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Split Throttle Procedures

Posted: Wed Mar 16, 2011 3:20 pm
by c5load
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?

RE: Split Throttle Procedures

Posted: Thu Mar 17, 2011 2:47 am
by 411A
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.

RE: Split Throttle Procedures

Posted: Thu Mar 17, 2011 4:46 am
by tdscanuck
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.

RE: Split Throttle Procedures

Posted: Thu Mar 17, 2011 11:42 pm
by airportugal310
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