767 inboard ailerons

[orion1210]

Hi,

I flew on a delta 767-300er out of manchester on sunday to ATL. I was sat on the left side and noticed in the cruise that the left inboard aileron or aka high speed aileron was deflected up by about what looked to be 6-8 inches.
At first I assumed there was a fuel imbalance, but it stayed this way for the duration of the 9 hr flight. Surely an imbalance would of been dealt with. I didn't see the right side, but I don't think it was trim for yawing due assymetric thrust as I couldn't detect any yaw and surely you wouldn't fly the whole sector like that?
The only thing i can come up with is that both sides were rigged up. As a licenced engineer I can think of reasons to do this, but it looked so inefficient.
They drooped as normal with flap selection and returned to neutral with flaps up on the taxi into ATL.

Can anybody shed any light?

Thanks

[subsonic69]

most probably it was trim.. you would not detect any yaw since it was already corrected by the 6-8 inches that you saw from the flaperon ( inboard aileron ) .

any other ideas ?? just in case I got it wrong.

[cessna24]

If the inboard aileron drooped with flap selection and then returned to neutral once the flaps returned to the up position, it could have been a little glitch in the system. But i seem to remember when reading a B767 maintenance manual that {this could be for something else} if the pilot selects aileron trim whilst the A/P is engaged, the aileron does not return to its correct unit. It fly's out of sync so to speak. It only resets its self once A/P has been disconnected.
I could have this wrong.
An interesting one though orion1210.

c24

[airfoilmod]

But Pitch, not Roll. Loaded tail, less drag, saves fuel.

[NSEU]

Flying straight and level... assuming no asymmetries/imbalances in flight with the A/P engaged.... if you added manual aileron trim, wouldn't the autopilot cancel this out, returning the control wheel to neutral?

Surely the crew should have noticed that the wheel wasn't straight (Trim input is backdriven)...unless, of course, this 6~8" equates to very little at the control wheel. Seems a lot aerodynamically, though.

Actually, the "neutral" position is 0.5 degrees down (from the faired position), but I'm not sure you would notice this.

With a setup like this (767), I can't see how disconnecting the A/P would return the trim to neutral.

Strange indeed.
Rgds.
NSEU

[Bolty McBolt]

Heavy aileron trim during cruise...

I have seen and troubleshot this defect to return a couple defects on the 767. After checking the usual suspects such as cable/actuator rigging to reveal to nil out of rig the following has been discovered on different aircraft for same excess aileron trim defect..

1st and the most common, Rudder trim indicator "ribbon" stretched and not indicating centre (0 units ) when the rudder is in the neutral position.
I have seen a few tech write ups of excessive aileron trim to trim out the rudder displacement due trim indicator. A bit of tail chasing. The EICAS flight control position indicating is not accurate enough to show the rudder out of trim especially in the high speed mode. I have often mused that we must have quite a few pilots with different length legs..
Its quite common to see up to 2 units of rudder trim on the 767-300 during climb and early cruise , then use same amount of trim in the opposite direction on descent. It would appear a faulty rudder trim indicator could trip up crews in a busy (high load) cockpit as aileron trim is used to achieve the aircraft to fly straight and true.

The 2nd and less common is due to Trailing edge flap rigging /construction.
There was a time when the out board flap assy were being changed frequently due to a mod or water ingress and being swapped from aircraft to aircraft within my fleet causing same trim defect .
For aircraft that need excess aileron trim to fly level with all rigging of flight controls checked ok. The maintenance manual states an amount of shim material to fit Vs the amount of aileron trim to lower the outboard flap assy (one side). This does not lower the flap the same as extension of the flaps but lowers the whole assy down away from its mounts...

Not saying this was the reason for the aileron displacement in the original posters question just something to add to the speculation

[cessna24]

What i previously wrote was complete bo:mad:cks!!. Got muddled with something else I think. :=
But, when at work today, i had a little play and i engaged autopilot and hdg select to 10 degrees to the left. The control coloumn moved to the left as normal then returned to neutral. I manually selected trim and nothing happened as far as control coloumn movements, then i disengaged the a/p and the coloumn moved to the left to the trimed position i had set.
So as others have said, it must have been a trimmed position due to flight conditions.

Anyone else.
Kind regards
c24

[KUMOOZ]

Aileron trimming with A/P engaged is not allowed on the 757/767.
You may get a nasty surprise on finals when disconnecting the A/P!
Safe flying!