Archive for October, 2011

The Dangers of Flight Test

Wednesday, October 5th, 2011

There should be no question that flight testing a new design is a much higher risk than routine flight. This falls into the “duh” category and yet the statistics of extremely high risk flight is lumped into GA’s accident rate. My interview with NTSB members Chris Hart and Earl Weener at AOPA Summit touched on this point.

GA is a diverse activity and that must be recognized. The single number fatal accident rate statistic is misleading. Two case studies:

Narrative Type: NTSB FINAL NARRATIVE (6120.4)
The pilot was performing high speed taxi tests in an experimental category airplane that he had designed and built. The airplane was configured with a T-tail, a canard wing forward of the cockpit with elevator control surfaces, and had two 28-hp engines mounted facing aft along the trailing edge of the wings in a pusher type design. The main landing gear were located forward of the engine nacelles. To address a lack of pitch response experienced during previous tests, the pilot had increased the size of the canard control surfaces, and moved the center of gravity further aft. During the first taxi run the electronic flight information system (EFIS) recorded a maximum pitch of 9 degrees, and maximum airspeed of 67 knots. During the test run that precipitated the accident, the airplane became airborne at the end of the taxi run and rose to about 122 feet above ground level (agl), entered a right-hand turn, stalled, and impacted terrain in a flat attitude. Audible engine sounds could be heard from the airplane throughout the event and the recorded data supported normal engine operation. The last 16 seconds of data recovered from the EFIS corroborated the witness reports, recording the airplane pitching up suddenly from 8 degrees to 45 degrees, the airspeed decaying from 55 to 22 knots, and then entering a rapid vertical descent. A colleague of the pilot stated that in this pusher configured airplane where the propellers are located aft of the main landing gear, a sudden reduction in thrust could cause a pitch up rotation moment around the main landing gear when on the ground….

At the other end of the GA spectrum was the loss of a Gulfstream 650 prototype in Roswell, NM resulting in four fatalities. According to NTSB’s preliminary report “Wingtip scrape marks beginning on the runway approximately 5,300 feet from the end of the runway lead toward the final resting spot about 3,800 feet from the first marks on the runway. Witnesses close to the scene saw the airplane sliding on the ground with sparks and smoke coming from the bottom of the wing, and described the airplane being fully involved in fire while still moving across the ground. The airplane struck several obstructions and came to rest upright about 200 feet from the base of the airport control tower.”

In my opinion, these two accidents do not belong in the general GA file, just as the Reno air race accident should be in its own category. We agree with EAA that amateur built and experimental aircraft in the flight test phase need to be treated separately.

The two areas where the emphasis should be placed are on personal flight and amateur built aircraft that have completed the flight test phase. Both these activities have opportunity for improvement. Exactly how that should be done is something of a challenge as I’ve pointed out in previous articles. There’s plenty of first class safety education material readily available for anyone willing to learn from the mistakes and mishaps of the past. For some pilots, they apparently lack the will to live.