Cleaning Out Manifold Pressure Guage

[soquetero]

1957 Tri-Pacer, certificated. It has a manifold pressure guage, looks like it came with the airplane. I have no idea why. It's alive, so maybe I ought to learn it against the day I get a complex aircraft. For the present, though, it looks like some bug cocoons have gathered in the bottom of it. Can I legally unscrew the panel cover, attempt to remove the face of the m.p. guage, and clean it out? It really BUGS (sorry!) me. Thanks.

[martymayes]

1957 Tri-Pacer, certificated. It has a manifold pressure guage, looks like it came with the airplane. I have no idea why. It's alive, so maybe I ought to learn it against the day I get a complex aircraft. For the present, though, it looks like some bug cocoons have gathered in the bottom of it. Can I legally unscrew the panel cover, attempt to remove the face of the m.p. guage, and clean it out? It really BUGS (sorry!) me. Thanks.

I doubt it is OEM. I'd also bet it has no installation data, so with that I'd remove it and return the airplane to its original configuration.

[Bob Dingley]

The TCDS for the PA22 shows a whole slew of optional propellers. Ranging from basic wood & metal props through Airomatic props to McCauly CS props. Good chance that it was delivered with a CS and someone removed it, but not the gauge.

[turtle]

To counter uninformed speculation, most Tri-Pacers came from the factory with a MP gauge and a fixed pitch metal prop. Yours would be unusual if it didn't. Just the way Piper did things back then. That's also why you have only three primer nozzles.

The good news is it isn't required equipment per the TCDS. It's not much use as there is little you can do without a blue knob. Legally I don't think you can open it up because it is an engine gauge and theoretically could cause a vacuum leak to the cylinder if something went wrong. A 57 has a restrictor in the line so it would be a very small leak. On the other hand, if you try and bork it up, you can remove the gauge and hose, and plug the cylinder with a 1/8" pipe plug. It's not like your average A&P would notice it missing.

[Kurt Flunkn]

The short answer is no. This is a major repair under FAR 43 appendix A.

[1600vw]

I say it really does not matter one way or the other if you legally can or can't unscrew the cover. Why do I say this. Because I tried to remove the cover on my MP gauge. These little screws must be epoxied into place. I have a gasket coming loose inside my MP gauge and it is now hitting the needle. I tried to remove these screws. Good luck with that.

Tony

[skyfixer8]

There should have been a small filter just before the orifice adjustment screw on the gauge. Even with it missing i don t see how a bug could get in the case unless the case is cracked or the screw is missing.

[soquetero]

Thanks to all. I think I get where this is going. I believe I'll leave it be for a while; ADS-B out's going into the plane next week, maybe those guys can mess with it.