What happened
On 18 December 2009, a Beech 95-B55 aircraft, registration ZS-NKB, departed from Wonderboom Airport (FAWB) for a type conversion training flight. The flight, operated by Loutzavia CC, was intended to proceed to the general flying area #2. Shortly after takeoff from runway 29, witnesses observed the aircraft struggling to gain altitude and flying at an dangerously low height. The pilot transmitted two emergency MAYDAY calls to the control tower but did not specify the nature of the distress. The aircraft subsequently struck trees and crashed into the Apies River, approximately 3.5 km from the aerodrome. The impact and subsequent post-crash fire resulted in 2 fatalities.
The investigation
SACAA AIID investigators examined the wreckage and the mechanical state of the engines. The investigation focused on the engine performance and the configuration of the fuel systems. Testing conducted on a similar aircraft type revealed that when fuel boost pumps are set to the HIGH position with a full rich mixture, the aircraft can experience a descent rate of over 300 feet per minute despite engines appearing to operate normally. Additionally, investigators found that the right-hand engine's spark plugs were fouled, preventing them from firing under pressure. The investigation also reviewed the Pilot Operating Handbook (POH) and the physical cockpit layout, noting that the control column obstructed the instructor's view of the fuel boost pump switches.
Findings
- The primary cause of the accident was the failure of the aircraft to gain sufficient altitude after takeoff, leading to a collision with terrain and vegetation.
- The fuel boost pumps were set to the HIGH position, which, combined with a full rich mixture, prevented the engines from producing full power.
- The right-hand engine suffered from fouled spark plugs that failed to function under pressure.
- The instructor's ability to monitor the fuel boost pump switches was compromised because the control column obstructed the view from the right-hand seat.
- The POH lacked clear instructions regarding the use of fuel boost pumps during emergency or specific operational scenarios.
- Both the instructor and the student pilot had limited flight experience on this specific aircraft type.