What happened
On 18 July 2003, a Douglas DC-9-83, registration SE-RDL, was conducting a charter flight from Lisbon to Dublin via Londonderry/Eglinton Airport, U.K. During the approach to runway 2 . . . the crew was unaware of an approaching thunderstorm because the available weather information was nearly four hours old. It was only after establishing on the ILS approach that the pilots were notified of heavy rain and active thunderstorms in the area.
As the aircraft descended through approximately 50 feet, the pilot in command gained visual contact with the approach lights. Due to the heavy rain, the pilot activated the windscreen wipers; however, the wiper blade on the pilot's side detached after only a few strokes, significantly reducing visual clarity. Shortly before touchdown, the aircraft experienced a sudden drift to the right. The aircraft landed well to the right of the runway centerline and the right main and nose wheels exited the paved surface onto the gravel runway edge. The excursion caused extensive damage to the aircraft, including damage to the engines, flaps, and fuselage, as well as damage to runway edge lighting. There were no injuries among the 143 passengers or 6 crew members.
The investigation
The Swedish Accident Investigation Board (SHK) examined several technical and operational factors. The investigation focused on the discrepancy in weather reporting, the mechanical failure of the wiper, and the lighting settings at the airport. Investigators analyzed the flight data recorder and cockpit voice recorder, as well as the technical integrity of the windscreen wiper arm. The investigation also looked into the differences between ICAO and Swedish standards regarding the intensity of approach and runway lighting.
Findings
- The crew was operating with valid qualifications and the aircraft held a valid Certificate of Airworthiness.
- The pilots were unprepared for the actual weather conditions due to outdated METAR information.
- The pilot's visual references were severely compromised by heavy rain, darkness, and the failure of the windscreen wiper.
- The airport's high-intensity approach lights were set to a low-intensity standard (3%), which, combined with the lack of local ground lights, made depth and position perception difficult.
- A roll disturbance occurred near the time the autopilot was disconnected, and local wind shear or turbulence may have contributed to the lateral drift.
- Standard periodic checks for windscreen wipers are typically performed without applying the load of heavy rain, which may have masked the underlying attachment weakness.
Safety action
- It is recommended that the Swedish Civil Aviation Administration work toward international harmonization of approach and runway light intensity standards.
- It is recommended that periodic functional checks of windscreen wipers on commercial aircraft be conducted under load to ensure reliability during heavy precipitation.