What happened
On 31 May 1998, a Lockheed L1011-385-1, registration EI-COL, was performing a scheduled passenger flight from Menorca to Manchester Airport. The aircraft, operated by an Irish airline under a wet lease agreement, was conducting an ILS approach to Runway 24R. The commander was manually flying the aircraft with the autothrottle disengaged.
During the landing flare, the pilot increased the pitch attitude to approximately 13 degrees after noting that the rate of descent was not reducing as anticipated. This steep nose-up attitude caused the rear of the aircraft to contact the runway surface. While the landing was described by the crew as firm rather than heavy, the impact resulted in minor damage to the tail bumper, antennae, a drain mast, and a small section of the rear fuselage skin. There were no fatalities and no injuries to the 300 passengers or 12 crew members on board.
The investigation
The investigation examined the flight profiles, aircraft systems, and weight and balance documentation. Analysis of the cockpit voice recorder and radar data revealed that the rate of descent actually increased below 100 feet, rendering the flare ineffective.
Investigators also discovered that the digital flight data recorder (DFDR) had failed to record any data during the flight due to a fault in the airborne integrated data system's central electronics unit. Additionally, a critical error was found in the weight and balance calculations. The commander had recorded passenger weights in kilograms on the loadsheet while treating them as pounds. This error resulted in a calculated landing weight of 304,000 lb, whereas the actual landing weight was approximately 325,985 lb.
Findings
- The primary cause of the tail strike was the incorrect calculation of the aircraft's landing weight, which led to an incorrect approach speed (VREF) being used.
- The pilot's attempt to compensate for a lack of descent reduction by increasing pitch attitude exceeded the manufacturer's recommended limits.
- A clerical error occurred when the commander entered passenger weights in kilograms into a field intended for pounds, significantly underestimating the aircraft's true mass.
- The digital flight data recorder was non-operational due to an electronic fault in the central electronics unit.