What happened
On March 23, 1979, at approximately 17:25 local time, a DC-9-51, registration HB-IST, was preparing for a charter flight from Zurich Airport to London-Gatwick. During the takeoff roll on Runway 28, the pilot observed a large bird at eye level near the intersection of taxiway N. Following a collision with a 750g buzzard, the pilot initiated a rejected takeoff at the critical decision speed (V1) of 143 knots.
Although the crew applied wheel brakes and reverse thrust, the aircraft could not be brought to a halt on the damp runway surface. The aircraft overran the end of the runway, traveling approximately 40 meters into soft ground and coming to a stop 12 meters to the right of the runway centerline. There were no injuries to the crew or the 122 passengers on board, and the aircraft sustained no damage, though minor damage to the terrain was noted.
The investigation
SUST examined the braking performance, the runway conditions, and the operational procedures in effect at the time. The investigation established that the runway was wet and in the process of drying. The crew initially set the reverse thrust to 1.6 EPR, as per their pre-takeoff briefing. As the aircraft decelerated, the pilot requested more reverse thrust, which the copilot increased to 2.0 EPR, but later reduced to 1.4 EPR after noticing a loud noise from the engines.
The investigation also reviewed the manufacturer's performance data and the airline's operating procedures. It was noted that the aircraft's braking capacity was not fully utilized during the most critical phase of the deceleration.