Keeping Tabs on Fuel

The fuel gauges on most aircraft are accurate in two positions-full and empty. In between, the quantity is anybody's guess. That's why the visual fuel check is essential, even when you know that the tanks are full. Given the number of fuel misman-agement accidents that occurred last year, this is a discipline that should be passed on to all students.

Returning from a trip in an elderly Mooney some time ago, I watched line personnel top the tanks. A week later a flight came up in a hurry, and I was running late. I was tempted to skip the visual fuel check. The tanks were full-I was there when the gas truck left and had the bill to prove it. Out of habit, I looked-and the right tank was bone dry! Closer inspection revealed a leaky quick drain, but the fuel had evaporated, leaving no trace on the tarmac.

Sure, the fuel gauge would have shown empty, but the gauges in this airplane stuck occasionally. For me, the bubble of self-delusion would not have burst until the aircraft rolled off on one wing because of the fuel imbalance. It could have been much worse had I selected the dry tank. Murphy's law says there will be enough fuel in the lines to complete the runup and just get airborne before the engine stops.

How do you estimate the fuel in less-than-full tanks? If the manufacturer has put in a tab (a metal bar that extends into the tank), then you've got a measurement. The aircraft should be parked on a level surface-but even if it's not perfect, the estimate will be close.

If the aircraft doesn't have a tab, you need a dipstick. There are aftermarket dipsticks available for a few aircraft. Otherwise, you have to make your own. The calibration process is arduous and somewhat messy. In any event, CFIs, teach your students well about managing fuel and the vital importance of the visual check.

Bruce Landsberg is executive director of the AOPA Air Safety Foundation.