Accident Overview
On October 15, 2017, at approximately 11:45 local time, a Cessna F177RG, registered as F-BSHB, sustained substantial damage during a gear-up landing at Ambérieu aerodrome. The privately operated flight, conducted under general aviation rules, carried the pilot and three passengers. The aircraft touched down on its belly, slid about 100 meters, and came to rest on the runway.
Flight Sequence
The pilot departed Ambérieu with three passengers for a local flight near Mont Blanc. On return, he joined the downwind leg for runway 19R. Feeling slightly fast, he selected approach flaps and delayed gear extension. During base leg, while performing the pre-landing checklist, he perceived the green light indicating the landing gear was down and locked as illuminated. On final approach, he reduced power, initiated descent, and selected landing flaps. The aircraft contacted the runway with the gear retracted.
Pilot Information
The pilot held a Private Pilot License (PPL(A)) and had accumulated 730 total flight hours, including 660 as pilot-in-command, with 13 hours on the accident aircraft in the preceding three months.
Technical Findings
Post-accident examination revealed no anomalies in the landing gear system or position indication when the aircraft was powered on and the gear extended. However, the TNS (Takeoff/Not Secure) warning horn microswitch, designed to activate when manifold pressure drops below approximately 12 inches of mercury, was found misadjusted. The switch only activated when the throttle was fully aft (idle cutoff position) rather than at the 12-inch Hg threshold specified in the flight manual.
During the approach, a passenger's video footage (taken until about 500 feet altitude) showed the amber gear-up indicator illuminated, manifold pressure below 10 inches Hg, flaps in landing configuration, and no audible TNS alarm.
The pilot stated that on base leg, a possible sun reflection may have caused a misperception of the gear indicator status. He also noted that he did not hear the TNS alarm on final.
Probable Cause
The source does not state a probable cause.