Jim Tomaszewski’s twin RV was one of the highlights at EAA AirVenture Oshkosh 2021 and he designed and built this unique experimental aircraft from a concept that he had in his head.
Images: Tom Snow
Jim had built himself an RV-6a in the mid-1990s, but he and his wife Ginger, like to go places and their single engine fixed tricycle-gear sport aircraft just did not offer what he wanted in a cross-country traveling machine.
With his job as chief pilot for a major executive jet charter company flying twin-engine jets, Jim wanted redundancy in his own aircraft, especially in the engine department. A twin homebuilt would be the answer, but none were available. Jim did not want to buy a twin, so he set about building his own.
“Simplicity plus redundancy equals reliability” is his motto, and he decided to convert his existing RV-6A. “This project resulted from too many nights in a hotel room,” he explained. Jim did over 100 drawings before starting the conversion. To make sure he was on the right track, Jim consulted with a famous aircraft designer whom he did not wish to name. The project took 10 years to complete.
Jim Tomaszewski named the aircraft ‘Twin JAG’, which stands for ‘Jim And Ginger’. The Twin Jag has almost the same dimensions as a Wing Derringer, which was a light two-seat twin designed in 1958 by John Thorpe. Only 12 were produced.
Jim’s modifications included increasing the wingspan to decrease the roll rate and more stable for IFR operations. He left the ailerons the same size. Other modifications included a larger RV-9 vertical stabiliser and rudder and RV-10 nose gear to handle the additional weight of two engines.
Engine choice was the next problem. Rotax engines were out of the question, as Jim just did not like reduction gears and opted for a pair of modified Corvair direct drive air-cooled 110 hp car engines instead.
“When I attended one of William Wynne’s FlyCorvair forums at Oshkosh, I knew immediately that I had found the right engines for my plane,” Jim recalls. “My Corvair engines run quiet and smooth,” he adds. “They are compact, simple and powerful and I’ve not had even the first bit of trouble with them.”
Two Sensenich fixed pitch ground-adjustable non-feathering propellers help produce the power needed. Jim installed a cable-activated bicycle brake calliper, to stop a prop from wind milling if he lost an engine.
A two-screen Dynon Skyview system, a Garmin 430W, a two-axis autopilot, a electric trim, heated seats, and a baggage compartment in the nose combine to make the Twin Jag a great aircraft.
“We don’t fly long legs because my ‘butt range’ is only about two and a half hours,” explains Jim Tomaszewski. “We like stopping at small airports because that’s part of the fun of general aviation.
The modified RV was finished and first flew as a twin in August 2018. Jim explains, “I was not looking for more speed and it flies exactly like my RV-6A did with a Lycoming O-320 and fixed pitch prop.”
Jim and Ginger took the aircraft to Oshkosh 2021, but since he and Ginger like to attend AirVenture in their camper, the Twin Jag is not likely to be back to Oshkosh any time soon.
However, during its brief visit to AirVenture, The Twin JAG drew a steady stream of curious lookers. What was most interesting was that most people did not see its RV-6 heritage.
Empty weight: 1,600 pounds
Gross Weight: 2,250 pounds
Useful Load: 650 pounds
Cruise speed: 175 mph
Climb rate: 1,000 feet per minute
Single engine climb rate: 300 feet per minute
Stall speed: 67 mph clean, 64 mph dirty
Fuel capacity: 54 gallons
Fuel burn 14 gph in cruise
Range: 3.5 to 4 hours