What happened
On 14 November 2002, a HS.7lar8 Series 2A, registration G-OPFW, was operating a cargo flight from Pisa to Paris. During the flight over the Western Italian Alps, the crew received a Ground Proximity Warning System (GPWS) 'PULL UP' alert. Although the warning was spurious due to an unserviceable radio altimeter, the crew followed company procedure and initiated an immediate climb.
This ascent placed the aircraft into a layer of clouds where it encountered severe airframe icing. Despite the activation of all anti- and de-icing equipment, ice accumulated rapidly on the wings and windscreen, reducing visibility to a tiny fraction of the glass. The accumulation caused a significant loss of performance; the aircraft's airspeed decayed to 120 kt, triggering the stick shaker. Unable to maintain level flight, the aircraft began a descent of approximately 500 feet per minute. Air Traffic Control (ATC) eventually vectored the aircraft toward clearer air, allowing the ice to dissipate and the aircraft to safely continue to Paris, where it landed without further incident.
The investigation
The AAIB investigation examined several contributing factors, including the crew's flight planning, training, and the aircraft's technical state. Investigators found that the crew had been tasked with the flight after a very short rest period. Furthermore, the crew lacked specific local knowledge of the Alpine region and were using manually produced navigation logs that lacked critical flight plan information.
Technical analysis of the aircraft revealed that a repair patch on a right-wing de-ice boot was missing. Additionally, investigators were unable to retrieve data from the Flight Data Recorder because the magnetic tape had adhered to the drive capstan due to a faulty batch of media. The investigation also looked into the company's training protocols and the adequacy of the crew briefing materials provided for the European operations.