- The pilot's fuel planning was based on incorrect fuel content
and weight considerations. - The pilot did not include the Sydney Harbour scenic flight in
his flight planning. - The pilot diverted from the recommended in-flight fuel
management practices.
The aircraft had been assessed as having 280 L of fuel on board
prior to departure from Canberra, based upon the delivery pilot's
calculation. ATSB calculations, using the operator's own fuel
planning figures, indicated that the amount of fuel consumed during
the 1.8 hour delivery flight from Tamworth would likely have
equated to a fuel remaining figure of approximately 265 L. In
addition, no allowance was able to be determined for the amount of
fuel consumed during the engine ground runs at Tamworth, between
the time of the last recorded refuel and the delivery flight.
Accordingly, the actual fuel tank contents on departure from
Tamworth for the delivery flight could not be accurately determined
and would probably have been an amount less than the maximum
useable.
While planning for the accident flight utilising a
computer-based application, the pilot used an incorrect figure (465
L) with respect to total versus useable fuel tank contents (454 L).
That led the pilot to include 11 L of fuel, which was unavailable
for engine consumption. In addition, he omitted to plan an
allowance for fuel consumption during the approximately 12 minute
Sydney Harbour scenic flight. Using the operator's fuel consumption
planning figure, this may have involved consumption of up to 20 L
of additional fuel.
The pilot's use of the computer-based flight planning
application included calculations for aircraft weight and balance.
His utilisation of the full fuel planning figure in these
calculations, instead of the assessed fuel load figure of 280 L,
may have led to an erroneous perception that he would be overweight
following embarkation of the five passengers at Bankstown, if he
added fuel prior to takeoff from either Bankstown or Canberra. Had
the pilot used the assessed fuel tank content figure, he would have
realised that he could have added fuel and remained within aircraft
weight limitations.
The manufacturer's fuel usage figures are determined using a
recommended technique for leaning of the fuel mixture supplied to
the engines. During the accident flight, the pilot deviated from
the recommended technique. That deviation would likely have
increased the engine fuel consumption.
Technical investigation of the right engine indicated that it
was capable of normal operation. Examination of the left engine
indicated that it should still have supplied at least partial power
in flight. The failure mode of the exhaust valve rocker stud and
the bending of the inlet valve pushrod were examined in
consultation with a representative of the engine manufacturer and
engine overhaul specialists. Although an exact reason for the
failure could not be determined, it is possible that the damage may
have occurred following the loosening of one or both of the rocker
pivot retaining nuts. As the nut(s) loosened during engine
operation, the exhaust valve rocker would have lifted, preventing
the exhaust valve from opening. During the valve overlap stage of
the engine operating cycle, prior to the start of the induction
stroke, the ignited and expanding combustion gasses may have been
unable to escape through a now closed exhaust valve. That scenario
would have greatly increased internal cylinder pressure which could
have prevented the inlet valve opening and, consequently, resulted
in the bending of the inlet valve push rod as it tried to move the
valve. The damage to the inlet valve pushrod was also considered to
have been consistent with the rotation of the engine with a
"hydraulic lock" situation existing in the cylinder. Such a
condition may occur in the cylinder if the engine was overprimed
prior to an engine start.
It is likely that the engine failures occurred as a result of
fuel exhaustion.
The Piper PA34 Seneca III, took off from Canberra for Bankstown
under the Visual Flight Rules (VFR). The pilot in command had
planned to embark five passengers at Bankstown then to conduct a
scenic flight around Sydney Harbour, proceed to Cessnock for lunch
and return to Bankstown where he intended to disembark the
passengers before returning to Canberra.
The flight to Bankstown was uneventful. On departure from
Bankstown, the pilot proceeded southeast to the coast and then
north, at low level, along the VFR coastal route to Manly. A delay
was experienced at Manly, prior to turning south and entering
Sydney Harbour. The Sydney Harbour scenic flight was then
conducted, completing a circuit of the Harbour Bridge to
Rushcutter's Bay loop. The pilot then returned to South Head and
proceeded north via Aeropelican for a landing at Cessnock.
During the return flight, the pilot deviated west of the planned
track in order to avoid severe weather that had been indicated on
the aircraft's weather radar. Shortly after passing Brooklyn
Bridge, which was the start point for the northern inbound VFR
track to Bankstown, at an altitude of 2,500 ft, the pilot reported
that the left engine suddenly stopped. The pilot reported that he
then carried out the engine failure checks from memory, feathering
the propeller. Approximately one minute later, the right engine
began to gradually lose power, before stopping after approximately
a further 20 seconds. The pilot reported that he then pushed all of
the engine and propeller controls forward and attempted to restart
the engines. That action resulted in the inadvertent unfeathering
of the left propeller due to operation of the unfeathering
accumulator.
The pilot conducted a forced landing into a treed area beside a
main road. The aircraft struck the trees, rotated to the right and
impacted the ground left wing forward. Four of the six occupants
sustained serious injuries and the aircraft was destroyed.
Pilot information
The pilot was appropriately licensed for the flight and had
accumulated a total of 270 hours flying experience with 14 hours on
the aircraft type.
Flight and fuel planning
The aircraft arrived on the operator's flight line five days
before the accident, after delivery from Tamworth. The technical
log indicated that the last recorded refuel had been conducted at
Tamworth on 13 March 2000. Between that time and the delivery
flight to Canberra the aircraft had undergone a 15-minute dual
engine run following a propeller change. The engine run included a
period of one to one and a half minutes with both engines at full
power. Prior to departure from Tamworth, the delivery pilot
reported that he visually assessed the fuel tanks as full. Upon
arrival at Canberra, the fuel tank content was assessed as 280 L,
using flight time and fuel usage calculations.
The pilot planned the accident flight utilising a computer-based
flight planning application. He did not plan for any aerial work at
Sydney Harbour, despite having an intention to conduct a scenic
flight in that location. Air Traffic Services (ATS) radar data
indicated that the scenic flight duration was approximately 12
minutes. In addition, he planned the flight using figures for full
fuel tanks, however he used the total fuel tank content figure of
465 L instead of the useable fuel tank content figure of 454 L.
Further, he was aware that the aircraft had only an assessed 280 L
of fuel on board and considered that that amount was sufficient for
the flight from Canberra to Cessnock and for the return flight to
Bankstown. He had decided not to add fuel prior to departure from
Canberra due to a perception that the aircraft would be over
Maximum Takeoff Weight at Bankstown or Maximum Landing Weight at
Cessnock, after the addition of the five passengers.
Fuel management
The pilot reported that he visually checked the fuel tank
contents at Canberra before departure, with fuel just visible
through the fuel cap opening. That quantity was then cross-checked
with the aircraft fuel gauges and it appeared to agree with the
previously calculated total. An attempt was also made to check the
fuel tank contents using the aircraft's fuel dipstick, however,
that was unsuccessful as the fuel level was well below the lowest
graduated scale on the stick. The pilot reported that he again
checked the fuel level on arrival at Bankstown. At that time the
level was out of sight of the fuel caps, however, the total fuel
remaining on the fuel gauges appeared to agree with his assessment.
Prior to landing at Cessnock the fuel gauges were again checked,
with the pilot considering that the indicated fuel level was what
he expected from his mental calculations to allow for the return
flight to Bankstown.
ATS radar data indicated a total flight time of 159 minutes from
takeoff at Canberra to the accident site. That figure did not
include any allowance for ground taxi at Canberra, Bankstown and
Cessnock. Using the operator's recommended fuel usage planning
figure of 100 L per hour, 159 minutes flight time would have
consumed 265 L of fuel.
The aircraft manufacturer's recommended engine fuel leaning
procedure for cruise flight was detailed in Section 4 (Normal
Procedures) of the Pilot's Operating Handbook, which stated:
"For 45, 55 and 65% power the mixture should be leaned to 25
[degrees] F rich of peak E.G.T. [Exhaust Gas Temperature] but not
to exceed 1,650 [degrees] F E.G.T.", and "For maximum engine
service life, cylinder head temperatures should be maintained below
420 [degrees] F..."
The pilot reported that he had been taught to lean the fuel
mixture to the top of the green arc on the exhaust gas temperature
gauge. The green arc on the gauge extended from 1,200 to 1,525
degrees F. He reported that during the accident flight he leaned
the mixture according to that method, however he had subsequently
enriched the mixture one or two graduations below the top of the
green arc. Advice from the aircraft manufacturer and other Seneca
III operators, indicated that that action may have increased the
fuel flow by up to approximately 10 L per hour.
Approximately one litre of fuel was recovered from the aircraft
wing tanks, however the fuel tanks had been substantially damaged
during the impact sequence. There was no evidence of fuel leakage
on the ground. Inspection of the fuel system components revealed no
evidence of fuel contamination. The left engine fuel selector
control was positioned at the OFF position and the right engine
selector was positioned at ON.
Engine and fuel system information
Both engines had recently been overhauled and had flown 57.3
hours since fitment to the aircraft.
During the flight, a short time after passing Aeropelican, the
pilot reported that the left engine had required increased throttle
to maintain the selected manifold pressure. While taxying after
landing at Cessnock the left engine appeared to idle slower than
before and the alternator light flickered on and off. The light had
extinguished when the pilot increased engine RPM. After vacating
the aircraft, the pilot noticed evidence of an oil leak along the
outboard side of the left engine cowling, on the underside of the
left wing and on the left flap. A check of the left engine oil
quantity revealed that the engine had used about half a quart
during the flight. Confirmation with the operator by telephone
indicated that the oil level was within tolerances. The source of
the oil leak was not able to be located. The pilot reported that
operation of both engines from departure at Cessnock to the point
of engine failure appeared normal.
Technical investigation at the accident site revealed that the
left engine number-4 cylinder exhaust rocker pivot was loose and
that the rocker had contacted and holed the inside surface of the
rocker cover. The forward rocker pivot-retaining stud had sheared
flush with the surface of the head with evidence of a fatigue
failure on the stud fracture surface. The number-4 cylinder inlet
valve push rod had also failed close to the outboard tip of the
rod. Detailed technical examination of both engines at an engine
overhaul facility noted that the exhaust valve on the number-4
cylinder of the left engine remained closed during rotation of the
crankshaft and the inlet valve on the same cylinder only opened a
small amount. Both engines were then test run in an engine test
cell. The test run of the right engine revealed no condition that
would have contributed to the in-flight loss of power. The test run
of the left engine indicated that it was capable of operation,
however it's performance was affected by the damage evident on the
number-4 cylinder's valve mechanism.