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Last updated: 15 July 2019
Status:Final
Date:Wednesday 11 May 1994
Time:15:30
Type:Silhouette image of generic BE20 model; specific model in this crash may look slightly different
Beechcraft B200C Super King Air
Operator:New South Wales Department of Health
Registration: VH-AMM
C/n / msn: BL-125
First flight: 1985
Crew:Fatalities: 0 / Occupants:
Passengers:Fatalities: 0 / Occupants:
Total:Fatalities: 0 / Occupants:
Aircraft damage: Substantial
Aircraft fate: Repaired
Location:Dubbo Airport, NSW (DBO) (   Australia)
Phase: Landing (LDG)
Nature:Ambulance
Departure airport:Brewarrina Airport, NSW (BWQ/YBRW), Australia
Destination airport:Dubbo Airport, NSW (DBO/YSDU), Australia
Narrative:
After arriving in the circuit area of Dubbo Airport, Australia, the pilot extended the landing gear and obtained the correct down and locked indications. The right main gear leg subsequently collapsed during the landing roll.
The retract actuator trunnion bearings had collapsed, allowing excessive movement of the actuator in its mount. This resulted in insufficient travel of the actuator to fully engage the downlock. Two separate occurrences involving unsafe landing gear indications, which had been corrected in flight by recycling, had been reported to the operator's maintenance staff prior to the accident. The maintenance staff, unable to duplicate the defect on the ground, had adjusted the downlock switch. Those adjustments finally resulted in the switch jamming in the closed position, giving a safe indication.
The downlock switch has two functions, providing independent safe/unsafe indications of the lock and, in series with the nose and left leg switches, removal of electrical power to the hydraulic pump when the three downlocks are sensed in a locked condition. On the accident flight, with the right downlock switch jammed in the closed position, hydraulic pressure was terminated when the left and nose gears locked down. As the lock function of the right gear lock was compromised because of the failed trunnion bearings, the leg collapsed under the landing loads. Investigation of the aircraft maintenance requirements determined that the landing gear actuator trunnion bearings had been incorrectly identified as sealed bearings requiring no lubrication. The bearings fitted to the aircraft were of the unsealed type, with a requirement for lubrication every 1000 landings or 30 months.

Accident investigation:
cover
Investigating agency: BASI
Status: Investigation completed
Duration: 2 years and 3 months
Accident number: 199401233
Download report: Summary report

Classification:

Sources:
» ATSB


Follow-up / safety actions
As a result of the investigation into this occurrence, two other B200C aircraft from the same operator were found to have similar unsealed bearings fitted to the main landing gear actuator trunnion bearings. The operator has taken action to amend the aircraft inspection schedule to include lubrication of unsealed bearings and initiated a retirement life program for all sealed bearings.

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Map
This map shows the airport of departure and the intended destination of the flight. The line between the airports does not display the exact flight path.
Distance from Brewarrina Airport, NSW to Dubbo Airport, NSW as the crow flies is 299 km (187 miles).

This information is not presented as the Flight Safety Foundation or the Aviation Safety Network’s opinion as to the cause of the accident. It is preliminary and is based on the facts as they are known at this time.
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