Paris 2011: Big Frog to stake France’s claim to Reno glory

Paris Air Show » 2011
June 20, 2011, 6:15 AM

The Big Frog racer is getting attention for more than just its tongue-in-cheek patriotic name. The French aircraft is the first carbon-fiber race plane to run on a diesel engine powered purely by jet-A fuel. And it is turning heads here at the Le Bourget show.

Big Frog is the brainchild of three pilots–Frank Doyen, Mario Soave and Willy Gruhier–who dreamed up the project in 2005. They wanted to prove that a high-performance aircraft with a diesel engine could win the prestigious Reno National Championship Air Races, which take place every September in the Nevada desert.

The novelty of Big Frog lies in its combination of a lightweight Nemesis NXT airframe with a diesel engine. Thanks to the U.S.-made airframe, which is mostly carbon fiber except for the fiberglass wingtips and vertical stabilizer, Big Frog team leader Franck Doyen expects his aircraft to weigh about 330 pounds less than competitors on race day. Powered by its original Lycoming TIO540-NXT engine, the Nemesis NXT has already won the Sport Class race in Reno three times.

Big Frog’s SMA SR305-230 engine consumes less fuel and has lower emissions than one running on avgas. It is also greener in that it doesn’t contain leaded additives that are harmful to the environment and public health. Diesel engines are a relatively new phenomenon in the field of light aviation–they usually have been considered too heavy–but they are enjoying newfound interest as the high cost and negative environmental effects of avgas raise concerns.

The engineers at SMA Engines, a division of French Safran group, are one of the few teams to have successfully developed a diesel engine for light aircraft. Doyen and others working on Big Frog have reworked the powerplant systems–such as cooling, turbo and exhaust–to fit their needs on raceday.

“The horsepower is not something we will make public,” Doyen told AIN, “except to say that it’s far more than the motor’s original power capacity of 230 horsepower.” Another notable innovation is that the aircraft’s wings and horizontal stabilizer can be disassembled for transport.

The Big Frog team is currently composed of a dozen engineers, designers and public relations specialists, as well as several high-profile “godparents” like world aerobatic champion Pascale Alajouanine and Formula 1 car racing legend Henri Pescarolo. Most members of the Big Frog team have experience in Formula 1 racing, as do the engineers behind the SMA engine.

“I was attracted to the challenge in Reno because I found the spirit of nascar: an oval, a pack, a sprint and a checkered flag,” Doyen explained, referring to the parallels with America’s number-one auto sport.

The French team has witnessed the races often, and, according to Doyen, American racers appreciate their ability to poke fun at themselves by adopting the name Big Frog. In Reno’s Sport Class race, airplanes will fly past ten 50-foot-high pylons around a seven-mile circular course.

The Big Frog team hopes to showcase advanced technology and French leadership by winning the Reno Sport Class Silver race with a French pilot and a French engine. Americans consistently dominate the Reno championship, although other nationalities also participate. “We have pilots from Australia, New Zealand, Switzerland, Japan, Germany, England and Canada,” said Valerie Miller, a spokesperson for the Reno Championship. 

The last time a Frenchman won was in 1936, when Michel Détroyat piloted a Caudron Rafale to victory. Seventy-five years later, the Big Frog team also has a “first” to be proud of. According to Miller, a diesel engine has never competed in the Sport Class before. Reno is an important step as it will introduce Big Frog to a large audience of air racing enthusiasts; this year’s event is expected to draw more than 200,000 spectators.

“In 2010, we were very close to being ready to go [to Reno],” said Doyen, “but we had some construction delays.” He and other team members are doing all they can to be in Nevada this year. According to Doyen, “The plane is ready; it flies almost every day.” He will confirm Big Frog’s participation in the championship after this week’s Paris Air Show. During the race, the team’s goal is to fly faster than 300 knots, with an average speed of 280 knots. The Sport Class category regularly sees speeds upward of 350 knots. 

The Big Frog team is also thinking about how to develop air racing in Europe, where aerobatics have always been more popular. “Right now our focus in on Reno,” said Doyen. “As for the next step, we are considering our options, we’re asking questions. We like the idea of a Reno-type race in Europe, with some differences, but we’re not really in a position to discuss that right now.”

Early on, PICY Development came onboard as a financial backer of the project. The company furnished the team with its “electron convertor in real-time nanotechnology” for use in Big Frog. Dassault Systèmes is supporting the project in a technical capacity via its Passion for Innovation program. During the design phase, Dassault’s Catia modeling software and Simulia simulation tool showed the team how best to combine the diesel motor and the Nemesis NXT airframe.

In 2009, the team found another partner in the French air force, which was particularly interested in the potential of a diesel-powered composite aircraft. This partnership has taken shape at the Mont-de-Marsan air base, which has welcomed Big Frog and now hosts its test flights. Two pilots are scheduled to fly Big Frog at the Reno races: Christophe Delbos, a fighter pilot based at Mont-de-Marsan, and founder Willy Gruhier.

Big Frog is conducting aerial demonstrations every day at Le Bourget this week. It is also on static display.

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