Pilot information
The helicopter pilot held a commercial pilot licence, a valid
class 1 medical certificate and a NVFR rating. He was endorsed to
fly Hughes 500 helicopters (also known as Hughes 369HS) and was
current at night flying. He held a helicopter float endorsement and
had successfully undergone helicopter underwater escape training on
30 April 1995.
At the time of the accident the pilot had a total flying
experience of 8,462 hours, of which 7,882 were in helicopters,
including 1,408 hours in Hughes 500 helicopters. He had flown a
total of 545 hours at night, and his total instrument flight time
was 10 hours. A biennial flight review had been conducted on 8
March 1996, and his most recent company flight check was conducted
on 14 January 1997. In the four years prior to the accident, the
pilot had flown in excess of 800 marine pilot transfers at night.
Most of those had been in Hughes 500 helicopters. The pilot
described the helicopter landing sites on the sister ships as more
than adequate for a Hughes 500 helicopter, which had a main rotor
diameter of 8 m.
The pilot had been rostered for duty in accordance with an
exemption against Civil Aviation Order (CAO) 48 - Duty Times which
applied to company pilots engaged solely in marine pilot transfer
operations. At the time of the accident, the helicopter pilot had
been on call solely for marine pilot transfers for the previous two
days, following two days off. After awaking at 0730 on 25 February
1997, he flew the first marine pilot transfer for the day between
1830 and 2030; the flight time was about 0.4 hours. He then slept,
before departing Gladstone at about 0058 on the accident flight.
The pilot reported that he had not engaged in any strenuous
activities during the rostered duty period and had flown only 0.7
hours in the 24 hours before the accident.
In recounting the accident, the pilot expressed the view that
conditions on the night of the accident were such that no part of
the flight would have been considered difficult for an experienced
marine transfer helicopter pilot in a Hughes 500 helicopter. He
reported that the flight to the ship was normal. After the
passenger had boarded the helicopter, the pilot checked for
obstructions in the intended direction of taxi and takeoff and
noted the crane jib. He planned to depart to the north-east after
clearing the left side of the ship and noted that two ships
positioned to the north, as well as the lights of Gladstone to the
west, would give him a good visual reference.
The pilot's position in the left front seat of the helicopter
provided an excellent view forward across the deck, to the left and
above, and above to the right. His view immediately to the right
would have been slightly restricted by the passenger.
The pilot reported that he took-off and manoeuvred the
helicopter into a low hover, then taxied across the hatch towards
the left side of the ship. He yawed the helicopter slightly right
in anticipation of weathercocking as the helicopter cleared the
ship to the left side. The helicopter weathercocked as expected.
The pilot said that he then stabilised the aircraft alongside the
ship briefly, maintaining a constant altitude and keeping pace with
the ship. This was in accordance with company procedures for
departing from ships with obstructions. With the ship to his right
and the lights of two other ships in the forward left quarter of
his field of view, he reported that he established a
zero-bank/zero-yaw attitude in preparation for transferring to
flight by sole reference to the cockpit instruments. To be sure the
helicopter would move away from the ship, he yawed 10 to 15 degrees
left, then simultaneously increased power and moved the cyclic
control forward to accelerate and climb away. Within a few seconds
of initiating this sequence, he felt a jolt and the helicopter
pitched nose-up and rolled to the right. Despite flight control
inputs, he was unable to counteract the roll to the right. The
helicopter then struck the water. The pilot believes that the
ship's crane was swung into the helicopter's rotor arc as he took
off from the ship.
Aircraft information
The Hughes 369S is equipped with an articulated main rotor
system, which permits the rotor blades to feather (change pitch
angle), flap (move up and down vertically) and to lead and lag in
the plane of rotation. The blades also have washout to equalise
lift across the blade. When the blades are rotating, aerodynamic
and centrifugal forces act on the rotor disc. These forces are
finely balanced to keep the rotor disc stable and acting in the
desired manner. If a critical component, such as a rotor blade, is
damaged, the rotor disc is likely to become immediately unstable
and its action unpredictable. During the investigation the pilot
supplied a report, which proposed a mathematical model to verify
his evidence. The report's author was not qualified as a helicopter
aerodynamicist or as an accident investigator.
The helicopter was loaded within its approved centre-of-gravity
and gross weight limits at the time of the accident.
The approved flight manual for the Hughes 369 states that
controllability during hovering downwind, and both sideward and
rearward flight, has been demonstrated to be adequate in winds up
to 20 kts. The Hughes 369 also has a reputation for being fully
controllable in much stronger crosswind and tailwind
conditions.
Wreckage and survivability information
Examination of the wreckage did not reveal any fault that might
have contributed to the accident. All flight control system damage
was typical of main rotor and drive train sudden stoppage. The main
rotor head assembly had suffered extensive damage, indicative of
main rotor blade contact with a solid object while the rotors were
being driven. The four main rotor blades and their grips were torn
off the rotor head at the strap pack as a result of the blades
impacting the pulley block, and the helicopter's subsequent contact
with the sea. Both tail rotor blades, the tail rotor gearbox, and
part of the tail rotor drive shaft had separated from the aircraft
when the aft portion of the tail boom fractured during the impact
sequence. Those items were lost at sea.
The engine-to-transmission drive shaft suffered an overload
fracture typically caused by sudden stoppage forces. Smearing of
the metal fracture surfaces on this drive shaft indicated that it
had continued to rotate after the fracture occurred. An in-depth
examination of the fuel system was not considered necessary, due to
the physical evidence that the engine was performing at a high
power setting when the main rotor strikes occurred.
The main damage to the fuselage occurred on the right side,
where the fuselage skin exhibited extensive lateral/inward crushing
deformation as a result of impact from one or more main rotor
blades, as well as from water impact. Both front seat pans were
crushed downward, consistent with the high g-loading experienced by
both occupants when the helicopter impacted the sea. Both forward
cabin doors separated from the aircraft. Most of the fibreglass
engine intake fairing was missing after the accident.
Both flight attitude indicators fitted to the helicopter had
recently been overhauled. Notwithstanding the extent of impact and
salt-water damage, no fault was found with the instruments.
The carrying capacity of the crane was 25 tonnes, with a maximum
outreach of 28 m. Marine surveyors subsequently advised that the
design of the cables and the pulley block counteracted any tendency
for the block to turn and twist the cables. Consequently, the block
face that was struck by the rotor blades, was probably facing out
to sea at the time of the accident.
The vertical face of the pulley block struck by the helicopter
was approximately 1.4 m high by 1 m wide. Contact between the main
rotor blades of the helicopter and the pulley block resulted in
several distinct impact marks on the face of the block. Four of the
marks displayed features that were consistent with contact by the
main rotor blade leading edge abrasion strips and threaded tip
weights. The sequence of the blade strikes could not be
established. However, the presence of the tip weight impact marks
on the block face indicated that the main rotor blades had not
contacted any solid object before hitting the block.
Multiple scratch marks were found on the opposite face of the
block to the main rotor blade strike marks. Those marks were
considered to have been a result of contact with the tail rotor,
the tail boom or the stabilisers.
No evidence was found of rotor strike marks on the hook, the
swivel, the chain, or the cables above the pulley block, nor were
any marks found on the upper or lower edges of the block, or on the
narrow vertical edges. However, the narrow vertical edge of the
block nearest the trailing end of the main rotor strike marks
showed evidence of white paint and fibreglass consistent with the
engine intake fairing contacting the block. Wreckage evidence
indicated that the main rotor blades probably dislodged the intake
fairing. Other fibreglass items attached to the airframe were
relatively undamaged and showed no evidence of contacting the
block.
The helicopter manufacturer reported that, "Once the first main
rotor blade struck the pulley block, all blades would have been
affected by the tremendous forces generated. The sudden stoppage
forces imparted and damage done to the main rotor system would have
resulted in severe main rotor imbalance and caused the blades to go
divergent in the lead/lag axis and possibly in the flapping and
feathering axis as well; in other words the blades would no longer
'fly' as you would expect normal rotor blades to. The drive train
and fuselage would also have been affected by these same forces.
Engineering and/or mathematical modelling of the accident scenario
then becomes a wild guess, as the performance and/or actions of the
fuselage, main rotor system (to include main rotor blades) and
drive train are no longer predictable."
The helicopter was fitted with utility floats. A life raft was
stowed in the rear passenger compartment. Both the helicopter pilot
and the marine pilot wore life vests. Both occupants also wore full
harness seat restraints and remained strapped in their seats during
the accident sequence. Examination of the wreckage indicated that a
main rotor blade had penetrated the cabin area on the right side of
the aircraft, fatally injuring the passenger. The pilot was able to
escape unaided from the helicopter after the accident.
Other information
Police spoke to the ship's captain by telephone two hours after
the accident. The captain reported that the helicopter was almost
out of the confines of the ship when it started turning left and
the main rotors then struck the crane hook which was hanging in the
air.
The ship's crew subsequently reported that the crane operator
had turned the jib to the left side of the ship and raised both the
jib and the hook before vacating the crane tower and standing on
the deck for the landing and takeoff of the helicopter. They said
that the helicopter initially rose into a hover about 1 m above
deck level, where it paused briefly before accelerating across the
deck, climbing and turning left at the same time. They reported
seeing the helicopter then collide with the pulley block and begin
to rotate, before the tail rotor also struck the block. The
helicopter then fell into the sea. Shortly thereafter, crewmembers
saw the helicopter floating inverted about 15 m from the left side
of the ship.
The company operations manual (page D8.10) stated:
"During each takeoff, when established in the hover
over the deck, a check should be made of power available, centre of
gravity and temperatures and pressures before moving clear of the
landing area.At night a climb to 500 ft is to be completed before any
substantial turns are made. All turns are to be made at the
standard rate. Steep turns are not to be carried out".
CAO part 95, section 95.7.3: Exemption of Certain Helicopters
from Compliance with Provisions of Sub-regulation 174B (2) of the
Civil Aviation Regulations provides for special requirements for
helicopters engaged in charter operations at night for the purpose
of marine pilot transfers to/from ships. No evidence was found that
the operator or the pilot had not complied with the requirements of
CAO 95.7.3.