Description

On 2 April 2011, a Gulfstream G650 being operated by the manufacturer on a pre type-certification test flight failed to become properly airborne when attempting a take off from Roswell for a local flight in normal daylight visibility with one engine intentionally inoperative. The right wing had been observed to touch the runway before the aeroplane impacted ground obstacles and caught fire with the resultant deaths of all four Gulfstream employee occupants and destruction of the airframe.

Investigation

An Investigation was carried out by the National Transportation Safety Board (USA) (NTSB). It was found that the aeroplane had stalled whilst lifting off the runway and still in ‘ground effect’ and that the SPS had not operated prior to the stall. It was noted that ground effect results in increased lift and reduced drag at any given angle of attack (AOA) as well as reducing the AOA at which an aerodynamic stall will occur. It was found that this had been considered during the preparations for G650 field performance test flights but the effect on the stall AOA in ground effect had been over-estimated so that SPS activation and the corresponding PFD pitch limit indicator had been set too high. In the investigated event, the flight crew of two pilots and two flight test engineers had also not had any tactile or visual warning before the actual stall occurred.