Test-Flying
Once the airplane construction is complete and signed off by a PFA inspector, a permit to test-fly is applied for with a fee of approximately $60. The flying characteristics of the airplane are then determined through a comprehensive flight test, which is conducted by a test pilot chosen by the PFA. The aircraft must be proven to meet specific airworthiness requirements.
The test pilot selected by the PFA for Waters' Berkut was retired Royal Air Force test pilot Angus McVitie. A pilot since 1951, McVitie has over 12,000 hours. He was formerly a chief instructor of test pilots at the International Test Pilot School, and most recently, he has conducted test flights for the CAA and PFA. The fundamental goal for the test flight is to make sure the airplane is safe and does not have any characteristics that will get the pilot into trouble. The design limits and the flight envelope are thoroughly tested. This includes determining the stall speed, observing the handling characteristics at stall speed and exploring the highspeed end of the envelope by flying the airplane just above Vne and testing for flutter.
McVitie and the PFA have a specific test protocol that must be followed for the design to receive approval from the PFA and, later its permit to fly issued by the CAA. Prior to McVitie's first flight in the Berkut, he conducted a thorough briefing with Ronneberg, who would be putting the Berkut through its paces from the front seat under the direction of McVitie. During this briefing, the test protocol was discussed, and Ronneberg was requested to explain various handling qualities and systems in the airplane.
The airplane was loaded to gross weight for the test flight and put through its paces, all recorded by the PI Research data logging system. The first test was a time-to-climb, from 4000 to 10,000 feet, keeping the airspeed constant. Upon reaching altitude, McVitie requested a speed run to 240 knots indicated, which was 10 percent over the Vne designated by the PFA. For Ronneberg, this was the most uncomfortable part of the flight.
The
nose was pushed over, and the speed began to build. At 220 knots and 7000
feet, Ronneberg decided to take a breather and fly level for a minute.
He then pushed the nose over again, until reaching 240 knots indicated
(288 mph true-corrected for temperature and pressure), leveling the airplane
at 4000 feet. During the descent, McVitie asked Ronneberg to bump all
the controls to try and induce flutter and control reversal, neither of
which was observed. The airplane was then put through a comprehensive
stall series, with and without the gear and speed brake retracted.
McVitie was also interested in the slow-speed characteristics, such as might be found on an approach. The airplane was flown at minimum controllable airspeed to demonstrate glide ratio, fugoid oscillations in pitch and descent rate characteristics that might be found during an approach. Next, a level speed run was done at 2500 feet and full throttle. At gross weight, the airplane flew 220 knots. This is the fastest IO-360-powered Berkut to date.
Upon his return from the test flight, McVitie commented, "I thought the Berkut was a very pleasant airplane to fly. I have not actually completed the evaluation, but we've been through all the corners of the flight-test envelope. [The Berkut] is obviously not a boy's airplane; it is a fairly complex piece of equipment that must be treated properly, and it has natural characteristics that you expect with canards. It was one of the most pleasant canards I've flown."
Ecstatic with the test-flight results, Waters was required to put a minimum of 10 hours on the airplane, with one flight of at least two hours in duration, and to complete at least 15 takeoffs and landings. After this was completed, McVitie conducted a solo test flight and wrote a test-flight report, which was then submitted to the PFA. John Tempest of the PFA was on hand for the flight and was taken up in the airplane. According to him, the best part of his job is, " ... the experience where someone has applied to build a new design, monitoring it, checking everything, advising on it and finally, seeing it fly. It's great to see people enjoying their airplane."
When asked about his work with the PFA and his favorite flights, McVitie replied, "Most of the PFA airplanes I've flown have been very much run-of-the-mill, and this one, the Berkut, is probably the best of the airplanes I've flown under the PFAs auspices. It must be pretty well the top of the heap."
Journey's End
A permit to fly was issued by the CAA as a result of the PFAs complete satisfaction with the design. The PFA set the operating limitations for Waters' Berkut, including the Vne, aerobatic limitations and e.g. limits. Although capable of limited aerobatics, Waters' airplane is not approved for acrobatic flight. This is typical in the United Kingdom, since the design is not specifically designed for aerobatics like a Pitts, for instance. In addition, all experimental airplanes in the United Kingdom are day VFR only. However, the PFA is considering changes to this policy.
A PFA-approved inspector will return in one year to sign off an annual inspection conducted by Waters. At that time, Waters must also conduct a flight test, which includes specific parameters, such as rate of climb and stall speed. These parameters are designated by the PFA. Waters must then submit this data, along with the inspection, to renew his permit to fly for another year.
While the PFA works differently than the aviation agencies we are used to in the United States, its goal is to get more people and airplanes flying-safe- It takes people like Glenn Waters to bring a new design to the country and have the perseverance to see the project through all the requirements set forth by the agency. The result of the efforts of both the PFA and Waters is his Berkut, a remarkable example of an experimental airplane that may never be duplicated by another homebuilder.
For more information contact, Berkut Engineering, 3025 Airport Avenue, Santa Monica, California 90405; 310/391-0179, email: cruser@aol.com or via the Web: www.berkutengineering.com. Builder Glenn Waters can be contacted via e-mail: waters@flexnet.co.uk