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Maiden Flight for SubSonex

V-tailed jet completes two flights at Wittman Field

By Fareed Guyot, Manager – Electronic Publications, EAA 388642

Bob Carlton
Test pilot Bob Carlton is all smiles after completing a second flight in the SubSonex on Thursday, August 11, at Wittman Field in Oshkosh.

The SubSonex on approach to Runway 27 at Wittman Field Thursday, August 11. It was the second flight for the V-tailed jet with Bob Carlton at the controls.

Bob Carlton and John Monnett
Test pilot Bob Carlton (left) talks with SubSonex designer John Monnett (right) after his second flight in the single-engine jet Thursday, August 11. The aircraft made its much-anticipated first flight the day before. All photos by Steve Cukierski.

See the photo gallery

August 11, 2011 – A little yellow jet was spotted over Oshkosh Wednesday morning (August 10) and soon it was confirmed that John Monnett’s SubSonex had made its first flight. Jet sailplane pilot Bob Carlton, who wowed AirVenture crowds two weeks ago, was at the controls for the 14-minute flight. Thursday Bob took to the air for a 45-minute flight that included four landings and a climb to 5,000 feet, which Carlton joked took about two minutes.

The flights are the culmination of at least four years of development including an engine change and a design review to address controllability during takeoff and landing. It was a happy day for Sonex Founder John Monnett, who designed the SubSonex for the recreational pilot.

The first flight was exciting, but after watching repeated landings on Thursday the entire Sonex team was giddy and impressed with the jet’s performance.

“Awesome. Awesome,” John Monnett said as he listened to Bob Carlton describe how the plane performed on Thursday’s flight. Later Monnett talked about how far the project has come: “It’s a proof-of-concept. Hey, can we build a jet? Yes, I guess we can. I think I’ll call it the ‘Little Hornet,’” he mused, referencing the Hornet’s Nest, which is the official name of Sonex’s  research and development facility.

Carlton was selected to be the test pilot in part because his Super Salto jet-powered glider uses the same Czech-built PBS engine (První Brnenská Strojírna Velká Bíteš, a.s. TJ-100), which is capable of 240 pounds of thrust.

“It was great - flies like an airplane,” Carlton said after the first flight.  “The faster I went, the better it felt.”

Carlton kept the throttle at 70 percent during the first flight as he checked out the low-speed characteristics of the aircraft, including how it performed in a stall. On Thursday’s flight Carlton used 90 percent throttle as he worked on expanding the test envelope, staying mostly in the airport traffic pattern to establish performance at different airspeeds. The two flights will allow the SubSonex to expand the test area away from the airport.

“It’s an exciting day for Sonex,” Monnett said after Wednesday’s flight. “Usually I am in that seat, but especially with the trepidation we had with the other gear, we knew this would solve that problem.”

The aircraft originally sported a tandem landing gear with outrigger gear on each wing tip. Controllability became an issue in the “transitional phase approaching takeoff speeds,” Sonex said in a June 2010 press release announcing a design review of the aircraft following a taxi-testing incident that caused minor damage after it departed the runway.

The SubSonex emerged from the review with fixed tricycle landing gear and it did about eight high-speed taxi runs on Monday, raising up the nose a few times to test the new configuration. Monnett said the nose gear will eventually retract.

“It’s kind of a vindication more than anything,” Monnett said.  “Once we get a retractable gear on the nose at least, we’ll see where we go with the program. I probably envision this thing is going to end up with a folding wing like the Onex.”

While the SubSonex someday might be a kit, the project is still on the backburner in Sonex’s Hornet’s Nest facility while other kits in development - such as the Onex - are being finalized.

First flight:

Second flight:


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