STC for mogas required?

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digits_
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STC for mogas required?

Post by digits_ »

Hello,

Assuming a certified privately registered and operated airplane, would one need an STC to burn mogas? I initially thought you did, but I discovered this service instruction from lycoming, approving some car fuels to be used: https://www.lycoming.com/sites/default/ ... 0Fuels.pdf

If your engine is on that list, can you just go ahead and burn mogas legally? It's probably a strong indication it will run, but I am asking from a legal point of view.

Assume no STC for your airplane exists. What is the cheapest way to get your airplane, with an engine on this list, certified for mogas use?

Thank you all!
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PilotDAR
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Re: STC for mogas required?

Post by PilotDAR »

Mogas use is applicable (or not) to the engine, and airframe independently of each other, so the certified aircraft type, and certified engine installed must both be expressly permitted to use Mogas, before you can. That expressed authority will be found in one of three places only: The type certificate for the airframe, and for the engine, an STC for the airframe and the engine, or, in a very limited way, Transport Canada's document TP10737, which contains blanket authority for a couple of types.

If you're flying a certified aircraft on Mogas without one of these authorities, it's not legal, and may not be safe.

It is possible that one of the airframe or engine may use Mogas (by TC/STC), but not the other, in that case, don't. I have tested a couple of types for which Mogas use was not safe - vapour lock (airframe) or detonation (engine).

Peterson is a source of Mogas STC approvals.
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digits_
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Re: STC for mogas required?

Post by digits_ »

Does that mean that service instruction from lycoming is pretty much useless? Or does it count as permission on the engine side of things?
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photofly
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Re: STC for mogas required?

Post by photofly »

digits_ wrote: Sun Sep 13, 2020 11:07 am Does that mean that service instruction from lycoming is pretty much useless? Or does it count as permission on the engine side of things?
It's pretty useless. The Type Certificate Data Sheets for both the engine and airframe will specify which fuel is to be used; to use anything else you need an STC for both.

The engine manufacturer may say that a different fuel is ok, but that doesn't constitute permission from the government to use that different fuel.
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tazin river
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Re: STC for mogas required?

Post by tazin river »

As far as I know, none of the existing MOGAS STC are valid if there is ethanol in the fuel and it is getting increasingly difficult to find alcohol free MOGAS....something to consider too....
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digits_
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Re: STC for mogas required?

Post by digits_ »

Thanks everyone!
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PilotDAR
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Re: STC for mogas required?

Post by PilotDAR »

Correct, ethanol must not be present in Mogas. So far, at least in Ontario, premium auto gas does not contain ethanol. Each time I have my tank filled, I check, so far so good.
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