Background
On Saturday, July 7, 2001, at 16:10 local time, a Piper PA-34-200T aircraft, registration EC-EQV, was preparing for a training flight at Tenerife Norte Airport. The flight was a dual instruction mission with an estimated duration of 1 hour 30 minutes, originating and terminating at the same airport. Onboard were three people: a student pilot, an instructor, and an accompanying instructor.
Accident Sequence
The crew received takeoff clearance and began taxiing to Runway 30, entering via taxiway C-4. During the takeoff roll, when the aircraft reached approximately 65 knots, the instructor noticed the left wing tending to lower. He took control, attempting to keep the wing up, shut down the left engine, feathered its propeller, and began decelerating. As speed decreased, aerodynamic control effectiveness diminished, and the left wing eventually dropped, striking the pavement. The aircraft then yawed around the left wingtip, exited the runway, and came to a stop within the runway strip. The crew secured the aircraft by shutting off fuel and the master switch, then evacuated.
Investigation Findings
The aircraft sustained damage to the left main landing gear leg, which was broken into two pieces, along with damage to the left wing and left propeller. No other damage was reported. Laboratory examination of the broken landing gear leg revealed the following:
- The leg showed widespread paint detachment and corrosion pitting, with irregular paint application. At the intersection of the two tubes forming the shock strut, paint had been mechanically removed, leaving deep scrape marks.
- A pronounced indentation was found on the forward face of the strut near the fracture surface.
- Material testing (hardness, conductivity, chemical composition, metallography, macrofractography, and microfractography) indicated that the material properties were adequate for the intended use.
- The fracture was a semi-brittle tear initiated at a point on the outer surface, which propagated instantly, and the remaining section failed under static bending overload.
- Adjacent to the fracture origin was a deep indentation that acted as a mechanical notch, significantly reducing local strength.
The likely fracture sequence was that during the takeoff roll under normal loads, a local overload occurred at the notch due to its stress concentration, initiating a semi-brittle tear, followed by failure of the remaining tube section under normal bending stresses.
Conclusions
The investigation concluded that the primary cause of the fracture was a semi-brittle tear, with the mechanical notch acting as a preponderant factor. The origin of the notch could not be determined; it may have existed before the flight or been produced during the takeoff roll.