Engine Starting 101 – When Flames Appear

Yep, you read that right, flames, as in FIRE (which is never a good word around an airplane fueled with any kind of AvGas) around your airplane when you are trying to start the engine. If you haven’t seen this yet, be wary, because all it will take are the right circumstances, and you not only can see this type of event, YOU WILL.


Here is the set up – the pilot tries to prime the airplane to get it ready to start. They prime the engine a little too much, resulting in gas getting into the intake manifold through an open valve. The pilot takes the key to the start position, and the engine starts to crank. All that has to happen at this point to have a lot of excitement in the cockpit is that the engine backfires for just a split-second, and the AvGas in the intake bursts into flames. WOOF – the fire that results will be clearly visible in the cockpit to many pilots, and even more visible at night. Are you nervous yet?


Pilots in this situation have two ways to go. They can follow their instincts, let go of the key, and jump out of the airplane. We’ve seen this happen, and in most cases, the airplane either gets slightly or severely damaged, depending on the amount of overprime. Some people can even get killed, since getting out of an airplane on the ramp when the pilot suddenly jumps out can be disorienting if the passengers don’t catch on to the problem. The second way for the pilot to go is for the pilot to go contrary to their instincts and keep cranking the engine. GUESS WHICH ONE SAVES THE DAY (and the plane)?

IF YOU GUESSED ‘KEEPING CRANKING,’ GIVE YOURSELF A PAT ON THE BACK. By keeping the engine cranking, the fuel is consumed and the fire goes out. Conversely, if the engine stops cranking with an active fire, as long as there is air and fuel, the fire will continue to burn. All the fire has to do is burn through the fuel line, and there is a much larger source of fuel available, and since we are in an atmosphere that is around 19% Oxygen, more AvGas means a longer, meaner fire. In a few minutes, (almost always before the fire department can arrive and get suppressants on the fire,) POOF – the flames turn the airplane into a puddle of aluminum and ashes.

WOW – THIS SOUNDS COOL! WHERE CAN YOU FIND THIS SAGE ADVICE? Surprisingly enough, most Pilot Operating Handbooks (POH) contains this advice. Let’s look at the 1985 Cessna 152 Information Manual for example. In Section 3, Emergency Procedures, on page 3-5 you’ll find the start of the details on what to do in the event of fires. The first fire that is dealt with is DURING START ON GROUND, where step 1 is simple: Cranking – CONTINUE, to get a start which would suck the flames and accumulated fuel through the carburetor and into the engine.

If your plane happens to be older, you may not find this advice in your POH. We checked the POH of a 1964 Cessna 182, and didn’t find the same instructions there. However, if you look at a later model’s manual, you probably will find it there, and there is always the regulation that states the Pilot In Command may deviate from FARs in the event of an emergency. If a fire on start isn’t an emergency that warrants deviation, I’m not sure what would be!

ALL THIS, AND (for the most part) YOU CAN FOLLOW THE POH PROCEDURES TOO! Knowing what you have to do in all emergencies is one way you can keep all of our insurance rates as low as possible. By having this information clearly in your mind, you will be ready for the unexpected when it happens, and will know what to do in order to be successful. Take a minute to review your emergency procedures today – they are there to help you keep flying!