The Cessna 120-140 Association Forum

My Cessna 140 flaps work on the ground but do not work in the air. In the air when trying to extend they do nothing until the last notch or full flaps. As soon as i release the flap handle they retract. Never lock in place. Any ideas?

Pre Flight on the ground , apply full flaps try to push them up and have someone check all the pulleys and attachment points inside.

Check to see if somebody over-tightened the connections between the carry thru tube and the flap connection fitting. It is supposed to be a smooth slip fit to accomodate for the dihedral. The fittings connected to the flaps have an elongated slot for that bolt. Might be some binding there?

It could be your flap handle assembly. The detents in the ratcheting mechanism might be so worn out that there is just enough of a groove to hold the flap in position against the force of the return spring while on the ground with 0 kts airspeed, but once you add 60+ kts of wind force on the flaps, they pop out of the groove, or won't seat in the first place.

The assembly I'm talking about can be found in Figure 15: Fuselage Assembly Complete on Page 28 of the Illustrated Parts Catalog.

I happen to have a 1946 C140 that has the flap handle where you have to twist the handle in order to change the flap (and handle) position. For a while, I thought I had an extra flap setting because I could set it on the ground. But then I could never get the flaps to lock into that "final" position in flight, on approach. It turned out that there was a tiny shoulder on my ratchet gear (probably not the correct terminology), but not a proper flap setting. I eventually figured out that it was aeroloads that prevented the flap from locking into that "extra" position. (Well, that and the fact that they were never designed to do that... )

Although the later models use a different mechanism on the flap handle, the push button instead of the twist, I would imagine a similar situation where the detents on your ratchet are just worn out.

Good luck. Please let us know what you find.

-- Chris B

Thanks Chris, that sounds like the problem. Let u know.

The fittings connected to the flaps have an elongated slot for that bolt.

Those slots get worn, too, and the movement of the torque tube is not transferred to the flaps. The air load takes up the slop by pushing the flaps up.

If this is the case, sometimes you can compensate by adjusting the cable. Set the adjustment to the correct angle with someone pushing up on the flaps.

Thx