Collision with terrain

While conducting spraying operations, the aircraft hit a single wire earth return (SWER) power line. The power line contacted the propeller and proceeded to wrap about the propeller hub. The power line was pulled taut by the aircraft, the pilot lost control, and the aircraft impacted the ground 1,000 metres beyond the point of wire contact. The lateness of the day combined with low overcast is believed to have contributed to the pilot's inability to detect the wire in his flightpath.

During the impact sequence, the underfloor framework with the attachment points for the seat and seat belt appear to have distorted altering their geometry. This in turn may have allowed sufficient movement of the pilot against the loosened restraints for his head to contact with the instrument panel. As he was wearing a helmet at the time, the sequence resulted in severe concussion and not a more serious head trauma.

The wind at the time was reported to be from the south-east at 15 to 20 kt with gusts to 25 kts. The pilot had flown away from a mob of cattle at 50 kts in a south-westerly direction across the wind, to check on some other animals. He then reduced speed and turned left into wind at a height of about 15 ft above ground level. As he was rolling out of the turn, the helicopter sank to the ground. The helicopter cartwheeled forward and came to rest inverted. The aircraft was within weight and balance limits for the flight and was reported to have been operating normally before the accident. The pilot reported having flown 6.4 hours that day.

The flight was part of a private holiday tour with four adults and two children in the aircraft. The pilot was conducting an approach to land at a property airstrip. There was a headwind of about 20 kts on final approach and he was maintaining an airspeed of 80 kts. When the aircraft descended below the tree line just before landing it entered an area of windshear. The pilot noted an increase in speed at this time and said that the aircraft bounced a number of times after the initial touchdown.

He then elected to go around, applied full engine power, and retracted the flaps from 30 to 20 degrees. He then became concerned about clearing trees to the left of the strip as the aircraft had veered left during the go-around. The aircraft subsequently collided with the trees and impacted the ground heavily. The pilot and one passenger sustained minor injuries. There was no reported problem with the engine or the aircraft during the go-around. Post-accident examination of the aircraft indicated that, at impact, the flaps were in the process of retracting, and the landing gear was down.

FACTUAL INFORMATION

At 0450 WST, the Bell 206 helicopter departed the heliport on East Intercourse Island to conduct a marine pilot transfer to a ship waiting at the outer buoy in Dampier Sound. The pilot reported that although there was a high overcast, which mostly obscured the moon and made the sky very dark, the horizon was visible. The towns of Dampier and Karratha were to the south-east of the ship. The wind was calm and the sea surface almost mirror-like. The pilot reported that the horizon was clearly discernible during the transit to the ship. The moon set at 0452 and sunrise was at 0633. The helicopter landed on the ship at about 0505 and disembarked the marine pilot. At about 0514, the helicopter departed towards the north-east. The pilot reported that as the helicopter climbed through 500 ft, the tail rotor pedals felt unusual. Whilst he was attempting to determine the nature of the tail rotor pedal problem, he did not monitor the helicopter's flight attitude and performance, and the helicopter descended into the sea. A deck hand on the ship reported to the ship's bridge staff at about 0515 that he saw the helicopter's lights enter the water off the ship's port side. At approximately 0615, a port authority vessel recovered the uninjured pilot. The helicopter sank in about 18 m of water in the main shipping channel to Karratha.

An inspection of the recovered wreckage did not reveal the cause of the reported fault in the tail rotor control system. The pilot reported that although the pedals had felt unusual, there had been no loss of directional control before the impact.

The helicopter was fitted with a radio altimeter that had a low height alert warning light. The pilot reported that the alert was set to activate at 150 ft but did not recall seeing the low light illuminate before the helicopter struck the water. The helicopter was not fitted with an autopilot or height hold facility. The operator reported that the collective of the helicopter had a tendency to fall if not closely controlled by the pilot.

The pilot had recorded approximately 4,200 hours flying experience on a variety of helicopters, including approximately 900 hours on the Bell 206. He had completed 20 hours on this helicopter in the 30 days immediately prior to the accident. The pilot had a valid night visual flight rules (night-VFR) rating and 51 hours night-VFR experience. However, he had accumulated only 5.5 hours instrument flying time and he did not have an instrument rating. The pilot commenced night marine pilot transfer training about 2 months prior to the accident, and had received 21 hours of night-VFR training that included more than 63 landings on ships at night. About half of these landings were to brightly lit decks. About 70 per cent of the landings had been conducted under dark-night conditions but his training did not include practice emergencies or distractions during night departures. He began carrying passengers less than 1 month prior to the accident.

The pilot had been working alternate days for 8 days prior to the accident. The longest shifts had been two of 8 hours duty time each.

Human performance levels vary through physiological cycles of approximately 24 hours. These are referred to as circadian rhythms. The most significant circadian low-point occurs between approximately 0200 and 0600. The effects of circadian dysrhythmia include poor judgement, increased reaction times, mental haziness or lethargy and a general decrement in psychomotor performance. On the day of the accident, the pilot had been awakened by a call from work at 0400 to pick up two marine pilots for a departure 1 hour later.

A constraint in human performance when operating at night is the eye's poor ability to quickly adjust from brightly lit areas, such as a ship's deck, to dark environments, such as over water. The human eye generally achieves a large amount of dark adaptation after 15 minutes with full adaptation occurring after about 40 minutes.

The Civil Aviation Regulations (CARs) permitted the operation of aircraft under night-VFR with certain provisions. Although the CARs restricted single-engine aircraft charter operations, the Civil Aviation Orders (CAOs) provided exemptions to these limitations for marine pilot operations. CAOs also required that operations that were conducted during visual meteorological conditions at night, do so in accordance with the helicopter's flight manual. Although the regulations and orders did not require a visual horizon when flying at night, there was no on-going requirement for a pilot to demonstrate an ability to fly an aircraft with sole reference to the aircraft's flight instruments.

The company operations manual required night-VFR flights to be flown such that flight attitude could be maintained by reference to external objects adequately illuminated by ground or celestial lighting. The helicopter's flight manual required that the pilot maintain orientation through visual reference to ground objects solely as a result of lights on the ground or adequate celestial illumination. Neither publication provided guidance or caution on the human factor limitations associated with night visual flying.

ANALYSIS

The pilot had a visual horizon during the transit to the ship and the lights of the town of Dampier would have provided a horizon to the south-east for the return transit. The ambient and ground lighting conditions would probably have been sufficient to meet the requirements of the company operations manual and the helicopter's flight manual, although it is unlikely that such conditions existed during the departure from the ship. The moon had set 13 minutes prior to the helicopter's arrival at the ship. The transit time to the ship would probably have been sufficient for the pilot to attain a large proportion of his visual dark adaptation and therefore he may have ascertained that there was an adequate horizon to the north-east. However, after landing on the ship, the pilot's dark adaptation would have been substantially destroyed by the ship's lights illuminating the deck area. Although the company operations manual and helicopter's flight manual required sufficient lighting to maintain flight attitude, neither publication provided guidance or caution on the human factor limitations associated with dark adaptation. Consequently, although the pilot thought he had an adequate horizon on which to maintain the helicopter's flight attitude, he had no objective measure with which he could ascertain the suitability of the conditions for continued flight in accordance with the company manuals.

The departure from the ship was unlikely to have been made with any discernible horizon because the moon had set 22 minutes before, the high overcast had obscured much of the celestial lighting and the pilot could not have achieved any dark adaptation in the brief period from the take-off to water impact. Deprived of an adequate external visual horizon, the pilot would have been unable to maintain the helicopter's attitude and departure profile without referring to the helicopter's flight instruments. Given his minimal instrument flying experience, the pilot may have had difficulty transitioning from visual reference to instruments during the departure. When the pilot became concerned at the "feel" of the tail rotor pedals, he diverted his attention from the helicopter's attitude and performance indications for an extended period. While the pilot was not monitoring the helicopter's flight attitude or performance, it is likely that the helicopter's collective control fell and the helicopter descended. Having been awakened at 0400, the pilot was working within the most pronounced low point of his circadian cycle which may have also adversley affected his ability to maintain his situational awareness during the distraction. His relative inexperience at conducting night marine transfers associated with possible circadian dysrhythmia may have reduced his situational awareness because he was unaware that the helicopter was descending until it struck the water.

SAFETY ACTION

The Bureau of Air Safety Investigation is currently investigating a perceived safety deficiency that has been identified as a result of this occurrence. The deficiency relates to:

- human factors involved with operating helicopters over water at night;

- passenger safety provisions for over-water helicopter operations; and

- the adequacy of current night-VFR requirements for over-water helicopter operations.

Any recommendation issued as a result of this investigation will be published in the Bureau's Quarterly Safety Deficiency Report.

Local safety action

The operator has increased the training requirements for pilots operating to ships under night VFR. These requirements include night training under moonless conditions and total cloud coverage, the introduction of basic instrument flying proficiency checking and the introduction of annual written human factors examinations.

The commercial pilot pre-arranged to private hire a Robinson R22 for business purposes. When he arrived at Mangalore to collect the helicopter he spoke to the duty instructor who advised him to take VH-KKG after it returned from a training flight. Minutes later a solo student pilot landed KKG well away from the AVGAS refuelling facility because the flying school forbade student pilots to hover or land near the fuel bowsers. The student then applied the control frictions and reduced power, expecting to stop the engine after its cool down period. The commercial pilot planned to depart Mangalore with full fuel.

He proceeded to the right door of KKG where he tried to explain to the student that he wanted to swap seats with him without the engine being shut down, in order to hover-taxi to the bowser for fuel. The student, a Japanese national undergoing basic flying training in Australia, did not understand the request mostly because of the over-riding engine noise and because he was wearing a headset. He remained at the controls with the engine running. As the commercial pilot intended to reposition the helicopter only a short distance before shutting down the engine to refuel, he proceeded to the left side of the helicopter and occupied the left seat where there were dual flight controls.

He explained his intentions to the student who handed over the controls. The commercial pilot then checked that both his and the student's seat belts were fastened before releasing the control frictions. He then increased the engine/rotor RPM to the top of the green and raised the collective lever with the intention of stabilising in the hover momentarily before hover-taxiing to the bowser. He reported that as the helicopter became light on the skids, he applied light pressure to the anti-torque pedals and made minor cyclic control inputs as he further raised the collective.

As the landing gear skids left the ground the helicopter yawed quickly to the left. He cannot recall exactly what his following control inputs were as things happened very quickly and violently. However, his impressions were of yawing quickly and an unusual attitude which he attempted to correct. Then the helicopter skids contacted the ground and it lifted back into the air momentarily before settling onto the ground and rolling onto its left side. The weather was reported to be fine with a light and variable wind, CAVOK and temperature about 25 deg Celsius. The weather was not a factor in the accident.

No fault has been subsequently found with the helicopter which may have contributed to the accident. It had been functioning normally on its previous flight. The student reported that he made no flight control input after handing over the controls to the private pilot. The commercial pilot recalled that the student grabbed the cyclic at the end of the accident sequence but this action did not influence the outcome of the accident. The instructor did not give the commercial pilot approval for a engine-running seat swap with the student, nor did he authorise him to fly from the left seat.

Prior to the accident, the instructor had been very busy escorting a group of cadets who had arrived at the airport earlier than expected to visit the flying school. Except for dual check and training flights, the helicopter manufacturer requires that the R22 be flown from the right seat. There is a different visual perspective flying from the left seat versus the right seat. The R22 is also equipped with the RPM governor on the right throttle only. Normally only check and training pilots are given the additional dual instruction to enable them to fly from the left seat with another pilot occupying the right seat.

Commonly, when a pilot first attempts to hover a helicopter from the opposite seat, some degree of over-controlling will occur. The commercial pilot reported that he had previously controlled an R22 in flight from the left seat with a pilot-in-command occupying the right seat, but he had never before lifted a helicopter into the hover while flying from the non command seat. It is probable that the commercial pilot began to over-control the helicopter as it lifted into the hover. He was experienced at flying without a governor controlling RPM, so manipulating the left throttle was probably not a factor in the accident.

The yaw to the left probably resulted from inadvertent excessive left pedal input because a loss of anti-torque or insufficient left pedal would have caused the helicopter to yaw to the right. Over-controlling probably developed into an irretrievable roll-over condition as the left skid dragged on the ground as the helicopter yawed left.

The pilot in command was demonstrating a 15-degree banked turn at a height of about 700 ft. The aircraft was travelling at 70 kts with 15 degrees of flap extended. However, control of the aircraft was affected by an unseen dust devil which caused it to roll further left to about 90 degrees angle of bank. The pilot applied full right rudder and aileron controls, righting the aircraft just above treetops in a stalled attitude, but was unable to arrest the descent. The aircraft struck trees and came to rest on the ground in an inverted position. Both the pilot and passenger vacated the aircraft, which was subsequently destroyed by an ensuing fire.

The foreign Private Pilot was conducting a local flight in the Camden area, following a flight review three days earlier.

At the time of departure, the control tower was manned. Throughout the day the wind had been from the south-west, favouring runway 24. By the time aircraft returned for a landing the tower had closed down. The Camden ATIS, which had earlier nominated runway 24 for landing, had been changed on closedown to provide a standard message. This indicated that the control zone was reclassified as Class G airspace, and that Mandatory Broadcast Zone procedures applied. The preferred runway direction was 06. No wind information was provided.

The pilot said that he listened to the ATIS well before his return to Camden, to reduce his workload during the subsequent approach. He understood that runway 24 was still in use. Later, when he returned for a landing, he was unable to see the wind indicator and elected to make an approach to runway 24, using 10 degrees of flap.

Ground observers subsequently saw the aircraft travelling along runway 24 at a very low height, with the pilot apparently attempting to land. When it reached a position some 3/4 along the runway the observers saw the aircraft adopt a high nose attitude and attempt to climb away. The aircraft continued in a high nose attitude, at low forward speed, towards rising ground to the west of the aerodrome. It became apparent that the angle of climb was insufficient to overcome the terrain. The aircraft was then observed to strike trees and disappear.

The aircraft came to rest in the front yard of a house, after colliding with a number of trees. Both occupants were able to escape with minor injuries. A subsequent examination concluded that the aircraft had been capable of normal operation at the time of the accident.

An investigation found that in the 30 minutes after the tower closed down, there had been a significant wind shift. At 1600, the time of closedown, the recorded wind direction and velocity was 300/13 kt. The next reading at 1630 showed the wind had changed to 100/12 kt. The effect of that wind shift was to create a substantial downwind component on runway 24.

Witnesses indicated that the wind had changed shortly after 1600, just before the pilot attempted his landing approach. The description of the event provided by the pilot, and other observers, was consistent with the pilot attempting to land the aircraft on a runway with a substantial downwind component. The angle of climb during the subsequent go-around was also adversely affected by the downwind component, and was insufficient to overcome the rising terrain.

The student was briefed by his instructor for a solo flight as part of the CPL training Block. The published route is Merredin - Wagin - Hyden - Merredin. The planned landing point for this exercise is Wagin, which has an adequate runway for the purpose. To meet the operational requirement of a 2.5 hour flight, students are permitted to divert en route Wagin to Hyden, direct to Merreden, after considering such factors as ground speed and fuel remaining.

This student elected to divert in the Merredin to Wagin leg, and proceeded to Hyden where he then conducted an unauthroised landing at a private airfield to the North of the town, not the Shire strip as published in the WA Country Airfield Guide. The student later reported that on his final approach for a landing to the South he was distracted by something close to the threshold, possibly a fence, which prompted him to change his original aiming point.

This action lead to a bounce on touch down followed by an attempted go around, during which the aircraft departed the runway centreline to the left towards some trees. He then tried to manoeuvre the aircraft back to the runway and then could not remember hearing the stall warning prior to the impact of the nose and right wing into the ground. The aircraft came to rest 10m from the runway edge sustaining considerable damage to the propellor, engine, nose and right undercarriage plus sundry damage to the airframe including the tailplane.

The aircraft was conducting spraying operations in a paddock bounded by a power line. Due to the nearness of the paddock to the power line, it was necessary for the pilot to fly the aircraft under the line at the commencement of each spray run. At the beginning of the accident run, the pilot rolled the aircraft right to clear a small tree. As he did this, the left wing contacted the power line. The aircraft then rolled inverted and struck the ground left wing first, cartwheeling several times before coming to rest inverted. The pilot was able to exit the aircraft before fire consumed the majority of the wreckage.

The pilot confirmed that the aircraft was operating normally at the time of the accident. While maneuvering to avoid the small tree, he had momentarily forgotten about the power line and did not correct quickly enough to prevent the wing contacting it.

The pilot reported that on approaching the paddock to be sprayed he did a circuit to observe wires and obstructions. He observed two sets of wires, one set running along a main road and another set running along one side of the paddock to a bore. The pilot decided to carry out some clean up runs along the bore wire first, to make the spray runs on the paddock safer. On the fourth run the pilot was intending to go over the road wires, but the landing gear snagged them, and brought the aircraft down to the ground some distance away. The pilot stated that there was a crop of tall sunflowers growing in the corner of the paddock, which made it too dangerous to go under the wires.