History of Flight
On Sunday morning, 1 August 2021 at approximately 0932Z, an instructor and a student pilot on board a Cessna 172N aircraft, registration ZS-SPB, took off from Runway 07 at Lanseria International Airport (FALA) in Gauteng province for a circuit training flight. Visual meteorological conditions prevailed. The flight was conducted under visual flight rules and Part 141 of the Civil Aviation Regulations.
During the second circuit, while on mid-downwind right for Runway 07, air traffic control instructed the crew to orbit left and re-establish on downwind right to allow another aircraft to land. While orbiting, the engine began to run rough and vibrate severely. Subsequently, the engine stopped. The student pilot, who was the pilot-in-command, attempted to restart the engine but was unsuccessful. He then decided to execute an emergency landing on taxiway Charlie. The aircraft landed safely at approximately 0956Z.
Injury and Damage
No injuries were sustained by either occupant. The aircraft was not damaged during the incident sequence.
Engine Examination
The engine was removed from the aircraft post-incident and sent to an approved engine workshop for inspection. Examination revealed the crankshaft had broken into two halves at the Number 4 piston connecting rod journal area due to fatigue cracks.
Probable Cause and Contributory Factor
The investigation determined the probable cause of the incident was in-flight engine stoppage as a result of a failed crankshaft that broke into two halves at the Number 4 piston connecting rod journal area due to fatigue. This was followed by a successful forced landing. A contributory factor was polishing of the connecting rod journal, which possibly introduced a notch (material weakness) during the engine's last overhaul.