An unregistered single-seat Sapphire ultralight aircraft took off from the town airstrip at 1700 EST. The pilot had borrowed the aircraft from the owner who expected him to practise flying the aircraft in the vicinity of a private airstrip at the outskirts of the town. At 1720 the aircraft crashed within 2 km of the town airstrip and about 500 m from the private airstrip.

This aircraft was unique. The designer had built it during the developmental stage of the aircraft type. Since then, it had been significantly modified including being retrofitted with a 40 horsepower Rotax 447 two-stroke engine, mounted upright. This is in contrast to the current Sapphire model which has the same Rotax engine installed inverted. The engine mounts were modified to enable the engine to be installed upright, and a specially designed engine cowl had been fitted. The shape of the engine cowl may have affected the aerodynamics of the aircraft.

Even though the propeller reduction gearbox had been installed inverted, the propeller thrust line was slightly higher than in the current model. The higher thrust line may have caused handling differences compared with the current model. The aircraft was fitted with a larger diameter propeller which rotated at lower RPM than propellers installed on current Sapphire models due to different gearing in the reduction gearbox. Whether the thrust produced was the same as the current model is unknown.

This aircraft did not have flaps and was fitted with full-span ailerons. Later Sapphire models have flaps and half-span ailerons. According to the current manufacturer, the full-span ailerons would have had a significant effect on the tendency for spin entry if the pilot inadvertently used aileron, in lieu of rudder, in an attempt to counteract wing drop. The main wing was fully fibreglass covered and appeared to be the same size and shape as the current model. The aircraft was equipped with a vacuum-driven airspeed indicator (ASI) sourced from a small venturi mounted on the nose of the aircraft. The owner had previously tested this ASI in flight and noted that it indicated 35 kts at the stall. Current Sapphires are fitted with a standard pitot/static system and the stall occurs at 36 kts.

The owner stated that when he test flew the aircraft it maintained straight and level flight, hands and feet off the controls, at 65 kts indicated airspeed. However, the effect of any differences between the accident aircraft and the current-model Sapphire concerning tendency to spin, spin entry, the established spin, or spin recovery is unknown.

The owner and the pilot had only flown this modified version of the Sapphire. The owner had a total flying experience of 80 hours in ultralight aircraft, with about 8 hours recent flying experience in the modified Sapphire. He stated that he had discussed the attributes of his Sapphire with the pilot before allowing him to fly it.

Witnesses saw the right wing drop and the aircraft enter a spin at a height estimated to have been between 200 ft and 500 ft. They heard the engine continue to operate until ground impact. One witness stated that the aircraft entered the spin from straight and level flight and spun three times before impact. Another witness stated that the aircraft may have just commenced a slight climb to the right when the right wing dropped and spinning commenced.

At the time of the accident the temperature was about 10 degrees C, the wind was a north-westerly at about 5 kts, and visibility was good with no sun glare because of high cloud cover. Official last light was 11 minutes after the time of the accident. The surrounding terrain was an obstruction-free mud flat.

There was adequate fuel on board and examination of the airframe and the engine found no defects which may have contributed to the accident.

The aircraft's centre of gravity and gross weight at the time of the accident are unknown. The owner and the pilot were unaware of the aircraft's empty weight and centre of gravity prior to the accident flight. Despite this lack of knowledge, pilots had successfully flown the aircraft for about 10 hours since it was modified.

According to other Sapphire pilots, the aircraft type does not exhibit a pre-stall buffet which would warn the pilot of an imminent stall. The Sapphire is not fitted with a stall warning horn. The investigation found that the pilot was wearing large boots and that the very small rudder pedals were located in a confined area of the cockpit pod. This may have made rudder application difficult. Spin recovery was probably not achievable if spin entry was as low to the ground as reported.

The pilot regularly flew his privately owned Jeep ultralight aircraft. Compared with a Sapphire, the Jeep has high drag, a slower cruise speed and a much slower stall speed. The pilot's logbook contained no entries for past Sapphire flights. However, according to the aircraft owner, the pilot had flown this aircraft four times and had accrued about two hours in it before the accident. None of the pilot's logbook entries indicated spin recovery training.

Spinning is currently banned in ultralight aircraft. However, the Australian Ultralight Federation's pilot ground training theory syllabus includes stall and spin recovery procedures, and the inflight stall training syllabus includes recovery from wing drops.

The Sapphire is known to be more sensitive to fly than the Jeep or similar high drag ultralights. It stalls at a higher airspeed and has sensitive handling characteristics. In the stall, the Sapphire normally mushes and then starts oscillating, but it may drop a wing and enter a stable spin. To stop the spin, a pilot must apply standard spin recovery drill. The manufacturer likens Sapphire handling characteristics to a modern glider. He recommends that, before flying a Sapphire, pilots should experience three hours dual instructional flying, including full spin recovery, in a two-place glider, or undertake equivalent training in powered aircraft.

The modified Sapphire stalled and entered a spin at a low altitude from which recovery was not considered possible. The reason the aircraft entered a spin could not be determined.

SAFETY ACTION

On 14 July 1995, the Australian Ultralight Federation (AUF) issued an Operations Bulletin to all training schools requesting them to ensure that the flight training syllabus coverage of stalling is followed. During routine inspections of operators, the AUF is ensuring that this is done.

The Operations Bulletin also requested instructors to impress upon students the need to undergo additional training when upgrading to a higher-performance aircraft. The aircraft manufacturer recommends three hours dual instruction in a glider prior to upgrading to the Sapphire.

History of the flight

The aircraft was one of a group of powered hang gliders operating from a 900-m grass strip aligned east-west. The group had arrived at the strip the previous morning. That afternoon, the pilot flew the aircraft with a passenger on a cross-country flight. Earlier, the pilot took another passenger for a flight which included power-on and power-off stalls. The aircraft performed normally on both these flights.

The group camped at the strip overnight and planned an early morning flight. However, the departure was delayed by fog. The aircraft had been left assembled overnight standing in the open. As a result, the wing had been wetted by condensation to the extent that beads of water had formed. Although the wing was exposed to direct sunlight for about 30 minutes before take-off, it was reported to have still been wet, although not beaded, when the aircraft taxied for take-off.

Conditions were suitable for flight by about 0930 EST. The understanding was that each aircraft would take off towards the west and climb straight ahead to 1,500 ft above ground level before flying back across the strip in an easterly direction.

The accident aircraft was the first to take off. The wind was calm. The aircraft became airborne after a normal ground roll and climbed straight ahead. As the climb progressed, the aircraft followed the normal procedure of positioning about 80 ft above the right side of the strip. (This procedure is conducted so that, in the event of an engine failure, the aircraft is in a position to turn left to land back on the strip.)

At an estimated 200 ft above ground level, the aircraft levelled and entered an abrupt right turn to head approximately north. At the same time, the engine noise decreased but then increased again as the aircraft began a shallow climb, still heading north. A short time later, the aircraft rolled sharply right to at least 45 degrees of bank and adopted a steep nose-low attitude. It then spiralled to the ground, completing about one and one-quarter turns before impact. Members of the group were in radio contact with one another. No transmissions were heard from the pilot during the take-off and accident sequence.

Witnesses described the turn onto north and the subsequent turn as unusually abrupt. One witness, who flew a similar aircraft, considered that the turns would have required considerable physical effort from the pilot to manoeuvre the control bar towards his chest and to the left. The pilot was described as confident and reliable. There were no reports of him acting impulsively while flying.

Assuming the aircraft was carrying full fuel for the flight, the calculated take-off weight was 387 kg. Maximum allowable take-off weight for the aircraft was 401 kg.

Wreckage examination

Examination of the wreckage did not reveal any pre-existing fault which might have contributed to the accident. Failures to the mast and front mast brace were caused by overload. A strip examination of the engine did not reveal any fault which may have precluded normal operation. Examination of a section of engine exhaust pipe confirmed that the engine was operating at impact.

Pilot's experience

The pilot had completed a training course on weight-shift aircraft (commonly known as Trike aircraft) about 18 months before the accident. This training was conducted in accordance with the Trike Pilot Training Syllabus issued by the Hang Gliding Federation of Australia (HGFA) and approved by the (then) Civil Aviation Authority. The pilot did not receive any training in recovery from spiral dives; nor did the syllabus include a requirement for such training.

Medical and pathological information

The pilot was reported to have been in good health on the morning of the accident. The passenger was suffering from a cold. Pathological examination did not reveal any pre-existing condition of the pilot or the passenger which might have contributed to the accident.

Extracts from Pilot's Handbook

Section 2, paragraph 2.1 of the Pilot's Handbook for the aircraft lists airspeed limitations including:

"Stall speed 30.3 knots (IAS) max weight (power off)

23.0 knots (IAS) min weight".

Paragraph 2.4, Other Limitations, includes the following:

"The effect of light rain on the aircraft is slight. Heavy rain will cause the stall speed to rise to the point where it is possible to stall the aircraft without banking the wing. Under these circumstances the pilot input for control in the roll axis increases.... Do not use waterproofing agents on the wing as the consequent beading of water droplets can significantly increase the stall speed.

Aerobatic manoeuvres including whipstalls, stalled spiral descents and negative G manoeuvres are not permitted. It must be emphasised that a whipstall, spiral descent, or negative G manoeuvre can never be conducted safely. These manoeuvres put the aircraft outside the pilot's control and puts [sic] both the aircraft and its occupants in extreme danger."

Aircraft handling characteristics

As part of the investigation, the Civil Aviation Safety Authority (CASA) was approached for information on the handling qualities of weight shift controlled (Trike) aeroplanes, including the type involved in the accident. As a result, a CASA test pilot undertook a limited flight evaluation and held discussions with experienced Trike pilots.

A test was conducted in which the aircraft was stalled and no roll correction applied. The Trike entered a spiral dive during which roll divergence and nose-down pitch increased. Large out-of-trim forces were felt as speed increased. This caused difficulty in maintaining a nose-up longitudinal control position. Roll control remained effective throughout the manoeuvre although response rate to a given control input decreased as the spiral developed. Rapid recovery from the spiral was achieved by relaxing the nose-up pitch input and rolling wings level.

The test pilot reported that discussions he had with experienced pilots indicated that the spiral dive was not a widely recognised condition among Trike pilots. If a wing drop at the stall was not corrected early, recovery from the spiral dive to normal flight could result in an altitude loss of up to 90 m. The recognition of, and recovery from, a spiral dive was not included in the Trike Pilot Training Syllabus. It was suggested that such training be included in the syllabus.

The test pilot considered that the accident aircraft may have stalled and entered a spiral dive. A reflex action of the pilot may have been to attempt to raise the nose of the aircraft to recover from the dive. However, although this would have involved very high control forces, such an action by the pilot would have maintained the wing in a stalled condition, causing the spiral to continue.

A further flight characteristic of the Trike was that aircraft response to control inputs was slower as speed decreased, and aircraft weight increased.

ANALYSIS

The evidence indicates that the aircraft entered a spiral dive which continued to ground impact. Without specific training in this area, the pilot probably did not have the experience or knowledge to apply to recover from the unusual situation the aircraft was in. From the witness reports, it could not be determined if the height above ground of the aircraft when it entered the spiral dive was sufficient to allow recovery to normal flight.

The two abrupt turns made by the aircraft shortly after take-off cannot be readily explained. The aircraft did not follow the planned departure procedure and there was no radio transmission from the pilot to indicate any problem. Further, the pilot had no record of impulsive behaviour during flight.

It is possible that the pilot was attempting to fly a circuit to land back on the strip, although no reason for such action was established. The take-off weight of the aircraft meant that the stalling speed was high. This may have been increased further by the remaining moisture on the wing. It is conceivable, therefore, that the aircraft stalled during the turn which led to the spiral.

It is also possible that the change in engine noise heard by witnesses when the aircraft turned onto north influenced the pilot's actions. However, the engine noise quickly recovered and there was no evidence of any fault in the engine. The change in noise could be explained by the pilot's foot slipping on the throttle pedal control. These facts weigh against the engine being a factor.

The flight tests indicated that wing drop accompanying a stall could lead to a spiral dive if roll correction was not applied. Although the response rate of the aircraft to control inputs would have been reduced at the operating weight of the aircraft, the pilot had recent experience in flying the aircraft (including stalling) at this weight. The entry of the aircraft into the spiral dive is, therefore, not readily explainable.

CONCLUSIONS

Findings

1. For reasons which were not established, the aircraft entered a spiral dive.
2. The pilot had not received training in recognising and recovering from spiral dives.
3. The height above ground available for the pilot to recover from the spiral dive was probably marginal.

SAFETY ACTION

During the investigation, close contact was maintained with the HGFA. The Federation was also informed of the results of the flight evaluation undertaken by CASA. In response to this information, the Federation issued in March 1996 an amendment to the pilot training syllabus for weight-shift aircraft to include steep turns as a training unit. One of the objectives of the unit is that the student demonstrate skills required to counter the spiral tendency of the aircraft following a stall during a steep turn.

A revised HGFA Weight shift Microlight Flying Instructor's Manual was issued. This included the following:

"Spiral Dive Tendency

Demonstrate the tendency for the aircraft to begin to "spiral" when excessive pitch pressure is applied with a nose down attitude in a steep turn. Demonstrate that the aircraft will recover from the spiral due to its pitch and roll stability, though height loss can be substantial if excessive pitch pressure is held until the aircraft stalls. Demonstrate that reducing pitch pressure and levelling the wings will reduce height loss.

"Demonstrate that though the aircraft's tendency to diverge in roll is slow, it will increase if the aircraft is held in this spiral mode. Demonstrate that the aircraft can be readily rolled level by easing pitch pressure and applying weight shift.

"Ensure that the student is able to recognise the onset of the spiral tendency and is familiar with the recovery techniques".

FACTUAL INFORMATION

History of the flight

The Cessna 310R aircraft had been chartered to transport livestock buyers and had flown from Wagga to Longreach on the afternoon of 27 July 1995. The three passengers and the pilot stayed overnight. The following morning the pilot had breakfast at about 0645EST. He was apparently well rested and appeared to be in good health. At about 0800 the aircraft departed Longreach and was flown to a number of properties in the Muttaburra and Julia Creek areas. This entailed a total of some 3 hours flight time before returning to Longreach at about 1500, where the aircraft was refuelled to maximum capacity. The pilot also obtained appropriate weather forecasts and route data, and submitted flight details to the Brisbane briefing office for an instrument flight rules flight to Wagga via Cunnamulla, Bourke, and Condobolin, at a cruising altitude of 9,000 ft. The estimated flight time was 248 minutes.

The pilot reported taxiing at Longreach at 1535 and subsequently advised a departure time of 1537. Normal position reports were made throughout the flight. At 1900, as the aircraft approached Condobolin, the pilot requested, and received, a report of the actual weather conditions at Wagga. The report indicated the wind was light and variable, and that there were 4 octas of cloud at 2,000 ft and 5 octas of cloud at 3,000 ft, with visibility greater than 10 km, reduced in isolated rain showers.

The aircraft passed over Condobolin at 1914, maintaining 9,000 ft, estimating Wagga at 1954. The pilot was requested by Sydney Flight Information Service (FIS) to contact Melbourne FIS. This was carried out at 1919:30 when the pilot reported maintaining 9,000 ft. Melbourne FIS advised the pilot to expect entry to Wagga controlled airspace on descent to 6,000 ft, and to contact Wagga Tower at 25 NM. This was acknowledged by the pilot.

At 1943 the pilot advised Melbourne FIS that the aircraft was 40 NM from Wagga and leaving 9,500 ft on descent. Shortly after, at 1943:35, Melbourne FIS asked him to repeat his DME (distance measuring equipment) distance from Wagga, to which the pilot replied, "about 37 DME". That was the last recorded radio transmission from VH-MFK. At 1948:46, three short bursts of hash and one click were heard, lasting for about 5 seconds. The pilot subsequently failed to contact Wagga Tower as required. Communications checks by both Melbourne and Wagga failed to re-establish contact with the aircraft. Search-and-rescue procedures were initiated which resulted in the wreckage of the aircraft later being found 55 km NNW from Wagga Airport, in a cleared field, in lightly timbered, generally level country.

It was subsequently reported that the wife of the pilot had made a telephone call from her home at Narrandera to one of the passengers, as the aircraft approached Wagga. The passenger handed the mobile telephone to the pilot, who told his wife, "I am in big trouble, I've lost my gyros". He indicated he may have to divert to Narrandera but was informed that the weather was not good there, either. His wife said she would go down to the airport at Narrandera and call him back. After a brief farewell, the pilot terminated the call and some 10 seconds later his wife, who was monitoring the radio, heard him report at 37 DME.

A pilot flying from Broken Hill in a similar aircraft type had landed at Wagga some 20 minutes prior to the accident. He reported that, at his cruising altitude of 9,000 ft, he had generally been above cloud but had occasionally flown through the tops of larger build-ups. The night had been very dark and the only ground lights he had observed were from Leeton. There had been little turbulence apart from the "odd bump", and he had observed only light rime icing on the airframe at cruising altitude. This had rapidly dissipated during descent through 7,000 ft.

Some time after 2000 he was requested to assist in the search for the missing Cessna. After taking off from runway 23 at Wagga, he entered cloud at about 1,000 ft and flew out along the expected inbound track of the aircraft to a distance of about 35 NM, at an altitude of 4,000 ft. He had then searched the area between 35 NM and 25 NM for about 20 minutes. At no stage during the time he was in the search area did he see the ground or any other feature.

The wreckage of the aircraft was strewn over an area of some 250 m by 300 m in a pattern consistent with an in-flight, high-speed breakup, at a low height. Apart from the rudder tab, all structural components and flight controls were accounted for at the accident site, including a 0.5 square metre section of the left horizontal stabiliser lower skin, which was located some 450 m to the south-west of the main wreckage area. From the depth of the impact craters, and orientation of ejected earth, it was apparent that the wreckage had been travelling at high speed on impact, in a north-east direction. The disposition of the tail components indicated they had separated first in the break-up sequence. The aircraft had then disintegrated prior to ground impact. This was indicated by the wreckage scatter and divergent paths of heavier components. There was no evidence found to indicate the presence of any pre-existing structural deficiency prior to the accident. Both engines had suffered considerable impact damage but had probably been at a low power setting at the time of impact. This was consistent with damage observed to the propeller blades. Evidence was found to indicate that all four fuel tanks had contained fuel at the time of impact.

All four occupants had suffered multiple injuries in the accident. The extent of aircraft damage made the accident non-survivable. Each of the three passengers had been ejected from the aircraft before it struck the ground, as a result of massive structural disruption of the airframe. None of the passenger seatbelts found in the wreckage showed evidence of having been fastened at the time of impact.

During an in-flight telephone conversation about 3 minutes prior to the accident, the pilot had indicated that the gyroscopic flight instruments had failed. Both attitude indicators and the directional indicator were air-driven gyro types. The turn co-ordinator was electrically operated. A post-accident examination of both attitude indicators showed no evidence of rotational witness marks which would have been expected if the gyros had been rotating at impact. The directional indicator gyro casing did display a witness mark consistent with the gyro being stationary at impact. Although it could not be determined if the turn co-ordinator gyro had been rotating at the time of the occurrence, electrical power was maintained until aircraft break-up.

The aircraft was equipped with two vacuum pumps, one driven by each engine, to provide a vacuum source for the air-driven gyroscopic flight instruments. The right engine driven vacuum pump body was found on the ground in the area between the engines. The left engine driven vacuum pump was found complete, together with its drive coupling, in the crater of the main wreckage. No useful information was obtained from the remains of the right engine vacuum pump. The left engine vacuum pump was dismantled, and the internal vanes were found broken, possibly resulting in seizure of the pump and subsequent shearing of the drive coupling. Further investigation indicated that the engine had continued to operate after the drive coupling had sheared. When that event took place could not be determined. It is likely that the right vacuum pump drive had also sheared in flight; however, this could not be substantiated as the drive coupling was not recovered. An examination of the remaining vacuum system components found no evidence of any pre-existing defect.

The loss of vacuum to the air-driven gyroscopic flight instruments would have resulted in those instruments providing erroneous and misleading aircraft attitude and heading indications to the pilot. A search of the BASI database found that four occurrences of double vacuum pump failure in twin-engine aircraft had been reported in Australia during the past 10 years.

A similar search was made of records held by the National Transportation Safety Board (NTSB) of the United States of America. In the period 20 May 1983 to 1 March 1994, the NTSB investigated 29 accidents in which vacuum system failure and/or vacuum pump malfunction were contributing factors. One accident involved a twin-engine aircraft suffering a double vacuum-pump failure. The remaining 28 accidents involved single engine aircraft. Most accidents resulted from the pilot losing control of the aircraft in instrument meteorological conditions (IMC), following the loss of reliable indications from the air driven gyroscopic flight instruments.

ANALYSIS

The circumstances of this accident were consistent with a loss of control by the pilot during flight at night in IMC, which resulted in the structural limitations of the aircraft being exceeded.

The pilot was reported to have told his wife, during an inflight telephone conversation that "I've lost my gyros". This was indicative of a failure of the vacuum-driven gyroscopic flight instruments. Examination of both attitude indicators and the directional indicator showed their respective gyros were not rotating at the time of impact. An examination of the vacuum system found that, with the exception of the vacuum pumps, it had been capable of normal operation immediately prior to impact. Only the left vacuum pump was recovered, and was found to have failed prior to impact. From the evidence available, it is concluded that the right vacuum pump had also failed some time prior to impact.

Despite extensive enquiries, no evidence was found to indicate the vacuum system was other than capable of normal operation when the aircraft departed Longreach for Wagga. There was no evidence found of any event during the subsequent flight which could have indicated when, or in what sequence, the vacuum pumps failed. With the benefit of hindsight, the only indication of a possible problem was the unexplained change in cruising altitude from 9,000 ft to 9,500 ft after the aircraft had passed over Condobolin. This could suggest that the pilot had already lost the use of his gyroscopic flight instruments and was endeavouring to remain above cloud until ready to commence descent into Wagga. At no stage did the pilot indicate to FIS that he was experiencing problems.

The pilot was faced with a relatively straight descent into Wagga, utilising the remaining flight instruments. Those instruments were, by their very nature, subject to various errors resulting from manoeuvres and other accelerations during flight. Such errors would be manifested as false, short-term indications. In normal instrument flying, those false indications could be resolved by reference to the gyroscopically stabilised attitude indicators or directional indicators.

Instrument-rated pilots are required to demonstrate proficiency in controlling their aircraft in normal flight manoeuvres and unusual attitude recovery techniques, with sole reference to the remaining flight instruments following a simulated failure of the primary attitude indicator. Normally, the failure is simulated by covering the instrument face. However, the person conducting the proficiency check is not permitted to simulate a failure of the primary attitude indicator in IMC or at night, unless that person has in view another serviceable attitude indicator. Furthermore, if a standby attitude indicator, powered from a different source to that of the primary attitude indicator, is available, then the person demonstrating proficiency is permitted to refer to the standby attitude indicator. There was no provision for the fitment of a standby attitude indicator to this class of aircraft.

In this occurrence the pilot was faced with the failure of both attitude indicators, as well as the directional indicator. Moreover, there was extensive cloud and rain on the intended descent track, the night was very dark, and there would have been almost no external visual cues to assist the spatial orientation of the pilot. In addition, the descent was at the end of a long and probably tiring day. Unfortunately, as distinct from a proficiency check, it is unlikely that the attitude and directional indicators were covered. In the course of his normal instrument scan, the pilot could not have avoided seeing erroneous attitude and heading indications from the failed instruments. His instrument scan pattern would have been developed over many thousands of flying hours, with great reliance on the attitude indicator. Such a habit could not easily have been modified to ignore the very powerful stimuli from the now unreliable attitude indicator. As a result, it is considered that the pilot, despite his very considerable experience, encountered circumstances that were beyond his capabilities. During the descent in IMC the pilot became spatially disorientated, leading to the loss of aircraft control, and in-flight break up.

SIGNIFICANT FACTORS

1. The probable in-flight failure of both engine-driven vacuum pumps, resulting in a loss of supply to the air-driven gyroscopic flight instruments.
2. Unreliable aircraft attitude and directional indications from the air driven gyroscopic flight instruments, which adversely affected the ability of the pilot in command to safely control the aircraft by sole reference to the remaining flight instruments.
3. Adverse meteorological conditions which prevented the pilot in command continuing the flight by visual reference to the natural horizon or other external features, following the loss of credible indications from the air-driven gyroscopic flight instruments.

SAFETY ACTION

As a result of the investigation into this occurrence, the Bureau of Air Safety Investigation issued interim recommendation IR950059 to the Civil Aviation Safety Authority (CASA) on 21 October 1996:

"The Bureau of Air Safety Investigation recommends that the Civil Aviation Safety Authority ensure appropriate maintenance policies are developed for all general aviation aircraft pneumatic vacuum system components".

The CASA response received on 13 February 1997 stated:

"I refer to your BASI Interim Recommendation IR960059 concerning the accident involving Cessna 310R, VH-MFK on 28 July 1995. The following comments are forwarded for your consideration.

"Upon receipt of this Interim Recommendation, CASA was alerted that maintenance requirements for pneumatic check valves had been introduced by Airborne Air and Fuel Products.

"An article is being prepared for inclusion in Flight Safety Australia informing all Certificate of Registration holders that periodic testing of specific vacuum components is recommended by the component manufacturer.

"An Airworthiness Advisory Circular will be issued to inform operators that failure to carry out periodic testing could result in unreliable indications or loss of aircraft flight instruments during IFR flight. This AAC will recommend that functional testing of the vacuum and pressure valves be included in the aircraft maintenance schedule."

Response status: CLOSED - ACCCEPTED

In addition, the Bureau issued safety advisory notice SAN960145 to the Civil Aviation Safety Authority on 13 February 1997:

"The Bureau of Air Safety Investigation advises the Civil Aviation Safety Authority of the availability of standby and alternative power sources for air driven gyroscopic flight instruments used in commercial IFR operations. An example of such a standby attitude reference system is the SVS III manufactured by Precise Flight Inc. This system utilises engine manifold pressure as a standby power source.

"The Authority should review the requirements for attitude indicators and examine the availability of alternative power sources. Also, during instrument ratings and renewals, pilots should be warned of the distractions caused by erroneous attitude indications and be encouraged to cover these instruments in the event of a failure."

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.