What happened
On 4 February 2001, a Shorts 3-60 Variant 100, registration EI-BPD, was conducting a scheduled passenger flight from Dublin to Sheffield City Airport. The aircraft, carrying three crew members and 25 passengers, was performing an ILS approach to Runway 28 under conditions of rain and snow.
During the final stages of the approach, the flight data recorder and cockpit voice recorder captured a critical event: three seconds before touchdown, the propeller blade angle transitioned from the flight range to the ground range. This change caused the propellers to 'disking', resulting in a significant longitudinal deceleration and a downward acceleration of the aircraft. The aircraft struck the runway with a high sink rate and a left wing low attitude. The impact was severe enough to cause the aircraft to bounce and subsequently veer left, eventually running off the runway onto the grass. There were no fatalities and no injuries among the occupants.
The investigation
The AAIB investigation focused on the mechanical state of the engines and the sequence of events leading to the impact. Engineers examined the propeller control rigging and the flight idle baulk, finding that the system was functioning correctly and that the flight idle baulk operated as designed. The investigation also reviewed the aircraft's structural damage, noting that the left main landing gear oleo strut had been compressed with enough force to break its attachment to the sponson. This caused the strut to extend violently, striking the underside of the wing.
Flight data analysis confirmed that the aircraft's descent rate immediately before touchdown was between 12 and 15 feet per second, which exceeded the design limits for a landing without structural damage at that weight. Witnesses in the control tower and near the terminal also observed the aircraft approaching at a higher speed than normal and striking the ground with significant force.
Findings
- The primary cause of the heavy landing was the unintentional selection of the propellers into the ground fine position by the handling pilot while still airborne.
- The sudden change in propeller pitch caused immediate aerodynamic drag and a loss of thrust, leading to the high sink rate and heavy impact.
- The impact forces caused the failure of the left main landing gear assembly, including the destruction of the left main landing gear oleopneumatic strut and damage to the sponson.
- The aircraft's landing weight was 11,100 kg, and the descent rate exceeded the threshold for maintaining structural integrity of the landing gear components.