Sequence of Events

At about 1000 EST, the pilot and passenger departed from the airstrip at Carrara where the helicopter is normally hangered. From information supplied by persons who knew the pilot, it appears likely that he flew to a remote section of the New England Ranges west of the Clarence River.

At about 1524 three people were mustering cattle just south of an 11,000-V powerline spanning the Clarence River. They saw a helicopter approach from the south and stopped to watch it fly out of sight to the north-west following the course of the river. Moments later, one of them heard the sound of a crash. Upon investigation they found the high-voltage powerline was down and saw parts of the helicopter in the river.

The investigation found that the helicopter had struck and severed the lowest of three high voltage wires spanning the river. The top surface of one main rotor blade had impacted the wire before the wire became entangled in the tail rotor. The evidence indicated that the helicopter started to break apart before impact with the water. The three-phase powerline had a span of 428 metres which drooped to 87 ft at its lowest point over the river. The powerline sloped from the western bank to a much lower bank east of the river. Both supports were obscured by trees when viewed from the south-east at low altitude. At the time of the accident the sun's azimuth was approximately 20 degrees west of the alignment of that particular reach of the river. The sun was elevated some 16-17 degrees above the horizon.

Evidence from persons in the aviation community who knew the pilot indicated that he had a love of low flying. The pilot was not approved by CASA (Civil Aviation Safety Authority) to conduct low flying operations.

The weather in the local area was fine with a clear sky and light winds.

Pathology tests revealed the pilot had a blood alcohol concentration of 0.098 g/100ml. Specialist medical opinion indicated that this concentration was most likely the result of alcohol consumption.

Significant factors

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

1. The pilot was flying the helicopter at low altitude.

2. The pilot was probably affected by alcohol.

3. The pilot apparently did not see the powerline in time to take adequate avoiding action.

Following a winch launch, the pilot soared the glider for some five minutes. On return to the circuit the glider was flown towards left base and was noted to be low for a normal circuit. Reports indicate that the glider may have then commenced a turn before entering a spin to the left. After two rotations of the spin the glider impacted the ground short of the threshold. No attempt at recovery from the spin was detected by witnesses.

The prevailing weather conditions were a light wind with 3 OKTAS of cumulus cloud above 6,000ft.

Members of the pilot's gliding club stated that the circuit entry flown was uncharacteristic of the pilot.

The Postmortem Examination did not reveal any identifiable cause for incapacity.

The reasons for the loss of control have not been determined.

1. FACTUAL INFORMATION

1.1 History of the flight

The pilot had planned to fly his own aircraft to Brisbane to attend an important business meeting. On the day of the flight a weather forecast was obtained by the pilot before his early morning departure from Longreach. The Area 40 forecast described a moist air mass which had engulfed south-eastern Queensland resulting in low stratus cloud, rain and fog over the eastern Darling Downs. A clearing change from the south-west was expected during the afternoon.

The aircraft was fitted with a GPS (Global Positioning System) which was unserviceable. Subsequently, the pilot borrowed a portable unit as an aid to navigation for this flight. He had planned to fly direct to Archerfield, the general aviation aerodrome for Brisbane. No flight plan was lodged with air traffic services for the VFR (visual flight rules) flight nor was there a need to do so.

In the Injune area the pilot noticed extensive cloud ahead along his chosen route and he decided to divert to Roma. During the subsequent descent the aircraft entered cloud at 9,000 ft and broke out at 7,000 ft. Following the landing the pilot was met by a local operator, who was a LAME (licenced aircraft maintenance engineer) and a pilot. The operator had extensive knowledge of operations in south-east Queensland. He was aware of the poor weather further east which he later confirmed by obtaining an actual weather observation from another pilot stationed at Toowoomba airport.  Over coffee he advised the pilot to delay his departure until the next day as an early morning start would still enable him to meet his business commitment. However, the pilot seemed inclined to continue with his original plan. He explained the importance of his business meeting in Brisbane, scheduled at 0900 the next day.

The pilot delayed his departure until 1240 leaving the local operator with the impression that he intended to follow the Warrego Highway to Brisbane. At about 1405, the aircraft, which was partially obscured by cloud, was sighted by a LAME as it flew to the south of Toowoomba airport. The aircraft was next observed by several witnesses, some of whom were pilots, as it flew over Toowoomba City at 150-200 ft AGL (above ground level), under a cloud base of 400-500 ft. It appeared to be at cruise speed and the sound of the engine supported this observation. The aircraft was flying due east and was seen to enter a fog bank in the vicinity of the Toowoomba Grammar School and then bank slightly to the left as it disappeared from view.

Next, the aircraft broke minor branches off the top of a 15 m high tree located on the crest of the Toowoomba Range which was enveloped in thick fog. The aircraft was in a shallow descent when it struck the lower trunk of a large tree and crashed through the roof of a house 325 m beyond and below the ridgeline. The aircraft exploded on impact partially demolishing the house and setting it on fire. The pilot received fatal injuries. The two occupants of the house escaped through windows. Both were injured with one person requiring hospitalisation.

1.2 Personnel information

1.2.1 Pilot in Command

The pilot was aged 51 years and had commenced flying training in 1979.  In 1983 he obtained a restricted private pilot licence which he upgraded to an unrestricted licence in 1990.  Over the 15 year period he accumulated 285 hours flying experience, 30 of which were on the Cessna 210 aircraft type. His medical status for the licence was valid until 16 June 1996. His last medical examination report was annotated with the requirement to wear spectacles whilst flying.

During his stopover at Roma, he confided to the local operator that he still was uncomfortable flying his aircraft and that he was not fully knowledgeable about its operation. The local operator observed that the pilot looked fatigued. The pilot admitted that he had retired to bed at 0230 that morning and had arisen at 0530 to prepare for the flight to Archerfield. He also said that he felt fatigued especially after his experience of descending through cloud which had unnerved him. He said that he had little instrument flying experience and did not have an instrument rating.

1.2.2 Previous 72 hours history

The pilot owned a hotel and was involved in running the business. On the night before the flight, he had had a maximum of three hours sleep. His previous recent history could not be established. The postmortem examination report indicated the presence of Paracetamol, a pain killer available without prescription.

1.3 Aircraft information

The aircraft was placed on the Australian Register on 8 January 1979. The present owner obtained the aircraft on 2 March 1995. The maintenance release was destroyed in the fire. A cursory inspection of the maintenance release by the LAME during its stopover at Roma indicated that the aircraft was due for a periodic maintenance inspection in 16 flight hours. Examination of the known flying activity of the aircraft reduced this period to 10 hours. There were no known outstanding maintenance defects.

1.4 Meteorological information

1.4.1 Introduction

The flight was to be operated under VFR from the departure aerodrome. The pilot was required to obtain the area forecasts (ARFORs) covering his route and the appropriate terminal area forecasts (TAFs). The pilot obtained ARFORs 40 and 41, but it is not known whether he obtained a TAF for his destination, Archerfield. ARFOR 40 covers a large area of south-east Queensland, including the eastern Darling Downs and the Brisbane area.

1.4.2 Area 40 forecast

The forecast valid from 0300 to 1800, gave an overview of scattered rain and showers clearing slowly from western parts after 0900. Forecast cloud consisted of broken stratus, base 700 ft, tops 3,000 ft, rain and showers. Also present was scattered cumulus, strato-cumulus, base 4,000 ft, tops 8,000 ft inland and alto-cumulus above 12,000 ft. The predicted visibility was 3,000 m in rain and showers.

The Archerfield TAF current from 0600 to 1800, forecast one OKTA (one-eighth cloud cover) stratus at 1,000 ft and 4 OKTA strato-cumulus at 2,500 ft with a deterioration to 5 OKTA stratus at 1,000 ft with visibility reduced to 4,000 m in rain. The Toowoomba TAF was similar with the cloud base 800 ft.

1.4.3 Weather conditions at Toowoomba

Actual weather observations by local pilots and other witnesses in the Toowoomba area indicated a cloud base sloping down to the east. The general cloud base at Toowoomba aerodrome was about 800 ft as forecast. It sloped to 400-500 ft over the city. A large fog bank enveloped the range area on the eastern boundary of the city until 1500 when the fog lifted to form low stratus. The Bureau of Meteorology observation at 1500 in the city reported complete cloud cover, rain with dry and wet bulb temperatures of 14 degrees Celsius.

1.5 Other information

1.5.1 A Safety Study of VFR Flight into Adverse Weather issued by the Transport Safety Board (TSB) of Canada published on 14 November 1990 found that:

• TSB data demonstrated a considerably higher accident rate for pilots with less than 400 flight hours.
• Business flying pilots were older than average (older than 40 years) and few held an instrument rating.
• They showed a tendency to fly in conditions which surpassed their personal ability or that of their aircraft.
• Visual restrictions in older pilots (50 years plus) lead to an increase in vertigo occurrences.
• Low time pilots had a strong tendency for poor in-flight decision making and often chose to fly into adverse weather.
• Occurrences showed inadequate planning, entering into flight operations beyond the pilot's ability and adopting improper procedures.
• Business pilots often made a conscious decision to continue flight despite the adverse weather conditions being encountered. Pressure to complete the flight was evident often from the pilot himself and this pressure took on a sufficiently high priority to jeopardise safety.

1.5.2 The Bureau's records show that on 1 May 1995 the pilot had been involved in conducting a VFR flight in IMC (instrument meteorology conditions) at Townsville. During descent to Townsville the pilot found himself in cloud and the services of the Townsville Approach Radar controller were required to vector the aircraft to a known clear area.

1.5.3 The visual flight rules state that the flight must be conducted in VMC (visual meteorological conditions). For flight outside controlled airspace and below 3,000 ft AMSL (above mean sea level), or 1,000 ft AGL (above ground level) whichever is the higher, the visibility must be 5,000 m or greater and the aircraft must remain clear of cloud.

2. ANALYSIS

2.1 Introduction

The investigation established that the aircraft was capable of normal operation at the time of impact. There was evidence to indicate that the performance of the pilot was affected by fatigue which may have adversely influenced his ability to carry out his task. Most of the aspects identified in the Canadian study of flight into adverse weather were present in this accident.

2.2 Examination of the aircraft

Information from witnesses who saw and heard the aircraft in the Toowoomba area said the engine sounded normal.

Metallurgical examination of the exhaust manifold confirmed the engine was operating at the time of impact. Inspection of the aircraft wreckage and documentation did not reveal any significant discrepancies which could have contributed to the accident. The immediate explosion on impact and the intensity of the fire which followed indicated that the fuel tanks contained a substantial amount of fuel when the aircraft crashed.

2.3 The weather

Witnesses were unanimous in describing thick fog over the Toowoomba Range which did not lift until about an hour after the crash. This was a clear indication that VMC did not exist at the time of the accident.

2.4 Conduct of the flight

It is clear from the pilot's comments that he was inexperienced and underconfident in operating his aircraft. Prior to the accident he admitted feeling fatigued and a witness remarked that he looked fatigued. While the pilot may have admitted feeling fatigued, one of the most dangerous aspects of performance degradation with sleep loss, is that a person is unlikely to be aware of the manner and extent of their deteriorating performance (Hawkins, 1987). Fatigue can result in a number of significant decreases in performance such as poor self-monitoring, increased susceptibility to distraction, lowered arousal and increased reaction time.

The pilot felt compelled to continue his flight to attend an important business meeting. He could have landed his aircraft at either Oakey or Toowoomba aerodromes and hired a vehicle to drive the remaining distance to Brisbane for his business meeting, which was not scheduled until 0900 the next day. One important aspect of acute fatigue is that the ability to make clear decisions is markedly reduced. Despite his previous encounter with cloud, the pilot continued the flight in non-VMC weather conditions.

2.5 The final flight path

The distance flown from entry into the fog bank to impact was approximately 850 m which would have been covered in about 10 to 12 seconds flying at a slow cruise. Considering the proximity of the terrain which the pilot must have been aware of, his anxiety and disorientation in the fog would have been significant. The aircraft's attitude at impact was nearly wings level and in a slight descent. This would suggest that the pilot maintained sufficient control to keep the aircraft nearly level from the time it entered fog to the point of impact. It is possible that the slight descent profile in the aircraft's attitude was a pilot control input in an attempt to regain visual contact with the ground.

3. CONCLUSIONS

3.1 Findings

1. The aircraft was serviceable and carried sufficient fuel for the intended flight.
2. The Area 40 Forecast indicated that a VFR flight to destination was unlikely to succeed.
3. Cloud in the Toowoomba Range area was at ground level.
4. The pilot did not have an instrument rating.
5. He was relatively inexperienced in total hours and on the aircraft type.
6. He was suffering from fatigue.
7. He seemed compelled to continue the flight to destination.
8. He had an important business meeting to attend in Brisbane the next morning.
9. He was flying under a low overcast when the aircraft entered fog.

3.2 Significant Factors

1. The pilot was suffering from fatigue.
2. The weather en route was not suitable for VFR flight.
3. The pilot had an important meeting to attend the following morning.
4. The pilot operated his aircraft in IMC. He was not rated for nor experienced in IMC operations.

It was reported that the rotorcraft took off and climbed to about 150 ft. It then entered what appeared to be shallow dive at full power. The descent continued until the rotorcraft collided with the ground. The wreckage was spread out over about 50 metres. It was reported that the pilot had modified the engine installation prior to the flight, and he may have recently changed the main rotor blades. The circumstances that led to the loss of control were not be determined.

The wreckage and pilot were found by the property owner. The circumstances are unknown.

The crew was conducting a practice locator/NDB approach to Alice Springs, at night, in clear moonless conditions. The approach involved a stepped descent in three stages using three navigation aids. The pilot in command had earlier briefed the co-pilot that the 'not below' altitude after the final approach fix for the approach (2,780 feet) would be used as 'the minimum' for their purposes.

The flight proceeded normally until the aircraft passed overhead the final approach fix when the pilot in command asked the co-pilot to set the 'minima' in the altitude alert selector. The co-pilot responded by calling and setting '2300 feet'. This altitude was the Category A/B aircraft minimum descent altitude as depicted on the Jeppesen chart for the approach. The minimum descent altitude for the Westwind, which is a Category C aircraft, was 3,100 feet. The 2,300 feet called by the co-pilot was acknowledged by the pilot in command, and the aircraft then descended to that altitude. Shortly after levelling at about 2,250 feet, the aircraft struck the top of the Ilparpa Range and was destroyed.

The crew had descended to the incorrect minimum descent altitude before reaching the appropriate sector of the approach.

The investigation revealed a number of factors relating to the performance of the crew. Also revealed were a number of pre-existing conditions which contributed to the actions of the crew. These ranged from crew experience and training to procedures and policies of the operator and regulator.

The report concludes with a number of safety recommendations.

The aircraft was being operated on a flight over the pilot's property to inspect bores. It had been airborne for about 90 minutes.

The pilot contacted his son, who was mustering sheep on the property, on a hand-held radio to advise that he was returning to the station airstrip to refuel.

About three minutes later the crashed aircraft was observed by the pilot's son who had not seen or heard the aircraft immediately before the accident. The aircraft had impacted the ground in a near-vertical nose-down attitude and the pattern of damage to the left wing indicated that the aircraft had been rotating to the left when it struck the ground.

The pilot, the sole occupant, had sustained fatal injuries.

An inspection of the aircraft did not reveal any evidence of pre-impact defects. The engine was running at impact; some flap was extended and there was evidence of post-impact fuel leakage.

The pilot had completed a biennial flight review (BFR) in December 1994 and was correctly licensed to carry out an aerial inspection flight.

The nature of the impact indicates that the pilot lost control of the aircraft and was unable to regain control prior to impact with the ground.

The reason for the apparent loss of control was not determined.

The aircraft had only recently been acquired, and the pilot had received instruction on its operating characteristics. He was also briefed on low altitude stalls, engine failures and mustering techniques, although this did not constitute a low flying/mustering endorsement.

On the day of the accident the pilot flew the aircraft from one property to another, where he assisted with some farm duties.  At about 1500 EST he departed to return to the original property, maintaining CB radio contact with his father for part of the flight. However, this radio contact was lost as the aircraft descended for a landing.

Later that evening, when there had been no further contact with the pilot, and he could not be found at the property, a search was instigated which went well into the night but failed to find him or the aircraft.  An aerial search of the area next morning found the burnt-out wreckage of the aircraft, with the pilot still inside, in low scrub, approximately 90 metres east of the north/south airstrip, and 400 metres south of its northern threshold.

Examination of the wreckage indicated that the aircraft probably had been flying in a westerly direction towards the airstrip when it impacted the ground in a steep nose down attitude, creating a crater, 10 - 15 cm deep in the sandy soil.  The wooden propeller had shattered, and sections of its blades were thrown up to 14 metres from the point of impact.  The battery had separated from its attachment at impact, probably causing sparks which ignited fuel from the ruptured right fuel tank. The resulting fire engulfed the aircraft, consuming all combustible items, including the airframe fabric covering, cabin trim, seat belt webbing and instrument panel.

The intense heat of the fire melted a large portion of the engine, distorted the wing leading edges, and softened the fuselage metal tubular frame, causing the rear fuselage section frame, being at a steep angle, to collapse.

Other than fire damage, the aircraft suffered only minor distortion to the cabin area and landing gear at impact.  The right side of the engine frame distorted and bent up, with the engine being pushed back only as far as the firewall.

The aircraft was last seen with the cabin doors fitted, but these had been removed after its return and left in the hangar where they were found after the accident.  The pilot then flew the aircraft again in this condition, possibly practicing some of the low flying skills he had recently been taught.

The day was fine with a light and variable wind, mainly from the south-west.  There were no power lines, or other high obstacles, such as trees, in the area with which the aircraft may have collided.  The aircraft was new and there were no indications that it was other than serviceable prior to the accident.  The pilot was reported as being healthy and in good spirits.

Even though the pilot had received injuries to his head and limbs, he had not been thrown violently forward in his seat, and the aircraft did not appear to have moved or bounced after its initial contact with the ground, suffering only minimal impact damage. This would indicate that the aircraft impacted the ground at a slow speed, possibly following a stall at a low height from which the pilot was unable to recover.

The throttle was found to be near the full forward (open) position, but bent downward, probably by exertion of the pilot’s hand at impact.  From the propeller damage, and throttle position, it would appear that the engine was delivering a considerable amount of power at the time of the accident, possibly as the pilot attempted a stall recovery.

Because of the condition of the aircraft due to fire damage, the lack of witnesses, and the absence of other evidence, the factors leading to the cause of the accident could not be positively determined.

Sequence of events

On the morning of 8 April, the pilot flew the aircraft from Archerfield to Gatton to practise aerobatics. That afternoon he carried out two flights during which he performed an aerobatic sequence known as a "free program", which is a sequence of manoeuvres designed by the pilot to meet certain criteria. The following morning, the pilot carried out a check flight with an instructor to obtain approval in accordance with Civil Aviation Regulation 155(3), to conduct aerobatics down to a minimum height of 1,500 ft above ground level. The minimum height for aerobatics is 3,000 ft above ground level unless this approval is obtained.

Early in the afternoon, the pilot commenced a flight to practise his "free program" again. The flight was observed from the ground by other pilots, one of whom was in radio communication with the pilot. On this occasion it was planned to critique the flight via the radio. The pilot on the ground, who was an experienced aerobatic pilot, stated that about halfway through the sequence he could see there was a problem. The aircraft had been inverted for 5 or 6 seconds after a half loop, before performing a half loop downwards and returning to upright flight. The observing pilot said that after reaching a horizontal attitude, the nose of the aircraft pitched up 40-60 degrees and the aircraft rolled to the right. He immediately queried the pilot as to what he was doing but received no response. The aircraft continued rolling slowly to the right and several more transmissions were made, but there was still no response. The aircraft then appeared to stabilise, and the pilot responded saying that he thought he might have blacked out, but that he was all right now. He then said that he thought he would land and have a rest for a while.

The landing appeared to be normal, and shortly afterwards the events of the flight were discussed with the pilot. The pilot said that he could remember the nose of the aircraft coming up to the horizon, but he did not remember anything after that until the aircraft was near the downwind leg of the circuit. A discussion was held on "G-LOC" (g-induced loss of consciousness) and its possible effects including disorientation. After further discussion the pilot decided that he would make another flight later that afternoon, as he did not appear to have suffered any aftereffects. A technique was then discussed which would reduce the g force during the manoeuvre and help prevent the situation from recurring during the sequence.

At about 1730 EST, the pilot took off to practice the "free program" sequence again. He was in radio communication with his brother, a highly experienced pilot and flying instructor. The pilot had said that he would increase the base height for the sequence as an added safety margin.  The sequence was commenced and proceeded normally and the manoeuvre which had previously caused the problem was performed with what appeared to be the suggested modifications. However, shortly after recovery to the straight and level attitude from the downward half-loop, the nose of the aircraft pitched rapidly to 10 degrees nose-up and the aircraft began to diverge slowly to the right with the nose continuing to rise slowly. The aircraft then commenced a continuous roll to the left. During this time, the ground observer made several unsuccessful attempts to contact the pilot by radio. The nose of the aircraft dropped, and the aircraft dived almost vertically into the ground from a height estimated by witnesses as 2,000-2,500 ft.

Wreckage examination

Examination of the wreckage did not reveal any defects or failures which may have been present before impact, and which could have contributed to the development of the accident.

The canopy had been previously broken when a radio detached from its mounting in the rear cockpit during aerobatics. Two parallel cracks extended laterally across the top of the canopy over the rear cockpit. A repair had been carried out by stitching the cracks with locking wire. The impact site and wreckage did not initially yield a representative quantity of Perspex (only about 20 per cent was found) and the site was then excavated.

Approximately 60 per cent by weight of the canopy Perspex was recovered from the impact crater, including the lockwire stitching with some Perspex still attached. The remainder of the canopy Perspex probably broke into fragments smaller than those recovered. A thorough ground and air search was carried out for Perspex under the flight path, but none was found. This evidence indicates that the canopy is unlikely to have failed in flight.

Impact information

Microscopic examination of both airspeed indicator faces revealed a pointer impact indicating 195 kts on one instrument. The aircraft impacted the ground vertically making a crater approximately 1.3 m deep. The impact forces were not survivable.

Medical

The pilot was assessed as medically fit for issue of a Class 2 medical certificate in December 1994 and appeared to be in good health on the day of the accident. Pathological examination showed evidence of coronary artery stenosis which could have affected the pilots g tolerance. However, medical opinion was that this could not be categorically stated to be the cause of a low g tolerance, or a contributing factor to the accident.

Research and analysis

From the available evidence it appears that the fatal flight was a repeat of the previous flight, except that on this occasion the pilot was unable to regain consciousness before the aircraft struck the ground. The aerobatic sequence up until the time of control loss was, in the opinion of witnesses, flown with more precision and was of a higher standard than on the previous flight. The manoeuvres were described as being tighter, and the pilot was probably generating more g than on the previous flight. He had been advised to reduce power during the manoeuvre that had previously caused the symptoms consistent with G-LOC, to enable the downward portion of the manoeuvre to be conducted at a slower speed and therefore reduced g. Witnesses said that a power reduction was heard during the inverted part of the manoeuvre, but the entry speed is not known.

A BASI Air Safety Research Report produced in February 1988, "The possibility of G-Induced loss of consciousness (G-LOC) during aerobatics in a light aircraft", stated that with sustained moderate rates of onset of g force, G-LOC is preceded by visual symptoms such as grey-out and then black-out (loss of vision). G-LOC is due to the reduced flow of blood to the brain when the magnitude of g in the vertical axis (Gz) passes beyond a particular value, the G-LOC threshold. Beyond this value, neurones fail to function in the absence of the oxygen replenishment provided by the normal blood flow and G-LOC occurs.

The report stated that with a rapid g onset (1g per second for more than 3 to 5 seconds) sudden loss of consciousness may occur without the prior visual warning symptoms. High performance aerobatic aircraft such as the Pitts S2 are quite capable of achieving rapid g applications, and rapid g onset is frequently experienced by competitive aerobatic pilots.

Centrifuge research has shown that there is a period of functional incapacitation following G-LOC lasting an average of 15 seconds. Full recovery may take 30 seconds or longer from the initiation of the manoeuvre that induces G-LOC. An aircraft descending vertically at an average speed of 120 kts will take approximately 15 seconds to reach the ground from 3,000 feet.

Gz tolerance is reduced by various factors such as fatigue, hypotension (low blood pressure), hypoglycaemia (low blood sugar), dehydration, and illness. The pilot was, by all accounts, in good health at the time of the accident, but it is not known what factors may have affected his g tolerance.

Conclusion

Findings

1. The pilot was correctly licenced and endorsed to carry out the flight.
2. The pilot probably experienced G-LOC on the flight previous to the accident flight and was subsequently advised on a means of avoiding a recurrence.
3. The accident flight was commenced some hours later for the purpose of the pilot practising the same manoeuvres as on the previous flight.
4. The aircraft was seen to go out of control at the same part of the sequence as on the previous flight.
5. The pilot did not answer repeated radio transmissions after the aircraft had gone out of control.
6. The pilot had a medical condition which may have reduced his tolerance to g.
7. There were no mechanical defects found which may have contributed to the development of the accident.

Significant factors

1. For reasons which could not be positively determined, but probably related to G-LOC, the pilot lost control of the aircraft.
2. The pilot did not regain control of the aircraft before it struck the ground.

The Bureau of Air Safety Investigation (BASI) released occurrence brief 9501019 on 2 February 1996. On 27 April 1999, following receipt of new information from the helicopter manufacturer concerning the identity of the part number of the fan fitted to KEB, a revised occurrence brief was issued by BASI.

The owner of KEB drew attention to a number of potential safety deficiencies in the maintenance and inspection of Kawasaki 47G3B-KH4 helicopter engine-cooling fans.

In response to the issues raised, and in recognition of the hazard to flight safety created by engine cooling-fan blade fracture, the Australian Transport Safety Bureau (formed on 1 July 1999, and which integrated the Bureau of Air Safety Investigation in a multi-modal agency) then undertook an analysis of the failure of Kawasaki 47G3B-KH4 engine cooling-fans. This analysis did not consider operational or piloting aspects, but was confined to the analysis of the cooling fan. As a result of technical analysis of this and other engine-cooling fan blade failures, the following recommendations are made:

R19990195

The Australian Transport Safety Bureau recommends that the Civil Aviation Safety Authority alert all aircraft maintenance engineers, especially those conducting non-destructive inspections, to the detrimental effects that may be created in critical components by the abrasion of surfaces during general cleaning or cleaning in preparation for non-destructive inspection.

R19990196

The Australian Transport Safety Bureau recommends that the Civil Aviation Safety Authority alert helicopter maintenance organisations and all aircraft maintenance engineers to the potentially detrimental effects of painting engine cooling fans.

R19990197

The Australian Transport Safety Bureau recommends that Kawasaki Heavy Industries clarify the bolt-tightening instructions contained in Service Bulletin 305 to establish if an allowance should be made for the frictional torque effects of self-locking nuts.

FACTUAL INFORMATION

The glider, flown by an Air Experience Instructor, was winch launched from the airstrip into the west. Wind conditions were almost calm, and the outside air temperature was about 23 degrees Celsius.  The initial climb was normal.  At about 300 ft above ground level (AGL) the cable broke at the winch end.  The pilot took recovery action and released the broken cable.  The recovery action appeared to be successful.  Although sufficient strip remained for a safe landing straight ahead, the pilot turned left onto what appeared to be a low and close downwind leg of a modified circuit.  The glider entered a spin off an attempted turn in the base/final area from about 200 ft.  It impacted the ground in a vertical, nose-down attitude.

Witnesses advised that the glider did not climb too steeply during the launch.  When the cable broke, club members expected the pilot to lower the nose and land ahead, as he had been observed to do successfully on previous occasions.  There was surprise when the glider turned and entered a modified circuit.  However, experienced glider pilots agreed that it was possible to have flown a left circuit and achieved a safe landing onto the strip into the west after a cable break at 300 ft.

The glider was being flown within its approved centre of gravity and weight limits, with the pilot occupying the front seat and a lightweight passenger in the back.

ANALYSIS

It is not known if the energy level of the glider was satisfactorily restored after the cable break. It is possible that the airspeed was low all the way around the modified circuit until it dissipated to the point where the glider entered a spin.  The IS28B2 will lose about 400 ft per turn in a spin and adopts a vertical, nose down attitude in the first half turn.

The broken winch cable was range two spring steel, as recommended by the Gliding Federation of Australia (GFA). The winch driver reported that the cable must have broken at a kink rather than at a previous join, as tends to happen, because the broken remains did not include a knot from a previous join.

The glider was subsequently inspected by an experienced GFA airworthiness inspector.  No fault was found which may have contributed to the accident.

CONCLUSIONS

Findings

1. The winch cable was range two spring steel, as recommended by the GFA.
2. The winch cable broke when the glider was at about 300 ft AGL.
3. The airstrip was long enough for the pilot to land safely straight ahead after the cable break.
4. The aircraft entered what appeared to be a close left circuit after the cable break.
5. The glider entered a spin from about 200 ft AGL off a low-level left turn in the base/final area.
6. The pilot was trained and experienced at handling winch cable breaks.
7. The glider was serviceable immediately prior to the accident.

Significant Factors

1. The pilot failed to maintain sufficient airspeed during the low-level left turn.
2. The glider entered a spin at a height insufficient to effect recovery.

SAFETY ACTION

Gliding Federation of Australia

The Lockhart accident was the third fatal accident to winch-launched gliders in the previous three months.  Since this accident, the GFA has issued Operations Directive 1/95 - 'Winch Failure Training' which re-emphasises the GFA requirement for 'live' launch failure training, the first priority to maintain safe airspeed, at least 1.5Vs (1.5 times the stall speed) and the importance of landing straight ahead after a cable break in preference to turning.

The GFA has issued Operations Directive 2/95 - 'Low Speed Loss of Control' because the common factor in the recent fatal glider accidents was that the pilots lost control of their gliders at too low a height to allow recovery. Directive 2/95 re-emphasises that pilots must be aware of the symptoms of an impending spin and that spin recovery is not achievable if the glider is too low.

The GFA has organised a series of Flight Safety Seminars to be held in VIC/TAS, NSW, QLD, SA/NT and WA in 1995.  These seminars are targeted at chief flying instructors, but other interested persons are invited to actively participate.  Launch failure training and low speed loss of control (stall and spin) training are amongst the topics for discussion during the seminars.

GFA RECOMMENDATIONS

The GFA has made the following recommendations to its members:

"As well as spin training in accordance with normal practice, particular attention is drawn to pages 36 and 37 Part 2 of the Instructor Handbook, Spin Awareness and Common Symptoms.  These sections highlight the practicalities of making a pilot aware that a glider is about to spin.  They are intended to supplement the training sequences, not replace them.  It is recommended that these pages are photocopied and placed in the club magazine and/or in a prominent place on the pie-cart or the clubhouse notice board.

One further tip may help. It takes a certain period of time for the mishandled turn to degenerate into a spin.  The time taken depends on the energy of the glider on turn entry and the degree of misuse of the rudder.  Although coordinated flying combined with safe speed near the ground is the only certain answer, an added element of safety when under 1000 ft agl may be provided by planning to limit changes of direction to 90 degrees or less. This will not eliminate the possibility of a spin but, combined with a minimum of 1.5Vs, will greatly reduce the likelihood of it occurring in the case of a pilot who, under stress, unwittingly uses excessive rudder, a surprisingly common error."