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Closer to Reality

Electric Cessna 172 to fly next year

By Max Trescott

Electric 172
A rendering of the Phase 2 electric Cessna 172.

Futurist Predicts Electric Planes Will One Day Dominate Sky

November 15, 2010 — Higher reliability, lower operating cost, and enhanced safety are some of the benefits you can expect from a Cessna 172 with an electric motor, according to George Bye, CEO of Bye Energy, who was joined by Charlie Johnson, former president of Cessna Aircraft, during a Green Flight Project update at the AOPA Aviation Summit last week in Long Beach, California.

“Battery technology is not maybe quite there,” Bye said. “We’re in an R&D focus right now. But we’re looking forward to the next two to three years.”

Johnson described the nuts and bolts of the project. “We’re taking about 400 pounds of conventional engine out of the airplane, replacing it with a 40- to 45-pound electric engine, so that will give us about a 350-pound differential,” Johnson said. “We’re taking out about 300 pounds of fuel and some other things, leaving 650 to 700 pounds of useful carrying capacity for batteries.”

When overhauling an engine, Johnson added, a 172 owner should be able to install an electric motor for about the cost of a conventional gold engine replacement.

The initial Phase 1 electric 172 will be a two-place aircraft capable of about an hour’s worth of flight time. At the current rate of technology improvement, Bye Energy expects its Phase 2 aircraft to have endurance of two hours.

Higher reliability is expected from the electric motor, which should have 20,000-30,000 hours of operational capability versus 2,500-3,000 hours from a conventional GA engine. The electric motor should also be smoother with less noise and vibration.

Operating cost should also be lower, considering Bye Energy’s worst-case future estimates for the cost of electricity and best-case costs of fuel. “On the average, we’ll be able to reduce operating cost between 75 and 80 percent,” Johnson claimed. “So instead of operating an airplane at $55 or $60 per hour, we’ll be operating down somewhere below $10 per hour.”

The electric 172 has performance advantages too, since unlike conventional engines an electric motor has no lapse rate in which power output decreases at higher altitudes in thinner air. The engine cowling is more streamlined, since a large inlet to cool engine cylinders isn’t required. Thus, the root of the propeller can contribute to thrust and parasite drag is reduced by 10 to 14 percent.

The Phase 1 aircraft will begin taxi tests in the first quarter of 2011, fly in the spring, and be flown to numerous air shows during the summer. A Phase 2 aircraft will include a six-blade propeller and regenerative technologies including solar panels on top of the wings and a regenerative drag device to recapture energy from wing tip vortices. The company may eventually offer an APU and a 4-5 gallon jet fuel tank that could generate electricity to extend aircraft range.

The kicker? When descending, the prop generates electricity that’s added to the batteries. According to Bye, “Pattern work in a training environment is ideal and that happens to be our initial market interest with training airplanes.”

In EAA’s recent 2010 Survey of the Average Aviator, appearing in the November 2010 edition of Sport Aviation, 48 percent of pilots expected to fly an electric aircraft during their lifetime. If the Bye Energy Green Flight Project is successful, they won’t have to wait long.


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