Originally Posted by
Hueymeister
So, how does increasing air bleed demand (put eng anti ice on) for take off at high density altitudes help control engine rpm in a high-bypass turbofan engine?
The pilot’s notes (-1) for my aircraft suggests that using engine anti ice may prevent rpm over speeds at high density altitudes. I think I know why, but am not quite sure.
I am puzzle by the instruction you read from pilot's notes for prevention of over speeds, my understanding:-
In a multi spool compressor using air off take would unload the forward spools causing them to speed up!
Same config at T/O would decrease thrust if an increase in fuel/EGT were not made!
Same config. a low air density (high altitude) would also cause front spools to run faster and perhaps over speed!
The only good reason for using air off takes,as far as the engine is concerned, is to improve the compressor stall margin for engine!
Welcome corrections.