What happened
On 29 October 2000, a Piper PA-3/2RT-300, registration G-NROY, was returning to Norwich Airport from Le Touquet on a private flight. During the initial approach to Runway 27, the pilot noticed a flickering red warning light indicating an unsafe nose landing gear condition. This prompted a go-around. Due to crosswinds, the pilot transitioned to an approach for Runway 22.
During the second approach, the nose of the aircraft appeared to drop excessively upon touchdown, leading to another go-around. The pilot suspected the propeller may have struck the runway surface. Following this second attempt, the pilot discovered the landing gear would not retract. An attempt was made to secure the gear using the emergency free-fall system by reducing airspeed and using aerodynamic loads to force the gear into the downlock position. However, no green light indication was achieved. After orbiting for 15 minutes in deteriorating, turbulent weather, a final landing was attempted on Runway 22. Upon touchdown, the nose gear collapsed, which subsequently caused the left main landing gear to fail. The aircraft ended up on the grass adjacent to the runway. There were no injuries to the seven occupants.
The investigation
Investigators examined the hydraulic system and found that the electric motor for the hydraulic pump had failed because the brushes had worn out. While the manufacturer recommended inspections every 500 flying hours, the motor had not been inspected since December 1997, despite the aircraft flying an additional 316 hours since that check.
Further investigation into the nose gear downlock microswitch revealed it was slightly mis-rigged. This misalignment caused the red 'unsafe' light to illuminate if pressure was applied to the linkage, even if the gear was technically locked. Regarding the gear collapse, investigators determined that the nose gear was not properly locked during the emergency extension attempt. The subsequent failure of the left main gear was attributed to hydraulic suction in the lines caused by the rapid collapse of the nose gear.
Findings
- The primary cause of the landing gear's failure to retract was the failure of the hydraulic pump electric motor due to worn brushes.
- The emergency free-fall procedure failed to achieve a secure downlock for the nose gear.
- The pilot's attempt to lock the gear via aerodynamic loads may have been hindered by the need to maintain safe airspeeds in turbulent weather, potentially preventing the gear from extending fully against airloads.
- The maintenance interval for the pump motor inspection had been exceeded.