What happened
On 01 December 2010, a BEDE BD-4, registration ZU-CXU, departed Wonderboom Aerodrome on a repositioning flight intended for Brits Aerodrome. The flight was being conducted by a commercial pilot accompanied by a passenger. While cruising at approximately 6,000ft AMSL, the aircraft experienced a significant drop in engine manifold pressure, falling from 15”Hg to 10”Hg, which resulted in a substantial loss of engine power.
Unable to maintain altitude, the pilot attempted to divert toward ODI Airfield. However, the loss of power necessitated an emergency forced landing in an open, grassy field near the airfield. During the landing sequence, the aircraft's nose landing gear struck a hole in the terrain, causing the gear to separate and the aircraft to nose over onto its back. The impact caused extensive damage to the wings, fuselage, and landing gear. Both the pilot and the passenger sustained serious injuries and required medical evacuation.
The investigation
An investigation by the SACAA AIID examined the mechanical state of the aircraft and the circumstances surrounding the flight. Investigators noted that the aircraft had recently undergone an annual inspection at an approved maintenance organization (AMO) that had since been suspended by the SACAA. During the pre-flight inspection on the day of the accident, several defects were noted, including low engine oil levels and a loose nose landing gear wheel, which were addressed prior to departure.
Technical analysis of the engine was hampered by the extent of the damage sustained during the overturn; while a teardown examination found no internal evidence of a cause for the manifold pressure drop, the damage to the engine control linkages prevented functional testing on a test bench. Furthermore, the investigation revealed that the accident was not reported to the authorities by the pilot or owners at the time of the occurrence; the AIID only became aware of the event five months later when the pilot visited their office.
Findings
- The primary cause of the accident was an unsuccessful forced landing.
- A significant contributing factor was the loss of engine power resulting from a decrease in manifold pressure below acceptable operating limits.
- The aircraft's nose landing gear failed when it encountered a hole in the grassy landing area, leading to the aircraft overturning.
- The accident was not reported to the SACAA AIID by the involved parties when it occurred.