Drafted — not technically validated
Record revision 2 · Lift, drag, load factor, corner speed, Mach number and the afterburner for the jet, and ETL, vortex ring state and autorotation for the rotor.
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 flight
These are the words of how aircraft fly: the wing and angle of attack, drag, control, turns and energy, and the rotor. Military training texts come first, from the Navy’s aerodynamics books and its T-45 fighter syllabus to the Army’s fundamentals of flight for helicopter crews. [1] [2] [3] [4]
The FAA’s handbooks describe the same physics for civil pilots and are cited where they state a point more directly, above all for helicopter hazards. [5] [6] [7] Angle of attack itself is in the joint terms. The Navy’s aerodynamics book also gives the words of speed and the jet engine: Mach number, the regimes of flight, the afterburner and the turboprop. [1]
49 terms
- Adverse yaw
Yaw opposite to the direction of bank when rolling, caused by the differential drag and the slightly different speeds of the two wings. Coordinated rudder counters it.
Source: [5] FAA-H-8083-25C, p. 6-3; [6] FAA-H-8083-3C, p. 5-8
- Afterburner
An additional combustion area aft of the turbine section of a turbojet, with fuel nozzles and flameholders, that burns fuel in the engine's large excess of air. It adds only 10 to 20 percent to the engine's weight but 40 to 60 percent to its static sea-level thrust, at least doubling its specific fuel consumption, so its use is limited to short periods.
The engine needs a variable exhaust nozzle that opens as the afterburner lights. The afterburner is most common on interceptor, fighter and other high-speed aircraft. [1]
Source: [1] NAVWEPS 00-80T-80, pp. 129–131
- Angle of incidence
The angle between the chord line of a rotor blade and the rotor hub, usually called blade pitch angle. For a fixed airfoil such as a fin, the angle between its chord line and a reference plane of the aircraft.
Source: [7] FAA-H-8083-21B, p. 2-8
- Antitorque pedals
The helicopter pilot's foot controls for the tail rotor. They change the pitch, and so the thrust, of the tail rotor blades, which controls heading in a hover.
Source: [7] FAA-H-8083-21B, p. 3-4
- Autorotation
Descent with the rotor turned by the upward flow of air instead of the engine. After an engine failure the pilot lowers the collective at once to keep the rotor turning.
In the autorotating rotor the middle of the blade, normally 25 to 70 percent of the radius, is the driving region; the outer 30 percent is driven, held back by drag; the inner 25 percent is stalled. [7]
Source: [7] FAA-H-8083-21B, pp. 11-2, 2-26
- Blowback
The nose-up pitch, and tendency to roll right, as a helicopter accelerates through translational lift, caused by dissymmetry of lift and transverse flow. Forward cyclic holds the rotor disk attitude.
Source: [7] FAA-H-8083-21B, p. 2-20
- Camber
The maximum distance between an airfoil's mean camber line, which runs midway between its upper and lower surfaces, and its chord line.
Source: [2] Preflight Course (API) Module/Unit 2, p. 33
- Chord line
The straight line through the leading edge and the trailing edge of an airfoil.
Source: [2] Preflight Course (API) Module/Unit 2, p. 33
- Coaxial rotor
A pair of rotors on the same shaft turning in opposite directions. Their torques cancel, so no tail rotor is needed.
Source: [7] FAA-H-8083-21B, pp. 1-4, 4-6; [4] FM 3-04.203, ¶1-78
- Collective
The helicopter control, at the pilot's left side, that changes the pitch of all the main rotor blades at once and by the same amount, and so the rotor's thrust.
Source: [7] FAA-H-8083-21B, p. 3-2; [1] NAVWEPS 00-80T-80, p. 321
- Coning
The upward bend of rotor blades as they carry the helicopter's weight, balanced by centrifugal force. Low rotor rpm or high weight increases it; excessive coning stresses the rotor and reduces lift.
- Corner speed
The speed where the stall boundary meets the limit load, giving the best instantaneous turn. The civil handbooks call it the maneuvering speed, VA, the maximum speed at which the positive design load limit can be imposed.
See also corner airspeed in the air combat terms.
Source: [6] FAA-H-8083-3C, p. 5-19
- Critical angle of attack
The angle of attack at which the lift coefficient reaches its maximum, CLmax. Beyond it the airflow is unable to adhere to the upper surface, lift falls away and the wing stalls.
Source: [2] Preflight Course (API) Module/Unit 2, p. 50; [1] NAVWEPS 00-80T-80, p. 23
- Cyclic
The helicopter control that changes each blade's pitch as it goes round, tilting the rotor disk, and its thrust, in the direction the stick moves.
Source: [7] FAA-H-8083-21B, pp. 3-3–3-4; [1] NAVWEPS 00-80T-80, p. 321
- Dissymmetry of lift
The difference in lift between the advancing and retreating halves of a rotor disk in forward flight. Blade flapping is the primary means of compensating for it.
Source: [7] FAA-H-8083-21B, p. 2-20; [4] FM 3-04.203, ¶1-32–1-33
- Dynamic rollover
A roll about a skid or wheel pinned to the ground that carries a helicopter past the point where cyclic can stop it, about 5 to 8 degrees. Quickly reducing collective is the most effective way to stop it.
Source: [7] FAA-H-8083-21B, p. 11-12
- Effective translational lift (ETL)
The point, between about 16 and 24 knots of forward speed, where the rotor disk completely outruns the recirculation of its own vortices and the same blade pitch gives more lift.
Source: [7] FAA-H-8083-21B, pp. 2-21–2-24; [4] FM 3-04.203, ¶1-24
- Energy height (ES)
ES = h + V² ÷ 2g: altitude plus the altitude the airspeed could ideally buy in a zoom, a single measure of an aircraft's total energy.
Source: [6] FAA-H-8083-3C, pp. 4-7–4-8
- Excess thrust
Thrust available minus thrust required. Positive excess thrust causes a climb, an acceleration, or both, depending on angle of attack.
Source: [2] Preflight Course (API) Module/Unit 2, pp. 60–63
- Flapping
The up and down movement of rotor blades, about a hinge in a fully articulated rotor or as a unit in a semirigid one. It is the primary means of compensating for dissymmetry of lift.
- Fully articulated rotor
A rotor in which each blade can flap, lead and lag, and feather independently of the others. It is found on helicopters with more than two main rotor blades.
Source: [7] FAA-H-8083-21B, pp. 4-4–4-5
- Ground effect
The surface's interference with the airflow around a wing flying within about one wingspan of it, which reduces induced drag. For a helicopter, the increase in rotor efficiency within about one rotor diameter of the surface, so a hover in ground effect takes less power.
Source: [5] FAA-H-8083-25C, pp. 5-11–5-12; [7] FAA-H-8083-21B, p. 2-12
- Ground resonance
A destructive vibration of a helicopter on the ground, at certain rotor speeds, when an out-of-balance articulated rotor drives the airframe at its natural frequency. It can destroy the helicopter in seconds.
Source: [7] FAA-H-8083-21B, p. 11-11
- Gyroscopic precession
The deflection of a spinning object when a force is applied to it, appearing about 90° later in the direction of rotation. It is why rotor controls act 90° ahead of the response.
Source: [7] FAA-H-8083-21B, p. 2-17
- Height/velocity diagram (H/V)
The chart of combinations of height above the ground and airspeed from which a helicopter can complete a landing after an engine failure. Its shaded areas are to be avoided.
Source: [7] FAA-H-8083-21B, pp. 7-2–7-3; [1] NAVWEPS 00-80T-80, p. 409
- Induced drag
The portion of total drag associated with the production of lift. In level flight it varies inversely with the square of the airspeed, so it is greatest when slow.
Source: [2] Preflight Course (API) Module/Unit 2, pp. 55–56; [5] FAA-H-8083-25C, pp. 5-7–5-8
- Induced flow
The downward flow of air through a rotor disk. In a hover it is the main cause of the high power a helicopter needs.
Source: [7] FAA-H-8083-21B, p. 2-8; [4] FM 3-04.203, ¶1-88–1-89
- L/Dmax
The best lift-to-drag ratio. The angle of attack that gives it produces the minimum total drag.
Source: [2] Preflight Course (API) Module/Unit 2, pp. 57–58
- Lift-limit and load-limit pull
The two maximum-performance pulls. Below corner speed the pull is lift-limited, flown to the buffet (19 to 21 units in the T-45); above it the pull is load-limited, flown to the G limit.
Source: [3] CNATRA P-1289 (Rev. 01-16), p. 4-3
- Load factor
The ratio of lift to weight, felt as G. In a level, coordinated turn it is 1 ÷ cos(bank), and the stall speed in the turn is the wings-level stall speed times its square root.
Source: [1] NAVWEPS 00-80T-80, p. 37
- Loss of tail rotor effectiveness (LTE)
An uncommanded, rapid yaw towards the advancing blade that does not stop of its own accord. It comes from aerodynamic interaction between the main and tail rotors, not a mechanical failure.
Source: [7] FAA-H-8083-21B, p. 11-18
- Mach number (M)
The ratio of the true airspeed to the speed of sound. All compressibility effects depend on it.
The speed of sound at standard sea level is 661 knots, and it falls with temperature. [1]
Source: [1] NAVWEPS 00-80T-80, p. 202
- Mast bumping
The rotor hub striking the mast when flapping exceeds its design limit, a hazard of semirigid (teetering) rotors that can shear the mast. Low G makes it likely.
Source: [7] FAA-H-8083-21B, pp. 4-3, 11-14–11-15
- Parasite drag
Drag that is not associated with the production of lift, made up of form drag, friction drag and interference drag. It varies directly with velocity squared.
Source: [2] Preflight Course (API) Module/Unit 2, pp. 52–54
- Retreating blade stall
Stall of a helicopter's retreating blade at high forward speed, from its high angle of attack and slow relative wind. The first step in recovery is usually to reduce collective.
Source: [7] FAA-H-8083-21B, pp. 2-20, 11-11
- Rigid rotor
A rotor with no flapping or lead-lag hinges; the blades bend to allow those motions. It is very responsive and usually not susceptible to mast bumping.
Source: [7] FAA-H-8083-21B, pp. 4-3–4-4
- Rotor stall
The stall of the whole rotor when rotor rpm falls too low, unlike retreating blade stall, which affects only part of the retreating side at high speed.
Source: [7] FAA-H-8083-21B, pp. 11-15–11-16
- Semirigid rotor
A rotor, usually two-bladed, whose blades are rigidly fixed to a hub that teeters on the mast, so they flap together as a unit. The blades feather but have no lead-lag hinge.
Source: [7] FAA-H-8083-21B, p. 4-2
- Stabilator
A one-piece moving horizontal tail used instead of a stabilizer and elevator, as on the F/A-18 and F-15.
Source: [2] Preflight Course (API) Module/Unit 2, p. 68
- Subsonic
The regime of flight below about Mach 0.75, in which the airflow on all parts of the aircraft is most likely subsonic.
Source: [1] NAVWEPS 00-80T-80, p. 204
- Supersonic
The regime of flight from about Mach 1.20 to 5.00, with definite supersonic flow on all parts of the aircraft. Above Mach 5.00 is hypersonic.
Source: [1] NAVWEPS 00-80T-80, p. 204
- Tandem rotor
A helicopter layout with two large main rotors, one ahead of the other, turning in opposite directions instead of a single main rotor and a tail rotor.
- Translating tendency
The sideways drift of a hovering single-rotor helicopter in the direction of its tail rotor thrust.
Source: [7] FAA-H-8083-21B, p. 2-15
- Translational lift
The improved rotor efficiency that comes with forward speed or wind, as more fresh air enters the disk and induced flow falls; the same pitch then gives more lift.
- Transonic
The regime of flight from about Mach 0.75 to 1.20, in which the flow over the aircraft is likely to be partly subsonic and partly supersonic.
Source: [1] NAVWEPS 00-80T-80, p. 204
- Transverse flow effect
The difference in lift between the front and rear of a rotor disk in forward flight, as induced flow falls at the front and rises at the rear. It shows as vibration around 12 to 15 knots and a roll to the right.
Source: [7] FAA-H-8083-21B, pp. 2-23–2-24
- Turboprop
A gas turbine that drives a propeller through extra turbine stages, which extract most of the exhaust gas energy as shaft power. Working on a much greater mass flow, it is more efficient than the turbojet in subsonic flight; jet thrust gives only 15 to 25 percent of its total thrust.
Source: [1] NAVWEPS 00-80T-80, p. 131
- Units (AOA)
How the T-45 and other Navy trainers display angle of attack, a type-specific scale rather than degrees of chord-line angle. The T-45 reaches its maximum lift coefficient at 21 units, in heavy buffet.
Source: [3] CNATRA P-1289 (Rev. 01-16), pp. 4-1–4-3
- Vortex ring state
Also called settling with power: a vertical or nearly vertical descent of at least 300 feet per minute, with the rotor using some engine power and horizontal speed below ETL, in which the rotor settles into its own downwash. Adding power makes it worse.
Source: [7] FAA-H-8083-21B, p. 11-10
Sources
- NAVWEPS 00-80T-80, Aerodynamics for Naval Aviators. H. H. Hurt, Jr., Office of the Chief of Naval Operations, Aviation Training Division (hosted by the FAA), Revised January 1965. https://www.faa.gov/sites/faa.gov/files/regulations_policies/handbooks_manuals/aviation/00-80T-80.pdf (accessed 2026-10-25).
- Preflight Course (API) Module/Unit 2, Fundamentals of Aerodynamics, Trainee Guide Q-9B-0020L. Naval Aviation Schools Command, Change 1, April 2017. https://www.cnatra.navy.mil/training/assets/media/aerodynamics/aero-trainee-guide.pdf (accessed 2026-10-25).
- CNATRA P-1289 (Rev. 01-16), Flight Training Instruction, Basic Fighter Maneuvering (1v1), Section Engaged Maneuvering (2v1), T-45. Naval Air Training Command, Revision 3 of 7 January 2016, Change 1 of 3 March 2021. https://www.cnatra.navy.mil/local/docs/pat-pubs/P-1289.pdf (accessed 2026-10-24).
- FM 3-04.203, Fundamentals of Flight. Headquarters, Department of the Army, 7 May 2007. https://irp.fas.org/doddir/army/fm3-04-203.pdf (accessed 2026-10-25). Cited by paragraph.
- FAA-H-8083-25C, Pilot's Handbook of Aeronautical Knowledge. Federal Aviation Administration, 2023. https://www.faa.gov/sites/faa.gov/files/07_phak_ch5_0.pdf (accessed 2026-10-25). Chapter 5, Aerodynamics of Flight, and chapter 6, Flight Controls.
- FAA-H-8083-3C, Airplane Flying Handbook. Federal Aviation Administration, 2021. https://www.faa.gov/sites/faa.gov/files/regulations_policies/handbooks_manuals/aviation/airplane_handbook/06_afh_ch5.pdf (accessed 2026-10-25). Chapter 4, Energy Management, and chapter 5, Maintaining Aircraft Control.
- FAA-H-8083-21B, Helicopter Flying Handbook. Federal Aviation Administration, 2019. https://www.faa.gov/sites/faa.gov/files/regulations_policies/handbooks_manuals/aviation/helicopter_flying_handbook/hfh_ch02.pdf (accessed 2026-10-25). Chapter 1, Introduction to the Helicopter; 2, Aerodynamics of Flight; 3, Helicopter Flight Controls; 4, Helicopter Components, Sections, and Systems; 7, Helicopter Performance; 11, Helicopter Emergencies and Hazards. Each chapter is its own PDF on faa.gov.