History of the flight
A Shrike Commander departed Horn Island on a charter flight to
Saibai and Boigu Islands in accordance with the visual flight rules
(VFR). The flight to Saibai took 32 minutes, and a further 13
minutes to Boigu Island. The aircraft then departed Boigu to return
to Horn Island with an expected flight time of 35 minutes.
The pilot reported that he had maintained 5,500 ft until
commencing descent at 35 NM from Horn Island. He tracked to join
final approach to runway 14 by 5 NM, reducing power at 1,500 ft. At
5 NM from the runway, the pilot extended the landing gear and
approach flap and commenced a long final approach.
When the aircraft was approximately 3 NM from the runway both
engines commenced to surge, with the aircraft initially yawing to
the right. The pilot commenced engine failure procedures and
retracted the flaps. He tried a number of times to determine which
engine was losing power by retarding the throttle for each engine,
before deciding that the right engine was failing. The pilot shut
down that engine and feathered the propeller. A short time later,
when the aircraft was approximately 200 ft above the water, the
left engine also lost power. The pilot established the aircraft in
a glide, advised the passengers to prepare for a ditching, and
transmitted a MAYDAY report on the flight service frequency before
the aircraft contacted the sea. The aircraft quickly filled with
water and settled on the seabed. All five occupants were able to
escape and make their way ashore.
Wreckage and impact information
The aircraft ditched approximately 400 m short of the threshold
of runway 14, and settled in 2.5 m of water. It was subsequently
recovered for examination. Although the aircraft had been damaged
during the ditching, it remained essentially intact. The fuselage
was distorted in front of and behind the cabin area as a result of
impact forces. The underside of the fuselage had also been pushed
upwards, and both windscreens were broken. The fuel tanks were
intact, and the fuel tank vents were not obstructed.
Personnel information
The pilot in command had gained a commercial pilot licence in
1994, and worked as a flight instructor until April 1998. He had
been based at Horn Island since April and was subsequently
appointed as the company chief pilot on 11 September 1998. Two days
prior to his appointment he had been endorsed on the Aero
Commander. At the time of the occurrence, the pilot had accumulated
a total flying experience of 2,045 hours, including 566 hours on
multi-engine aircraft, and 79 hours on Shrike Commander
aircraft.
Aircraft information
The aircraft had undergone scheduled maintenance in Cairns on 28
August 1998, and had since flown 100.8 hours. The next scheduled
maintenance was due in 19.2 hours. The horizontal situation
indicator was unserviceable and had been placarded as such, with
the defect being recorded in the maintenance release; however, that
did not preclude the conduct of VFR flight.
No defects that could have contributed to the accident were
found in the airframe or flight control systems. An examination of
the engines and their associated systems did not reveal any defects
that could have led to the loss of power. The right engine fuel
control unit was found to be serviceable but worn. Bench tests
indicated that it provided a fuel flow 10% greater than normal
(approximately 6 L/h).
The right propeller had been feathered before the ditching;
however, the propeller blades had not moved to the fully feathered
position. Examination of the propeller dome revealed that oil
sludge had prevented the propeller piston from driving the blades
to the fully feathered position.
It was determined that the aircraft had been operated within its
normal weight-and-balance range throughout the accident flight
The fuel system of the Shrike Commander consisted of five
interconnected tanks, with one fuel quantity indicator receiving an
electrical signal from a float-type sensor mounted in the fuselage
tank. The flight manual specified that a fuel quantity indicator
was a mandatory instrument for operation of the aircraft.
A single fuel filler point was situated on the upper surface of
the right wing, inboard of the engine, and connected to the right
forward wing tank. It was not possible to assess the fuel quantity
by "dipping" the fuel tank through the fuel filler point. After the
aircraft had been recovered from the sea the fuel system was
drained and found to contain approximately 0.75 L of aviation fuel
and approximately 100 L of seawater. The fuel quantity indication
system was examined. A wire that connected to the wiper arm in the
fuel transmitter unit was found to be broken under its insulation,
causing an intermittent open circuit, which resulted in a
fluctuating fuel quantity indication. When the wire was repaired
the fuel indication system operated normally. The wire to the wiper
arm in the fuel quantity transmitter had been repaired on 7 August
1998 by resoldering the wire onto the wiper arm. The maintenance
manual for the Shrike Commander provided instructions for removal
and replacement of the transmitter unit; however, there were no
instructions for disassembly and repair of any components within
the unit. No other defect was found in the fuel quantity indication
system.
A piece of adhesive paper was found covering the fuel quantity
indicator. The pilot reported that he had covered the indicator
before the flight because he noticed that its indications had been
intermittent on a flight the previous day, and believed that the
fluctuating indications might have alarmed the passengers.
Fuel planning and consumption
Company operations in the Torres Strait involved transporting
passengers and freight on flights between the islands. Pilots would
frequently undertake two or three flights each day, with up to five
sectors per flight. The Shrike Commander was normally flown with
less than full fuel tanks in order to permit greater payloads.
An examination of the aircraft fuel records since the fuel tanks
were last filled on 13 October 1998 revealed that the average fuel
consumption rate was 143 L/h, with an average sector time of 22
minutes. The company operations manual specified the procedure to
be used for fuel planning. That procedure stipulated that the fuel
consumption rate for the Aero Commander was to be calculated at a
rate of 110 L/h, with an additional allowance of 20 L for each
takeoff. The fuel log found in the aircraft revealed that, in
practice, pilots had used a consumption rate of 120 L/h without any
additional allowance for takeoff's.
A fuel log was maintained for each flight; however, during the
investigation significant inconsistencies in the recording of fuel
quantities were repeatedly found between consecutive fuel log
records. The fuel log indicated that before the aircraft was
partially refuelled prior to the accident flight, the fuel tanks
appeared to have 170 L of fuel remaining. Investigation revealed
that the actual quantity was substantially less.
Survival aspects
During the impact sequence, the passenger in the rear left seat
was thrown over the centre seats into the front right seat, which
was unoccupied at the time. The passenger in the centre right seat
received a back injury. Both windscreens were shattered by the
impact. The pilot pushed out the remaining pieces of perspex on the
left windshield with his hands, cutting his finger in the process,
and the passenger who had been thrown into the front right seat was
able to kick out the remaining perspex pieces of the right
windshield. The pilot and the three passengers in the front of the
cabin exited the aircraft through the open windshields. The
passenger in the rear right seat escaped through the emergency exit
window. The cabin rapidly filled with water. All the occupants then
swam ashore, assisting the injured passenger.
All the aircraft seating and seat-belt assemblies were found to
be securely attached to the airframe. Surface corrosion was present
on seat-belt end fittings, which was consistent with salt-water
immersion, and all except one operated normally. The left rear
passenger lap-belt end fittings were stiff to operate, and
difficult to close properly. The end fittings could be easily
placed together incorrectly, allowing improper locking of the
assembly.
The aircraft was not equipped with life jackets, nor was that a
requirement for the intended operation.
Organisational and management information
The company had expanded rapidly over a short period. At the
time of the accident, it was operating 13 aircraft of various
types. The company structure consisted of a managing director who
was based in Melbourne, an operations manager who controlled sales
and the allocation of tasks to aircraft, a chief pilot who managed
the aircrew and assigned their duties, and a total of seven pilots.
The chief pilot had worked for the company for six weeks, and was
his first appointment as a chief pilot. During the course of the
investigation, it became apparent that he had had minimal
experience or guidance in the management of operational personnel.
There was evidence that the new chief pilot had experienced
difficulty in establishing practices that ensured compliance with
safety requirements.
The pilot had been approved as a chief pilot in accordance with
the procedures contained in the Civil Aviation Safety Authority
(CASA) Air Operator Certification Manual. The guidelines in
appendix 16 stated that it was preferable to have a chief pilot who
could "manage the system" rather than one with the best
manipulative skill. A candidate for the position of chief pilot was
required to demonstrate to a CASA Flying Operations Inspector (FOI)
an ability to operate within the regulatory framework. The
checklist for the approval process contained a list of regulatory
knowledge required of a chief pilot, however, no guidance was
provided to an FOI in assessing the overall capability of an
applicant to manage the objectives of the operator, within the
boundaries imposed by aviation safety legislation.
No formal system of responsibility for maintenance control
existed within the organisation. Unscheduled maintenance was
recorded on a whiteboard in the operations room, but responsibility
to ensure that the whiteboard was kept up to date was not a
delegated duty of any of the company personnel.
Pilots verbally reported defects to the chief pilot, who would
then approach the relevant maintenance organisation to arrange for
rectification. The company used four different suppliers of
third-party maintenance, depending on the aircraft. The remoteness
of the location meant delays would frequently occur while spare
parts were sourced.
