In-Flight Fire – Maybe in the Rear Engine You Can’t See

[Roger]

These messages as related to exhaust leaks (which can among other things cause fires) interest me because I haven't YET had any rear exhaust problems. But I almost did.

I consider my aircraft to be pretty well maintained, yet at the last annual the A&P noted something that had essentially been overlooked for perhaps some time. The two holes in the rear cowling where the exhast pipes come out, had small wear marks in the bottom.

The exhaust pipes were well above those marks, so it wasn't like they were rubbing on the bottom of the holes (while on the ground). But if you put a lot of weight on the spinner you could see the engine go down to a point where the pipes were getting close to hitting the bottom of the holes.

So we decided to measure the distance between the bottom of the pipes and the bottom of the holes, and then replace the motor mounts. The net result was that the motor is now raised about 5/8" at static, and the aircraft is much smoother in flight.

Essentially the rubber in the motor mounts had deteriorated to some degree (probably softened) and it allowed the engines to move around a bit (and enough to allow the exhaust pipes to hit the edge of the cowling holes). I can't help but feel that this type of movement and rubbing on the cowling in flight could cause cracks in the exhaust.

So I might recommend that everyone check this by just looking at the exhaust pipe holes in the rear cowling.

[jchronic]

So to ask the specific question: Does anyone know of an off-the-shelf fire or heat detector system suitable for installation in the 337 rear engine nacelle - either STCed or likely acceptable to the feds via form 337? Is the O2 system suitable (if one could be obtained)?

Joe

[WebMaster]

Do a search, and you will find this.

http://www.337skymaster.com/messages...e+extinguisher

[jchronic]

Larry -

Thanks. I think we may have had this conversation when I inquired before. One responder in the thread you referenced has extinguishers, and the guy with the O2 has a detector system. I'm less interested in an extinguisher than in a detector system, and whether anyone is aware of a system that be can put in a straight 337. I'd assume the O2 system could be adapted (or probably even be a straight drop-in), but are any even available?

Joe

[Skymaster337B]

Ernie, I'm curious about the "data of in-flight fires" you mentioned? I haven't heard of any Skymasters with rear engine fires, especially that ended in disaster.

It certainly would be nice to have a fire detector on the rear engine, but I can't image that Cessna didn't consider this. Maybe fire can't be sustained at normal cruise speed because of all the air going thru that rather large air scoop on top of the fuselage. Or maybe air flow is reversed (as it does in so many unpressurized cabins) that you would smell a fire. I guess we need to hear from some one who actually had a rear engine fire...and what they experienced. Don't get me wrong, extra safety equipment is nice to have, but let's not scare the crew.

[hharney]

Returning from the Bahamas in 2007, we had just attended the SOAPA event. Larry and I were flying with Jerry in his G model P337. We were on the first domestic leg from Ft. Pierce to a small airport in Southern Kentucky (can't remember the name now). I was in the rear and I was hearing some kind of knock or something. I had mentioned that I thought I heard something but Larry and Jerry didn't seem to hear it yet. Again, we are at Flt Level 100, we all have headsets on, in one of those noisy Skymasters and it's a pressurized cabin. I am hearing some kind of noise that is coming from the rear or bottom of the plane.

All of a sudden a loud quick knock gets the attention of everyone in the cabin. See I told you I heard something, I thought. Within a few seconds I could smell oil, burnt oil or hot oil. Jerry immediately called center and said that we needed down now. Center told us that Athens, GA was just a few miles on right and told us to squawk 1200 and call Athens. Ok, just drop us then. Anyway, one of the bolts for the rocker arm broke and the rocker made a hole in the cover. You will have to search the SOAPA Bahamas thread to see the photos and story about the amazing repair that day, in Athens, on a Saturday.

You can definitely smell hot stuff in the rear engine from the back seat, right away. We had no fire,

[Ernie Martin]

No, there is no data on any fire in the rear-engine compartment of a Skymaster. My research was generally about in-flight fires in GA aircraft, with two noteworthy findings: how little time between first hint and unrecoverable condition (average 7 minutes), and that the more likely location for a fire in older aircraft is in the wiring behind the panel (hence my suggestions on smoke masks and halon extnguishers).

The points made above that air flow in the compartment may preclude fires is interesting and worth pursuing. Maybe there is no cause for my concern about a raging fire while you keep on flying. The fact that Cessna added fire detection on O2s but failed to incorporate it on subsequent 337 models (G and H) may suggest that Cessna did not deem a fire a likely event in non-combat conditions -- after all, the design was done, so adding it would have had little impact on cost or weight.

Ernie