John Lancaster Posted April 12, 2020 Report Share Posted April 12, 2020 I was practicing landings yesterday at W29 (Stevensville, MD) and noticed a problem with my flaps. After my first landing with 15 degree flaps I heard what sounded like the flap servo motor as I exited the active runway. I hadn't touched the controls and when I glanced at the flaps they looked ok, so I decided I must have imagined it. Flaps retracted normally. Took off and landed again and the same thing happened, in the same place. This time I retracted the flaps again to zero but then the flaps extended on their own. Then they retracted again, as if they had a mind of their own. Called it a day and taxied back to the hangar, where of course I could not duplicate the problem. Flaps extended and retracted normally this time. Wondering if anyone else has had this problem and was able to identify a cause. I've heard of runaway trim. But runaway flaps? Quote Link to comment Share on other sites More sharing options...
FlyingMonkey Posted April 13, 2020 Report Share Posted April 13, 2020 10 hours ago, John Lancaster said: I was practicing landings yesterday at W29 (Stevensville, MD) and noticed a problem with my flaps. After my first landing with 15 degree flaps I heard what sounded like the flap servo motor as I exited the active runway. I hadn't touched the controls and when I glanced at the flaps they looked ok, so I decided I must have imagined it. Flaps retracted normally. Took off and landed again and the same thing happened, in the same place. This time I retracted the flaps again to zero but then the flaps extended on their own. Then they retracted again, as if they had a mind of their own. Called it a day and taxied back to the hangar, where of course I could not duplicate the problem. Flaps extended and retracted normally this time. Wondering if anyone else has had this problem and was able to identify a cause. I've heard of runaway trim. But runaway flaps? My bet would be a cracked flap control board causing an intermittent connection that is activating the flaps. Quote Link to comment Share on other sites More sharing options...
Anticept Posted April 20, 2020 Report Share Posted April 20, 2020 Your potentiometer has failed and it's seeking flap position. Extremely common. The control board constantly monitors flap position by the use of a potentiometer configured in a voltage divider circuit. As the flaps move, the sense wire will receive a different voltage. When the potentiometer has failed, the voltage on sense will fall outside of the normal range and the flaps will try to seek that position based on if sense voltage is too low or too high, and get confused, resulting in extending and retracting as it runs across the bad spot in the pot track trying to find position. Sometimes that seeking will be enough to loosen the crap on it and it will start working again, but it will happen again. There's a lot of posts already on this forum that covers how to replace and configure the pot. It is located on the flap actuator column. Quote Link to comment Share on other sites More sharing options...
FlyingMonkey Posted April 21, 2020 Report Share Posted April 21, 2020 On 4/20/2020 at 4:03 AM, Anticept said: Your potentiometer has failed and it's seeking flap position. Extremely common. The control board constantly monitors flap position by the use of a potentiometer configured in a voltage divider circuit. As the flaps move, the sense wire will receive a different voltage. When the potentiometer has failed, the voltage on sense will fall outside of the normal range and the flaps will try to seek that position based on if sense voltage is too low or too high, and get confused, resulting in extending and retracting as it runs across the bad spot in the pot track trying to find position. Sometimes that seeking will be enough to loosen the crap on it and it will start working again, but it will happen again. There's a lot of posts already on this forum that covers how to replace and configure the pot. It is located on the flap actuator column. Great information! Quote Link to comment Share on other sites More sharing options...
Runtoeat Posted April 22, 2020 Report Share Posted April 22, 2020 Thanks for posting Corey. Quote Link to comment Share on other sites More sharing options...
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