The Dangers of Flight Test

October 5, 2011 by Bruce Landsberg

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.

Bruce Landsberg
President, AOPA Foundation

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3 Responses to “The Dangers of Flight Test”

  1. Mark Jones Jr Says:

    One of the good and bad characteristics of General Aviation is that people can do whatever they want with their airplanes. The first example is CLEARLY part of the “general” aviation. Maybe we don’t want it to be, but I think it belongs, because along with our freedoms as general aviators, we have some responsibilities.

    I do agree, however, that the Gulfstream crash should not be considered “general aviation.”

    The bigger picture that we are missing is this:
    THE NUMBERS DON’T MATTER! What matters is the true interpretation of the data.

    If we can’t get a bloated, ineffective federal agency to change the way they push paper, then stop trying.

    The president isn’t going to save the aviation industry. The NTSB isn’t going to change the culture of pilots. We are losing because we are fighting the battle with groups who have more money and people using their tactics.

    WE CONTROL OUR OWN DESTINY!

    Frankly, I’d be delighted to see more stories that inspire me to lead my fellow pilots in a culture of legacy and safety.

  2. Dick Van Pelt Says:

    I have never seen an explanation of how a canard aircraft can be designed to provide pitch stability similar to a tail controlled aircraft. Can someone explain or provide a good reference on the subject?

  3. Alex Says:

    @Dick Van Pelt

    Pitch stability is a result of Xcg – Xac, where X is a distance from a datum forward of the airplane (arbitrary so long as consistent), and cg and ac refer to locations of center of gravity and aerodynamic center, respectively (aerodynamic center is the location about which moment caused by lift is constant with angle of attack, and can be approximated as a function of the distribution of “area” of a top/bottom cross section of the aircraft with all wings/canards/stabilizers included). There is no reason here, for static stability, that a canard configuration cannot provide equal pitch stability for most purposes.

    In this case, the thrust axis did not pass through the CG, which will induce a moment. In a very small airplane such as the one described, engines placed above or in line with a high wing may induce quite a large moment relative to the moment provided by the canards mounted on a relatively short fuselage.

    If, like some canard designs, the thrust axis is through the CG, the flying characteristics can be made very similar, albeit with a more limited CG range due to the shorter moment arm of the canards and likewise shorter fuselage.

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