What happened
On 21 January 2002, an Aerospatiale SA365N Dauphin, registration G-PDGN, was conducting a scheduled public transport flight from a heliport at Kyle of Lochalsh, Scotland. The flight, which included one crew member and five passengers, was intended to travel via the Skye Bridge to Rona Island. Due to heavy rain and low cloud, the pilot opted to fly over water to avoid low land-based cloud.
During the flight, significant condensation accumulated on the inside of the windscreen, severely restricting the pilot's forward visibility. Attempting to rectify this, the pilot opened a side window and used a towel to wipe the screen. During this process, the pilot's hands were momentarily removed from the primary flight controls. This resulted in an unintended descent that caused the aircraft to strike the sea surface. The pilot was able to initiate a full power climb and, after receiving assistance from ground crew to locate the landing site, completed a safe landing.
The investigation
The AAIB investigation examined the aircraft's heating and demisting systems, finding no mechanical defects other than a small crack in a windscreen diffuser. The investigation noted that the aircraft lacked an electrical heating element for the glass windscreens, which can hinder effective demisting in heavy rain.
Investigators also reviewed the aircraft's safety equipment and procedures. While the helicopter was equipped with a Radar Altimeter and an Automatic Voice Alert Device (AVAD), the pilot did not recall hearing any alerts during the descent. Furthermore, the investigation looked into the survival equipment on board, noting that while the crew wore survival suits, most passengers did not, due to the discomfort of the provided suits.
Findings
- The primary cause of the incident was the unintended descent caused by the pilot leaving the collective pitch control lever unguarded while attempting to clear the windscreen.
- Heavy rain and high humidity led to significant condensation on the windscreen, which the pilot attempted to clear manually.
- The pilot's lack of an instrument rating meant he was unable to rely effectively on flight instruments to maintain altitude when visual references were lost.
- The lack of electrical heating elements in the glass windscreen contributed to the difficulty in maintaining visibility.
- The investigation highlighted that the proximity to the coast does not guarantee that search and rescue can be completed within the survival window in cold sea temperatures.