Circumstances:

The helicopter was operating onto a floating pontoon situated adjacent to a reef area. The pontoon was 30.65 m long and 9.32 m wide and consisted of a wooden platform mounted above two steel floats. A series of hardwood joists 295 mm x 85 mm and approx. 950 mm apart were mounted between the floats and 35 mm x 110 mm hardwood decking was nailed to the joists to form the platform surface. The decking ran lengthwise along the pontoon. The pontoon was constructed in 1985 and had been in operation almost continuously since then. While mainly skid equipped helicopters operated onto the pontoon, it had also been used by wheeled helicopters, including the Agusta 109. It was established that Agusta 109s had landed on the pontoon on some hundreds of occasions prior to the accident. Company pilots reported that they had observed decking planks bend when subjected to the weight of the Agusta 109 through its mainwheels. For this reason, the general practice for Agusta 109 operations onto the platform was for the mainwheels to be positioned over the joists when landing along the pontoon parallel to the decking. At the time of the accident, there was a northerly wind at about 15 kts and the pontoon was pitching some 25-30 cm in the swell. The northern end of the pontoon was occupied by another company helicopter which had just landed and was parked across the pontoon with its engine running and passengers still on board. VH-LHJ approached into wind to land along the pontoon. The helicopter was being flown by the pilot in the left seat. Shortly before the wheels contacted the decking, the pilot in the right seat opened his door to check the position of the mainwheels in relation to the joists. As the mainwheels touched the surface, he reported to the pilot flying the aircraft that the mainwheels were 6-8 in behind the beam. As the weight of the helicopter was transferred to the wheels, the right-seat pilot saw the decking beneath the right mainwheel flex slightly and then crack and break. The helicopter rolled rapidly to the right and the main rotor blades began impacting the pontoon and the water. The helicopter eventually came to rest on its right side, having veered about 130` to the right adjacent to the southern edge of the pontoon. The impact forces destroyed the main rotor blades, substantially damaged the rotor head, and broke the tail boom. There was no evidence of any fault in the helicopter which might have contributed to the accident. There was also no evidence of a hard landing or any other pilot-related aspect which might have caused excessive loads to be placed on the decking during the landing sequence. The investigation therefore focused on the pontoon itself, and a study was commissioned to examine the strength of the pontoon decking with respect to the helicopter types known to use the pontoon. The results of the evaluation of the pontoon decking were as follows 1. The condition of the decking timber was such that deterioration due to exposure to the elements was concluded not to have been a factor in the deck failure. 2. The failure of the decking when subjected to Agusta mainwheel loading was due to grossly excessive bending stress. The overload factor was calculated as 8.39 and readily explained the failure. The only pontoon design documentation which could be located concerned the general structure and dimensions of the pontoon and contained no details on deck strength considerations. No comment can be made, therefore, as to whether the wheel or skid loadings of the various helicopter types using the pontoon, and particularly those for the Agusta 109, were considered during the design of the pontoon.

Significant Factors:

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

1. The strength of the pontoon decking was inadequate for Agusta 109 operations.

2. The pontoon decking failed due to excessive bending stress when subjected to loading through the right mainwheel of the helicopter.

Recommendations:

The helicopter operator and the pontoon owner, along with the Civil Aviation Authority (CAA), were notified of the progress of the investigation. This included information contained in a preliminary report followed later by the complete testing details, technical analysis, and stress calculations concerning the pontoon decking. The analysis concluded that the strength of the decking was inadequate for all helicopter types which used the pontoon and steps were instituted by the operator and the pontoon owner for the deck to be strengthened.

1. A recommendation was made to the CAA on 13 September 1991 that the circumstances of the accident be brought to the attention of other organisations involved in operations on to helicopter landing sites with timber decking and that these organisations confirm the design specifications of those surfaces for the particular types of helicopter involved.

2. It is further recommended that the Civil Aviation Authority through surveillance, following the failure and subsequent repair of this pontoon, confirm that the pontoons and other helicopter landing sites which are being used by this operator, have the structural integrity to accommodate operations of the relevant helicopter types.

Circumstances:

The pilot had flown from Archerfield to Surfers Gardens to pick up a passenger and made a normal landing on strip 12. About 20 minutes later he was taxiing for take-off on strip 12 when the nosewheel strut collapsed, and the propeller struck the ground. The ALA had only recently been reopened after having been closed for some time due to a soft wet surface. The nosewheel had entered a slight depression prior to the strut collapsing but the depression should not have been sufficient to overload the strut to the point of failure at normal taxiing speed. Examination of the nose gear showed that the metal to metal epoxy bonding which attaches the torque tube to the airframe end fittings had failed. This failure allowed the torque tube to rotate inside the end fittings, to the extent that all normal suspension action was lost. The nose gear strut assembly then folded upwards into the engine cowls, and the propeller struck the ground. The epoxy bonding had deteriorated to the extent that the load carrying capacity of the nose gear had been substantially reduced.

Significant Factors:

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

1. The nosewheel entered a depression whilst the aircraft was being taxied.
2. The epoxy glue which bonds the nose landing gear torque tube to the attachment fittings failed.

Recommendations:

The engineer involved in the recovery of the aircraft had previously experienced a similar failure on this type of aircraft. As a result, he had sought assistance from the American distributor. The distributor confirmed that as a result of many USA operators experiencing similar defects, a Supplemental Type Certificate (STC) number SA3564SW, had been issued allowing modification of the torque tube and end fittings. This simple modification places taper pins through the torque tube and end fittings, effectively preventing movement even if the epoxy bonding deteriorates. The Civil Aviation Authority should examine the above aspects with a view to recommending incorporation of a similar modification to all high-houred aircraft of this type.

Circumstances:

The aircraft had taken off on runway 24 towards a range of hills. Wind at the time was reported as a steady 20 knots from the south-west, straight down the runway. After take-off, the pilot retracted the landing gear and reduced power for climb. He reported that soon after, the aircraft encountered a windshear, lost airspeed, and failed to climb. He did not reapply full power. There were no clear areas ahead, so he commenced a left turn; however, the airspeed decayed further, and the left wing dropped. The aircraft struck the top branches of a 15 m pine tree, rolling inverted before coming to rest approximately 15 m from a house. The occupants were trapped in the wreckage until emergency services arrived. The accident site was approximately 1 250 m south-west of the end of the runway. The terrain is below a five percent gradient, but beyond this area it rises quite steeply to a ridge line approximately 5 km from the runway. No fault was found with the aircraft. There was evidence from propeller strike marks on severed branches that the engine had been delivering substantial power at the time of impact. The area is well known for local wind effects due to the terrain. The prevailing wind direction would have been conducive to wind shear in the lee of the ridge where the accident occurred. This is the second of three similar accidents which have occurred within an area of 1.5 km during the last few years. In each case the aircraft failed to outclimb the terrain after taking off from runway 24.

Significant Factors:

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

1. The aircraft may have encountered windshear soon after lift-off.

2. The pilot did not operate the aircraft for maximum performance.

3. The pilot was not able to maintain speed.

Recommendations:

Over the past ten years BASI records indicate at least 16 take-off accidents to fixed wing aircraft attributed in part or totally to the effects of wind over the local terrain and to high density altitude. The following recommendations are made:

1. The CAA consider preparing an educational article to be widely distributed detailing considerations for GA type aircraft operations in areas where flight may be affected by terrain, wind, and density altitude.

2. The CAA bring to the attention of training schools the need to accent these issues in both theoretical and practical training.

Spraying operations were being conducted in generally calm weather conditions. One load had been sprayed successfully, but the pilot later advised that, as he manoeuvred at the end of the second run with the next load, sink was encountered. Although he dumped the remainder of the load, he reported that he had insufficient time to increase power. The aircraft collided with a tree, then struck the edge of a road and groundlooped into an adjacent crop. Weather conditions at the time were unlikely to have produced any sink. It was probable that while turning towards rising ground the pilot misjudged the slope of the terrain. The aircraft had stalled, with insufficient height available in which to effect a recovery.

The pilot was accompanied by two friends on a local flight to view a property in the South West Rocks area. About twenty minutes after take off, the engine commenced to run roughly and lose power. The pilot carried out a trouble check which revealed the left magneto had failed. Whilst the pilot was attempting a forced landing the engine stopped, the aircraft collided with trees before coming to rest in a semi-inverted attitude. The pilot and passengers were able to vacate the aircraft without assistance. Post accident testing of the ignition system revealed that both magnetos were unserviceable because of age deterioration of the insulation around the transformer coils. The failure of both magnetos resulted in the loss of engine power. A service bulletin was issued by the magneto manufacturer in 1973 which recommended replacement of the transformer coils in the type of magneto fitted to VH-DLT. The aircaft maintenance records show the magnetos were repaired and tested in 1985 but the transformer coils were not replaced as recommended by the service bulletin.

The pilot was cleared to conduct a straight in approach at the destination aerodrome. At a position 15 kilometres from touchdown, he commenced the prelanding checks and selected gear down. The gear selector panel indication of three green lights and a visual inspection from the cockpit windows, which included the use of an engine cowl mounted mirror to view the nose landing gear, confirmed that the landing gear was fully extended. Shortly after touchdown, the right main gear collapsed causing the aircraft to veer from the runway. An inspection of the gear and its systems revealed two defects which are considered to have contributed to this accident. The throttle warning horn had been rendered unserviceable due to a blown fuse in the warning system electrical circuit. The down-lock pin had failed to locate in the lower dragstay due to a worn bearing, allowing the stay to be misaligned from the lock pin. The down-lock microswitch is attached to the lower dragstay and does not come into contact with the down-lock pin. It is therefore possible for the gear to be fully extended, the electrical circuit to be made and three greens indicating, but for the down-lock pin to be disengaged. It is considered that the gear extended fully prior to touchdown, providing the pilot with three green indications, but remained in an unlocked state due to the misalignment of the lock assembly. As the weight of the aircraft transferred onto the gear during the landing roll, the unlocked gear collapsed. The pilot was deprived of an aural warning, due to the failed aural warning electrical warning circuit. The investigation also revealed a potential problem with the main gear ground handling lock pin system, which is used to prevent the down-lock pin from dislocating. If the down-lock pin has not correctly located in the lower dragstay, the ground handling pin is ineffective. This accident was not the subject of an on-site investigation.

The pilot intended to transport two passengers and their equipment along the Katherine Gorge. The helipad used for take-off was on the side of the gorge, some 40 feet above the river level. The pilot initiated a running take-off on the skids, but the helicopter began to sink as it left the river bank. Full throttle was applied, but without effect. As the helicopter approached the opposite bank at tree-top level, the pilot raised the collective lever in an attempt to clear the trees. The aircraft did not respond and as it continued to sink, the pilot recalled seeing the engine and rotor rpm decay towards the lower limit of the operating range. The helicopter descended into the trees and came to rest on its left side about 400 metres from the take-off point. The pilot subsequently advised that the helicopter had not been performing as well as he had expected during previous flights. Investigation revealed that the engine had been unable to develop rated power output and that the helicopter was some 114 kilograms over the maximum permissible all-up weight. Detailed examination of the turbocharger revealed that various components had suffered severe deterioration. The unit had exceeded its authorised life by nearly 400 hours. It was also likely that pilot operating techniques had contributed to the faults in the turbocharger, in that insufficient engine idling time prior to shutdown had been allowed.

The aircraft was in normal cruise at 1500 feet above sea level when the pilot noted a mild shuddering, and almost immediately the oil pressure reading dropped to zero. Shortly afterwards, the engine began vibrating severely, and the pilot was committed to a forced landing. In the latter stages of the approach the pilot was forced to pull-up to clear powerlines, following which the aircraft descended and struck a tree and a steel mesh fence at the edge of an industrial area. Investigation revealed that the flexible oil line between the engine and oil cooler had failed due to deterioration, resulting in oil starvation and seizure of the engine. Examination of Bureau records revealed three other recent occurrences in New South Wales where the subject hoses have failed in flight. The hoses are currently required to be inspected and tested every six years. However, the manufacturer recommends that the hoses should be replaced every five years or at engine overhaul, whichever comes first. The particular hose which failed had been in service for more than six years.

Circumstances:

The aircraft had been flown twice that day prior to the accident flight. No problems or unserviceabilities had been reported. The purpose of this flight was to take a youth for a joy flight and the passenger emplaned while the engine was still running after the previous flight. After take-off, the aircraft was seen by several witnesses to fly low over the strip and adjoining areas before starting a manoeuvre at low level which resulted in the aircraft apparently stalling. The aircraft was then seen to rotate several times before crashing in a near vertical attitude through several branches of a large tree. Witnesses ran to the aircraft and found the pilot dead, but they were able to free the surviving passenger from the rear seat. It would appear that at the time of the accident, the pilot was carrying out some form of impromptu display at low level or "showing off". The investigation established that the pilot was want, at times, to show off or enjoy "pushing it" or taking an aircraft to its limits. Although it was not possible to determine the exact manoeuvre performed by the pilot which lead to his loss of control, there is no doubt that he carried out a manoeuvre at low level that resulted in the aircraft stalling at a height insufficient for recovery. Such a manoeuvre was apparently induced by the pilot rather than as a result of his experiencing a problem with the aircraft. No faults or anomalies were detected in the aircraft that could have contributed to the accident. All witness evidence is consistent in that the "spin" or spiral occurred after the aircraft entered the turn at low level. During his earlier flight in the aircraft that day, the pilot was reported to have performed aerobatic manoeuvres. The aircraft was not certified for aerobatic flight, and no record was found of the pilot holding an endorsement to perform aerobatic manoeuvres.

Significant Factors:

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

1. The pilot was engaged in an unauthorised impromptu display at low level.

2. The pilot stalled the aircraft at a height insufficient for recovery.

3. The pilot attempted manoeuvres beyond his level of experience.

Recommendations:

It is recommended that the Civil Aviation Authority

1. Require evidence of logbook endorsements for aerobatic manoeuvres, Biennial Flight Reviews, and other logbook only entry qualifications to be recorded on the departmental pilot history file.

The rudder failed when the pilot initiated a climb at the end of a spray run. The rudder was bent over at the top by about 45 degrees, but the pilot was able to maintain control of the aircraft and carry out a safe landing at Dalby. The rudder spar had failed above the top hinge point near a weld which was associated with a modification to replace the single point hinge with a three point hinge. The failure of the spar was caused by the pressure of a crack which had not been detected prior to the welding of the upper hinge modification. This accident was not the subject of an on-site investigation.