TM 55-1510-222-10
APPENDIX B
ABBREVIATIONS AND TERMS
For the purpose of this manual, the following abbreviations and terms apply. See appropriate technical manuals
for additional terms and abbreviations.
AIRSPEED TERMINOLOGY.
CAS
Calibrated airspeed is indicated airspeed corrected for position and instrument error.
FT/MIN
Feet per minute.
GS
Ground speed, though not an airspeed, is directly calculable from true airspeed if the true wind
speed and direction are known.
IAS
Indicated airspeed is the speed as shown on the airspeed indicator and assumes no
error.
KT
Knots.
Mmo
Maximum operating Mach number.
TAS
True airspeed is calibrated airspeed corrected for temperature, pressure, and compressibility
effects.
V1
Takeoff decision speed (V, = VR)
V2
Takeoff safety speed is the speed at 50 feet AGL (35 feet AGL with one engine inoperative)
Va
Maneuvering speed is the maximum speed at which application of full available aerodynamic
control will not overstress the aircraft.
Vf
Design flap speed is the highest speed permissible at which wing flaps may be actuated.
Vfc
Maximum flap extended speed is the highest speed permissible with wing flaps in a prescribed
extended position.
Vic
Maximum landing gear extended speed is the maximum speed at which an aircraft can be safely
flown with the landing gear extended.
Vlo.
Maximum landing gear operating speed is the maximum speed at which the landing gear can be
safely extended or retracted.
Vlof
Lift off speed (takeoff airspeed).
Vmca
The minimum flight speed at which the aircraft is directional controllable as deter- mined in
accordance with Federal Aviation Regulations. Aircraft Certification conditions include one
engine becoming inoperative and windmilling; a 5° bank towards the operative engine; takeoff
power on operative engine; landing gear up; flaps up; and most rearward CG. This speed has
been demonstrated to provide satisfactory control above power off stall speed (which varies with
weight, configuration, and flight attitude).
Vmo
Maximum operating limit speed.
Vnc
Never exceed speed.
B-1
