Accident Overview
On 3 November 2015, Shaheen Air International Flight NL-142, operating a scheduled passenger service from Karachi to Lahore, experienced a serious incident upon landing. The aircraft, a Boeing 737-400 registered as AP-BJO, touched down on Runway 36L. Runway 36R was unavailable due to ILS CAT-III upgrade work. After touchdown, both main landing gears failed sequentially, causing the aircraft to depart the runway. It came to rest on its engines, 8,302 feet from the runway threshold and 197 feet left of the runway centerline. The nose landing gear remained intact. All passengers and crew evacuated safely using emergency procedures.
Investigation Findings
The investigation determined that the accident had multiple contributing factors. The cockpit crew executed an unstabilized approach characterized by high ground speed and an incorrect flight path. Additionally, the left main landing gear (LMLG) experienced a low sink rate at touchdown, and there was probable excessive play in the shimmy damper mechanism linkages beyond specified limits. This condition led to torsional vibrations and breakage of the shimmy damper after touchdown. The resulting torsional excitation from free pivoting of the wheels about the vertical axis caused the LMLG to collapse. Subsequently, the right main landing gear (RMLG) failed due to overload as the aircraft moved on the unprepared surface (the runway edge area).
Conclusion
The official probable cause was identified as a combination of unstabilized approach factors and mechanical deficiencies in the shimmy damper system, leading to the collapse of the main landing gear.