Diego
Topic Author
Posts: 135
Joined: Mon Apr 23, 2001 7:33 pm

Throttle Split

Wed Apr 23, 2003 10:28 am

hi folks, the other day I was flying an old all beated up learjet 24 when I noticed that the throttle split was even bigger than in the lear that I normally fly and to tell you the truth while shooting the ILS in IMC late at night, after having flown 4 other legs, it can be really annoying adjusting the throttles correcting for that split reffering to that small N1 gauge, so while I was perched on my seat I was wondering if airliners with FADEC systems still have the throttle split or if the FADEC automatically matches the two engines. One last thing that airplane was not equipped with a synchophaser and even if it was normally we switch it off at 18000ft while we complete the approach checklist besides on lears before switching the synchro on, the two N1,s must be adjusted so that the difference between them is not greater than 1.5%.
Thanks!!
 
Guest

RE: Throttle Split

Wed Apr 23, 2003 11:17 am

Sounds to me like you guys may have inadvertently turned off one of the bleed air selectors.
 
VC-10
Posts: 3546
Joined: Tue Oct 26, 1999 11:34 am

RE: Throttle Split

Wed Apr 23, 2003 4:59 pm

Oh my god, you had to work while you were flying for once  Smile

No, FADEC equipt a/c do not suffer from throttle stagger. Put simply the thrust lever angle on the pedestal relates to a particular N1 speed or EPR setting, so that what you get. The EEC will adjust the HMU to allow for the bleed config of the engines to maintain the TLA/thrust setting relationship.

On the A320/340 however you do not have a conventional throttle quadrant, you have detents at TOGA, Flex/Max Cont, Max Climb & Idle. With Auto thrust selected, for T.O. you move the throttle levers to the TOGA detent (or Flex/Max Cont for a derated T.O.) and once airbourne at about 500' (I can't remember the actual fig) you pull the levers back to Max Climb and there they stay until you get to flare on the appr where you pull the levers back to Idle! in the meantime the FMS/A/p has been controlling the thrust settings.
 
AJ
Posts: 2295
Joined: Wed Nov 03, 1999 3:54 pm

RE: Throttle Split

Wed Apr 23, 2003 5:10 pm

We get a thrust lever split on our JT9D fitted 767s, and on our RR 767s if the EEC balanced EPRs cause a large, unsynched N1 split.
 
avioniker
Posts: 1099
Joined: Tue Jan 01, 2002 5:38 am

RE: Throttle Split

Wed Apr 23, 2003 9:31 pm

Actually it is possible for a FADEC plane to have a throttle split if the Autothrottle system is acting up.
The temporary fix is to shut off the ATS and fly by hand and unless your day is really going down the hole that'll take care of things till you get on the ground and someone with a better knowledge of queertrons and black boxes can get a fix on it.
One may educate the ignorance from the unknowing but stupid is forever. Boswell; ca: 1533
 
VC-10
Posts: 3546
Joined: Tue Oct 26, 1999 11:34 am

RE: Throttle Split

Wed Apr 23, 2003 10:14 pm

Actually it is possible for a FADEC plane to have a throttle split if the Autothrottle system is acting up.


Avioniker you are obviously in student mode rather than instructor mode  Smile

Naturally, I was describing a serviceable system. You could go on forever decribing systems with a failure mode.
 
avioniker
Posts: 1099
Joined: Tue Jan 01, 2002 5:38 am

RE: Throttle Split

Wed Apr 23, 2003 10:39 pm

Actually I'm in the middle of troubleshooting a plane with a very long history. Has nothing to do with being a student. It's all based on events and history.
One may educate the ignorance from the unknowing but stupid is forever. Boswell; ca: 1533
 
avt007
Posts: 1989
Joined: Mon Jul 10, 2000 4:51 am

RE: Throttle Split

Wed Apr 23, 2003 11:16 pm

Avioniker- I don't know what aircraft you're working on, but here is a short story that might help. We had a Dash8 -300 with a huge history of power lever stagger. Everyone had a go at it, it would always trim out nicely, but come back again the next week. In the end, one of the trim switches (hidden switches used by maintenance for doing trim runs) was faulty, and would intermittently close by itself, thereby "trimming" that one engine out of whack.
Good luck!
 
AAR90
Posts: 3140
Joined: Fri Jan 21, 2000 11:51 am

RE: Throttle Split

Thu Apr 24, 2003 1:09 am

No, FADEC equipt a/c do not suffer from throttle stagger. Put simply the thrust lever angle on the pedestal relates to a particular N1 speed or EPR setting, so that what you get.

Yes, FADEC equiped a/c can have different throttle positions with equalized engine performance. Virtually all the individual planes I've flown with FADEC had some sort of throttle split. A very small minority had equal throttle positions. Generally speaking though, the split is smaller than with conventional h/m only systems.

*NO CARRIER* -- A Naval Aviator's worst nightmare!
 
VC-10
Posts: 3546
Joined: Tue Oct 26, 1999 11:34 am

RE: Throttle Split

Thu Apr 24, 2003 2:03 am

Yes, FADEC equiped a/c can have different throttle positions with equalized engine performance

I stand corrected, but my own personal experience since we have been operating 747-400's with CF6-80's, A320's with IAE/CFM engines and A340's with CFM's & RR Trents is that we have never had stagger reported.

Avioniker, what I said wasn't meant as a slight at you, I was just going on your occupation as described in your profile and thought about the sort of questions students asks.
 
AAR90
Posts: 3140
Joined: Fri Jan 21, 2000 11:51 am

RE: Throttle Split

Thu Apr 24, 2003 7:49 am

... is that we have never had stagger reported.

I never report it unless it is a significant amount... which is pretty rare.  Wink/being sarcastic

*NO CARRIER* -- A Naval Aviator's worst nightmare!
 
avioniker
Posts: 1099
Joined: Tue Jan 01, 2002 5:38 am

RE: Throttle Split

Thu Apr 24, 2003 10:06 pm

No offense taken.

I'm waiting for the engines to get a bit more wear on them to see what'll happen when they need more rpm to develop the same EPR on both sides of the plane. Of course that won't happen on the GE's since they use N-1. We've been washing our CFM's and you wouldn't believe the difference in
EGT and efficiency after the wash. The change has been on the order of 7 to 15 per cent efficiency and as much as 25 degrees EGT reduction. Now if we could just get those guys in Phoenix to fix the HMU's.

One interesting thing is that the tolerance is still the same as on the non-FADEC engined planes (1" or one knob width) before it's considered a malfunction. What is it that the engineers aren't telling us?

(Could this be part of the "great chemtrail conspiricy"?)

That was a joke! Let's not get on that track on this thread!!!

For the record. I spend a lot more time on the floor than in the classroom. The only reason I'm teaching is because I have schooling to fall back on and lost my medical because of my neck and can't do any extended heavy work . But I can and do still get my hands dirty and cause my wife to threaten me if I "ruin one more good shirt..." (I miss flying but miss working the line more. That was never boring.)
One may educate the ignorance from the unknowing but stupid is forever. Boswell; ca: 1533

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