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Crossfeed, wrong feed, or no feed, fuel management is a safety issueCrossfeed, wrong feed, or no feed, fuel management is a safety issue

Fuel mismanagement isn’t a huge headache for the flight training industry. All told, it’s blamed for fewer than 5 percent of all accidents on instructional flights. Of course, just about all of those could (and should) have been avoided—and there do seem to be some systematic differences in who chooses which way to run an engine out of gas.

Student pilots go whole hog. Two-thirds of fuel-management accidents on solo flights involve complete exhaustion. Whether it’s because they didn’t check the tanks before they left, miscalculated fuel burn en route, forgot to lean the mixture, or didn’t adjust their plans in the face of stronger-than-expected headwinds, students are the most consistent in running through every usable drop before the engine quits. (Of course, they’re also more likely to fly aircraft with the simplest fuel systems, many with the attractive option of being able to use both tanks at once.) Occasionally we read about a student who was tripped up by a reluctance to top off away from home. Schools whose policies discourage this—say, by refusing to reimburse for more than the same quantity would have cost at home base—may want to give that a little more thought.

Training flights with instructors on board are more likely to make that forced landing while there’s still usable fuel on board. Why? Maybe CFIs are better than students at figuring out how much fuel they’ll need and making sure they actually start with at least that much. Maybe they’re also more in the habit of keeping an eye on the clock in flight, even sneaking the occasional glance at those notoriously inaccurate fuel gauges. It’s also true that instructors occasionally show the incredibly poor judgment to simulate an engine failure by shutting off the fuel selector. Sometimes the offended engine just decides not to go back to work. In a twin, that’s at least a problem; in a single, it’s an emergency, and it’s not a mistake many students will make on their own.

It’s also true, of course, that step-up training to more complicated aircraft (including twins) with more complex fuel systems is done chiefly in dual flights. That also shows up in the accident record: About half the fuel-management accidents training primary students are due to fuel starvation compared to 70 percent of those during advanced training (instrument, commercial, multiengine, transition training, flight reviews, etc.). However, the role of complexity in these is easily overstated. About 80 percent were in piston singles, the vast majority of which had only two tanks and one selector valve. More common than confusion about which tank still has gas and how to get it connected to the engine is a simple failure to forget to switch to a fresh tank at the appropriate time, usually while both student and instructor are preoccupied with something else (like an instrument approach).

Even in twins, the complexity isn’t necessarily overwhelming. A Piper Seminole has two selector valves, one per engine, with three positions each (on, off, and crossfeed). That’s twice as many as in an Archer or an Arrow, true, but the effect seems disproportionate. In 2010, three of the four training accidents in Seminoles were caused by fuel selectors that were set wrong. Two were inadvertently turned off; in the third, the student neglected to tell her CFI that they’d been flying for the past hour with the same tank feeding both engines because she’d put that selector on crossfeed.

Fuel selectors cause problems in other models as well, particularly singles where the selector valve isn’t readily accessible from the right seat. We noted earlier that students aren’t likely to deliberately shut off the fuel in flight, but they have been known to do it accidentally. Sometimes they leave the valve between detents when they try to switch tanks; sometimes, as in a recent Bonanza accident in Texas, they turn the handle in the wrong direction altogether and click it firmly OFF. Even when they’re present, safety interlocks designed to prevent this don’t always work.

This is another reason to caution your instructors against doing tank changes at pattern altitude, no matter what the POH might say. If the student accidentally shuts off the engine at altitude, the instructor might have as much as a couple of minutes to figure out what happened and try to get gas flowing again. If it happens on downwind, chances are that airplane’s coming up short. If a tank change is needed during pattern work or ground reference maneuvers, make a full-stop landing and do it on the ground; then run the engine for a couple of minutes before taking off again.

ASI Staff

David Jack Kenny

David Jack Kenny is a freelance aviation writer.

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