What happened
On September 26, 2019, a Cessna Aircraft Company R182, registration LN-IPR, was performing a training flight at Trondheim Airport Værnes. The flight, which included an instructor and a student pilot, involved a series of maneuvers including a touch-and-go at a nearby grass strip before returning to the main airport for further landing practice.
As the aircraft approached the inbound leg of runway 09, the crew extended the landing gear. During the approach, the crew was instructed by the tower to circle due to other traffic. Upon completing the turns, the aircraft established on final approach, maintaining a slightly higher altitude to avoid wake turbulence from a preceding passenger aircraft.
While the landing initially appeared normal, the main landing gear began to retract immediately after the aircraft touched the runway. The aircraft veered to the right and came to a complete stop on the runway. The impact caused damage to the right horizontal stabilizer and a crack in the right wingtip fairing. There were no injuries to the two occupants.
The investigation
The Norwegian Safety Investigation Authority (NSIA) examined the aircraft's mechanical systems and the crew's procedures. Technical inspections revealed that the landing gear mechanism itself was functional, with no hydraulic leaks or system failures detected. However, investigators discovered that the throttle was not connected to the landing gear warning system. This disconnection meant that the audible alarm, which should trigger when the throttle is retarded below 12 inches of manifold pressure if the gear is not locked, was non-functional.
Testing demonstrated that it was possible to achieve a configuration where the nose gear was fully extended while the main gear remained unlatched. The investigation also looked into the crew's use of checklists during the approach.
Findings
- The primary cause of the gear collapse was likely that the landing gear handle was not moved to the fully down and locked position during the landing gear extension process.
- The failure of the throttle-linked audible warning system removed a critical safety barrier, leaving the crew without an automated alert for an improper gear configuration.
- The crew did not utilize the full "Before landing checklist" prior to the base turn, instead relying on a simplified GUMP (Gas, Undercarriage, Mixture, Propeller) check during the final approach.
- Bright sunlight and glare may have made it difficult for the instructor to visually confirm the green gear-down lights during the final check.
Safety action
- The NSIA emphasizes the importance of instructors acting as role models by strictly adhering to standard operating procedures and checklists.
- The authority recommends that flight clubs and general aviation pilots maintain a heightened focus on the proper execution of checklists, ensuring that the "Before landing checklist" is completed before entering the base leg to allow sufficient time for corrections.