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Fuel Burn, Schmuel Burn

It was the moment of truth. Michael removed the towel covering the fuel pump, revealing the verdict: 13.2 gallons. That was within a half-gallon of what we'd predicted! Unfortunately, the number we'd actually submitted on our rally form included an additional 10% "fudge factor," a decision that had just come back to bite us. Hard.

Sigh. Maybe next time.

My buddy Anders and I had just competed in a "Fun Fly" rally organized by our fellow club members Hal and Michael. My friend Angela accompanied us in our club's Cessna. She'd just lined up a gig writing for wired.com's Autopia section and was intrigued by my description of rally flying, so she came along to see what it was all about. She wrote a great story about the event.

The informal rally followed the format of the Hayward Air Rally. Hal and Michael have been flying our club's Bonanza in the Hayward Rally for several years now, and they've turned in several impressive performances, often scoring in the top three. Anders and I are newbies, but we've been officially bitten by the bug. On rally legs, he does the flying while I run a home-grown flight planning spreadsheet on my laptop.

Our course that day was a single leg traversing California's Central Valley, starting at Tracy and ending at Los Baños. The objective, as in the Hayward Rally, was accuracy in predicting time en route and fuel burn. This requires an intimate understanding of one's airplane, in particular its fuel burn and true airspeed under various conditions. Managing time is easier than managing fuel, and Anders and I are getting fairly good at it. We were only 13 seconds off this time around, which is respectable, if not quite good enough to be competitive.

It's the fuel that gives us fits.

"How much did we burn?" asked Angela after the fueling was done.

"13.2 gallons," I answered.

"And how much did you predict?"


"That's not very close, is it?"


In the past, our fuel-burn predictions had always come up about 10% short. So, lacking a good understanding of where the fuel was going, we decided to fudge it. We figured an extra 10% should at least get us closer. Not this time. There are so many variables, especially in our elderly carbureted Cessna. Reproducing a particular fuel-flow rate from flight to flight is difficult. Measuring the actual fuel burned in a particular configuration is a challenge. Just fueling the airplane consistently is hard. Clearly, Anders and I have our work cut out for us.

So, what's the attraction of this obsessive-compulsive behavior? Are rally fliers just sick? Should we seek professional help? Maybe, but it's a blast. There's the challenge of competing with people who really know what they're doing. There's the camaraderie of fellow and sister aviators. There's the opportunity to understand our airplane better, or at least realize how poorly we do understand it. Besides, as I'm so fond of saying, it's flying!

We all sat around the lunch table at Ryan's Place across the street from the airport swapping stories and comparing notes—being careful, of course, not to divulge any secrets. Finally the time came to announce the results of the day's contest. As Michael read them out, it came as no surprise to Anders and me that we came in seventh place. We took our well-earned lumps with grace if not with pride. At least we weren't "Tail-End Charlie" this time!

Being gluttons for punishment, and always on the lookout for excuses to fly, Anders and I have already signed up for this year's Hayward Rally. In the meantime, we'll be doing our homework and making more test flights in a quest to understand that elusive fuel burn. This year our goal is at least to get in the ballpark on both time and fuel.

In the immortal words of my hero Bullwinkle Moose, "This time for sure!"

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