Airbus Engine Vibration Question

PGT said:
On props it's if the RPM isn't matched up, you get this really annoying "waw.waw.waw."
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Quick way to make any multi pilot/instructor mad...take off and act like you don't hear it.
It's a riot.





It is the small things in life.
 
BobDDuck said:
Any Airbus drivers know why, every once in a while in cruise flight, the engines start running really rough for a few minutes and then smooth out? It almost feels like when you get ice buildup on the fan blades (in a CRJ) but not that bad.

We are cruising along at 36,000 and it just started a few minutes ago, stopped for a while and then started again. I've noticed it on other flights too.

Anybody?
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Were you by chance near the lav? Our lav pump sounds like the props going out... Or like they're eating gravel...
 
PGT said:
Engine synch usually works off of the right engine, why is that?
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Left engine's critical on a jet. Do you know how much P-Factor you have when you're pimping thousands of pounds of thrust?






































































*giggle!*
 
747-400 (CF6) has engine trim to sync N1s

E145 has the same

E170 also

747-200 has FE engine trim
 
A-300F4-622R said:
No engine sync on any turbojet I've ever flown and I've flown the first generation jets right up to the most modern.
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Not sure what sort of jets you been flying but as Polar and others have said, a bunch models do. Add to his list the CRJ700/900 which has the option of N1 or N2 syncing using the FADEC. On the small CRJ you have to manually sink the fans by adjusting the N1s with the thrust levers.
 
BobDDuck said:
Not sure what sort of jets you been flying but as Polar and others have said, a bunch models do. Add to his list the CRJ700/900 which has the option of N1 or N2 syncing using the FADEC. On the small CRJ you have to manually sink the fans by adjusting the N1s with the thrust levers.
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Flown CJ-610, TFE-731, JT-3D, JT-8D, CF-6, JT-9D, PW2000, RB-211, RR-Tay, CFM-56, PW4000. Of those, only the TFE-731 had a pilot operable engine sync.
 
It's news to me that Airbus and Boeing planes (excluding DC-9s) have anything that keeps the engine RPMs balanced.

I am aware N1 trim values, but that is something specific to each individual engine. It is a schedule of N1 values that are empirically-derived in a test cell to relate the actual tachometer N1 to the "book value" N1 for the full range of thrust settings (ECAM/EICAS indications are normally the trimmed values). It is fixed in the EEC and (as far as I know) does not change while on-wing.
 
A-300F4-622R said:
No engine sync on any turbojet I've ever flown and I've flown the first generation jets right up to the most modern.
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The Jets I have flown have had Sync but I have only flown ones with 2 engines.<?xml:namespace prefix = o ns = "urn:schemas-microsoft-com:office:office" /><o:p></o:p>
 
Minuteman said:
It's news to me that Airbus and Boeing planes (excluding DC-9s) have anything that keeps the engine RPMs balanced.

I am aware N1 trim values, but that is something specific to each individual engine. It is a schedule of N1 values that are empirically-derived in a test cell to relate the actual tachometer N1 to the "book value" N1 for the full range of thrust settings (ECAM/EICAS indications are normally the trimmed values). It is fixed in the EEC and (as far as I know) does not change while on-wing.
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I will only comment on the airplanes I have flown (and remember how the system works)

The 747-400s fly run the CF6s. The sync of the engines is controlled through the Autothrottles and EEC. It can also be toggled off via the MCDU.

The EJet, running CF34s, had a similar system that matched N1s using the autothrottles and FADECs. Again, it is toggled off through the MCDUs.

Both systems used the autothrottles to set the targeted N1 and match the engines within a specific range, then the EECs would make continual fine adjustments the keep the N1s matched. There were minor differences in the exact operation of the trim system, but the theory behind each was similar.

The E145, with the Allison 3007s, had the gross adjustement via a manual throttle setting, then the FADEC would again make the fine adjustments.

Then the old school 747-200. The autothrottles would drive until the first throttle hit the requested thrust, then the clutch pack would release and the FE would target the other 3 engines. We'd play with tweeking them if we were bored in cruise, other than that, let them run wild. ;)


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Dough seems to think I'm a sharp guy... little does he know since he's never flown with "Crash." :)


I've gotta sniff around about the engine sync- I've got around 1400 hours in the 757 and it's safe to say that even with the TL's perfectly aligned with each other, the N1 fans wont synch up, and those are fadec engines. However, when you do align the N1's they stay there pretty well. The digital response works very smoothly. Although, it does drive me crazy on a 4 hour leg flying with a guy that doesnt notice the "womp womp womp womp" the whole time. Just wait until they turn around and trim the TL's, haha.

The 767-300 "domestic" with the rudimentary and old school EEC's are very much not synched unless you work for it and very touchy... similar to the JT8's on the MD-88.

I'll look up if there is some sort of a synch tonight though.


Just flew the Saints on a charter yesterday to IAD then ferried the 763 empty from IAD-BWI. And due to the snow it was required to be a full power takeoff..... VROOM!!!!
 
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