Airbus Industrie A320-211, VH-HYT

Local safety action

As a result of this investigation the operator advised that the
following actions were taken:

All maintenance personnel were made aware of approved company
maintenance procedures relating to APU's.
Company personnel were instructed on the proper reporting
procedures to ensure prevention of any further breakdown in the
reporting chain.

As a result of this investigation the operator advised the
following:

The role and responsibility of personnel posted at reduced or
single-engineer bases are to be clarified and reviewed.
Arrangements for the ongoing supervision of personnel posted at
reduced or single-engineer bases are to be reviewed.
The occurrence is to be reviewed with respect to the company's
standard crew resource management policy.
The role and responsibility of ground personnel are to be
reviewed and clarified with respect to non-normal and emergency
situations.

It is likely that during the time the engineer was away from the
APU, with the oil dolly still connected, the faulty spool valve in
the oil delivery line permitted the oil to continue to flow into
the APU, resulting in an overfilled condition with excess oil
draining into the tailpipe. The APU then surged and automatically
shut down. The surge was probably caused by some of the excess oil
within the APU escaping through the bearings and entering into the
combustion chamber, where it was ignited. This would have resulted
in a rapid increase in the exhaust gas temperature. Flame from the
combustion would then have "torched" through the turbine stage into
the tailpipe, where it ignited the overflow oil that had drained
into the tailpipe.

The pilot in command was initially provided inadequate
information regarding the APU problem. He was aware that the APU
had shut down, and was informed that there was an APU fire.
However, this was not confirmed by an ECAM message due to the
location of the fire in the tailpipe. This series of events was an
unusual situation and did not fit with the pilot in command's
expectations of an APU fire. Had he been properly informed of the
circumstances of the fire, it is unlikely that he would have
considered it necessary to inspect the APU. Consequently, he would
have been able to more rapidly respond to ensure the safety of the
passengers and crew.

The operator was unable to immediately follow its
post-occurrence investigation procedures due to delayed and
incomplete reporting of the circumstances of the occurrence.

On 19 February 1999, while on the tarmac at Townsville with the
auxiliary power unit (APU) operating, the crew of A320 Airbus
VH-HYT observed an advisory message for "oil quantity below 1/4" on
the electronic centralised aircraft monitoring (ECAM) cockpit
display. The limitations section of the operator's A320 Operating
Manual stated that the minimum before start APU oil quantity was
1/4. However, it also noted that with the ECAM low oil level
message displayed, the APU should be considered unserviceable until
an engineering inspection was conducted. This included a check of
the APU oil level and inspection of the APU compartment and air
intake for oil contamination.

The pilot in command notified the operator's Townsville
maintenance engineer of the ECAM APU oil quantity message. The
operator's procedure in response to a low APU oil quantity ECAM
advisory message required that the APU be inspected for gross oil
leaks and that the aircraft maintenance log APU oil servicing
records be reviewed to determine oil consumption. However, because
the APU bay was a controlled fire zone, the operator's maintenance
procedures specified that the APU access door not be opened while
the unit was operating.

The engineer opened the APU bay access door and inspected the
operating APU for oil leaks. He then returned to the cockpit, where
he consulted the aircraft maintenance log to review the APU oil
servicing records. Noting that oil had not recently been added to
the APU, the engineer advised the pilot in command that he would
replenish the APU oil.

Passengers were already on board for the flight to Brisbane.
Because of the prevailing hot and humid conditions, the engineer
decided that, for reasons of passenger comfort, he would leave the
APU running while he replenished the oil. This decision to add oil
to the APU while it remained operating was in violation of the
operator's standard policy and procedures, which stated that
replenishment of APU oil may only be carried out while the unit is
not operating.

The engineer connected the oil supply line from a mobile oil
dolly to the operating APU. The oil dolly was equipped with a
pressurised supply tank, with delivery of oil from the tank being
controlled by a hand-operated spool valve in the oil delivery line.
The engineer had determined that 1 L of oil should be added to the
APU, and he calculated that it would take 15 seconds to deliver
that quantity from the oil dolly into the APU. After the oil had
been added, the engineer returned to the cockpit to observe whether
the ECAM advisory message had extinguished, leaving the APU access
hatch open and the oil delivery line still connected to the
operating APU. The ECAM advisory remained illuminated, so the
engineer returned to the APU bay. As he was climbing onto the
workstand, a fire broke out in the APU tailpipe and the APU shut
down.

The surface movement controller in the control tower observed
fire and smoke coming from the tail of HYT. He sounded the crash
alarm and radioed HYT on the surface movement control frequency,
but there was no response. Three fire trucks responded immediately
and parked in a fanned position around the aircraft's tail, with
one truck being parked under the APU exhaust. Two firemen climbed
onto the top of that truck to better observe the source of the fire
and to determine the appropriate fire-fighting measures to be
employed.

The crew had been conducting pre-flight checks when they noticed
the APU shutdown. At the same time, they heard the sirens from the
fire trucks, and a customer service officer entered the cockpit and
notified the crew that the APU was on fire. However, the engineer
also entered the cockpit and stated that the fire was under
control, but he did not inform the pilot in command that the fire
was located in the APU tailpipe and not in the APU bay.

HYT was equipped with a fire and overheat detection system
located in the APU compartment. The system was designed to provide
for automatic APU shutdown and agent discharge in the event of fire
or overheat in the APU compartment while the aircraft was on the
ground. A fire warning light was fitted to the overhead panel in
the cockpit to alert the crew in the event of an APU fire. However,
because the fire was located in the APU tailpipe, it did not
activate the APU fire detection system and consequently there was
no fire warning. After being advised that an APU fire had occurred,
the pilot in command elected to leave the aircraft to obtain
further information about the nature of the problem and its effect
on the safety of the aircraft. Before leaving the cockpit, he made
a public address to the passengers to advise that the aircraft had
experienced a problem with its airconditioning system, and that
this would delay the aircraft's departure.

The pilot in command then left HYT through the left forward
cabin door (L1) but did not brief the cabin manager, who was
stationed at L1, about the nature of the problem. The cabin manager
was therefore unable to plan for the possible evacuation of
passengers from the aircraft. The pilot in command proceeded to the
rear of HYT, where one of the firecrew informed him that the fire
was still burning. The firecrew were unaware that passengers were
already on board and when the pilot in command asked if they wanted
the passengers off the aircraft, the fire controller instructed the
pilot in command to disembark the passengers immediately. However,
no instruction was given regarding doors that were not to be used
for the disembarkation.

The pilot in command then ran back and instructed the cabin
manager stationed at door L1 to disembark the passengers. Up until
that point, the only information that the cabin manager had been
given about the fire was from the customer service officer when the
officer had entered the aircraft to advise the pilots of the
problem. None of the other flight attendants were aware of the
situation until the order to disembark the passengers was given.
All passengers and crew were then disembarked through both the
front and rear entry doors on the left side of HYT.

The airport fire crew discharged three 5 kg carbon dioxide
bottles into the APU exhaust and the fire was extinguished. When
the fire controller determined that HYT was safe, he released it to
the crew. The engineer conducted a damage inspection of the
aircraft and it was dispatched with the APU inoperative.

On arrival at Brisbane, the pilot in command lodged a general
flight report stating that HYT had sustained an APU tailpipe fire
at Townsville. The report noted that there was no fire warning or
ECAM display associated with the APU tailpipe fire. The same day,
the engineer reported to the operator's Melbourne maintenance base
that HYT had sustained an APU tailpipe fire. Neither of these
reports mentioned that the APU oil had been replenished while the
unit was operating.

On 4 March 1999, the engineer lodged an accident/injury report
of the event with the operator, noting that an APU tailpipe fire
had occurred. On 5 March 1999, BASI received an air safety incident
report from the company concerning the occurrence and on 8 March
1999, BASI also received an air safety occurrence report from RAAF
Townsville.

On 10 March 1999, the operator interviewed the engineer. During
the interview, it was established for the first time that the APU
oil had been replenished while the unit was operating. The engineer
advised the operator that on 21 February 1999, he and another
engineer had inspected the spool valve of the oil dolly. The
inspection was conducted to determine if oil continued to flow from
the delivery hose with the spool valve in the closed position. The
inspection revealed that the spool valve was faulty and that it had
probably been faulty at the time of the occurrence.