TM 1-1510-223-10 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. B-1.  AIRSPEED TERMINOLOGY. V_fe Maximum  flap extended CAS Calibrated airspeed is indi- speed is the highest speed cated airspeed corrected for permissible with wing flaps position and instrument error. a prescribed extended posi- tion. GS Ground speed is the speed of  V_le Maximum  landing  gear the aircraft relative to the extended speed is the maxi- ground. mum speed at which an air- craft can be safely flown with lAS Indicated airspeed is the the landing gear extended. speed as shown on the air- . no instrument error. V_lo Maximum landing gear oper- ating speed is the maximum KT Knots. speed at which the landing gear can be safely extended or M Mach number.  The ratio of retracted. true airspeed to the speed of sound. V_mca The minimum flight speed at which the aircraft is direction- M_mo Maximum  operating Mach ally controllable as deter- number. mined in accordance with TAS True airspeed is calibrated Federal Aviation Regulations. airspeed corrected for alti- Aircraft Certification condi- tude, temperature, pressure, tions include one engine and compressibility effects. becoming inoperative and propeller feathered; up to a 5° V₁ Takeoff decision speed bank toward the operative engine; takeoff power on V₅₀ Takeoff safety speed is the operative engine; landing gear speed at 50 feet AGL (35 feet up; flaps up, and most rear- AGL with one engine inoper- ward CG.  This speed has ative). been demonstrated to provide V_a Maneuvering speed is the satisfactory control above maximum speed at which power off stall speed (which application of full available varies with weight, configura- aerodynamic control will not tion, and flight attitude). overstress the aircraft. V_mo Maximum  operating limit V_enr One  engine  inoperative speed. enroute climb speed. V_r Rotation speed. V_f Design flap speed is the high-  V_ref The indicated airspeed that est speed permissible at the aircraft should be at when which wing flaps may be 50 feet above the runway in actuated. the landing configuration. B-1