Assymetric flaps...flap tube joined in a 64 M20E

[Pilot boy]

Commercial check ride coming up soon and my instructor and I were trying to figure out if the Mooney can have  asymmetric flaps as a failure or if they system is generally one long torque tube thru the frame.  IE how does the torque tube interact with the flap hydraulic pump?  Is it one tube or split?  Can one side of the tube shear off like a Cessna?  Can the flaps fail on just one side if you lose multiple of the little push rod nuts? 

[N201MKTurbo]

6 minutes ago, Pilot boy said:

Commercial check ride coming up soon and my instructor and I were trying to figure out if the Mooney can have  asymmetric flaps as a failure or if they system is generally one long torque tube thru the frame.  IE how does the torque tube interact with the flap hydraulic pump?  Is it one tube or split?  Can one side of the tube shear off like a Cessna?  Can the flaps fail on just one side if you lose multiple of the little push rod nuts? 

It is one short torque tube in the belly. It would have to be really broke to be asymmetric. 

[Vance Harral]

57 minutes ago, N201MKTurbo said:

It is one short torque tube in the belly. It would have to be really broke to be asymmetric. 

That torque tube doesn't connect directly to the flaps.  Arms are welded to the torque tube on each side, and those arms drive a pair of connected rod ends, which in turn drive the flap.  See screenshot of parts diagram from the IPC below.  Among other reasons for this design, it allows the flaps to be adjusted independently by turning the rod ends.

Mooneys are certainly less susceptible to asymmetric flap deployment than some other models, and I'm not aware of any Mooney accident reports associated with asymmetric flaps.  But I count four welds/linkage points between the torque tube and the flap on each side, the failure of any one of which would result in that side's flap hanging loose in the breeze.

 

 

 

[47U]

31 minutes ago, Vance Harral said:

I count four welds/linkage points between the torque tube and the flap on each side, the failure of any one of which would result in that side's flap hanging loose in the breeze

Here’s a picture of the linkage that I think Vance is referring to…

 

[Vance Harral]

Yep, that's the one.  It looks slightly different in models with electric flaps, which is why I didn't post a picture from my airplane.  But the linkage is similar in both electric and hydraulic flap airplanes, with roughly the same (low) probability of an asymmetric failure.

[MB65E]

Woah! A new spring and SB!! 
-Matt

[Immelman]

One other thing to point out, the rod end bearings (2 on each side) are wear items where the fastener passes through them. Periodically these need to be lubed/inspected for play/replaced.... there are quite a few in a Mooney, nose to tail. I would imagine uneven wear L/R could cause a slight flap asymmetry.

Edited November 12, 2021 by Immelman

[larryb]

Yes, it can happen, and it happened to me.

 

It was my first day of transition training on my new-to-me '84 J model 10 years or so ago. 2nd or 3rd takeoff, flaps up, feel a strong roll tendency. Look, out the window and tell my instructor we have an asymmetrical flap situation. He didn't believe it, but it was true. It wasn't hard to control and I never felt we were at risk of an accident.  We cycled flaps but no improvement. The next day we flew flaps-down off to the local MSC. They had never seen it either. At the end of the day, and a couple repair attempts later, it was found that the flap skin had come up slightly and was catching in a wing skin in the wing root area. Probably caused a ton of torque on the system, but nothing else seemed damaged. The repair was to bend the skins back and apply teflon tape.

 

Larry