What happened
On 20 August 2005, a Boeing 757-225, registration TF-ARD, was performing a scheduled passenger flight from Palma, Majorca, to London Gatwick. Following a period of weather-related delays at Palma Airport, the aircraft departed in instrument meteorological conditions. Shortly after climbing to approximately 3,000 ft, the aircraft entered a small but intense area of hail. The encounter was marked by a loud noise within the flight deck, and the aircraft's weather radar subsequently failed.
Despite the damage, the crew elected to continue the flight to Gatwick rather than returning to Palma, as the damage to the co-pilot's windscreen was limited to the outer, non-structural layer. During the flight, the crew inspected the engine nacelles and wing leading edges, finding no apparent damage. The aircraft landed safely at Gatwick without further incident.
The investigation
Investigators examined the aircraft's radome, landing lights, and various windows. The radome's outer skin had disbonded from the honeycomb structure, causing it to deform inward and impede the movement of the weather radar antennae. The landing light lenses were found to be shattered, and pieces of this debris had caused gouges on the outer panes of several cabin windows. The co-pilot's windscreen showed extensive impact points on its outer layer, though the structural integrity of the screen remained intact.
Flight data recorder analysis showed no abnormal vertical or longitudinal accelerations during the period of the hail encounter. Additionally, the investigation noted that the weather radar system's inability to detect the hail was a known limitation, as ice crystals and hail can produce very small or even no radar returns compared to heavier rain.
Findings
- The aircraft encountered a localized area of intense hail during its departure from Palma.
- The weather radar failed to detect the hail due to the inherent limitations of radar technology regarding the reflectivity of hail and ice crystals.
- The encounter caused significant damage to the radome, landing lights, and the outer layer of the co-pilot's windscreen, but the aircraft remained in a safe condition for the remainder of the flight.