Incident Overview
Flight SR-306 was a scheduled international flight from Zürich to Rome, with an intermediate stop at Geneva. Dense fog was present at the time of departure. At 0600 hours, the flight was informed that the runway visual range (RVR) was 180 meters for runway 34 and 60 meters for runway 16, with a light northerly wind of 1 to 2 knots.
Taxi and Takeoff
At 0604 hours, the flight was authorized to taxi to runway 34 behind an accompanying vehicle. One minute later, at 0605, the crew reported they would taxi halfway down runway 34 to inspect fog conditions and then return to the takeoff position. This was accomplished, using at times considerable engine power, probably in an attempt to disperse the fog. Around 0612 hours, the aircraft was back at the threshold of runway 34, and permission to take off was granted. The flight took off at 0613 hours and began climbing to flight level 150, its cruising altitude.
In-Flight Fire and Mayday
Four minutes after takeoff, witnesses on the ground noticed a whitish trail of smoke on the left side of the aircraft, followed suddenly by a long flame from the left wing-root. Around 0620 hours, the aircraft reached an altitude of approximately 2700 meters. It then began to lose height, entered a gentle left turn while losing height more rapidly, and finally went into a steep dive. Parts of the aircraft became detached. At 0621 hours, a "MAYDAY" message was received.
Crash and Impact
At 0622 hours, the aircraft crashed into the ground on the outskirts of Dürrenäsch, at an elevation of 559 meters, approximately 35 kilometers from Zürich-Kloten Airport. The aircraft disintegrated on impact, causing a huge crater at the point of impact. All 80 occupants were killed, among them 43 habitants of the small village of Humlikon (200 habitants in total). Farmers specialized in milk business, they were flying to Geneva to visit a milk-farm.
Probable Cause
The official findings stated that the crash was due to the destruction of essential structural parts of the aircraft by a fire caused by overheating of the brakes during the taxiing phase.