Event Details
On 20 August 2006, at 10:20 UTC (12:20 local time), a Socata TB 20 Trinidad, registration F-GDGM, departed from Cannes, France, at 11:05 local time for a VFR flight to Valbrembo Airport. The flight proceeded normally during initial climb, cruise, and approach. During the final landing phase, the pilot configured the aircraft with flaps in the landing position and engine at idle, but did not extend the landing gear. According to the pilot, the audible warning that should have activated in that configuration did not sound. The first contact with the surface occurred on an asphalt taxiway approximately 136 meters past the threshold. The aircraft came to a stop after traveling 198 meters, sustaining damage to the propeller and the lower fuselage.
Aircraft and Operator Information
The aircraft, a Socata TB 20 low-wing monoplane with retractable tricycle landing gear, was built in 1983 (serial number 383). It was powered by a Lycoming IO-540 six-cylinder injection engine producing 250 hp, driving a Hartzell HC-C2YK-1BF variable-pitch propeller. The operator was the sports association "Fly Club" Sondrio. The flight was classified as tourism. On board were the pilot and one passenger.
Personnel Information
The pilot, a 66-year-old Italian male, held a valid private pilot license (PPL) with SEP and English radiotelephony ratings. His total flight time was 980 hours, with 800 hours on type. In the last 90 days, he had flown 8 hours and 45 minutes.
Airport Information
Valbrembo Airport (ICAO: LILV) is located at coordinates 45°43'14"N, 009°35'37"E, elevation 745 feet. It has a single grass runway 02/20, 700 meters long and 50 meters wide. To the east and parallel to the runway lies an asphalt taxiway. According to the Italian AIP, this taxiway is reserved for tow and glider movements; powered aircraft may taxi on it with radio communication. The AIP does not specify that it may be used as a runway for takeoffs or landings.
Meteorological Information
Weather conditions presented no critical elements that could have influenced the event.
Post-Event Tests and Findings
Functional tests of the landing gear extension/retraction mechanism performed after the event found no malfunctions. Additional tests on the audible gear warning horn revealed that, with the gear not extended, the horn was inactive in any flap position and inactive when the throttle was reduced, except when the throttle was moved forcefully. The pilot reported that the warning did not sound.
Examination of the aircraft logbook showed that the last flight prior to the accident was on 18 July 2006 from Bilbao, Spain, to Caiolo, Italy. After the accident, two additional flights were recorded: one on 6 August 2006 from Caiolo to Cannes (where the 50-hour inspection was performed on 18 August 2006) and the accident flight. The later addition of these flights indicates approximate logbook compilation. The pre-accident 50-hour inspection included functional tests of the landing gear that are normally part of the 100-hour inspection, suggesting a possible pre-existing malfunction, but no documentation of such was found.
Landing Surface
The aircraft did not land on the grass runway but on the parallel asphalt taxiway. The investigation revealed that this taxiway was habitually used as a runway, though such use was not authorized in the AIP.