What happened
On 3 March 2009, a Beechcraft B36TC, registration ZS-SVM, was preparing for a private flight from Kimberley aerodrome to Ladysmith. During the takeoff roll, the aircraft exhibited abnormal maneuvers before nose-diving into the ground near the runway threshold. While both occupants survived the initial impact, the passenger died at the scene due to burn injuries, and the pilot succumbed to injuries two weeks later.
The investigation
SACAA AIID investigators examined the wreckage and the engine components, including the Continental TSIO-520 UB engine and the propeller. The investigation focused on whether mechanical failure contributed to the loss of power. Detailed inspections of the spark plugs, oil pump, magnetos, and fuel pump revealed no technical defects or mechanical failures. Furthermore, the aircraft was found to be airworthy and properly maintained at the time of the accident.
Testing conducted on a similar engine type suggested that the engine could fail if the auxiliary fuel pump was switched to the high position while the mixture was set to full rich. Investigators noted that the auxiliary fuel pump switch was found in the "HI" position, and the lack of damage to the "gated" switch suggested it was moved intentionally rather than bumped.
Findings
- The engine lost power or failed during the takeoff phase due to an over-rich mixture setting.
- The pilot likely intended to retract the landing gear but accidentally engaged the auxiliary fuel pump to the high position.
- The pilot failed to maintain the necessary flying speed following the engine power loss, which led to an aerodynamic stall.
- The aircraft was destroyed by a post-impact fire, though no in-flight fire was detected.
- Weather conditions at the time of the accident were fine and did not contribute to the event.
Safety action
- It is suggested that flight instructors maintain strict oversight regarding the procedures followed during engine failure scenarios, as failure to adhere to correct emergency protocols should be a critical factor in student evaluations.