Oil and exhaust pipes

(I posted this in the mechanics forum on flightinfo, then realized that Doug added one here too, so... I guess I'm a little slow)

How much, if any, risk of fire is there if engine oil is seeping, leaking, spraying, oozing, spattering, or otherwise coming into contact with red hot exhaust pipes in flight? How much would it take to create a real risk and/or cause a fire? Say on a TIO-540 for example. Just curious. Thanks in advance!

what your talking about is called FLASH POINT. This is a temp that the oil begins to give off vapor and has the ability to ignite. Regardless of viscosity, the flash point of oil is about 400-450 F. ( that's what I read anyway )

Right, but what I want to know is what it would take to actually ignite the oil, or create a substantial risk of that happening (or if it's even possible). Just because a temperature is higher than the flashpoint of a given substance doesn't necessarily mean it will ignite.

right, but that is the temperature ( I believe ) where it becomes possible. That is the point it is a vapor in the air, and without knowing the exact volume of air in the space of ignition and various factors that flux the concentrations of vapor in the chamber, it would be impossible to determine exactly. You could even go as far as determining the density of oil vapor and comparing that to the ambient air. This difference in density could determine if the vapor even comes in contact with the "flame".

ESF, sounds like you need to upgrade into the 99.

Haha, yeah. Pretty soon! Could be now if I wasn't base-locked until June.

At night you can see the pipes glowing bright orange inside the cowlings. Just something I was morbidly pondering tonight.

Any time you have any flamable substance coming into contact with exaust components it is a problem. If everything with the engine is OK, then you are OK. But the other 90% of the time it's a problem.

The main worry is that an exasust leak could ingnite the oil.

Example:

After overfilling the oil in your Seminole you go flying. The excess oil is vented through the crankcase breather and settels on you exaust manifold and pipes, and every other surface in the cowling. The oil is heated by the hot pipes and gives off flamable vapors. These vapors reach the flange at one of the exaust valves that is leaking. It ignites which quickly spread to the rest of the engine compartment. The fireproffing over the fuel lines which was never properly instaled fails, and the fuel line ruptures.

You now have a gasoline fed fire and have about 60-90 seconds to shut off the source of fuel before either your spar melts in two, or the flames eat through the firewall into the fuel tank, or both.

Did I forget to mention that there is no fire warning system in the PA-44. Your first sign of trouble will be the paint on the cowling blistering, then flames. You have used about 45 of your precious seconds before you can even notice that there is a problem.


Fire is THE biggest danger onboard any aircraft. Nothing else comes close. I constantly hear people talking about how they worry about what will happen if the engine quits, and the FAA requires us to train for it. Yet few CFIs understand, much less teach, how dangerous a fire is.


Oh yeah, the turbocharger in a TIO-540 can reach 16,000 degrees and about 30-40,000 RPM. It's a small bomb under the cowling.

ESF... you in the Chieftain? Have you figured out how to lean with the glow yet? A good plane, but slower than the Barons...

Yes... and no, although I can't say that I've tried, I bet I can guess how.

It's a good plane, I like it. Never flown a Baron, though, which I'm willing to bet is a nicer ride based on the other two Beech products I've flown.

The Baron is like a sports car (of course, ours are pretty beat up on the inside, so think of a classic muscle car that hasn't been restored), the Chieftain is a station wagon...gets you where you want to go but no style, and the Van is, of course, the turbine suburban

I have about 60-70 hours in the Chieftain, so I am not good enough with it to do, but there are some of our guys with significant time in it that swear they can lean it by how much the pipes are glowing.

USMCmech...great to know info. Thanks. Scary to think about some times how stuff can go wrong that we really have no control over. Thanks for giving me a warm fuzzy

TX

Flash point is the temperature at which the material will ignite if it contacts an open flame (ignition source). This is important if there is an exhaust leak (mentioned later) since the exhaust is still burning and therefore provides an ignition source. If there is no ignition source then the temperature of concern is the auto-ignition temperature. This is the temperature at which the material will spontaneously combust.

As a fairly well known example, the flashpoint of paper is well below room temperature; the auto-ignition temperature of paper is 451 degrees F ("Farenheit 451").

ahh yes. thanks for correcting me. hot pipes are not flames.