Steel AN fittings - some questions - Page 3

Noah · #21 03-04-2010, 10:33 AM

Quote:

Originally Posted by L.Adamson

What I'd really like to know more than anything, is statistics or testing of a FWF engine/compartment fire in which the fuel (100LL/Mogas) has been removed after a few seconds, but the fire has to be sustained by engine oil, and most likely not atomized, as it is with a modern day oil burner (furnace).

This is an enticing argument, Larry. I suppose that one strong possibility for a persistent oil fed fire results from installations with CS props, where the prop governor line or a fitting thereon fails (Hence the Lycoming AD to remove any and all aluminum fittings in this line). You can shut your fuel off killing your engine, but your prop governor is going to keep pumping oil out of your engine unless you can get your windmilling prop stopped - quite difficult to do, as I recall from those who have tried during flight test with engine in cut off. I think it is quite easy to imagine a loose fitting making a nice fine oil mist which would combust quite readily and with maximum heat potential, not unlike the oil burner in my basement.

I would not assume that shutting off fuel valves will automatically diminsh or extinguish all petroleum fed fires.

jrs14855 · #22 03-04-2010, 11:15 AM

I think it was Reno 2008 that one of the Sanders Sea Furies blew the engine and had what looked like a bad fire. The flames looked like they reached half way back to the tail. I got a chance to look at the airplane afterwards and listened to the pilot who was C J Stevens. He was amazingly casual about it, said "it was just oil-no big deal" I did not even see any burned paint on the side of the airplane where the fire was. Home heating oil is a kerosene related product-much different than engine oil.

DanH · #23 03-04-2010, 11:37 AM

No statistics to back it up, but I'd venture the most common cause of oil fires is engine case rupture. We've all seen the photos; seems like most connecting rod failures knock a hole in the case.

This from the NTSB report on what is perhaps the best known RV8 inflight fire:

Metallurgical examination revealed that the #2 connecting rod fractured in two places due to fatigue at the rod end resulting in release of the rod from the crankshaft......Post-crash examination revealed holes in the upper engine case and disintegration of the #1 piston.

A case rupture or a failed oil line will pump the entire contents of the sump into the fire unless you manage to stop the prop. The only exceptions would involve an inoperative oil pump.

The fire itself would be forced-draft. Air velocity would vary with location as it passes through the engine compartment, ranging from roughly 1x to 0.2x aircraft velocity. Aeroshell 100W has a flash point of 548F. I'd guess surface temperature of the exhaust pipes at the ports would be around 1200F. That would also be location of the lowest air velocity, so it wouldn't be like lighting a match in a windstorm.

NDrv8r · #24 03-04-2010, 12:06 PM

I'm thinking steel firewall fittings.

My only experience with in flight fire is a friend of mine who took off, pulled the power back on a R182 on downwind, heard a back fire, and almost immediately had evidence of fire. He turned the fuel off, but in his haste, he missed the detent and fthe fuel flow continued.

As soon as he realized he had a fire he dived at the runway and landed right in front of the fire station. As soon as they landed he and his passenger bailed out. The only injury was scraped knees from tripping over portable intercom wires. The fire dept had the fire out in seconds. the floor aft of the firewall and the passenger door were burned through. The fitting was cracked on the fuel inlet to the carb.

Any thoughts on adding stainless in the cowl air outlet area???

RV8R999 · #25 03-04-2010, 12:26 PM

I think all these posts are making a stronger point for adding a fire supression system rather than which type of fitting is better.

Low Pass · #26 03-04-2010, 12:38 PM

Fire prevention is my key with these small planes. If a big (fuel or oil) fire breaks out - particularly in the cockpit, you're screwed. Use a parachute.