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May 1, 2009
I read AOPA Pilot, as well as a number of other aviation periodicals, diligently every month. I have read countless articles which chronicle the events leading to fuel exhaustion accidents. Invariably the pilots writing those articles previously felt that such an event could never happen to them. Although I’ve never quite run out of fuel in an airplane, that fact has more to do with dumb luck than anything else. I very nearly became a victim of fuel exhaustion, and even worse, I almost caused another pilot to run out of fuel.
On June 2, 2007, I successfully completed my private pilot checkride in my instructor's Cessna 172SP as a 100-hour pilot. On the previous day, I had agreed to purchase a state-of-the-art composite, piston single along with two friends, Jeff and Scott. Over the course of the next year, I flew as often as I could, accumulating hours, honing my piloting skills, and learning the technically-advanced aspects of our new airplane. During that time (over 130 hours logged), it was apparent that the fuel gauges were exceptionally reliable. Based on the gauges, I could tell within a gallon or two how much fuel it would take to top off. This was not just an occasional observation, but one that I had made numerous times over the course of the year. In cruise flight, we would typically burn about 10 gallons per hour. I rarely put myself in the position of having only less than one hour of fuel remaining in the tanks. On those few times that I got close, my only thought was to get on the ground as quickly as possible — even though I was well above IFR and VFR minimum regulatory requirements.
On May 30, 2008, my two partners and I traded our plane for a "demo" model of the top-of-the-line version of our manufacturer's composite piston single. At this point, I had already begun training for my IFR rating. I completed my transition training for the new plane on a Sunday. Later that week, I had another IFR lesson scheduled with my instructor, Ron. The new plane's fuel capacity is 92 gallons usable, nearly double that of our previous plane. On the day of the flight, the gauges read nearly 30 gallons each side. Although this would be plenty for our two- hour lesson, I still decided to taxi to the self-service fuel just to be safe. It is all too common for the fuel pumps to be out of service at our airport, as they were that day. No problem, I thought. We had planned to travel to a non-towered airport with an ILS about 30 miles northeast of our home base to shoot some approaches. Although we should have had plenty of fuel, we could always land at that airport to add more.
After practicing maneuvers to become familiar with the new plane, we headed to the airport to shoot some approaches. During flight, the pilot’s operating handbook recommends switching tanks periodically to avoid a fuel imbalance. Although some minor variation in the fuel gauges was common in our previous plane, I was somewhat disconcerted to see that the fuel gauges in the new plane were fluctuating wildly. At one moment, it would appear that one tank had much more fuel than the other. I would switch tanks, only to note a minute later that the apparent discrepancy had completely reversed. Still, I reassured myself, there is no way that the gauges would show more fuel on board than we actually had. After all, this plane had been flown by one of the company representatives for three weeks before it was delivered to us. Surely he would have alerted us to such a serious flaw if he had known of it.
After about two hours of flying, I suddenly noted one of the fuel gauges was down to just five gallons, the other registered about 10. I switched to the apparently higher tank and suggested to Ron that we wrap it up and head home. The short flight home was made even quicker by the new plane's higher cruise speed. We requested a practice approach to our home airport, and we were given an ILS to Runway 15. We landed uneventfully, taxied back to the hangar, and put the plane away. Just another routine flight.
I knew that Jeff had a cross-country flight planned for the next day. Since the fuel pumps were inoperative, I was not able to top off the plane. I sent Jeff an e-mail to let him know there was about "15 gallons" left in the plane. Based on that information, Jeff decided to fuel up at a nearby airport, with working pumps and lower prices, prior to leaving on his cross-country trip. Our plane has an electronic fuel page to keep track of fuel remaining. After fueling, we typically hit the "full fuel" button, and then reduce the total by three gallons as a safety margin. However, since the gauges on our previous plane were so accurate, I never paid much attention to the information that the fuel page provided. Fortunately Jeff did pay attention the next day when he started the plane and the fuel page reported the fuel remaining as zero gallons!
He elected to taxi to our fuel ramp which was now operating appropriately. Jeff was able to add 88.6 gallons of fuel to the plane that morning. That means that when I landed the previous day, I had 3.4 gallons of usable fuel left! Needless to say, I was stunned when I received that information from Jeff. How could such a near-disaster happen to me? Our previous plane was equipped with mechanical float sensors for the fuel gauges. For our new plane, the manufacturer has switched to an electronic fuel sensor. Apparently there were rare problems reported with the mechanical sensors. Based on my experience, the accuracy of the mechanical sensors appears to far outweigh their potential problems. There were numerous times after this incident when we demonstrated on our plane that the gauges indicated 15-20 gallons MORE than what was actually on board.
Our manufacturer has since offered to replace all electronic fuel sensors with mechanical. We have taken advantage of this offer, and while our gauges are still not as accurate as our previous plane, they are a whole lot better than they were with the electronic sensors. I have also since learned that our electronic fuel page is extremely accurate, so it is now my primary tool to manage fuel.
I'll be forever grateful that Jeff demonstrated superior judgment and did not rely on my estimate of fuel remaining. Had he left for the nearby airport to refuel, he certainly would have been a victim of fuel exhaustion. What did I learn from this near-disaster?
Brian Litch is an instrument-rated private pilot with about 350 hours flying time. He has never come close to running out of fuel again.
Aircraft Power and Fuel,
Pilot Safety and Skills,
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