Incident Description
On Thursday, 22 January 2009, at 11:54 local time, a Cessna F-172-RG (registration EC-DMR) operated by Top Fly was conducting an instrument flight rules (IFR) instructional flight from Sabadell Airport (Barcelona). The aircraft, with an instructor and a student onboard, had departed at 08:50 and performed a normal ILS approach to Reus Airport before returning to Sabadell.
Entering the right-hand traffic circuit for runway 31, the crew lowered the landing gear but the indicating light did not illuminate. Visual inspection confirmed that the right main landing gear leg was not fully extended. After completing normal and emergency procedures, the crew contacted the control tower at 10:22. A fly-by of the tower confirmed the asymmetrical gear position.
After further attempts to extend the gear while remaining airborne away from the airport, the crew reviewed the emergency landing procedure and returned. A second fly-by verified the gear position. The instructor then landed the aircraft, shutting down the engine and electrical system once on the ground. During the landing roll, the instructor kept weight on the left wheel. After nearly stopping, the right wing dropped, its tip contacting the ground, and the aircraft performed a 180-degree turn.
The control tower alerted the airport firefighting service, which applied foam to the runway. Both occupants were uninjured and evacuated without assistance.
Aircraft Damage
The right wingtip and horizontal stabilizer (which also contacted the ground) were damaged. The right main landing gear leg and nose wheel leg sustained significant damage. No third-party damage occurred.
Investigation Findings
Post-incident inspection revealed that the actuator for the right main landing gear leg was cracked, preventing proper extension. The actuator, part number 9882015-2, was sent for laboratory analysis.
Three cracks were found in the annular section near two orifices where the ring joins the actuator body. Crack A1 and A2 penetrated through the upper hole walls; crack B ran through one wall of the inner orifice, with an additional small non-penetrating crack on the outer wall.
Material analysis showed no defects in the actuator material. Fractographic examination indicated the fracture mechanism was microvoid coalescence, consistent with a static overload failure under tensile load causing local circumferential stresses.
Maintenance History
The aircraft had a valid airworthiness certificate and had logged 6,619:45 flight hours. It was primarily used for flight training. Maintenance records showed compliance with Cessna Service Bulletin 01-2-RG MLGA Rev. 2, which mandates inspection of main landing gear actuators for fatigue cracks. The actuator had been inspected during a 50-hour check on 9 April 2008 at 6,196 hours. The bulletin specifies that if cracks are found, the actuator must be replaced; if not, it must be modified and periodically inspected. The inspection areas in the bulletin did not exactly coincide with the fracture location in this incident.
Crew Information
The instructor, occupying the right seat, held a Commercial Pilot License (CPL(A)) with instrument and instructor ratings, and had 3,300 total flight hours (900 on type). The student held a Student Pilot Permit (SP(A)) and was training for a CPL with instrument rating.
Previous Incidents
The NTSB reported 10 previous occurrences of similar actuator failures on Cessna models, with causes including actuator overload, fatigue, and hydraulic system issues.