The prototype Berkut was designed and built by Dave H. Ronneberg and Kerry Beresford as part of a business partnership between Ronneberg and Donald S. Murphy (called Experimental Aviation) between 1989 and 1992.
In 1992 the partnership dissolved, and Ronneberg (incorporating as Experimental Aviation, Inc.) brought the aircraft to market as a kit, while Murphy wanted to shelve the project entirely. A subsequent series of lawsuits between the two resulted in bankruptcy for Ronneberg and Murphy as individuals, and for EAI as a corporation. The kit was resurrected by Renaissance Composites, in 1996, with Ronneberg working as a consultant.
In January 2001, under pressure from Ronneberg, Renaissance sold the assets to Vicki Cruse who then formed Berkut Engineering Inc. That company withdrew the aircraft from the market in 2002. Ronneberg continues with the project, which is now directed at UAV markets . In 2003 a deal was struck to sell the project to Republic Aerospace but the deal fell through. Cruse is no longer involved with day-to-day operations, but maintains ownership.
Through the various incarnations approximately 75 kits were sold, and 20 airplanes completed.
The Berkut is descended from the Rutan Long-EZ, with the primary differences being retractable main landing gear, dual canopies, and molded fuselage, strakes, and spar. Like the Long EZ, the Berkut carries 2 people in tandem seats. The front seat occupant has access to all instrumentation and controls. The rear seat, normally holding the passenger, is equipped with a side stick and throttle, but no rudder pedals, brakes, or instruments. Aerodynamically only minor changes were made. The fuselage was stretched, and the nose, canard, instrument panel and pilot moved forward one foot, to allow a heavier engine to be used in the back. The main wing trailing edge was straightened, removing a small bend in the trailing edge of the Long EZ wing. The lower winglet was removed and the aileron size increased in both chord and span, increasing roll rate.
Early Berkuts used wings and canard that were structurally similar to the Long-EZ and used hot-wired solid blue 2 lb/cu. ft. density Dow STYROFOAM PI cores, but with carbon fiber skins instead of fiberglass. The fuselage and winglets remained fiberglass. Later versions (kits produced after spring 1999) used fully-molded carbon fiber canards and wings with high density, 5 lb/cu. ft. 1/4″ thick PVC or SAN foam cores, leaving only minor fairings and tip surfaces to be carved from foam. The Berkut has always used the Roncz 1145MS canard airfoil, which is more tolerant of bug and rain contamination than the original GU 25-5(11)8 airfoil originally used on the Long-EZ.
Berkuts used a retractable main (rear) landing gear system designed by Shirl Dickey for his E-Racer homebuilt. Originally Berkut used gear parts produced by Dickey, but over time they were repeatedly re-engineered and strengthened. Later kits had gear components produced entirely in-house. Like the earlier Vari-Eze and Long EZ, the Berkut parks with its nose gear retracted to prevent the plane from tipping over backwards when parked without a pilot in the front seat. Some early Berkuts utilized hydraulic nose-gear extension systems, but most have used an electro-mechanical jack-screw. With the electric system the pilot can climb into the cockpit with the nose down, then extend the nose gear, raising the airplane with him inside.
While the Long-EZ was originally designed for the Lycoming O-235 108-118 hp engine, the Berkut was designed from the outset for the larger Lycoming IO-360 180 hp engine. The aircraft was later adapted (with a different engine mount, cowls and battery location) to accept the 260-hp Lycoming IO-540, which most builders chose. With the 540, some have reportedly reached speeds of 300 mph in level flight.
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