Oshkosh, Wis.-based Sonex Aircraft opened the order book on July 28 for the smallest, lightest and lowest-cost jet-powered airplane–the $125,000 SubSonex single-seater. The tiny jet will be sold as a nearly completed kit, and the price includes everything except paint and avionics.

“This has always been a dream of mine,” said Sonex chief designer, president and founder John Monnett. Sonex began testing the concept of a small jet two years ago with the JSX-1 proof-of-concept prototype, which was powered by a 150-pound-thrust model airplane jet engine. However, that engine wasn’t amenable to the precise control needed for a piloted airplane.

Coincidentally, Monnett met Bob Carlton, who flies the jet-powered Super Salto sailplane in airshows, including at AirVenture, and Carlton introduced him to Czech engine manufacturer PBS Velká Bíteš. This company’s TJ-100 engine turned out to be ideal for the SubSonex. “We were able to obtain the engine and retrofit it to the [JSX-1] airframe,” he said, “and that made it a viable project.” Carlton flew the first test flights of the new engine in JSX-1.

The $125,000 price is only for the first 10 buyers who sign up for the SubSonex. Buyers can reserve a slot in the assembly line for $10,000, then in the first quarter of 2014 Sonex will provide an offer to purchase when the rest of the money will be due. Deliveries are expected to begin in mid-2014.

The SubSonex is what Sonex general manager Mark Schaible said is an “ultra quick build” kit. This means that Sonex builds the wings, fuselage, empennage and control surfaces and installs the canopy and windshield. The builder just has to install the engine, fuel system, landing gear, avionics, flight controls, upholstery, BRS parachute and paint.

The ultra quick build kit doesn’t meet the FAA’s 51-percent guidelines for amateur-built airplanes, so a buyer can legally hire someone else to complete the SubSonex. The jet will fall into the Experimental Exhibition Group 5 category, which has no restrictions on where the airplane can be flown for proficiency purposes. Because the buyer won’t build 51 percent of more of the SubSonex, he or she won’t be able to obtain a repairman certificate as part of the building process. So the annual condition inspection will have to be done by an A&P mechanic. Pilots will need to obtain an FAA Letter of Authorization to fly the SubSonex.

Compared to JSX-1, the latest JSX-2 version has a larger and wider cockpit while retaining the same external dimensions, with more headroom and legroom. The instrument panel is larger too, to fit glass displays or an iPad mini, and buyers can also install an autopilot.

JSX-2 also has retractable landing gear, unlike JSX-1. The main landing gear uses dual-wheels and a unique integrated shock absorber system that uses urethane rods instead of leak-prone hydraulic struts. Outer wing panels will be easily removable, but not foldable. The 44-gallon fuel cell is rotationally molded and thus has no seams and also incorporates safe foam for fire protection. Cabin heat and oxygen will be options.

Range for the JSX-2 will be 300 miles with reserve. At lower altitudes, cruise speed is about 180 mph while burning 18 gph. Fuel consumption drops and speed increases at higher altitudes, Monnett said. Stall speed is 59 mph. Maximum weight is 850 pounds and empty weight 416 pounds, for a 434-pound useful load. The SubSonex will be capable of aerobatics, and aerobatic maximum weight is 750 pounds.

The 247-pound thrust TJ-100 is Fadec controlled and simple to start and operate. Hot section inspections need to be done every 300 hours and will be accomplished by sending the 45-pound engine to PBS in the Czech Republic. Turn-around time is one week.

The JSX-1 powered by the new engine uses less than 1,500 feet of runway for takeoff and landing, according to Monnett. The JSX-2 will use 1,200 feet for takeoff and 1,000 feet for landing. “The roll rate is exceptional and it flies a lot like a glider,” he said. Carlton will fly demos in the JSX-1 prototype equipped with the TJ-100 this week at EAA AirVenture Oshkosh on Tuesday, July 30 and Thursday, August 1. The JSX-1 and the JSX-2 cockpit are on exhibit at Sonex’s exhibit space in the North Aircraft display area.