What happened
On 14 June 2014, a Cessna 152, registration 4R-DJD, was conducting a solo circuit training flight from Colombo Airport, Ratmalana. During the flight, the student pilot flew south of the airfield to practice maneuvers. Upon returning to the airport for landing, the pilot heard an unusual metallic shearing noise and observed that the port side wheel was missing.
Following this discovery, the pilot executed a go-around and performed another circuit. The aircraft subsequently landed on Runway 22 using only the starboard wheel and nose wheel, with the left strut making contact with the runway at low speed. While the aircraft sustained damage to the strut, there were no injuries to the pilot.
The investigation
The investigation examined the aircraft's flight path, the condition of the detached components, and the surrounding environment. The detached wheel was located by police approximately 10 nautical miles south of the airport near the Southern Expressway.
Technical analysis was performed by the University of Moratuwa. Material stress tests on the detached wheel and strut examined the presence of fatigue, corrosion, and impact forces. Additionally, a flight test was conducted using a similar aircraft to determine if radar signal loss occurred at specific altitudes near the area where the wheel was found. The investigation also reviewed air traffic control transcripts and examined the possibility of the aircraft striking an object at low altitude.
Findings
- The investigation identified severe corrosion on the strut end and the fixing bolt.
- This corrosion contributed to the initiation of a fatigue crack at the bolt hole of the strut.
- The primary cause of the detachment was a fatigue crack that propagated until a brittle fracture occurred.
- The final detachment was triggered by a force acting at an angle against the direction of flight, likely caused by the aircraft striking a high-tension power line over the expressway.
- The aircraft was flying at a low altitude, which caused a temporary loss of Mode C transponder signal on radar.