What happened
On 25 June 2019, a Cessna 441 Conquest II, registration EI-DMG, was conducting a private flight from Waterford Airport, Ireland, to Glasgow Prestwick Airport, UK. The aircraft was operated by two pilots and carried seven passengers. During the ILS approach to Runway 30, the crew performed standard landing checks, which indicated that all three landing gear lights were green and locked.
As the aircraft touched down on its main gear, the pilots noticed the nose was dropping lower than usual, accompanied by a scraping sound. Realising the nose gear had not fully extended, the crew opted against a go-around due to the risk of further damage. Instead, they increased engine power and applied back pressure to the control column to keep the nose elevated while simultaneously activating the emergency landing gear blow-down system. This action successfully extended the nose gear for the remainder of the landing roll.
During taxiing, the crew discovered a fuel leak from the right engine. The aircraft sustained damage to the engines, propellers, and the right-hand nose locker door. There were no injuries to the two crew members or seven passengers.
The investigation
The AAIB investigation focused on why the nose landing gear failed to deploy and why the cockpit warning systems failed to alert the crew. The investigation examined the aircraft's landing gear indication and warning system, which is designed to provide visual and audible alerts if the gear is not down and locked.
Technical analysis considered several electrical possibilities provided by the manufacturer. It was noted that the nose landing gear downlock switch is a two-pole switch that provides the ground for both the green indicator light and the warning horn. If this switch provides a continuous ground, the light would appear green even if the gear is in transit, and the warning horn would be silenced.
Findings
- The nose landing and main landing gear were not fully extended upon touchdown.
- The landing gear warning horn did not activate during the approach.
- The landing gear down and locked lights appeared green despite the unsafe condition.
- A faulty downlock switch on the nose landing gear actuator was identified as a likely cause, as it could provide an erroneous ground signal to the cockpit indicators and prematurely trigger the hydraulic bypass valve, preventing full extension.
- The aircraft's downlock switches are known to be susceptible to moisture or contaminant ingress, which can lead to such malfunctions.