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Good to the last dropGood to the last drop

In the “good news, bad news” department, we find the following: Over the past 20 years, the number of fixed-wing accidents blamed on deficient fuel management has dropped by more than half, from almost 200 a year in the early 1990s to a low of 75 in 2008. This represents a real improvement—the decrease has been much faster than the general decline in flight activity, which is the chief reason we’ve seen fewer accidents overall. In the 1990s, about 11 percent of each year’s accidents were caused by fuel mismanagement. By the late 2000s, it was more like 6 percent.

And the bad news? Well, we’re still losing six or seven airplanes a month (not to mention the occasional helicopter) to completely avoidable operational errors. It’s hard to imagine that’s the best we can do, and hard to see it as an acceptable cost of doing business.

Not surprisingly, the bulk of these happen on personal flights—more than three-quarters, about the same as for GA accidents in general. But the fact that flight instruction ranks number two is surprising, or should be. It’s a distant second, to be sure, but 10 percent of all fuel-management accidents—289 of 2,867—took place during training flights, an average of almost 15 a year.

Doesn’t sound so bad? Well, stop and consider: More than 40 percent happened on student solos. While both good professional practice and the PTS require teaching students to make close calculations of fuel requirements as part of their flight planning, that’s not sufficient reason to send a student off with tanks that are less than full. Topping the tanks before and after the flight is the most accurate way to calibrate preflight estimates against the actual burn. Weight and balance aren’t usually a problem, and sooner or later the tanks will need filling anyway. Why not do it first? Even if the flight is running late, we don’t want students getting into the habit of thinking of fuel as something they can skip when they’re pressed for time.

To be fair, students are students because they still have a lot to learn, and their record shows it. Eighty-five percent of their fuel-management accidents involve complete fuel exhaustion, generally due to poor flight planning. What’s really hard to understand is that the majority of fuel-management accidents on instructional flights take place in the supposedly watchful presence of a CFI. About 55 percent occurred during dual instruction, which clearly should not happen. Anyone who’s passed the written, oral, and flight tests for the private, commercial, and flight instructor certificates can fairly be assumed to have learned how to calculate fuel requirements, check and verify the quantity on board, and monitor fuel status during flight, not to mention understand the importance of maintaining adequate reserves. If it’s hard to see why any pilot would risk running low on fuel, it’s downright baffling in the case of an instructor who’s not just responsible for the student’s safety but for teaching all the elements of planning and watchfulness that contribute to the safe conduct of any flight.

Complacency probably enters into it, especially if you know the airplane and know (or think you know) how much it’s flown since its last refueling. Who wants to keep clambering up and down the struts of a Cessna 172? Instructors also have been known to put a little too much faith into a student’s ability to eyeball the quantity in a partially filled tank, a skill that’s harder to learn than most newcomers think. If the engine’s still running after you’ve taxied back to the ramp, it’s natural to assume that your estimate was good enough. So by and large, there’s only one way to find out it was wrong.

The data provide some evidence that CFIs are better at estimating fuel requirements than their students, but it’s of a distinctly left-handed variety. Fuel starvation accidents caused by errors in configuring the aircraft were almost four times as common on dual flights, and while a handful involved twins with auxiliary tanks and multi-position boost pumps, most were simple mistakes in setting a single fuel selector valve. There are models—low-wing single-engine Pipers come to mind—in which it’s difficult for an instructor in the right seat to move or even see the valve, but this doesn’t explain why it ends up in the wrong position more often when there’s an instructor there to ask about it. Could this detail get lost somewhere between the student’s trust in the CFI and the instructor’s focus on the lesson plan?

ASI Staff

David Jack Kenny

David Jack Kenny is a freelance aviation writer.

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