What happened
On 14 August 2012, a Cessna 337 departed Rand aerodrome for a training flight involving a type conversion. Shortly after takeoff from runway 29, the crew attempted to retract the landing gear. During this process, an unusual sound and vibration were noted, accompanied by white smoke entering the cockpit. The crew immediately selected the landing gear to the down position, fearing the nose wheel was stuck.
Simultaneously, the front-mounted engine suffered a sudden failure. Because the hydraulic pump is driven by this engine, the crew was unable to retract the gear, creating significant drag. Unable to maintain altitude on the remaining aft engine, the pilot flying declared a "Mayday" and requested a return to Rand aerodrome. However, the aircraft's descent rate was too high to reach the runway. The flight instructor took control and executed a forced landing in an open field near the N3 highway in the Alberton area.
While the initial touchdown was successful, the nose gear struck a hidden anthill in the dry grass approximately 230 meters into the landing roll. This caused the landing gear to collapse and the cargo pod to detach from the fuselage. The aircraft skidded on its belly, sustaining substantial damage. All four occupants escaped without injury.
The investigation
SACAA AIID investigators examined the wreckage and engine components to determine the cause of the failure. The inspection of the front engine revealed that a connecting rod bolt had not been properly torqued during a previous overhaul. This allowed a connecting rod to become loose and eventually penetrate the engine crankcase, causing an uncontained failure and engine stoppage. The investigation also reviewed maintenance logs, noting a lack of documented engine preservation after the aircraft had been stored for an extended period.
Findings
- The primary cause was an unsuccessful forced landing following an uncontained failure of the front engine.
- The aircraft was overweight at takeoff by approximately 93 kg (5%), which prevented the aircraft from maintaining altitude on a single engine.
- Improper maintenance practices were identified, specifically that connecting rod bolts were not sufficiently tightened during the engine overhaul.
- The inability to retract the landing gear following the engine failure added excessive drag to the flight.
- There was no documented evidence that proper engine preservation procedures were followed during the aircraft's period of inactivity.
Safety action
- It is recommended that the Airworthiness division revise the inspection checklist for issuing Certificates of Airworthiness for small aircraft to include a more detailed study of the aircraft's historical maintenance and usage.
- The regulatory authority should provide clearer guidance regarding mandatory engine preservation procedures for aircraft that remain unoperated for periods exceeding 90 days.