Event
On January 8, 2001, at 13:30 local time, a Cessna 177-RG (registration EC-GCX) was on a private pleasure flight from Madrid/Cuatro Vientos Airport to Casarrubios del Monte aerodrome. Shortly after takeoff, the pilot retracted the landing gear but the indicator lights for "gear up and locked" did not illuminate. The pilot contacted the control tower at Madrid/Cuatro Vientos and reported the problem, then proceeded to the Navalcarnero area. Standard gear extension procedures and emergency manual extension attempts failed to lock the gear down.
Pilot Actions
The pilot decided to divert to Casarrubios del Monte. Upon arrival, ground personnel advised a low-altitude, low-speed pass to visually assess the gear position. During this maneuver, the pilot reported that the engine stopped, necessitating an emergency landing. The landing gear collapsed on touchdown, causing the propeller and lower fuselage to contact the runway. The aircraft slid on its belly before stopping. The pilot was uninjured. The aircraft sustained minor damage to the landing gear, lower fuselage, propeller, and engine area.
Inspection Findings
Post-accident inspection of the aircraft revealed a hydraulic fluid leak from a cracked tube in the landing gear extension/retraction system. The tube had a crack approximately 1 cm from the power pack fitting, extending around 240° of the circumference. Nearby microcracks were also found. The tube showed no protective coating except for a flexible plastic sleeve on two portions. Areas unprotected by the sleeve exhibited surface wear and uniform corrosion, with sulfur and chlorine present in corrosion products. Metallurgical analysis indicated intergranular corrosion attack, which initiated fatigue cracks that propagated under static installation stresses and vibration-induced stresses. The tube was located beneath the battery, possibly exposing it to corrosive battery fumes or liquid spills. The engine was inspected and no anomalies were found.
Conclusions
The hydraulic tube failed due to intergranular corrosion that led to fatigue cracking under static and vibration stresses. Corrosion may have stemmed from battery gases or spills. No evidence was found to support the pilot's report of an engine stoppage before landing.