Collision with terrain

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 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.

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."

Factual Information

The pilot took off from Frogs Hollow Airfield in an amateur-built Skybolt biplane to carry out aerobatic routines. Witnesses advised that the aircraft climbed to approximately 3,000 ft above the airfield and commenced manoeuvres that included stall turns, one and two turn spins, a flick roll and loops. The pilot then carried out one turn through 360 degrees rolling the aircraft about its longitudinal axis during the turn. The pilot then flew an inverted 360-degree turn. After a pause, he climbed vertically, carried out either a stall turn or wingover and entered an 'erect' or upright spin. After one turn of the spin, the aircraft's attitude was seen to change from 'erect' to inverted.

Witnesses advised that as the aircraft descended, the spin may have changed in direction and as it got closer to the ground, the nose began to drop. At about 1,000 ft above ground level the aircraft was observed to be spinning to the right. The rate of rotation began to decrease, with the nose dropping through the vertical.  The aircraft then entered an erect spiral dive from which it was recovering when it impacted the ground and caught fire. The impact was not survivable.

The wreckage and wreckage trail indicated that at impact, the aircraft was approximately 40 degrees nose down, right wing low, rotating to the right, with some forward momentum. This is consistent with witness evidence that indicated that the aircraft was probably in the early stages of recovery from a spiral dive.

The engine noise was reported to be normal until immediately prior to impact when power was removed, re-applied, then removed again. Examination of the wreckage did not disclose any evidence of pre-impact distress with the engine, the airframe or systems.

The weather was fine, with scattered high cloud, and was not considered to be a factor in the accident.

The aircraft was properly certificated, had been properly maintained and serviced and had a valid maintenance release.

The aircraft had been refuelled with sufficient fuel for the flight and was correctly loaded with respect to its centre of gravity. The pilot had carried out a pre-flight inspection of the aircraft during which he had set the altimeter to record height above the airfield, known as QFE.

The pilot's licence and medical certificate were valid.

The pilot commenced flying in 1959 and over the next 35 years had flown 722 hours. He was reported to have been a competent, self-taught aerobatic pilot. There was no record of the pilot receiving formal aerobatic training except for a brief period of instruction in spin recovery when he was endorsed on the Skybolt. The pilot's licence did not have an endorsement permitting him to conduct low-level aerobatic manoeuvres below 3,000 ft.  He had not been a member of the Australian Aerobatic Club.

He had flown 83 flights totalling some 60 hours in the Skybolt in the three years that it had been based at Frogs Hollow. Most of that flying had been in the first year when he flew 47 flights. In the second year he flew 22 flights, and in the year prior to the accident, 14 flights.  He flew most weekends and regularly flew a variety of single-engine aircraft that were based on the field. The majority of his Skybolt flights averaged approximately 30 minutes duration and involved essentially the same aerobatic routine as carried out prior to the accident, with the exception of the inverted spin.

The pilot had been observed to carry out a small number of inverted spins, but these had always been commenced at approximately 6,000 ft above ground level. Witnesses advised that on these occasions the aircraft was seen to generate high rates of descent and rotation and took an estimated 2,000 ft to enter a nose-down spin and subsequently recover to level flight. The pilot had not been observed to attempt an inverted spin from the 3,000 ft height from where he normally commenced his aerobatic routines. The last time he was observed to do an inverted spin was six months prior to the accident.

The Skybolt is described as an easy to fly, docile aircraft. The owner /builder of another Skybolt aircraft advised that he recovered instantly to horizontal flight from an inadvertent inverted spin when he closed the throttle, let go of all controls and then pushed on the anti-spin rudder. The aircraft flicked upright, and he was able to fly out of the manoeuvre.

However, even though they are built to the same plans, there are variations between aircraft. Each is built by a different builder and, being a biplane, is more subject to the effects of rigging tolerances than a conventional aircraft. When it was new, the aircraft was test flown to a more simplified procedure than that used for production aircraft manufactured to Federal Aviation Regulation 23 (FAR23). Therefore, there is little available data in regard to this particular Skybolt's handling characteristics, nor is there any documented comparison of this particular aircraft against others built in Australia.

Prior to the accident flight the pilot flew with a colleague to a neighbouring airstrip. They walked the length of the sloping strip and the pilot was observed to be breathing heavily and appeared to be unfit.  The colleague advised that this was the first time that he had observed the pilot to be other than fit and well.

Subsequent enquires found that the pilot had suffered from mild hypertension, for which he was reported to be taking Diazide or Renetic tablets, and that he was a mild hay fever sufferer. The post-mortem examination found no evidence of possible chest infection, but did disclose fibrous changes throughout the lungs that may have been due to pulmonary fibrosis, the causes of which are unknown.

As a condition of his licence, the pilot was required to wear glasses at all times while flying but was known to wear them selectively. He was not observed to be wearing them for this flight, nor were his glasses located in the wreckage.

Analysis

The pilot may have knowingly placed the aircraft into an inverted spin, or he may have suffered disorientation from 'G' induced loss of consciousness, otherwise known as G-LOC. The investigation was not able to positively determine if either of these scenarios had occurred.

G-LOC may have been induced during the pull up prior to the stall turn or wing over manoeuvre that preceded the inverted spin. If the pull up induced G-LOC, the pilot would have had to remain fully conscious at least to the point where full rudder was applied to induce the stall turn or wing over.  The subsequent changes to the aircraft's state may have occurred due to the pilot being disoriented and confused following a G-LOC episode.

However, the Skybolt aircraft has the reputation of being an easy aircraft to fly and the pilot was known to have successfully flown inverted spins in this aircraft. Witnesses to the flight did not describe the sequence to have been other than normal, except that the inverted spin was commenced at a lower height than before, and the recovery was not successful. Accordingly, it is possible that the pilot knowingly placed and held the aircraft in an inverted spin, intending to recover by allowing the nose to drop through the vertical until the aircraft was in an erect spiral dive, consistent with his previous routines.

The change in power during the final seconds of flight was most probably as a result of the pilot realising that he was too low and that an impact was inevitable. This realisation could have occurred regardless of whether the pilot had deliberately flown into the inverted spin, or due to G-LOC induced confusion.

The pilot may have been unwell on the day.  However, he had continued flying and obviously did not consider his symptoms to be enough to stop him performing the planned aerobatic sequences.

It is conceivable that the perceived lack of fitness may have increased his susceptibility to G-LOC. However, the medications he was taking for mild hypertension and mild asthma are not considered significant.

It is not known why the pilot did not wear his glasses, nor is known what effect the lack of glasses had on the pilot's ability to observe and react to the indications of attitude and altitude that were available to him.

The pilot had flown the Skybolt for only 14 flights, totalling less than 7 hours in the past year. This low level of currency would not be considered sufficient to maintain aerobatic competency, especially in light of the technically and physically demanding routines being attempted.

The pilot had not undertaken any formal instruction in aerobatic flying. Civil Aviation Regulations in force at the time of the accident required that acrobatic manoeuvres be completed 3,000 ft above the terrain. It is not known why the pilot commenced his manoeuvre at a height at which he should have been completing his recovery to level flight.

Conclusions

Findings

1. The aircraft was properly certificated and was serviceable.
2. The pilot held a valid licence and medical certificate, but he was not endorsed to conduct acrobatic manoeuvres below 3,000 ft.
3. Formal instruction in aerobatic flying had not been undertaken by the pilot.
4. The pilot had very low total and recent experience on the Skybolt aircraft.
5. The aircraft entered an inverted spin. The reason why this occurred was not determined.
6. The recovery procedure employed by the pilot did not ensure a rapid recovery to level flight.
7. The aircraft flew into the ground before recovery was effected.

Significant factors

1. The aircraft entered an inverted spin at a low height.
2. The pilot did not apply timely and effective recovery actions.

Sequence of events

The pilot received an endorsement on the MU2 after completing 3.4 hours on the aircraft type with the operator's check-and-training pilot. The operator's policy was that before being cleared to operate as pilot in command on company MU2 aircraft, pilots were required to accumulate 150 hours in command under supervision (ICUS) on the aircraft type. Company records indicated the pilot had completed this flying.

On the evening of 19 December 1994 the company check-and-training pilot gave the pilot a 45-minute check flight. Following this flight the pilot went on a final route check flight with a senior company training captain, from Bankstown to Melbourne and back to Sydney. These three flights were all conducted in VH-IAM. No instrument landing system (ILS) approaches were undertaken on these flights. After the return to Sydney the pilot was assessed as suitable to act as pilot in command on company MU2 aircraft.

Early on the morning of 20 December 1994 the pilot flew VH-IAM from Sydney to Melbourne International airport on his first company flight as pilot in command. On the approach into Melbourne there were three octas of cloud at 600 ft, three octas at 1,000 ft and an ILS approach was required. After landing at 0410 ESuT he rested at a nearby motel. Following this rest period, the pilot spent the afternoon with a fellow pilot. The only problem he mentioned with VH-IAM was that it did not have a serviceable distance measuring equipment (DME) unit.

Early in the evening of 20 December 1994 a flight plan was submitted for an instrument flight rules (IFR) flight to Sydney, departing Melbourne at 1930, and from Sydney to Melbourne, departing Sydney at 2230. The aircraft did not depart Melbourne until 2215. The ILS for runway 34 left at Sydney was out of service. Due to cloud at 800 feet a runway 34 left VOR/DME approach was flown.

The runway 34 left VOR/DME approach involves a progressive descent to specific altitudes at specific DME distances, but VH-IAM did not have a serviceable DME. The controller offered to keep the pilot advised of the aircraft's distance by radar to facilitate the approach. This offer was accepted. During the approach, the aircraft was noted on radar to descend to 1,000 ft when it should still have been at 1,900 ft. The pilot was advised, and the aircraft was noted to climb back to 1,500 ft, still below the required 1,900 ft. The aircraft landed without any further problems.

The aircraft departed Sydney for Melbourne International airport at 0130 on 21 December 1994. En-route cruise was conducted at flight level 140. Melbourne Automatic Terminal Information Service (ATIS) indicated a cloud base of 200 feet for the aircraft's arrival and runway 27 with ILS approaches, was in use. Air Traffic Control advised the pilot of VH-UZB, another company MU2 that was also en-route from Sydney to Melbourne, and the pilot of VH-IAM while approaching the Melbourne area, that the cloud base was at the ILS minimum and that the previous two aircraft landed off their approaches.

VH-UZB was slightly ahead of VH-IAM and made a 27 ILS approach and landed. In response to an inquiry from the Tower controller the pilot of VH-UZB then advised that the visibility below the cloud base was 'not too bad'. This information was relayed by the Tower controller to the pilot of VH-IAM, who was also making a 27 ILS approach about five minutes after VH-UZB. The pilot acknowledged receipt of the information and was given a landing clearance at 0322. At 0324 the Approach controller contacted the Tower controller, who had been communicating with the aircraft on a different frequency and advised that the aircraft had faded from his radar screen.

Transmissions to VH-IAM remained unanswered and search-and-rescue procedures commenced. Nothing could be seen of the aircraft from the tower. A ground search was commenced but was hampered by the darkness and reduced visibility. The terrain to the east of runway 27 threshold, in Gellibrand Hill Park, was rough, undulating and timbered. At 0407 the wreckage was found by a police officer. Due to the darkness and poor visibility, the policeman could not accurately establish his position.  It took approximately another 15-20 minutes before a fire vehicle could reach the scene of the burning aircraft. The fire was then extinguished.

Wreckage examination

The aircraft had struck the ground on a descent path of about three degrees while banked about five degrees to the left. The ground impact position was about 150-200 metres to the right of the centreline for the 27 ILS approach. The track of the aircraft at the time of the accident was about 245 degrees. Examination of the badly fire-damaged wreckage did not produce evidence of any significant defects. At the time of ground contact the landing gear was extended and the flaps were in the 20-degree position.

The tuning units for the VHF radios and navigation receivers were badly fire damaged. However, it was established that the cockpit selector for the number one VHF navigation receiver was tuned to 109.3 MHz, the frequency for the runway 27 ILS and the number two VHF navigation receiver to 114.1 MHz, the frequency for Melbourne VOR. One glidepath receiver was fitted and although some impact damage was sustained in the accident, no evidence of any pre-existing defect was identified. Examination of the altimeters established that the pilot's was correctly adjusted to a QNH setting of 1008 hectopascals and the co-pilot's was set to 1013 hectopascals.

Weather data

The amended terminal area forecast for Melbourne, issued at 1929, included a prediction of 7 octas of stratus cloud, base 500 ft. The 0100 aerodrome weather report for Melbourne included an observation of 2 octas of stratus at 500 ft and 3 octas of stratus at 1,000 ft. The ATIS current at the time of arrival of VH-IAM, was runway 27, damp, wind light and variable, QNH 1008, temperature 17, 7 octas cloud, base 200 ft, drizzle, expect ILS approach. Flight conditions for the ILS approach were smooth. The Bureau of Meteorology estimated that the low stratus cloud layer extended up to an altitude of 4,500 ft.

ILS approach procedure

The published chart for this procedure showed that the approach commenced at an altitude of 3,000 ft at the Epping locator beacon which was 8.5 NM east of the runway threshold. The specified track was 263 degrees magnetic, and the glideslope angle was 3 degrees.  The outer marker beacon was at 3.8 NM from the runway threshold and the middle marker was 0.6 NM from the runway threshold. The pilot was required to keep the aircraft within two dots of the on glidepath and on track ILS indications to remain within specified tolerances. If the aircraft was on the glidepath at the outer marker the altitude would have been 1,645 ft.

As the aircraft gets closer to the runway the ILS localiser and glide path beams become progressively narrower, requiring increased flying accuracy to remain within limits. The minimum altitude for the approach was 610 ft and this altitude should have been reached at about the position of the middle marker. Provided that the high intensity runway and approach lights were on, the required flight visibility to continue the approach was 800 metres. If this minimum visibility did not exist, a missed approach was required. The missed approach procedure was to maintain a track of 263 degrees magnetic and climb to 4,000 ft.

The ILS chart also provides a table of DME distances against altitudes. This allows pilots to make progressive checks of altitude, independent of the ILS cockpit needle indications, to monitor the progress of the ILS. However, DME is not mandatory for the approach which can be satisfactorily completed by reference to the needle indications and by making altitude checks at the locator beacon, the outer marker and middle marker beacons. The elevation of the runway 27 threshold was 407 ft.

Radar data

A readout of the air traffic control radar data tape for the approach indicated that tracking, altitude, and speed anomalies had occurred during the approach.

Tracking

At 3 NM from the runway threshold the aircraft was about 440 metres left of the runway centreline. A heading alteration to the right of about 30-40 degrees was made and the aircraft passed through the centreline and went about 250-300 metres to the right. At the time of ground impact, the aircraft heading had again been altered, and the aircraft was closing on the centreline from the right.

Altitude

The aircraft had passed slightly north of the Epping locator beacon, which marks the start of the ILS final approach, at an altitude of about 2,800-2,900 ft. This altitude was maintained until 2 NM past Epping, when the aircraft was about 200 ft above the glidepath. The descent was then started and continued with the aircraft descending through the glideslope at about 5 NM from touchdown. The descent continued with displacement below the glidepath increasing. Between approximately 2 NM and 1.5 NM from touchdown the descent temporarily stopped at about the minimum altitude for the approach. (This minimum altitude was 610 ft but the radar data only reads out in increments of 100 ft.)  At this stage the aircraft was about 400-450 ft below the glidepath. Descent then recommenced, probably at an increased rate. The last altitude recorded was at approximately 400 ft in the vicinity of the accident site.

Speed

Radar data records calculations of ground speed.  From 10 NM into 6 NM the speed was about 145-150 knots. It then increased and at 5 NM peaked at about 170 knots. The speed then decreased to about 120 knots at 2.5 NM. It briefly increased to about 138 knots at 2 NM then decreased to 120 knots at the accident area. During the ILS approach the wind at 3,500 ft was estimated to be a south-easterly at 20 knots. This varied moderately to be a southerly at 7 knots at 1,000 ft. This indicated that the winds were mainly from abeam and that most of the ground speed fluctuations were probably associated with pilot handling.

Pilot/aircraft handling information

The pilot's logbook was not located after the accident. Most of his experience was on twin piston-engine aircraft such as the Cessna 310 and the Piper PA 31. He also had some time on Nomad aircraft. His last instrument rating renewal was carried out on a Cessna 310 aircraft. The renewal for conduct of an ILS or VOR approach was not covered on that flight but was completed separately in a synthetic trainer.

Advice on the aircraft handling characteristics was obtained from a pilot who was very experienced on the type. He indicated the MU2 was a faster, more difficult type to fly in comparison to general aviation twin piston-engine aircraft on which the accident pilot had gained most of his experience.  After inspecting the radar readout data, he said that VH-IAM was never stabilised on the ILS approach.

The MU2 is an aerodynamically clean and pressurised aircraft. This means that unlike piston engine types the pilot had flown, there would not have been the audible changes in wind noise associated with airspeed changes which provide clues to the changing situation. The experienced pilot consulted during the investigation indicated that with changes in airspeed and/or engine power it is very easy for the MU2 to quickly develop a rate of descent. This can only be detected by close monitoring of the cockpit instruments.

Medical/Fatigue

There was no medical evidence of any condition that might have contributed to the accident.

Specialist advice provided to the investigation indicated that persons involved in night shift work experience circadian disruption. This is because of the disruption of normal sleep and the quality of sleep gained. The main factor known to regulate the sleep/wake cycle is core body temperature. The best quality of sleep is gained when the core body temperature is at its lowest point, which usually happens between 0200 and 0600. As body temperature increases during the day, sleep quality and duration decreases.

Research shows that even where people are exposed to long periods of night shift the human circadian rhythm does not adjust. However, if the individual forms a routine of night shift that is consistent, they can partially compensate. Techniques to assist include the use of heavy drapes and air conditioning and buffering of outside noise.

The pilot was on the second night of night operations. Flying at night is a normal situation for pilots engaged in these type of freight operations. The pilot spent the afternoon before the accident with a pilot friend who had also flown the night before. The friend understood the pilot had slept through to 1300 after the previous night of flying and did not feel fatigued.

ANALYSIS

Because of the specialist advice that the effect of changing to night operations inevitably affects the quality of sleep achieved, it is likely that some fatigue effect existed.

No evidence was found to suggest any aircraft malfunction existed or contributed to the accident.

The cloud base being at the approach minimum altitude would have required the pilot to fly the aircraft to the minima in cloud, at night. Even so, the smooth conditions in the cloud should have made the flying task relatively easy. The knowledge that other aircraft had landed off an ILS approach may have given the pilot an expectation that he should also be able to land.

The evidence indicated that the pilot flew an erratic and unstable approach, in terms of airspeed, track, and glidepath maintenance. The safe operation of the aircraft on the approach required keeping it within specified limits for tracking and glidepath and not going below the permitted minimum. This was not done. The reason for descent below the glideslope and the minimum altitude at a late stage of the approach was not determined but was very likely unintentional.

The MU2 is a faster and more demanding type to fly compared to general aviation piston engine twin-engined aircraft on which the pilot had gained most of his experience. Anecdotal evidence suggests that to minimise costs, many pilots undertake the flight segment of their instrument rating renewal in relatively low-performance aircraft and complete the balance in a synthetic trainer. Therefore, a pilot may be endorsed and operate a high-performance aircraft in IMC yet not have practised instrument flying in that type of aircraft.

Civil Aviation Regulations 5.81 and 5.108 require non-instrument rated private and commercial pilots to undertake Biennial Flight Reviews. The Biennial Flight Review must be conducted in an aircraft type in which the pilot flew the greatest number of hours as pilot in command during the 10 flights before the review.

The Bureau believes that a similar criterion should apply to instrument-rated pilots. It would be appropriate for flight segments of instrument rating renewals to be conducted on a complex, high-performance aircraft, representative of the types that the pilot wishes to operate.

Considering the length of the pilot's ICUS training on the MU2, the approach into Sydney and the accident approach indicated a deficiency with his instrument flying skills. The company training system had not detected this situation, but the specific reasons for this were not determined.

SIGNIFICANT FACTORS

1. The company's training system did not detect deficiencies in the pilot's instrument flying skills.
2. The cloud base was low at the time of the accident and dark night conditions prevailed.
3. The pilot persisted with an unstabilised approach.
4. The pilot descended, probably inadvertently, below the approach minimum altitude.
5. The pilot may have been suffering from fatigue.

SAFETY ACTION

As a result of the investigation, the Bureau issued Safety Advisory Notice 960032 to the Civil Aviation Safety Authority on 02 September 1996.

"SAN 960032

"CAO 40.2.1 lays down the requirements when synthetic trainers are used for instrument rating renewals. This allows for the instrument rating renewal to be undertaken on a category B synthetic trainer except for the renewal of one aid which shall be conducted in flight. However, the CAO does not stipulate the type of aircraft that must be used. The renewal therefore can be carried out on a relatively low-performance aircraft.

"The Civil Aviation Safety Authority should note the safety deficiency identified in this report."

The following response was received from the Civil Aviation Safety Authority on 19 November 1996.

"I refer to your Safety Advisory Notice SAN 960032 concerning the accident involving Mitsubishi MU2B-30, VH-IAM during an instrument approach at Essendon, Victoria on 21 December 1994. The following comments are forwarded for your consideration.

"It can only be speculated that the accident occurred due to the pilot's lack of currency on type. The accident could equally have been caused by distraction, fatigue, or the like. It is current CASA policy that the multi-engine command instrument rating is a generic rating for multi-engine aeroplanes. Given that there are several thousand command instrument rating tests undertaken each year there does not appear to be an accident trend to suggest that the associated flight test provisions are deficient.

"The desirability, or otherwise, of reviewing Civil Aviation Order 40.2.1 will be raised as an issue under the Regulatory Framework Review program. The Personnel Licensing Technical Committee will be responsible for this issue. The suggestion to align flight test aircraft requirements with similar provisions that exist for flight reviews has merit and will be referred to this committee.

"We shall keep BASI appraised of the outcomes of this, and other committee deliberations."

The glider had been prepared for its first flight of the day and found airworthy. The pilot was considered to be competent and had been trained in all emergency procedures pertaining to winch launches.

Witnesses reported that although the take-off appeared normal, the glider climbed at a steep angle and slow forward speed.  At about 200 ft above ground level the winch tow cable failed. The pilot lowered the nose to about the level flight attitude before commencing a turn to the right and releasing the broken tow cable. As he had not lower the nose sufficiently for the glider to gain flying speed, it stalled, entered a spin and impacted the ground.

Winch tow cable are known to break regularly, and glider pilots are trained to cope with this situation.  It could not be determined why the pilot failed to apply the correct recovery procedures.

FACTUAL INFORMATION

The aircraft was being flown on a night navigation training exercise from Canberra to Bankstown, then returning via Bathurst, in accordance with the night visual flight rules (NGT VFR). The crew included an instructor, a licensed private pilot undergoing NGT VFR training, and a licensed student pilot who was observing the flight from a rear seat. The exercise was to include a diversion during the return leg. The planned cruising altitude for the return leg was 7,500 ft, remaining outside controlled airspace. The flight plan submitted included the lowest safe altitude (LSALT) for each of the planned legs. The flight was conducted entirely at night.

The pilot-in-command held valid instructor and command instrument ratings. The pilot under instruction was undertaking NGT VFR training as a qualification towards obtaining a commercial licence. He had previously completed some basic instrument flight training.

The aircraft departed Canberra at 1745, arriving at Bankstown at 1853 after an apparently uneventful flight. It subsequently departed Bankstown at 1945 for the return flight. Recorded radar data indicated that, in accordance with its flight plan, the aircraft initially tracked towards Katoomba and climbed to 2,000 ft. After passing 22 NM from Sydney the aircraft commenced a further climb, reaching 4,300 ft by 33 NM, having infringed controlled airspace without a clearance. The aircraft then turned left onto a reciprocal track and descended to 2,300 ft. After travelling about 9 NM along the reciprocal track the aircraft turned right and tracked south towards Camden, descending to 2,100 ft. The pilot under instruction advised Flight Information Service that he was amending his flight plan and was now tracking to Canberra via Camden and the Shellys non-directional beacon (NDB).

After passing Camden, the aircraft turned onto a south-westerly track, towards the Shellys NDB, and gradually climbed to an altitude of 3,100 ft. The climb rate was erratic and included periods where the aircraft descended at up to 300 ft/min. The altitude flown did not conform with the enroute LSALT of 3,900 ft. At 2017, a minute after reaching its maximum altitude the aircraft commenced a gradual descent at rates of up to 350 ft/min. Passing 2,500 ft, the aircraft turned left through 110 degrees onto an easterly track before colliding with terrain in the Hilltop area, at an elevation of about 1,820 ft, some 2 km south of the last recorded radar position. The calculated groundspeed just prior to impact was more than 150 knots.

An examination of the wreckage found no defects which were likely to have contributed to the accident. The aircraft had initially collided with the crown of a tree about 18 m above the ground, descending at an angle of about 15 degrees, in a wings level attitude. Both wingtips had been detached on impact with the tree, and their relative positions suggested the aircraft had been inverted at that point. An emergency locator transmitter (ELT) fitted to the aircraft had activated on impact. Another activated ELT was also found in the wreckage. This unit was the personal property of one of the occupants. The ELT signals assisted the crew of a search helicopter to subsequently locate the accident site.

Post-mortem examinations indicated that neither the instructor or rear seat observer had any pre-existing physical condition likely to have contributed to the accident. The student was found to have severe coronary artery disease, but there was insufficient evidence to indicate that he had suffered some form of inflight incapacitation. Toxicological analysis indicated the three crew members, despite being non-smokers, had carbon monoxide saturation levels ranging between 7% and 8%. The reason(s) for the elevated carbon monoxide levels was not established, however, values of up to 10% at sea level are considered to be within the normal range.

A specialist analysis of the weather conditions in the vicinity of the crash site indicated there was fog in the area, with five to eight octas of stratus or cumulus cloud ranging from 2,000 ft to 8,000 ft. The wind was light and variable. The temperature was eight degrees Celsius.

ANALYSIS

After departing Bankstown, the aircraft had conducted a step climb, apparently attempting to remain outside controlled airspace whilst achieving LSALT requirements. However, just prior to commencing the diversion, the aircraft had briefly penetrated controlled airspace. It then tracked towards Camden, descending to 2,300 ft. After passing Camden the aircraft remained below the enroute LSALT, failing to climb to 3,900 ft, although the aircraft did climb somewhat erratically to 3,100 ft, remaining there for only a short time before gradually descending into the ground. The vertical profile flown prior to the accident would appear to indicate that the instructor was not adequately monitoring the performance of the student and consequent flight progress. It could not be determined if the student's heart disease contributed to the accident, however, if he had become disabled then it would be expected that the instructor could have regained control of the aircraft with the assistance of the passenger.

The reason why the aircraft had climbed somewhat erratically after passing Camden, and then descended, may have been due to an attempt to remain clear of cloud. The radical alteration of track, and increase in groundspeed just before impact, may have been indicative of the student becoming spatially disoriented whilst attempting to either remain clear of instrument meteorological conditions (IMC), or having unintentionally entered IMC. Why the instructor, who was qualified to fly in IMC, did not, or could not intervene, was not able to be established. The carbon monoxide levels, although slightly elevated, are not considered to have been sufficient to have caused any significant impairment of the performance of the flight crew.

SIGNIFICANT FACTORS

The investigation was unable to determine with any certainty the significant factors associated with this occurrence.

The pilot was spraying a tomato crop at the time of the accident. A set of three powerlines ran along the edge of the field at approximately 20 degrees to the direction of flight. It was reported that the pilot had been turning left off his spray runs and, on this occasion, the right wing had collided with the three wires from below during the start of the turn. The tip of the right wing struck the wires first. The aircraft then appeared to have rolled right and struck the ground with the right wing, cartwheeling until it came to a stop. The engine bay was destroyed decreasing the occupiable space in the cockpit. The pilot was still conscious when he was pulled from the left side of the wreckage. He was wearing a helmet which had been retained during the crash sequence and had suffered facial injuries as well as broken limbs. His visor appeared to have been up at impact.

The sun angle was off to the pilot's left by about 45 degrees and about 30 degrees above the horizon. It was reported that the wires were shiny with reflected light, immediately after the accident, and they should have been visible from the direction of flight.

It is probable that the pilot misjudged his clearance from the powerlines during the turn.

The pilot was having a dam constructed on his property which is adjacent to the Oakey airfield. Witnesses working on the dam site reported that the pilot had indicated that he would conduct a low fly-past over the dam after taking off from Oakey.

The aircraft was observed to fly at low level across the dam and commence a climb before striking powerlines located on the property. After the mainwheels contacted the wires, the aircraft impacted the ground inverted. The pilot received fatal injuries.

On 14 January 1994 at 0114, Aero Commander 690 aircraft VH-BSS struck the sea while being radar vectored to intercept the Instrument Landing System approach to runway 34 at Sydney (Kingsford-Smith) Airport, NSW. The last recorded position of the aircraft was about 10 miles to the south-east of the airport. At the time of the accident the aircraft was being operated as a cargo charter flight from Canberra to Sydney in accordance with the Instrument Flight Rules. The body of the pilot who was the sole occupant of the aircraft was never recovered. Although wreckage identified as part of the aircraft was located on the seabed shortly after the accident, salvage action was not initially undertaken. This decision was taken after consideration of the known circumstances of the occurrence and of the costs of salvage versus the potential safety benefit that might be gained from examination of the wreckage.

About 18 months after the accident, the wing and tail sections of the aircraft were recovered from the sea by fishermen. As a result, a detailed examination of that wreckage was carried out to assess the validity of the Bureau's original analysis that the airworthiness of the aircraft was unlikely to have been a factor in this accident. No evidence was found of any defect which may have affected the normal operation of the aircraft.

The aircraft descended below the altitude it had been cleared to by air traffic control. From the evidence available it was determined that the circumstances of this accident were consistent with controlled flight into the sea.

No safety recommendations resulted from this investigation.