What happened
On 06 April 2018, a Pulsair aircraft, registration ZU-BLM, was conducting a private flight departing from Saldanha Airfield (FASD) in the Western Cape. After an initial flight from Morningstar airfield, the aircraft had been parked on a sunny apron for approximately thirty minutes. Following pre-flight inspections and taxiing to Runway 20, the aircraft took off at 1100Z.
During the climb, at an altitude of roughly 200 feet above ground level, the engine began running roughly and backfired, subsequently losing power and stopping. Realizing there was insufficient time to switch fuel tanks, the pilot executed a forced landing within the runway clearway. The aircraft struck the ground with significant force, causing the nose wheel to collapse and the propeller to strike the surface. The aircraft skidded approximately 300 metres. There were no injuries to the two occupants on board.
The investigation
SACAA AIID investigators examined the circumstances leading to the engine failure and the mechanical state of the aircraft. The investigation focused on the period when the aircraft was parked in direct sunlight prior to the second departure. Technical analysis of the engine and fuel system was also conducted.
Findings
- The engine failure was caused by fuel starvation resulting from vapour lock within the fuel line.
- Because the aircraft was parked in the sun, the fuel lines heated up, causing the fuel to vaporize.
- The engine was not equipped with a fuel return line, which is a critical component for preventing vapour lock.
- There was no evidence in the engine logbook to confirm compliance with several manufacturer service bulletins, specifically those regarding fuel line modifications (SI-912-020[1]) and fuel hose replacements (ASB-912-016UL).
- The lack of a return line prevented the diversion of fuel back to the tank, which is necessary to maintain stable fuel temperatures and prevent the formation of vapor bubbles.