28/06/25 - Nutplates on firewall recess - 3h
Hanging the engine comes closer and closer. I started investigating what other things I was missing on the firewall. Once the engine hangs, access to the firewall becomes extremely difficult. You can off course always drill from the inside but getting a rivet gun in there is difficult.
One of the things I discovered on the plans were some nutplates at the firewall recess top line which will be used to attach adel clamps that hold the oil pressure line to the transducer block. I noticed the I had already drilled the holes to AN3 #12 size but didn't make the nutplate ears yet. These are one leg nutplates so I used the nutplate as a template to drill the holes. As usual, slow rpm on the stainless steel drilling and a sharp drill bit.
After drilling, I used the countersink cage to make the countersinks for the AN423AD3 rivets.
Dimpling is no longer possible here as the firewall angle on the other side is rivetted. I asked the question to Vans and they confirmed just to countersing through the firewall plate into the firewall stiffener angle behind.
Other side of the recess, same procedure.
There is another nutplate below the recess in the vertical rivet line. This will be used to hold the FF-705 breather tube as indicated on OP-27 plan "oil system".
On some airplanes the hole is also used for the engine ground strap. I'm planning to go to the ground block with the engine ground cable.
Squeezed the nutplates on. This was easy as the pneumatic squeezer could be used.
Then I countersunk the other nutplate
and used the rivet gun to set them.
Another step closer to finalising the firewall layout and hanging the engine