The British Aerospace BAe 146-200A (BAe 146) was being operated
on a regular public transport service from Brisbane, Qld to
Canberra, ACT. Approximately 5 minutes after take-off the flight
crew detected that smoke was present on the flight deck. They
donned their oxygen masks in accordance with the emergency
checklists that dealt with smoke, fumes or fire and made a PAN
transmission to air traffic control, requesting a return to the
airport. The approach controller issued radar vectors to facilitate
the prompt return of the aircraft to Brisbane and placed the
airport's emergency services on standby. During the descent, the
pilot in command briefed the cabin crew, alerting them to the
possibility of a cabin evacuation.
At the time of the incident, the BAe 146 Quick Reference
Handbook (QRH) contained an emergency checklist procedure titled
Smoke, Fumes or Fire on Flight Deck or in Cabin - Any Source. That
checklist inferred that if the source of the smoke was identified,
the crew should then conduct an appropriate procedure from a choice
of further checklists contained within the QRH. The crew's
selection of an appropriate checklist was dependent on whether the
source of smoke was either from the electrical system, from the air
conditioning system, or from the cabin equipment/furnishings.
Initially believing that the electrical system was the source of
the smoke, the crew commenced the emergency checklist for
Electrical Smoke, Fumes or Fire of Unknown Origin. That checklist
had the potential to take in excess of 8 minutes to complete
because it involved the troubleshooting of the aircraft's
electrical system to determine the source of the smoke. As the
aircraft was close to landing and the crew's priority was to land
as soon as possible, that checklist was not completed. Since the
incident, the aircraft manufacturer issued a revision to the QRH
that simplified and combined the checklists described above. The
new checklist was not generated in response to this particular
incident.
The aircraft landed 20 minutes after take-off without further
incident. Rescue and fire fighting services (RFFS) were in
attendance as the crew stopped the aircraft on the taxiway. The
RFFS personnel inspected the aircraft's electronics bay in an
attempt to trace the source of the smoke, but nothing abnormal was
observed. The aircraft was then taxied to the airport terminal and
the passengers were disembarked. The co-pilot suffered eye
irritation as a result of the smoke, but the passengers and the
other members of the crew reported no symptoms.
Maintenance personnel inspected the aircraft and established
that the smoke and fumes in the cockpit were due to contaminated
bleed air from the number-1 engine. During normal operation, bleed
air from that engine, along with bleed air from the number-2
engine, was fed to airconditioning pack one. Pack one supplied
conditioned air to the flight deck and augmented the passenger
cabin supply. Bleed air from the number-3 and number-4 engines was
fed to pack two, which in normal operation supplied air to the
cabin only.
The engineers addressed the defect in accordance with the Civil
Aviation Safety Authority (CASA) airworthiness directive
AD/BAe146/86 and the British Aerospace Systems Information Service
Bulletin (ISB) 21-150. That ISB required certain actions to be
performed whenever a cabin air quality problem was identified,
which was suspected of being associated with oil contamination of
the air supply from the airconditioning packs. The bleed air supply
from the number-1 engine was isolated and the defect was deferred
in accordance with the aircraft's approved Minimum Equipment List.
The aircraft resumed service and no further smoke or fumes were
evident during subsequent flights.
The defective engine was removed from the aircraft 5 days later
and was returned to the engine manufacturer for overhaul. The
overhaul procedure revealed that the engine's number-2 forward and
aft carbon seals had heavy carbon build-up and were leaking oil.
The manufacturer's report stated that the engine's number-4 carbon
seal also showed evidence of oil leakage. Previous incidents of air
system contamination on this type of aircraft had indicated that
the fumes were a consequence of failures of the engine oil
seals.
It has been noted in previous incidents, both in Australia and
overseas, that there was a reluctance of the crews to use oxygen
masks when air contamination was detected on the flight deck. Those
incidents indicated that operating crews were not aware of their
potential impairment and the consequent effect on their
decision-making ability. The safety implications of that impairment
was reflected in the decision by CASA to adopt a United Kingdom Air
Accidents Investigation Branch (AAIB) recommendation requiring
flight crew to use oxygen masks selected to 100 percent when there
was a suspicion of flight deck or cabin air contamination.
