Accident Details
On 20 September 2001 at 1205 UTC, a Piper PA-34-200-2 Seneca, registration G-ELBC, was involved in an accident at Stapleford Airfield, Essex. The aircraft was on a training flight with one student pilot under instruction and one instructor on board. The runway in use was Runway 04L, a 1,120-metre long grass runway that was dry. Weather conditions were good with a surface wind of 315° at 8 knots, well below the demonstrated crosswind limit of 17 knots.
Aircraft and Crew
The aircraft, manufactured in 1972, was equipped with two Lycoming IO-360-C1E6 piston engines. The instructor, aged 64, had 8,000 total flying hours, of which 1,500 were on type. The student had 140 hours total experience, with only 2.7 hours on the PA-34-200. Both crew members were wearing lap and diagonal seat belts and evacuated via the right overwing exit without injury. No fire occurred.
Sequence of Events
The student flew two circuits, described by the instructor as well-flown for the student's experience level. Both landings were positive but not heavy. During the take-off roll following the second landing, the right main landing gear collapsed. The crew aborted the take-off, and the aircraft slid off the right side of the runway before coming to rest.
Examination Findings
Examination by the flying club's maintenance organization revealed that the right propeller, right flap, and right wing sustained ground contact damage. The right main landing gear was structurally detached, with both forward and aft attachment fittings fractured. The forward fitting (PN 67041-1) had fractured horizontally across its centre, releasing the pintle bearing. The aft fitting (PN 67043) had a portion of its boss broken away, with distorted lower mount bolt flanges and one fractured across the bolt hole.
Both fittings showed slight ovalisation of attaching bolt holes and appreciable fretting on the mounting face in contact with the spar. The forward fitting had extensive pitting. While some fretting is common, the damage was more severe than usual, suggesting the aircraft may have operated with the fitting attachment bolts undertorqued at some point. Piper Service Bulletin No 956 (March 1992) required a torque check of 50-70 in-lb every 100 flying hours, with replacement of the fitting if torque was below 50 in-lb. Evidence suggested the trunnion pivoted down and rearwards about the aft pintle, fracturing the forward fitting and damaging the aft fitting. No evidence indicated that the fretting damage or pre-existing cracking contributed to the failure. Evidence indicated the fittings failed due to overload, but insufficient evidence was available to determine when the overload occurred.