Control Surfaces Separated Before Grob SPn Crash

 - December 13, 2006, 8:55 AM

Structural failure appears to have caused the fatal crash of the second Grob SPn prototype light jet near the company airfield in Tussenhausen-Mattsies, Germany, on November 29. Grob Aerospace CEO Niall Olver told AIN that the elevators and left-hand stabilizer separated from the aircraft before impact and were found “several hundred feet” behind the main wreckage. “We know they separated,” said Olver, “but we don’t know why.”

Grob changed the design of key control surfaces on Aircraft No. 2 from those on Aircraft No. 1 to accommodate anti-icing requirements and to provide more roll authority. The front end of the belly fairing was also re-profiled, according to Olver. Aircraft No. 2 was equipped with larger ailerons and a longer horizontal stabilizer than on Aircraft No. 1. Grob had also redesigned the “hinge fit” on the elevators. While Aircraft No. 1 had flown its full flight envelope up to 41,000 feet and Mach 0.8, Aircraft No. 2 had yet to do so.

Grob was demonstrating Aircraft No. 2 to approximately 20 members of the German Business Aviation Association when the airplane crashed 4.5 miles from the runway, killing chief test pilot Gerard Guillaumaud, 45, the sole occupant aboard the all-composite eight- to nine-passenger twinjet. The aircraft appears to have crashed at a steep angle and was destroyed by a post-impact fire.

Guillaumaud had just demonstrated a short-field takeoff and was setting up to do a high-speed pass over the field when the accident occurred, according to Olver, who was not present at the time. “He would have been accelerating for his first pass,” said Olver. Guillaumaud did not radio a distress call. “There was no indication of trouble at all,” said Olver.

While Grob’s test-flight program is standing down during the accident investigation, construction is continuing on a third prototype, scheduled to join the test fleet early next year and to be fitted with a complete interior by June. Olver said that construction of two more test aircraft would be accelerated to compensate for the loss of the second aircraft. He said the flight-test program was designed around four aircraft. Olver said the company would issue a new flight-test schedule shortly and that a new chief test pilot had yet to be named.

Before the crash Grob, had said that it expected the SPn to be certified in the third quarter of next year and that the first two years’ production of 15 to 20 aircraft annually had been sold out. The $7.1 million Grob SPn is powered by two Williams International FJ44-3A turbofans, designed to be flown single-pilot and have a range of 1,800 nm with six passengers. The aircraft is billed as a “utility jet” because of its ability to use short, unimproved runways. Grob announced the SPn at the Paris Air Show last year. In September, Grob announced that a private investor group led by Olver, who is also CEO of Zurich-based ExecuJet Aviation, had acquired the company.