What happened
On the morning of 23 May 2019, a Bantam B22J microlight, registration ZU-FFB, departed Phalaborwa Aerodrome for a flight toward Skuku and the Kruger National Park boundary. About six minutes into the flight, while cruising at 1,500 feet, the pilot noticed the engine running roughly. In an attempt to return to the departure airfield, the pilot initiated a turn, but the engine's RPM began to drop rapidly. The pilot reported hearing a metallic clanking sound followed by a heavy thud, after which the engine ceased operation entirely.
Realizing the aircraft could not reach the aerodrome, the pilot identified the 18th fairway of the Hans Merensky Golf Course as a suitable landing site. After broadcasting a Mayday call, the pilot attempted a forced landing. However, at an altitude of only a few feet above the ground, the aircraft stalled. The resulting hard impact caused the nose and left main landing gear to collapse, forcing the engine cradle to fail and the engine to strike the aircraft's windscreen and pod. There were no injuries to the pilot, though the aircraft sustained substantial damage.
The investigation
SACAA AIID investigators examined the wreckage and performed a teardown of the Jabiru 3300A engine. The inspection revealed significant internal damage, including fragments of the piston and a deformed connecting rod within the number 4 cylinder. Metallurgical analysis of the engine components was also conducted to determine the nature of the component failure.
Findings
- The primary cause of the engine failure was a fatigue failure of the exhaust valve on the number 4 cylinder.
- High operating temperatures were observed on the cylinder head and the failed valve area, which likely contributed to the fatigue.
- The pilot was fully qualified and the aircraft had a valid authority to fly and a recent annual inspection.
Safety action
Investigators noted that this incident was part of a pattern, having identified three separate accidents involving Bantam B22J aircraft with Jabiru engines suffering valve failures within an eight-month window. To address this, the AIID recommended that the SACAA and the engine manufacturer conduct a safety study focusing on the material composition of the valves and the impact of excessive heat or inadequate cooling on valve integrity.