What happened
On the evening of 30 June 2023, a Piper PA28-161 (registration ZS-OVY) was conducting a night navigation training flight from Chief Dawid Stuurman International Airport. The flight, which included an instructor and a student pilot, was operating under Part 141 training regulations.
While climbing past 4,200 feet above ground level near the northern suburbs of Grahamstown, the crew heard a loud bang inside the cockpit. This was immediately followed by significant airframe vibration and a sharp drop in engine RPM. The instructor took control of the aircraft and identified Runway 34 at Grahamstown Airport (FAGT) to the right. The pilot executed a forced landing, bringing the aircraft to a stop on the runway centerline. There were no injuries to the occupants, and the aircraft sustained no impact damage during the landing.
The investigation
Following the incident, an inspection of the engine revealed that oil was leaking from the cowling. A technical examination by an approved maintenance organization determined that the second cylinder had experienced a complete separation between the steel cylinder barrel and the aluminum head.
Investigators found evidence of an initial crack, indicated by combustion gas residue (blowby) escaping through the cylinder. The investigation noted that the crack was located on the lower side of the cylinder, an area obscured by inter-cylinder baffles, which made visual detection difficult. The aircraft had undergone an annual inspection only 11.5 hours prior to the event, and a compression test conducted during that inspection had shown healthy results for all four cylinders.
Findings
- The engine lost power due to a fatigue crack in the cylinder head, which eventually caused the head to separate from the barrel.
- The location of the crack was hidden behind engine baffles, hindering detection during routine visual inspections.
- The failure pattern is consistent with known issues involving certain cylinder assemblies, which have been subject to previous manufacturer recalls and airworthiness directives.
- The aircraft was maintained according to approved manuals and was considered airworthy prior to the flight.