All you folks with ram air, check those ram air door seals!

[Vance Harral]

Last July, @chrixxer graciously shared a "never again" story about foreign material in the intake of his M20F here:

Mooneyspace collectively identified this as a portion of the ram air door seal.  I got an uneasy feeling when I read the story, because we've never replaced the ram air door seal in 15 years of ownership.  In fact, there's no record of ours ever having been replaced in the logs, and I think there's a good chance it's original from 1976.  Last fall, I took a close look at the seal, and it definitely showed signs of cracking.  I made a note to look at replacing it during the annual this spring, and ordered a new seal from LASAR a couple of weeks ago.

So... we removed the ram air door yesterday, and found this:

Here's what it looks like after drilling out the rivets and removing the aluminum plate "sandwich" around the seal:

New seal from LASAR was only about $60, and I got to practice my riveting skills:

It's not difficult to remove the door.  Just remove the air filter, pull the ram air knob to open the door, and remove the three screws that secure the actuating plate to the door itself.  After doing so, the door slides right off the actuating plate, and can be pulled out the front of the cowl.  Yes, you have to drill out the old rivets and install new ones, but I'm a total noob at this, and I managed to do it without damaging anything  (I only had to re-do 3 of the 9 rivets. ).

For those of you with the ram air door - whether you use it or not - strongly encourage you to take a look and consider replacing the seal if you haven't done so in a while.  When you get to looking at how the assembly goes together, it's pretty obvious that if a piece of the seal comes loose, it just goes right into the fuel servo.  At $60 for the seal and maybe 1-2 hours of labor for a professional (it took me about four with adult supervision), it's cheap insurance against a potentially catastrophic failure.

[RLCarter]

3 rivets? IIRC there are 3 that have to go on because once assembled you can’t get to them. Well done!!!!

Edited April 4, 2019 by RLCarter

[MB65E]

I didn’t know the original piece was that big. I replaced mine and cut it at the hinge line. 

Nice work. 

-Matt

[Immelman]

Thanks for detailing this job, and nice work shooting those rivets, this is something to take a look at.

[carusoam]

Great post with pics and all!

also looks similar to the heater control valve on many modern Mooneys... after the slide gates were eliminated...

Thanks, Vance.

Best regards,

-a-

[Vance Harral]

22 hours ago, RLCarter said:

3 rivets? IIRC there are 3 that have to go on because once assembled you can’t get to them. Well done!!!!

I should clarify.  When I said I only had to re-do 3 of the 9 rivets, I meant that I replaced all 9, but I botched 3 of the replacements, and had to drill them out and start over.  So I actually placed 12 rivets total. 

In addition to the rubber seal, the ram air door consists of three pieces of metal: two flat "sandwich" plates, and a third dimensional piece of metal which captures the actuator plate.  RLCarter is correct that you have to drive an initial set of 3 rivets to fasten just the two the "sandwich" plates around the rubber seal, then the final 6 rivets go through all three pieces of metal.

 

[RLCarter]

1 hour ago, Vance Harral said:

I should clarify.  When I said I only had to re-do 3 of the 9 rivets, I meant that I replaced all 9, but I botched 3 of the replacements, and had to drill them out and start over.  So I actually placed 12 rivets total. 

Can't remember how many I had set when I realized they had to come out to set the ones under the demensional piece. 

[Boilermonkey]

Looks really similar to the flap for carb heat on carburated models....makes me think that should be checked too!