Take-off Rated Thrust (TRT)
- the maximum allowable thrust (determined by fan speed, N1).
- varies with pressure altitude,
ram air temperature,
and bleed air usage. - operation of TRT is limited to 5 minutes.
Maximum Continuous Thrust
- the maximum allowable thrust (determined by fan speed, N1) that may be used without a time limitation.
- varies with pressure altitude, ram air temperature & bleed air usage
Runway Available
runway length minus any unusable portion of the runway such as the aircraft lineup distance or barriers on or above the runway
Runway Length
the paved surface length excluding any overrun
Critical Engine Failure Speed
the speed at which one engine can fail and the same distance is required to either continue to accelerate to lift-off speed, or abort and decelerate to a full stop
Critical Field Length
- the total length of the runway required to accelerate on all engines to critical engine failure speed, experience an engine failure, then continue to lift-off or stop
- used during takeoff planning together with the climbout data to determine maximum gross weight for a safe takeoff and climbout
- for a safe takeoff, CFL must not be greater than the runway available
Takeoff Factor
takeoff factor numbers are & N1 settings adjusted for OAT and altitude and are presented on a different scale
Takeoff Ground Run
the runway distance normally obtained in service operation at zero wind at the mission-specified
- weight,
- pressure altitude,
- thrust setting,
- ambient temperature, and
- appropriate takeoff configuration
using liftoff speed
Distance to 50-foot Obstacle
(Distance to Reference Zero)
- the sum of the takeoff ground run distance to liftoff, plus the airborne horizontal distance needed to accelerate and climb to arrive at the 50-foot obstacle height at or above the obstacle climbout speed
- if S1 < Vrot → CFL must be used for the distance from brake release to liftoff
- in all cases, this will equal or exceed actual ground run during engine failure at or greater than S1
Reference Zero
- the point in space at the end of the takeoff flare distance at which the aircraft reaches 50 feet above the runway elevation
- will occur no later than departure end of the runway
Minimum Control Speed Ground (Vmcg)
- 88 KIAS
- the minimum controllable speed during the takeoff run, at which, when an engine fails, it is possible to maintain directional control using only primary aerodynamic controls without deviating more than 25 feet laterally with all three wheels on the runway
- the speed is established with the remaining engine at the takeoff thrust setting, the aircraft loaded at the most exceeding 180 pounds of rudder control force by the pilot with the rudder boost system operating
- conditions of crosswind and RCR may increase Vmcg
Minimum Control Speed Air (Vmca)
- 89 KIAS
- the minimum controllable speed in the takeoff configuration out of ground effect with one engine inoperative and the remaining engine at takeoff rated thrust
- determined by at the most critical combination of asymmetric thrust, lightweight, and aft center of gravity
- the speed is established with the aircraft trimmed for takeoff, 5° AOB into the operating engine and no more than 180 lbs of rudder control force by the pilot with the rudder boost system operating
- always less than takeoff speed and is not considered in takeoff planning
Refusal Speed (Vr)
the maximum allowable speed that can be attained, with normal acceleration, from which a stop may be completed within the available runway length
Maximum Braking Speed for Takeoff (Vb)
the max speed from which the aircraft can be brought to a stop without exceeding the max brake energy limit [14.8 million ft-lb]
Maximum Braking Speed for Landing (Vb)
- the max speed from which the aircraft can be brought to a stop without exceedinf the energy absorption capability of the brakes
- energy absorption corresponds to the fuse plug brake energy [4.05 million ft-lb/brake]
Takeoff Acceleration Check
- provides a speed for a given distance during takeoff ground roll
- can be checked against aircraft indicated airspeed at that distance point to ensure that the takeoff is proceeding normally
- should be adjusted to be at least 10 KIAS less than S1
- compute whenever S1 < Vrot
- effects of wind, runway gradient, and RSC are included in the takeoff ground run
- use 100% of runway wind component for takeoff ground run determination
Go/No Go Speed (S1)
- takeoff committed at indicated airspeeds at or above S1
- if an engine failure occurs prior to obtaining S1 and action is taken to stop the aircraft before obtaining S1, takeoff abort capability is assured
- in takeoff planning:
S1 must be ≥ the higher of Vmcg or Vcef
S1 must be ≤ lowest of Vr, Vrot, or Vbmax
S1 equation
Vmcg, Vcef ≤ S1 ≤ Vrot, Vr, Vbmax
My Crap Smells Really Really Bad
Rotation Speed (Vrot)
- the speed at which the aircraft attitude is increased from the ground run (taxi) attitude to the lift-off attitude
- Vrot > Vmcg
Lift-off & Lift-off Speed (Vlof)
- the moment at which the main gear lift off the runway
- lift-off speed (Vlof) - the speed at which lift-off occurs
Takeoff Flare
the ground distance covered between lift-off and the 50-foot obstacle height
Takeoff Speed
the speed which permit attaining the obstacle climbout speed at or before reaching the 50-foot obstacle height above the runway
Climbout Speed (Vco)
- the scheduled single-engine combout speed and should be obtained at or prior to reaching the 50-foot obstacle height
- due to excess thrust available with 2 engines operating, the 2-engine climbout speed is 10 knots greater or Vco + 10 knots
Climbout Factor
- the variable used to determine takeoff/climb performance and obstacle clearance
- minimum climbout factor for all takeoffs is 2.5
