RADIO INSTRUMENT FLIGHT

GPS APPROACH (RWOP 917.)

A Global Positioning System (GPS) approach is a non-precision instrument approach based on satellite transmitted positioning information received by on-board equipment and not dependent on ground-based navigation aids.

B. Procedures (full approach)

* Before reaching the IAF:

1. OBTAIN WEATHER, ALTIMETER, DUTY RUNWAY AND WINDS (WAR) OR ATIS/ASOS/AWOS.

2. NAVAIDS: LOAD APPROACH INTO ACTIVE FLIGHT PLAN:

A. SELECT AIRPORT IDENTIFIER (APT PAGE, TOP OF RIGHT
PAGE)
B. SELECT APPROACH

C. LOAD APPROACH (INTO FPL 0)
D. SELECT APPROPRIATE MODE and NAV SOURCE ON GPS PANEL
E. TUNE AND ID ANY AVAILABLE BACK-UP NAVAIDS

3. CHECK FOR OTHER "TRANSITION" POINTS (ie. STEP DOWN ALTITUDE FIXES) THAT ARE PUBLISHED ON THE APPROACH PLATE BUT NOT INCLUDED AS A WAYPOINT IN THE GPS APPROACH OBTAINED FROM THE DATABASE.

4. BRIEF APPROACH AND CO-PILOT DUTIES.

5. OBTAIN APPROACH CLEARANCE.
(*PRIOR TO IAF ENSURE APPROACH IS ARMED ON GPS PANEL)

*At the IAF:

1. TIME. NOTE TIME AT IAF.

2. TURN. TURN OUTBOUND ON PROCEDURE TURN OR TOWARDS NEXT WAYPOINT OF THE APPROACH AS APPROPRIATE.

3. TIME. N/R

4. TRANSITION. DECELERATE TO FINAL APPROACH SPEED OF 90 KIAS, DESCEND AS REQUIRED, COMPLETE LANDING CHECKLIST.

5. TWIST. SET DESIRED COURSE IN HSI/CDI AND ENSURE APPROPRIATE MODE (OBS/LEG) ON GPS PANEL. CHECK THAT GPS HAS SEQUENCED TO NEXT WPT.

6. TALK. MAKE VOICE REPORT AS REQUIRED.

7. EXECUTE APPROACH AS DEPICTED ON THE APPROACH PLATE, MAKE VOICE REPORTS AS DIRECTED, PROCEED TO MAP.

*At each waypoint:

1. TIME. N/R

2. TURN. TURN AS REQUIRED TO INTERCEPT SUBSEQUENT LEGS OF THE APPROACH.

3. TIME. N/R

4. TRANSITION. DESCEND TO NEXT INTERMEDIATE ALTITUDE OR MDA AS APPLICABLE. REVIEW LANDING CHECKLIST COMPLETE (GIVE CONSIDERATION TO LIGHTING CONFIGURATION INSIDE FAF.)

5. TWIST. SET DESIRED COURSE IN HSI/CDI, ENSURE LEG MODE (WHEN INBOUND TO FAF), CHECK THAT GPS HAS SEQUENCED TO NEXT WPT ON APPROACH.

6. TALK. MAKE VOICE REPORT AS REQUIRED/DIRECTED.

*If missed approach is required:

1. SET REQUIRED 70 KT CLIMB/100 KT CRUISE POWER.

2. SET REQUIRED 70 KT CLIMB/100 KT CRUISE NOSE ATTITUDE. (CHECK IVSI / ALTIMETER FOR POSITIVE CLIMB INDICATIONS).

3. TURN SEARCHLIGHT OFF.

4. TURN TO COMPLY WITH MISSED APPROACH OR CLIMBOUT INSTRUCTIONS. HAVE CO-PILOT MANUALLY SEQUENCE GPS (DIRECT-TO PBS) TO NEXT WPT REQUIRED FOR MISSED APPROACH.

5. TALK. REPORT MISSED APPROACH/EXECUTING CLIMBOUT INSTRUCTIONS, REASON FOR MISSED APPROACH(IF APPLICABLE) AND INTENTIONS AS SOON AS PRACTICABLE.

C. Amplification and technique

1. The approach to be executed must be entered into the active flight plan by selecting from the list of available approaches in the GPS Airport database (only 1 approach can be entered into the active FPL at a time).

2. CDI/HSI must be in the OBS mode for procedure turns, holding patterns and RVFAC until inbound on a portion of the approach when LEG mode should be selected (TWIST HSI/CDI to appropriate course and ensure GPS is in LEG mode)

3. If being radar vectored to final use the HSI/CDI in OBS mode until established on the approach course then switch to the LEG prior to arriving at the FAF.

4. During vectors to final it is imperative that the pilot stay oriented so that the next WPT that the aircraft will fly to on the approach is the active WPT after intercepting final.

5. If holding at a WPT remain in OBS mode. When cleared for the approach and inbound to the WPT, switch to LEG mode in order to enable the GPS unit to sequence through the waypoints that constitute the approach.

NOTE: If executing a procedure turn following holding remain in OBS until procedure turn inbound.

6. When switching from OBS to LEG mode and vice versa always ensure you are inbound to the desired WPT.

NOTE: Switching modes sometimes causes the KLN-900 to cycle to the next WPT in the approach sequence.

7. Prior to 2NM from FAF ensure GPS is in LEG mode. If GPS doesn't cycle to ACTIVE mode (ACTV) automatically, do not continue to MDA and contact ATC with intentions.

D. Common errors and safety notes

1. When being radar vectored to final HSI/CDI should remain in OBS mode. If LEG is selected the course from the aircraft to the active WPT will be locked into the HSI/CDI and may not be the FAC.

2. RAIM (receiver autonomous integrity monitoring) must be available to commence a GPS approach. A flashing Message indicator may be an indication of RAIM nonavailability.

3. Some published approaches that are parallel to ground based NAVAID-based approaches may contain transition points that do not have corresponding waypoints in the associated GPS approach. It is the responsibility of the pilot to identify these points and apply them to any GPS approach to be commenced by fixing their position relative to other waypoints that are contained within the GPS database. Note that DME will always count down to the active waypoint when inbound on approach.

4. The GPS unit will not automatically sequence to any waypoints required for a missed approach procedure. Automatic sequencing will cease at the MAP. If a missed approach is required, the pilot must manually sequence the unit to the missed approach WPT (Simply press the "direct to" key followed by the "enter" key, the default WPT will be the missed approach WPT following an approach that terminates at the MAP).

5. Not switching from OBS to LEG prior to FAF.

6. Not ensuring approach is armed within 30 NM of airfield.

7. Not checking that approach is ACTIVE at FAF.

8. Mistaking CDI/HSI scale change (Enroute to ARM to ACTV) for actual deviations and subsequently making unneeded or unnecessarily large corrections.

B. Localizer procedures

C. ILS procedures

D. Glideslope failure

5. If a glideslope indicator disappears on the CDI/HSI during the approach, descend no lower than published localizer minima, or if not published, no lower than circling minima for your category aircraft. If course deviation bar is fully deflected when inside of final approach fix and runway is not in sight, execute missed approach.


F. Precision minima

Approach Criteria for Single-Piloted Aircraft (OPNAV 3710.7R 5.3.4.3)
An instrument approach shall not be commenced if the reported weather is below published minimums for the type approach being conducted. …. Absolute minimums for a single-piloted aircraft executing a precision approach are 200-foot ceiling/height above touchdown (HAT) and visibility 1/2-statute-mile / 2,400 feet RVR or published minimums, whichever is higher.

1. The lowest authorized ILS minimums, with all required ground and airborne systems components operative, are

(a) Category I Decision Height (DH) 200 feet and Runway Visual Range (RVR) 2,400 feet (with touchdown zone and centerline lighting, RVR 1800 feet).


G. CAT II ILS

Why Brief this? Well, I would guess that it is to show us that we cannot shoot CAT II ILS approaches because we don’t have either the installed equipment or the authorization. If you happen to know update this gouge.

CATEGORY II OPERATIONS EQUIPMENT

The instruments and equipment listed in this section must be installed in each aircraft operated in a Category II operation. This section does not require duplication of instruments and equipment required by §91.205 or any other provisions of this chapter.

(a) Group I.

(1) Two localizer and glide slope receiving systems. Each system must provide a basic ILS display and each side of the instrument panel must have a basic ILS display. However, a single localizer antenna and a single glide slope antenna may be used.

(2) A communications system that does not affect the operation of at least one of the ILS systems.

(3) A marker beacon receiver that provides distinctive aural and visual indications of the outer and the middle markers.

(4) Two gyroscopic pitch and bank indicating systems.

(5) Two gyroscopic direction indicating systems.

(6) Two airspeed indicators.

(7) Two sensitive altimeters adjustable for barometric pressure, each having a placarded correction for altimeter scale error and for the wheel height of the aircraft. After June 26, 1979, two sensitive altimeters adjustable for barometric pressure, having markings at 20-foot intervals and each having a placarded correction for altimeter scale error and for the wheel height of the aircraft.

(8) Two vertical speed indicators.

(9) A flight control guidance system that consists of either an automatic approach coupler or a flight director system. A flight director system must display computed information as steering command in relation to an ILS localizer and, on the same instrument, either computed information as pitch command in relation to an ILS glide slope or basic ILS glide slope information. An automatic approach coupler must provide at least automatic steering in relation to an ILS localizer. The flight control guidance system may be operated from one of the receiving systems required by subparagraph (1) of this paragraph.

(10) For Category II operations with decision heights below 150 feet either a marker beacon receiver providing aural and visual indications of the inner marker or a radio altimeter.


Required Equipment for Night Flight (NATOPS 4.21)

1. All Exterior lights
2. All Instrument and Circuit Breaker panel lights
3. Operating Communications Radio
4. Attitude Gyro
5. Radar Altimeter

Night and Instrument Flights (NATOPS 5.5.3)
A flashlight shall be carried in the aircraft.

Introduce
A. GPS approach (min 2)
B. Localizer approach (min 1)
C. ILS approach (min 2)
Practice
A. Instrument takeoff (ITO)
B. Standard instrument departure (SID)
C. ASR
D. Enroute navigation/fuel consumption checks


A. ILS OPERATION
INSTRUMENT LANDING SYSTEM (ILS)

a. General

1. The ILS is designed to provide an approach path for exact alignment and descent of an aircraft on final approach to a runway.

2. The ground equipment consists of two highly directional transmitting systems and, along the approach, three (or fewer) marker beacons. The directional transmitters are known as the localizer and glide slope transmitters.

3. The system may be divided functionally into three parts:

(a) Guidance information localizer, glide slope

(b) Range information marker beacon, DME

(c) Visual information approach lights, touchdown and centerline lights, runway lights

4. Compass locators located at the Outer Marker (OM) or Middle Marker (MM) may be substituted for marker beacons. DME, when specified in the procedure, may be substituted for the OM.

5. Where a complete ILS system is installed on each end of a runway; (i.e., the approach end of Runway 4 and the approach end of Runway 22) the ILS systems are not in service simultaneously.

b. Localizer

1. The localizer transmitter operates on one of 40 ILS channels within the frequency range of 108.10 to 111.95 MHz. Signals provide the pilot with course guidance to the runway centerline.

2. The approach course of the localizer is called the front course and is used with other functional parts, e.g., glide slope, marker beacons, etc. The localizer signal is transmitted at the far end of the runway. It is adjusted for a course width (full scale fly-left to a full scale fly-right) of 700 feet at the runway threshold.

3. The course line along the extended centerline of a runway, in the opposite direction to the front course is called the back course.

CAUTION: Unless the aircraft's ILS equipment includes reverse sensing capability, when flying inbound on the back course it is necessary to steer the aircraft in the direction opposite the needle deflection when making corrections from off-course to on-course. This "flying away from the needle" is also required when flying outbound on the front course of the localizer. DO NOT USE BACK COURSE SIGNALS for approach unless a BACK COURSE APPROACH PROCEDURE is published for that particular runway and the approach is authorized by ATC.

4. Identification is in International Morse Code and consists of a three-letter identifier preceded by the letter I (··) transmitted on the localizer frequency.

5. The localizer provides course guidance throughout the descent path to the runway threshold from a distance of 18 NM from the antenna between an altitude of 1,000 feet above the highest terrain along the course line and 4,500 feet above the elevation of the antenna site. Proper off-course indications are provided throughout the following angular areas of the operational service volume:

(a) To 10 degrees either side of the course along a radius of 18 NM from the antenna, and

(b) From 10 to 35 degrees either side of the course along a radius of 10 NM.
6. Unreliable signals may be received outside these areas.

c. Localizer-type Directional Aid

1. The Localizer-type Directional Aid (LDA) is of comparable use and accuracy to a localizer but is not part of a complete ILS. The LDA course usually provides a more precise approach course than the similar Simplified Directional Facility (SDF) installation, which may have a course width of 6 or 12 degrees.

2. The LDA is not aligned with the runway. Straight-in minimums may be published where alignment does not exceed 30 degrees between the course and runway. Circling minimums only are published where this alignment exceeds 30 degrees.

d. Glide Slope/Glide Path

1. The UHF glide slope transmitter, operating on one of the 40 ILS channels within the frequency range 329.15 MHz, to 335.00 MHz radiates its signals in the direction of the localizer front course. The term "glide path" means that portion of the glide slope that intersects the localizer.

CAUTION: False glide slope signals may exist in the area of the localizer back course approach which can cause the glide slope flag alarm to disappear and present unreliable glide slope information. Disregard all glide slope signal indications when making a localizer back course approach unless a glide slope is specified on the approach and landing chart.

2. The glide slope transmitter is located between 750 feet and 1,250 feet from the approach end of the runway (down the runway) and offset 250 to 650 feet from the runway centerline. It transmits a glide path beam 1.4 degrees wide (vertically). The signal provides descent information for navigation down to the lowest authorized decision height (DH) specified in the approved ILS approach procedure. The glide path may not be suitable for navigation below the lowest authorized DH and any reference to glide path indications below that height must be supplemented by visual reference to the runway environment. Glide paths with no published DH are usable to runway threshold.

3. The glide path projection angle is normally adjusted to 3 degrees above horizontal so that it intersects the MM at about 200 feet and the OM at about 1,400 feet above the runway elevation. The glide slope is normally usable to the distance of 10 NM. However, at some locations, the glide slope has been certified for an extended service volume which exceeds 10 NM.

4. Pilots must be alert when approaching the glide path interception. False courses and reverse sensing will occur at angles considerably greater than the published path.

5. Make every effort to remain on the indicated glide path.

CAUTION: Avoid flying below the glide path to assure obstacle/terrain clearance is maintained.

6. The published glide slope threshold crossing height (TCH) DOES NOT represent the height of the actual glide path on course indication above the runway threshold. It is used as a reference for planning purposes which represents the height above the runway threshold that an aircraft's glide slope antenna should be, if that aircraft remains on a trajectory formed by the four-mile-to-middle marker glide path segment.

7. Pilots must be aware of the vertical height between the aircraft's glide slope antenna and the main gear in the landing configuration and, at the DH, plan to adjust the descent angle accordingly if the published TCH indicates the wheel crossing height over the runway threshold may not be satisfactory. Tests indicate a comfortable wheel crossing height is approximately 20 to 30 feet, depending on the type of aircraft.

e. Distance Measuring Equipment (DME)

1. When installed with the ILS and specified in the approach procedure, DME may be used:
(a) In lieu of the OM.

(b) As a back course (BC) final approach fix (FAF).

(c) To establish other fixes on the localizer course.

2. In some cases, DME from a separate facility may be used within Terminal Instrument Procedures (TERPS) limitations:

(a) To provide ARC initial approach segments.

(b) As a FAF for BC approaches.

(c) As a substitute for the OM.

f. Marker Beacon

1. ILS marker beacons have a rated power output of 3 watts or less and an antenna array designed to produce an elliptical pattern with dimensions, at 1,000 feet above the antenna, of approximately 2,400 feet in width and 4,200 feet in length. Airborne marker beacon receivers with a selective sensitivity feature should always be operated in the "low" sensitivity position for proper reception of ILS marker beacons.

2. Ordinarily, there are two marker beacons associated with an ILS, the OM and MM. Locations with a Category II ILS also have an inner marker (IM). When an aircraft passes over a marker, the pilot will receive the following indications:

MARKER PASSAGE INDICATOR

MARKER CODE LIGHT

OM - - - BLUE

MM ·-·- AMBER

IM ···· WHITE

BC ·· ·· WHITE

(a) The OM normally indicates a position at which an aircraft at the appropriate altitude on the localizer course will intercept the ILS glide path.

(b) The MM indicates a position approximately 3,500 feet from the landing threshold. This is also the position where an aircraft on the glide path will be at an altitude of approximately 200 feet above the elevation of the touchdown zone.

(c) The inner marker (IM) will indicate a point at which an aircraft is at a designated decision height (DH) on the glide path between the MM and landing threshold.

3. A back course marker normally indicates the ILS back course final approach fix where approach descent is commenced.

g. Compass Locator

1. Compass locator transmitters are often situated at the MM and OM sites. The transmitters have a power of less than 25 watts, a range of at least 15 miles and operate between 190 and 535 kHz. At some locations, higher powered radio beacons, up to 400 watts, are used as OM compass locators. These generally carry Transcribed Weather Broadcast (TWEB) information.

2. Compass locators transmit two letter identification groups. The outer locator transmits the first two letters of the localizer identification group, and the middle locator transmits the last two letters of the localizer identification group.

h. ILS Frequency


FREQUENCY PAIRS ALLOCATED FOR ILS

i. ILS Minimums

1. The lowest authorized ILS minimums, with all required ground and airborne systems components operative, are

(a) Category I Decision Height (DH) 200 feet and Runway Visual Range (RVR) 2,400 feet (with touchdown zone and centerline lighting, RVR 1800 feet).

(b) Category II DH 100 feet and RVR 1,200 feet.

(c) Category IIIa No DH or DH below 100 feet and RVR not less than 700 feet.

(d) Category IIIb No DH or DH below 50 feet and RVR less than 700 feet but not less than 150 feet.

(e) Category IIIc No DH and no RVR limitation.

NOTE: Special authorization and equipment are required for Category II and III

B. GPS OPERTION
GLOBAL POSITIONING SYSTEM (GPS) (AIM 1-1-21.)

a. System Overview

1. The GPS is a United States satellite-based radio navigational, positioning, and time transfer system operated by the Department of Defense (DoD). The system provides highly accurate position and velocity information and precise time on a continuous global basis to an unlimited number of properly equipped users. The system is unaffected by weather and provides a worldwide common grid reference system based on the earth-fixed coordinate system. For its earth model, GPS uses the World Geodetic System of 1984 (WGS-84) datum.

2. GPS provides two levels of service: Standard Positioning Service (SPS) and Precise Positioning Service (PPS). SPS provides, to all users, horizontal positioning accuracy of 100 meters, or less, with a probability of 95 percent and 300 meters with a probability of 99.99 percent. PPS is more accurate than SPS; however, this is limited to authorized U.S. and allied military, federal government, and civil users who can satisfy specific U.S. requirements.

3. GPS operation is based on the concept of ranging and triangulation from a group of satellites in space which act as precise reference points. A GPS receiver measures distance from a satellite using the travel time of a radio signal. Each satellite transmits a specific code, called a course/acquisition (CA) code, which contains information on the satellite's position, the GPS system time, and the health and accuracy of the transmitted data. Knowing the speed at which the signal traveled (approximately 186,000 miles per second) and the exact broadcast time, the distance traveled by the signal can be computed from the arrival time.

4. The GPS receiver matches each satellite's CA code with an identical copy of the code contained in the receiver's database. By shifting its copy of the satellite's code in a matching process, and by comparing this shift with its internal clock, the receiver can calculate how long it took the signal to travel from the satellite to the receiver. The distance derived from this method of computing distance is called a pseudo-range because it is not a direct measurement of distance, but a measurement based on time. Pseudo-range is subject to several error sources; for example, ionospheric and tropospheric delays, and multipath.

5. In addition to knowing the distance to a satellite, a receiver needs to know the satellite's exact position in space; this is known as its ephemeris. Each satellites signal transmits ephemeris information about its exact orbital location. The GPS receiver uses this information to precisely establish the position of the satellite.

6. Using the calculated pseudo-range and position information supplied by the satellite, the GPS receiver mathematically determines its position by triangulation. The GPS receiver needs at least four satellites to yield a three-dimensional position (latitude, longitude, and altitude) and time solution. The GPS receiver computes navigational values such as distance and bearing to a waypoint, ground speed, etc., by using the aircraft's known latitude/longitude and referencing these to a database built into the receiver.

7. The GPS constellation of 24 satellites is designed so that a minimum of five are always observable by a user anywhere on earth. The receiver uses data from a minimum of four satellites above the mask angle (the lowest angle above the horizon at which it can use a satellite).

8. The GPS receiver verifies the integrity (usability) of the signals received from the GPS constellation through receiver autonomous integrity monitoring (RAIM) to determine if a satellite is providing corrupted information. At least one satellite, in addition to those required for navigation, must be in view for the receiver to perform the RAIM function; thus, RAIM needs a minimum of 5 satellites in view, or 4 satellites and a barometric altimeter (baro-aiding) to detect an integrity anomaly. For receivers capable of doing so, RAIM needs 6 satellites in view (or 5 satellites with baro-aiding) to isolate the corrupt satellite signal and remove it from the navigation solution. Baro-aiding is a method of augmenting the GPS integrity solution by using a nonsatellite input source. GPS derived altitude should not be relied upon to determine aircraft altitude since the vertical error can be quite large. To ensure that baro-aiding is available, the current altimeter setting must be entered into the receiver as described in the operating manual.

9. RAIM messages vary somewhat between receivers; however, generally there are two types. One type indicates that there are not enough satellites available to provide RAIM integrity monitoring and another type indicates that the RAIM integrity monitor has detected a potential error that exceeds the limit for the current phase of flight. Without RAIM capability, the pilot has no assurance of the accuracy of the GPS position.

10. The Department of Defense declared initial operational capability (IOC) of the U.S. GPS on December 8, 1993. The Federal Aviation Administration (FAA) has granted approval for U.S. civil operators to use properly certified GPS equipment as a primary means of navigation in oceanic airspace and certain remote areas. Properly certified GPS equipment may be used as a supplemental means of IFR navigation for domestic enroute, terminal operations, and certain instrument approach procedures (IAPs). This approval permits the use of GPS in a manner that is consistent with current navigation requirements as well as approved air carrier operations specifications..................Sky wings

NAVIGATION

3-11 CLASS A AIRSPACE

Definition: Generally, that airspace from 18,000 feet MSL up to and including FL600, including the airspace overlying the waters within 12 nautical miles of the coast of the 48 contiguous States and Alaska; and designated international airspace beyond 12 nautical miles of the coast of the 48 contiguous States and Alaska within areas of domestic radio navigational signal or ATC radar coverage, and within which domestic procedures are applied.

3-12 CLASS B AIRSPACE

Definition: Generally, that airspace from the surface to 10,000 feet MSL surrounding the nation's busiest airports in terms of IFR operations or passenger enplanements. The configuration of each Class B airspace area is individually tailored and consists of a surface area and two or more layers (some Class B airspace areas resemble upside-down wedding cakes), and is designed to contain all published instrument procedures once an aircraft enters the airspace. An ATC clearance is required for all aircraft to operate in the area, and all aircraft that are so cleared receive separation services within the airspace. The cloud clearance requirement for VFR operations is ``clear of clouds.'' b. Operating Rules and Pilot/Equipment Requirements for VFR Operations: Regardless of weather conditions, an ATC clearance is required prior to operating within Class B airspace. Pilots should not request a clearance to operate within Class B airspace unless the requirements of FAR Part 91.215 and Part 91.131 are met. Included among these requirements are:

1. Unless otherwise authorized by ATC, aircraft must be equipped with an operable two-way radio capable of communicating with ATC on appropriate frequencies for that Class B airspace.

2. No person may take off or land a civil aircraft at an airport within Class B airspace or operate a civil aircraft within Class B airspace unless: (a) The pilot in command holds at least a private pilot certificate; or, (b) The aircraft is operated by a student pilot or recreational pilot who seeks private pilot certification and has met the requirements of FAR Part 61.95.

3. Unless otherwise authorized by ATC, each person operating a large turbine engine-powered airplane to or from a primary airport shall operate at or above the designated floors while within the lateral limits of Class B airspace.

4. Unless otherwise authorized by ATC, each aircraft must be equipped as follows: (a) For IFR operations, an operable VOR or TACAN receiver; and (b) For all operations, a two-way radio capable of communications with ATC on appropriate frequencies for that area; and (c) Unless otherwise authorized by ATC, an operable radar beacon transponder with automatic altitude reporting equipment.

3-13 CLASS C AIRSPACE

Generally, that airspace from the surface to 4,000 feet above the airport elevation (charted in MSL) surrounding those airports that have an operational control tower, are serviced by a radar approach control, and that have a certain number of IFR operations or passenger enplanements. Although the configuration of each Class C airspace area is individually tailored, the airspace usually consists of a 5 NM radius core surface area that extends from the surface up to 4,000 feet above the airport elevation, and a 10 NM radius shelf area that extends from 1,200 feet to 4,000 feet above the airport elevation. b. Outer Area: The normal radius will be 20NM, with some variations based on site specific requirements. The outer area extends outward from the primary airport and extends from the lower limits of radar/radio coverage up to the ceiling of the approach control's delegated airspace, excluding the Class C airspace and other airspace as appropriate.

Operating Rules and Pilot/Equipment Requirements:

1. Pilot Certification: No specific certification required.

2. Equipment: (a) Two-way radio, and (b) Unless otherwise authorized by ATC, an operable radar beacon transponder with automatic altitude reporting equipment.

3. Arrival or Through Flight Entry Requirements: Two-way radio communication must be established with the ATC facility providing ATC services prior to entry and thereafter maintain those communications while in Class C airspace. Pilots of arriving aircraft should contact the Class C airspace ATC facility on the publicized frequency and give their position, altitude, radar beacon code, destination, and request Class C service. Radio contact should be initiated far enough from the Class C airspace boundary to preclude entering Class C airspace before two-way radio communications are established

3-14 CLASS D AIRSPACE

Definition: Generally, that airspace from the surface to 2,500 feet above the airport elevation (charted in MSL) surrounding those airports that have an operational control tower. The configuration of each Class D airspace area is individually tailored and when instrument procedures are published, the airspace will normally be designed to contain the procedures.

Operating Rules and Pilot/Equipment Requirements:

1. Pilot Certification: No specific certification required.

2. Equipment: Unless otherwise authorized by ATC, an operable two-way radio is required.

3. Arrival or Through Flight Entry Requirements: Two-way radio communication must be established with the ATC facility providing ATC services prior to entry and thereafter maintain those communications while in the Class D airspace. Pilots of arriving aircraft should contact the control tower on the publicized frequency and give their position, altitude, destination, and any request(s). Radio contact should be initiated far enough from the Class D airspace boundary to preclude entering the Class D airspace before two-way radio communications are established.

4. Aircraft Speed: Unless otherwise authorized or required by ATC, no person may operate an aircraft at or below 2,500 feet above the surface within 4 nautical miles of the primary airport of a Class D airspace area at an indicated airspeed of more than 200 knots (230 mph).

5. Class D airspace areas are depicted on Sectional and Terminal charts with blue segmented lines, and on IFR En Route Lows with a boxed [D].

6. Arrival extensions for instrument approach procedures may be Class D or Class E airspace. As a general rule, if all extensions are 2 miles or less, they remain part of the Class D surface area. However, if any one extension is greater than 2 miles, then all extensions become Class E.

3-15 CLASS E AIRSPACE

Definition: Generally, if the airspace is not Class A, Class B, Class C, or Class D, and it is controlled airspace, it is Class E airspace.

Operating Rules and Pilot/Equipment Requirements:

1. Pilot Certification: No specific certification required.

2. Equipment: No specific equipment required by the airspace.

3. Arrival or Through Flight Entry Requirements: No specific requirements.

c. Charts: Class E airspace below 14,500 feet MSL is charted on Sectional, Terminal, World, and IFR En Route Low Altitude charts.

d. Vertical limits: Except for 18,000 feet MSL, Class E airspace has no defined vertical limit but rather it extends upward from either the surface or a designated altitude to the overlying or adjacent controlled airspace.

e. Types of Class E Airspace:

Surface area designated for an airport: When designated as a surface area for an airport, the airspace will be configured to contain all instrument procedures.

Extension to a surface area: There are Class E airspace areas that serve as extensions to Class B, Class C, and Class D surface areas designated for an airport. Such airspace provides controlled airspace to contain standard instrument approach procedures without imposing a communications requirement on pilots operating under VFR.

Airspace used for transition: There are Class E airspace areas beginning at either 700 or 1,200 feet AGL used to transition to/from the terminal or en route environment.

4. Federal Airways: The Federal airways are Class E airspace areas and, unless otherwise specified, extend upward from 1,200 feet to, but not including, 18,000 feet MSL.

3-22. IFR REQUIREMENTS

The FARs specify the pilot and aircraft equipment requirements for IFR flight. Pilots are reminded that in addition to altitude or flight level requirements, FAR Part 91.177 includes a requirement to remain at least 1,000 feet (2,000 feet in designated mountainous terrain) above the highest obstacle within a horizontal distance of 4 nautical miles from the course to be flown.

3-31. PROHIBITED AREA

Prohibited Areas contain airspace of defined dimensions identified by an area on the surface of the earth within which the flight of aircraft is prohibited. Such areas are established for security or other reasons associated with the national welfare. These areas are published in the Federal Register and are depicted on aeronautical charts.

3-32. RESTRICTED AREA

Restricted Areas contain airspace identified by an area on the surface of the earth within which the flight of aircraft, while not wholly prohibited, is subject to restrictions. Activities within these areas must be confined because of their nature or limitations imposed upon aircraft operations that are not a part of those activities or both. Restricted areas denote the existence of unusual, often invisible, hazards to aircraft such as artillery firing, aerial gunnery, or guided missiles. Penetration of Restricted Areas without authorization from the using or controlling agency may be extremely hazardous to the aircraft and its occupants. Restricted Areas are published in the Federal Register and constitute FAR Part 73.

ATC facilities apply the following procedures when aircraft are operating on an IFR clearance (including those cleared by ATC to maintain VFR-ON-TOP) via a route which lies within joint-use restricted airspace.

1. If the restricted area is not active and has been released to the controlling agency (FAA), the ATC facility will allow the aircraft to operate in the restricted airspace without issuing specific clearance for it to do so.

2. If the restricted area is active and has not been released to the controlling agency (FAA), the ATC facility will issue a clearance which will ensure the aircraft avoids the restricted airspace unless it is on an approved altitude reservation mission or has obtained its own permission to operate in the airspace and so informs the controlling facility

33-33. WARNING AREA

Warning Areas are airspace which may contain hazards to nonparticipating aircraft in international airspace. Warning Areas are established beyond the 3 mile limit. Though the activities conducted within Warning Areas may be as hazardous as those in Restricted Areas, Warning Areas cannot be legally designated as Restricted Areas because they are over international waters. Penetration of Warning Areas during periods of activity may be hazardous to the aircraft and its occupants. Official descriptions of Warning Areas may be obtained on request to the FAA, Washington, D.C.

3-34. MILITARY OPERATIONS AREAS (MOA)

MOAs consist of airspace of defined vertical and lateral limits established for the purpose of separating certain military training activities from IFR traffic. Whenever a MOA is being used, nonparticipating IFR traffic may be cleared through a MOA if IFR separation can be provided by ATC. Otherwise, ATC will reroute or restrict nonparticipating IFR traffic.

Most training activities necessitate acrobatic or abrupt flight maneuvers. Military pilots conducting flight in Department of Defense aircraft within a designated and active military operations area (MOA) are exempted from the provisions of FAR Part 91.303(c) and (d) which prohibit acrobatic flight within Federal airways and Class B, Class C, Class D, and Class E surface areas.

Pilots operating under VFR should exercise extreme caution while flying within a MOA when military activity is being conducted. The activity status (active/inactive) of MOA's may change frequently. Therefore, pilots should contact any FSS within 100 miles of the area to obtain accurate real-time information concerning the MOA hours of operation. Prior to entering an active MOA, pilots should contact the controlling agency for traffic advisories.

3-35. ALERT AREA

Alert Areas are depicted on aeronautical charts to inform nonparticipating pilots of areas that may contain a high volume of pilot training or an unusual type of aerial activity. Pilots should be particularly alert when flying in these areas. All activity within an Alert Area shall be conducted in accordance with FARs, without waiver, and pilots of participating aircraft as well as pilots transiting the area shall be equally responsible for collision avoidance. Information concerning these areas may be obtained upon request to the FAA, Washington, D.C.

3-36. CONTROLLED FIRING AREAS

Controlled Firing Areas contain activities which, if not conducted in a controlled environment, could be hazardous to nonparticipating aircraft. The distinguishing feature of the Controlled Firing Area, as compared to other special use airspace, is that its activities are suspended immediately when spotter aircraft, radar, or ground lookout positions indicate an aircraft might be approaching the area. There is no need to chart Controlled Firing Areas since they do not cause a nonparticipating aircraft to change its flight path.

4-13. AUTOMATIC TERMINAL INFORMATION SERVICE (ATIS)

ATIS is the continuous broadcast of recorded noncontrol information in selected high activity terminal areas. Its purpose is to improve controller effectiveness and to relieve frequency congestion by automating the repetitive transmission of essential but routine information.

ATIS information includes the time of the latest weather sequence, ceiling, visibility, obstructions to visibility, temperature, dew point (if available), wind direction (magnetic), and velocity, altimeter, other pertinent remarks, instrument approach and runway in use.

4-19. TRANSPONDER OPERATION

Air Traffic Control Radar Beacon System (ATCRBS) is similar to and compatible with military coded radar beacon equipment. Civil MODE A is identical to military MODE 3.

Civil and military transponders should be adjusted to the ``on'' or normal operating position as late as practicable prior to takeoff and to ``off'' or ``standby'' as soon as practicable after completing landing roll, unless the change to ``standby'' has been accomplished previously at the request of ATC.

Some transponders are equipped with a MODE C automatic altitude reporting capability. This system converts aircraft altitude in 100 foot increments to coded digital information which is transmitted together with MODE C framing pulses to the interrogating radar facility.

Pilots of aircraft with operating MODE C altitude reporting transponders should report exact altitude or Flight Level to the nearest hundred foot increment when establishing initial contact with an ATC facility.

TRANSPONDER IDENT FEATURE

1. The transponder shall be operated only as specified by ATC. Activate the ``IDENT'' feature only upon request of the ATC controller.

Military pilots operating VFR or IFR within restricted/warning areas should adjust their transponders to code 4000 unless another code has been assigned by ATC.

In general, the FAR requires aircraft to be equipped with Mode C transponders when operating:

(a) at or above 10,000 feet MSL over the 48 contiguous states or the District of Columbia, excluding that airspace below 2,500 feet AGL;

(b) within 30 miles of a Class B airspace primary airport, below 10,000 feet MSL. Balloons, gliders, and aircraft not equipped with an engine driven electrical system are excepted from the above requirements when operating below the floor of Class A airspace and/or; outside of a Class B airspace and below the ceiling of the Class B Airspace (or 10,000 feet MSL, whichever is lower);

(c) within and above all Class C airspace, up to 10,000 feet MSL;

(d) within 10 miles of certain designated airports, excluding that airspace which is both outside the Class D surface area and below 1,200 feet AGL. Balloons, gliders and aircraft not equipped with an engine driven electrical system are excepted from this requirement. 3. FAR Part 99.12 requires all aircraft flying into, within, or across the contiguous U.S. ADIZ be equipped with a Mode C or Mode S transponder. Balloons, gilders and aircraft not equipped with an engine driven electrical system are excepted from this requirement.

4-31. RADIO TECHNIQUE

Listen before you transmit. Many times you can get the information you want through ATIS or by monitoring the frequency.

Think before keying your transmitter. Know what you want to say and if it is lengthy; e.g., a flight plan or IFR position report, jot it down.

4-32. CONTACT PROCEDURES

Initial Contact-- 1. The terms initial contact or initial callup means the first radio call you make to a given facility or the first call to a different controller or FSS specialist within a facility. Use the following format:

(a) Name of the facility being called;

(b) Your full aircraft identification as filed in the flight plan or as discussed under Aircraft Call Signs below;

(c) The type of message to follow or your request if it is short, and

(d) The word ``Over'' if required.

(e) EXAMPLE: ``NEW YORK RADIO, MOONEY THREE ONE ONE ECHO.'' EXAMPLE: ``COLUMBIA GROUND, CESSNA THREE ONE SIX ZERO FOXTROT, I-F-R MEMPHIS.'' EXAMPLE: ``MIAMI CENTER, BARON FIVE SIX THREE HOTEL, REQUEST V-F-R TRAFFIC ADVISORIES.''

4-42. COMMUNICATIONS WITH TOWER WHEN AIRCRAFT TRANSMITTER OR RECEIVER OR BOTH ARE INOPERATIVE

Arriving Aircraft.

1. Receiver inoperative-If you have reason to believe your receiver is inoperative, remain outside or above the Class D surface area until the direction and flow of traffic has been determined; then, advise the tower of your type aircraft, position, altitude, intention to land, and request that you be controlled with light signals.When you are approximately 3 to 5 miles from the airport, advise the tower of your position and join the airport traffic pattern. From this point on, watch the tower for light signals. Thereafter, if a complete pattern is made, transmit your position downwind and/or turning base leg.

2. Transmitter inoperative--Remain outside or above the Class D surface area until the direction and flow of traffic has been determined; then, join the airport traffic pattern. Monitor the primary local control frequency as depicted on Sectional Charts for landing or traffic information, and look for a light signal which may be addressed to your aircraft. During hours of daylight, acknowledge tower transmissions or light signals by rocking your wings. At night, acknowledge by blinking the landing or navigation lights. To acknowledge tower transmissions during daylight hours, hovering helicopters will turn in the direction of the controlling facility and flash the landing light. While in flight, helicopters should show their acknowledgement of receiving a transmission by making shallow banks in opposite directions. At night, helicopters will acknowledge receipt of transmissions by flashing either the landing or the search light.

3. Transmitter and receiver inoperative--Remain outside or above the Class D surface area until the direction and flow of traffic has been determined; then, join the airport traffic pattern and maintain visual contact with the tower to receive light signals. Acknowledge light signals as noted above.

4-71. OPTION APPROACH

The ``Cleared for the Option'' procedure will permit an instructor, flight examiner or pilot the option to make a touch-and-go, low approach, missed approach, stop-and-go, or full stop landing.

4-72. USE OF AIRCRAFT LIGHTS

Aircraft position and anticollision lights are required to be lighted on aircraft operated from sunset to sunrise. Anticollision lights, however, need not be lighted when the pilot-in-command determines that, because of operating conditions, it would be in the interest of safety to turn off the lights (FAR Part 91.209). For example, strobe lights should be turned off on the ground when they adversely affect ground personnel or other pilots, and in flight when there are adverse reflection from clouds.

4-80. CLEARANCE

``The pilot-in-command of an aircraft is directly responsible for, and is the final authority as to, the operation of that aircraft.'' If ATC issues a clearance that would cause a pilot to deviate from a rule or regulation, or in the pilot's opinion, would place the aircraft in jeopardy, IT IS THE PILOT'S RESPONSIBILITY TO REQUEST AN AMENDED CLEARANCE.

When weather conditions permit, during the time an IFR flight is operating, it is the direct responsibility of the pilot to avoid other aircraft since VFR flights may be operating in the same area without the knowledge of ATC. Traffic clearances provide standard separation only between IFR flights.

4-82. CLEARANCE ITEMS

ATC clearances normally contain the following:

a. Clearance Limit.--The traffic clearance issued prior to departure will normally authorize flight to the airport of intended landing. Under certain conditions, at some locations a short-range clearance procedure is utilized whereby a clearance is issued to a fix within or just outside of the terminal area and the pilot is advised of the frequency on which he will receive the long-range clearance direct from the center controller.

b. Altitude Data-- 1. The altitude or flight level instructions in an ATC clearance normally require that a pilot ``MAINTAIN'' the altitude or flight level at which the flight will operate when in controlled airspace. Altitude or flight level changes while en route should be requested prior to the time the change is desired.

c. The term ``cruise'' may be used instead of ``MAINTAIN'' to assign a block of airspace to a pilot from the minimum IFR altitude up to and including the altitude specified in the cruise clearance. The pilot may level off at any intermediate altitude within this block of airspace. Climb/descent within the block is to be made at the discretion of the pilot. However, once the pilot starts descent and verbally reports leaving an altitude in the block, he may not return to that altitude without additional ATC clearance.


1. Whenever an aircraft has been cleared to a fix other than the destination airport and delay is expected, it is the responsibility of the ATC controller to issue complete holding instructions (unless the pattern is charted), an EFC time, and his best estimate of any additional en route/terminal delay.

2. If the holding pattern is charted and the controller doesn't issue complete holding instructions, the pilot is expected to hold as depicted on the appropriate chart. When the pattern is charted, the controller may omit all holding instructions except the charted holding direction and the statement AS PUBLISHED, e.g., ``HOLD EAST AS PUBLISHED.'' Controllers shall always issue complete holding instructions when pilots request them.

3. If no holding pattern is charted and holding instructions have not been issued, the pilot should ask ATC for holding instructions prior to reaching the fix. This procedure will eliminate the possibility of an aircraft entering a holding pattern other than that desired by ATC. If the pilot is unable to obtain holding instructions prior to reaching the fix (due to frequency congestion, stuck microphone, etc.), he should hold in a standard pattern on the course on which he approached the fix and request further clearance as soon as possible. In this event, the altitude/flight level of the aircraft at the clearance limit will be protected so that separation will be provided as required.

4. When an aircraft is 3 minutes or less from a clearance limit and a clearance beyond the fix has not been received, the pilot is expected to start a speed reduction so that he will cross the fix, initially, at or below the maximum holding airspeed.

5. When no delay is expected, the controller should issue a clearance beyond the fix as soon as possible and, whenever possible, at least 5 minutes before the aircraft reaches the clearance limit.

6. Pilots should report to ATC the time and altitude/flight level at which the aircraft reaches the clearance limit and report leaving the clearance limit.

4-83. AMENDED CLEARANCES

Amendments to the initial clearance will be issued at any time an air traffic controller deems such action necessary to avoid possible confliction between aircraft. Clearances will require that a flight ``hold'' or change altitude prior to reaching the point where standard separation from other IFR traffic would no longer exist.

4-85. PILOT RESPONSIBILITY UPON CLEARANCE ISSUANCE

a. Record ATC clearance--When conducting an IFR operation, make a written record of your clearance.

b. ATC Clearance/Instruction Readback--Pilots of airborne aircraft should read back those parts of ATC clearances and instructions containing altitude assignments or vectors as a means of mutual verification. The readback of the ``numbers'' serves as a double check between pilots and controllers and reduces the kinds of communications errors that occur when a number is either ``misheard'' or is incorrect.

5-7. FLIGHT PLAN--IFR FLIGHTS

General-- 1. Prior to departure from within, or prior to entering controlled airspace, a pilot must submit a complete flight plan and receive an air traffic clearance, if weather conditions are below VFR minimums. Instrument flight plans may be submitted to the nearest FSS or ATCT either in person or by telephone (or by radio if no other means are available). Pilots should file IFR flight plans at least 30 minutes prior to estimated time of departure to preclude possible delay in receiving a departure clearance from ATC. To minimize your delay in entering Class B, Class C, Class D and Class E surface area at destination when IFR weather conditions exist or are forecast at that airport, an IFR flight plan should be filed before departure. Otherwise, a 30 minute delay is not unusual in receiving an ATC clearance because of time spent in processing flight plan data. Traffic saturation frequently prevents control personnel from accepting flight plans by radio. In such cases, the pilot is advised to contact the nearest FSS for the purpose of filing the flight plan.

Direct Flights-- 1. All or any portions of the route which will not be flown on the radials or courses of established airways or routes, such as direct route flights, must be defined by indicating the radio fixes over which the flight will pass. Fixes selected to define the route shall be those over which the position of the aircraft can be accurately determined. Such fixes automatically become compulsory reporting points for the flight, unless advised otherwise by ATC.

5-31. POSITION REPORTING

Position Identification—

1. When a position report is to be made passing a VOR radio facility, the time reported should be the time at which the first complete reversal of the ``to/from'' indicator is accomplished.

2. When a position report is made passing a facility by means of an airborne ADF, the time reported should be the time at which the indicator makes a complete reversal.

Position Reporting Requirements—

1. Flights along airways or routes--A position report is required by all flights regardless of altitude, including those operating in accordance with an ATC clearance specifying ``VFR ON TOP,'' over each designated compulsory reporting point along the route being flown.

2. Flight Along a Direct Route--Regardless of the altitude or flight level being flown, including flights operating in accordance with an ATC clearance specifying ``VFR ON TOP'', pilots shall report over each reporting point used in the flight plan to define the route of flight.

3. Flights in a Radar Environment--When informed by ATC that their aircraft are in ``Radar Contact,'' pilots should discontinue position reports over designated reporting points. They should resume normal position reporting when ATC advises ``RADAR CONTACT LOST'' or ``RADAR SERVICE TERMINATED.''

Position Report Items—

1. Position reports should include the following items:

(a) Identification.

(b) Position.

(c) Time.

(d) Altitude or flight level (include actual altitude or flight level when operating on a clearance specifying VFR-ON-TOP.)

(e) Type of flight plan (not required in IFR position reports made directly to ARTCC's or approach control),

(f) ETA and name of next reporting point.

(g) The name only of the next succeeding reporting point along the route of flight, and

(h) Pertinent remarks.

5-32. ADDITIONAL REPORTS

The following reports should be made to ATC or FSS facilities without a specific ATC request:

1. At all times:

(a) When vacating any previously assigned altitude or flight level for a newly assigned altitude or flight level.

(b) When an altitude change will be made if operating on a clearance specifying VFR ON TOP.

(c) When unable to climb/descend at a rate of a least 500 feet per minute.

(d) When approach has been missed. (Request clearance for specific action; i.e., to alternative airport, another approach, etc.)

(e) Change in the average true airspeed (at cruising altitude) when it varies by 5 percent or 10 knots (whichever is greater) from that filed in the flight plan.

(f) The time and altitude or flight level upon reaching a holding fix or point to which cleared.

(g) When leaving any assigned holding fix or point.

NOTE--The reports in subparagraphs (f) and (g) may be omitted by pilots of aircraft involved in instrument training at military terminal area facilities when radar service is being provided.

(i) Any loss, in controlled airspace, of VOR, TACAN, ADF, low frequency navigation receiver capability, complete or partial loss of ILS receiver capability or impairment of air/ground communications capability. Reports should include aircraft identification, equipment affected, degree to which the capability to operate under IFR in the ATC system is impaired, and the nature and extent of assistance desired from ATC.

(j) Any information relating to the safety of flight.

2. When not in radar contact:

(a) When leaving final approach fix inbound on final approach (non precision approach) or when leaving the outer marker or fix used in lieu of the outer marker inbound on final approach (precision approach).

(b) A corrected estimate at anytime it becomes apparent that an estimate as previously submitted is in error in excess of 3 minutes. Pilots encountering weather conditions which have not been forecast, or hazardous conditions which have been forecast, are expected to forward a report of such weather to ATC. (Reference--Pilot Weather Reports (PIREPs), paragraph 7-19 and FAR Part 91.183(b) and (c).)

5-35. CHANGEOVER POINTS (COP'S)

a. COP's are prescribed for Federal Airways, jet routes, Area Navigation routes, or other direct routes for which an MEA is designated under FAR Part 95. The COP is a point along the route or airway segment between two adjacent navigation facilities or way points where changeover in navigation guidance should occur. At this point, the pilot should change navigation receiver frequency from the station behind the aircraft to the station ahead.

b. The COP is located midway between the navigation facilities for straight route segments, or at the intersection of radials or courses forming a dogleg in the case of dogleg route segments. When the COP is NOT located at the midway point, aeronautical charts will depict the COP location and give the mileage to the radio aids.

5-36. HOLDING

Entry Procedures

(a) Parallel Procedure: When approaching the holding fix from anywhere in sector (a), the parallel entry procedure would be to turn to a heading to parallel the holding course outbound on the non-holding side for one minute, turn in the direction of the holding pattern thru more than 180 degrees, and return to the holding fix or intercept the holding course inbound.

(b) Teardrop Procedure: When approaching the holding fix from anywhere in sector (b), the teardrop entry procedure would be to fly to the fix, turn outbound to a heading for a 30 degree teardrop entry within the pattern (on the holding side) for a period of one minute, then turn in the direction of the holding pattern to intercept the inbound holding course.

(c) Direct Entry Procedure: When approaching the holding fix from anywhere in sector (c), the direct entry procedure would be to fly directly to the fix and turn to follow the holding pattern.

(d) While Other entry procedures may enable the aircraft to enter the holding pattern and remain within protected airspace, the parallel, teardrop and direct entries are the procedures for entry and holding recommended by the FAA. 4.

Timing-- (a) Inbound Leg: (1) At or below 14,000 Ft. MSL-1 minute.

Outbound leg timing begins over/abeam the fix, whichever occurs later. If the abeam position cannot be determined, start timing when turn to outbound is completed.

Pilot Action

(a) Start speed reduction when 3 minutes or less from the holding fix. Cross the holding fix, initially, at or below the maximum holding airspeed.

(b) Make all turns during entry and while holding at: (1) 3 degrees per second, or (2) 30 degree bank angle, or

(c) Compensate for wind effect primarily by drift correction on the inbound and outbound legs. When outbound, triple the inbound drift correction to avoid major turning adjustments; e.g., if correcting left by 8 degrees when inbound, correct right by 24 degrees when outbound.

(d) Determine entry turn from aircraft heading upon arrival at the holding fix; +/-5 degrees in heading is considered to be within allowable good operating limits for determining entry

5-44. INSTRUMENT APPROACH PROCEDURE CHARTS

1. Minimum Altitude will be depicted with the altitude value underscored. Aircraft are required to maintain altitude at or above the depicted value.

2. Maximum Altitude will be depicted with the altitude value overscored. Aircraft are required to maintain altitude at or below the depicted value.

3. Mandatory Altitude will be depicted with the altitude value both underscored and overscored. Aircraft are required to maintain altitude at the depicted value.

Minimum Safe Altitudes (MSA) are published for emergency use on instrument approach procedure (IAP) charts except RNAV IAPs. The MSA is defined using NDB or VOR type facilities within 25 NM (normally) or 30 NM (maximum) of the airport. The MSA has a 25 NM (normally) or 30 NM (maximum) radius. If there is no NDB or VOR facility within 30 NM of the airport, there will be no MSA. The altitude shown provides at least 1,000 feet of clearance above the highest obstacle in the defined sector. As many as four sectors may be depicted with different altitudes for each sector displayed in rectangular boxes in the plan view of the chart. A single altitude for the entire area may be shown in the lower right portion of the plan view. Navigational course guidance is not assured at the MSA within these sectors.

Minimum Vectoring Altitudes (MVA) are established for use by ATC when radar ATC is exercised. MVA charts are prepared by air traffic facilities at locations where there are numerous different minimum IFR altitudes. Each MVA chart has sectors large enough to accommodate vectoring of aircraft within the sector at the MVA. Each sector boundary is at least 3 miles from the obstruction determining the MVA. To avoid a large sector with an excessively high MVA due to an isolated prominent obstruction, the obstruction may be enclosed in a buffer area whose boundaries are at least 3 miles from the obstruction. This is done to facilitate vectoring around the obstruction.

The minimum vectoring altitude in each sector provides 1,000 feet above the highest obstacle in nonmountainous areas and 2,000 feet above the highest obstacle in designated mountainous areas. Where lower MVAs are required in designated mountainous areas to achieve compatibility with terminal routes or to permit vectoring to an IAP, 1,000 feet of obstacle clearance may be authorized with the use of Airport Surveillance Radar (ASR). The minimum vectoring altitude will provide at least 300 feet above the floor of controlled airspace.

5-45. APPROACH CLEARANCE

a. An aircraft which has been cleared to a holding fix and subsequently ``cleared . . . approach'' has not received new routing. Even though clearance for the approach may have been issued prior to the aircraft reaching the holding fix, ATC would expect the pilot to proceed via the holding fix (his last assigned route), and the feeder route associated with that fix (if a feeder route is published on the approach chart) to the initial approach fix (IAF) to commence the approach. When cleared for the approach, the published off airway (feeder) routes that lead from the en route structure to the IAF are part of the approach clearance.

b. If a feeder route to an IAF begins at a fix located along the route of flight prior to reaching the holding fix, and clearance for an approach is issued, a pilot should commence his approach via the published feeder route; i.e., the aircraft would not be expected to overfly the feeder route and return to it. The pilot is expected to commence his approach in a similar manner at the IAF, if the IAF for the procedure is located along the route of flight to the holding fix.

c. If a route of flight directly to the initial approach fix is desired, it should be so stated by the controller with phraseology to include the words ``direct . . .,'' ``proceed direct'' or a similar phrase which the pilot can interpret without question. If the pilot is uncertain of his clearance, he should immediately query ATC as to what route of flight is desired.

5-46. INSTRUMENT APPROACH PROCEDURES

a. Minimums are specified for various aircraft approach categories based upon a value 1.3 times the stalling speed of the aircraft in the landing configuration at maximum certificated gross landing weight.

b. When operating on an unpublished route or while being radar vectored, the pilot, when an approach clearance is received, shall, in addition to complying with the minimum altitudes for IFR operations (FAR Part 91.177), maintain his last assigned altitude unless a different altitude is assigned by ATC, or until the aircraft is established on a segment of a published route or IAP. After the aircraft is so established, published altitudes apply to descent within each succeeding route or approach segment unless a different altitude is assigned by ATC. Notwithstanding this pilot responsibility, for aircraft operating on unpublished routes or while being radar vectored, ATC will, except when conducting a radar approach, issue an IFR approach clearance only after the aircraft is established on a segment of a published route or IAP, or assign an altitude to maintain until the aircraft is established on a segment of a published route or instrument approach procedure. For this purpose, the Procedure Turn of a published IAP shall not be considered a segment of that IAP until the aircraft reaches the initial fix or navigation facility upon which the procedure turn is predicated.

c. When executing an instrument approach and in radio contact with an FAA facility, unless in ``radar contact,'' report passing the final approach fix inbound (non precision approach) or the outer marker or fix used in lieu of the outer marker inbound (precision approach).

5-47. PROCEDURE TURN

a. A procedure turn is the maneuver prescribed when it is necessary to reverse direction to establish the aircraft inbound on an intermediate or final approach course. It is a required maneuver except when the symbol NoPT is shown, when RADAR VECTORING is provided, when a holding pattern is published in lieu of procedure turn, when conducting a timed approach, or when the procedure turn is not authorized. The altitude prescribed for the procedure turn is a minimum altitude until the aircraft is established on the inbound course. The maneuver must be completed within the distance specified in the profile view.

1. On U.S. Government charts, a barbed arrow indicates the direction or side of the outbound course on which the procedure turn is made. Headings are provided for course reversal using the 45 degree type procedure turn. However, the point at which the turn may be commenced and the type and rate of turn is left to the discretion of the pilot. Some of the options are the 45 degree procedure turn, the racetrack pattern, the tear-drop procedure turn, or the 80 degree - 260 degree course reversal. Some procedure turns are specified by procedural track. These turns must be flown exactly as depicted.

2. A procedure turn need not be established when an approach can be made from a properly aligned holding pattern. In such cases, the holding pattern is established over an intermediate fix or a final approach fix. The holding pattern maneuver is completed when the aircraft is established on the inbound course after executing the appropriate entry. If cleared for the approach prior to returning to the holding fix, and the aircraft is at the prescribed altitude, additional circuits of the holding pattern are not necessary nor expected by ATC. If the pilot elects to make additional circuits to lose excessive altitude or to become better established on course, it is his responsibility to so advise ATC when he receives his approach clearance.

3. A procedure turn is not required when an approach can be made directly from a specified intermediate fix to the final approach fix. In such cases, the term ``NoPT'' is used with the appropriate course and altitude to denote that the procedure turn is not required.

b. Limitations on Procedure Turns.

1. In the case of a radar initial approach to a final approach fix or position, or a timed approach from a holding fix, or where the procedure specifies ``NoPT'', no pilot may make a procedure turn unless, when he receives his final approach clearance, he so advises ATC and a clearance is received.

2. When a teardrop procedure turn is depicted and a course reversal is required, this type turn must be executed.

3. When holding pattern replaces the procedure turn, the standard entry and the holding pattern must be followed except when RADAR VECTORING is provided or when NoPT is shown on the approach course. As in the procedure turn, the descent from the minimum holding pattern altitude to the final approach fix altitude (when lower) may not commence until the aircraft is established on the inbound course.

4. The absence of the procedure turn barb in the Plan View indicates that a procedure turn is not authorized for that procedure.

5-49. RADAR APPROACHES

a. The only airborne radio equipment required for radar approaches is a functioning radio transmitter and receiver. The radar controller vectors the aircraft to align it with the runway centerline. The controller continues the vectors to keep the aircraft on course until the pilot can complete the approach and landing by visual reference to the surface. There are two types of radar approaches: Precision (PAR) and Surveillance (ASR).

b. A radar approach may be given to any aircraft upon request and may be offered to pilots of aircraft in distress or to expedite traffic, however, an ASR might not be approved unless there is an ATC operational requirement, or in an unusual or emergency situation. Acceptance of a PAR or ASR by a pilot does not waive the prescribed weather minimums for the airport or for the particular aircraft operator concerned. The decision to make a radar approach when the reported weather is below the established minimums rests with the pilot.

c. PAR and ASR minimums are published on separate pages in the NOS Terminal Procedures Publication (TPP).

1. A PRECISION APPROACH (PAR) is one in which a controller provides highly accurate navigational guidance in azimuth and elevation to a pilot. Pilots are given headings to fly, to direct them to, and keep their aircraft aligned with the extended centerline of the landing runway. They are told to anticipate glide path interception approximately 10 to 30 seconds before it occurs and when to start descent.

2. A SURVEILLANCE APPROACH (ASR) is one in which a controller provides navigational guidance in azimuth only. The pilot is furnished headings to fly to align his aircraft with the extended centerline of the landing runway.

3. A NO-GYRO APPROACH is available to a pilot under radar control who experiences circumstances wherein his directional gyro or other stabilized compass is inoperative or inaccurate.

5-55. APPROACH AND LANDING MINIMUMS

a. Landing Minimums. The rules applicable to landing minimums are contained in FAR Part 91.175.

b. Published Approach Minimums. Approach minimums are published for different aircraft categories and consist of a minimum altitude (DH, MDA) and required visibility. These minimums are determined by applying the appropriate TERPS criteria. When a fix is incorporated in a nonprecision final segment, two sets of minimums may be published: one, for the pilot that is able to identify the fix, and a second for the pilot that cannot. Two sets of minimums may also be published when a second altimeter source is used in the procedure.

c. Obstacle Clearance. Final approach obstacle clearance is provided from the start of the final segment to the runway or Missed Approach Point, whichever occurs last.

5-56. MISSED APPROACH

a. When a landing cannot be accomplished, advise ATC and, upon reaching the Missed Approach Point defined on the approach procedure chart, the pilot must comply with the missed approach instructions for the procedure being used or with an alternate missed approach procedure specified by ATC.

b. Protected obstacle clearance areas for missed approach are predicated on the assumption that the abort is initiated at the missed approach point not lower than the MDA or DH.

c. If visual reference is lost while circling-to-land from an instrument approach, the missed approach specified for that particular procedure must be followed (unless an alternate missed approach procedure is specified by ATC). To become established on the prescribed missed approach course, the pilot should make an initial climbing turn toward the landing runway and continue the turn until he is established on the missed approach course.

d. At locations where ATC Radar Service is provided, the pilot should conform to radar vectors when provided by ATC in lieu of the published missed approach procedure.

e. When approach has been missed, request clearance for specific action; i.e., to alternative airport, another approach, etc.

5-57. VISUAL APPROACH

When it will be operationally beneficial, ATC may authorize an aircraft to conduct a visual approach to an airport or to follow another aircraft when flight to, and landing at, the airport can be accomplished in VFR weather. The aircraft must have the airport or the identified preceding aircraft in sight before the clearance is issued.

5-59. CONTACT APPROACH

a. Pilots operating in accordance with an IFR flight plan, provided they are clear of clouds and have at least 1 mile flight visibility and can reasonably expect to continue to the destination airport in those conditions, may request ATC authorization for a contact approach.

b. Controllers may authorize a contact approach provided:

1. The Contact Approach is specifically requested by the pilot. ATC cannot initiate this approach.

2.The reported ground visibility at the destination airport is at least 1 statute mile.

3.The contact approach will be made to an airport having a standard or special instrument approach procedure.

4. Approved separation is applied between aircraft so cleared and between these aircraft and other IFR or special VFR aircraft.

5-74. MISSED APPROACH

Pilot-- 1. Executes a missed approach when one of the following conditions exist:

(a) Arrival at the Missed Approach Point (MAP) or the Decision Height (DH) and visual reference to the runway environment is insufficient to complete the landing.

(b) Determined that a safe landing is not possible.

(c) Instructed to do so by ATC..................Sky wings

Mountains flying

BASIC PREMISES

Without exception, you must adhere to the two basic premises of mountain flying, whether flying "with the mountains" or over the mountains.
Always remain in a position where you can turn toward lowering terrain
The novice mountain pilot should plan to fly 2,000 feet above the terrain along the route of flight. When approaching within ½ to ¼ mile from the mountain ridges, turn to approach the ridge at a 45-degree angle. This permits an easy escape with less stress on the airplane if downdrafts or turbulence are encountered. Never, fly in a canyon where there is not room to turn around.
Never fly beyond the point of no return.
Flying beyond the "point-of-no-return" will lead to an accident.

When flying upslope terrain, the "point of no return" is defined as the position where, if you reduce the throttle to idle, you can lower the nose for a normal glide and perform a 180-degree turn without impacting the ground. At or prior to this point, circle away from the mountain to gain additional altitude before proceeding.

MOUNTAIN METEOROLOGY

A complete check of the weather is necessary to develop a go/no-go decision. Stay out of marginal weather areas. Winds aloft greater than 30 knots at cruise altitude usually means the novice pilot should delay or postpone the flight until more favorable conditions prevail.

Landing at Possum Creek airstrip, 10,010-foot elevation.

GROSS WEIGHT

The takeoff distance varies with the gross weight. A 10-percent increase in the takeoff gross weight (while not exceeding the maximum allowable gross weight) will cause a:

5-percent increase in the speed necessary for takeoff;
9-percent decrease in acceleration to takeoff speed, and
21-percent increase in the takeoff distance.

CLIMB OUT

The first consideration for takeoff from a strip surrounded by mountains is terrain clearance. A considerable amount of time may be required to circle, climbing to the en route altitude prior to turning on course.

DOWNDRAFTS

Use visualization to determine possible downdraft areas. Air behaves like water. Ask yourself, "What would water do if it were flowing like the winds aloft?" You can then picture areas of downdrafts, updrafts and splashes of turbulence. If you encounter unexpected downdrafts, diving–away from the visualized downdraft–to maintain airspeed will generally lessen the total displacement effect of the downdraft (altitude loss). Although the rate of descent is greater at the higher airspeed, you will be under the influence of the sink for a shorter period of time.

COURSE REVERSAL

Everyone flying in the mountains will encounter situations when it becomes necessary to make a 180-degree turn. Forget hammerhead turns, wingovers, chandelles and the other fancy maneuvers. By the time you figure out you are in trouble and need to turn around, there is insufficient speed to perform these maneuvers. To turn around, slow down. This will decrease the radius of turn. Pull back on the control wheel to trade airspeed for altitude if you have extra speed. Then make the steepest turn you can comfortably make, up to 60 degrees.

Airstrip (creek bed) west of Mt. Blackburn, Alaska. Youdon't make the standard left-turn departure here.

ARRIVAL

The mountainous terrain surrounding many airstrips prevents a normal descent from cruise altitude to pattern altitude. It is necessary to make progressive power reductions to prevent thermal stresses from being induced in the engine. This allows the engine to cool slowly, preventing not only thermal shock, but also preventing de-tuning. Always make smooth power changes when adding or reducing power.

CAUTION: This is not the total information you need to fly safely in the mountains. It is merely an outline of the minimum information that should be studied.


'Mountology' The psychology of mountain flying

"I know you believe you understand what you think I said, but I'm not sure you realize that what you heard is not what I meant."
This gobbledygook, adopted by the FAA more than 20 years ago for flight instructor clinics was their attempt to demonstrate and reinforce the importance of communication. 'Mountology' is my fancifully contrived word used to describe the following proposal. Without careful study this plan may appear to contain the same double talk and confusion as the above FAA statement. Observant contemplation will prove it is not profuse verbiage or redundancy, but rather, it will ensure greater safety in all mountain-flying operations. Conditioned in psychology means exhibiting or trained to exhibit conditioned reflex or response. Reflex means an unlearned or instinctive response to a stimulus. Instinct means an innate aspect of behavior that is unlearned, complex and normally adaptive. It is necessary to define some terms before trying to persuade you to train yourself to react in mountain flying situations like one of Pavlov's dogs. These terms are conditioned, reflex and instinct. An instinctive response to a stimulus does not work at all times in an airplane. For example, when an airplane is in a spin, your instinct is to pull back on the control wheel to raise the nose. You have been taught that then the nose is down, you pull back. It has worked before, but not adaptive. In a spin situation you must be trained to break the stall before pulling back on the control wheel. This training is a conditioned response.
True mountain flying—that is, terrain, contour or drainage flying, as opposed to flying well above the mountains—can be done with total safety only when the pilot becomes conditioned to apply the basic premised during flight, without having to think about them.

BASIC PREMISE #1

Always remain in a position where you can turn toward lowering terrain.
This axiom also encompasses the idea that you will not enter or fly in a canyon where there is not sufficient room to turn around. Another way of stating this truth is to have an escape route in mind and be in a position to exercise this option.

BASIC PREMISE #2

Do not fly beyond the point of no return.
This is the position when flying upslope terrain where, if you reduce the throttle to idle and begin a normal glide, you will have sufficient altitude to turn around without impacting the terrain. Flying beyond this point drives home the southern sheriff's warning, "You're in a heap of trouble, boy."
Constantly evaluate where you are and decide if you can lose altitude before having to turn the airplane. If not, you are narrowing your options substantially.
What happens when the pilot flies beyond the point of no return? First, and usually the less serious consequence, involves landing the airplane straight ahead into whatever terrain exists. This normally results in destruction of the aircraft, but with proper technique the occupants will survive. Proper technique means the airspeed is maintained to allow transition to a normal landing attitude (often upslope terrain) without stalling the airplane.

The second outcome of flying beyond the point of no return involves the stall-spin accident. Because there is insufficient altitude or maneuvering space to complete the turn around, the pilot may try to hurry the turn with excessive bottom rudder, thus yawing the airplane. This induces a stall-spin.

These aphorisms or basic premises of mountain flying are not instinctive. They must be conditioned responses. As an example, consider that at some point in your basic flight training your instructor began constantly challenging you to find an emergency landing site. After pulling the power off, he would say some like, "Your engine just failed, proceed as you would during an actual emergency.
Soon you became conditioned so that when the instructor pulled the power, you already had a suitable landing area picked out and you headed for it, even though you might have been oblivious to your surroundings just before the simulated power failure.
This type training unconsciously caused you to seek an emergency area each time you were with the instructor. Eventually this training transfers to encompass all the time you are flying. Although you do not need an instructor to condition you for mountain flying, it helps when you first begin mountain flying. It is necessary for you to constantly think about the axioms of flight until you become conditioned to unconsciously remain in a position where you can turn toward lowering terrain and never fly beyond the point of no return.

Have you ever been caught in an un-forecast downpour during a picnic? Or have you flown in an area of anticipated updraft, yet all you find are downdrafts? Occasionally the wind defies all common sense reasoning and visualization. When this occurs it is usually due to one or a combination of the following:
subsidence
inversion
terrain modification
valley breeze
mountain breeze
Circulation (This discussion is limited to the northern hemisphere)
A quick review of some basic weather phenomena helps make the point. Circulation refers simply to the movement of air about the earth's surface. The sun heats the Earth's surface unevenly. The most direct rays strike near the equator, heating the equatorial regions more than the Polar Regions. The equatorial region re-radiates to space less heat than is received from the sun, while the reverse is true at the poles. Yet the equator does not continue to get hotter and hotter, nor does the polar region get colder. The only explanation is that heat is transferred from one latitude to another by the actual transport of air. Warm air forced aloft at the equator begins to move north at high elevation. Coriolis force turns it to the right (east). This turning develops a strong band of winds, "prevailing westerlies," at about 30º north latitude. Similarly, cool air from the poles begins a low-elevation journey toward the equator. It is also deflected to its right by Coriolis force creating a belt of low-level "polar easterlies." The result is to create an temporary impasse that disrupts simple, convective transfer. The atmosphere seeks stability and in an attempt to reach equilibrium, huge masses of air overturn in the middle latitudes. Cold air masses break through the barriers, plunging southward. The result is a mid-latitude bank of migratory storms with ever-changing weather.

Air Mass

The large air masses are high pressure areas. In the northern hemisphere, high pressure areas circulate in a clockwise direction. The high pressure system depicted on weather maps should be visualized as a mountain of air. The mountain is composed of isobars or lines of equal pressure. Consider the isobars as topographic in nature. If they are far apart, the high pressure area has a shallow topography. When close together, there is a very steep slope to the mountain of air.
Where isobars are close together it indicates the air is squeezed into a smaller, more confined area with a steep slope creating a rapid flow of air and strong surface winds.
Between the high pressure areas will be areas of low pressure where the air flows counter-clockwise. Visualize the low pressure area as a valley between air masses.
None of the pressure areas are stagnant. The earth's atmosphere is in a constant state of imbalance, but there is always a tendency to regain a state of balance.
Wind
Three forces act on wind. The pressure gradient force drives the wind. Pressure gradient is the decrease of pressure with distance and is in the direction of greatest decrease, thus, pressure gradient is from higher to lower pressure and perpendicular to the isobars. If pressure gradient was the only force acting on the wind, wind would always blow perpendicular to the isobars.
Rotation of the earth generates a force that deflects from a straight path any mass moving relative to the earth's surface. Coriolis force is zero at the equator and increases with latitude to a maximum at the poles. It is at a right angle to wind direction and is directly proportional to wind speed. Air in motion, due to pressure gradient, blows straight across the isobars from higher to lower pressure. When the air is in motion, Coriolis force begins to act at right angles to the wind, turning it to the right. Coriolis force continues to deflect the wind until is is blowing parallel to the isobars. Coriolis force and pressure gradient force balance, and above surface friction (about 2,000 feet), causes the wind to blow parallel to the isobars. The winds at the earth's surface do not blow parallel to the isobars. Instead, they cross the isobars at an angle from higher to lower pressure. Frictional force always acts opposite to wind direction. As friction slows the wind speed, Coriolis force decreases; however, friction has no effect on pressure gradient force. Pressure gradient and Coriolis forces are no longer in balance. Above 2,000 feet AGL the wind blows parallel to isobars. Below that altitude, friction causes the surface wind to blow 45º inward toward a low-pressure area and 45º outward from a high-pressure area.
Subsidence
Variations in temperature and humidity create a contrast in pressure and density. The pressure differences drive a complex system of air currents in a never-ending attempt to attain equilibrium.
Suppose an air mass (high pressure area) arrives over the plateau area of the upper Arkansas River Valley near Leadville, Colorado. The down flow, sinking are may be a stronger force than the prevailing winds aloft. The pilot departing Aspen and flying up the Roaring Fork River toward Independence Pass will be hard pressed to find an updraft in the face of this down flow. Yet it's always been there before. This pilot may be an accident waiting to happen. According to Aviation Space Environment Medicine, 232 airplanes crashed within 50 nautical miles of Aspen, CO, between 1964 and 1987. A total of 202 people died and 69 were seriously injured. This points out the need for better training in mountain flying.

Inversion

Often there is a layer of air within the troposphere that is characterized by an increase of temperature with altitude. It is called an inversion and is usually confined to a shallow layer.
Widespread sinking air (subsidence) is heated by compression and may become warmer than the air below it causing the inversion. The most frequent type of inversion over land is that produced immediately above the ground on a clear, still night. The ground loses heat rapidly through terrestrial radiation, cooling the layer of air next to it. Frontal inversions are also found in association with movement of colder air under warm air or the movement of warm air over cold air.

In a valley, expect the prevailing westerly winds to flow down the east-facing side of the mountain on the downwind side, pass through the valley and flow up on the west-facing upwind side of the next mountain. An inversion may place a cap over the area preventing the wind from flowing down the mountain. But when the wind strikes the terrain on the downwind side of the valley, it may tuck and move down the mountainside. With enough velocity, it may continue across the valley and up the other side.

Uneven terrain features may cause the air flow to be deflected downslope on what is considered the updraft side of the mountain. In the absence of wind, the sun's heating of the surface will produce convection currents known as anabatic lift.

During the day, the sun warms the valley walls and its adjacent air. The heated air being less dense will—lacking strong prevailing winds—rise gently upslope and is known as a valley breeze. The east facing mountain will receive the benefit of the sun's rays first and may cause a downslope wind on the west-facing slope as air rushes down to fill the evacuated air.
The valley breeze begins early in the morning and depending on the elevation of the mountain and the heat of the sun, may reach a peak speed of around 10 knots by noon. The significance of this is that when landing on an airstrip in a drainage, there will be a tailwind to contend with. The average wind speed is 6-8 knots.

Mountain Breeze

During the late afternoon and evening the valley walls cool quickly, cooling a layer of air next to the slope. This more dense air moves downslope into the valley causing the mountain breeze (gravity or drainage wind). The slopes cool at a rate faster than they heat up, so the mountain breeze may be stronger than the valley breeze, averaging 10-12 knots. Departing downslope will mean the airplane may be subject to the tailwind.
Coping
We tend to think in constants when contemplating the weather and associate whatever is happening as affecting a large area. Often a phenomena is isolated or may crop up in various isolated areas. Despite what is happening or where it is happening, it is important to visualize what is going on. Air is fluid, similar to water—although less dense. Ask "What would water do in this situation?" More often than not the picture becomes clear, you will know where there are areas of lift, sink and turbulence. So what will happen to the pilot heading up the Roaring Fork River toward Independence Pass? As long as he remains in a position where he can turn to lowering terrain and does not fly beyond the point of no return, Mother Nature will not have a chance to perform a "got-cha." The "point of no return" is defined as a point on the ground of rising terrain where the terrain out climbs the aircraft. The turn-around point is determined as the position where, if the throttle is reduced to idle, the aircraft can be turned around during a glide without impacting the terrain. Never fly beyond this point of no return. Turn around and maneuver for additional altitude prior to continuing. (By the way, it is not proper technique to reduce the throttle for the turn around; this merely denotes the point where the turn around must be initiated.)

Experienced pilots sometimes get into trouble with density altitude. It's not that they don't know what it is, it's just that they become complacent.


Federal Aviation Regulation 91.116 Pre-flight Action requires that a pilot check the density altitude.

(b) For any flight, runway lengths at airports of intended use, and the following takeoff and landing distance information ... other reliable information appropriate to the aircraft, relating to aircraft performance under expected values of airport elevation and runway slope, aircraft gross weight, and wind and temperature.

Density altitude is a term that sometimes causes confusion. A high-density altitude is NOT a good thing. Density altitude is defined as the pressure altitude corrected for non-standard temperature variations. And while this is a correct definition, my definition is perhaps more appropriate:

DENSITY ALTITUDE IS THE ALTITUDE THE AIRPLANE THINKS IT IS AT, AND PERFORMS IN ACCORDANCE WITH.

Density altitude can be computed on a density altitude chart, flight computer, electronic flight calculator or by rule of thumb. Density altitude gives us some idea about the expected performance of the airplane, but only if you apply the information to the performance charts. The DENALT performance computer gives values to be multiplied by the sea level takeoff and sea level rate-of-climb to predict the expected performance under current density altitude conditions.
This special DENALT calculator has information for both fixed-pitch propeller or constant-speed propeller airplanes. The sea level performance can be written at the bottom. The temperature is selected at the top center, then the pressure altitude is selected along the center, to the left for take-off factors and to the right for rate-of-climb percentage. Multiply the sea level performance by the factor and obtain the expected performance of the airplane.

An accurate rule of thumb (usually any error will be less than 300 feet) for determining the density altitude is easy to remember. For each 10-degrees Fahrenheit above standard temperature at any particular elevation, add 600 feet to the field elevation. (And, conversely for each 10-degrees F below standard temperature, subtract 600 feet.)
Standard temperature at sea level is 59-degree Fahrenheit. For elevations above sea level, subtract 3.5 degrees per thousand feet of elevation from the sea level temperature of 59 degrees. For example, at Jackson, Wyoming the elevation is 6,444. Multiply 6.444 times 3.5 for 22.55. Subtract this from 59 (59-22.55) for 36.45. The standard temperature at Jackson is 36.5 degrees. If the existing temperature is 80 degrees, subtract (80-36.5 = 43.5). Divide this difference by 10 degrees (for each 10-degrees F above standard), and multiply 4.35 times 600 (600 feet per 10 degrees) equals 2,610. Add 2,610 to the field elevation (6,444) for a density altitude of 9,054. Under the existing conditions (of our example), the airplane will perform as it would on a standard day at 9,054 feet elevation.

Density altitude not only affects the takeoff distance and rate of climb, but also applies to the service ceiling of the airplane while en route.

A simple rule of thumb for determining takeoff distance exists that helps you deal with density altitude during takeoff. The only problem is that it does not guarantee rate of climb after takeoff, but it insures that you will be able to takeoff in the distance available for the runway involved.

Do's and Don'ts
DO'S AND DON'TS OF MOUNTAIN FLYING

DON’T fly into unimproved mountain strips without a minimum of 150-hours total flight experience. Even then, be proficient at slow flight maneuvering and the spot method for landing.

DON’T plan a cross-country flight into the mountains when the wind at mountaintop level exceeds 30 knots unless you are experienced in this type operation (strong updrafts, strong downdrafts and moderate or greater turbulence). This does not preclude taking a “look-see.” Often with a stable air mass the air will contain very little turbulence during these high-wind conditions. Expect the wind velocity to double or more in mountain passes and over the ridges due to a venturi effect.

· DON’T choose a route that would prevent a suitable forced-landing area.
· DON’T leave the airplane without a compelling reason if you have executed an emergency or precautionary landing. Temporary evacuation may be necessary if a fire hazard exists.

DON’T go if the weather is doubtful or “bad.”
· DON’T become quiescent with weather reports of ceilings of 1,000-2,000 feet. The ceiling is reported above ground level. Often, in the mountains, the weather reporting facility will be surrounded by mountains that extend thousands of feet higher than the facility. Clouds may obscure the mountains and passes in the vicinity.
DON’T fly VFR or IFR in the mountains in an unfamiliar airplane make and model. It is required that you learn the flight characteristics, slow flight and stalls in various configurations, beforehand.
· DON’T make the landing approach too slow. Some pilots feel they have to make a low approach on the backside of the power curve to get into a mountain strip. This “hanging on the prop” is a dangerous operation. Use a stabilized approach for all landings.
· DON’T operate low-performance aircraft into marginal mountain strips. If in doubt about your takeoff, use the “sufficient runway length” rule of thumb.

DON’T rely on cloud shadows for wind direction (unless you are flying at or near the cloud bases). Expect the wind to be constantly changing in direction and velocity because of modification by mountain ridges and canyons.
· DON’T fly close to rough terrain or cliffs when the wind approaches 20 knots or more. Dangerous turbulence may be encountered.
· DON’T fail to realize that air, although invisible, acts like water and it will “flow” along the contour of the mountains and valleys. Visualize where the wind is from and ask yourself, “What would water do in this same situation?”
DON’T slow down in a downdraft. By maintaining your speed, you will be under the influence of the downdraft for a lesser period of time and lose less altitude overall.

· DON’T forget or fail to realize the adverse effect of frost. Less than 1/8 inch of frost may increase the takeoff distance by 50 percent and reduce the cruise speed by 10 percent. Often, if the airplane becomes airborne, the smooth flow of air over the wings is broken up by the frost and the extra drag prevents the airplane from climbing out of ground effect.
· DON’T give insufficient attention to the importance of fuel and survival equipment. It is important to keep the airplane light, but don’t skimp on these items.

o DON’T fly the middle of a canyon. This places you in a poor position to make a turnaround and it subjects you to shear turbulence.
· DON’T fail to use the same indicated airspeed at high-altitude airports that you use at low-altitude or sea level airports for the takeoff or for the approach to landing.
· DON’T be too proud or too vain to check with experienced mountain pilots concerning operations to and from unfamiliar fields.
DON’T attempt VFR flight in mountainous terrain unless you have the minimum visibility you have established as a personal safety standard.

· DON’T become complacent about the horizon when flying with outside visual reference. A gentle upslope terrain may cause an unknown constant climb with the possibility of an inadvertent stall. The horizon is the base of the mountains some six to eight miles away.
· DO file a flight plan for each leg of your flight. Also, make regular position reports to allow search and rescue personnel to narrow down the search area if you are overdue on the flight plan.

DO check all aspects of the weather including weather reports and forecasts.
· DO familiarize yourself with the high-altitude characteristics and performance of your airplane. This includes the takeoff and landing distance and rate of climb under various density altitude conditions.
· DO spend some time studying the charts to determine the lowest terrain along the proposed route of flight. If possible, route the flight along airways.
· DO have confidence in the magnetic compass. The compass (unless it has leaked fluid or someone has placed interfering metal near its magnets) is the most reliable instrument. Charts will show the areas of local magnetic disturbance that may affect the accuracy of the compass reading.
· DO plan the fuel load to allow flight from the departure to the destination airport with a reserve to counter unexpected winds.
· DO fly a downdraft, that is, maintain speed by lowering the nose of the airplane. Unless the airplane is over a tall stand of trees or near a shear cliff, the downdraft will not extend to the ground (exception: microburst).
DO use Sectional Aeronautical Charts instead of World Aeronautical Charts (WAC) because of the greater detail (8 miles per inch).

· DO approach ridges at an angle. The recommendation is to use a 45-degree angle approach when in a position of one-half to one-quarter mile away. This allows an escape, with less stress on the pilot and airplane, if unexpected downdrafts or turbulence are encountered. Flying perpendicular to the ridge, rather than at a 45-degree angle, does not mean you cannot escape the downdraft or turbulence by making a 180-degree turn. But, it does mean the airplane will be subjected to the effects of the downdraft and turbulence for a greater period of time. Usually, a steeper bank will be required to make the 180-degree turn. This will increase the g-loading stress on the airplane.

DO use horse sense (common sense) when performing takeoffs or landings at mountain strips. If you have any doubt about the operation, confirm the aircraft performance using the Pilot’s Operating Handbook or Owner’s Manual. If the physical conditions are adverse and compromise the operation, delay the operation until conditions are better.

DO count on the valley breeze (wind blowing upstream during the morning hours) and the mountain breeze (wind blowing downstream during the evening hours). In an otherwise calm wind condition the valley breeze will create an approximate 4-knot tailwind for landing upstream. The mountain breeze will cause an approximate 8-knot to 12-knot tailwind for takeoff downstream.

· DO make a stabilized approach for landings. Since the late ‘60s the power-off approach has been discouraged because of thermal shock to the engine.
· DO remember your study of aerodynamics. It is possible to stall the airplane at any airspeed and any attitude (providing you are strong enough and the airplane doesn’t break first). If a stall is entered in the same manner, for example, with a slow deterioration of the airspeed, it will stall at the same indicated airspeed at all altitudes.

The Aeronautical Information Manual, paragraph 574 states, “Your first experience of flying over mountainous terrain, particularly if most of your flight time has been over the flatlands of the Midwest, could be a never-to-be-forgotten nightmare if you are not aware of the potential hazards awaiting … Many pilots go all their lives without understanding what a mountain wave is. Quite a few have lost their lives because of this lack of understanding. One need not be a licensed meteorologist to understand the mountain wave phenomenon.”
Perhaps other than IFR weather, nothing affects the pilot flying in the mountains more than the mountain wave.
To develop an understanding of the mountain wave, we need to ask and answer some questions:
What is a mountain wave?
What forms it?
Why is it of concern to pilots?
What are its distinguishing characteristics?
How do we deal with it?

The most distinctive characteristic of the mountain wave is the lenticular cloud. This is a "signpost of the sky" indicating that mountain wave activity is present.
Someone has come up with all kinds of names for the mountain wave. There is the:
· Mountain wave
· Standing wave
· Lee wave
· Gravity wave
· Standing lenticular
· ACSL (altocumulus standing lenticularis)
· Or just plane "wave"
· Pilots have developed a few names of their own, but we can't mention them here.
The wave that forms over the mountain is more properly called the "mountain wave." The waves downwind from the mountain are the "standing wave" or "lee wave." Pilots have come to accept all of these names for wave activity, regardless of position of the lenticular clouds.
How does the atmosphere go about setting up a mountain wave condition? It needs three elements:
· Wind flow perpendicular to the mountain range, or nearly so, being within about 30 degrees of perpendicular.
· An increasing wind velocity with altitude with the wind velocity 20 knots or more near mountaintop level.
· Either a stable air mass layer aloft or an inversion below about 15,000 feet.
Because of these elements, the weather service is able to predict the mountain wave condition with over 90-percent accuracy.

we have likened an atmosphere with low stability to a flimsy spring that offers little resistance to vertical motion. So while the lower coils move easily up and over the mountain, the jolt received at ground level is not transmitted very far upward.
represents a stable atmosphere that is similar to a tough, heavy spring. This air, when it strikes the mountains, tends to suppress internal vertical motion. It is essentially too tough for oscillations to be set up.
we have an arrangement of a strong coil sandwiched between two weaker springs to simulate an atmosphere with a stable layer sandwiched between areas of lesser stability. With this arrangement it is conceivable that the strong spring will continue to bounce up and down for some time after the parcel of air has crossed the mountain ridge. With a stable layer (or inversion aloft) the air stream is both flexible enough to be set in vertical motion and elastic enough to maintain that motion as a series of vertical oscillations.
As the air ascends, it cools and condenses out moisture, forming the distinctive lenticular clouds. As it descends, it compresses and the heat of compression reabsorbs the moisture. It goes through this up and down action many times forming a distinctive lenticular cloud at the apex of each crest, providing there is sufficient moisture present for the cloud formation.

The up-and-down action forms a trough at the bottom of its flow and a crest at the top of the flow. The distance from trough to trough (or crest to crest) is called the wave length. The wave length is directly proportional to wind wind and inversely proportional to stability.
The wave length is used for visualization. In the area from the trough to the crest is an area of updrafts. The area from the crest to the trough is predominately downdrafts.
In the intermountain west the wave length can vary from about 2 nautical miles to over 25 nautical miles. It averages 8 miles and extends downrange about 150-300 nautical miles. Satellite photos have shown the wave capable of extending over 700-nautical miles downwind from the mountain range.

Cap cloud of the Teton mountain rangeThis cloud is mostly on the windward side of the mountain.
FoehngapThe foehngap exists because moisture isreabsorbed during the down rush of air.
With sufficient moisture three typical wave clouds will form, although there are four types of clouds associated with the wave.
Cap cloud (foehnwall)
Lenticular
Roll (rotor, arcus)
Mother-of-Pearl
The presence of clouds merely point out wave activity and not wave intensity at any particular level. Because moist air takes less vertical distance to reach its condensation level than does dryer air, the presence of a lenticular cloud is not necessarily an indication of the strength of the updrafts or downdrafts in a mountain wave.
For example, high altitude lenticulars may indicate there is sufficient moisture at that altitude to form them, when in fact the strongest wave lift and sink occurs at a lower altitude where there isn't enough moisture to form the lenticular clouds. This is one reason visualization is so important.
The mother-of-pearl or nacreous cloud is a pancake-shaped cloud that is extremely thin and visible for only a short time after sunset or before sunrise when the sky is dark. It is normally seen in latitudes higher than 50-degree north, or over Antarctica. It is best seen in the polar regions at 80,000 to 100,000 feet when the sun is below the horizon.
Lenticulars over Montana
Rotor cloud in Alaska

The lenticular cloud appears to be stationary although the wind may be blowing through the wave at 50 knots or more. The wave lift can extend into the stratosphere, more than 10 miles above sea level, so you can't escape wave effects by flying over them. What are the flight conditions in lenticular clouds? Generally the lenticular area will be quite smooth. The only danger is the magnitude of the sustained updrafts and downdrafts. Usually individual lenticulars are composed of ice crystals, but when they are composed of super-cooled water droplets watch out for severe icing conditions.
Line of rotors - Calgary

Normally the rotor clouds are centered beneath the lenticular cloud. Most often it extends anywhere from ground level to mountaintop level, but is frequently observed up to 35,000 feet. Destructive turbulence from the rotor rarely exists more than 2,000-3,000 feet above mountaintop level. The rotor is described as a "dark, ominous-looking cloud with a rotating appearance." If it forms near the ground where it can pick up dust and debris, it is dark and ominous looking, but more often it looks similar to a fair-weather cumulus. Turbulence is most frequent and most severe in the standing rotors just beneath the wave crests at or below mountaintop level (visualization is helpful where there is insufficient moisture to form the rotor or the lenticular).
The rotor area forms beneath the lee wave where a large swirling eddy forms. Sometimes with an inversion (normally stable air), turbulence succeeds in overturning the air in the stable layer. Once warm air is suddenly forced beneath colder and denser air a vigorous convection is set up in an attempt to restore normal equilibrium. This makes the roll cloud a particularly turbulent hazard. If the top of the cloud is rotating faster than the bottom, avoid the area like the plague.
The most dangerous characteristic of the standing wave is the rotor. The rotor can be assumed to exist whenever a mountain wave forms, but a cloud will not always form to alert you to its presence. Avoid the area where the rotor will form with visualization.
Often the three conditions that must exist to form a mountain wave will exist (perpendicular wind flow, increasing wind velocity with altitude, and a stable air mass layer or inversion) ... but there is insufficient moisture for the wave clouds to form. This is called a dry wave. All of the updrafts, downdrafts and rotor turbulence exists, you just can't see the clouds. You must use visualization.
Just because a mountain wave exists, it is not a sure sign that your flight must be delayed or cancelled. The degree of stability can be determined from pilot reports or by a test flight.

Mountain wave safety practices

Altitude 50 percent above the terrain - Turbulence caused by extreme mountain waves can extend into all altitudes that you might use, but dangerous turbulence can usually be avoided by clearing the mountains at least half again as high as the height of the mountain. In Colorado there are 54 peaks over 14,000-foot elevation. Does this mean we have to fly at 14,000 plus one-half (7,000) or 21,000 feet? No, use the base of the terrain to begin measuring. For example, if the surrounding terrain is 10,000 feet and the mountaintop is 14,000 feet, use one-half of the 4,000-foot value and fly 2,000 feet above the mountaintops.
Approach at a 45-degree angle - The rule-of-thumb of flying half again as high as the mountain is designed to reduce the risk of entering the turbulent rotor zone, but it does not necessarily give you a sufficient margin to allow for height loss due to downdrafts. You must have an escape route.
Avoid ragged or irregular-shaped lenticulars - Ragged and irregular-shaped lenticulars can contain the same turbulence as the rotor area.
Climb in lift - Dive in sink - By diving in sink, rather than trying to maintain altitude, the airplane is exposed to the effects of the downdraft for a lesser amount of time. Even though the rate of descent will likely be double or more the rate of climbing at the best rate-of-climb airspeed, the airplane will loose less altitude overall.
Avoid the rotor - If rotor clouds are not present, visualize the area of the rotor and avoid it.
Visualize the wavelength - When flying parallel to the wave, fly in the updraft area.

LENGTH

Operating at mountain airstrips presents us with various passenger loads and different density altitude conditions for nearly each takeoff. These factors combine to provide a loss of performance, creating concerns about whether or not the runway is long enough for takeoff.
You might not be too concerned about landing at this airstrip. There are unobstructed approaches from either end. But, when it comes time to depart, you might have some doubts about the runway length. We have a rule of thumb that can determine if the runway length is adequate for the takeoff; although, it will not guarantee rate of climb after the takeoff. The POH (pilots operating handbook) should be consulted to determine the rate of climb.
Airstrip runs NW-SE on right side


The rule really is quite simple. It states: "Ten times the square root of the percentage of liftoff distance required is equal to the percentage of liftoff speed that should be attained in that distance."
Because airplanes stop better than they accelerate, we can easily accelerate to the halfway point of a runway and determine if there is sufficient performance to continue the takeoff. If there is insufficient speed, we can easily stop in the remaining half of the runway. (This really doesn't work well on downhill runways.)
So we will use the halfway point of the runway for "liftoff distance required."
Remember, this rule of thumb does not guarantee that the rate of climb will be sufficient to clear any obstacles after takeoff, but it does guarantee there is sufficient runway for the takeoff.
Mark the halfway point on the runway. This might require you to walk the length and count your steps, then walk back and determine a distinguishing characteristic or place a flag or marker at this point.
Using the rule, "10 times the square root of the percentage of liftoff distance," we use 50 percent for the liftoff distance and the square root of 50 is 7.07. Ten times 7.07 equates to 70.7 percent of the liftoff speed should be obtained at the halfway point to guarantee takeoff in the remaining half of the runway. If you have the speed, continue. If you do not have the speed abort the take off.

There is a concern about the use of flaps for takeoff from a backcountry strip among many pilots. Should flaps be used or not, and if used, how much flap should be used?
The majority of mountain pilots agree ... flaps should be used for takeoff.
How much flaps? The POH or Owner's Manual may give a recommendation, in which case you are obligated to use their wisdom. But, if there is no blessing listed, the following procedure will provide the maximum lift from any particular airfoil section.

Begin by making full control deflection, aileron control (wheel or stick) moved full left in this picture. This represents the maximum lift for the airfoil design. Remember, lift and drag are directly proportional. Increase lift and you increase drag. Here the manufacturer determined the maximum lift for the aileron deflection is obtained at the particular angle formed.


Next, match the flap deflection to the aileron deflection. This provides the maximum amount of lift for the airfoil (considering the effect of drag). This works for normally aspirated engines. With the Cessna-type airplanes, it is necessary to parallel the flap deflection to match the aileron deflection since they are not side-by-side. This will result, for example, in about 12-degrees flap extension in the Cessna 150-170 series airplanes.
If your airplane happens to be a turbo-super charged wild duck, or some such derivative, the flaps will probably be set at 50 percent because you are not as concerned with the balance of engine power and lift.

CANYON FLYING

Most pilots don't read a book about aerobatics and go out to practice on their own. Flying in canyons (even if you read the superb Mountain Flying Bible) is usually done after you have gained experience from someone knowledgeable in canyon flying.
Who is knowledgeable? Your flight instructor.


Generally speaking the best path to fly through a canyon will be on the updraft side (a narrow canyon is the exception). The canyon may be more or less level terrain, or it may be sloping terrain.
The airplane will have to be close to the mountain side to take advantage of the potential orographic lift. Maneuver the airplane to within a couple of hundred yards of the canyon side if lift is desired. Beyond this area the lift is insignificant.
Novice pilots often fly down the center of a canyon. This places them the farthest away from the sides of those scary old mountains. But, this is not the correct position for the airplane.

There are two good reasons for flying the side of a canyon.
First, you will avoid the shear area caused by the mixing of air flowing down one side and up the other side.
And, second, you will be in a better position from which a turnaround can be safely made. You have the full canyon width to perform the turnaround maneuver if the terrain becomes unsuitable, adverse weather is encountered or you don't want to be there.


Remember the basic premises?Basic permisis Always remain in a position to turn to lowering terrain; and, never fly beyond the point of no return. These two axioms encompass the idea that you will never enter a canyon if there is not room to turn around.
Only fly in a canyon when there is adequate room to allow a turnaround. Otherwise, fly the terrain. That is, gain altitude and over-fly the canyon area from the high end to the low end.

It doesn't matter which side you fly down a canyon, either the updraft or downdraft side, because flying downhill makes it easy to transition to either side. Normally we associate updrafts with the sunny side of a mountain, but in canyons it depends on the airflow down a slope more than whether or not the sun is shining on the surface.
The majority of mountain instructors will caution you when flying in canyons to gain sufficient altitude to go to the head of the canyon and then fly downslope terrain. This is sage advice. But, often it is necessary to fly up canyons (fire patrol, game and fish surveys, search and rescue, law enforcement).

FLYING UP CANYONS

There is nothing wrong with flying up canyons ... when you do it properly. In addition to never entering a canyon where there is not room to turn around, you must remain in a position that allows a turnaround if the canyons narrows or if the terrain begins to out climb the airplane. It is a good idea to fly at a speed faster than Vx (best angle-of-climb airspeed).


Have you ever flown over water beyond power-off gliding distance from the shore? Have you noticed the engine goes to "automatic rough?" You start hearing strange noises that you haven't noticed before. The oil pressure gauge begins ticking and the engine seems to run rough.
A similar thing happens when flying upslope terrain in a canyon. Your left arm become shorter and the airspeed decreases without you noticing it. When flying up a canyon, fly the UPDRAFT SIDE. If you can't gain altitude on one side, try the other side (Mother Nature may be fooling you about which side has the updraft).

FLYING UP NARROW CANYONS

One thing can be said about flying up narrow canyons ... if it's not done properly, it's not habit forming. Until you are experienced (with a knowledgeable mountain instructor), stay out of these areas.
Speaking of a mountain instructor, do you have to fly with a certified flight instructor to obtain mountain flight instruction? Absolutely not. Many excellent, knowledgeable pilots can provide a wealth of information about mountain flying, but they can't sign your logbook. Do you really care? I don't. I will take learning from whatever source I can.
Let's define a narrow canyon. This is one, where, if you have to turn around the turn radius exceeds one half the canyon width. This can be intimidating to experienced mountain pilots when conditions aren't perfect.
Flying up a narrow canyon requires a different technique from the "regular" canyon. Rather than flying the updraft side, you are better off flying the downdraft side. This way, if you get into trouble, when you turn around you won't be getting into a worse situation. You will be entering an area of updraft during the turn. BUT REMEMBER, the turnaround will be subject to a tail wind that will increase the radius of turn.


It is not uncommon when flying in unfamiliar terrain to encounter a blind canyon. Blind canyons leading to a dead end shouldn't be a problem, but they are. The reason is that the pilot violates the basic premises of mountain flying.
To avoid potential problems stay out of canyons where there is not room to turn around, remain in a position to turn to lower terrain, and never fly beyond the point-of-no-return.


BASIC PREMISES OF MOUNTAIN FLYING

Always remain in a position where you can turn toward lowering terrain.
Never fly beyond the point of no return.

THE POINT OF NO RETURN

The "point of no return" is defined as the point on the ground of rising terrain where the terrain out climbs the aircraft. The turn-around point is determined as the position where, if the throttle is reduced to idle, the aircraft can be turned around during a glide without impacting the terrain.
(It is not proper technique to reduce the throttle for the turnaround. This merely denotes the point where the turnaround must be initiated.)

TURN AROUND POINT

More important than the "point of no return" is the "turn around point." What or where exactly is this position where, if the throttle is reduced to idle, the aircraft can be turned around during a glide without impacting the terrain?
The reason it is an elusive value is because of the variables that may be encountered. If the airplane is flying upslope terrain at a high speed, the turn around point will be further up the upslope than it would be if the airplane is flying at minimum airspeed.
Usually, if a pilot gets into trouble while flying upslope terrain, he has experienced a phenomena known as "short arm" effect. The self-preservation instinct causes a pilot to unconsciously pull back on the control wheel to avoid the rising terrain. The airplane slows down and this reduction in airspeed is usually imperceptible to the pilot, who is probably directing his attention outside the airplane.
As the pilot, flying at or near the minimum controllable airspeed, realizes he needs to turn around, the density altitude may preclude a level flight turn around. It becomes necessary to trade altitude for airspeed during the turn. This is the main reason for the definition of the "turn around point."
One of the maneuvers we demonstrate at the Montana Aeronautics Search Pilot Clinic is the "turn around point."

CAUTION: Let me caution you before we begin, "don't do this at home." If you decide that you need to do this training maneuver for whatever reason (it really isn't necessary), have an experienced pilot accompany you.

DEMONSTRATION – TURN AROUND POINT

NOTE: This demonstration is not required to safely fly in the mountains. Search pilots operate close to the terrain (500 feet vertically and 500 feet laterally) on a continuous basis. It is felt this demonstration, with the required steep nose-down attitude, will help prevent complacency and cause the search pilot to continually be aware of his position and altitude.
While flying upslope terrain in a canyon, the "student" (actually, the participants are all experienced pilots) is asked to determine the turn around point. The Cessna 182 or T-41 is used for the backcountry flying in this course.
The instructor must monitor the position diligently in order not to fly beyond the turn-around point. This is definitely a place where complacency will "get you."


This picture shows flying up a canyon after completing the last pass of a contour search

The contour search began at the top of the ridge and moved back and forth with step-downs in 500-foot intervals

This is the last pass of the contour. In this case it results in the airplane flying upslope terrain at low altitude

The airspeed is 80 knots indicated, the speed used for the contour search technique. When the student determines the turn around point, the throttle is reduced to idle and the turn around is commenced. Because of the slow speed it is necessary to lower the nose to a position most students consider excessive; however, to maintain a constant airspeed, it is required.

The student continues up the canyonuntil reaching the "turn around point"

At the "turn around point" the throttle isreduced to idle and a gliding turn is begun

Because of the slow speed the nose must be lowered to maintain 80 KIAS. Operation in a confined area may also require a steep turn. Lowering the nose further is necessary to maintain the constant 80-KIAS airspeed.

It is in this area of the turn that the 'student's' heart rate increases. The nose is pointed downward and the airplane is approaching the trees.


If the student has judged the position properly, the airplane will complete the 180-degree turn just over the tree tops at 80 knots indicated airspeed.

At the completion of the turn theairplane is just above the tree tops

A climb, with power, is initiated after the studentdetermines he has cleared the tree tops
Most students find this demonstration quite exuberating ... and most of the time the instructor does too. This demonstration is made with the power at idle. If the student misjudges the turn-around point, power is used to get out of the situation, so it is not as dangerous as it may appear.
Required Altitude
What altitude is required for the Cessna 182 to complete the 80-KIAS turn around? It's going to be about 400-500 feet above ground level, probably closer to 500 feet.

BOX CANYON TURN

I can't imagine anyone needing the box canyon turn under normal circumstances. If you need this maneuver, you have violated the laws of mountain flying. By keeping the basic premises in mind, you will never be in a position where you will need this maneuver; however, it is fun to play around.
To explain the box canyon turn it is necessary to consider two scenarios. In the first, the pilot is flying along at cruise power setting and cruise airspeed. In the second case, the pilot is flying at minimum controllable airspeed. This minimum controllable airspeed is probably not an intentional flight condition.
Flying over water beyond the power-off gliding distance from the shore, sometimes causes the oil pressure gauge to begin ticking. And it hasn't done that before. Next the engine may appear to give a little shudder of roughness. This might happen several times before you again approach the safety of the shoreline.
A similar phenomenon occurs when flying upslope terrain in the mountains. Your left arm becomes shorter. This is a normal self-preservation aspect of flight. You unconsciously pull away from the rising terrain and often the deterioration of airspeed goes unnoticed.
Conditioned Response
Mountain flying, like Mother Nature, can be harsh and unforgiving for the novice who fails to adhere to the two basic premises for all mountain flying: It’s really a simple matter to flirt with the mountains if you always remain in a position to be able to turn toward lowering terrain and never fly beyond the point of no return.
The first law, being able to turn while having some extra altitude to descend, does encompass the idea that you never enter into a canyon if there is not sufficient room to turn around.
The second law, to never fly beyond the point of no return, requires the pilot to establish a turn-around point whenever flying upslope terrain. The point of no return is defined as a point on the ground of rising terrain where the terrain out climbs the aircraft. The turn-around point is determined as the position where, if the throttle is reduced to idle, the aircraft can be turned around during a glide without impacting the terrain. Obviously, the power is not reduced to idle. This merely is a gauge to judge and establish the point over the ground where an escape turn must be made.
For the unconcerned aviator bopping along through the mountains at cruise power setting, it is still necessary to maintain a conditioned reflex of maintaining a position where you can always turn to lowering terrain and never fly beyond the point of no return.
This must be a conditioned reflex rather than instinct, because instinct is often wrong in an airplane. For example, if you have ever experienced a spin, your first impression is that the airplane is pointing straight towards the ground while rotating. The Cessna 172, for example, has its nose 46 degrees below the horizon, only about halfway from the horizon to the vertical. Your instinct will be to raise the nose with back pressure. It's always worked before. But now you must use the conditioned reflex of relaxing the controls (or pushing the controls forward) to break the stall and then fly out of the resulting dive without exceeding the critical angle of attack (somewhere around 16-18 degrees).
Another example of the conditioned reflex is the forced landing procedure experienced at the beginning of the private pilot training. After several lessons, the flight instructor reaches out and pulls the power lever, stating something like, "You're engine just quit, proceed as you would in an actual emergency."
To begin, your first endeavors don't provide much satisfaction for yourself or the instructor. You try to pick out an area for a forced landing and next try to extend the glide to make it to that spot; however, without experience only luck will allow you to approach anywhere near your projected spot.
If you have an excellent flight instructor, someone who teaches the spot method of landing, it is easy to determine how far the airplane will glide. Using the spot method technique allows you to look at a windscreen mark during a glide and determine the spot on the ground where the airplane will glide. By mentally subscribing a line in an arc from this point, the area surrounding the airplane within which the airplane can be landed is defined.
The instructor continues this "conditioning," much as Pavlov conditioned his dogs, but hopefully without quite as much salivating. At some point during this process, your subconscious begins mentally picking out forced-landing areas. When the conditioning is complete, the instructor pulls the engine power and you, without really thinking or concentrating about it, head for a forced-landing spot. The spot may be ahead or behind the airplane, it doesn't really matter for your subconscious has already made the decision.

Box Canyon Turn 2

Until you have practiced the box canyon turn and understand the mechanics of and the ramifications of an unintentional stall close to the terrain, the best advice for escaping from a "tight," or rapidly rising terrain or the narrowing confines of a canyon, is to make a steep turn at a slow speed, using flaps if prudent.
What possible options are available for the course reversal maneuver to escape the precarious position?

Hammerhead Turn

Pilots, in all seriousness, have asked my advice about performing the hammerhead turn as an emergency procedure for getting out of a tight spot. There are several problems that immediately jump to mind, negating the possibility of performing the hammerhead turn.
First by way of definition, the hammerhead turn is an aerobatic maneuver where the airplane enters a vertical climb from maneuvering speed (or the recommended indicated airspeed for the aerobatic airplane involved). As the airplane slows, but before it encounters stall buffet, the pilot initiates the turn. For a left turn, the torque of the engine aids in making the turn. Application of left rudder is coordinated with the application of right aileron and forward movement of the control wheel (left rudder and left aileron used together causes the airplane to roll onto its back). When the airplane pivots to a nose-down position, back pressure is used to fly out of the resulting dive. Definitely it is best to avoid this maneuver in a "tight."
The airplane is usually at a dangerously low airspeed when the pilot arrives at the "tight." This precludes even thinking about performing the hammerhead maneuver. Even with plenty of airspeed, it would be stupid (as in not exhibiting common sense) to try the hammerhead.
The airplane used for mountain flying is probably not an aerobatic certified machine.

Wing Over

The wing over is more of a fun maneuver than an emergency escape maneuver. Usually the pilot pre-plans the wing over, allowing sufficient airspeed to transition from level flight to a climbing pitch attitude of about 40 degrees. During the increase in pitch, a coordinated bank is begun. The maximum pitch is reached after about a quarter turn (45 degrees of turn). At this point the back pressure is completely relaxed, but the bank continues to increase to 90 degrees. The bank is rolled out during the last quarter of the turn and back pressure is increased to arrest the descent. The airplane should arrive at the 180-degree turn point at the same altitude at which it began the maneuver.
Again, this is a maneuver that is intentionally performed for fun, rather than to escape during an emergency situation.
Steep Turn
The safest and perhaps the most commonly used method of course reversal is the steep turn. It is very similar to the box canyon turn.
The stall speed of an airplane increases as the square root of the wing load factor. In a 60-degree coordinated turn, regardless of airspeed, the airplane experiences a 2-g load factor. The square root of 2 is 1.41, so there is a 41 percent increase in stall speed.
Most pilots don't really care how to determine the radius of turn. By formula, the radius of a turn is equal to the velocity in true airspeed (knots) squared and then divided by a constant of 11.26 times the tangent of the bank angle in degrees.
The valid information this formula provides is the fact that the radius of turn can be shortened by either reducing the true airspeed, or by increasing the angle of bank. A combination of the two provides the greatest benefit.
The ratio of turn radius to an increase in airspeed at a constant bank varies as the square of the true airspeed. If the airplane doubles its speed, it will quadruple the distance traveled. So even if the airplane is going faster (twice as fast in this case), it still takes twice the amount of time to complete the turn around (four times further traveled).
What about using flaps during this steep turn? Definitely, use them as appropriate to the flight conditions. Flaps were invented to allow an airplane to increase its approach angle without an increase in airspeed. They work because lift and drag are directly proportional. If the lift is increased (by applying flaps to increase the camber of the wing), the drag is increased (and hence, no increase in airspeed).
For most airplanes the addition of flaps, up to half the total available, provides more lift than drag because the drag can be “subdued” with excess power.
At a high density altitude it may not be possible to use full flaps without intentionally losing altitude to maintain a safe airspeed. If a trade-off between altitude and airspeed cannot be made because of rapidly rising terrain, limit the use of the flaps to the extent that the airplane will maintain a constant altitude during the turn.
Remember too that flaps reduce the structural strength of the airplane. Many of the normal category airplanes are stressed for 3.8 gs (g = gravity unit). This is the limit-load factor that should not be exceeded. Okay, you say, what about the ultimate load factor, you know, that 50-percent safety factor built into the airplane? Shouldn't the airplane be capable of flying at 5.7 gs?
The correct response requires a definite and emphatically strong NO. For certification the airplane must be able to withstand the ultimate load factor for a period of fewer than 2 seconds without permanent deformation of the structure. More time than this at a load greater than the limit-load factor and the airplane may experience structural failure (that is, the wing breaks off).
Check the POH (pilots operating handbook) to determine the amount of reduction in structural strength with the application of flaps. The book may say: normal category 3.8 gs; flaps extended 2.2 gs (a 42 percent reduction).

Box Canyon Turn - Introduction

The box canyon turn varies from the steep turn in that it is either performed from level flight at such a slow airspeed that an unintentional stall is imminent, or some excess airspeed at the beginning of the maneuver allows the nose to be raised above the horizon prior to initiating the bank and the airspeed, during the turn, will be too slow to sustain level flight.
We have learned the airplane always stalls at the same critical angle of attack. When banking the airplane, the stall speed increases (remember? it increases as the square root of the wing load factor). Whenever the airplane is banked in a coordinated turn, it is balancing the centripetal force (horizontal lift component that causes the turn) and the centrifugal force (the force of the turn). The turn takes place because the centripetal force pulls the airplane towards the inside of the turn.
Without a compensating increase in the amount of total lift during a turn, the airplane will lose altitude. The total lift (lift) is divided between a vector force that sustains the weight of the airplane and its contents (weight). The portion of lift that is directed sideward (centripetal force) causes the turn. The centrifugal force acts towards the outside of the turn.
To maintain level flight while turning it is necessary to increase back pressure (more lift equals an increase in angle of attack). This increases the load factor and stall speed.
Some pilots get into trouble with the box canyon turn without realizing it because they have been "conditioned" to maintain level flight when performing steep turns.

Box Canyon Turn -Procedure from Cruise Flight

The first time a pilot has to perform a box canyon turn in a true life situation, he may feel like the lady who climbs on a stool to avoid a mouse scampering across the floor. A little scream to get the adrenaline flowing wouldn’t hurt either.
The box canyon turn could be described as a combination of the steep turn and wing over (when entered at or near cruise airspeed). The nose is raised above the horizon, but nowhere near the 40-degree attitude of the wing over. About five to 20 degrees is about right, depending on the airspeed.
This does two things for you. First it trades airspeed for altitude and second, it slows the airspeed for a smaller radius of turn.
At the same time, full power is added and full flaps (providing the airspeed is within the flap operating range) are applied while beginning the bank. The bank will be a minimum of 60 degrees and may approach 90 degrees.
To insure that the g-load factor is not exceeded during the steep bank it is necessary to relax the backpressure once the bank passes about 45 degrees. The back pressure is not increased again until the bank passes through about 45 degrees toward zero degrees during the rollout.
Initiate the turn - the procedure requires coordination to accomplish all items at the same time:
Increase pitch attitude
Increase power
Begin a bank
Apply full flaps
At approximately 45 degrees of bank increasing toward 60-90 degrees:
Relax back pressure from the control wheel
Recovery - at approximately 45 degrees of bank, decreasing from 60-90 degrees:
Increase back pressure on the control wheel to arrest any loss of altitude.
When the airplane is in a position that allows, reduce flaps to one half
Box Canyon Turn -Procedure from Climbing Flight
When operating near cruise airspeed the box canyon turn was described as a combination of the steep turn and wing over where the nose was raised above the horizon.
Hopefully, the airspeed is near the best rate-of-climb speed or best angle-of-climb speed. This is usually a critical situation because the airspeed will probably be slower than Vy or Vx due to the “short-arm” effect.
While applying full power and full flaps, a bank is established at a minimum of 60 degrees. Again the bank may approach 90 degrees.
Previously we stated that the back pressure was relaxed to insure that the g-load factor was not exceeded. This is not as much of a problem at low speed, but it still exists. At the slow speed the airplane will probably stall before it exceeds the structural limitations. The main reason for relaxing the back pressure now is so the airplane does not stall. The back pressure is not increased again until the bank passes through about 45 degrees toward zero degrees during the rollout.
Initiate the turn - the procedure requires coordination to accomplish all items at the same time:
Maintain pitch attitude initially
Increase power
Begin a bank
Apply full flaps
At approximately 30 degrees of bank, increasing toward 60-90 degrees:
Relax back pressure from the control wheel
The pitch attitude will fall below the horizon
Recovery - at approximately 30 degrees of bank, decreasing toward zero degrees:
Increase back pressure on the control wheel
Reduce flaps to one half

Natural Horizon

The natural horizon is used to teach flying by outside visual reference. An instructor demonstrates a climb attitude at the best rate-of-climb airspeed. The student mimics this attitude. The airspeed indicator can be covered and the student, by noticing the pitch attitude in relation to the horizon (where the horizon intersects the side of the nose cowling), is able to fly at the best rate-of-climb airspeed within plus or minus one knot. Learning the “climb attitude” can provide for a very accurate climb speed, without looking at the airspeed indicator.
The instructor also demonstrates where is the nose in relation to the horizon in level flight, where are the wings in relation to the horizon in level flight, and where is the nose in relation to the horizon in a steep turn (left and right turns).
This natural horizon is easy to use in the flatlands as a reference for basic attitude flying. In the mountains, the natural horizon may disappear. By visualizing a horizon, basic attitude flying can still be maintained. The base of the mountains, at least six to eight miles away, represents the natural horizon.
What if the airplane is closer than the six to eight miles? Visualization must be used. Perhaps the mountains at least six to eight miles in the distance are visible out the side window. Project the same horizon visually to the front of the airplane.

The box canyon turn is an emergency procedure. It is best to practice it with an experienced instructor prior to the time when it becomes necessary as a life-saving maneuver.
Without practice it is very easy to get into an accelerated stall condition that will exacerbate the original situation.
Caveat
You must exercise caution in using full flaps during the practice of the box canyon turn and for drainage searches because of the possibility of the flaps failing in the extended position. For practice you may want to restrict the use of flaps because of the real possibility of the flaps failing to retract. It is possible to demonstrate and learn the box canyon turn without full flaps where the same technique, using full flaps, is applicable to a real "tight" or emergency condition.

CROSSING RIDGES

Without experience the visual aspects of mountainous country can be very deceptive. It is difficult to be able to look out the windshield and say with any certainty whether or not you are higher than the ridge you are approaching.
In approaching and crossing ridges, the novice pilot is well advised to start out by maintaining a 2,000-foot clearance over both mountains and valleys.

When a mountain ridge is approached from the upwind side there is usually a cushion of air to help you up and over the ridge, providing the wind is blowing somewhat perpendicular to the mountain. Once the wind hits about 20 knots or more at mountaintop level there will be turbulence associated with any downdrafts on the lee side, but this depends a great extent on the stability of the air. Under stable conditions, there may only be a laminar flow with smooth down air on the downwind side of the mountain. And, too, the updraft generated on the upside of the mountain may extend beyond the mountaintop to form updrafts on the downwind side (above ridge level).


If a mountain ridge is approached from the downwind or lee side, the pilot runs the risk of encountering a downdraft and turbulence. When the airplane is flown perpendicular to the mountain there is also a possibility of encountering a downdraft that could cause the airplane to impact the mountain.
I am not implying that there will not be sufficient room to turn away from the ridge if it is approached "head on, but when you approach the mountain at an angel, it will permit a safer retreat with less stress on the aircraft should severe turbulence or downdrafts be experienced.

Remember that in addition to the load factor induced by the turbulence, the load factor also increases during a banked turn. These are not separate forces, but add together for a total force on the airplane. Also, the stall speed increases as the square root of the wing load factor. In a 60-degree bank, the load factor is 2 Gs (gravity units). The square root of 2 is 1.41 or a 41 percent increase in stall speed.
For this reason, ridges are always approached at an angle, a 45-degree angle is recommended by most instructors. Even when the stability of the air is such that the 45-degree angle approach isn't necessary, do it anyway (or at least remain in a position to turn to lowering terrain). The reason for this recommendation is because Mother Nature can provide some surprises.
As an example of such a surprise, consider the pilot who departs Aspen, Colorado with a right downwind from runway 33. He follows the Roaring Fork River to Independence Pass. Knowing he is in an area of prevailing westerly winds aloft, the pilot assumes there will be a cushion of air to help him up and over the pass. But, Mother Nature may have stalled a high pressure area over the Upper Arkansas River Valley near Leadville.
This high-pressure area is a mountain of air that is creating an instability in the atmosphere. In regaining stability, it subsides, that is, the air flows down the mountain toward areas of lesser pressure. This might occur in the vicinity of Independence Pass and the subsidence can overpower the westerly winds aloft, presenting a downdraft where an updraft is expected. So, for safety sake, remain in a position to turn to lower terrain!

EXITING DOWNDRAFTS

Whenever you are caught in a downdraft, it is wise to immediately turn toward lowering terrain. Compute the rate of climb for the density altitude that you are flying. Perhaps the POH gives a value of 400 fpm rate of climb at 8,000-feet density altitude. In a strong or sustained downdraft, if the descent rate, after transitioning to the best rate-of-climb airspeed, is greater than your computed best rate of climb, transition to cruise speed to escape the downdraft. If turbulence is a concern, accelerate to the maneuvering speed.
Perhaps you are descending at 500 feet per minute and transition to cruise airspeed. The airplane may now be descending at 1,100 feet per minute. Accept this temporary increase in descent rate. Although the airplane is descending faster, it will exit the area of the downdraft in lesser time, providing an altitude loss that will be less than fighting the downdraft at the best rate of climb speed.

Although we (mountain instructors) advocate that it is best to approach mountain ridges at a 45-degree angle, it is not necessary to do so when you are four or five miles away from the mountains. Wait until you are within about 1/2 mile to 1/4 mile from the ridge, then maneuver to approach at the 45-degree angle. If you are crossing a series of ridges, you might consider crossing one ridge to the right and the next to the left and so on, to stay somewhat on course.

If you elect to make a flight without maintaining the 2,000-foot clearance altitude above the ridges, you can determine if you have sufficient altitude to cross the ridge by picking two spots. The first spot is whatever you can see over the ridgeline. The other spot is an arbitrary point. In the example to the right, the first point is the bottom of the yellow arc and the arbitrary point is the top of the yellow arc.
As you get closer to the ridge the spacing between the two spots will increase if you are higher than the ridge (the pick arc). If the distance decreases, there is not sufficient altitude to cross the ridge.


I don't like this method of determining sufficient ridge clearance. As an instructor I found my students developing "tunnel vision," where they concentrated only on the points and became unaware of other things going on in and around the airplane.
It is easier (and better) to just be aware of the terrain. If you can see more and more of the terrain on the other side of the ridge, you are higher than the ridge and can probably continue. If the terrain on the other side of the ridge is disappearing, get out. Turn around, gain more and try again.
If this technique causes you worry or concern rather than challenging your ability, don't do it. Fly over the ridge with 2,000-foot terrain clearance.


The wind is from the west-northwest (left rear of the airplane). The airplane is being flown up the right (south) side of the canyon to be in an area of updraft. Can the pilot make a commitment to cross the ridgeline at this point? NO.

Once the pilot maneuvers to a position (maintain the 45-degree angle approach) where the throttle can be reduced to idle and the airplane has sufficient altitude to dive and hit the top of the ridgeline, the pilot can make the commitment to cross the ridge. I'm not suggesting that it is proper procedure to reduce the throttle to idle -- this is how you just the proper position for making a commitment.
If you have gotten to this position without encountering a downdraft, any downdraft experienced can be overcome by lowering the nose slightly to maintain airspeed while crossing the ridge. Once you have made the commitment it is a good idea to fly toward lowering terrain. This "safe ridge crossing" technique may be used whether approaching the ridge from

upwind or downwind.

A word of caution. If you are trying to cross an extended plateau as opposed to the ridgeline, this rule will not work. In this case you will need additional altitude and you must remain in a position to turn to lower terrain................Sky wings