Structural failure eyed in Grob crash

 - December 20, 2006, 6:33 AM

Structural failure appears to have caused the fatal crash of the second Grob SPn prototype near the company airfield in Tussenhausen-Mattsies, Germany, on November 29. Grob Aerospace CEO Niall Olver confirmed to AIN last month 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.”

In a December 15 statement, the company said it now anticipates European certification of the SPn not in the third quarter of this year but rather in the first quarter of next year, with U.S. approval to follow in the second quarter.
Grob changed the design of key control surfaces on aircraft number two from those on aircraft number one 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 aircraft No. 1. The “hinge fit” on the elevators had also been redesigned.

While aircraft No. 1 had flown its full flight envelope up to 41,000 feet and Mach 0.8, No. 2 had yet to do so.

Grob was demonstrating 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 twin-engine “utility” jet. The aircraft appears to have crashed at a steep angle and was destroyed by a post-impact fire.

No Indication of Problem
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.

The exact speed of the aircraft at the time of the accident is not known so far as it was flying below radar coverage. While the ceiling at the time of the crash was reported to be about 1,000 feet, it is not believed that weather was a factor. Aircraft No. 2 was equipped with the Honeywell Apex system, but Grob’s runway does not have an instrument approach.

Olver said it was routine to perform demonstration flights with only one pilot aboard but that test flights were always crewed by two pilots. “We fly demonstration flights single-pilot,” he said. “It is usually just a local flight around the facility and we fly a fair number of them.”

Grob’s flight-test program is standing down during the accident investigation, but construction is continuing on a third prototype, scheduled to join the test fleet in the second quarter of this year and to be fitted with a complete interior by June. Olver said that construction on 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 replacement for Guillaumaud had yet to be named.

In a statement on December 15, Grob said that aircraft No. 4 will be fitted with a full interior and flying by September. This will be followed by the first serial production SPn, which will also join the flight-test program.

The statement said that the company’s engineers are continuing to work with the German Federal Bureau of Accident Investigation “to determine the precise cause of the accident.”

The first two years’ production of around 20 aircraft annually are reportedly sold out, and Grob has now said that it could increase output to 40 units by the third year of production. It is ramping up the production rate specifically to address the delay in certification.

“We are in regular dialog with our suppliers and our customers with respect to this and are extremely encouraged by their support to date,” said Olver.

The $7.1 million Grob SPn is powered by two Williams International FJ44-3A engines and is 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 revealed the SPn at the 2005 Paris Air Show. Last September Grob announced that a private investor group led by Olver had acquired the company.