On 27 March 2013, a Raytheon B200, registered VH-ZCO, was being operated on an aero-medical flight from Darwin to Port Keats, Northern Territory. On board the aircraft were the pilot and two flight nurses.
In preparation for landing at Port Keats the pilot selected the gear down. The left and right main landing gear down indication lights did not illuminate, while the nose landing gear down indication light (green) illuminated. The pilot elected to return to Darwin and advised air traffic control.
The pilot reported that on landing, the right main landing gear wheel touched down first and when the left landing gear wheel touched down the pilot felt the left side of the aircraft start to sink. The pilot shut down the left engine and feathered the left propeller, then shut down the right engine and feathered the right propeller. The left wing then contacted the runway and the aircraft skidded to a stop, at about 1551. The pilot and flight nurses evacuated the aircraft via the overwing exit. The aircraft sustained minor damage, while the pilot and flight nurses were not injured.
The operator determined that during the last overhaul of the left main landing gear, a washer was not installed, which resulted in the landing gear contacting the aircraft structure preventing the landing gear from locking in the down and locked position.
The Civil Aviation Safety Authority (CASA) conducted an investigation into the accident and found that there was no conclusive way to determine when the washer installation error occurred. CASA also established that this error was an isolated event.
The manufacturer was informed of the accident and determined that the missing washer would not have led to the failure of the landing gear to lock down. They believed that it was more likely that the drag brace was not installed or rigged correctly when installed on ZCO or that another landing gear assembly or maintenance error occurred, causing the circuit breaker to trip, resulting in the accident.
As a result of this occurrence, the aircraft operator has advised the ATSB that they are taking the following safety actions:
- A medical bag that was located near the overwing emergency exit was relocated.
- All B200 aircraft were inspected. The main landing gear on one aircraft was found not to be correctly assembled and this was rectified before further flight.
- A safety bulletin was issued to all staff to inform them of the accident.
- The training and checking department were to review the part within the proficiency check about this type of landing and ensure it is reiterated at the next base check.