Friday, March 30, 2018

What is the FLEX Temperature?

FLEX temperature is an assumed temperature that is used in aircraft engine controls to increase the engine life. FADEC oversees all the operations related to the engine depending on the commands and outside conditions. 

When the pilot enters the OAT to the FADEC through MCDU, a much elevated value (let’s say 400C), FADEC thinks that the OAT is 400C and it adjusts its performance according to it. Hence engine will be operated in a de-rated manner generating less thrust than usual TOGA thrust. Engine will generate thrust that suits for a warmer day and definitely it’s less when compared to thrust delivered in a normal day. 

Main intention for the usage of FLEX temperature is to reduce engine ware by the reduction of time spent under TOGA thrust. An engine encounters extreme operating temperatures during this time and will cause thermal fatigue on many engine parts that lowers the life span of those components. Hence more time under TOGA the engine will be aged rapidly.

There are some exemptions for the use of FLEX temperature. Mainly it depends on current aircraft status and ambient environmental conditions. When the aircraft is heavy (aircraft weight close to MTOW) and its some functions are de-rated, it’s not allowed to perform a FLEX takeoff. 

When the outside temperature is too high, when the runway is contaminated with ice/snow or departing from an airport where its elevation is too high to make the air denser will call upon the full thrust over FLEX.

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