Aileron rigging question
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Aileron rigging question
On a recent flight (as SLF) in an Airbus 319 in cruise I noticed that both ailerons were deflected up by about 3 or 4 degrees. I can appreciate why this is a good idea for drag reduction when at high speed when not all the lift generated by the wing is needed to maintain level flight and if the angle of attack on the whole wing was reduced by pitching the nose down the fuselage then would be at a sub-optimal angle.
The question is how are the ailerons controlled, and at what range of airspeeds/Mach nos does it work? At approach speeds the ailerons seemed to follow the camber of the wing and behave normally, without droop.
I'd be interested to know how this works; the aeroplanes I used to fly were never as clever - no FBW!
MB
The question is how are the ailerons controlled, and at what range of airspeeds/Mach nos does it work? At approach speeds the ailerons seemed to follow the camber of the wing and behave normally, without droop.
I'd be interested to know how this works; the aeroplanes I used to fly were never as clever - no FBW!
MB
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As far back as the L1011 Tristar active control systems have done 'clever' things with the ailerons.
At high lift modes (flaps / slats extended) the ailerons deflect up to dump lift from the wingtips and move the lift envelope inboard - alleviate root loads.
In elastic mode suppression (wing flapping) the ailerons move up or down together to counter the flapping motion.
In approach mode the ailerons feed into the spoilers, to augment roll control at slow speeds.
Things have moved on quite a lot since then, and you'll find inboard and outboard ailerons doing different things at any given time!
At high lift modes (flaps / slats extended) the ailerons deflect up to dump lift from the wingtips and move the lift envelope inboard - alleviate root loads.
In elastic mode suppression (wing flapping) the ailerons move up or down together to counter the flapping motion.
In approach mode the ailerons feed into the spoilers, to augment roll control at slow speeds.
Things have moved on quite a lot since then, and you'll find inboard and outboard ailerons doing different things at any given time!
Even earlier than the L1011, the VC10 had a wing bending relief system which allowed the ailerons to be raised in unison by up to 10degrees at some weights/altitudes.to ease wing bending
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The ailerons' actuators aren't linked together mechanically or anything, so they can operate entirely different if that's what the FBW computer wants. Others have addressed the aerodynamic reasons.
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Even earlier than the L1011, the VC10 had a wing bending relief system which allowed the ailerons to be raised in unison by up to 10degrees at some weights/altitudes.to ease wing bending
Far too long since I worked on it to recall...
Electronicals? In a VC-10?
Not levers, but switches a little higher up, that release two equally athletic mice that run inside wheels with cables.
Not levers, but switches a little higher up, that release two equally athletic mice that run inside wheels with cables.
The 'aileron upset' system, as it was called on the VC10. Can you imagine, a switch for upsetting your ailerons! I don't know how they still get away with it in this day and age of laws against bullying and harassment! 
The Victor K2 had it's ailerons permanently up-rigged to provide wing bending relief in it's later years. Permanently upset, they were. Poor ailerons!
The Victor K2 had it's ailerons permanently up-rigged to provide wing bending relief in it's later years. Permanently upset, they were. Poor ailerons!
Most FBW Airbus either have an active aileron system fitted as standard, or on some types as an option. Know as Manoevre Load Aleviation (MLA) it's controlled by the FBW electrickery. It's there, and that's all the manuals say about it - so don't ask the pilots how it works. The ailerons on the A320 series also droop a bit with full flap to add a little more lift, but this reduces aileron effectiveness.
My company removed the MLA on it's Airbusses as it cost more than it saved.
My company removed the MLA on it's Airbusses as it cost more than it saved.
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I will tell a scary story here.
Soon after I had bought an HS125 700 crews reported sluggish performance and roll control. 3 or 4 times the engineers reported "nil defect found".
On a heavy crew sector I was down the back of the aircraft and woke up in the morning to look out of the window and saw the right aileron fully up. I looked at the other aileron and that was fully up too! To cut a long story short the servo tab had been rigged wrong together with very slack aileron cables (wrong cable size tensioner units used) caused both ailerons to upfloat in flight, completely to the mechanical stops. All aileron control input was doing was lowering one aileron. No wonder it was a bit sluggish. On the ground all returned to normal and "no fault found". When I reported this to the engineers they did not believe me. As sort of inadvertant wing bending relief?
Soon after I had bought an HS125 700 crews reported sluggish performance and roll control. 3 or 4 times the engineers reported "nil defect found".
On a heavy crew sector I was down the back of the aircraft and woke up in the morning to look out of the window and saw the right aileron fully up. I looked at the other aileron and that was fully up too! To cut a long story short the servo tab had been rigged wrong together with very slack aileron cables (wrong cable size tensioner units used) caused both ailerons to upfloat in flight, completely to the mechanical stops. All aileron control input was doing was lowering one aileron. No wonder it was a bit sluggish. On the ground all returned to normal and "no fault found". When I reported this to the engineers they did not believe me. As sort of inadvertant wing bending relief?
