Landing Gear Failure During Training Flight at Madrid Cuatro Vientos (EC-HLQ)

Incident Overview and Flight Details On Tuesday, August 1, 2006, at 14:25 local time, a Piper PA-34-200T with registration EC-HLQ, operated by American Flyers, was conducting a dual-command training flight at Madrid Cuatro Vientos Airport (LECU). The aircraft was equipped with two Continental TSIO-360-E engines. The flight crew consisted of a 23-year-old commercial pilot instructor with 1,100 total flight hours (150 in type) and a 20-year-old student pilot with 174.5 total flight hours (4.5 in type). ## Sequence of Events The crew was practicing takeoffs and landings on runway 28. After completing two takeoffs and landings, during the climb following the second landing, the landing gear unsafe warning light illuminated when the gear was retracted. The crew proceeded to point W of the visual approach chart (over Villaviciosa de Odón) and performed two gear cycles. The three green down-and-locked lights illuminated during extension, but the unsafe warning persisted during retraction. After a third cycle confirmed the green lights, they elected to land. Upon touchdown, the right main landing gear leg began to slowly collapse and eventually detached. The right wingtip contacted the pavement, causing the aircraft to veer to that side. The aircraft remained on the runway and came to a stop near taxiway J-3. Both crew members were uninjured and evacuated the aircraft on foot. ## Aircraft Damage and Maintenance History The aircraft sustained minor damage, including the collapse and detachment of the right main landing gear leg due to the failure of its forward and rear supports. Minor damage was also noted to the tip of a right engine propeller blade and light deformations to the right wing's leading edge, trailing edge, aileron, and flap. The aircraft, manufactured in 1976 (serial number 34-7670336), had a takeoff weight of 1,999 kg. Its last maintenance check was on July 21, 2006, at 7,110.33 total flight hours, during which the landing gear hydraulic fluid level and pressure were verified to be within required limits. ## Technical Analysis of the Failure Laboratory analysis of the forward and rear landing gear supports and their fastening bolts revealed that the materials met the manufacturer's specifications. Both supports exhibited brittle fractures in the trunnion support area, the section of smallest cross-section, with loads applied transversely to the parts in the direction of the gear leg axis, exerting a bending force. The forward support showed no mechanical deformation, nor did its bolts. The rear support, however, displayed plastic deformation in all fracture zones, particularly in the lugs, and one of its bolts showed mechanical deformation in the shank. Microfractographic examination of both supports revealed small micro-domes typical of static overload fractures with load applied at very high speed, practically instantaneously. No indications of progressive failure (such as fatigue, corrosion, or stress corrosion) were observed. Both supports exhibited homogeneous porosity, which was greater in the forward support but remained within the limits established by the drawings. ## Conclusions The investigation concluded that the material of the landing gear supports showed no failure in mechanical or metallurgical specifications. The fractures in both supports were caused by static overload with load applied at very high speed. This indicated that the landing gear was subjected to such loads during one or several excessively abrupt landings, which were determined to be the cause of the accident. The plastic deformation in the lugs of the rear support indicated that the forward support fractured first, and as a consequence, the rear support fractured.