Collision with terrain

The absence of witnesses to the accident, and of an emergency radio broadcast from the pilot meant that there was no information available to the investigation about the pilot's situation immediately prior to the accident. However, the low-level manoeuvring carried out by the pilot overhead the sheltering sheep, and interaction via radio with the driver of the four-wheel drive vehicle was consistent with the pilot attempting to disturb the sheep from their position.

The steepness of the angle of bank and the nose-down pitch attitude at the aircraft's point of ground impact indicated that the aircraft was in a steep left turn at that time. Those indications and the minimal forward movement of the aircraft after ground contact were consistent with the aircraft having stalled and slipped out of the turn. The lack of aircraft rotation at impact indicated that there had been insufficient time for the stall to develop into a spin, consistent with it occurring at low level. It was likely that there was insufficient time for the pilot to recover before impacting the ground. Given the variety of opinion relating to the use of wing flap during mustering operations, the investigation was unable to determine the degree of influence that the lack of flap had on the development of the accident.

The pilot's probable focus on the sheltering sheep, together with the need to operate the UHF radio may have distracted the pilot from the primary task of flying the aircraft. In addition, any sensory illusion as a result of the pilot moving his head during the low-level manoeuvring, or inadvertent movement of the flight controls could have resulted in an unintentional increase in the aircraft's angle of bank. In either case, it was likely that the pilot was initially unaware that the aircraft was in such a steep turn, or that the airspeed was insufficient for the angle of bank. The stall warning probably sounded before the stall, but given warnings were often activated during aerial mustering, it may not have had a significant effect on the pilot's awareness of the impending stall.

A possible influence on the development of the stall was a decrease in available engine power. However, the damage to the propeller indicated that the engine was developing power at ground impact, there were no identified engine defects, there was adequate fuel on board and the pilot had flown for about 1.5 hours without any apparent performance degradation prior to the accident. That evidence indicated that the engine was capable of performing normally. Notwithstanding that evidence, the use of a mix of aviation gasoline and unleaded petrol, and the estimated dewpoint depression at about the time of the accident, meant that the investigation could not discount the possibility of the formation of carburettor icing. The result in that case was the possible loss of some engine power.

During the pilot's 18 years experience operating the Cessna 206, he would have become accustomed to the relatively large amount of engine power available during aerial mustering manoeuvres in that aircraft. The investigation considered whether the pilot might have unwittingly expected the same performance from the Cessna 150. However, the pilot had operated the Cessna 150 on aerial mustering operations for over 15 months, and it was concluded that the pilot would most probably have been aware of, and adjusted to that performance difference between the aircraft types during that time.

Although the pilot's flight reviews included the practice of stall recovery in turns, and the pilot had been mustering for 18 years, the lack of an aerial stock mustering permission meant that the pilot had not completed formalised training in all of the competencies inherent in the award of that permission. As a result, there was the potential that the pilot may have acquired and, over time, reinforced perhaps inappropriate responses to some of the risks inherent in the mustering environment. The completion by the pilot of the aeronautical experience requirements of Civil Aviation Order 29.10 would have provided some assurance that he had acquired the appropriate knowledge and skills necessary to manage the risks inherent in the low-level, low-speed, and high workload mustering environment.

Sequence of events¹

On 6 December 2005, the owner-pilot of a single-engine Cessna Aircraft Company 150G, registered VH-KPQ, was conducting aerial mustering operations on a family-owned station, 156 km north of Broken Hill, NSW. The pilot, who was the sole occupant, had departed a station airstrip at about 0710 Eastern Daylight-saving Time to coordinate the movement of sheep from an 18,000-acre paddock to shearing shed yards near the homestead. The paddock had medium to dense coverage of 2.5 m high scrub and was generally flat. Aerial mustering activity that day involved flying a north to south pattern progressively from the east to the west and directing ground-based mustering personnel to the location of the sheep. Those personnel were using two motorbikes and a four-wheel drive vehicle in the muster. All of the musterers were communicating with ultra-high frequency (UHF) radio.

At about 0835, the four-wheel drive vehicle was being used to move a few sheep along when the driver lost sight of them. The driver advised the pilot by UHF radio and shortly after the aircraft circled above the area a number of times at about 250 ft above ground level (AGL), but the pilot was reported to have not seen the sheep. The driver then sighted the sheep in thick scrub that the vehicle was unable to penetrate and advised the pilot of the situation. The pilot requested that the driver reverse and drive onto a nearby track. The driver asked the pilot to report when the sheep moved away from the scrub. There was no response. Shortly after the driver noticed smoke nearby and found that the aircraft had impacted the ground and there was an intense fire. The pilot was fatally injured.

The other musterers were in different areas of the paddock and did not observe the aircraft's descent and impact with the ground. No one heard an emergency radio broadcast from the pilot. One of the musterers observed the pilot's take-off from the station airstrip and heard the engine a number of times during the mustering before the accident and reported that it sounded normal.

Wreckage and site information

The aircraft wreckage was found approximately 400 m to the south-east from where the mustering vehicle was operating. The aircraft was upright with evidence of severe impact damage to the left wing, nose section and rear fuselage. There was evidence of intense fuel-fed fire damage to the cabin area and left wing. The main wreckage, approximately 8 m from the first ground impact mark, contained all the aircraft parts except for the nosewheel, which was found nearby.
The ground impact marks and damage to the left wing indicated that the initial impact with the ground was the outer leading edge of the left wing. In addition, the minimal damage to the shrubs surrounding the initial ground impact marks indicated that the aircraft impacted the ground with a steep left angle of bank between 70 and 80 degrees. The damage to the wing, and the nose impact position also indicated that the aircraft impacted in a nose down attitude with a high descent rate. There was no evidence of rotation.

Examination of the aircraft, including the flight control systems and engine, did not reveal any evidence of pre-impact defects. Damage to the propeller indicated that the engine was operating at ground impact. The wing flaps were found in the retracted position.

Pilot information

The pilot commenced flight training in 1987 and flew 18 hours in a Cessna 150 and 32 hours in a Cessna 172. The pilot purchased a Cessna 206 and completed his flight training in that aircraft. He was issued with a private pilot (Aeroplane) licence in 1988. There was no evidence of any low level or aerial stock mustering permission (the relevant regulations are outlined below).

Family members reported that the pilot used the Cessna 206 primarily for aerial mustering on pastoral properties that he owned in regional NSW. About 18 months prior to the accident, the pilot purchased the station north of Broken Hill and in August 2004, purchased the Cessna 150 primarily for mustering on that station.

The pilot's logbook was full and did not contain any entries after 1 October 2004. He had logged 36.5 hours flying the Cessna 150 over the station north of Broken Hill and a total of 2,041 hours. Although there were no flights logged by the pilot after 1 October 2004, family members reported that the pilot continued to fly the Cessna 206 and the Cessna 150 after that date.

The pilot's most recent flight review was competed on 24 April 2004 in his Cessna 206. The instructor who conducted the review reported that the pilot was competent and that the review had included steep turns and stall recovery. Steep turns were practiced at 3,000 ft AGL and between 45 and 60 degrees angle of bank. Stall recovery was practiced at 3,000 ft AGL and included recovery from a stall during a steep climbing turn with low power.

The pilot's logbook indicated that the pilot had completed stall and steep turn training in a Cessna 150 during his initial training in 1987/1988. There was no record of any stalls or steep turn training in a Cessna 150 since.

The Civil Aviation Safety Authority (CASA) issued the pilot with a Class 2 Medical Certificate on 30 June 2004 that was valid to 30 June 2006. That certificate contained a restriction requiring the pilot to wear distance vision correction and to have reading correction available during flight.

The pilot had been involved in mustering activities that included about two hours aerial mustering in the Cessna 150 per day during the previous two weeks. Two days before the accident the pilot did some aerial mustering in the Cessna 150 and then flew the Cessna 206 to a station in the Hay area. He was reported to have worked on the station until about 2030, before going to bed at 2300. The next morning the pilot awoke at 0600 and departed at 0830 for Wagga Wagga aerodrome, landing at 1000. At 1500, the pilot departed for the station north of Broken Hill via Hay and Broken Hill, arriving home at about 2000. The pilot worked in the sheep yards until returning to the homestead at 2130. Family members reported that the pilot was tired and had a sore shoulder for which he took a non-prescription painkiller. He retired to bed shortly after.

On the day of the accident, the pilot woke at about 0615 and at about 0630 flew the Cessna 206 from the airstrip near the homestead to another station airstrip where the Cessna 150 was hangered. It was reported that he was in good spirits and appeared well rested.

At the time of writing this report, the postmortem report was not available. There was no evidence of any physiological condition that may have contributed to the accident.

Aircraft information

The Cessna 150G was a two-seat, high wing aircraft equipped with a Continental O-200A engine rated at 100 HP (74.6 kW). The aircraft was fitted with a pneumatic aural stall warning system that activated 4 to 8 kts before the stall was reached. That was the only aural warning known to be fitted to the aircraft.

The pilot operated the Cessna 150 on a mixture of 10% aviation gasoline (Avgas) and 90% unleaded automotive petrol as authorised by a flight manual supplement. The flight manual supplement stated that when using automotive fuel, the onset of carburettor ice may occur earlier than with Avgas under the same atmospheric conditions. Two days before the accident, the aircraft fuel tanks were reportedly filled from clean drum stock in the hangar using a hand-pump that included an in-line filter. On the morning of the accident, the pilot was observed conducting his pre-flight checks, including of the aircraft's fuel system drains.

In addition to the aviation radios, a UHF transceiver was fitted to the aircraft for use during mustering operations. The audio output from that transceiver was wired into the aircraft's phones jack, and there was a hand microphone. The pilot was reported to use an aviation headset.

The pilot's Cessna 206 was a six-seat high wing aircraft equipped with a Continental IO-520F engine rated at 300 HP (223.7 kW).

Meteorological information

The applicable aviation area forecast was valid from 0800 and predicted isolated showers and thunderstorms with broken ² cloud at 10,000 ft. The wind at 2,000 ft was expected to be from the north-west at 20 kts. Turbulence was forecast to be moderate in the broken cloud and after 1200, light to moderate below 9,000 ft.

Automatic weather observations at 0830 from the nearest Bureau of Meteorology (BoM) site at Broken Hill recorded scattered cloud at 9,500 ft and a surface wind from the south-west at 10 kts. The temperature was 26 degrees, the dewpoint was 14 degrees and the barometric pressure was 1003 hPa. There was a report of a thunderstorm and 0.2 mm precipitation between 0730 and 0800. The BoM advised that the Broken Hill observations were representative of the weather conditions at the accident site.

One of the ground-based musterers reported that at the time of the accident, the wind was a light south-westerly and it was overcast and humid.

The 0830 Broken Hill temperature and dewpoint depression³ was plotted on a Carburettor icing - probability chart. That chart predicted moderate icing at cruise power, or serious icing at descent power in those conditions.

Current regulations

Civil Aviation Order 29.10 defines aerial stock mustering as 'the use of aircraft to locate, direct and concentrate livestock whilst flying below 500 feet above ground level'. The aeronautical experience requirements for a pilot to engage in mustering operations include that the pilot must complete 5 hours low flying training and an exam to confirm pilot proficiency, followed by 10 hours operational training. That training included:

• level, climbing and descending turns and recovery from the stall at up to 60 degrees angle of bank
• slow flying and the methods of losing height at low level
• steep climbing and descending turns away from and returning to a ground reference.

Aerial stock mustering

Aerial mustering of stock in aeroplanes such as the Cessna 150 usually involves low-level flight including steep turns at low airspeed to allow the pilot to monitor the location and movement of stock, and to guide ground-based personnel accordingly. It was reported that the pilot usually conducted aerial mustering at an estimated height of between 150 and 200 ft AGL, but if sheep found cover in dense scrub, the pilot would sometimes fly lower and apply power over the sheep to encourage them to move.

Turns are a significant risk during aerial mustering in aeroplanes due to the reduction in vertical lift component and significant increase in stall speed⁴ with bank angles over 60 degrees. To maintain height in a turn at a constant airspeed requires an increase in lift, which produces an increase in drag that necessitates an increase in engine power. Depending on the angle of bank and the conditions, maximum engine power may not be sufficient to prevent a descent.

The use of small angles of flap reduces the stall speed and lowers the nose angle for a particular airspeed. Although one low-level flying expert indicated that use of flap was advantageous during low-speed turns, opinion amongst pilots with experience in low-level operations regarding the use of flap during those operations varied.

One of the ground-based musterers reported that he heard a buzzer twice in the background of some of the pilot's UHF radio transmissions. That included while the aircraft was circling shortly before the accident. He also reported hearing the same buzzer during the pilot's previous mustering operations. An experienced aeroplane mustering pilot and instructor reported that it was common for the stall warning to activate in the steeply banked turns used during aerial mustering operations.

A number of potential sensory illusions can result in mustering pilots inadvertently applying excessive bank angles during turns. If a pilot's head is orientated into a turn (such as looking at the ground or stock) and is then quickly rotated away, the pilot's vestibular balance system can produce a sensation that the aircraft is underbanked. A visual illusion that the aircraft is skidding out of a turn can occur when turning from downwind to upwind while looking at the ground, also giving the sensation that the aircraft is underbanked.

When pilots are paying very close attention to stock by moving their head during a turn, they may tend to move the flight controls in sympathy with head-body movement. This can lead to inadvertent overbanking. Distractions during a turn, such as looking for stock or using a radio, can also increase the risk of inadvertently steepening the turn and/or allowing the airspeed to decay.

1. Only those investigation areas identified by the headings and sub headings were considered to be relevant to the circumstances of the occurrence.
2. Five to seven eighths of the sky obscured by cloud.
3. Dew point depression is calculated by subtracting the dewpoint from the ambient temperature.
4. Stall speed is the airspeed at which the stalling angle of attack (angle between effective wing chord line and relative airflow) occurs resulting in rapid decrease in lift

On 6 December 2005, the owner-pilot of a single-engine Cessna Aircraft Company 150G, registered VH-KPQ, was conducting aerial mustering operations on a family-owned station, 156 km north of Broken Hill, NSW.

At about 0835 Eastern Daylight-saving Time, the pilot was observed to circle some sheep at about 250 ft above ground level. Shortly after, ground mustering personnel noticed smoke nearby and found that the aircraft had impacted the ground and there was an intense fire. The pilot, who was the sole occupant of the aircraft, was fatally injured.

The aircraft wreckage was found approximately 400 m to the south-east from where the pilot was circling. The aircraft was upright with evidence of severe impact damage to the left wing, nose section and rear fuselage.

Examination of the aircraft, including the flight control systems and engine, did not reveal any evidence of pre-impact defects. Damage to the propeller indicated that the engine was operating at ground impact. The wing flaps were found in the retracted position.

The steepness of the angle of bank and the nose-down pitch attitude at the aircraft's point of ground impact indicated that the aircraft was in a steep left turn at that time. Those indications and the minimal forward movement of the aircraft after ground contact were consistent with the aircraft having stalled and slipped out of the turn. The lack of aircraft rotation at impact indicated that there had been insufficient time for the stall to develop into a spin, consistent with it occurring at low level.

The investigation concluded that the aircraft stalled at a height from which the pilot was unable to effect recovery.

At about 1425 Western Standard Time on 22 October 2005, an Air Tractor AT-602 aircraft, registered VH-NIT, impacted terrain approximately 100 metres south of the perimeter fence of Ballidu aerodrome, WA. The pilot was carrying out a series of familiarisation flights. He was the sole occupant of the aircraft and was fatally injured.

Witnesses recalled that the aircraft had dropped a quantity of water at low level over the aerodrome. Soon after that drop, the nose of the aircraft pitched steeply towards the ground and the aircraft descended into terrain.

The aircraft impacted terrain in a slightly right wing-low, almost nose-level attitude at a high vertical rate of descent, but with low forward speed.

Examination of the wreckage did not identify any anomaly that could have affected the normal operation of the aircraft during the accident flight. Examination of the engine indicated that it was producing power at the time of terrain impact.

Toxicology testing revealed that the pilot had ingested cannabis. Specialist medical advice was that the results of the toxicology testing would be consistent with the pilot using cannabis sometime during the 24 hours prior to the accident.

The physical and witness evidence was consistent with the pilot losing control of the aircraft at low altitude, most probably as the result of an inadvertent aerodynamic stall. There was insufficient altitude to recover the aircraft to level flight.

The overriding survivor, witness and physical evidence was that the helicopter's engine was operating normally up to and including at the time of ground impact. On that basis, the investigation concluded that the performance of the engine had not contributed to the development of the occurrence.

Application of the requirements of the Aeronautical Information Publication (AIP) to the time of last light at Yalda Downs meant that a pilot in command who did not hold a night Visual Flight Rules (VFR) rating should have planned to arrive at Yalda Downs no later than 1816. In addition, the reported thin layer of cloud in this instance suggested that the planned arrival time should probably have been adjusted to earlier than 1816. The reported time of departure from Border Downs of 1800, and normal time interval for the planned flight to Yalda Downs of 1 hour 15 minutes, meant that the occurrence pilot attempted a flight for which:

• he was not qualified
• the equipment standard of the helicopter was not adequate.

Each increased the likelihood, and therefore risk that the pilot might become disoriented in the dark night conditions, resulting in a situation from which he was unable to recover.

The content of the approved flight manual (AFM) meant that the pilot ought to have been aware of the risk of his becoming disoriented when operating the helicopter in dark night conditions. The reported operation of the helicopter at about 30 ft above ground level minimised the time available for the pilot to recover from any disorientation before impacting the ground. In addition, it was likely that the climbing right U-turn eroded the already marginal outside references that the pilot may have gained as a result of identifying the lights and road as he passed north abeam Calindary. As indicated to pilots in the Safety Notices in the AFM, the likely result was that the impact with the ground was almost inevitable.

The action of the pilot to request successive property owners along the planned route to illuminate their homesteads' external lighting could have been interpreted to have had the secondary benefit of acting as a replacement for the flight notification requirements for flight through a Designated Remote Area. However, that was not an approved means of providing flight notification, and was based on the assumption that each of those property owners would be at home and respond to the pilot's radio transmissions.

That lack of a formal flight notification, and the apparent omission by the pilot to carry an Emergency Locator Transmitter meant that, had the accident not been observed by the witnesses at Calindary, the subsequent search and rescue effort could have been delayed. Any delay in locating the survivor had the potential to have:

• adversely affected the survivor's subsequent recovery from his injuries
• significantly complicated the survivor's injuries
• diminished the survivor's chances of survival.

At about 1800 Central Standard Time on 6 October 2005, a Robinson Helicopter Company model R22 Beta helicopter (R22), registered VH-HUZ, departed Border Downs, NSW on a private flight to the pilot's property at Yalda Downs, NSW with the pilot and one passenger on board. The helicopter subsequently crashed near a homestead at Calindary Station (Calindary), fatally injuring the pilot and seriously injuring the passenger.

A hearing witness¹ at Border Downs who was also a pilot and endorsed to fly the R22, had previously flown the occurrence helicopter. He reported that the helicopter 'sounded completely normal' during the take-off and departure from Border Downs. He indicated that the normal time interval for the flight to Yalda Downs was about 1 hour 15 minutes.

Witnesses at a number of properties along the route flown by the pilot reported that, as the flight progressed, the pilot requested by radio for each of them to illuminate their external homestead lights. The reason given by the pilot for those requests included, earlier in the flight, for the pilot to 'get his bearings' and, as the helicopter approached Calindary, to assist the pilot to identify two sets of power lines that crossed the main west to east road about 1 and 3 kms west of the property respectively. In response to the pilot's request, the property owners at Calindary reported that they parked their vehicle on top of a sand embankment that was about 100 m south of the main road. The vehicle's spotlights, and a third hand-held spotlight, were illuminated in the direction of the helicopter's anticipated approach.

The pilot advised the property owners by radio that he had sighted their spotlights. The property owners reported that they suggested to the pilot that he should land at Calindary and use one of their vehicles to return to Yalda Downs by road. The pilot declined that suggestion and indicated that, after picking up the road from Calindary to Yalda Downs, he would continue with the flight. The property owner estimated that the helicopter was below 30 ft above ground level (AGL) at that time, and described the helicopter's 'powerful white lights' as being visible 'down amongst the trees'. The survivor indicated that the pilot manoeuvred the helicopter in order for the helicopter's landing lights to criss-cross the road.

One of the witnesses at Calindary, with extensive experience flying aeroplanes, stated that there was nothing abnormal about the sound of the helicopter or its engine as it passed the vehicle's position, or immediately prior to the ground impact.

The survivor stated that, shortly after passing Calindary, the road appeared to merge with the surrounding bush and the pilot turned the helicopter to visually reacquire the road. The property owners at Calindary reported that the helicopter commenced a climbing right U-turn, before returning in a westerly direction and descending at an estimated angle to the horizon of 20 to 30 degrees. The survivor indicated that, during the turn and until the impact with the ground:

• he heard no abnormal noises from the helicopter
• he did not observe the illumination of any warning lights in the cockpit
• there was no apparent apprehension or degree of panic displayed by the pilot.

At about 1921, the helicopter impacted a sand hill a number of times and was destroyed by the impact forces and post-impact fire.

The pilot held a private pilot (helicopter) licence, was endorsed to fly the R22 and was reported to have about 9,000 hours flying experience. The pilot did not hold a night Visual Flight Rules (VFR) rating. The requirements of Civil Aviation Regulation (CAR) 174C(1) included that the pilot was required to have held that rating in order to conduct a flight at night under the VFR.

The pilot last undertook a medical examination in order to renew his Class 2 Medical Certificate in January 2002. There was no evidence that:

• the pilot finalised the administrative requirements for the renewal of that certificate
• the pilot held a valid Class 2 Medical Certificate at the time of the occurrence
• the Civil Aviation Safety Authority (CASA) had given the pilot permission to continue flying without a current medical certificate.

CAR 5.04(1) required that:

Without the permission of CASA, the holder of a flight crew license must not perform a duty authorised by the license if the person does not hold a current medical certificate that is appropriate to the license.

That meant that on the day of the accident, the pilot should not have been performing the duties that were authorised by his license.

The helicopter was first registered in Australia on 3 May 2005 and was reported to have flown about 130 to 140 hours since its delivery flight to Yalda Downs on 1 August 2005. An examination of the helicopter's maintenance records found that the helicopter was certified for day VFR flight and equipped and maintained in accordance with existing regulations and approved procedures. The helicopter was not equipped for flight under the night VFR, nor was it installed with an Emergency Locator Transmitter (ELT)².

The helicopter's weight and centre of gravity were estimated to have been within the prescribed limits at the time of the occurrence.

It was reported that the pilot would have refuelled the helicopter to capacity from the aviation gasoline fuel source at Yalda Downs prior to departing for Border Downs earlier that day. A witness at Border Downs indicated that the pilot did not refuel the helicopter at that location. It was estimated that at the time of the accident, about 24 L of fuel remained on board the helicopter. That would have been sufficient for the remainder of the planned flight to Yalda Downs.

A Bureau of Meteorology (BoM) examination of the forecast weather and meteorological observations from the Tibooburra Automatic Weather Station³ indicated that there was no significant weather, no low-level cloud, and no reduction in visibility in the region of Tibooburra at the time of the occurrence. The investigation determined that the times of sunset, and of the end of civil twilight for the relevant locations along the planned west to east route included:

The pilot was reported to have accessed a private weather source via the internet prior to the departure from Border Downs. The available information from that source included the observed surface wind for a number of locations in the general vicinity of the flight and the weather forecast and times of sunrise and sunset for Broken Hill. Sunset for Broken Hill on the day of the occurrence was published by that source as 1809.

A witness at Border Downs reported the weather as being 'good', with a wind of about 10 to 15 kts from the west-south-west, and a cloud base of above 1,500 ft AGL. The weather at the accident site at the time of the accident was reported by witnesses to include: a light north-westerly wind; a 50% overcast layer of thin cloud, with a high base; good visibility; and no horizon. Witnesses reported that it was 'pretty dark, as in black'.

Examination of the NSW Police and other photographic evidence indicated a low angle of impact with the sand hill at a relatively high speed, which compromised the integrity of the helicopter's cockpit area. That was consistent with the reported 85 m wreckage trail and witness reports of the helicopter's approach towards the ground.

The damage to the helicopter's landing skids and engine mount frame was consistent with a slightly nose-down, right angle of bank at ground impact. One of the main rotor blades separated from the main rotor head at its hinge bolt attachment point, consistent with static overload as a result of the blade's impact with the ground. The damage to that main rotor blade confirmed that the main rotor was rotating at that time. The tail boom appeared to have failed in overload and separated from the main wreckage following the initial impact with the ground. The relatively minor torsional shear indications evident on the tail rotor driveshaft, and the nature of the damage to the tail rotor blades, indicated that the tail rotor had ceased rotating prior to its impact with the ground.

Based on the available information, there was no evidence that material failure or component malfunction had contributed to the development of the occurrence.

At the time of writing this report, the pilot's post mortem report was not available to the investigation team.

There was no report by the witnesses to the occurrence of an in-flight fire. The source of the post-impact fire was from fuel that had spilled from the ruptured helicopter fuel tanks. The ignition source of the fire could not be confirmed, but was most likely from the hot engine exhaust.

CAR 252A specified that a pilot in command of an aircraft that was not an exempted aircraft⁴ may only begin a flight if the aircraft either:

• was fitted with an approved and functioning ELT, or
• carried an approved and readily accessible portable ELT that was in working order.

The helicopter was not an exempted aircraft and it was reported that the pilot normally carried a portable ELT during flight. The survivor indicated that he had not observed a portable ELT in the helicopter prior to or during the occurrence flight, and the item was not identified by the NSW Police amongst the wreckage of the helicopter, or at the site of the accident. AusSAR⁵ reported that an emergency signal was not identified at or about the time of the accident.

The flight was within the central Australian mainland component of the Designated Remote Area that was promulgated in Appendix III to Civil Aviation Order 20.11. That required the carriage of sufficient survival equipment for sustaining life appropriate to the area being overflown, and either the submission of a SARTIME⁶ flight notification to Air Traffic Services (ATS) or for a pilot in command to leave a flight note with a responsible person. It was reported that the pilot and passenger carried sufficient clothing in case the decision was made to remain overnight at Border Downs. ATS records indicated that a SARTIME was not submitted to that agency, and a flight note was not left at either Border Downs or Yalda Downs for the occurrence flight. Witnesses at Yalda Downs indicated that the first confirmation that the pilot intended to return that night was via a radio call from the pilot at about 1900 to 1915, indicating that '[he] would be late [arriving at Yalda Downs]'.

The Aeronautical Information Publication (AIP) requires that:

Unless the pilot in command holds a Command Instrument Rating or night VFR (NGT VFR) rating and the aircraft is appropriately equipped for flight at night, a VFR flight must not depart from an aerodrome:

1. before first light or after last light; and
2. unless the ETA [Estimated Time of Arrival] is at least 10 minutes before last light after allowing for any required holding.

Last light was interpreted by the AIP to equate to the end of civil twilight ⁷. In addition, the AIP alerted pilots to the potential for the presence of cloud cover to the west of an aerodrome, and a number of other variables to adversely affect a flight arriving at its destination near the end of daylight. Sunset was highlighted as 'having no relevance when calculating daylight operating times for the VFR pilot.'

The AIP also placed altitude restrictions on the operation of an aircraft under the night VFR. That included that a pilot should not operate an aircraft under those rules at a height lower than the published lowest safe altitude (LSALT) for the route, or a height that was calculated in accordance with the requirements of the AIP, except under certain prescribed circumstances. Depending on the calculation methodology applied by a pilot, the LSALT for the route Border Downs to Yalda Downs was at least 2,020 ft above mean sea level (equivalent to about 1,500 ft AGL at Calindary).

The Approved Flight Manual for the helicopter included a number of Safety Notices that were relevant to the operation of the helicopter at night. Those notices included that:

• Flying a helicopter in obscured visibility due to fog, snow, low ceiling, or even dark night can be fatal.
• Loss of the pilot's outside visual references, even for a moment, can result in disorientation, wrong control inputs, and an uncontrolled crash.
• …[the pilot] loses control of the helicopter when he attempts to turn to regain visibility but is unable to complete the turn without visual references.
• [pilots should] be sure you NEVER fly at night unless you have clear weather with unlimited or very high ceilings and plenty of celestial or ground lights for reference.

1. A witness who heard, but did not observe the takeoff.
2. Crash-activated radio beacon that transmits an emergency signal that includes the position of a crashed aircraft.
3. The closest station to the site of the accident, being about 49 NM north-north-west of that location.
4. Exempted aircraft means high capacity regular public transport or charter aircraft, single seat or turbo-jet powered aircraft, or balloons, airships or gliders.
5. Australian Search and Rescue - in general terms, AusSAR coordinates the response to aviation SAR incidents across Australia.
6. The time nominated by a pilot for the initiation of Search and Rescue action if a report has not been received by the nominated unit.
7. Period at sunset when the sun's centre is between 0°50' and 6° below the horizon.

The helicopter with the pilot and one passenger onboard, was returning to Yalda Downs Station from Border Downs Station after last light. As it overflew Calindary Station homestead, which is approximately 46 km west of the intended destination, the helicopter was observed to gain height and conduct a right turn. The helicopter then descended and impacted the ground about 500 m from the homestead. The helicopter was destroyed by impact forces and the post-impact fire. The pilot was fatally injured and the passenger sustained critical injuries.

Examination of the aircraft wreckage and accident site indicated that the aircraft impacted terrain at a steep angle and at high speed. In addition, the investigation concluded that the engine was producing power at the time of the accident.

The recorded Air Traffic Services (ATS) radar data indicated that the autopilot was engaged prior to the aircraft entering a steep left descending turn. The abruptness of the turn and the high rate of descent indicated that the autopilot was no longer controlling the aircraft. The autopilot could be disconnected by either pressing the electric trim switch or manually overriding the controls. The pilot was familiar with the route being flown and would be unlikely to have deliberately diverted from the intended flightpath. There was no significant weather in the area at the time of the accident, so the pilot would not have had to alter his heading to maintain visual flight.

If the pilot had deliberately disconnected the autopilot and manoeuvred the aircraft, the resultant flight path would probably not have been as abrupt as the recorded ATS radar data indicated. Therefore, the autopilot was probably disconnected by the pilot making an unintentional control input.

The investigation was unable to determine the reason for the sudden control input, but the circumstances are consistent with pilot incapacitation. The pilot was the only occupant of the aircraft who could manipulate the controls with the autopilot disconnected. The passenger, due to the usual seating arrangements, would have been unable to render assistance to the pilot, or assumed control of the aircraft, prior to the accident, if the pilot had become incapacitated.

History of the flight

At about 0855 Eastern Standard Time¹ on 24 September 2005, a Raytheon Aircraft Company Beechcraft A-36 Bonanza, registered VH-BKM, took off from Murwillumbah, NSW, on a private flight to Coonabarabran, NSW, with one passenger, who was the pilot's wife, under the visual flight rules. The pilot had not submitted a flight plan or nominated a SARTIME² and there was no requirement to do so. The pilot and passenger regularly flew return flights from Coonabarabran to Murwillumbah in this aircraft.

The aircraft was subsequently reported to be missing on 28 September 2005, and a search was commenced. The wreckage of the aircraft was located on 29 September 2005. The aircraft had impacted a heavily timbered hill on a private property 'Millera', located approximately 35 km east of Tenterfield. The aircraft had been destroyed by impact forces and a post-impact fire (Figure 1), and both occupants were fatally injured.

Figure 1: View of impact crater looking north-west

Operational Information

The pilot was 71 years old and held both commercial and private pilot licences for aeroplanes and had a valid Class 2 medical certificate. He held a pilot's licence for over 50 years and had previously owned and operated an aerial agricultural business. He had a total aeronautical experience of approximately 13,000 flying hours.

The aircraft had been owned and operated by the pilot for the previous 14 years. Maintenance records indicated that the aircraft had a valid maintenance release which was issued on 27 January 2005 and was valid for 12 months. The aircraft maintenance release was unable to be located in the wreckage, however the estimated total time in service of the aircraft at the time of the accident was 3,231 hours. The engine had been rebuilt and fitted to the aircraft in April 1992.

The aircraft was fitted with a two-axis autopilot which included separate roll and pitch engagement, altitude hold and automatic and manual electronic pitch-trim. The autopilot could be disconnected by pressing down on an electric pitch-trim switch on the control wheel, or by manually overriding the controls. The aircraft was fitted with a single control wheel.

Prior to the flight to Murwillumbah the aircraft was refuelled at Coonabarabran, from a fuel bowser owned by the pilot. Witnesses reported that the aircraft had been refuelled to its maximum capacity. Fuel records for the fuel supplied to the bowser indicated that the fuel sample in the supply truck was clear and free of sediment. The local aero club had been supplied with 400 L of fuel from the pilot's bowser and had not reported any problems with the fuel.

Performance calculations were used to estimate the fuel burn from Coonabarabran to Murwillumbah and from Murwillumbah to the accident site. These calculations indicated that approximately 140 L of fuel would have been on-board the aircraft at the time of the accident. Discolouration of tree foliage at the accident site and the extent of the post-impact fire confirmed that there was fuel in the aircraft when the accident occurred. Weight and balance calculations showed that the aircraft was within centre of gravity limits for the final flight.

Information provided by the Bureau of Meteorology indicated that a low-pressure trough was present to the west of Tenterfield on the morning of the accident. The weather forecast and actual observations indicated that the flight was conducted under visual meteorological conditions. Witnesses reported clear weather in the vicinity of the accident site.

The pilot had not submitted a flight plan for the flight or contacted air traffic control for an area QNH³ and was not required to do so. The recorded Air Traffic Services (ATS) radar data indicated that the aircraft was operating on a transponder code of 1200^4.

A review of recorded radar data indicated that the aircraft had been maintaining a stable heading and altitude for most of the flight, which was consistent with the autopilot having been engaged.

The aircraft had then descended from a cruising altitude of about 6,300 ft above mean sea level (AMSL) to a final recorded altitude of about 3,800 ft AMSL at a rate of approximately 5,000 ft/ min. The accident occurred at an approximate elevation of 1,000 ft AMSL.

The recorded radar data of the aircraft's flight path was superimposed on a topographical chart that indicated that the aircraft had made a sudden left turn over the area of the accident site (Figure 2).

Figure 2: Radar plot of final segment of flight

There were no recorded radio transmissions from the aircraft prior to departure from Murwillumbah, or during the flight. The aircraft was fitted with a fixed emergency locator transmitter; however, it was destroyed at impact and was not capable of transmitting a distress signal.

Wreckage and impact information

The aircraft wreckage was fragmented and damage to the aircraft structure was consistent with a high-speed impact. There was no evidence of an in-flight breakup, birdstrike or in-flight fire prior to the accident and a technical examination of the engine and propeller indicated that they were producing power at the time of the accident.

Ground contact marks indicated that the aircraft impacted the ground in a left wing-low, nose-down attitude. Damage to the tree canopy in the vicinity of the impact crater indicated an impact angle of 72 degrees to the horizontal (Figure 3). The aircraft's direction of flight at the time of the accident was estimated to be 290 degrees Magnetic.

Figure 3: Tree canopy damage

Post-mortem medical examination was unable to determine if the pilot had experienced any incapacitation prior to the accident. The pilot's medical records indicated that he was taking regular medication to control blood pressure and that he recently had undergone a minor surgical procedure to remove skin cancers but there was no evidence that either had a bearing on the accident.

Witnesses reported that the passenger normally travelled in the second row of seats, which faced rearwards. The passenger would occupy the seat diagonally across from the pilot (Figure 4) and only communicate with the pilot occasionally during a flight. There was no evidence of the passenger having any aeronautical experience.

Figure 4: Seating configuration of aircraft

1. The 24-hour clock is used in this report to describe the local time of day, Eastern Standard Time (EST), as particular events occurred. Eastern Standard Time was Coordinated Universal Time (UTC) + 10 hours.
2. The time nominated by a pilot for the initiation of search and rescue action if a report has not been received by the nominated time.
3. QNH is the altimeter subscale barometric pressure setting to provide altimeter indication of altitude relative to mean sea level. Area QNH is representative of the QNH of any location within a particular area.
4. A transponder is a receiver/transmitter which will generate a reply signal upon proper interrogation of an air traffic control radar signal.

On the morning of 24 September 2005, a Raytheon Aircraft Company Beechcraft A-36 Bonanza, registered VH-BKM, was being flown by the owner pilot on a private flight from Murwillumbah, NSW, to Coonabarabran, NSW, with one passenger. The pilot had not submitted a flight plan or nominated a SARTIME and there was no requirement to do so.

The aircraft was reported to be missing on 28 September 2005, and a search was then commenced. The wreckage of the aircraft was located on 29 September 2005. The aircraft had impacted a heavily timbered hill on a private property 'Millera', located approximately 35 km east of Tenterfield. The aircraft had been destroyed by impact forces and a post-impact fire and both occupants were fatally injured. Witnesses reported clear weather in the vicinity of the accident site.

The recorded radar data indicated that the aircraft was maintaining a stable heading and altitude which was consistent with the autopilot having been engaged. The aircraft then descended from a cruising altitude of 6,500 ft above mean sea level (AMSL) to a final recorded altitude of 3,800 ft AMSL, at a rate of approximately 5000 ft/min.

The pilot was 71 years old and held both commercial and private pilot licenses for aeroplanes with a valid Class 2 medical. The maintenance records indicated that the aircraft had a valid maintenance release which was issued on 27 January 2005.

Weight and balance calculations showed that the aircraft was within centre of gravity limits for the final flight.  Discolouration of tree foliage at the accident site and the extent of the post-impact fire indicated that fuel was present when the accident occurred.

The accident is consistent with the pilot becoming incapacitated, the aircraft departing controlled flight and subsequently impacting terrain. The possible reasons for any incapacitation could not be determined.

The pilot was reported to have conducted a similar low-level manoeuvre to that which preceded the accident on several previous occasions. On that basis, the investigation team considered that it was unlikely that the passenger was at the controls of the aircraft at the time of the accident. The manoeuvre left little or no margin for error and required sound judgement and skill. Although the pilot may have possessed those skills, no evidence was found of his ever having undertaken the appropriate check to assess those skills and obtain approval to conduct low-level aerobatic manoeuvres.

Repetition of the manoeuvre over a period of time may have led to the pilot gaining a false sense of security and may have led to the pilot becoming complacent about the inherent dangers involved with such manoeuvres. The manoeuvre performed by the pilot earlier that day at another location was commenced from a 'high-speed' flypast. The associated energy would have allowed the aircraft to convert speed to height and climb higher and attain a greater altitude for recovery than the manoeuvre performed during the accident flight. That manoeuvre was commenced from a take-off roll that did not use the full runway length available. When combined with a tailwind component, it was unlikely that the aircraft attained adequate airspeed to safely complete the intended manoeuvre by the end of the strip. It was also possible that the pilot was unaware of the windshear or had not considered its affect on the aircraft's climb performance.

Although the aircraft appeared to have stopped spinning to the right just before impact, the pilot had insufficient height to avoid a collision with the ground. Had the stall warning been operating, it could have provided the pilot with an earlier indication of the stall condition and thus enabled him to initiate a recovery earlier in the development of the manoeuvre.

The affect of the pilot's medical condition on his judgement or decision-making could not be determined. However, some aspects of the pilot's behaviour were not consistent with compliance with rules and regulations or good airmanship. These included conducting low-level aerobatics without approval, ignoring concerns expressed by peers, operating with an unserviceable stall warning indicator and ignoring weight and balance limitations. Furthermore, the pilot flew the aircraft knowing that he was suffering from a medical condition that was being reviewed by the Civil Aviation Safety Authority (CASA) and having been advised by CASA that he was not to fly until the results of the review were known. Disregard for the rules governing the conduct of flight and the operation of the aircraft removed safety defences that were established to prevent this type of accident.

On 15 May 2005, at 1535 Central Standard Time, an American Champion Corporation Citabria 7GCAA aircraft registered VH-TUF, with a pilot and passenger, took off from Stonefield private airstrip in South Australia for a local private flight. Shortly after becoming airborne, the aircraft crashed. Both occupants were fatally injured. The aircraft was destroyed by impact forces and a post impact fire.

After start up, the pilot performed a turn on the ground of more than 360 degrees before taxying on the north-east strip. The aircraft engine was heard powering up on the strip into the north-east and shortly after became airborne. After becoming airborne, the aircraft was observed to remain approximately 10 feet above the strip, and remained at that height until the end of the strip. At about this point, the aircraft was observed to enter a near vertical climb. At an estimated height of 500 feet above ground level, the aircraft stalled in the vertical position, before entering a right hand spin. The aircraft completed one and a half turns in the spin before it appeared to recover. At the point where the aircraft appeared to have recovered from the spin, it impacted the ground.

The investigation determined that the aircraft on the accident flight was 20kg over maximum all up weight (MAUW). The increased weight would have the effect of increasing the stall speed of the aircraft, thereby reducing its performance. It was also determined that the pilot took off north-east with a quartering down wind component, and attempted a vertical climb with a wind gradient of approximately 30kt and at 500 feet from the south, above ground level. This wind gradient would have significant impact on the aerodynamic performance of the aircraft, and the pilot may not have achieved the height he intended before it stalled.

On 8 March 2005, the Gippsland Aeronautics Pty Ltd GA-8 aircraft, registered VH-FGN, was carrying emergency relief supplies from Muelaboh to Patek in Aceh Province, Indonesia, as part of the Tsunami relief effort. The aircraft occupants comprised the pilot and one passenger.

At about 1326 Eastern Daylight-saving Time on 7 March 2005, the pilot of a Cessna Aircraft Company 310R, registered VH-FIN, took off from runway 30 Right at Tamworth Airport, for Scone, NSW. Approximately 1 minute after becoming airborne, the pilot reported flight control difficulties. At about 1329, the aircraft impacted the ground in a cleared paddock about 7 km west-south-west of the airport. The pilot was fatally injured, and the aircraft was destroyed by the impact forces and post-impact fire.

Examination of the aircraft's mechanical flight control systems, autopilot and electric trim system did not reveal any evidence of pre-impact malfunction. Those results, however, were inconclusive due to the extensive impact and fire damage. A bent hand tool found in the wreckage was not implicated in the development of the accident.

A periodic maintenance inspection carried out in the days before the flight resulted in the rudder trim tab being set at the full right position and possibly aileron and elevator trim tabs being set at non-neutral positions prior to the flight. There were indications that the pilot was rushed and probably overlooked the rudder and aileron trim tab settings prior to take-off. The aircraft flight path reported by witnesses was found to be consistent with the effect of abnormal rudder and/or aileron trim tab settings.

The investigation found that aircraft operating checklists produced by aircraft operators did not always include the autopilot and electric trim procedures located in the supplements of aircraft operating handbooks/flight manuals. At the time of the accident, the training and guidance generally provided to pilots did not emphasise the management of flight control difficulties including autopilot and electric trim related difficulties.

Following the accident, the aircraft operator and the maintenance provider advised that they had reviewed and amended some procedures. The Civil Aviation Safety Authority advised that a Civil Aviation Advisory Publication titled Multi-engine Aeroplane Operations and Training will be issued by July 2007 and that three items have been forwarded to the Safety Promotion Branch for consideration/action.