Flight Training - November 2012 - 41

FLIGHT LESSON

By Raymond Brown
FLIGHT LESSON offers the opportunity for pilots to learn from the experiences of others.

LEST EMPTY FUEL TANKS SMITE THEE

KNOW THY AIRPLANE

t was a scheduled nine-hour flight in a Cessna Turbo 210 with one fuel stop. I was cruising at 15,000 feet and I planned the fuel stop for 100 miles from my position. I had 135 gallons of fuel on board when I departed. I had a range of six hours, so I would make my refueling stop with plenty of reserve fuel.
After about four hours I realized I was burning way too much fuel. I was becoming more aware of the fuel gauges; they were moving toward the dreaded side of “empty” at an alarming rate. At this point I started to recalculate my time. I had been in the air for more than four hours, and I was positive I should have had an hour and a half of fuel. gulped its last drop of 100LL. A switch to the left tank brought the big Lycoming back for a short while. By this time I knew I would not make any airport under power, as the left fuel gauge was on empty. I headed to the only field around that had a long runway, an FBO, and fuel. My hoped-for destination was 30 miles dead ahead.

THE FUEL GAUGES WERE MOVING TOWARD THE DREADED SIDE OF "EMPTY" AT AN ALARMING RATE.
When the GPS showed 80 miles to the refueling stop, the gauges started their move to the big “E” at a pace so fast, I could actually see the needles moving. I switched to the right tank, which showed the lowest fuel level. I determined that when that tank went dry, I would know that I still had fuel in the left tank. I had already punched up the nearest airport function key on the navigator and had altered my course from an east to a northwest heading when the right tank Then, the anticipated “sound of silence.” I was now unofficially a glider pilot. After I had informed air traffic control of my new flight rating, they seemed more panicked than I was. I was at best glide speed, descending from 15,000 feet. There was never a doubt as to whether I could make the airport. I just did not want to be too high or, God forbid, too low. I arrived at the pattern at a good alti-

tude, made a beautiful dead-stick landing, and, in my best Bob Hoover style, exited the runway with a complete stop on the taxiway. The aircraft was towed in and refueled—135 gallons. The tanks were bone dry. Resuming the flight, and making sure I planned a fuel stop before three hours, I needed to figure out why an aircraft that is supposed to burn 18 gallons per hour and have an endurance of six hours had run out of gas in four and a half hours. Although I had leaned the mixture to what I assumed to be 18 gph—never assume—it was not. Upon closer inspection, the gauge was calibrated in PSI and MP, not fuel flow, as I was used to in other, similar aircraft instruments. The cruise checklist called for mixture lean to 1,530 TIT, or turbine inlet temperature. Lo and behold, a number appeared on the fuel monitor screen. It was the TIT temperature. Still very skeptical, and extremely gunshy, I set the mixture using my newfound information. Back to altitude, leaned to recommended TIT, after three hours in the air the tanks had hardly moved off the full mark, so on I flew. After five hours in the air, I landed at my final destination with just a shade under half tanks, and a still-full center tank. On the ground, I recalculated the entire trip and realized I had been burning 28 gph for the trip to exhaustion. Not knowing or becoming familiar with the onboard fuel-monitoring equipment, I had leaned—but nowhere enough, burning more than 11 gph more than I should have. The lesson learned, however, is no matter how experienced and professional you think you are, you can still be very stupid. My advice to myself and to all pilots is to know thy aircraft.

LESSON LEARNED
ALEX WILLIAMSON

Never assume, particularly when it comes to fuel calculations.

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Flight Training - November 2012

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