During taxi for takeoff, the crew of the BAe146-100 aircraft
noticed a 'yellow' hydraulic system 'low quantity' warning light on
the aircraft's master warning system panel.
At approximately the same time, a cabin crewmember opened the
flight deck door to alert the flight crew to the presence of fumes
in the cabin. Passengers and two off-duty cabin crew reported a
slowly moving white haze, low on the right side of the passenger
cabin, in the vicinity of row 6. The haze was acrid and transparent
and caused coughing and breathing difficulties.
An off-duty cabin crewmember also went to the flight deck and
told the captain that the situation in the cabin had worsened, that
there was smoke on the right side of the cabin and that passengers
were having difficulty breathing. Because of the urgency of the
report the pilot stopped the aircraft on a taxiway and instructed
the cabin crew to prepare to evacuate passengers through the left
doors. After shutdown procedures were completed, he ordered the
evacuation.
The two operating cabin crewmembers opened the forward and rear
left doors and deployed the escape slides. The two off-duty cabin
crewmembers evacuated first, one through each door, to assist
passengers at the base of the slides.
A passenger reported that cabin crew who stood at the aircraft
doors to control the evacuation and block access to the right doors
were out of view of the cabin. Therefore, the cabin crew could not
see other passengers attempt to retrieve cabin baggage; an action
that clogged the aisle and slowed progress to the exits. However,
cabin crewmembers reported that cabin baggage did not delay the
evacuation.
A cabin crewmember at the base of a slide reported that early in
the evacuation, some passengers struck others that had not yet
cleared the slide. Some fell as they reached the slide base and she
lifted people to avoid a bank-up and the possibility of injury.
Later, the evacuation proceeded in a more orderly manner. Cabin
crew reported that they did not request assistance from able-bodied
passengers during the evacuation.
Medical assistance
The airport Rescue Fire Fighting Services attended shortly after
the evacuation was completed. They offered medical assistance and
administered oxygen to two passengers. Medical assistance was also
offered to passengers and crew on arrival at the airport terminal.
None of the passengers requested medical attention.
Aircraft crew actions
Company emergency procedures required flight crew to don oxygen
masks at any time that smoke or fumes were detected in the cabin.
The procedures also required the flight deck door to remain closed
to avoid flight crew incapacitation from fumes.
Both the pilot and the cabin crewmember that opened the door to
speak to the flight crew reported that they were aware of the
emergency procedure requirements. However, the pilot reported that
the flight crew did not don oxygen masks as there were no fumes in
the area and because the urgency of the cabin crew messages
conveyed the need for an immediate evacuation. The cabin crewmember
reported that it was quicker to open the flight deck door and safe
to do so as there were no fumes in the area.
Cabin crew who had inhaled vapours, or who had assisted
passengers off the escape slide, reported that during the continued
tour of duty they suffered effects that included extreme tiredness,
sore muscles and minor throat and chest problems.
Hydraulic system
Two independent systems provided hydraulic power to the aircraft
flight controls and landing gear. These hydraulic systems were
designated 'green' (left) and 'yellow' (right).
The power generation components were housed in the hydraulic
bay, situated immediately forward of the main landing gear bay,
below the forward rows in the passenger cabin. A light on the
flight deck instrument panel provided a low hydraulic quantity
warning when the fluid level fell below the operating level.
An inspection by the operator found that a leak in a hydraulic
coupling allowed fluid under pressure to escape as vapour into the
hydraulic bay and enter the passenger cabin via gaps in the
sidewall lining. The 'o' ring seal for the coupling was replaced
and the leak stopped. After a number of subsequent flights the
coupling leak re-occurred. On closer inspection it was found that
the coupling had a crack along its threads. The coupling was
replaced.
The company reported that a subsequent Non Destructive Test
(NDT) examination of the cracked coupling revealed that the
coupling had failed through the bottom of a thread due to overload,
which was consistent with having been done up too tightly.
Hydraulic equipment bay sealing
The aircraft manufacturer had generated three service bulletins
that either required or recommended remedial action to improve
sealing between the hydraulic bay and the passenger cabin. A zonal
inspection was also conducted in the area at regular intervals.
At the time of the occurrence the operator had incorporated the
first two service bulletins and had scheduled, but had not
commenced, the third.
