British Aerospace Plc BAe 146-100, VH-NJY

Local safety action

As a result of the investigation the operator has:

Scheduled detailed visual inspection of airstair actuators and
fittings during routine maintenance.
Issued maintenance instructions to check that:
- airstair retract switch covers are fitted and correctly aligned
  with the rocker switch;
- adequate tolerances exist when replacing panels around the
  retract switch so that the switch cannot be fouled by surrounding
  panels; and
- the retract switch operates without obstruction and springs
  back to the `off' position.
Amended maintenance schedules to include:
- Operational check of the airstair hydraulic system;
- Inspection for evidence of hydraulic leakage from the `retract'
  actuator banjo fittings and airstair hydraulic coupling and banjo
  fitting; and
- Regular change of airstair banjo fitting `o' rings, as
  required, during heavy maintenance checks.
Amended flight attendant emergency procedure manuals and
training sessions to reflect the requirement for cockpit doors to
be closed in the event of smoke or fumes.
Amended flight crew and flight attendant training modules to
include scenarios that reflect aspects of this occurrence,
including information regarding suitable evacuation paths for
passengers and crew.
Formed a working group within the Australasian Aviation Ground
Safety Council. The working group will develop a Recommended
Industry Practice procedure for response to an aircraft that has an
emergency return to the terminal from a taxi position

The airstair retract switch remained in the `on' position,
thereby allowing sustained hydraulic pressure to be delivered to
the airstair retraction system.
The airstair actuator banjo fitting `o' ring failed.
The non-use of the crew interphone system exposed the flight
crew to the fumes.
Cabin crew opened the flight deck door allowing the mist/fumes
into the flight deck.
Emergency response teams did not provide portable stairs in a
timely manner.
Cabin crew disembarked passengers through the fumes affected
forward left door.

Airstair operation

The electric stand-by pump would have been switched off from the
flight deck shortly after airstair retraction, thereby reducing
hydraulic pressure even though the retract switch was stuck in the
`on' position.

However, after engine start, the engine driven hydraulic pumps
would have delivered pressure to the airstair hydraulic system.
Sustained hydraulic system pressure would then have been delivered
to the airstair retraction system when the pump was engaged.

The failure of the retract switch allowed sustained pressure to
be delivered over an undetermined, but excessive time, to the
airstair retraction system. That exposure resulted in the failure
of the `o' ring and consequent leakage of fluid, as a fine mist,
into the cabin.

Emergency Procedures

Instead of using the crew interphone, to contact the flight
crew, the flight attendants followed common practice and opened the
flight deck door to tell the flight crew about the fumes. This
action exposed the flight crew to the fumes.

The captain's decision not to don his oxygen mask could have
resulted in flight crew incapacitation through exposure to smoke or
fumes.

The information exchange between the flight crew and ground
staff should have indicated a need for portable stairs at the rear
door. The decision to disembark the passengers through the forward
door was not appropriate. Use of the rear door would have provided
passengers and flight attendants better protection from the
fumes.

The absence of suitable emergency ground procedures, delay in
response from ground staff, and the provision of stairs to only the
front door, increased the exposure to fumes for passengers and
crew.

During taxi from the terminal, when the British Aerospace BAe
146-100 was approximately 150 metres from the parking bay, and
while making the pre-flight safety public address, a flight
attendant began coughing due to a slight irritation in her throat
and was unable to finish the presentation. When the second flight
attendant went to the front of the cabin to assist, she too
developed a cough. Both flight attendants saw what they described
as a grey, smoky gas in the airstair region of the left door.

At approximately the same time, the first officer experienced an
involuntary cough and stinging eyes and donned an oxygen mask. A
short time later a flight attendant opened the flight deck door and
advised the flight crew that smoke, or fumes, were filling the
forward section of the passenger cabin. The flight crew turned off
both air conditioning packs and the Auxillary Power Unit and
immediately returned to the parking bay after advising Air Traffic
Control and the ground handling company. During the return to the
bay, the captain opened the left flight deck window and the flight
attendants moved the forward seated passengers to the rear cabin
and instructed passengers to cover their nose and mouth.

When the flight crew reported their intention to return to the
terminal, the ground handling company requested that passengers
remain on board the aircraft at the terminal. The first officer
advised the company that this was not possible as there were fumes
in the cabin. The aircraft arrived back at the parking bay
approximately four minutes after the fumes were first noticed.

Upon arrival at the terminal the captain instructed the flight
attendants to open the doors. A flight attendant returned to the
front of the aircraft from the rear cabin and opened the forward
left door. The second flight attendant opened the rear left door.
The flight attendants reported that there were no portable stairs
available when the doors were opened. The forward flight attendant
called to ground staff in the area and portable stairs were brought
to the forward left door. The flight attendants elected not to
attempt airstair activation as that was believed to be the source
of the smoky gas.

To avoid delay, flight attendants disembarked passengers through
the forward door, in the vicinity of the fumes. They reported that,
as they were coughing, they could not speak to passengers during
the disembarkation.

The company later reported that the urgency of the situation
might not have been conveyed to ground services during the initial
advice of the aircraft's return to the terminal.

After passengers had disembarked, Aviation Rescue Fire Fighting
(ARFF) personnel advised the flight attendants to sit outside the
aircraft for ten minutes. The flight attendants later underwent a
medical check at the recommendation of the company. Neither the
captain nor first officer sought medical attention following the
incident. All crewmembers have since returned to duty.

Some passengers later reported that they experienced coughing,
watering of the eyes, and respiratory irritation during the event.
They also reported that medical attention was not available at the
terminal. The ground handling company reported that when passengers
reached the terminal, staff did not call a doctor when requested by
passengers. They also reported that ARFF personnel had recommended
that passengers go outside into the fresh air but few passengers
had followed that advice.

Subsequent investigation revealed that neither the operator nor
the ground handling company had emergency response procedures in
place to cover the situation of an aircraft emergency return to the
terminal from a taxi position.

Integral airstair

The aircraft was fitted with an integral stairway (airstair) at
the forward left door. However, portable stairs were often used in
place of the narrow integral stairs for convenience and ease of
boarding.

The operator reported that the forward door airstair had been in
use before the flight but had been retracted and replaced by
portable stairs prior to boarding passengers.

The airstair was operated from inside the aircraft. It was
extended manually, but retracted by hydraulic pressure when the
airstair-selector `retract' switch was pressed and held in
position. This procedure allowed hydraulic fluid (Skydrol) to pass
under pressure through a series of lines and valves to activate
airstair retraction. When the airstair was retracted, and the
airstair-selector switch was released, the rocker-type switch was
designed to spring back to the `off' position. The airstair was
then pushed along tracks to a rearward, stowed position out of the
doorway.

While the aircraft was on the ground with engines off, an
electric stand-by pump was used to top-up and maintain pressure for
airstair retraction. After engine start-up, engine driven pumps
delivered pressure to the airstair hydraulic system.

An examination of the integral airstair by company engineers
revealed that the airstair selector switch had stuck in the
`retract' position, and also revealed a failed `o' ring in the
retraction jack `banjo' fitting in the airstair actuator. During
the examination, other `o' rings had also shown signs of
deterioration.

The operator reported that an internal failure caused the switch
to be stuck in the `retract' position and also noted that the
switch was flush with the surrounding panel. The operator
considered it possible that the body of the switch became fouled on
the panel and remained in the `retract' position.

The operator also reported that the aircraft maintenance manual
stated that the airstair `retract' switch should have had a hinged
flap cover. The flap was missing and an engineering order had not
been raised for its removal.

Crew emergency procedures and manuals

Flight crew emergency procedures for smoke or fumes required
flight deck crew to don oxygen at any time that smoke or fumes were
evident. The captain reported that he did not don the oxygen mask
when he was alerted to the presence of smoke or fumes as the fumes
did not affect him. He also considered it more important to return
the aircraft to the parking bay to disembark passengers than to
stop and don his oxygen mask.

Flight crew emergency procedures for smoke or fumes also
required that the flight deck door remain closed. However, this
procedure was not reflected in the flight attendant emergency
procedures manual. The flight attendants were unaware of the
requirement to keep the flight deck door closed.