Frugal Flyer: Fly high

Flying at higher altitudes can extend range and avoid needless and costly intermediate fuel stops.

September 1, 2009

Of all the advantages to flying high in general aviation piston aircraft, cost savings is easiest to overlook. Despite the well-known advantage of cooler and often smoother air, more direct ATC routings, reduced fuel consumption, and longer range, most GA pilots fly between 6,000 and 9,000 feet regardless of the benefits of thinner air above.

Sure, the best power and highest true airspeeds for most normally aspirated, piston aircraft can be found in the lower range. Pilots who fly there don’t have to be concerned with headaches, dehydration, or hypoxia that can result from improper preparation or execution of high-altitude flights. But the comfort, convenience, and simplicity of flying low come with a price.

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Consider the AOPA 2009 Let’s Go Flying Sweepstakes SR22’s recent trip from its home base in Frederick, Maryland, to Tampa, Florida, host city for the upcoming AOPA Aviation Summit (November 5 through 7). At its best-power engine setting and an altitude of 6,000 feet, the 735-nm flight would have taken 4.2 hours at 174 KTAS and consumed about 75 gallons of avgas (17.1 gph in cruise plus two gallons for the five-minute climb). That sounds OK until you consider the SR22 holds 81 gallons of usable fuel, so the airplane would have arrived with less than legal VFR fuel reserves. That would have meant an intermediate fuel stop (hello, South Carolina!), along with a hot start and a second, full-power climb.

Almost two miles higher, however—at 16,000 feet—the flight takes 15 more minutes (4.5 hours total) at 165 KTAS. But total fuel burn is reduced 20 gallons to a total of 55 (10.7 gph in cruise plus a 35.5-minute climb). The higher altitude (flown on June 17) allowed the SR22 to arrive at Tampa’s Peter O. Knight Airport with 26 gallons in the tanks. Like the fabled tortoise-versus-hare race, the slower-high road won because it bypassed the intermediate fuel stop, and it was far more efficient because it avoided a second gas-guzzling takeoff and climb.

Any flight in an unpressurized airplane that stays more than 30 minutes above 12,500 feet requires the crew to use oxygen. A portable, two-person Mountain High Aviation Oxygen System such as the one AOPA has in the Let’s Go Flying SR22 carries a retail price of $1,129. And filling the 24.2-cubic-foot aluminum cylinder costs between $20 and $40 depending on where you do it. (The cylinder provides about 20 man-hours of oxygen at 15,000 feet.) But since you’re saving about six gallons or $30 of fuel every hour you fly at the higher altitude, it takes less than 40 flight hours to recoup the initial investment. And having oxygen adds time- and money-saving options.

On a recent flight across the Sierra Nevada Mountains, the portable oxygen system allowed the Let’s Go Flying SR22 to take a nearly direct route from the San Francisco Bay area to Sedona, Arizona. Crossing the mountains just north of Mount Whitney’s 14,505-foot summit required a climb to the SR22’s service ceiling of 17,000 feet, and the shorter route cut the trip by more than 30 minutes.

Even in nonturbocharged airplanes such as the Let’s Go Flying SR22, higher altitudes and oxygen systems can increase flight efficiency, improve range, and cut costs.

E-mail the author at [email protected].

Dave Hirschman

Dave Hirschman | AOPA Pilot Editor at Large, AOPA

AOPA Pilot Editor at Large Dave Hirschman joined AOPA in 2008. He has an airline transport pilot certificate and instrument and multiengine flight instructor certificates. Dave flies vintage, historical, and Experimental airplanes and specializes in tailwheel and aerobatic instruction.