What happened
During a multi-engine training flight focused on landing procedures, the crew encountered a critical mechanical failure involving the landing gear. The instructor pilot (IP) established the aircraft on a straight-in final approach configuration, utilizing half flaps and zero thrust with manifold pressure set at 10 inches of mercury on both engines. While the aircraft remained airborne, the IP directed the student pilot to feather both propellers and shut down the engines to simulate an emergency power-off scenario.
Immediately following the engine shutdown, the rate of descent increased significantly. The aircraft touched down on an embankment approximately 45 feet short of the runway threshold. After bouncing, a second touchdown occurred, at which point the nose gear collapsed, causing contact with the runway surface about 55 feet beyond the initial touchdown point.
The investigation
A post-acc examination revealed that the nose wheel was retained by a missing rocking nut. This hardware failure allowed the nose wheel to detach during the impact sequence. Notably, the aircraft had undergone its required 100-hour inspection only eight hours prior to the accident, indicating that the defect was present but undetected during the recent maintenance cycle.
Findings
The primary contributing factor was the mechanical failure of the nose landing gear assembly due to missing hardware. The training maneuver, while standard for simulating engine failures, placed unusual stress on the gear system which was compromised by the absent rocking nut. The instructor's decision to maintain a straight-in final with zero thrust contributed to the hard touchdown on the embankment, exacerbating the structural failure.
Safety message
This incident highlights the critical importance of thorough pre-flight and post-maintenance inspections. Even recent 100-hour inspections can miss loose or missing hardware if not meticulously checked. Training maneuvers involving engine shutdowns should always consider the current airworthiness status of the aircraft, particularly landing gear integrity.