The operator briefed the pilot to fly the helicopter along the powerline from one construction camp to the next and pick up passengers for transportation to another location. The operator left the construction camp in a vehicle at about the same time as the helicopter departed and drove to the camp expecting to see the helicopter on the ground. He became concerned when the helicopter had not arrived at the camp. A short time later, a construction linesman came across the wreckage of the helicopter some 74 m west of the powerline and about 18 km south of its destination.

Examination of the wreckage indicated low power and low rotor RPM at ground impact. The final descent was vertical amongst small trees with the helicopter's attitude 20 - 30 degrees nose high and approximately 40 degrees of left bank.

There had been only minimal damage to the engine, and it was later run prior to a specialist strip inspection.  Neither the test run, nor the inspection revealed any abnormalities that would have affected the operation of the engine. Examination of the remainder of the wreckage did not reveal any faults that may have contributed to the occurrence.

The weather in the range area consisted of low cloud and rain over the ridges. It is possible that the pilot encountered problems with lack of visibility as he proceeded along the ridgeline following the route of the new powerline. However, the dynamics of the crash would indicate that there was no loss of control due to inadvertent flight into cloud or rain.  The throttle was found in the closed position and the helicopter had impacted the ground with a high rate of vertical descent with no appreciable forward speed.

The post-mortem examination report indicated that the pilot was suffering a degree of myocardial fibrosis and coronary atherosclerosis. The report concluded that these conditions could have contributed to the accident by way of pilot incapacitation.

The factors contributing to the accident could not be determined.

On Friday 11 June 1993, at about 1918 EST, Piper PA31-350 Navajo Chieftain aircraft, VH-NDU, while on a right base leg for a landing approach to runway 01 in conditions of low cloud and darkness, struck trees at a height of 275 feet above the elevation of the aerodrome at Young, New South Wales, and crashed. The aircraft, which was being operated as Monarch Airlines flight OB301 on a regular public transport service from Sydney to Young, was destroyed by impact forces and post-crash fire. All seven occupants, including the two pilots, suffered fatal injuries.

The investigation found that the circumstances of the accident were consistent with controlled flight into terrain. Descent below the minimum circling altitude without adequate visual reference was the culminating factor in a combination of local contributing factors and organisational failures. The local contributing factors included poor weather conditions, equipment deficiencies, inadequate procedures, inaccurate visual perception, and possible skill fatigue. Organisational failures were identified relating to the management of the airline by the company, and the regulation and licensing of its operations by the Civil Aviation Authority.

During the investigation a number of interim safety recommendations were issued by the Bureau. The recommendations and responses are summarised in Section 4 of this report.

The aircraft had been stored in a hangar/shed, in a partially dismantled state for about 4 months. The pilot assembled and rigged the aircraft with the help of a person not familiar with aviation, and without reference to any qualified person or documentation. The pilot then boarded the aircraft, started it, and taxied for take-off. The take-off appeared normal, and the aircraft turned 90 degrees to the right at the upwind end of the runway. During the climb, at about 300 feet above ground level, the aircraft was seen to adopt a steep right wing low attitude and enter a spiral descent to ground impact.

The pilot was rescued from the wreckage and taken to the hospital, where he later died. He was not wearing a helmet during the flight.

Inspection of the wreckage revealed a broken wooden plug in the wing warping rod, where it attaches to the forward part of the right wing. The remains of the plug were found partially withdrawn from the rod end and an inspection of the left wing warping rod revealed the wooden plug partially withdrawn from its rod end by an amount similar to that found in the right wing. Microscopic analysis of the broken plug showed that the plug had been broken prior to the ground impact and that its material, which did not meet the manufacturer's specifications, had also degraded after lengthy exposure to the environment.

The plug failure, alone, should not have resulted in the loss of control of the aircraft. The aircraft is controllable with an adjustment of the position of the controls to compensate for the loss of the warping rod.

No other defects were found in the aircraft which could have contributed to the loss of control and subsequent crash.

The pilot's logbook contained no reference to prior experience in flying the Scout aircraft and indicated that he was inexperienced in operating ultralight aircraft. Anecdotal evidence suggested that he had more total hours than recorded in the logbook and also had some flying experience in the Scout, about two years prior to the crash.

The pilot had been solo-checked eight months prior to the crash and his logbook indicated that he had flown, unsupervised, on many occasions since that flight check, in contravention of the Australian Ultralight Federation Operation Manual requirements.

The wind on the ground at the time of the take-off was westerly at about 5 knots and was likely to have been stronger above tree top level. As the pilot turned away from the take-off strip, he probably would have had a tailwind component.

It is probable that the wooden plug broke after take-off. The pilot lost control following the failure, either because of inexperience, or he was distracted by the failure and allowed the speed to decrease to the stall speed as the aircraft climbed. The rudder is normally used for primary roll control of the Scout and if the pilot had not been aware of this, he may have aggravated the situation by using other recovery techniques.

Safety Actions

The Bureau of Air Safety Investigation has made the following recommendations:

1.  That the Civil Aviation Authority, in consultation with the Australian Ultralight Federation;

i) Advise owners of Wheeler "Scout" Mk3 ultralight aircraft to examine the wing warping control attachments and replace any suspect parts, and ii) As a matter of urgency complete and distribute the AUF Technical Manual.

2. That the Civil Aviation Authority research the wearing of helmets in ultralight operations with the view to determining if regulation in this area is warranted.

3. That the Civil Aviation Authority;

i) Examine its procedures for surveillance of sport aviation groups to ensure that the standards required by the regulations are being met;

ii) Actively pursue breaches of regulations or operating procedures, and, in conjunction with the Australian Ultralight Federation,

iii) Maintain an ongoing education programme of all ultralight operators with regard to their privileges and responsibilities under the Civil Aviation Orders and the AUF Operations Manual.

The following Safety Advisory Notices have been sent to the Australian Ultralight Federation:

1. The Australian Ultralight Federation should consider reminding all ultralight operators of;

i) The dangers associated with substituting substandard parts in their aircraft, and, 

ii) The dangers associated with not maintaining their aircraft to manufacturers' specifications.

2. The Australian Ultralight Federation should emphasise the potential safety benefits in wearing helmets during ultralight operations.

At 2015 hours on 24 May 1993 PH-BFA, a Boeing 747-400 aircraft, was hearing touchdown on runway 07 at Sydney (Kingsford Smith) Airport, having received a clearance to land from air traffic control. At the same time, a Federal Airports Corporation safety vehicle, Car 9, was conducting a search for reported debris on a portion of taxiway 'A' near runway 07.

During the search, the vehicle crossed the taxi holding position markings and entered the 07 runway strip. The crew of PH-BFA observed this incursion and carried out a go-around manoeuvre from a low altitude. It was determined that the safety officer in Car 9 had inadvertently crossed the holding point as a result of not seeing the holding point lighting/markings provided at the intersection of taxiway 'A' and runway 07.

Prior to commencing the Night VFR (Visual Flight Rules) flight, the pilot obtained a pre-flight briefing by facsimile.  This briefing included the appropriate weather forecast for the intended route.

After departing Coolangatta, the pilot reported to Brisbane Flight Service that he intended climbing to 7,500 ft and that he would remain outside controlled airspace. About 22 minutes later a single radio transmission was received by Brisbane Flight Service.  The transmission, by a male voice, said 'I'm doing cartwheels'.  This voice was different from the voice that made the initial transmission from VH-IWJ to Flight Service.

Witnesses in the Evans Head area observed the aircraft flying towards the north-west at an estimated altitude of 1,000 ft above the ground.  They reported that it was flying erratically before commencing a looping manoeuvre.  At the top of that manoeuvre the aircraft appeared to lose all airspeed, then dive vertically into the ground.

The aircraft was extensively damaged by impact forces.  Inspection of the wreckage did not reveal any pre-existing faults that may have contributed to the occurrence.

Post-mortem examination of the pilot did not provide evidence sufficient to determine whether he had suffered from any form of incapacitation.

The weather forecast obtained by the pilot indicated that showers were expected along the route and that some low cloud would be associated with the showers.  Provided the pilot remained clear of the showers a flight under VFR should have been possible.  There is extensive ground lighting in the area from Coolangatta to Ballina but after that the ground lighting reduces as the settlements become more widely spread.  The moon was located in the western sky, but most witnesses reported that it was dark at the time they observed the aircraft and that there was cloud in the area. Consequently, the pilot may have been deprived of a visual horizon from time to time.

The pilot was reported to have been in current flying practice, having last flown at night on 28 February 1993.  He had held a Night VFR rating since 25 September 1987.

The available evidence is consistent with the pilot having lost control of the aircraft and being unable to regain control before it impacted the ground.

SIGNIFICANT FACTORS

The factors leading to an apparent loss of control of the aircraft could not be positively determined.

The aircraft took off from the strip near the homestead at about 0645 hours to conduct cattle spotting operations. At about 0930 hours, the pilot reported by radio that he had completed the spotting task and was directed by the property manager to fly to the western section of the property and check the status of three bores. When the manager arrived back at the homestead at about 1200 hours, he found that the aircraft had not returned. Search arrangements were initiated and the wreckage of the aircraft was later found approximately one kilometre from the second in the series of bores to be checked. There were no witnesses to the accident.

On-site investigation revealed that the aircraft had crashed on flat, open terrain while heading in a north-easterly direction. The aircraft initially contacted the ground with the left wingtip followed by the propeller 14 metres beyond this point. There was evidence of a flash fire at this location, and of the aircraft then cartwheeling, before coming to rest 60 metres from the initial impact point. The relationship between the wingtip ground impact mark and the propeller impact point suggested that, at initial impact, the aircraft was in a slightly nose down attitude and banked steeply to the left.

The aircraft was severely damaged by a combination of impact forces and post impact fire. Examination of the wreckage did not disclose any condition or fault which might have contributed to the accident, although fire damage precluded a complete examination of some components, particularly the instruments and controls in the cockpit area.

The weather in the area around the time of the accident was reported to have been fine and hot with a light and variable wind. There were no restrictions to visibility. Flying conditions as described by occupants of the search aircraft were good with only light turbulence.

The broader area over which the aircraft was operating was covered with lush knee-high grass. Advice from the Bureau of Meteorology indicated that the chances of a dust devil (willy-willy) forming in these conditions were very small. Dust devil formation usually required barren, very hot and very dry conditions. No dust devils were observed in the area during the on-site phase of the investigation.

Considerable bird activity was noted around bores on the property. However, no evidence of the aircraft having struck a bird was found, although the post-crash fire could have destroyed any bird remains which might have entered the cabin area.

The notepad apparently used by the pilot to record information on each bore was found along the wreckage trail. Writing in pencil on the notepad indicated that the pilot had inspected the first bore (D-15) and recorded his observations. Beneath this writing was an incomplete recording of information on the second bore (X-8). At the end of this writing was a pencil mark similar to that which might be expected if the writing platform or the pencil was bumped or disturbed.

Bore inspections were a regular aspect of the pilot's flying duties. Inspections involved flying over the bore and checking the amount of water in the holding tank along with the condition of the adjacent animal drinking trough. The task could be readily accomplished from a flying height of 500 feet above ground level.

There was no indication of any physiological or psychological condition which might have affected the pilot's ability to operate the aircraft. He had been flying in the area for some 14 months during which time he had conducted many bore inspection flights. The pilot completed a course in low flying in January 1993.

Factors

The factors which contributed to this accident could not be determined.

The helicopter had been hired by the pilot to take family members on scenic flights in the local area. It was observed operating at low level between Tacoma and the F3 freeway during the afternoon. During its fourth flight it was observed flying low over the F3 freeway on a southerly heading then make a rapid 180 degree turn onto a northerly heading which it maintained for a short time. The helicopter then turned to the east and descended into a shallow depression where it collided with high tension power lines some 47 feet above ground level.

The high tension power lines span a depression on the eastern side of the F3 freeway. The wires are suspended between poles which are masked by trees on their western sides and are hidden from view when approached from the west at low level. The wire spans blend with the background vegetation. As the helicopter was approaching the wires from the west at low altitude it is probable that the pilot did not see the wires in time to avoid collision. The reason why the pilot was operating at that height at the time of the accident was not determined.

Investigation did not reveal any mechanical deficiencies with the helicopter which may have contributed to the accident.

Significant Factors

• The helicopter was operating at a very low height.
• The high-tension power lines are difficult to see when approached from the west at low level.

The aircraft was conducting cotton spraying operations on a 61 hectare field. The pilot stated that he had completed numerous swath runs, using a human marker for guidance, when it became necessary to fly beneath power lines converging at the southern corner of the field. He then completed a pass under the power lines in a south easterly direction and carried out an extended procedure turn to facilitate the next pass under the wires. He said he could then see the marker moving off to the next swath position.

The aircraft was positioned to pass beneath the powerlines at a speed of about 100 knots with a power pole to the right and the marker to the left, and moving left. As the pilot passed the power pole he heard a loud thudding noise, associated with a left yaw. The pilot said that he thought at the time he had clipped the power pole, but as he regained control of the aircraft, he noticed the left wing was damaged. Shortly after, he noticed the marker lying in an irrigation ditch, near where she had been standing. The marker was killed as a result of being struck by the aircraft.

The pilot was mustering cattle. The helicopter's gross weight was estimated at 602 kilograms which was 20 kilograms below maximum allowable. The terrain was approximately 1000 feet above sea level and the outside air temperature was about 25 degrees Celsius.

The surviving passenger recalled that the helicopter was about 35 feet above ground level when he first heard the low rotor warning horn and saw a warning light on the instrument panel. There were trees ahead which were about 25 feet high. The pilot said "whoops", pulled up, nosed over and veered slightly left towards a gap in the trees. At the time the helicopter had very little forward airspeed. He subsequently described a weightless feeling which is consistent with the pilot having applied a large forward cyclic input to achieve the "nose over". He recalled that the pilot was "fighting" the cyclic control for a short time as the helicopter rolled to the right into a tree. The survivor also remembers leaves flying about but he has no recollection of a rotor blade hitting a limb.

Damage sustained by the helicopter indicated that the main rotor struck a tree limb and that one rotor blade was severed about one metre inboard from its tip. When the section of rotor was severed, the remaining rotor blade flapped up causing a severe mast bump which resulted in overload failure of the mast at the main rotor head. The main rotor assembly departed and the unsevered rotor blade impacted the first section of the tail boom immediately aft of the engine. The main rotor did not sever the tail boom or the tail rotor drive shaft or the tail rotor control tube. The tail rotor drive shaft within the tail boom was severed in torsional/bending overload when the boom separated probably as the helicopter impacted the tree and fell through its limbs.

The right side of the helicopter, in the area of the fuel tank to the pilot's upright seat cushion, was pushed inwards probably when the helicopter impacted the tree. The right side of the landing skid was severely deformed and broken. No such damage was found on the left skid. It is probable that, after the tree impact, the helicopter impacted the ground right side low and bounced on to its left side where it was found at rest. There was no post crash fire. Damage to the tail rotor assembly indicated that the tail rotor was still rotating but probably not being driven by the engine when the tail rotor blades impacted foliage.

The helicopter was found with both the drive belts off the pulleys associated with the drive system from the engine to the main gearbox. There was no evidence of previous damage or wear on the drive belts, the pulleys or bearings; nor has any fault been found with the clutch or free wheeling unit. However, marks were found on the inside opposing faces of the flexible coupling between the main gearbox output shaft and the tail rotor drive shaft, forward of the upper pulley assembly. This indicates that the upper pulley assembly had moved forward abruptly thereby misaligning the belts enough for them to jump off the pulleys. There is no known inflight manoeuvre which could compress the forward coupling to the extreme as found. However, a severe tree impact or ground impact could dislodge the upper pulley assembly enough to damage the coupling and cause the belts to come off. It is most likely that the drive belts came off after the initial tree strike by the main rotor and not before. Engineers have found no significant fault with the engine or airframe which might have contributed to the accident. A magnetic particle inspection of engine components proved that the engine had not suffered a significant overspeed.

Subsequent trials in a Robinson R22 helicopter were conducted by a very experienced flying instructor in conditions similar to the day of the accident. His helicopter successfully hovered out of ground effect at 35 feet above the ground with rotor revolutions per minute (RPM) as low as 96% at which time the low rotor RPM horn was audible and the low rotor warning light was illuminated. During a simulated engine failure from a low hover it was noted that the cyclic still responded normally with rotor RPM as low as 75%.

The survivor's description of the accident is consistent with the pilot having inadvertently achieved low rotor RPM, possibly losing height, and trying to recover while avoiding nearby trees. His description suggests that the "nosing over/bunting manoeuvre" managed to unload the main rotor to the extent that tail rotor thrust rolled the helicopter to the right. It is a known fact that a pilot may not be able to counteract this uncommanded roll to the right with left cyclic input. It is probable that an uncommanded roll to the right caused the helicopter to collide with a tree; this is consistent with the survivor's description of the helicopter being "pulled into the tree".

SIGNIFICANT FACTORS

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

1. The pilot inadvertently allowed the rotor RPM to decay.

2. During the attempted recovery from low rotor RPM, the pilot's flight control inputs induced an inflight manoeuvre which resulted in an uncommanded roll to the right.

3. The helicopter collided with a tree.

Pilot transmitted a Mayday call stating the aircraft engine had failed 10 miles NW Aurukun and that he was conducting a forced landing into trees. Nothing further was heard from the aircraft, and the burnt-out wreckage was found some hours later in a densely treed, inhospitable area 44 km north of Aurukun.

The investigation determined that the engine fuel mixture control cable end had become detached from the mixture control arm on the fuel control unit. This allowed the control arm to move to the 'idle cut-off' position, causing the engine to fail because of fuel starvation.