What happened
On 8 February 2019, a flight instructor and a student pilot were conducting circuit training at Hoedspruit Aerodrome. While the Bantam B22J aircraft, registration ZU-DOG, was turning on the crosswind leg for Runway 17, the engine suddenly failed following a loud bang and the sound of breaking metal.
Recognizing the emergency, the instructor took control of the aircraft, maintained the best glide speed, and broadcast a MAYDAY call. The instructor identified a suitable landing site in the Zandspruit River, a dry riverbed, and executed a forced landing. During the landing roll, the aircraft's right main wheel struck a rock while traveling at approximately 20 knots. The nose gear subsequently dug into the soft soil, causing the aircraft to nose over and come to rest in an inverted position. While the aircraft sustained substantial damage, there were no injuries to the two occupants.
The investigation
An inspection of the Jabiru 2200A engine was performed by an approved maintenance organization. The teardown revealed that the inlet valve on the number 4 cylinder had failed due to metal fatigue. Further examination of the valve stem showed significant wear, indicating that the valve had been moving excessively within its guide. The investigation established that the valve guide was worn beyond allowable limits, which caused the valve to operate at improper angles, ultimately leading to its fatigue failure.
Findings
- The primary cause of the in-flight engine failure was a worn valve guide, which resulted in the fatigue failure of the inlet valve.
- The aircraft's inversion during the landing roll was caused by the nose gear digging into soft ground after the right main wheel struck a rock.
- The engine had completed 898.0 hours of operation since new.
- The flight was a Part 141 training operation conducted during daylight under favorable meteorological conditions.
Safety action
- The SACAA should consider adopting and mandating the implementation of safety guidelines previously published by the Australian CASA regarding the operation of aircraft powered by Jabiru engines.