What happened
On April 26, 2015, a privately owned Cessna 172RG, registration JA3857, was conducting a familiarization flight between Iwami Airport and Kagoshima Airport. During the return leg, the aircraft encountered volcanic smoke from Mt. Aso, which significantly reduced visibility at approximately 8,500 feet. To avoid the risk of engine failure while flying through the smoke, the pilot climbed to 12,5 and redirected the flight path.
During the descent toward Kagoshima Airport, the pilot extended the landing gear at 8,500 feet to increase the descent rate. However, to maintain sufficient airspeed for an earlier landing, the pilot retracted the gear at approximately 3,500 feet. Due to a change in the assigned runway and the presence of other traffic, the pilot entered the final approach on a shorter path, bypassing the usual downwind leg where gear configuration is typically verified. Consequently, the aircraft touched down on runway 16 with the landing gear retracted, resulting in a belly-landing that caused substantial damage to the fuselage and propeller.
The investigation
The JTSB investigation focused on why the landing gear was not deployed and why the pilot was not alerted to the configuration error. Investigators examined the aircraft's maintenance history, the cockpit checklist procedures, and the mechanical state of the gear warning system. The investigation also reviewed flight records, including GPS data and air traffic control communications, as well as onboard video footage which confirmed the gear was not extended prior to impact.
Findings
- The pilot failed to extend the landing gear because he forgot the gear had been retracted during the descent and subsequently skipped the gear-down check on the landing checklist.
- The pilot's mental and temporal capacity was diminished by the recent encounter with volcanic smoke and the pressure to land quickly due to following traffic.
- The gear warning horn failed to activate even when the throttle was set to idle. This was caused by a mechanical failure where a screw securing the throttle-linked warning switch had been lost, causing the ground wire to detach.
- The failure of the warning system might have been detectable during the 200-hour periodic inspection performed one week prior to the accident, had the gear warning system been specifically checked.