What happened
On December 12, 1965, a Lear Jet 23, registration D-IHAQ, attempted a takeoff from runway 28 at Zurich-Kloten Airport. The aircraft was significantly overweight, carrying 13,084 lbs against a maximum takeoff weight of 12,50 and with a center of gravity positioned forward of the allowable limits. During the takeoff roll, the pilot experienced an unexpected and sudden increase in control column resistance while attempting to rotate the aircraft at high speed.
Believing a malfunction had occurred, the pilot initiated an aborted takeoff. The pilot reduced power, but the aircraft continued to accelerate, reaching speeds between 80 and 100 knots past the end of the runway. The aircraft then traveled approximately 200 meters through soft, wet terrain before striking a cable reel and the airport perimeter fence. The impact caused severe damage to the airframe. The co-pilot sustained fatal injuries, while the remaining occupants suffered various serious injuries.
The investigation
The investigation examined the aircraft's weight and balance, the runway conditions, and the mechanical state of the flight controls. Investigators analyzed the pilot's decision-making process and the crew's coordination during the emergency. The inquiry also looked into the operational procedures regarding engine shutdown and flap retraction during an aborted takeoff on a wet surface.
Findings
- The primary cause of the accident was the pilot'1s decision to abort the takeoff on a wet runway while the aircraft was overweight and experiencing a perceived control issue.
- The perceived resistance in the control column was likely caused by a loose nut in the control shaft that could intermittently obstruct the elevator movement.
- The aircraft experienced significant aquaplaning during the braking phase, which prevented the aircraft from stopping within the remaining runway length.
- The pilot failed to retract the flaps during the high-speed deceleration, which would have reduced lift and helped mitigate the effects of aquaplaning.
- There was a critical lack of coordination between the pilot and the co-pilot during the emergency procedures.
- The aircraft was operating with an unauthorized load, as the pilot had failed to verify the weight and balance or create a proper loading plan.
- The pilot failed to properly shut down the second engine, leaving it producing approximately 90 kg of residual thrust during the rollout.