What happened
On 25 February 2005, a CONVAIR 440, registration ZS-ARV, was conducting a domestic charter flight from Johannesburg International Airport (FAJS) toward Skukuza (FASZ). While cruising approximately 5 nautical miles east of Witbank, the pilot experienced a backfire in the number 2 engine.
In response to the engine malfunction, the pilot initially intended to divert the aircraft to Lanseria Aerodrome (FALA), which serves as the operator's maintenance base. However, as the backfiring in the number 2 engine persisted, the decision was made to return to Johannesburg International Airport. The aircraft landed safely at FAJS with 0 fatalities and 0 injuries reported among the 23 people on board.
The investigation
SACAA AIID investigators examined the mechanical state of the aircraft and the maintenance history of the operator. Records indicated that the aircraft had logged 17,571.9 total airframe hours and had only flown 7.6 hours since its last major periodic inspection (MPI) on 10 February 2005. The maintenance organization had undergone a recent audit in November 2004 with no significant issues noted, and all maintenance records appeared to be in order.
Findings
Technical analysis of the engine revealed that a crack had developed in cylinder number 16 of the 18-cylinder engine. The fracture originated at the internal corner where the cylinder wall meets the cylinder head. This cylinder failure led to a loss of pressure within the engine system, resulting in the observed backfiring and subsequent power loss.