Investigation Summary
On the morning of September 4, 1963, Zurich Airport was blanketed in thick fog. To clear the runway of fog using jet blast—a common but unofficial practice at the time—the crew taxied the Caravelle at high power settings while applying brakes to control speed. This caused the magnesium alloy wheel rims to overheat significantly. After takeoff, the damaged tires exploded in the wheel well, severing hydraulic lines and igniting a fire fueled by hydraulic fluid. The fire quickly spread through the fuselage, compromising the aircraft's control surfaces and leading to a steep, high-speed dive into the village of Dürrenäsch.
Final Conclusions
The accident was caused by the overheating of the wheel brakes during an extended taxi period at high engine power in fog. The subsequent tire burst in the wheel well led to a catastrophic hydraulic fire that rendered the aircraft uncontrollable.
Video Analysis
The Dürrenäsch Disaster – Swissair Flight 306 — An exploration of the events leading to the crash of Swissair Flight 306, where a fire caused by overheating brakes led to Switzerland's worst aviation disaster at the time.
Watch on YouTube ↗If playback is blocked, the owner has disabled embedding — use the link above.
Systems & Failure Modes
Braking System
Overheated during taxiing due to high power settings used to disperse fog, leading to tire failure.
Hydraulic System
Lines were severed by tire fragments and the resulting fire, causing a total loss of flight control.
Landing Gear Bay
The unsealed wheel well allowed the fire to spread rapidly into the fuselage and wing structure.
Interesting Facts
- 01The crash killed all 80 people on board, including 43 residents of the small village of Humlikon.
- 02The village of Humlikon lost one-fifth of its total population in the disaster.
- 03The aircraft was a Sud Aviation SE-210 Caravelle III named 'Schaffhausen'.
- 04Investigators found that the magnesium wheel rims caught fire due to the heat generated during taxiing.
- 05This was the deadliest aviation accident in Switzerland at the time of the occurrence.
Safety Actions & Advisories
Brake Temperature Monitoring
The accident led to stricter regulations regarding brake cooling times and the monitoring of wheel temperatures before takeoff.
Hydraulic Line Protection
Design changes were implemented in later aircraft to better shield critical hydraulic lines from tire bursts in wheel wells.