Four Lost On Way Home From Fishing Trip
The Australian
Transportation Safety Bureau has issued its final report on the
November 8th, 2003 crash of a Robinson R-44 carrying four men on
their way back from a fishing trip in Kununurra. The aircraft,
headed for Cape Dommett, went down in a stand of trees about
17-minutes after take-off.
Here are some excerpts from the ATSB report:
On 8 Nov 2003, a Robinson Helicopter Company R44 (R44),
registered VH-YKL, and a Bell Helicopter Company 206 (B206),
registered VH-FHY, were conducting fishing charter flights from
Kununurra to the Cape Dommett area of northern WA. The flights were
conducted under the visual flight rules (VFR) and were both
single-pilot operations.
The R44 had four persons on board (POB) and the B206 had five
POB.
After the passengers had spent the morning fishing, it was
decided between them that several would change seating arrangements
between the helicopters for the return journey. At about 1027
western standard time, after the passengers assumed their new
seating arrangements, the helicopters took off and flew in company
at 500 feet above ground level (AGL), for the return flight to
Kununurra.
Approximately 17 minutes later, the pilot of the lead
helicopter, the B206, received a radio broadcast from the pilot of
the R44 (file photo of type, below) stating that "I am going in
hard" The pilot of the B206 immediately banked his helicopter
around in a tight right turn and, after assuming a reciprocal
heading, observed a mushroom cloud of smoke rising from a nearby
ridge. The pilot of the B206 broadcast a MAYDAY to air traffic
services (ATS) and began to orbit the accident site. The pilot of
the B206 was asked by ATS to look for people moving around the
wreckage; none could be seen.
With no signs of life visible, and unable to identify a safe
place to land, the pilot of the B206 made an operational decision
to continue to Kununurra. The first rescue team to arrive at the
site confirmed that all four occupants had received fatal
injuries.
ATSB Analysis
The pilot had undergone training by an approved organization on
the helicopter type and was well regarded by his CFI. During the
course of that training, he had also conducted a number of practice
autorotations, and had successfully executed power-on recoveries to
the flare. The pilot in command also met the operator’s
minimum flying experience requirements listed in the operations
manual to conduct the occurrence charter flight.
The absence of passenger information on the flight note
indicated that an accurate calculation of MTOW was probably not
conducted, and the pilot was probably not aware of the
helicopter’s actual take-off weight and center-of-gravity
position. The occurrence pilot had been trained by the CFI to
habitually include the nature of any emergency in his radio
transmission if it had been identified. These identifiable
failures would prompt calls of "engine failure," "drive belt
failure" or "tail rotor drive failure" as part of the emergency
radio transmission. The occurrence pilot did not identify the
nature of the emergency in his brief radio transmission.
Due to the destruction of the engine the investigation was
unable to determine the amount of power being produced by the
engine immediately prior to impact. The investigation team examined
a number of reasons for the helicopter diverging from the planned
flight path track.
While prevailing weather conditions were unlikely to have
contributed to the occurrence, the effect of an upset due to
turbulence leading to large control inputs by the pilot and a
possible low-G maneuver could not be ruled out. The physical
evidence that would point to this type of event would be damage to
the blade flapping restraint components. In extreme examples of
this phenomenon, the main rotor mast may exhibit damage from
contact by the main rotor head as it reached a teetering and or
flapping limit. Also separation of the main rotor mast and severing
of the tail boom structure are not uncommon in such situations and
would have been evidence of a possible low-G occurrence.
The main rotor mast of the R44 was examined and no evidence that
might be attributed to low-G maneuver, to the extent that mast
bumping had occurred, was observed. The blade droop stops,
up-coning stops and tusks were also examined and found to exhibit
contact marks consistent with the normal range of rotor blade
movement. The marks consisted of minor surface scraping. The
investigation was unable to determine when the marks occurred.
The damage to the tail boom, evident at the accident site, was
considered to be as a result of a main rotor blade contacting it
after the first main rotor blade tree strike during the break up
sequence.
Given the similarity of distance covered, and the flight time
after the divergence from track when compared with the published
figures, it was also possible that the R44 was established in
autorotational flight, and that the pilot initiated a right turn to
a selected forced landing site.
The metallurgical evidence indicated high energy in the rotor
system. This could indicate that the pilot may have been
terminating the flight in a forced landing autorotative maneuver,
or may have been in the midst of a recovery maneuver such as that
required for a low-G event recovery.
If the pilot had been executing an autorotation, the high gross
weight of the helicopter would have assisted him in maintaining
optimum rotor RPM, if the autorotation procedures recommended by
the helicopter manufacturer had been followed. However, the pilot
would have had to use an amount of aft cyclic input to the flight
controls to counteract the effects of the forward center of
gravity.
If he had been attempting an autorotative landing, the forward
center of gravity may have compounded the already aft cyclic
position and adversely affected his ability to flare the helicopter
to the extent required to arrest the descent and reduce forward
groundspeed. This may have resulted in a heavier than intended
landing and a higher than intended groundspeed and may have been
the reason for the pilot’s broadcast that he was going in
hard. It was unlikely that the pilot had previously conducted an
autorotation at MTOW and/or with a forward center of gravity in the
occurrence helicopter type.
The helicopter was most likely under the control of the pilot
until the moment it contacted the trees at approximately 36 feet
AGL with a groundspeed of about 48 knots. From that point, the
helicopter departed from controlled flight due to the damage to the
main rotor system caused by impact with the trees. Given that the
short radio transmission by the pilot of the R44 did not allude to
a specific problem, and in the absence of witness reports of the
occurrence, and the lack of physical evidence due to post-impact
fire, the reason(s) for the descent from cruise altitude, and the
subsequent impact with terrain could not be established.
Conclusions
1. The R44 departed
cruise flight in a descending right turn approximately 17 minutes
after take off from the Cape Dommett area.
2. The R44 first contacted trees at a height of 36 ft AGL.
3. The R44 was approximately 27 kg over the MTOW for the
helicopter type at impact.
4. The R44 center of gravity was outside the forward limit for
the helicopter type at impact.
5. The accident was not survivable.