My mechanic showed me something that may be an issue, but neither he nor I know enough about the Musketeer yet. I have a Super III. From the outside, looking at the gap where the cowling and firewall come together, there is a crack in what looks like some kind of lamination or seal of some kind. Does anyone know what this is, or how the cowling is supposed to be attached to the firewall, and if it being cracked is a problem?
All of the rivets on the firewall are OK, and the engine mount bolts should hold the cowling on to the firewall. But I’m just not sure if this needs to be glued back together or what…
Bob Steward, A&P IA
The whole firewall comes off if you remove the bolts for the engine mount. There is a layer of non-hardening putty between the firewall and the first fuselage former. I bet this is what you are looking at. After 30-40 years it has formed a skin that has dried out and cracked. The putty underneath is probably still pliable.
Don’t be too harsh on your mechanic. Very few mechanics still in business today have had the firewall assembly off a Musketeer. I’ve got pictures of the firewall removed if either you or he have questions about what it looks like under that putty.
There is a fireproofing compound available from Aircraft Spruce (or it used to be; I could not find it in their online search). It is known as “firewall caulk”, and can be used to seal gaps and joints in firewalls.