Re: Power Hungry air conditioning ?

From:         Crone <>
Organization: University of Washington
Date:         22 Mar 95 02:34:22 
References:   1
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> I was taking off from Mombasa last Monday and was surprised to hear the pilot
> advice us that - due to the high outside temperature causing lower engine
> efficiency - he would be turning off the cabin air conditioning during takeoff
> to get more power.
> Does the air conditioning consume a significant portion of the engine power ?
Oh yes!  It certainly does, at least in older jet aircraft, maybe the 
newer generation engines are not as effected.  In my old C-141, turning 
off air conditioning is not unusual in hot weather takeoff situations.

> I thought it was driven from the APU anyway.

Again, the following is true for the 141.  The APU is shutdown usually 
after engine start but definitely no later than takeoff roll.  Why?  The 
inlet for the APU faces sideways to the airflow, it would simply starve 
for air once the airplane gets going.