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.

FMI: www.atsb.gov.au