Okinawa

It is considered highly probable that this accident occurred through the following causal chain: When the Aircraft retracted the slats after landing at Naha Airport, the track can that housed the inboard main track of the No. 5 slat on the right wing was punctured, creating a hole. Fuel leaked out through the hole, reaching the outside of the wing. A fire started when the leaked fuel came into contact with high-temperature areas on the right engine after the Aircraft stopped in its assigned spot, and the Aircraft burned out after several explosions. With regard to the cause of the puncture in the track can, it is certain that the downstop assembly having detached from the aft end of the above-mentioned inboard main track fell off into the track can, and when the slat was retracted, the assembly was pressed by the track against the track can and punctured it. With regard to the cause of the detachment of the downstop assembly, it is considered highly probable that during the maintenance works for preventing the nut from loosening, which the Company carried out on the downstop assembly about one and a half months prior to the accident based on the Service Letter from the manufacturer of the Aircraft, the washer on the nut side of the assembly fell off, following which the downstop on the nut side of the assembly fell off and then the downstop assembly eventually fell off the track. It is considered highly probable that a factor contributing to the detachment of the downstop assembly was the design of the downstop assembly, which was unable to prevent the assembly from falling off if the washer is not installed. With regard to the detachment of the washer, it is considered probable that the following factors contributed to this: Despite the fact that the nut was in a location difficult to access during the maintenance works, neither the manufacturer of the Aircraft nor the Company had paid sufficient attention to this when preparing the Service Letter and Engineering Order job card, respectively. Also, neither the maintenance operator nor the job supervisor reported the difficulty of the job to the one who had ordered the job.

It is estimated that the accident was caused as follows:
The aircraft was being operated on a training flight at Shimoji-Shima Airport, and was making a one-engine-out touch-and-go landing with the right engine simulated inoperative. The touchdown was late and beyond the normal aim point, and on the direction of the instructor, the trainee pilot attempted to go around on only the left engine. However, the trainee mishandled the aircraft, and then, seeing the instructor advance the right engine’s thrust lever, he applied right rudder pedal mechanically. This coincided with an increase in the rotation speed of the left engine, and the aircraft’s attitude suddenly changed towards the right. Because the trainee pilot could not fully correct this and the instructor was late in taking over control, the aircraft veered off the east side of the runway into a grass area and was damaged. Moreover, it is estimated that the following causal factors contributed to the accident:
1) The instructor did not take over when he directed the trainee to go around, or at an earlier stage, because he thought to allow the trainee pilot to handle the aircraft as much as possible, and because he did not sufficiently recognize that a go-around with one-engine simulated inoperative is a difficult maneuver for an inexperienced pilot.
2) Regarding the instructor’s intent to allow the trainee pilot to handle the aircraft as much as possible, the company’s instructional guidelines contained statements meaning that a judgment to go around should be made by the trainee pilot, and that during simulated one-engine-out touch-and-go training landings, the go-around after landing should continue with one engine simulated inoperative.
3) Regarding the instructor’s insufficient recognition of the difficulty of a go-around with one engine simulated inoperative for an inexperienced pilot, the instructor had not been trained to deal with the situation encountered in the accident, and the company’s regulations and manuals did not describe considerations on the difficulty of executing a go-around with one-engine simulated inoperative for an inexperienced pilot or on the effects of the wind on such maneuvers.
4) Regarding the delay in the instructor taking over control of the aircraft, the instructor was not following with his hands on the control wheel and was not in a position to take over immediately if necessary, and when the instructor had changed from being a simulator instructor to a flight instructor, he had not received sufficient training on cautionary matters regarding training in actual aircraft.