TOLD Definitions

Take-off rated thrust is the maximum allowable thrust (determined by fan speed N₁). It varies with pressure altitude, ram air temperature, and bleed air usage. Operation of TRT is limited to 5 minutes.

Maximum continuous thrust is the maximum allowable thrust (determined by fan speed N₁) that may be used without time limitation. Maximum continuous thrust varies with pressure altitude, ram air temperature, and bleed air usage.

Runway length is the paved surface lenth excluding any overrun.

Critical engine failure speed is defined as 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.

The critical field length is the total length of the runway required to accelerate on all engines to critical engine failure speed, experience and engine failure, then continue to lift-off or stop.

Take-off factor numbers are % N₁ settings adjusted for OAT and altitude and are presented on a different scale.

Take-off ground run is defined as that runway distance normally obtained in service operation at zero wind at the mission-specified weight, pressure altitude, thrust steting, ambient temperature, and appropriate take-off configuration using lift-off speed.

Ground minimum control speed, V_mcg (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 settting, the aircraft loaded at the most unfavorable weight and center of gravity, and the aircraft is trimmed for takeoff, without exceeding 180 pounds of rudder control force by the pilot with the rudder boost system operating. Conditions of crosswind and RCR may increase V_mcg.

Air minimum control speed, V_mca (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. V_mca is determined by the most critical combination of asymmetric thrust, lightweight, 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 pounds of rudder control force by the pilot with the rudder boost system operating. V_mca is always less than take-off speed and is not considered in takeoff planning.

Refusal speed, V_r, is 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 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 pounds).

A take-off acceleration check provides a 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 the take-off is proceeding normally. Takeoff acceleration check speed should be adjusted to be at least 10 KIAS less than S₁. Compute take-off acceleration check whenever S₁ is less than V_rot. 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.

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, take-off abort capability is assured. In take-off 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 take-off weight must be reduced until this requirement is met.

Rotation speed is defined as the speed at which the aircraft attitude is increased from the ground run (taxi) attitude to the lift-off attitude. This speed is greater than the ground minimum control speed.

Lift-off is the moment at which the main gear lift off the runway.

Lift-off speed is the speed at which lift of occurs.

Take-off flare is the ground distance covered between lift-off and the 50-foot obstacle height.

Take-off speed is defined as that speed which permits attaining the obstacle climbout speed at or before reaching the 50-foot obstacle height above the runway.

Climbout speed is the scheduled single-engine climbout speed and should be obtained at or prior to the 50-foot obstacle height. Due to excess thrust available with two engines operating, the two-engine climbout speed is 10 knots greater or V_co + 10 knots.

Climbour factor is the variable used to determine take-off/climb performance and obstacle clearance. Minimum climbout factor for all take-offs is 2.5.