Asymmetric Flap Deployment

[Tom Veatch]

1960 PA-24-250 with manual flaps.

When attempting to retract the flaps, either in flight or on the ground, the left flap hangs at about the 1 notch extension instead of retracting to the 0° stowed position. This results in an asymmetric flap deployment and a roll to the right which can be counteracted with aileron without losing roll control of the aircraft.

In flight, below the 125mph flap deployment speed, after a couple of tries, I was able to return the flap to stowed position by pulling full flaps and dumping them suddenly in one movement. Testing on the ground, with the flap lever in stowed position, significant manual force on the trailing edge of the left flap is required to move the flap to the 0° position. When commanding flaps up with the manual lever the right flap returns to the stowed position but is not locked in that position until the left flap is manually stowed. When manually stowing the flap, it feels as if there is some obstruction and once forced past that single point obstruction, the flap return spring is sufficient to stow and lock the flaps up. There seems to be no difficulty or resistance to extending the flaps.

In either case, in flight or on the ground, with the left flap extended and the right flap stowed, the flap lever moves freely with no spring tension/stick force between the positions for 0° and about 1 notch of deployment.

I'll not be able to address this issue until my wife and I recover from this flu, cold, whatever we've been battling since just after Christmas, but if anyone has any comments, suggestions, experience with similar conditions, etc., I'd be pleased to hear them.

[Zach Grant L1011jock]

On the manual flap aircraft, there are up locking mechanisms on both sides. The first bit of cable tension releases the uplock and then extends the flaps with further movement of the lever. When returning the lever to the flaps up position, there is nothing but spring tension to return the flaps to up/locked. Most people start having "hung" flaps on retraction, or problms with the up locks not engaging, when the first cold snap hits, or when they fly a normally warm weather aircraft into the cold country. The simple reason for this is that the uplock cam and slider assembly simply end up with too much friction from the warm weather lube (most often I find spray on white lithium marine grease or similar installed) and cleaning the mechanism thouroughly with a lubricant with some solvent capabilities, and using a dry lube such as triflo or another teflon based comercial lube solves the problem. The mechanisms are easily accessed by removing the wheel well inserts.

Zach

[Tom Veatch]

Thanks, Zach. Cleaning and lubricating fixed the problem.