Electric cowl flaps on 96 MSE creep open

[gjensen]

Has anyone else experienced cowl flaps slowly opening in flight? I had to close or adjust about every ten minutes on a flight this afternoon. I am at KILM for the night and plan on having someone at Air Wilmington check them out in the morning. Any suggestions, or experience with this problem would be appreciated.

[jrwilson]

I've never ever experienced that in a 1996 MSE... But then I have never flown a 1996 MSE. Never experienced it in my C either. Guess I'm not the target audience of this post.

[Ned Gravel]

Is this where we shut up and let the adults talk? ;-)

Sent from my iPad

[N601RX]

We manufactured the gearmotor for the flaps where I used to work.  I don't remember if it had a brake on it or not, many of the motors we manufactured did.  If it did, then it may have got some oil on the disk. If it doesn't have a brake, then it may have been used enough that it has loosened up and the backdrive torque has been reduced to the point it will not hold the flaps out. Generally a thicker grease in the gearbox increases the amount of torque necessary to backdrive a motor.  I'm not familiar with how Mooney used it in the application so its possible they put some friction device in the system also.

[LANCECASPER]

Cowl flap motors in later K models (252, Encore) have been discussed before. (I think the MSE/Allegro use the same set-up.) There is an up limit switch that may not be working properly or it may be time to rebuild the cowl flap motor. The topic below starts with not-so-good news but a solution is eventually found.

 

http://mooneyspace.com/topic/8315-m20k-252-cowl-flap-motor/

[Ftlausa]

My cowl flap motor is being rebuilt by Globe right now.  Estimate is about 2 weeks for overhaul and 4 to 6 weeks for new motor to be built.  After searching for days, we found a new one in France, but opted to go with rebuild since the motor was already at Globe.  You might want to check the limited switch, as that is what cause my failure.  The limiting switch failed and the drive shaft sheared off on the motor.  M20J MSE 

[gjensen]

Thanks for the info, the limit switch is where the mechanics said they were going to check first.

[PeytonM]

I've had the same issue on my 89J. They trail about 1/4 open. Limit switches all adjusted properly to no avail. I have a suspicion it's the motor, but I have no desire to have it rebuilt. I did have it rebuilt about 10yrs/1000 hrs ago. Since all temps seem good, I guess I'll just deal with loss of a knot or two!

[fantom]

Has anyone else experienced cowl flaps slowly opening in flight?

 

How far do they open if you don't close them every ten minutes, Gary? If they stay in trail, maybe just let it be.

 

Have you uncowled and checked the motor? It may be oil soaked. Mine was. Cleaned it up and no more problems.

[gjensen]

They will open all the way if I do not adjust, motor was loose, I am flying this afternoon to see if problem is resolved.

[Releew]

Check the position indicator cabeling. I have a 92mse and it will bind. Rick

[Ftlausa]

A thumps up for Globe in rebuilding my cowl flap motor.  It took longer than I would have liked, and we had a little shipping snafu, but the motor looked like new when it finally arrived. 

[jetdriven]

The aerodynamic force on the M20J cowl flaps will force them in trail, but the trail positon is only actually about 1/3rd open.  Its still a loss of 3-4 knots though, and a distinct rumbling in the floor accompanied by a hiss and loss of cabin heat.

[fantom]

I usually have my electric cowl flaps in trail and lose less than one knot, a lot less.

With the cowl flaps wide open the loss is about three knots in cruise.

[fantom]

Why do you usually have 'em in trail, Gary? Cooling issues? FWIW, I can't detect a speed loss at all in trail, although I rarely have them there. There is a detectable speed loss with them wide open, however.

In the J at least, it seems to me that electric cowl flaps were a solution to a problem that didn't exist.

Jim

Same experience, Jim.

Ever since two Mooney's at my home base exhibited serious chaffing of their flap from either rubbing on or just being too close to the exhaust pipe, i've made a habit of keeping them in trail.

As you say, no speed loss and while I don't have a cooling issue, if they cool things off a bit more, I'm not complaining.

[jetdriven]

My J has 5000 hours on it, and a friend's J has ~3500.  Both have signs of the cowl flap doubler bracket pulling the rivets through the fiberglass. I'm not sure leaving the cowl flaps in trail will do this, but locking them open in flight certainly will. The fix isnt cheap, nor easy. And I am not sure I've seen a qualified repair on one yet. MIne currently has #6 screws, nuts, and tinnerman washers all down both sides of both cowl flaps, and they are smoking, full of oil and generally falling apart.

 

You must grind away the complete periphery of the fiberglass opening in the bottom of the cowl, and rebuild all the glass again. Then drill new holes and buck new rivets.  If you use polyester boat resin and fiberglass cloth from the boat store, it will last 500 hours. It takes real structural aircraft epoxy, such as MGS, and S-glass or E-glass.