Plane & Pilot
Tuesday, August 9, 2011

Save On Avgas


American avgas is becoming almost as expensive as European petrol. Here’s how to use less of it.


It barely matters what you fly these days— avgas is starting to comprise a greater percentage of an airplane's total operating cost. Back in the late '70s and early '80s when avgas was usually about $1/gallon, a standard formula for guess-timating total operating cost per hour on a production single was to simply multiply fuel cost times five.

I flew a company Seneca II in the U.S. and Canada for two years in the '70s, and I was appalled at paying a whopping $25/hr for fuel. Even my first Mooney 231 extracted $13/hr from my credit-card limit.

Today, you'll pay about $125 to fuel a Seneca II for an hour, and half that to run a Mooney 231 or 252. Avgas expense now consumes probably a third of total operating cost for most piston-powered, general aviation airplanes.

Even when fuel was cheap, no one wanted to spend more than they had to, but today's high fuel prices provide an extra incentive to save gas and money. It's a safe bet we'll never again see $4 avgas, much less $3 fuel, so why not save what you can?

Even when fuel was cheap, no one wanted to spend more than they had to, but today's high fuel prices provide an extra incentive to save gas and money. It's a safe bet we'll never again see $4 avgas, much less $3 fuel, so why not save what you can?

Here's a look at 10 ways (I really did try to find 11) to reduce the amount of fuel you burn for a given trip, and minimize the financial drain of high fuel prices. You'll note that some of these suggestions rely on making the airplane fly slightly faster or more efficiently to increase its mpg. We've deliberately excluded such pricey options as speed mods that often do little more than add weight. (Some, such as the LoPresti cowlings, most definitely work, but that's an expensive and not-too-efficient method of improving an airplane's mpg.)


Fueling your airplane very early in the morning, when temperatures are coldest and fuel is densest, will get you more bank for the buck. Every little savings counts!
1 Fly Slower And Higher
The most obvious fuel-saving technique is to simply reduce cruise power from 75% to 55%. It's purely a numbers game, so please bear with me on this.

Using a new-generation, re-start Cessna Skylane as an example, the reduction from 75% to 55% power drops speed from 134 to 115 knots while improving fuel burn from 12.6 to 9.6 gph. That's only a 16% speed loss in exchange for a 31% reduction in burn, a reasonably good bargain.

If you're willing to fly higher, you can improve the airplane's efficiency even more. Operate a Skylane at 55% at 6,000 feet, and you'll see the aforementioned 115 knots. Climb on up to 10,000 feet, and the same airplane will trip along at 120 knots on the same power and burn—that's five extra knots. Yes, you'll burn slightly more fuel in the longer climb, but you may get some of that back in the reduced-power descent.

One argument against this philosophy is that you increase engine time by flying slower; you may lose some of the financial benefit by paying additional engine reserve. So be it. We're talking about saving fuel.






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