Flaps won't extend beyond 2/3

mshac · #1 10-03-20, 02:29 AM

They work fine up/down in the 1/3 and 2/3 position, but when the selector is placed in the full position, flaps stay at 2/3 position.

Ideas?

Ernie Martin · #2 10-03-20, 03:50 PM

A word of caution is that a flap setting beyond 2/3 MAY be dangerous.

There have been instances of a flap cable breaking on one wing and the aircraft rolling uncontrollably because of insufficient authority of opposite aileron when in full flaps. The problem may even occur at 2/3 flaps. Depending on altitude and how quickly you a) apply opposite aileron and b) raise the extended flap on one side, accidents have occurred and I believe there have been fatalities.

As a result, I adhere to several precautions. At annual inspections I give special attention to the flap-cable inspections. In flight I use more than 1/3 flaps only when absolutely necessary and I lower flaps at a higher altitude as a test, with my hand next to the flap lever to instantly raise the flaps if a cable breaks. So virtually all my landings are at 1/3 flap, where a quick calculation based on aileron and flap surface areas and moment arm indicated that 1/3 flaps on one side can be overcome with full opposite aileron.*

Ernie

_________________
* I'm an aerospace engineer with an MS from Caltech.

mshac · #3 10-03-20, 05:04 PM

I got it figured out. The push-pull cable that attaches to the flap indicator was out of adjustment. The flap indicator interacts with two switches on the flap position selector. They both move, so its a fairly precise little Rube Goldberg mechanism. The push pull wouldnt allow the indicator to go to the full down position, which in turn caused a switch to not be pressed. I took some pics that I will upload later. Files are too big so site wont let me from my phone.

mshac · #4 10-04-20, 11:46 AM

Pics attached. Had to remove the pedestal cover to access the flap selector switch. For pressurized models, you have to remove the dump valve t-handles and securing nuts before you can remove the pedestal cover.

wslade2 · #5 10-06-20, 10:36 PM

Pursuant to Ernie Martin post, I have read with interest information under technical data at this website’s home screen regarding flap cables and inspection.