Cowl flaps will not stay closed

[75_M20F]

Anyone have this issue? How did you resolve it?

My cowl flaps will not stay closed at higher cruise speeds. The air pressure is forcing them back open. My mechanic put a stronger spring on them to help, but they still open. Has anyone had this issue?

My F has all M20J parts operating the cowl flaps + the Lopresti STC cowling with larger cowl flaps then a stock J would have.

 

 

[201er]

4 minutes ago, Mooney_Mike said:

Anyone have this issue? How did you resolve it?

My cowl flaps will not stay closed at higher cruise speeds. The air pressure is forcing them back open. My mechanic put a stronger spring on them to help, but they still open. Has anyone had this issue?

My F has all M20J parts operating the cowl flaps + the Lopresti STC cowling with larger cowl flaps then a stock J would have.

 

 

Did you just say you have a Lopresti cowl but the Lopresti cowl flaps replaced with the original aluminum Mooney ones? Could that be causing the issue?

When I got my J, it came with a throttle with friction lock for controlling the cowl flaps. Previous owner complained about them getting sucked open as you did so they did a lame fix by putting a friction locked throttle in place of the cowl flap lever. Sometimes the locking friction was enough and sometimes it wasn't. It wasn't till I had it replaced with a new, ridiculously expensive, long cowl flap knob and cable that it operated properly. Perhaps you need a new longer cable.

[75_M20F]

25 minutes ago, 201er said:

Did you just say you have a Lopresti cowl but the Lopresti cowl flaps replaced with the original aluminum Mooney ones? Could that be causing the issue?

When I got my J, it came with a throttle with friction lock for controlling the cowl flaps. Previous owner complained about them getting sucked open as you did so they did a lame fix by putting a friction locked throttle in place of the cowl flap lever. Sometimes the locking friction was enough and sometimes it wasn't. It wasn't till I had it replaced with a new, ridiculously expensive, long cowl flap knob and cable that it operated properly. Perhaps you need a new longer cable.

The cowl flaps are Lopresti as part of the STC they are made of fiberglass / carbon fiber. The cowl flaps are larger then stock J cowl flaps it appears. They seem to be overpowering the mechanism designed to keep them closed once I accelerate in cruise. If I put a small amount of pressure on the cowl flap control knob it is enough to keep them closed....

I am thinking maybe temporarily put a plastic clamp on the cowl control knob until I can get this solved.

 

Edited August 2, 2017 by Mooney_Mike

[carusoam]

Clean and adjust, or replace the friction lock parts.  There are a few friction locks in planes.  They age terribly.

A mechanic can probably disassemble and clean or replace the parts easily.

Lopresti was a brilliant engineer.  He probably wouldn't leave you hanging.

His company still exists if you need some parts(?) http://www.loprestiaviation.com/aerodynamic-mods-5/mooney-m20.html

The forces on the cowl flaps are gigantic at speed. Getting them rigged properly with the proper hardware will be your lowest cost.

Did the cowl come with any maintenance instructions?

Best regards,

-a-

[peevee]

we had a worn out linkage, it was expensive, like $300 but it's been fine since. Looks like a pretty intricate system, I'm sure no two cases are the same.

[75_M20F]

Linkage is new.

[N201MKTurbo]

Do you have a picture of the linkage? Mine has a series of bars and levers that is pretty clever. It has two stable states opened and closed. You can put it between and it will be "in trail" You may have to re-rig the cable adjustment and rod lengths to get it into the stable closed state.

[KSMooniac]

It is very likely mis-rigged, or has the fuel line impinging on the travel and not allowing it to get over center.

Sent from my LG-US996 using Tapatalk

[jetdriven]

often its the cabin air heater hose. The mechanism drags over this and rips a hole in the hose. you can hold it away from the linkage with a large Adel clamp over the #3 intake tube and a zip tie around the hose. then safety wire to hold them tight enough to keep the hose off the linkage.