What happened
On 15 January 2009, an Embraer 190-200, registration G-FBEH, was performing a scheduled passenger flight from Aberdeen to London Gatwick. While cruising at FL370 over Edinburgh, the Senior Cabin Crew Member observed an ice-blue colored substance, appearing to be smoke, emerging from the forward galley sink after water had been poured into it. Although no fire or odor was detected, the flight and cabin crews initiated the 'Electrical System Fire or Smoke' emergency procedure.
As part of the emergency response, the flight crew disarmed the emergency lighting and deployed the Ram Air Turbine (RAT). To manage the situation, the crew also selected off the Integral Drive Generators. This transition to emergency power caused the cabin lights to extinguish and left only a single flight deck display operational. The sudden darkness, combined with the loud noise produced by the RAT's operation, caused significant concern among the cabin crew.
The investigation
The AAIB investigation focused on the behavior of the aircraft's systems under emergency power conditions. The investigation established that while the interphone system's 'PILOT' call button illuminated in the cabin, the corresponding visual indicators on the flight deck's audio panels failed to light up, and voice communication could not be established. Furthermore, the cabin crew found they were unable to use the emergency flight deck access system, which is dependent on flight deck action when the aircraft is on emergency power.
Findings
- The primary trigger for the event was the appearance of blue-colored smoke or steam from the galley sink.
- The interphone system provided a false positive indication by illuminating the call button in the cabin without actually alerting the flight deck pilots.
- The cabin crew were unaware that the flight deck access system becomes non-functional on emergency power.
- The transition to emergency power caused a loss of cabin lighting and communication, which, coupled with the noise of the RAT, led the cabin crew to fear the pilots had become incapacitated.