Drafted — not technically validated
Record revision 1 · The control and performance concept, the crosscheck, the illusions of spatial disorientation, holding, and the fixes and altitudes of an instrument approach.
Definitions are quoted or closely paraphrased from the source named with each word. Meanings change between editions and theatres; the brief and the current publications take precedence.
The words of instrument flight
These are the words of flying without looking outside: how the instruments are grouped and scanned, the illusions that make a pilot doubt them, holding, and the fixes and altitudes of an instrument approach. They come from the Air Force’s instrument flight procedures manual, which writes for fixed- and rotary-wing pilots. [1] The illusions are from the FAA’s Aeronautical Information Manual, which all US airspace users share. [2]
PAR, TACAN and IFR are in the airfield and ATC terms, and radials and station passage in the navigation terms.
22 terms
- ASR
Airport surveillance radar approach. A radar approach giving course and range but no glidepath, so a non-precision approach flown to a minimum descent altitude. On request the controller gives recommended altitudes each mile on final.
Source: [1] AFMAN 11-217 Volume 1, pp. 220–221
- Control and performance concept
Attitude instrument flying by setting an attitude and power on the control instruments (attitude indicator and power gauges), trimming, then checking the result on the performance instruments (altimeter, airspeed, vertical velocity, heading, angle of attack, turn and slip) and correcting attitude and power if the result is off.
Source: [1] AFMAN 11-217 Volume 1, pp. 12–13
- Coriolis illusion
The illusion of rotating in a different axis after an abrupt head movement during a prolonged constant-rate turn. The most overwhelming illusion in flight; avoided by not moving the head suddenly in long turns under IFR.
Source: [2] Aeronautical Information Manual, ¶8-1-5
- Crosscheck
The division of attention between the control and performance instruments, reading them and correcting what is off. It runs like a wheel, with the attitude indicator as the hub and the other instruments as spokes, out and back to the hub each time.
Source: [1] AFMAN 11-217 Volume 1, p. 14
- Decision altitude
DA, or decision height (DH). The altitude on a precision approach at which the missed approach is flown if the runway environment is not in sight; a precision approach has no separate missed approach point.
Source: [1] AFMAN 11-217 Volume 1, pp. 208, 249
- Diverse departure
A departure from a runway where no obstacle penetrates a 40:1 surface from the departure end, so an aircraft climbing at 200 ft per nautical mile may turn any direction, and no obstacle departure procedure is needed.
Source: [1] AFMAN 11-217 Volume 1, p. 128
- EFC
Expect further clearance time. The time ATC gives a holding aircraft as its best estimate of when it will be cleared on. Ask for one whenever told to hold without it.
Source: [1] AFMAN 11-217 Volume 1, p. 152
- Final approach fix
FAF. Where the final approach begins, shown as a Maltese cross in the profile view with its crossing altitude. Normally crossed at approach speed in the landing configuration.
Source: [1] AFMAN 11-217 Volume 1, p. 206
- Graveyard spiral
In a prolonged coordinated turn the inner ear stops sensing the turn; seeing altitude lost, the pilot thinks the wings are level in a descent and pulls back, tightening the spiral and losing more altitude.
Source: [2] Aeronautical Information Manual, ¶8-1-5
- Holding pattern
A racetrack flown at a fix while awaiting further clearance, inbound on the holding course to the fix, then 180° turns. Standard turns are to the right and nonstandard to the left; the inbound leg is 1 minute at or below 14,000 ft MSL and 1½ minutes above.
Source: [1] AFMAN 11-217 Volume 1, p. 151
- Minimum descent altitude
MDA. The lowest altitude on a non-precision approach. Stay at or above it until the runway environment is in sight and you are in position to land, or go missed at the missed approach point.
Source: [1] AFMAN 11-217 Volume 1, pp. 206, 209
- Minimum safe altitude
An emergency altitude with at least 1,000 ft of obstacle clearance around the facility an approach is based on. A minimum sector altitude covers 25 NM; an emergency safe altitude, normally published only for military procedures, covers 100 NM, with 2,000 ft of clearance in designated mountainous areas. Neither guarantees navigation aid reception.
Source: [1] AFMAN 11-217 Volume 1, p. 105
- Missed approach point
MAP. The point on a non-precision approach at which a missed approach is flown if the runway environment is not in sight or a safe landing cannot be made. For a straight-in approach it is no farther from the final approach fix than the threshold.
Source: [1] AFMAN 11-217 Volume 1, pp. 208, 249
- No-gyro approach
A radar approach for an aircraft whose heading indicator has failed. The controller says "turn right", "turn left" and "stop turn"; turns are about standard rate (not over 30° of bank) until the controller calls for half-standard rate on final.
Source: [1] AFMAN 11-217 Volume 1, p. 222
- Penetration turn
The turn back to the inbound course during a high-altitude teardrop approach, flown in the published direction, normally at 30° of bank. If no turn altitude is published, start it after descending half the height between the initial and final approach fix altitudes.
Source: [1] AFMAN 11-217 Volume 1, p. 171
- Somatogravic illusion
Rapid acceleration, as on takeoff, feels like a nose-up attitude and the pilot pushes nose low; rapid deceleration has the opposite effect, toward a nose-up or stalled attitude.
Source: [2] Aeronautical Information Manual, ¶8-1-5
- Spatial disorientation
Mistaking the aircraft's attitude or motion because of illusions of motion and position created by complex motions, forces and certain visual scenes. It can be prevented only by visual reference to reliable, fixed points on the ground or to the flight instruments.
Source: [2] Aeronautical Information Manual, ¶8-1-5
- Stepdown fix
A fix between the final approach fix and the missed approach point on some non-precision approaches, normally to clear an obstacle inside the final approach fix. Do not descend below its altitude until it is identified.
Source: [1] AFMAN 11-217 Volume 1, p. 206
- The leans
The illusion of banking the opposite way after an abrupt roll out of a bank that was entered too slowly for the inner ear to sense. The pilot rolls back into the original bank, or leans toward the false vertical.
Source: [2] Aeronautical Information Manual, ¶8-1-5
- Touchdown zone elevation
TDZE. The highest point in the first 3,000 ft of the landing surface. Field elevation is the highest point of any usable landing surface.
Source: [1] AFMAN 11-217 Volume 1, p. 105
- Unusual attitude
An aircraft attitude entered inadvertently, from turbulence, channelized attention, instrument failure, inattention, spatial disorientation, a lost wingman or going from visual to instrument conditions.
Source: [1] AFMAN 11-217 Volume 1, p. 26
- Visual descent point
VDP. A point on a non-precision straight-in final from which a normal descent of about 3° from the minimum descent altitude to touchdown can begin, if the runway environment is in sight. Shown as a "V" in the profile view.
Source: [1] AFMAN 11-217 Volume 1, pp. 206–207
Sources
- AFMAN 11-217 Volume 1, Instrument Flight Procedures. US Air Force (copy hosted by code7700.com), 22 October 2010. https://www.code7700.com/pdfs/usaf/afman11-217v1.pdf (accessed 2026-11-02). By printed page. Superseded by the consolidated AFMAN 11-217 of 10 June 2019, which could not be retrieved for this revision.
- Aeronautical Information Manual, chapter 8, section 1: Fitness for Flight. Federal Aviation Administration. https://www.faa.gov/air_traffic/publications/atpubs/aim_html/chap8_section_1.html (accessed 2026-11-02). ¶8-1-5, Illusions in Flight.