Getting a Good Fuel Sample when Sumping

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    • #1561
      Roscoe Rosché

      A Cheetah with the normally horse powered engine came in and he was running Mogas in one tank and 100LL in the other. This is since we are near the time when winter fuel is in the tanks of the gas stations and we have a few warm days (it was 75 F here today), so to prevent vapor lock, he takes off and lands on the 100LL and burns Mogas in cruise.

      As he prepared to leave I saw his fuel sample and it was tan, so I asked about which tank had 100LL (he had told me the other tank). So I got a pint jar and took this sample. Yep, that is water, not Mogas with 100LL floating on top. Fuel and Water small

      So I told him to check his scupper drain (may be cracked letting rain into the tank (we had a bit the other night and he does tie down outside), the scupper could be debonded or his cap does not fit tight (not a 1979 AA5A).

      The moral of the story is to check you fuel well.

    • #1598
      Shannon Stebbens

      First and foremost, thank you for posting the graphic photo of the fuel sample. This is a great example of a picture telling the story better than words.

      I have witnessed this before, albeit not in a Grumman but rather a King Air. I noticed the fuel sample looking odd; it was in a quart canning jar. Continued draining and after more than a gallon of water was removed, a good fuel sample was obtained. I have only seen this once in 40 years but one time can be catastrophic.

    • #5350
      Dennis Cheever

      This brings up a question I have. We have a tank drain and a sump drain. Why? Isn’t the sump drain lower, therefore where the water will actually collect? Has anyone found water at one and not the other?

    • #5359
      Roscoe Rosché

      In the original planes they sat in a much more level attitude. In flight that wing sump is at the bottom. I have opened several planes (4-place) that have been completely drained of fuel and still had a good 1/2 gallon in the back inboard corner, usually with a little water and debris. In the case of a ’79 Tiger with the flush caps, not well maintained, a lot of water.



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