Date & Time:
Apr 1, 1990
Type of aircraft:
Armstrong Whitworth AW.650 Argosy
Operator:
Safe Air
Registration:
ZK-SAF
Flight Phase:
Landing (descent or approach)
Flight Type:
Cargo
Survivors:
Yes
Schedule:
Christchurch – Wellington
MSN:
6801
YOM:
1965
Country:
New Zealand
Region:
Oceania
Crew on board:
2
Crew fatalities:
0
Pax on board:
0
Pax fatalities:
0
Other fatalities:
0
Total fatalities:
0
Aircraft flight hours:
47035
Aircraft flight cycles:
36329
Circumstances:
On final approach to Wellington Airport, the crew selected gear down but the left main gear failed to lock down. The crew decided to divert to Blenheim Airport for an emergency landing. Upon touchdown on runway 25, the left main gear collapsed and the aircraft came to rest. Both pilots escaped uninjured.
Probable cause:
The failure of the left main undercarriage to fully extend was caused by the seizure of the piston rod within the undercarriage jack assembly. The piston rod and the spring housing through which it passed had become scored, eventually resulting in the seizure. The piston rod had been installed, new, in the jack assembly some seven months earlier and had completed 787 landings. Further investigation found that the synthetic wiper ring had been installed incorrectly and would allow foreign material to find its way into the spring housing when the undercarriage was retracted. Additionally, hydraulic components on the undercarriage may have become contaminated during cleaning in an inadequately filtered cleaning booth, which was also used for general cleaning involving the use of abrasive pads.
