Summary

In January 1995, the offshore supply vessel Far Sword, along with the offshore supply vessel Lady Audrey, was engaged in support of the United States drilling vessel Glomar Robert F Bauer, operating in the North Gorgon field on the Northwest Shelf, in 720 m water depth, 43 nautical miles (80 km) north-west of Barrow Island.

During the evening of 23 January, operations commenced on recovering the Glomar Robert F Bauer's anchors, preparatory to a move to a new drilling location, Altair No.1, in the Medusa field, 54 nautical miles (100 km) west of Barrow Island.

Glomar Robert F Bauer uses an anchor buoy system, the anchor recovery operation requiring each anchor buoy to be taken on board one of the supply vessels and the anchor hauled from the seabed using the buoy pennant wire.

On the morning of 24 January, while the three-man deck party of Far Sword was positioning an anchor buoy for securing on the aft deck, a sea broke over the stern and swept them up the deck. One of the seamen needed to be transferred to the Karratha hospital, where it was confirmed that he had a number of fractured ribs and a punctured right lung.

Conclusions

These conclusions identify the different factors contributing to the accident and should not be read as apportioning blame or liability to any particular person or organisation.

The injury to the rating was the result of a number of factors that, combined with the increasing sea conditions, made the anchor recovery a marginal operation:

1. The inexperience of the ratings in anchor handling operations resulted in a lengthier operation and extended exposure time.
2. The inexperienced ratings had to start the anchor handling operation during hours of darkness.
3. The '24 hours a day' regime inhibited the Master from holding a lengthy operational and safety discussion with the crew before commencing anchor retrieval operations and from considering delaying operations until daylight.
4. The lack of detailed planning resulted in the tugger wire not being deployed correctly.
5. The solid design of the vessel's safety barrier provided very limited escape routes to the deck party, instilling an instinct to grab and hold on to the nearest object, rather than to move outboard of the barrier, or to climb up on it.
6. The Bauer was not equipped with chain chasers, using instead an anchor buoy system, necessitating a long exposure time for the standby vessels' crews during anchor handling operations.

As a result of this and other occurrences, together with a systemic investigation of the Class G Airspace demonstration, the Bureau of Air Safety Investigation issued interim recommendation IR980253 to the Civil Aviation Safety Authority on 8 December 1998:

"The Bureau of Air Safety Investigation believes that the Class G Airspace Demonstration has served its purpose. In the light of the safety concerns identified by this investigation, BASI recommends that the Civil Aviation Safety Authority should now terminate the demonstration. The results of the demonstration should be subject to a comprehensive evaluation that specifically addresses the safety concerns identified by BASI.

The evaluation process should take into account the time required to:

1. review and analyse the demonstration;
2. refine the model where required and conduct a proper safety analysis; and
3. provide a comprehensive and effective education and training program for any subsequent changes to Class G Airspace.

If this is not achieved, the deficiencies identified in this investigation are likely to be repeated, thereby seriously compromising the successful introduction of future changes to airspace including reintroduction of Class G Airspace incorporating Radar Information Service and National Advisory Frequency".

The Bureau of Air Safety Investigation simultaneously issued the following related interim recommendations to the Civil Aviation Safety Authority:

"IR980260

The Bureau of Air Safety Investigation recommends that the Civil Aviation Safety Authority review program management policies and procedures for current and proposed changes to the aviation system, in the light of experience gained from the present Class G Airspace Demonstration.

IR980261

The Bureau of Air Safety Investigation recommends that the Civil Aviation Safety Authority, the Department of Transport and Regional Services and Airservices Australia review and clarify the roles and responsibilities of the respective organisations in relation to the regulation, design and management of airspace to ensure the safety integrity of the aviation system".

The Bureau of Air Safety Investigation simultaneously issued IR980261 to the Department of Transport and Regional Services and Airservices Australia as IR980256 and IR980257 respectively.

Subsequently, the Minister for Transport and Regional Services announced in Parliament on 9 December 1998 that the demonstration would cease on 13 December 1998.

FACTUAL INFORMATION

History of the flight

At approximately 0910 EST, the aircraft took off from runway 32 at Horn Island and commenced a normal climb. Shortly after, it adopted a nose-high attitude and commenced a wingover type manoeuvre to the right. Witnesses described the aircraft as being in a nose-low attitude, and at a height of approximately 600 ft to 700 ft above ground level after the completion of this manoeuvre. It then abruptly adopted a level attitude and rapidly entered a spin to the left.

Witnesses on the ground reported that at approximately the same time as the aircraft entered the spin, engine power became asymmetric, with the right engine continuing to deliver considerable power. The aircraft continued to descend in a fully developed flat spin, with no observed signs of an attempt to recover. The impact was heard shortly after the aircraft descended behind vegetation to the north-west of the aerodrome. The accident was reported to Flight Service by radio at 0918.

The wreckage was located on a beach approximately 2 km to the north-west of the aerodrome. The aircraft was destroyed by impact forces and the pilot sustained fatal injuries.

Wreckage examination

Examination of the wreckage indicated that the aircraft had impacted the ground in an almost flat attitude while rotating in an anticlockwise direction.

Examination of the airframe and flight control systems did not reveal any pre-impact malfunction or defect which may have contributed to the accident.

Damage to the right engine, and propeller blade slash marks on the trunks of trees at the accident site, indicated that the right engine was producing considerable power at impact. The left propeller was in the feathered position. The left engine and propeller were removed from the wreckage for further examination. There was no evidence of pre-existing defects. Subsequent tests determined that the engine was capable of producing power prior to impact.

Maintenance history

A review of the aircraft, engine and propeller logbooks found nothing to suggest any irregularity that was likely to have affected the normal operation of the aircraft during this flight.

Pilot information

The pilot was the holder of an Australian commercial pilot licence for aeroplanes.  He held a valid medical certificate, multi-engine command instrument rating and grade one instructor rating. At the time of the accident, he was the chief flying instructor for the company's flying school and carried out check-and-training duties for the company's charter operations. He had accumulated approximately 11,740 flying hours, of which 7,750 hours were acting as pilot in command of multi-engine aircraft.

The pilot was endorsed on the Aero Commander 500S on 15 October 1993 and had accumulated in excess of 119 hours on type. He had flown the accident aircraft on a number of occasions.

Results of the post-mortem and toxicological examination of the pilot did not indicate signs of incapacitation due to a medical condition or the presence of drugs or alcohol.

A review of the pilot's activities in the 72 hours prior to the accident established that he had been flying for another company in Cairns during the previous weekend. He had a late night on Sunday and was observed to consume a considerable amount of alcohol and smoke heavily on this occasion, activities which he reportedly had not engaged in for some time. He was described as in good spirits on Monday morning and departed for Horn Island during the afternoon. Monday evening was spent with other company employees at the local motel. During this period, he was not observed to consume alcohol. He returned to the company's accommodation on the island with one of the company pilots. They spent a short time talking before retiring at approximately 2200.

On the morning of the accident, the pilot was rostered to train one of the company pilots on the Aero Commander 500. After arriving at the airport by bus at approximately 0900 EST, he was observed to walk through the terminal and proceed directly to the aircraft. He was not wearing his uniform. Shortly after, the pilot was observed to start the engines of the aircraft and taxi to the runway holding point. Witnesses reported that they did not observe the pilot carry out a pre-flight inspection of the aircraft or any pre-take off engine checks.

Weather

At the time of the accident the wind was a light south-easterly and there was scattered cloud with a base of approximately 1,800 ft. The weather was not considered a factor in this occurrence.

ANALYSIS

The investigation established that the aircraft was capable of normal operation prior to impact. No evidence was found to indicate that the performance of the pilot was affected by any physiological condition which may have adversely influenced his ability to carry out his tasks.

As a result of discussions with a number of witnesses and friends of the pilot, it is apparent that his behaviour immediately prior to the accident was not in keeping with what most described as his thorough and professional attitude to aviation. Witnesses and friends also stated that they had never known the pilot to commence a flight when not wearing his uniform and without having carried out a pre-flight inspection of the aircraft or any pre-take-off engine checks.

The aircraft entered a flat spin at a height from which recovery may have been possible. The reason the aircraft entered the spin and subsequently crashed could not be determined.

CONCLUSIONS

Findings

1. The pilot held a valid pilot licence and medical certificate.
2. The pilot was endorsed on the aircraft type.
3. The aircraft entered a flat spin to the left with no reported signs of an attempt to recover.
4. The aircraft struck the ground whilst established in a flat left spin.
5. The right engine was producing considerable power prior to impact.
6. Indications were that the left engine was producing little or no power. Its propeller was in the feathered position prior to impact.
7. No evidence was found to indicate a malfunction or pre-existing defect with the aircraft or its systems which may have affected normal operation during this flight.
8. No evidence was found to indicate pilot incapacitation as the result of a medical condition or the presence of alcohol or drugs.
9. The pilot's behaviour on the morning of the accident was not consistent with what was generally accepted to be a thorough and professional attitude to aviation.

FACTUAL INFORMATION

Sequence of Events

The flight was planned to transport three passengers to Agnes Waters, returning on the same day.

The pilot commenced planning about two weeks before the flight. On the morning of the flight, he submitted a visual flight rules (VFR) flight plan which was received in Brisbane at 0543 EST. The flight plan indicated a planned departure time from Maroochydore of 0630, to cruise at 6,500 ft tracking about 5 NM west of Bundaberg and with a search and rescue time (SARTIME) for Agnes Waters of 1100.

At 0708 the pilot reported to Brisbane Flight Service that he was descending to 3,500 ft due to cloud. This was the last known radio transmission from the pilot.

Witnesses heard the aircraft circling for 5-10 minutes in the Kolan South area (10 NM west of Bundaberg airport) at about 0740. The engine sounded normal, the sound fading and increasing as the aircraft circled. One witness reported hearing a burst of engine power immediately followed by the sound of ground impact. None of the witnesses saw the aircraft before the accident.

The wreckage was found in an open, fallow cane field. The accident was not survivable, and all four occupants were killed by impact forces.

Pilot in Command

The pilot held a valid class 2 medical certificate for a private pilot licence. There was no known medical condition which could have contributed to the accident.

The pilot was adequately rested prior to the accident.

Of his 342 flying hours, the pilot had completed 32 hours on this type of aircraft. He had flown 4 hours (2 hours on type) in the previous 90 days.

Three days before the accident, the pilot had taken part in a club competition with an instructor pilot seated in the right seat. The competition included a climb under simulated instrument meteorological conditions (IMC) from 500 ft to 2,000 ft and some 45-degree angle of bank turns. This exercise was completed to the satisfaction of the instructor pilot. The pilot had logged 7 hours instrument flight time although he did not hold an instrument rating.

The pilot's last biennial flight review was conducted five months before the accident.

Meteorology

Over the period of the flight, the general weather in the area consisted of a very moist, unstable light northerly flow ahead of a trough to the west of the Great Dividing Range. Winds below 5,000 ft were north-westerly at less than 15 kts. In the Maroochydore area at 0600 there was scattered cumuliform cloud with a base around 3,000 ft and broken middle level cloud. ('Scattered' indicates 1-4 octas of cloud cover and 'broken' 5-7 octas.) Further north, the main base lowered and became broken to overcast by Maryborough.

The area forecast (ARFOR) for Area 40 covering the period 0130 to 1800 issued by the Bureau of Meteorology indicated thunderstorms and showers clearing from the coast by 0400 and redeveloping after 1200. The amended Area 40 forecast for the period 0600 to 2100 indicated scattered showers on the coast north of Bundaberg until 0900, isolated showers until 1200 and scattered showers and thunderstorms after 1200.

Terminal area forecasts (TAFs) and amended TAFs issued for Maryborough and Bundaberg were similar. The forecast issued at 0426 indicated a light northerly wind, scattered cumulus cloud and temporary periods after 1300 (up to 60 minutes) of thunderstorm activity. These forecasts were amended at 0725 to reflect intermittent periods (up to 30 minutes) of reduced visibility, showers, rain, and low cloud for the period from 0700 to 1300; and again at 0803 to predict intermittent periods of thunderstorms and rain between 0800 and 1300.

A pilot who arrived at Bundaberg at about 0710 from Archerfield stated that conditions were visual until about 20 NM south of Bundaberg when he encountered heavy rain. Maryborough had some cloud, but the circuit area was visual. He made a distance measuring equipment (DME) arrival to Bundaberg down to 840 ft before landing. He stated that there were lower patches of cloud with rain, and he estimated the cloud base on departure 25 minutes later to be about 900 ft.

A second pilot departed Bundaberg soon after 0700. He said the cloud base was about 400 ft, broken and in layers. There was no rain, and visibility was about 10 NM.

A third pilot who also departed soon after 0700 reported scattered cloud at about 300 ft in layers and that the coastal route to the south-east appeared to be good. To the north-west through north to the north-east, visibility was restricted in falling rain. He said the cloud extended to Flight Level (FL) 170.

A pilot who arrived at 0905 said that the cloud was unbroken from FL160 to 600 ft from 30 NM south of Bundaberg. There were build-ups with heavy rain to the north and south of Bundaberg.

Witnesses on the ground in the South Kolan area reported hearing a thunderstorm at the time of the accident. They reported low cloud and light rain.

Communications

A transmission from the pilot at 0708 was the last recorded transmission from the aircraft. The Bundaberg aviation data tape did not record any transmissions from the accident aircraft.

An analysis of the appropriate radar tapes did not indicate any trace of the aircraft.

Wreckage and Impact

The aircraft had impacted the ground in a steep nose-down attitude, right wing low, while rotating to the right. The aircraft disintegrated on impact, with the majority of the wreckage coming to rest about 23 m forward of the initial impact site.

The right wingtip had struck the ground first about 4 m before the main impact, followed by the right mainwheel.

After the main impact, the aircraft broke up, with sections of wreckage found up to 60 m from the main impact point. Fuel was spread over a wide area to the right of the wreckage centreline; consequently, the wreckage did not burn.

Both wings displayed typical evidence of in-flight overstress in a positive 'g' direction, indicating a possible attempt to recover the aircraft to level flight before impact. All control surfaces were present and control cables and push rods were still attached although severely disrupted.

The engine was subjected to an on-site examination and later to a partial tear down. No pre-accident fault could be found with the engine. The lack of pre-impact damage is supported by witness evidence of hearing the sound of an aircraft's engine.

Other components were examined in an attempt to determine aircraft configuration, attitude, and serviceability. The attitude indicator gyro and the vacuum pump both showed signs of operation before impact, but the degree of damage made obtaining any useful information from any of the other recovered components impossible. A further difficulty was encountered in finding small components due to their wide distribution and a combination of soft soil and torrential rain.

The aircraft was fitted with a Trimble global positioning system (GPS) mounted on the instrument panel with tape but not connected to the aircraft. The pilot had prepared the GPS the day before the accident and had asked for help from another pilot to program it. One pilot claimed that it was not an easy GPS to use and that he had difficulty turning it on. No information was recovered from the GPS.

Emergency Locator Transmitter

The aircraft was equipped with a fixed Dorne and Margolin 6.1 emergency locator transmitter (ELT) which complied with TSO C91. The ELT was severely damaged in the accident and failed to operate.

Weight and Balance

The aircraft's weight was estimated at 1,270 kg at take-off, which is within weight limits. Load distribution could not be determined.

Aircraft Documentation

The current maintenance release was not found at the accident site. However, previous maintenance releases and aircraft logbooks indicated that all relevant engine and airframe airworthiness directives were incorporated and that the aircraft should have been serviceable for the flight.

ANALYSIS

The pilot probably held ARFORs and TAFs issued at 0130 and 0426 which indicated little concern for the period of the flight to Agnes Waters and return. The ARFOR indicated only scattered showers for the period and the TAF predicted scattered cumulus cloud. Consequently, the pilot probably had few concerns about proceeding VFR on his planned track.

A TAF issued for Bundaberg at 0725 indicated intermittent periods from 0700 to 1300 of reduced visibility, showers, rain, and cloud at 900 ft. The pilot was probably not aware of this forecast.

The aircraft seemed to be serviceable at the time of impact. The engine was operating, and the airframe was intact. No evidence was found to suggest any flight control circuit failures. Damage to the attitude indicator gyro and the vacuum pump indicated that both of these components were operating at impact. Consequently, the aircraft flight instruments were probably operating normally.

The pilot was considered to be cautious and conscientious in his approach to flight preparation and in-flight procedures. He commenced planning the trip two weeks before departure by discussing the route with instructor pilots and preparing a chart. He had sought help in preparing the GPS and participated in a club competition three days before the accident. On the day of the flight, the pilot had submitted a flight plan.

About 30 minutes before the accident the pilot had descended to avoid cloud. This indicates that his intention was to continue with the planned flight and to remain visual. However, at some point near Bundaberg the aircraft entered cloud. This may have been inadvertent, or the pilot, relying on the forecast which he held, may have decided to fly through what he thought was a small area of cloud.

Witnesses reported the aircraft circling for up to 10 minutes and during this manoeuvring, the pilot probably entered a thunderstorm. A combination of low instrument hours, no instrument rating and turbulence in the cloud could lead to pilot disorientation and loss of control.

CONCLUSIONS

Findings

1. The pilot in command held a valid pilot licence.
2. The pilot in command did not hold an instrument rating.
3. There was no evidence found to indicate that the performance of the pilot in command was adversely affected by any physical or medical condition.
4. There was no evidence found to indicate that the aircraft was other than airworthy for the flight.
5. The weather forecasts obtained by the pilot indicated that the weather was suitable for the flight as planned.
6. The pilot submitted a VFR flight plan for the Maroochydore to Agnes Waters route.
7. While en route, the weather deteriorated, necessitating a descent by the aircraft.
8. Amended forecasts issued while the aircraft was in flight were probably not received by the pilot.
9. The aircraft entered cloud.
10. The accident was not survivable.

Significant Factors

1. Weather conditions encountered south of Bundaberg were considerably worse than the forecast held by the pilot.
2. The pilot allowed the aircraft to enter cloud.
3. The pilot in command lost control of the aircraft and was not able to recover control before ground impact.

At the request of and under the direction of BASI, the engine manufacturer investigated several engine failure modes during the investigation, including the misalignment of the reduction gearbox carrier housing assembly bearing bores

Following the accident the engine manufacturer has introduced an improved design N2 spur gear nut retainer and updated the overhaul assembly instructions for this component. The new nut retainer was incorporated to prevent tang fatigue failures. The improvement to the nut retainer was instituted as a result of an investigation into nut retainer failures in the U.S. Army UH-1 helicopter fleet. This investigation was initiated in April 1994.

An improved nut retainer was introduced on 13 Mar 1996 (Illustrated Parts Catalogue Temporary Revision No 6). Updated assembly instructions involving the match marking of the retainer and gearshaft, lubrication of the nut and a doubling of the torque on the nut were also introduced on 13 Mar 1996 (Overhaul Manual Temporary Revision No 16). A Service Bulletin (T5313B/T5317-0081) requiring replacement of nut retainers with improved retainers within 300 hours or two years was issued in May 1996. The Service Bulletin cites several instances of spur gear nut retainer separation in the U.S. Army T53 fleet. An Airworthiness Directive (AD 97-07-05) mandating the requirements of the Service Bulletin was issued by the U.S. Federal Aviation Administration in June 1997.

FACTUAL INFORMATION

Sequence of events

The pilot had been spraying cane fields near the accident site. The aircraft was observed flying towards an airstrip about 1 km away where a spray hopper was positioned on a trailer. At about 0650 hours, the aircraft was seen flying straight and level towards the airstrip. The aircraft was then seen to strike powerlines, roll inverted and impact the ground. The aircraft came to rest inverted. The aircraft had impacted two high-voltage powerlines approximately 17 m above ground level.

Damage to aircraft

The fuselage forward of the wing leading edge was destroyed and the engine was forced rearwards into the hopper. The main cockpit structure was intact, and the seat and harness were undamaged. The windscreen was broken but the windscreen frame was intact. The instrument panel was badly damaged by impact from the pilot. The fuselage rear of the cockpit area was creased but the tailplane and fin were intact, suffering only minor damage. The right wing outboard leading-edge section was severed by powerline contact. The aircraft severed two wires. The top aerial earth wire consisted of three strands of 2.55mm aluminium conductor wound around four strands of 2.5mm steel conductor, and a 66-kilovolt cable consisted of 30 strands of 2.55mm aluminium conductor wound around seven strands of 2.5mm steel conductor.

Meteorological information

The weather was fine at the time of the accident, with a light south-easterly wind.

Wreckage examination

There were no mechanical defects discovered with the airframe or the engine which may have led to the development of the accident. The seat harness was found undone immediately after the accident and did not exhibit any signs of stress as would have been expected after such impact.

Tests and research

Considerable research and testing was carried out to ascertain if there was a possibility of the seat harness being released by impact forces. Testing of the harness and buckle was conducted at Crash lab, the Roads and Traffic Authority of New South Wales test and research centre, which specialises in dynamic testing of safety harness.

Initial examination of the harness found there were no signs of severe loading on the buckle, adjusters, anchors or webbing. However, load bearing marks on the webbing of the lap and shoulder sections of the harness were evident following dynamic testing of the harness.

Dynamic testing of the aircraft safety harness was conducted to test the overall integrity of the harness and also to investigate the possibility of the over-centre buckle being inadvertently released by the occupant's abdominal region during a dynamic impact. The dynamic test demonstrated that the harness was able to restrain the anthropomorphic test dummy without evidence of abnormal distortion, separation or damage to the harness webbing and components. The test also demonstrated that the over-centre buckle did not release during dynamic impact, when correctly latched.

The testing indicated that the aircraft safety harness was not correctly fastened at impact. The possibilities were, therefore, that the harness was not worn at all by the pilot, that the harness was worn but the over-centre buckle was not correctly latched (in other words, the detent mechanism was not fully engaged), or that the buckle was inadvertently unlocked during the flight or accident sequence by clothing or arm contact with the latch.

ANALYSIS

Given that the powerline was the largest and most obvious in the area, it is difficult to understand why the pilot failed to avoid it. The possibility of the low angle of the sun momentarily dazzling the pilot was considered but this is unlikely due to the aircraft being in a right turn and heading in a south-easterly direction shortly before impact. Some witnesses described seeing what appeared to be puffs of smoke from the engine seconds before the aircraft hit the powerline. The aircraft was fitted with a smoke generator so the pilot could assess the wind drift. This could occasionally emit puffs of smoke due to small quantities of oil leaking into the system.  The possibility of an engine malfunction distracting the pilot at a crucial moment and diverting his attention to inside the cockpit cannot be discounted; however, there was no evidence found to support this theory.

Examination and testing of the seat harness led to the conclusion that the harness was not fastened at impact. The harness was not fitted with an inertia reel. The possibility that the pilot momentarily undid the harness to retrieve an item from the cockpit floor was considered. However, this is unlikely as the floor cannot be reached even with the harness undone.

SIGNIFICANT FACTORS

1. The aircraft struck a powerline, causing loss of control.
2. The pilot's seat harness was unfastened prior to or during the impact sequence for reasons unknown.

SAFETY ACTION

Action by the Civil Aviation Safety Authority

The Civil Aviation Safety Authority had previously issued Airworthiness Directive (AD) Restraint 7 Amendment 2 for this safety harness buckle [MS22013 (ASG)] in response to industry concerns about inadvertent buckle release during aerobatics.

Action by the Bureau of Air Safety Investigation

As a result of this occurrence, the Bureau of Air Safety Investigation issued Safety Advisory Notice (SAN) 960153 to the Civil Aviation Safety Authority. The safety deficiency identified was:

"AD restraint 7 Amendment 2 for safety harness buckle MS22013 (ASG) refers to utility and acrobatic category aircraft only.  The AD should address all categories of operations."

The crews of two helicopters had been engaged in survey work. On the morning of the accident, the second helicopter became unserviceable. The pilot and passenger, in conjunction with the pilot of the grounded helicopter, decided to continue on their own. About 45 minutes after commencing the flight, the helicopter flew up a dry creek line and struck a high-voltage single wire powerline. The line severed the flying controls at the mast. All control was then lost and the helicopter crashed into the dry creek bed.

When electrical power was lost at the cattle station homestead, search parties were sent in both directions along the powerline. The wreckage of the helicopter was found about 45 minutes after the power was lost.

The span of the SWER (single wire earth return) line struck by the helicopter was 490 m and was strung between two hilltops. The point of impact was approximately 40 m above the creek bed and about 20 m above the general tree canopy. This was the pilot's second day at the station. He was not familiar with the area south of the homestead which included the crash site.

Significant factors

The following factors were considered relevant to the development of the accident:

1. The pilot was flying the helicopter at low level in a survey/mustering operation.
2. The second helicopter which had been used for lookout duties was unserviceable.
3. The pilot was unfamiliar with the area.
4. He did not see the SWER line in time to avoid a collision.
5. Control of the helicopter was lost when the wire cut control rods.

FACTUAL INFORMATION

At 0721 EST, while taxiing for take-off at Coolangatta, the pilot informed the aerodrome controller that he intended to fly along the coast at 500 ft. He had not submitted a flight plan and did not require search and rescue services.

The early part of the flight to Noosa was without apparent difficulty. The aircraft was last observed by radar at 0820, crossing the coast on a north-westerly track south of the Wide Bay Restricted Area. Radar returns indicated that the aircraft was at 2,500 ft at the time. The pilot did not communicate with the Brisbane Flight Service unit.

At about 0907 witnesses on the ground heard what they believed was aircraft engine noise, which was varying in intensity, followed by a loud bang. A short time later several large pieces of aircraft were seen to fall from the low cloud base, followed by a shower of lighter material.

The Area 40 weather forecast covering the period from 0300 to 1800 on 26 October 1995, indicated wide-spread rain from stratiform, layered cloud, with a base below 1,000 ft. A clearing change, gradually moving east, was expected at the coast about midday. Pilots who flew in the area at about the time of the accident reported that the cloud mass was quite thick, with a base at about 600 ft and tops to 14,000 ft in places. Witnesses on the ground said that the cloud base was unbroken at about 500 ft above ground level. No thunderstorms were reported in the area. An Area 40 forecast was available to the pilot before the flight commenced but it is not known whether he obtained one from the Brisbane Briefing Office.

Examination of the wreckage found that the left wing had failed in overload and had separated from the fuselage.

The remainder of the aircraft structure then rapidly disintegrated. There was no evidence of an in-flight explosion. The landing gear was found in the extended position.

The validity of the aircraft's Maintenance Release expired on 20 October 1995.

The pilot was the owner of the aircraft, and he used it almost exclusively for transport between the Gold Coast and Rockhampton where he had business commitments on a semi-regular basis. On the day of the accident, he had business scheduled in Rockhampton. He did not hold an instrument rating but did hold a night visual flight rules (NVFR) rating. His logbook showed that he had completed his endorsement training in the aircraft in October 1990. He had not undertaken a biennial flight review within the two years prior to the accident.

In 1990 the pilot underwent heart bypass surgery. Since the operation he had regained his Class 2 medical certificate and was allowed to exercise the privilege of his pilot's licence. The post-mortem examination revealed the presence of ischaemic heart disease, a deficiency of blood in part due to functional constriction or actual obstruction of a blood vessel.

ANALYSIS

Weather and Flight Planning

Both the Area 40 forecast and actual weather reports indicated that it was unlikely that the pilot could have completed his flight in visual meteorological conditions.

The Pilot

Examination of his logbook showed that the pilot first flew VH-YAB during training for a Constant Speed (Propeller) and Retractable Gear endorsement in October 1990. In September 1991 he obtained a NVFR rating. The last log-book entry was dated March 1995. However, a detailed, current notebook recorded his flying activities. He had noted 45 flight hours in VH-YAB since March 1995, mostly on flights to and from Rockhampton.

The NVFR rating is not regarded by the Civil Aviation Safety Authority (CASA) as an instrument rating; however, the pilot would have gained limited instrument flying experience during his training for the rating.  A passenger on an earlier flight said that on one occasion they were caught above cloud. The aircraft entered cloud and seemed to be out of control for a period of time.

The post-mortem examination report revealed the presence of ischaemic heart disease. The report found that there may have been a cardiac episode prior to the crash which affected the pilot. With the degree of ischaemic heart disease found, any relative hypoxia of the myocardium might have precipitated a rapid and/or irregular rhythm, bringing about left ventricular failure. The report noted that anxiety with a rapid heart rate might trigger such a sequence. A specialist report from the Directorate of Aviation Medicine, CASA, endorsed the findings of the post-mortem examination report, adding that unfavourable in-flight conditions may have brought on some degree of myocardial ischemia through anxiety.

Aircraft Operation and Crash Site Examination

The crash site is situated on the direct track between Maroochydore and Gladstone. Examination of the aircraft's gyro flight instruments confirmed that they were functioning up to the point of breakup. The Piper Auto control 111 automatic pilot was switched on.  A Magellan NAV 1000 PLUS (Marine) Global Positioning System (GPS) had been connected to the aircraft's electrical system. All GPS data was lost due to the loss of aircraft power supply and its battery pack backup. However, it is possible that the pilot had the relevant data entered in the GPS receiver and was flying along the route.

The altitude at which the aircraft broke up could not be determined. Examination of the recorded radar tapes did not show the aircraft. The Mt Alma radar near Rockhampton is a monopulse secondary surveillance radar which relies on an operating aircraft secondary surveillance radar transponder. The pilot may have switched his transponder off, or the aircraft may have been operating below the radar horizon. Interpolation of radar coverage maps indicated that the radar horizon is approximately 6,000 ft over the crash site.

Witnesses described the engine sound as varying before the aircraft broke up. The varying engine noise was probably due to the doppler effect as the aircraft, relative to the witnesses, continually turned away and towards them in a downward spiral.

The aircraft had an automatic gear extension system which lowers the landing gear when the speed drops below about 90 kts. That the landing gear was down and locked could indicate that the air speed dropped below normal cruise speed some time before the breakup, or that the gear was deliberately lowered.

CONCLUSIONS

Findings

1. The aircraft was overdue for maintenance but was otherwise serviceable for flight as far as could be determined.
2. The pilot was not trained or rated for flight under instrument flight rules.
3. On a previous flight, the pilot had flown into cloud and probably lost control of his aircraft.
4. The pilot had scheduled business in Rockhampton on the day of the accident.
5. The weather was unsuitable for visual flight.
6. The pilot continued the flight without visual reference to the ground or horizon.
7. The pilot was suffering from ischaemic heart disease and may have been incapacitated.
8. The pilot lost control of the aircraft.
9. The aircraft was overstressed and as a result broke up in flight.

Significant factors

1. The pilot was unable to continue visual flight rules flight along the coast as planned and entered cloud, probably relying on his autopilot and GPS to aid him in control and guidance of his aircraft.
2. Control of the aircraft was lost by the pilot either through disorientation, incapacity, or a combination of both.

1. FACTUAL INFORMATION

1.1 History of the flight

The pilot had commenced mustering at Kilclooney Station at about 0700 EST. A refuelling stop was made at about 0930 when the mustering operation had been completed. After refuelling, the pilot took off and returned to the homestead, which was about 5 minutes flying time away, intending to collect his swag and the helicopter canopy cover and then return to his home base at Greenvale, 76 km west of Kilclooney. The pilot phoned his wife at about 1045 to say he was departing Kilclooney. At about 1050 the power supply to the homestead failed. The homestead was unattended at the time. At 1330 the company chief pilot reported to Brisbane Search and Rescue (SAR) the aircraft had not arrived at Greenvale. At 1348 the Brisbane Area Approach Control Centre (AACC) co-ordinator advised SAR that an emergency locator transmitter (ELT) signal had been heard by an overflying aircraft. The Queensland Emergency Services helicopter was then tasked to conduct a search in the area where the beacon was heard. At 1506 the wreckage of the helicopter was located at Kilclooney Station.

The helicopter had collided with a single 19-kilovolt powerline located near where the helicopter had been parked overnight. He had apparently landed near the homestead, to collect the swag which was known to be on the back of a vehicle, and then repositioned the helicopter to the parking area to pick up the canopy cover.  Two parallel wires

15 metres apart were strung from poles near the homestead and passed alongside the parking area in a southeast-northwest direction.

1.2 Impact information

It is probable that as the helicopter was approaching the parking area from the south, the left skid passed under the second wire which had a span of approximately 150 metres. The helicopter travelled a short distance before impacting the ground in a steep nose-down attitude and caught fire. The three-strand 12-gauge steel wire did not break and was trapped under tension by the wreckage for some time. The left skid was thrown clear of the fire when it became detached by heat and the wire separated from the wreckage. The wire was substantially stretched and was within 4 metres above ground level after becoming detached from the wreckage.

1.3 Pilot in command

The pilot was correctly licensed and endorsed and appeared to be in good health immediately prior the accident.

1.4 Meteorological information

Station personnel reported that the weather was fine with a moderate northerly wind at the time of the accident.

1.5 Wreckage examination

The cabin area forward of the firewall was completely destroyed by fire. The engine suffered substantial fire damage, and all engine accessories were damaged beyond the point where the serviceability of these items could be assessed. The ELT was a fixed installation in the engine bay and was destroyed by fire, it was of the type that complied with TSO C91. No mechanical failures or defects were discovered with the engine which would have prevented it from operating normally. The tail boom was separated from the main wreckage and remained clear of the fire. The tail rotor and tail rotor gearbox appeared undamaged, indicating that a steep nose-down impact had occurred.

2. ANALYSIS

The wind direction would have required an into-wind approach to be made over two wires which were about 15 metres apart. The approach over the second wire would have to be steep to achieve a touchdown near the fuel drum where the canopy cover was located and would therefore have taken the helicopter close to the second wire. During the accident sequence the helicopter actually struck the drum. Why the helicopter struck the wire could not be determined, but it is probable that the helicopter was capable of normal operation up to the time of the accident. The canopy cover was on the ground beneath an upright 200-litre fuel drum, located about 10 metres from the powerline. The helicopter was probably previously parked in this particular position as the pilot did not want to frighten horses in an adjacent paddock.

3. CONCLUSIONS

3.1 Findings

1. The pilot was correctly licensed and fit to perform the flight.
2. There were no mechanical defects discovered which may have contributed to the accident.
3. The helicopter had been previously parked in close proximity to a single strand powerline and was being manoeuvred to land at this position to allow the pilot to collect the helicopter canopy cover.
4. The wind direction required an approach from south to north over the top of the powerline.
5. The helicopter struck the powerline.

3.2 Significant factors

1. The aircraft was being manoeuvred in close proximity to a single-wire powerline.
2. The pilot failed to see and avoid the powerline.

The pilot hired the aircraft with the stated intention of conducting practice circuits at Archerfield. When he taxied, he told the Surface Movement Controller that he was proceeding to the (Archerfield) Southern Training Area. The aircraft departed the circuit area at 0927 EST.

At about 0955, a witness near Mt Warning heard an aircraft engine operating at high rpm followed by the sound of impact. Later an aerial search found the fragmented and burnt wreckage of an aircraft at the base of a near vertical cliff on the north face of Mt Warning. The aircraft had impacted head on, near the geometric centre of a large triangular shaped cliff face. The weather at the time was fine with a clear blue sky and light winds.

On the basis of information received concerning the circumstances of this occurrence, the Bureau has discontinued its investigation.