Pilot's tip of the week

Fuel Gauge Inaccuracy

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Subscriber question:

"My instructor told me to ignore the airplane fuel gauges in the Cessna 172M that I'm using for lessons. Is that good advice?" — Paul M.

David:

“No, this is not good advice. Airplane fuel gauges should work as well as the one in your car. While that’s not always true with an airplane that is almost 50 years old, you should still approach light airplane fuel gauges with a ‘trust but verify mindset.’

Start by verifying the fuel quantity before takeoff with a properly calibrated dipstick. Compare the quantity shown on the stick with what the gauges says. After a few fill-ups, you’ll get a feel for the accuracy of the gauges. My experience is that the gauges get more accurate in the last third of the fuel capacity, which is where it matters most. And a properly maintained airplane will have the fuel gauges calibrated every year to confirm that when they indicate zero to empty the tank is indeed empty.

Don’t ignore an unexpectedly low, or a sudden reduction of, fuel level in flight. I know of one wrecked airplane where the pilot ignored the unusually low fuel quantity readings because he was sure the gauge was wrong. The good news was he wasn’t hurt in the forced landing. That was helped by the fact that there was no post-crash fire, as the airplane had no fuel it to burn.”

(NEW) IFR Mastery scenario #173 “Mammoth Winds West of Macon” is now available. A last-minute switch to a slower airplane is unfortunate, but flight planning shows strong tailwinds will almost make up the difference. The time and range should still work—until you level off in cruise and see an ETA an hour further out than you anticipated. Surely that can’t be right. But what is right? Watch the Intro video.

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