c5load
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Posts: 344
Joined: Tue Sep 16, 2008 9:40 pm

Split Throttle Procedures

Wed Mar 16, 2011 3:20 pm

The other day I was flying from UAFM-ETAR and was put in a step climb. I noticed when we would level off the pilots would bring back 1 and 4 throttles for a few couple of minutes, then push them up and bring back 2 and 3. When asked, they said when all four throttle handles were in the same position it put the engines in the vibe range. Do civilian four engine airliners do this at lower altitudes?
"But this airplane has 4 engines, it's an entirely different kind of flying! Altogether"
 
411A
Posts: 1788
Joined: Mon Nov 12, 2001 10:34 am

RE: Split Throttle Procedures

Thu Mar 17, 2011 2:47 am

No, generally not, at least on the specific types that I have flown.
However, on some types with turbocompressors (B707 for example), outboard engines are reduced to idle for descent, and the inboard throttles are left slightly advanced, to ensure enough air is available from the turbocompressors, to allow the cabin altitude to descend, for landing.
 
tdscanuck
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RE: Split Throttle Procedures

Thu Mar 17, 2011 4:46 am

Quoting c5load (Thread starter):
When asked, they said when all four throttle handles were in the same position it put the engines in the vibe range. Do civilian four engine airliners do this at lower altitudes?

None that I know of. Some engines do have keep-out zones (speed/altitude combinations) to avoid vibration and resonance, but the FADEC takes care of that and it's not something the crew generally has to deal with.

Tom.
 
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airportugal310
Posts: 3218
Joined: Sun Apr 11, 2004 12:49 pm

RE: Split Throttle Procedures

Thu Mar 17, 2011 11:42 pm

Quoting c5load (Thread starter):
The other day I was flying from UAFM-ETAR and was put in a step climb. I noticed when we would level off the pilots would bring back 1 and 4 throttles for a few couple of minutes, then push them up and bring back 2 and 3. When asked, they said when all four throttle handles were in the same position it put the engines in the vibe range. Do civilian four engine airliners do this at lower altitudes?

That seems like a pain. I didn't think that engines had to be THAT closely monitored. Learn something new everyday
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