Hello everyone, late Merry Christmas and Happy New Year to everyone. Today I want to speak a little bit about electric engine pre-heaters. For those of us who have flown for a while out of airports based where Jack Frost freezes us every winter we are familiar with the need to pre-heat the oil and engine before attempting to start the engine. Aircraft engines don’t like to start when they are cold as most of us know and having that oil warm of course keeps it thin enough to lubricate the engine properly when the engine is started. I wont get into too much detail about the benefits of warming it unless someone comments and wants it explained further. So you may be asking yourself right now why am I talking about this when I stated that most of us know about the benefits? Well I want to shed some light on some aircraft debate I have seen on some aircraft owner pages on Facebook. The question is: “Is it a corrosion hazard to leave my aircraft pre-heater plugged in all the time?”
Well there are a few factors at play. When the engine is running, there is some moisture produced from combustion. There is also some corrosive by-product that enters the oil from combustion. These don’t go away when the engine is shut down. The theory is that, leaving the engine plugged in produces water vapor that will re-condense on cooler engine parts and cause a corrosion problem. The fact is though that there is no evidence proving this. If you ask the pre-heater manufacturers, oil manufactures and the engine manufacturer who to blame well, they will never point the finger at themselves. We leave our aircraft plugged in all the time and haven’t had any issues. Aircraft kept in hangers that fly all the time are at a lower risk for corrosion in general. If your plane is left outside, exposed to wind and varying temperature changes and the aircraft is hardly ever flown then the engine is at a higher risk for corrosion. That corrosion risk is always there with or without the heater plugged in. I have talked to a couple mechanics and they didn’t express any concern about it. One of them did say however that it might be a good idea to remove the oil dipstick when the heater is plugged in. This of course would allow any moisture to escape the engine if it were to accumulate due to the heater. There seems to not be any concrete evidence that leaving the heater plugged in is a bad idea, it’s all just theory.
I hope this blog was a little helpful however I think this will be debated for a long time to come. Remember to follow manufacturer recommendations and also remember that an aircraft that is rarely flown itself without a heater is at risk for corrosion. If you think your aircraft is at risk leaving it plugged in than you can remove the dipstick to vent any moisture that may build up. Remember also to take comfort in the fact that more often than not, your engine will go to TBO without any issues. If you like what you read or have any comments/concerns feel free to drop me an email. Until next time remember to keep the greasy side down.
Flight Operations Manager / Pilot
Winterset Aviation Services