Take off Rated Thrust (TRT)
Take off rated thrust is the maximum allowable thrust (determined by fan speed %N1). It varies with pressure altitude, ram air temperature, and engine bleed air usage. Operation at TRT is limited to 5 minutes.
Depending on the operating conditions, the %N1 for TRT will be defined by one of the following engine limitations:
● Limiting Fan %RPM: 104%
● Limiting Inter-Turbine Temperature (ITT): 700oC
● Limiting Gross Thrust: 2900 LB
Constant altitude lines are defined by the engine gross thrust limit.
The %N1 limit line annotated by a specific bleed air configuration (such as ACM ON, ALL ANTI-ICE OFF) is defined by the ITT limit.
At pressure altitudes above 8000 ft, TRT is based on the %N1 limit line annotated by a specific bleed air configuration (ITT) limit or limiting Fan %RPM (104%), depending on temperature. If PA is 8500 and the RAT is -30oC, TRT is 104% N1.
KEY ITEMS:
Maximum allowable thrust based on %N1. Varies with pressure altitude, ram air temperature, and engine bleed air usage, limited to 5 minutes.
Maximum Continuous Thrust
Maximum continuous thrust is the maximum allowable thrust (determined by fan speed %N1) that may be used without a time limitation. MCT varies with pressure altitude, ram air temperature, and engine bleed air usage. MCT is normally used for climbing flight.
Depending on the operating conditions, the %N1 for TRT will be defined by one of the following engine limitations:
● Limiting Fan %RPM: 106%
● Limiting Inter-Turbine Temperature (ITT): 680oC
● Limiting Gross Thrust: 2900 LB
At pressure altitudes above 10,000 ft, MCT is based on the %N1 limit line annotated by a specific bleed air configuration (ITT) limit or limiting fan %RPM (104%), depending on temperature. If PA is 10,500 feet, and RAT is -50oC, with ACM and ALL ANTI-ICE ON, MCT is 102%N1
Critical Engine Failure Speed (VCEF)
Critical engine failure speed is defined as the speed at which one engine can fail and the same distance is required to either to continue to accelerate to lift-off speed, or to abort and decelerate to a full stop.
Critical Field Length (CFL)
Critical Field Length (CFL)
The Critical Field Length is the total length of runway required to accelerate on all engines to Critical Engine Failure Speed (VCEF), experience an engine failure, then continue to lift-off or stop. It is used during take-off planning together with the climbout data to determine maximum gross weight for a safe takeoff and climbout. For a safe takeoff, the critical field length must be no greater than the runway available.
Take-Off Ground Run
Take-off ground run distance is defined as the runway distance normally obtained in service operation at zero wind at the mission specified weight, pressure altitude, thrust setting, ambient temperature, and appropriate take-off configuration using lift-off speed.
Minimum Control Speed Ground (VMCG)
Ground minimum control speed VMCG (88 KIAS), is the minimum controllable speed during the take-off run, at which, when an engine is failed, 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 take-off rated thrust setting, the aircraft loaded at the most unfavorable weight and center of gravity and the aircraft trimmed for takeoff, without exceeding 180 lbs 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)
Air minimum control speed, VMCA (89 KIAS), is the minimum controllable speed in the take-off configuration out of ground effect with one engine inoperative and the remaining engine at take-off rated thrust. VMCA is determined at the most critical combination of asymmetric thrust, light weight, and aft center of gravity. The speed is established with the aircraft trimmed for takeoff, 5 degrees angle of bank into the operating engine and no more than 180 lbs of rudder control force by the pilot with the rudder boost system operating. VMCA is always less than the take-off speed and is not considered in take-off planing.
Refusal Speed (VR)
Refusal speed, VR, is the maximum speed that can be attained, with normal acceleration, from which a stop may be completed within the available runway length. Refusal speed is compared with ground minimum control speed and rotation speed determining S1.
Maximum Braking Speed (VB)
Maximum braking speed is the maximum speed from which the aircraft can be brought to a stop without exceeding the maximum brake energy limit (14.8 Million Foot-lbs total). When setting up the take-off acceleration check, care should be taken to choose the checkpoint such that the resulting speed is below VB
Take-Off Acceleration Check
A take-off acceleration check provides speed for a given distance during take-off ground roll. This speed can be checked against aircraft indicated airspeed at that distance point to ensure that the takeoff is proceeding normally. Take-off acceleration check speed should be adjusted to be at least 10 KIAS less that S1. Compute take-off acceleration check whenever S1 is less that VROT. Effects of wind, runway gradient, and RSC are included in the take-off ground run. Use 100% of runway wind component for take-off ground run determination.
Go/No-Go Speed (S1)
The take-off is 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 is equal to or greater than the higher of ground minimum control speed or critical engine failure speed. However, S1 must not be higher than the lowest of refusal speed, rotation speed, or maximum braking speed. If it is higher, the takeoff weight must be reduced until this requirement is met.
Rotation Speed (VROT)
Rotation speed is defined as the speed at which the aircraft attitude is increased from ground run (taxi) attitude to the lift-off attitude. This speed is greater than the ground minimum control speed (VMCG).
Take-Off Flare
Take-off flare is the ground distance covered between liftoff and the 50 ft obstacle height.
Distance To 50-Foot Obstacle
Distance to 50 ft obstacle is defined as the sum of the take off ground run distance to liftoff, plus the airborne horizontal distance needed to accelerate and climb to arrive at the 50 ft obstacle height at or above the obstacle climbout speed. If S1 is less than VROT, critical field length (CFL) must be used for the distance from brake release to lift-off. In all cases, this will equal or exceed actual aircraft ground run during engine failure at or greater than S1.
Stall Speed (VS)
Stall speed is the higher of:
1. The airspeed at which the aircraft will cease to fly due to the loss of aerodynamic lift during the application of slow smooth control inputs.
2. The minimum steady flight speed at which the aircraft is controllable.
Climbout Speed (VCO)
Climbout speed is the scheduled single-engine climbout speed based on 1.2 times the stall speed at the take-off weight and should be obtained at or prior to reaching the 50 ft obstacle height. Due to the excess thrust available with two engines operating, the two engine climbout speed is 10 knots greater or VCO + 10 knots.
Final Segment Climb Speed
The climbout speed from 400 feet (1500 feet optional) above the airfield elevation to the end of the take-off flight path (2200 feet above the airfield elevation for one engine inoperative) is 125% of the stall speed at the take-off weight. This is approximately VCO + 15 knots (10 flap or VCO + 5 knots 0 flap).
Range Climb
The range climb speed schedule will result in a somewhat longer time and a greater fuel usage than the rate climb. The range climb schedule may be used when minimum climb fuel and time are not required, but a longer climb range is desired.
Rate Climb
The scheduled airspeed for the rate climb is the speed for best rate-of-climb. A climb scheduled at this speed will result in the least time for the climb segment to the final altitude. 220 Knots
Reference Speed (VREF)
Reference speed (VREF) is the 30 degrees flap approach speed. Approach speeds for flaps 0 degree and 10 degrees are noted on the landing speeds chart.
Approach Speed (VAPP)
Approach speed (VAPP) is the airspeed equal to 1.3 VS for a given flap setting.
VAPP Flaps 30 degrees = VREF
VAPP Flaps 10 degrees = VREF + 10 KIAS
VAPP Flaps 0 degrees = VREF + 20 KIAS
Approach Climb Speed (VAC)
Approach climb speed (VAC) is the airspeed for the approach climb configuration. VAC equals VREF +22 KIAS.
Flare Distance
Flare distance is the ground distance covered from the 50 ft height to touchdown.
Landing Ground Roll Distance
Landing ground roll distance is the distance covered from touchdown to full stop using normal braking procedures.
