what percent is a derated takeoff and how do you apply assumed temperature?

Answer 1

For us, a derated or reduced thrust takeoff is anything that our book says is less than the normal takeoff thrust. That could be as low as 85% N1 up to 90% N1. It depends on the weight of the aircraft as well as the airport and temperature.

The assumed temperature is simply a means of correcting our V speeds for the reduced thrust takeoff. If the assumed is 35 then we will go to the 35 column on the takeoff data card and correct our V1/V2 by the number that is found there. This amount can be anything from 1 knot up to 5 knots.

Answer 2

A derated Takeoff is any take off made with less than the maximum power of the engine(%of N1 on some planes its 100% on others 105% etc) This is done for multiple reasons, to reduce workload on the engine, to increase the engine's life span and to burn less fuel. On most modern airplanes, the flight crew dont firewall the throttles for most of the time anymore(advance the throttle lever forward until it hits the stops)

Answer 3

A de-rated takeoff is a reduced power takeoff. Engine performance, weights, weather conditions, pressure, etc. are taken into account and aircraft-specific tables help calculate what percentage of thrust to use for a de-rated takeoff.