- The left wing fuel tank filler caps were not secured before
takeoff. - Fuel vented from the left wing fuel tanks and had the
appearance of smoke coming from the left engine. - The pilot(s) did not take the appropriate actions to maintain
aircraft performance after shutting down the left engine. - The pilot(s) were unable to maintain control of the
aircraft.
The aircraft took off with the fuel caps for the left wing tanks
not secured, and the flap covers unlocked. It could not be
established if the flap covers remained in the opened (up) position
where they were left by the refueller, or whether they moved to the
closed/not locked position because of aircraft movement or
vibration, or airflow.
There may have been some perceived time pressure regarding the
pre-flight inspection because of the deteriorating light. Further,
the light may have reduced the visual prominence of the open flap
covers. Either, or both of those influences could have contributed
to the pilots not being aware that the left wing fuel caps were not
secured.
As the aircraft accelerated during the takeoff roll, the caps
fell from the left wing filler ports, probably as a result of
vibration and/or aerodynamic forces. The 'smoke' observed by the
tower controller and a witness was fuel venting from the open tank
filler ports. It was unlikely that any other interpretation of the
venting fuel would reasonably have been made in the circumstances,
particularly in the deteriorating ambient light conditions, coupled
with the position of the filler ports on either side of the engine
nacelle.
Other than the tower controller's transmission regarding the
'smoke', it could not be determined what other information the
pilots of the aircraft used in reaching the decisions to shut down
the left engine and attempt a left turnback. However, based on the
examination of the left engine and propeller, there would most
probably have been no indication from the cockpit instruments that
the left engine was malfunctioning in any way. Whether the pilots
were able to observe the 'smoke', or became aware of the situation
regarding the fuel caps, could not be determined.
It was apparent from the record of communications with the
control tower that the pilot who initiated communications with the
air traffic controller prior to take off was not the same person
who communicated with the tower controller following the advice
that there was 'smoke' coming from the left engine. However, which
pilot manipulated the aircraft controls during that period could
not be determined.
At the time the aircraft passed abeam the control tower, there
was adequate runway and overrun distance available for the aircraft
to land and decelerate significantly before reaching the boundary
fence. Whether the pilots considered the option of landing straight
ahead after being notified of the 'smoke' could not be
determined.
The flight path taken by the aircraft (the turn away from the
live engine) and the aircraft configuration at impact (left
propeller not feathered, landing gear extended) indicated that
aspects critical to maintaining single engine performance were not
accomplished. The final flight path and impact attitude of the
aircraft were typical of what might be expected following loss of
control when the airspeed falls below the minimum single engine
control speed.
Sequence of events
The co-owners of the Piper Twin Comanche aircraft, both of whom
were pilots, were conducting the flight to test a newly fitted left
propeller governor.
At about 1650 EST, one of the owners telephoned the aircraft
refueller and requested fuel for VH-CNZ. When the refueller arrived
at the aircraft a short time later, he was requested by the other
pilot to refuel the aircraft to full tanks. The refueller reported
that this pilot appeared to be conducting a preflight check of the
aircraft while the other pilot was seated in the cockpit, possibly
in the left seat. The refueller noticed that the fuel filler flap
covers were open and that the fuel tank filler caps, two on each
wing, one on either side of the engine nacelles, had each been
removed and placed on the wing adjacent to the filler points. After
adding fuel to the right auxiliary fuel tank, the refueller placed
the cap in the filler port. The pilot who was doing the external
inspection approached him and said that he would secure the caps
because they had a locking mechanism that was different from those
fitted to many other aircraft types. The refueller then filled the
right main tank and placed the cap in the filler port. As he moved
away, he saw the pilot move to the tank. The refueller then moved
to the left side of the aircraft and filled the left auxiliary and
left main tanks, again placing the caps in the filler port of each
tank. He did not secure the caps and left the flap covers open. At
this stage, he saw the pilot lying beneath the fuselage, apparently
conducting a fuel drain check. The refueller recorded in the
refuelling register that 179 litres of fuel had been added to the
aircraft at 1700. He then told the pilot seated in the aircraft the
amount of fuel he had added, and reminded her that he had not
secured the fuel caps. The refueller then moved to refuel another
aircraft.
A short time later, the aircraft taxied for takeoff. Visual
meteorological conditions existed with scattered light cloud at
3500 feet. The wind was from the southeast, gusting to 5 knots.
Sunset on the day of the accident was at 1658. At the time of the
accident, the sun was 3.5 degrees below the horizon, bearing 292
degrees True.
The following is a summary of the pertinent communications
between the aircraft (CNZ) and Archerfield Tower (Tower), which
commenced at 1714.14.
- 1714.14 (CNZ) Archer Tower Twin Comanche Charlie November Zulu
is ready runway 10 right departing to the southeast (male
voice). - 1714.26 (Tower) Charlie November Zulu Tower runway right
cleared for takeoff. - 1714.31 (CNZ) Runway right cleared for takeoff Charlie November
Zulu (male voice) - 1715.21 (Tower) Charlie November Zulu there is smoke coming
from one of your engines (pause) it's the left engine. - 1715.31 (Tower) Charlie November Zulu did you copy.
- 1715.36 (CNZ) Charlie November Zulu affirm we're shutting it
down and request a left turn back for landing (female voice). - 1715.43 (Tower) Charlie November Zulu left turn approved.
- 1715.45 (CNZ) Charlie November Zulu (female voice).
- 1716.23 (Tower) Charlie November Zulu clear to land.
- 1716.27 (CNZ) Clear to land Charlie November Zulu (female
voice).
Several witnesses observed the progress of the aircraft. Their
observations confirmed that a cloud of what appeared to be 'greyish
black smoke' coming from both sides of the left engine. The
aircraft yawed sharply left and right just after becoming airborne
and then commenced a left circuit at very low level, estimated to
have been 100 ft above ground level. The landing gear remained
extended throughout the circuit. Approaching the western boundary
of the airport, the aircraft entered another left turn, passing low
over some buildings. Part way through the turn, the aircraft's
angle of bank suddenly increased and it descended rapidly into the
ground. Both occupants were fatally injured.
Wreckage and impact information
Initial examination at the accident site revealed that the fuel
filler flap covers of the two left wing tanks were open, and both
filler caps were missing. The caps were recovered the following day
from runway 10 right and the adjoining clear way. Fuel wetting was
evident on the ground below the open fuel caps of the inverted left
wing. A total of approximately 35 litres of fuel was recovered from
the damaged right wing fuel tanks. The recovered fuel was confirmed
as the correct type and grade for the aircraft. The accident
aircraft was the thirteenth of sixteen refuelled from the same
batch and tanker on the day. The records show that the fuelling
agent had sample tested the fuel on three previous occasions
throughout the day. Given that there were no reports of fuel
related problems from any other aircraft and because of the obvious
level of performance from the right engine. The quality of the fuel
as a factor in the development of the accident was discounted.
The aircraft wreckage was located in an open area adjacent to
the western boundary fence of the aerodrome, approximately 250
metres north-northwest of the threshold of runway 10 left. Impact
marks indicated that the aircraft was inverted and rolling left
when it struck the ground. The aircraft attitude was 55 - 60
degrees nose down and 25 - 30 degrees left wing low. The main
wreckage came to rest about 17 m beyond the initial impact point.
The tail section was right way up and the main wing section was
folded back on top of the rear fuselage. The cabin area was
severely distorted, with the instrument panel and cockpit floor
displaced rearward.
Specific points noted during the wreckage examination included
the following:
- There was no evidence of either pre-impact or post impact fire
including to the left engine. (PA30-160 aircraft, along with most
other light twin engine aircraft, were not equipped with fire
detection or suppressant systems.) - The landing gear was locked in the extended position and the
wing flaps were fully retracted. Impact damage prevented the
serviceability of the stall warning system being assessed. - The nature and extent of damage to the cockpit engine control
pedestal prevented any useful witness mark information being
obtained regarding the pre-impact position of the controls. - Ground contact marks and the condition of the right propeller
blades indicated that the right engine was developing significant
power at impact. Ground contact marks and the condition of the left
propeller blades indicated that the left propeller was rotating at
impact but that the engine was not developing power.
The constant speed governor from the left engine was recovered;
the only obvious damage being slight bending to the control-input
shaft which was consistent with impact damage. The governor was
functionally tested at an approved overhaul facility. The tests met
all the manufacturer's specifications, with the exception of the
maximum RPM setting that indicated 2285. This was 45 RPM below the
specification. Specialist opinion was that this discrepancy could
be attributed to the damage to the control-input shaft.
Disassembly of the left and right propellers found no evidence
of any pre-existing fault or defect. Disassembly of the left
propeller confirmed the blades were at fine pitch and not in the
feathered position at impact. Disassembly of both engines did not
reveal any pre-existing fault or defect that would have affected
normal engine operation.
Fuel tank filler points
The two fuel tank filler points on each wing were located on
either side of the engine nacelles. The filler points consisted of
filler port, a cap to seal the port, and a flap covering the cap
access. The cap consisted of a black rubber insert that compressed
to seal the fuel filler tank port by the action of a screw grip on
top of the cap. The flap cover was secured with a winged slotted
'dzus' type fastener and, when locked, was flush with the upper
surface of the wing. Locking the flap cover required deliberate
action, and could not be achieved by slamming the cover down. The
flap covers were hinged parallel to the longitudinal axis of the
aircraft, and opened away from the engine nacelles. The slotted
'dzus' fasteners had to be locked for the flap covers to be closed
flush with the wing surface. If not locked, the flap covers would
stand slightly proud of the wing surface.
The left and right wing filler points, inboard of the engine
nacelles, were visible from the left and right cockpit seats,
respectively. They may have been visible in the pilot's peripheral
vision, depending on the pilot's seating position. With the flap
covers open, there was a high level of contrast between the white
painted upper surface of the wing and the dark underside of the
flap covers and filler cavity. In reduced light conditions, the
level of contrast would have been lower.
When in the open position, the outboard flap covers were partly
visible from the cockpit. If those covers were down, but not
locked, they were not visible from the cockpit.
The 'dzus' fastener locking mechanism for the flap covers on the
left wing tanks functioned normally. Aside from damage caused to
one cap when it was struck by an aerodrome mower operating on the
runway 10R flight strip on the morning following the accident, both
fuel caps from the left wing tanks were in a serviceable
condition.
The pilots
Both pilots were appropriately licensed and held current medical
certificates.
Toxicological and Post-mortem analysis did not reveal the
presence of any compound or pre-existing medical condition that may
have affected the performance of either pilot.
Aerodrome information
Runway 10 Right was 1100 m long. Beyond the runway end was a
flat area extending for more than 400 m, and free of major
obstacles, to the aerodrome boundary fence. The distance from a
position on the runway abeam the control tower to the boundary
fence was about 800 m.
The control tower cab was 65 ft above ground level. The
controller reported that when the aircraft passed abeam the tower,
its level appeared to be slightly below that of the tower cab. With
respect to the control tower, the remaining light or glow from the
sun was behind and slightly left of the position of the aircraft,
as it became airborne.
Aircraft performance
The aircraft flight manual performance charts indicated that, in
the prevailing conditions, the take-off ground run distance
required was about 350 m, depending on the flap setting used. The
observations of the tower controller indicated that the actual
take-off performance of the aircraft was not substantially
different from that figure.
The landing distance over a 50-ft obstacle was approximately 500
m, depending on the aircraft flap setting and approach speed.
Single engine performance
The sea level single engine climb performance of light twin
engine aeroplanes certified in accordance with United States
Federal Aviation Regulation 23 requirements can be up to 70 to 90
percent less than the twin engine performance. Many factors can
contribute to this performance loss such as aircraft age and
condition, leaving the landing gear extended, not feathering a
propeller, not maintaining the correct airspeed, and not turning
towards the live engine.
The Pilot's Operating Manual for the aircraft included
information on propeller feathering procedures and single engine
flight. That information included the statement that, when climbing
with one engine inoperative, the landing gear and wing flaps must
be retracted.