C172 Asymmetrical flap deployment

Discussion in 'Pilot Training' started by DesertNomad, Aug 19, 2014.

  1. DesertNomad

    DesertNomad Pattern Altitude

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    One of the local C172's had an asymmetrical flap deployment a couple days ago - it looked like the left flap was at about 30° and the right one at zero (C172M so it goes to 40°), but in flight the wind would have kept it a bit less of a deployment.

    How much authority do the ailerons (and rudder) have to overcome this?

    Anyone ever seen this before while they were flying?
     
    Last edited: Aug 19, 2014
  2. MAKG1

    MAKG1 Touchdown! Greaser!

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    The only way this can happen on a Cessna is if the interconnect between the flaps breaks. If that's the case, one of the flaps is controllable by the motor, and the other is just free. It should take minimal slipstream to push it back to nearly zero. So, retract the flaps to make them symmetrical, probably near zero.

    Cessna singles have only one flap motor.
     
  3. DesertNomad

    DesertNomad Pattern Altitude

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    Not sure what happened exactly but pushing the left flap up manually while parked on the ramp, it would not go further up than 20°. The CFI said it was not a fun experience.
     
  4. James331

    James331 Ejection Handle Pulled

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    I've heard this is really rare, most cesuras have good fail safes (especially the van).

    If you start to get a roll,yaw when dropping flaps, slap em to 0 (if you have the speed and altitude), power up and configure for a 0 flap landing.
     
  5. Dan Thomas

    Dan Thomas Final Approach

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    A sign of really poor maintenance inspections. There are a pair of cables that run from the right flap bellcrank over to the left flap, above the headliner. Those cables fray right in the middle of the ceiling where there are small nylon pulleys that don't turn most of the time (sludged-up bearings), they get dirt embedded in them, the cables drag across that grit and vibrate against it too, and they get worn. Inspecting those is a 200-hour item, yet many guys can't be bothered. Those cables have to be in really poor shape to break, meaning that they've been ignored for a long time.

    Another bad spot in Cessna flaps are the rollers that run in the flap tracks. Those rollers are just Torrington needle bearings with a sleeve pressed over them, and that sleeve shifts sideways a little on the bearing and cuts a circular groove in the flap support arm. Eventually the aluminum gets cut most of the way through, a circle of aluminum punches right out, and the flap cocks and jams and twists and can ratch up the whole aft spar in the wing. Cessna had a Service Bulletin on it nearly 20 years ago; there's no excuse for such stuff. McFarlane sells roller kits to fix the problem.

    Dan
     
  6. NJP_MAN

    NJP_MAN Pattern Altitude

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    C208B has a standby flap motor.:)
     
  7. DesertNomad

    DesertNomad Pattern Altitude

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    Interesting. This 172 is part of a flight school that I think does on going maintenance rather than 100-hour inspections. I don't fly this 172 (I've only flown it once) but do fly one of their other aircraft.

    I'll ask him about the details of the problem.