Air cycle machine

[voilier]

Hi,

I had a question about the air cycle machine or the pack? How is it started? Is it done thanks to an electrical motor to start-up the turbine that will drive the compressor? or is it start-up with bleed air and by-passing the compressor?

Thanks for your answers
Regards

[Yeelep]

The ACM is started and operated pneumatically. The compressor isn't bypassed.

[voilier]

Thanks a lot Yeelep!

[grounded27]

With exception of the 787, It is an electrical motor as the aircraft uses no bleed air.

[Plore]

Compressor bypass

The compressor section of the ACM is bypassed with startup on the B777's, A340's and A330's as well... as far as I can recall from my type courses I've attended anyway. Compressor bypass valve I think...

[Yeelep]

I should have stipulated that I was talking about the 737CL/NG

[rajone]

acm

electrically actuated( pack switch) and pnematically operated .