Cowl Flap closing

[zerotact]

So,  Buttoning up the plane after a lot of work done,  The cowl flaps aren't closing all the way. Looking at the mechanism it looks like the only adjustment I have is the rod length that connects to the flap itself. As the bar that the rods connect to are rotating to top dead center and then just a bit past.  So the rod length that connects to the flaps is the only adjustment, I say this because the whole from of the plane has been apart and rebuilt and the cowl flaps look equally open but the rods only affect one side at a time.

[Raptor05121]

Is this per the maintenance manual? I believe my C manual calls for 3/4" opening at the fully-closed setting

[jetdriven]

Shorten the rods up until they close flush or max open of 1/2”.  If they’re 1-2” open they buffet and wear out the cowl flap hinges, and also pull the rivets they are attached to the cowl with. . On the early J models it’s a real job to repair those. I ended up replacing all the fiberglass in that area, the cowl flap frames, and hinges and added a replaceable bushing in the hinge. Probably 30 hours of work. 

[zerotact]

The cowl flap itself was mostly original but the all the rest of the metal is new ... the whole cowling was a complete overhaul 

[INA201]

On 9/25/2018 at 2:36 AM, jetdriven said:

Shorten the rods up until they close flush or max open of 1/2”.  If they’re 1-2” open they buffet and wear out the cowl flap hinges, and also pull the rivets they are attached to the cowl with. . On the early J models it’s a real job to repair those. I ended up replacing all the fiberglass in that area, the cowl flap frames, and hinges and added a replaceable bushing in the hinge. Probably 30 hours of work. 

How do you determine if you have buffeting, just 1/2” or less? Any merit to either 1/2” or fully closed? Thanks

[jetdriven]

Between a half inch and fully closed the Cht is a few degrees, perhaps 20, than fully closed. 

I don’t know how to determine where it buffets, but do a run up with the cow flaps open fully and watch them. They move around quite a bit, and they flex the cowl and wear the hinges and flex the frames which cause cracking. Fully closed or nearly so, the cowl flaps are braced by more than the three pivot points. 

[zerotact]

I disconnected the rods and it was quickly evident when I tried to close  them...  the new metal was not notched out to clear the exhaust....  

[Piloto]

The gap shown on the picture is about right. A fully closed  cowl flap will increase the temps in cruise and climb.

José

Edited October 4, 2018 by Piloto