Status:prototype, later sold as kitplanes
Type: experimental canard pusher
Powerplant: 1 x 180 hp (205 hp) Lycoming IO-360
Significant date: 1991
By using a VariEze manual to reverse engineer, aviation enthusiast Dave Ronneberg began to understand the intricacies of composite fabrication and design. During this time, he was hired by Thomas Aberle of Aberle Custom Aircraft and manufactured Starduster II wings. Working with Aberle for two years, Ronneberg gained invaluable experience in rag, tube, metal, and wood construction and engine assembly techniques. When Aberle moved his business from the LA area, Ronneberg and a friend, Arnold Dutton, then began building two VariEzes. Just after the canards were complete, word came out that the Long-EZ was available. A trip to Mojave ensued and Ronneberg bought the second set of Long-EZ plans ever sold. So the two VariEzes became Long-EZs.
From 1980 to 1983, working with his clients, Dave built three Long-EZs. In early 1983, Dave was employed by Dick Rutan for construction of Voyager. In 1984, he returned to Santa Monica and continued building Long-EZs. Liberally sprinkled amongst these projects were movie programs, cars, tooling jobs, and a stint with California Microwave manufacturing Remotely Piloted Vehicles, all the while gaining the experience necessary to evolve the Long-EZ into a moldable, manufacturable kit aircraft. In 1987, Ronneberg started fulfilling his dream. Sam Kridell, head of Shuttle Design for North American Rockwell, used a Cray supercomputer to produce a set of full-size templates of the fuselage and bulkheads that Dave had designed over the previous five years. Using these templates, a full-size model of the fuselage was built, however the project was shelved for two years while funding was acquired.
Finally, in 1989, construction began on the prototype bird, now called the Ronneberg/Murphy Berkut. The model of the fuselage built in 1987 was 12" longer, 3.5" wider, and provided 4" more headroom than the Long EZ. These features were retained in the prototype Berkut. This airplane would emerge with fully retractable gear, designed by Shirl Dickey designer of the ERacer. Ronneberg acquired the rights to use Shirl's gear in the prototype and future Berkut kits and now produces the gear himself after Dickey stopped production. The prototype Berkut utilized a Lycoming IO-360 180-hp engine bumped up to 205 hp. Light Speed Engineering's Klaus Savier designed the electronic ignition.
The Berkut differs from the EZ in a number of other ways. The canopy of the Long EZ is one piece whereas the Berkut canopy is two pieces, a canopy for each person much like a fighter jet. This was incorporated to eliminate the effect of shrinkage of a canopy this size at colder temperatures, affecting the fit and seal of the canopy. The Berkut ailerons are 6" longer than on an EZ and have a 3/4" larger chord at upper surface the hinge line and 7/8" larger chord on the lower surface. The lower winglets have been eliminated by incorporating them into the wing on the Berkut. The strakes (the triangle portions between the fuselage and wing) have a convex upper surface instead of the flat surface found on the EZ.
The Berkut also makes use of carbon fiber in the design. Carbon fiber is found in the canopy frame, wing skins and spar caps, main spar caps, and canard skins and spar caps, longerons and cowls. Carbon fiber was chosen because it is four times stiffer and one-and-one-half times stronger than fiberglass by weight. The use of carbon fiber in the Berkut prevents unwanted torsional flexing in the wing, making for a much more rigid structure with no weight penalties. This, combined with the larger ailerons, also makes for a roll rate double that of a Long EZ.
The Berkut aircraft was built by Dave Ronneberg and Don Murphy between 1989 and 1992. The prototype N91DR was completed in the summer of 1991 and flown to Oshkosh. The reception was outstanding but Ronneberg was not ready to sell kits just yet. He used the next year to acquire financing, tooling, and materials necessary for producing kits, as well as writing a construction manual. In 1992 the partnership between Ronneberg and Murphy dissolved, and the former finally decided to bring the airplane to market as a kit. At Oshkosh 1992, orders were taken and deliveries began in January of 1993. The first Berkut kit went to Glenn Waters in the United Kingdom.
With the advent of the more powerful Berkut 540, for the original Berkut became known as the Berkut 360. Fixed gear versions also were marketed as the Berkut 360 FG and Berkut 540 FG. Unfortunately, a series of lawsuits between Ronneberg and Murphy resulted in bankruptcy for both. The kit was resurrected by Renaissance Composites in 1996, and in 2000, the company chose to announce a four place Berkut, but in 2001 Renaissance sold out to Berkut Engineering, a company which itself withdrew from the market in 2002, and the four-seater is no longer under development.
After several requests for a fixed gear version, Ronneberg has configured the Berkut to accept conventional Long-EZ gear as the Berkut FG. The only changes to the kit occur in the C kit and accessory packages. Berkut Engineering also announced "new and exciting engine options involving the IO-360 and IO-540 that will be announced as further details are available" but although Berkut production was restarted in late 2002/early 2003, these never materialized, and despite this short run, the Berkut aircraft kit is no longer available and BED do not have plans to bring the aircraft back into production. As for the N91DR prototype, it suffered a fatal accident in 1995, was rebuilt, and became in 2003 the superfast Super Berkut 540 demonstrator, under the auspices of the newly formed Berkut Engineering & Design, Inc. With this new venture, David Ronneberg has proceeded with development of the Berkut, which is now directed at UAV (Unmanned Aerial Vehicle) markets.
Population: 1 prototype [N91DR], less than 20 built
Crew/passengers: 2Main sources:
- Berkut Engineering website
- Berkut - Son of an EZ!