Lessons Learned: Mogas

by Jason Schappert

This weeks lessons learned has no NTSB report as it is a problem the pilot caught early in the preflight.

The pilot of a beautiful 1976 Cessna 182 came out to the hanger and began his preflight as normal. He always had a practice where he would go to the end of each wing and “tip” the airplane. “It’s not in the checklist.” he said “just something I’ve always done.”

This time it proved life-saving. As he did that he heard the fuel slosh around as usual and then he noticed fuel began to leak from the aircrafts inspection plates. Wondering what was wrong he called his mechanic and explained the bizarre situation. Upon arrival the mechanic quickly diagnosed the problem as a leaky fuel tank. However it was due to auto gas.

It turns out Cessna 182’s manufactured from 1956 to 1978 used rubber fuel bladders. Which are perfectly safe for fuel without alcohol. However since the recent addition of ethanol into auto fuel “mogas” the ethanol has been “attacking” anything rubber: engine gaskets, fuel bladders, and fuel caps are the common problem areas.

With problems like this can we still even consider the use of auto fuel?

Tagged as: General Aviation

  • http://www.adamfast.com/ Adam

    “With problems like this can we still even consider the use of auto fuel?”

    Absolutely. An important note is that the most common STC for auto fuel use (which you’re required to have for an aircraft in order to use auto fuel) comes from the EAA – and in many places in the documentation and even placards says the use of ANY auto fuel which contains any fraction of ethanol is prohibited, no ifs ands or buts. It’s likely that this pilot was knowingly operating his aircraft in violation of the POH and its supplements – don’t do that, and you’ll be fine. (it is possible he had a different STC without that language in it, I guess – but I find that case unlikely.)

    Yes, it’s hard to find auto fuel that doesn’t have ethanol in it now in some states (including my home base in Missouri) When you can’t find fuel without it, you have to use 100LL even if it is more expensive. The STC paperwork even includes documentation on testing for the presence of ethanol in fuel with simple tests. Use caution and follow the procedures of whatever STC you’re operating under when using auto fuel – if you do that, you’ll be safe.

  • http://www.adamfast.com Adam

    “With problems like this can we still even consider the use of auto fuel?”

    Absolutely. An important note is that the most common STC for auto fuel use (which you’re required to have for an aircraft in order to use auto fuel) comes from the EAA – and in many places in the documentation and even placards says the use of ANY auto fuel which contains any fraction of ethanol is prohibited, no ifs ands or buts. It’s likely that this pilot was knowingly operating his aircraft in violation of the POH and its supplements – don’t do that, and you’ll be fine. (it is possible he had a different STC without that language in it, I guess – but I find that case unlikely.)

    Yes, it’s hard to find auto fuel that doesn’t have ethanol in it now in some states (including my home base in Missouri) When you can’t find fuel without it, you have to use 100LL even if it is more expensive. The STC paperwork even includes documentation on testing for the presence of ethanol in fuel with simple tests. Use caution and follow the procedures of whatever STC you’re operating under when using auto fuel – if you do that, you’ll be safe.

  • George Weeks

    I have a Cessna 182H with the auto fuel STC. Luckily I have a local source for Mogas without alcohol. However, I recently heard that the toluene in Mogas will also attack the bladders. do you have any information about this?

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