What happened
On 17 October 2019, a flight instructor and a student pilot were performing circuit training at Lanseria Aerodrome (FALA). The aircraft, a Diamond Aircraft Industries, DA 20-C1 with registration ZS-SJY, had successfully completed three touch-and-go landings without incident. However, during the fourth circuit, the aircraft experienced a sudden jolt on the main wheels as the nose lowered.
Following the touchdown, the instructor noted the nose dropped lower than usual, accompanied by a loud grinding noise. The aircraft's propeller subsequently struck the runway surface. While there were no injuries to the two occupants, the aircraft sustained substantial damage. Upon inspection after the aircraft came to a stop, it was discovered that the nose landing gear wheel and fork assembly had completely separated from the landing gear strut.
The investigation
SACAA AIID examined the maintenance history of the aircraft, noting that a Mandatory Periodic Inspection (MPI) had been completed just one day prior, on 16 October 2019. During this inspection, the nose landing gear fork assembly had been replaced due to the discovery of cracks.
Investigators reviewed the parts used during this maintenance procedure. While the maintenance organization confirmed that a cotter pin was used to secure the castellated nut, the specific part number used was MS24665-360. However, the manufacturer's Service Bulletin (DAC1-32-03) explicitly required the use of part number MS524665-285. The investigation also considered other potential causes, such as hard landings or stud failure, but ruled these out due to a lack of supporting evidence and the recent inspection records.
Findings
- The primary cause of the separation was the installation of an incorrect cotter pin during the reassembly of the nose landing gear fork following the recent MPI.
- The maintenance engineer utilized a part that did not meet the manufacturer's specifications for the upgraded fork assembly.
- The separation occurred during a routine training maneuver, specifically a touch-and-go landing.