Description

On 15 January 2009, an Embraer 195-200 being operated by UK Regional Airline Flybe was passing overhead Edinburgh UK at FL370 at night in VMC when communications problems between the flight deck and cabin crew occurred following the selection of emergency power as a precautionary measure after smoke, considered to possibly be of electrical origin, had been observed in the galley. An en route diversion with an uneventful outcome was accomplished.

The Event

The following is taken from the UK AAIB Final Report on this event:

"The aircraft was on a scheduled passenger service from Aberdeen to London Gatwick. As it cruised overhead Edinburgh at FL370, the Senior Cabin Crew Member (SCCM) poured half a jug of water down the forward galley sink. He saw that “smoke”, apparently “ice‑blue” in colour, immediately began to emanate from the sink. He assumed that this was not steam, as the jug of water had been drawn from the boiler some minutes previously, and he checked the galley area for signs of fire. He called another cabin crew member to the forward galley, and they both assessed that the “smoke” was not steam. There were no signs of combustion, and neither crew member detected an odour.

The flight deck and cabin crews took appropriate emergency action. In the course of the ‘Electrical System Fire or Smoke’ procedure, the flight crew disarmed the emergency lighting, deployed the Ram Air Turbine (RAT) and then selected off the Integral Drive Generators (IDGs), which are the engine-driven sources of main electrical power. This caused all the cabin lighting to extinguish; it was early morning and there was little ambient light. In the flight deck, only one Primary Flight Display (PFD) and one Multi‑Function Display (MFD) remained operating.

The RAT is positioned on the right side of the aircraft nose, forward and below the forward service door; ram air drives a two-bladed ‘propeller’ connected to a generator, supplying emergency electrical power to the aircraft’s systems. The cabin crew heard the noise caused by the RAT’s operation, for which they were unprepared, and which they described as “horrendous”. The cabin lights extinguished soon afterwards.

The SCCM attempted to call the flight crew on the cabin interphone system, by pressing the PILOT call button. The green light above the button (Figure 1) illuminated, but the flight crew did not answer. Despite repeated attempts, using handsets in both the forward and rear galleys, the SCCM could not establish communication with the pilots in this way.

The “smoke” diminished and eventually ceased. Nonetheless, the cabin crew became concerned at the darkness in the cabin, the unexplained noise from the forward part of the aircraft, and the lack of communication with the flight crew. They became concerned either that the flight crew might have become incapacitated or that a serious emergency had developed in the flight deck. After some minutes they decided to attempt to access the flight deck using the emergency flight deck access system1, but this, too, did not function and the cabin crew were unable to gain access to the flight deck.

Concern amongst the cabin crew continued until the commander made a public address announcement explaining that the aircraft was diverting to Newcastle; the cabin crew then recognised that their concerns were unfounded."

The Investigation

The Findings were that:

"Whilst the “smoke” was the initiating factor in this incident, it was the performance of some of the aircraft’s systems whilst the aircraft was on emergency power which caused serious concern amongst the crew. The PILOT function of the interphone system seemed, to the cabin crew, to indicate that it was functioning normally. However, the CAB pushbutton in the flight deck did not illuminate, and no voice contact was possible. The cabin crew did not attempt to use the EMER PILOT function, as this would involve an emergency call, which differed (in the cabin crewmembers’ perception) from the normal call only in the number of chimes.

The ‘false positive’ indication of the PILOT call was crucial to the incident; had the PILOT call not appeared to function correctly, it is probable that the cabin crew, instead of contemplating incapacitation of the flight crew or serious emergency on the flight deck, would have attempted to establish communication using the EMER PILOT call. The operator’s operations manual did not detail the functioning of the interphone and flight deck access systems when the aircraft was on emergency power, and training had not made the crew aware of this functioning."

A Special Bulletin S1/2009 was issued during the early stages of the investigation containing four Safety Recommendations to the aircraft manufacturer in respect of operation of the aircraft when supplied only with emergency electrical power. These Recommendations are replicated in the Final Report together with the aircraft manufacturer’s response.

Related Articles

• Airworthiness

Further Reading

• For further information, see (Final Report in AAIB Bulletin 1/2010) Note that the aircraft involved in this Incident was an Embraer 195 (length: 38.65 m) and not the slightly smaller Embraer 190 (length: 36.24 m) stated in the AAIB Report, although in all relevant systems respects, the two variants are identical.