Cowl Flap Loose

[Ragsf15e]

Today I noticed my left cowl flap is pretty loose on the front “hinge” part.  Although it looks to just be pinned to the cowling on the front left and right with a rivet or bolt - not a full hinge.  The actuator rod on the back has a little play but the inboard front “pin” has a lot of forward/aft play.  It looks like it’s a blind rivet?

Thoughts on fixing this?  I think this is step one of identifying a weird vibration I’m noticing at level off from climb.  Can’t tell yet if it’s related to speed, elevator play or maybe cowl flaps, but the left cowl Flap clearly needs fixed either way.

thanks!

’68 F

[larryb]

My j always let me know to close the cowl flaps at top of climb with a vibration. I did find and replace a number of loose rivets but the vibration remained.

Interesting that in my encore there is no vibration no matter the cowl flap setting. If I forget to close them at the top of the climb I usually remember when I look at the engine monitor and wonder why the temps are so low.

[Ragsf15e]

Interesting.  I wonder why it’s the top of the climb?  That’s exactly what mine is doing.  I gotta figure out how to fix the front attach points on the cowl flap so I can go to my mechanic with a plan.  They are clearly loose.  Maybe @M20Doc will throw me a tip? 

[larryb]

I think it is just the increased airspeed at the top of the climb.

[carusoam]

Feel free to post a pic...

With all the vibration and forces... that hinge must see a lot of wear...

if it wiggles... in your hand... it can vibrate in the wind.

changing attitude is going to vary the forces on it... similar to the stall vane...

I'd post a pic of mine if it would help... but it would attract too much ire... 

Best regards,

-a-

[Guest]

The cowl flaps on early airplanes use bolts and no bushings.  After decades of use the bolts and holes wear out.  The inner bolts are in the air filter cavity, the outer bolts access with the sides removed.  You can fashion bushing from thin wall 4130 tubing to restore the holes.

Clarence

[Ragsf15e]

2 hours ago, M20Doc said:

The cowl flaps on early airplanes use bolts and no bushings.  After decades of use the bolts and holes wear out.  The inner bolts are in the air filter cavity, the outer bolts access with the sides removed.  You can fashion bushing from thin wall 4130 tubing to restore the holes.

Clarence

Thanks Doc.  That’s exactly what it looks like - the bolt going into the airbox cavity is very loose.  It’s hidden behind the oil cooler lines with the side cowl off.  I’ll have to dig deeper.  I’ll get working on a bushing.

[Ragsf15e]

19 hours ago, carusoam said:

Feel free to post a pic...

With all the vibration and forces... that hinge must see a lot of wear...

if it wiggles... in your hand... it can vibrate in the wind.

changing attitude is going to vary the forces on it... similar to the stall vane...

I'd post a pic of mine if it would help... but it would attract too much ire... 

Best regards,

-a-

Maybe even better than a picture..

https://photos.app.goo.gl/jtVUC3qmTsYYbR23A

Google video if it works.

[carusoam]

Way better than a pic, Rags!

According to Doc’s drawings...   it looks like only two screws holding the front of the flap in place...

To have that much motion... the screws may have come loose, or the holes they are in may have worn larger...

See if your mechanic has a fresh set of hardware to swap in there... and get a good look at the shape of the holes...

taking up the excess play should change the way it behaves...

Your mechanic will have the ideas for a proper long term fix if the holes have grown...

PP thoughts only, not a mechanic...

Best regards,

-a-

[madjano]

Thanks Doc.  That’s exactly what it looks like - the bolt going into the airbox cavity is very loose.  It’s hidden behind the oil cooler lines with the side cowl off.  I’ll have to dig deeper.  I’ll get working on a bushing.

You can get the new doubler from lasar, I had mine replaced when I bought it. I was shocked when the previous owner mentioned how much the little piece of aluminum cost. Pretty sure you could fabricate it, but should last another 50 years.

Sent from my SM-G970U using Tapatalk

[Tcraft938]

On ‎3‎/‎19‎/‎2020 at 9:55 AM, Ragsf15e said:

Thanks Doc.  That’s exactly what it looks like - the bolt going into the airbox cavity is very loose.  It’s hidden behind the oil cooler lines with the side cowl off.  I’ll have to dig deeper.  I’ll get working on a bushing.

This summer when engine was out for overhaul, my A&P meticulously went through the cowl and baffles/dog house making repairs.  He found the cowl flap play to be "acceptable, but we are here, stuff isn't in the way, lets fix all we can now and make sure things fit right and proper alignment".  Strip the engine mount check the welds an powder coat.  Then over to the lathe he went to make bushings for the cowl flaps, or I should say he did one and then supervised me making the other three.  Most A&P in my area hate Mooney, but he likes it.  "everything on this plane is done for good reason, save weight, speed and efficiency, I can live with that, I can't stand (another manufacturer known for a candy bar wing :-) cutting corners just to be cheap".  He restored a MIG 17 to airworthy and apparently the M20C "is a ballroom of space compared to the MIG".  I'm very appreciative of his time researching and learning the plane and also teaching me things.  More appreciative that he does not charge for learning and preventative maintenance time.  

The cowl flap issue I have to work on now is the cable/wire broke a few inches above where it attaches to the mechanism.  It had a little T-handle and push button mounted under the panel.  Friend's is 2 years new 20C and his looks like an old Cessna mixture control.  I doubt either one are original.