What happened
On August 1, 2006, a PIPER PA-34-200T, registration EC-HLQ, was performing dual instruction flight operations at Madrid Cuatro Vientos Airport. The flight crew, consisting of a flight instructor and a student pilot, had completed two take-offs and landings. During the climb following the second takeoff, the crew attempted to retract the landing gear but observed a red warning light indicating the gear was not up and locked.
The crew proceeded to a visual approach point near Villavictosa de Odón to perform gear cycles. While the gear appeared to lock in the down position (indicated by three green lights), the unsafe warning light reappeared whenever the gear was retracted. After a third attempt to cycle the gear, the crew decided to land. Upon touchdown, the right main landing gear began to yield and eventually collapsed. The impact caused the right wingtip to contact the pavement, resulting in the aircraft veering toward the right side of the runway. The aircraft came to a stop near taxiway J-3. The crew sustained no injuries.
The investigation
CIAIAC investigators examined the aircraft's landing gear assembly, specifically focusing on the front and rear supports of the right main gear. The investigation included a laboratory analysis of the trunnion supports and their mounting bolts. The inspection of the aircraft's maintenance records showed that the last maintenance check had been completed on July 21, 2006, and the hydraulic fluid levels and pressures were within required limits.
Microfractographic analysis of the broken supports revealed the presence of small micro-cups, which are characteristic of static overload failures occurring at very high speeds. The investigation found that the materials used in the supports met all manufacturer specifications and that there were no signs of progressive failure, such as fatigue or corrosion. While the front support showed no mechanical deformation, the rear support exhibited plastic deformation, particularly on the lugs, and one of the mounting bolts was also deformed.
Findings
- The failure of the right main landing gear was caused by static overload applied at a very high velocity.
- The investigation concluded that the gear supports were subjected to excessive loads during one or more extremely hard landings.
- The failure sequence began with the breakage of the front support, which subsequently led to the failure of the rear support due to the resulting mechanical stress.