What happened
On 20 September 2021, a Gates Learjet 35A, registration ZS-SFV, departed Cape Town International Airport for Lanseria International Airport. The flight, operated under private Part 91 regulations, carried two pilots and three passengers. During the cruise and descent phases, the crew encountered a rapid succession of technical malfunctions, including the failure of the left generator and several unserviceable instrument backlights.
As the aircraft approached Lanseria, the crew's attention was further diverted by a master warning light and the failure of the augmentation aileron system, which impacted the aircraft's roll control. Due to these accumulating issues, the crew's pre-landing checklist was interrupted. Consequently, the landing gear was never transitioned to the down position. The aircraft touched down on Runway 25 with its gear retracted, skidding on its belly for approximately 2 kilometres before coming to a stop. While there were no injuries to the five occupants, the aircraft sustained substantial damage.
The investigation
SACAA AIID investigators examined the cockpit environment and the sequence of mechanical failures leading to the accident. The investigation established that the crew was managing multiple simultaneous defects, including unserviceable indicators for hydraulic pressure, airspeed, and altimeter backlights. The investigation also looked into the functionality of the aircraft's warning systems and the maintenance history of the airframe.
Findings
- The primary cause of the accident was the failure to extend the landing gear prior to touchdown.
- High cockpit workload, driven by multiple recurring instrument defects, distracted the crew from standard procedures.
- The crew failed to properly consult the pre-landing checklist during the approach.
- The landing gear warning horn and associated red indication lights failed to activate as required by the Pilot's Operating Handbook.
- Issues related to poor maintenance contributed to the unserviceable state of the warning systems.