Welcome Guest. Sign in or Signup

1 Answers

How to be certain fuel sample isn’t all water?

Asked by: 2275 views , ,
General Aviation, Private Pilot

Often the 100LL fuel at my airport is so lightly tinted that it does not appear blue. I sump multiple times and smell the fuel. Still I'm sometimes unable to see a blue tint and I'm concerned I'm looking at all water. 

Is is there a way to be certain it's fuel and not all water I'm looking at? Perhaps I could add a little water to the sample to verify the difference from the fuel?

 

Thanks

Ace Any FAA Written Test!
Actual FAA Questions / Free Lifetime Updates
The best explanations in the business
Fast, efficient study.
Pass Your Checkride With Confidence!
FAA Practical Test prep that reflects actual checkrides.
Any checkride: Airplane, Helicopter, Glider, etc.
Written and maintained by actual pilot examiners and master CFIs.
The World's Most Trusted eLogbook
Be Organized, Current, Professional, and Safe.
Highly customizable - for student pilots through pros.
Free Transition Service for users of other eLogs.
Our sincere thanks to pilots such as yourself who support AskACFI while helping themselves by using the awesome PC, Mac, iPhone/iPad, and Android aviation apps of our sponsors.

1 Answers



  1. Skyfox on Jul 11, 2016

    Yes, that’s one way to do it. Water settles to the bottom of avgas like it would with oil, so if you add a couple drops of water to the sampler and see those same drops sitting at the bottom, you know it’s not a cup of water you’re looking at. Another test is to simply splash the sample cup onto something and observe how quickly it evaporates. Avgas will evaporate very quickly, while water would evaporate very slowly (or hardly at all on a humid day).

    One thing you have to be sure of is that it is in fact 100LL you’re getting. The dyes in the various grades of avgas are formulated to neutralize each other and turn clear if they’re mixed. Double check with the FBO that it is in fact 100LL they get at that pump and that they test it before the storage tank is filled. If the fuel supplier is doing the job right, they have a bucket with a white porcelain lining that they dump a sample of their shipment into for inspection by the delivery person as well as the FBO attendant. In that very white bucket, the blue dye of 100LL stands out quite clearly, especially in sunlight. If it was a different grade they should see it very plainly and reject the shipment.

    Those little plastic samplers aren’t perfect for sampling because, IMO, the plastic has a very slight blue tint to it already. Something else you can do is hold up the sample cup with a white sheet of paper behind it to help the color stand out, and maybe even pour it into a clear glass jar if you want to eliminate the possibility of a slightly tinted plastic.

    +4 Votes Thumb up 4 Votes Thumb down 0 Votes


The following terms have been auto-detected the question above and any answers or discussion provided. Click on a term to see its definition from the Dauntless Aviation JargonBuster Glossary.

Answer Question

Our sincere thanks to all who contribute constructively to this forum in answering flight training questions. If you are a flight instructor or represent a flight school / FBO offering flight instruction, you are welcome to include links to your site and related contact information as it pertains to offering local flight instruction in a specific geographic area. Additionally, direct links to FAA and related official government sources of information are welcome. However we thank you for your understanding that links to other sites or text that may be construed as explicit or implicit advertising of other business, sites, or goods/services are not permitted even if such links nominally are relevant to the question asked.