Investigation Report on Jet Airways B 737-800 Aircraft involved in landing gear collapse due improper overhaul of trunnion pins

Final Investigation Report on Jet Airways Boeing B 737-800 Aircraft involved in landing gear collapse due improper overhaul of trunnion pins at Khajuraho Airport, India, on 13-04-2015

Incident

Jet Airways B-737-800 aircraft VT-JGA flight 9W- 2423 (Delhi -Varanasi-Khajuraho –Delhi) was involved in an accident at Khajuraho Airport on 13.4.2015. There were 59 passengers and 08 crew members on board the aircraft.
During landing Roll, 15 seconds after touchdown, at speed 36 knots, left main landing gear aft trunnion pin broke and aircraft started deviating to the left of center line. The aircraft came to stop on runway with damage to the LH landing gear and resting on LH engine, Nose & RH landing Gear. Hydraulic fluid spillage occurred due to damage to LH main landing gear. Emergency evacuation was carried out on the runway.

Damage to aircraft.

The aircraft sustained substantial damage. Following main damages occurred to the aircraft.
1. LH main landing gear aft trunnion pin found sheared off. The aft end of the LH MLG has travelled up and (puncturing the composite panels) protruding out and above the aft wing surface (walking beam visible above the wing surface).The damage limited to the composite panels and their non-structural support frames.
2. The support beam is damaged due L/G travel.
3. Hangar link assembly found a drift.
4. Hangar link mount found dislocated.
5. Side strut assembly twisted
6. Door attachment bracket and door found damaged.
7. MLG stub beam (structural member) between the aft spar and the MLG support
beam lower forward attach lug ripped off.
8. Aircraft resting on the LH engine.

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Investigators of Aircraft Accident Investigation Bureau, India, found

The Committee of inquiry determined the cause of accident as “The LH Aft landing Gear trunnion pin failed due to overload following fatigue growth. Crack initiation was in the heat affected area where excessive grinding was done at the time of overhaul. Initial crack growth is charterized by intergranular cracking (assisted by hydrogen embrittlement mechanism) until fatigue took over.”