cause of damage to flap on 172N?

cause of damage to flap on 172N?

This 1977 Cessna 172N is owned by a flying club.  During a preflight, damage was found on the right flap only.  Could this type of damage to a single flap have occurred in flight or on the ground even if the flaps were not extended outside of the white arc airspeed limit?  Due to some mechanical problem with the flap system?  If so, how could this happen?  Alternatively, could this type of damage to a single flap have been caused by operating the flaps outside of the white arc airspeed limit? Please see the linked set of 7 photos.   Thanks.  Steve S.

http://http://www.flickr.com/photos/37889666@N03/sets/72157623731359330/

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Re: cause of damage to flap on 172N?

All the photos are of the top surface of the flap.  They appear to show damage to the skin that is localized to the area of the actuating rod, apparently suggesting an excessive load in the "downward" or "lowering" direction transmitted from the rod to the flap.  This skin damage does not appear to extend very far across the span of the flap; it appears to be limited to about four or five corrugations.  In addition there appears to be some damage closer to the leading edge of the flap.  I'm puzzled as to just what could cause this pattern of damage.  Is this damage consistent with an excessive aerodynamic load?  Is this damage consistent with a mechanical malfunction that does not necessarily involve an excessive aerodynamic load?  Take a peek at the photos and see if you agree with my description and let me know what you think could cause this.  Thanks!  S.

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Re: cause of damage to flap on 172N?

Steve

Difficult to really see damage from photos

Could someone have tried to extend Flaps with a Flap/Aileron Gust Lock in place?

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Re: cause of damage to flap on 172N?

Thanks for the suggestion, however external control surface locks are never used on this aircraft.

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Re: cause of damage to flap on 172N?

Steve;

I would suggest checking the flap track wear and rollers.  If there is excessive wear or the rollers/spacers in the flap are worn, they can distort and bind when you extend the flaps under a load.  This will not be apparent when operating/checking the flaps on the ground. McFarlane sells a guage that can be used to check the track wear.  even if it is within limits, check the wear on the rollers and spacers.  This can also cause binding. Hope this helps.

Jon

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Re: cause of damage to flap on 172N?

Looks to me like a classic example of misrigged flaps or a microswitch malfunction. I would check the microswitches for function and do a thorougth inspection of the flap system, paying particular attention to the flap tracks mounted at the rear spar. If the flap system was operated outside of the envelope (white arc), flap track damage will be evident by wrinkled underwing skin or working flap track rivets. Oil canning on Cessna control surfaces is pretty common as the use of ribs in control surfaces to hold the shape of the airfoil is limited.

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Re: cause of damage to flap on 172N?

Thanks you for the helpful replies so far.  I am continuing to monitor this thread.  Steve

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