The pilot had recently purchased the glider, and had previously made two short flights in it, for endorsement and familiarisation purposes. On the day of the accident he had trailered the glider to the launching strip, and had then assembled and rigged it for flight. A normal winch launch was carried out, with the glider releasing from the winch at about 1000 feet above the ground. It was then observed to be circling in a thermal, while gaining a further 500 feet of altitude. The angle of bank at this time appeared to be moderately steep. A witness then observed that the nose of the glider dropped and the aircraft commenced to spin to the left. It spun rapidly in a steep nosedown attitude, with occasional pitch oscillations, and recovery was not effected prior to impact with the ground. The subsequent investigation did not reveal any apparent faults or defects with the aircraft which might have led to the development of the accident. In addition, there was no medical evidence to indicate that the pilot was incapacitated or unfit to perform his duties as pilot in command. Although the pilot had received training in spin recognition and recovery techniques, he was possibly unaware that a spin could occur during an apparently normal thermalling turn. It could not be established when he had last performed spinning manoeuvres.

Circumstances:

The sea state for take-off was moderate with a 35 centimetre chop. As the aircraft approached 40 knots, it struck a wave and bounced into the air. When the aircraft settled back onto the water it was yawed to the left, and this caused it to slide sideways into another wave. The engine and its support pylon broke off at the fuselage. The aircraft sank shortly after coming to a stop. All occupants evacuated successfully. The pilot reported that the yaw was probably induced when the left hand float entered a wave. He was unable to realign the aircraft before it collided with the second wave. The force of the impact although it did not feel severe, caused the engine and pylon to break off. The rear seat passenger seated on the left hand side, was injured when the sash seat belt anchor point was torn from the aircraft. The sash seat belt upper anchor points are also the anchor point for the engine pod bracing wires. As the engine pod and support collapsed to the right, the left hand bracing wire and anchor block were pulled from the fuselage, tensioning the left sash belt and pulling the passenger's head into the fuselage structure.

Recommendations:

The Bureau conducted an examination of the seat belt anchor point failure.

1. It is recommended that the Manufacturer redesign the seat belt anchor point so that it is separate from the engine pod bracing wire anchor point

While performing the pre-flight inspection, the pilot carried out an engine run to check the engine performance. At the completion of the run he allowed the engine to idle for several minutes, during which time it suffered from carburettor icing and stopped. The pilot, having satisfied himself that it was only ice which caused the problem, prepared for DEPARTURE. Both he and his passenger embarked and he taxyed the aircraft for approximately 6 minutes to the threshold of the into wind runway. He then spent a further 2 minutes completing the pre-takeoff checks. The takeoff and climb were sluggish and after climbing to 150 ft AGL the pilot retracted the landing gear. He turned onto a downwind heading, and at 250 ft AGL reduced the engine power from the take-off setting. The engine then commenced to surge and lose power. As there was sufficient height available he decided to glide back for a landing on the DEPARTURE runway. During the approach he continued trying to locate the reason for the engine malfunction, then at about 60 ft AGL he lowered the gear and stopped the engine. As he commenced the round out for landing the pilot became unsure as to whether the gear had been correctly locked down, and became distracted checking the lever position. He inadvertently moved the control stick rearwards, causing the glider to balloon, lose airspeed and stall. A heavy landing ensued. The engine malfunction was probably the result of carburettor icing. The engine was not equipped with any method for preventing or removing ice, and conditions on the particular day were such that icing could be expected at any power setting.

Circumstances:

The aircraft was engaged on a training flight involving instrument flying and circuit practice. At Griffith, the pilot carried out a VOR let down from which the aircraft was positioned for a circling approach to runway 24. The landing gear was extended during the instrument letdown procedure, and the cockpit indicator showed the landing gear was safely down and locked. When the aircraft was on final approach, both pilots checked that the landing gear indication was unchanged. The pilot reported a normal touched down, when without warning, the right main gear leg collapsed. The pilot was able to bring the aircraft to a halt on the runway. The wind conditions at the time were variable at 5 knots. A technical examination revealed the right main landing gear had collapsed as a result of material failure. It was determined that the lock nut which secured the rod end of the piston rod of right hydraulic actuating cylinder had loosened. This permitted the rod end to screw into the piston rod, shortening the length of the piston rod. The shortening of the hydraulic actuating cylinder rod travel prevented the drag brace from being positioned in the over centre position to complete the extension cycle. The locknut had progressively loosened due to contact with the rear end of the clevis yoke in the final stages of leg extension. As a result, the loads from the right main gear were taken by the right hydraulic actuating cylinder and its mountings. The right clevis on the landing gear strut consequently failed in overload. The pilots were unaware of an unsafe right main gear. The down lock micro switch was incorrectly adjusted, such that a green light "safe" indication appeared in the cockpit before the drag brace was in the over centre or locked position.

Significant Factors:

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

1. Insufficient clearance existed between the clevis yoke and the rod end locknut.

2. The locknut progressively loosened when it contacted the mounting yoke for the rod end on the right main gear strut.

3. The piston rod of the right hydraulic actuating cylinder shortened when the lock nut on the rod end loosened.

4. The shortened piston rod prevented full extension of the right main gear leg and overcentering of the drag brace.

5. The down lock micro on the right main gear leg was incorrectly adjusted and indicated "safe" when the extension sequence was incomplete.

6. The mounting yoke on the strut for the right hydraulic actuating cylinder failed in overload.

The aircraft reported departing Bundaberg for Monduran Dam on a no SAR flight at 1135 hrs EST with three persons on board and an endurance of 270 minutes. The purpose of the flight was to complete the endorsement of the pilot under check and to assess the suitability of an area of water on the coast to where the passenger, who was the regular pilot of the aircraft, was to fly the aircraft the following day. The pilot in command had flown 27 hours in the previous three months, of which 9 were on type. The pilot under check had flown only one hour in the last three months. This flight had been in VH-BSL. At approximately 1200 hrs, the aircraft was observed in the Lake Monduran area. It flew two left hand circuits, landing into wind towards the dam wall each time. After the second takeoff, it turned left and was seen heading north from the lake. Nothing further was heard or seen of the aircraft. Following an extensive search, the wreckage was located six days later lying inverted in 15 metres of water approximately 2 km WNW of the dam wall in the area of the junction of the main east-west channel and a north-south channel of the lake. Both floats had separated from the aircraft and the right float was severely torn for about half its length. There was substantial water impact damage to the windshield frame/cockpit roof area and to the upper leading edge surfaces of both wings. No fault was found with the aircraft or its systems which might have contributed to the accident. It could not be determined who was manipulating the controls of the aircraft at the time of the accident. Evidence was obtained that it was the habit of the check pilot to have pilots undergoing endorsement or check to fly two circuits landing into wind and then to carry out crosswind landings. The check pilot and the pilot under check had previously operated at the dam and alighted on to both the east/west and the north/south channels. Having been observed to fly two into wind circuits and then head north and not be sighted again, it is possible that the aircraft then commenced crosswind operations onto the north/south arm of the lake, landing in a southerly direction with a crosswind from the left. Information from the Bureau of Meteorology indicated that the surface wind in the area at the time of the accident was 090` magnetic at 15 knots. This information was confirmed by witnesses at the dam wall who observed white caps on the surface of the dam. The north/south channel of the lake was bounded on its east side by steep hills rising to 70 metres above water level. The effect of this high ground was to partially blanket the north/south channel from the easterly wind. The position of the wreckage was in the area where the wind shadow effect would have ended and where the wind would have blown at full strength along the main east/west channel of the lake. The crosswind limitation for the aircraft as stated in the flight manual was 8.7 knots. Commenting in early 1988 on an enquiry regarding the raising of this limit, the aircraft manufacturer emphasised the 8.7 knot limit and advised that any test work to raise the limit should proceed cautiously starting at or below the current (8.7 knot) limit. If the aircraft was conducting crosswind operations in the north/south channel, and suddenly encountered a 15 knot crosswind on exiting the wind shadow area, the control difficulties confronting the pilot could have been significant. The aircraft wreckage was intact except for the floats which had been torn off by water impact forces. The right float was severely damaged while the left was intact. The forward tip of the right float had been severed by the propeller. The remaining forward section had then been forced upwards and outboard and had broken off. This weakened the float support structure, causing it to fail, and allowing the remaining section of the right float to strike the right side of the fuselage just aft of the cabin. Damage of this type an magnitude was most probably caused by the nose of the right float digging into the surface of the lake at relatively high speed. For this to occur, the aircraft was banked to the right at float impact - a possible consequence of encountering a strong crosswind from the left. There was no evidence that the aircraft had hit a submerged object.

After landing in a sheltered gully, the pilot became concerned that the retrieval crew might not have access to the area. He therefore elected to proceed to another area about 3 kilometres away. At this location, a landing was carried out in 10 knot wind conditions. The basket made a hard flat contact with the ground, before being pulled over on its side by the deflating balloon canopy and the wind. Because of the possibility of the balloon making contact with a fence during the landing, the pilot had instructed all passengers to squat below the edge of the basket, which possibly made their stance for the landing unstable. One passenger received a fractured ankle when her leg twisted under her as the basket rolled over.

Circumstances:

The pilot was conducting spraying operations in a large wheat paddock. The aircraft was being flown about two metres above the crop and the pilot intended to pass to the right of a large tree near the end of the particular swath run. The aircraft suddenly swung violently to the left as the wheels entered the crop. By the time the pilot managed to pull the aircraft clear, it was heading for the tree. While attempting to manoeuvre the aircraft, the pilot was unable to prevent it from striking the ground.

Significant Factors:

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

1. Contact with the crop on spray run, reasons undetermined.

2. Aircraft struck the ground during pilot attempt to avoid a tree.

The aircraft had been engaged in spraying cotton fields in generally turbulent flying conditions. Power lines crossed one end of the area at an angle of about 20 degrees to the direction of the swath runs. At their lowest point, these wires were about 10 metres above the ground. The pilot reported that as he approached the power lines, intending to fly underneath at the lowest point, the aircraft ballooned upwards in turbulence. Despite corrective action the cockpit mounted wire deflector struck the lines. The deflector was broken and much of the fin and rudder was torn from the aircraft, which subsequently impacted the ground about 800 metres from the power line.

Circumstances:

The pilot reported that the engine run up checks were normal, with the engine operating for about ten minutes before the take-off was commenced. During take-off, no anomalies were noted by the pilot, however, at about 100 feet the engine lost nearly all power. The pilot attempted to turn back in order to land on the strip. During the turn, control was lost, and the aircraft struck the ground. The area beyond the strip where the power loss occurred was mainly open farmland. The occurrence of a major power loss at low height gave the pilot little time to assess the situation. Inspection of the aircraft did not reveal any mechanical defects which might have caused the engine power loss. The pilot had been using a mixture of Avgas and unleaded motor fuel. This aircraft type was not approved to operate using automotive fuels. Atmospheric conditions were conducive to the formation of significant carburettor ice under all engine power conditions. The use of automotive fuel may have increased the possibility of this occurring. Inspection of the stall warning system revealed that the screws securing the connections to the wing mounted vane assembly were loose, and the system had been inadequately maintained. It was likely that the system was not operating at the time of the accident.

Significant Factors:

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

1. Conditions conducive to carburettor ice formation.

2. Use of non-approved fuel.

3. Engine power loss at a low height.

4. Pilot attempted to turn back to land on the strip from too low an altitude.

5. Poor condition of the stall warning system.

6. Pilot did not ensure adequate airspeed was maintained.

Circumstances:

While taxiing after a normal landing, a rumbling noise was heard from the vicinity of the nose gear, the hydraulic low-pressure light illuminated, and nose gear steering authority was lost. The right hand nosewheel had separated from the aircraft due to fracturing of the axle. As the nosewheel departed it damaged the nose gear uplock assembly with consequent loss of hydraulic system integrity. It then continued under the fuselage causing skin damage. The nosewheel axle was recovered and subjected to metallurgical examination which showed that the fracture was due to fatigue. The fracture resulted from prior long term fatigue cracking which occupied approximately 75 of the cross sectional area of the axle. Stress corrosion cracks were present which were the most likely initiator of the fatigue cracks. A mandatory crack inspection requirement called up for this axle did not cover the specific area in which the stress corrosion was located. Consequently, during the axle refurbishment, the stress corrosion cracks were covered by a layer of electroplated chromium. Upon advice of the failure mode by the Bureau, the operator carried out an inspection of all Inservice and spare axles, to remove any axles with stress corrosion under the electroplated chromium.

Significant Factors:

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

1. The nosewheel axle failed due to fatigue initiated by stress corrosion cracks.

2. The recurrent Non Destructive Inspection for the axles does not address the area where the stress corrosion occurred. Consequently, pre- and post- refurbishment inspections did not detect the cracks.

Recommendations:

1. The Civil Aviation Authority consider extending the current mandatory Non Destructive Inspection for the axles, to address the area discovered in this accident.