Fuel lessons

I learnt something new about filling up with Avgas at Kasane International Airport, Botswana. Usually our Sling takes 95 unleaded car petrol which I get from our local petrol station and fill up the tanks by syphoning the fuel out of containers. Car petrol is not generally available at airports when we travel though so we have to get Avgas (Aviation Gasoline) from the tanker or bowser at the airport. This is a higher grade fuel and is not good for long-term use in our planes and also pumps much quicker with the electric pump.

Half-full

I usually pop the fuel cap on quickly after refueling to stop any dust or impurities getting in while the cap is off. The next morning after filling the tanks at Kasane I checked the fuel level and was shocked to see that the one tank had dropped by nearly a third. The lesson to be learned is that if the tank is filled very quickly, the fuel does not have enough time to drain through the buffer compartments in the tank so it looks like the tank is full, but if you wait a bit for it to drain through the level drops significantly. Fortunately I had enough fuel for the next leg and James drained an extra 40l out of his tank at Victoria Falls for me.. but I will remember to wait in future and recheck the level before assuming the tank showing full is actually full. No one wants to run out of fuel on a long 4 1/2 hour flight with not many alternative airfields around.

Refueling with Avgas at Kasane taught me a new lesson