Circumstances:

The pilot reported that he had made a normal landing on the grass runway 14. The wind was a light crosswind from the left. During the ground roll the aircraft began to swing to the left. Application of right rudder was not effective, and the aircraft ground looped to the left. During the ground loop the right hand gear leg broke off and the right wing contacted the ground. At the time of the accident there was a thunderstorm developing nearby and strong thermal activity was reported in the circuit area by another pilot. The loss of directional control was probably caused by a sudden wind gust associated with the unstable local conditions.

During a landing on a golf course, an elderly lady passenger sustained a fractured leg as she had not taken up the correct landing position. The pilot reported the landing was conducted in suitable weather conditions and that the rate of descent was not excessive.

Circumstances:

Seven days prior to the accident a new propeller was fitted to the aircraft after which two brief test flights were made. The aircraft was not flown again until the accident flight. Witnesses reported that on the day of the accident the pilot had been flying the aircraft for about 20 minutes. He was proceeding in a westerly direction at an altitude of about 100 feet above the ground when the rotor blades appeared to disintegrate. The propeller had in fact come off its mounting and hit one of the rotor blades. The rotor blade was destroyed and the aircraft dived to the ground. Subsequent investigation showed that the six bolts securing the propeller to the hub assembly had failed. The propeller was secured to the hub assembly with a compression plate on either side of the propeller hub to distribute the compression loads from bolt tension over a large area of the hub. The plates had been coated with black paint which had allowed slippage to occur between the propeller and the hub plates. This resulted in the inability of the hub assembly to achieve successful engine torque transfer through friction. The torque transfer was achieved through the bolts only which failed in bending.

Significant Factors:

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

1. Inadequate engineering design in that the propeller was attached to its mounting in a manner that resulted in the drive being transferred to the mounting bolts.

2. Failure of the mounting bolts, which led to the separation of the propeller.

Recommendations:

1. It is recommended that the Australian Ultralight Federation and the Australian Sport Rotorcraft Association advise their members of the CAA Airworthiness Advisory Circular - May 1987, Item 187-1 addressing the basic principles and conditions of engine torque transmission to wooden propellers.

Circumstances:

The glider was lined up short of the normal launch point. During the winch launch the wing-walker apparently released the into wind wing early. The wing dropped and the glider veered into the gusting crosswind. The pilot abandoned the launch however the glider continued to weathercock and ran into the retrieval vehicle before being brought to a halt.

It was reported that the pilot was confronted with bad weather and elected to land on a beach. The aircraft touched down in an area of soft sand and nosed over.

During the take off run, on the open sea and just prior to lift off, the right engine suffered a total failure. The pilot was unable to maintain directional control, due to the prevailing conditions, and the aircraft finally stopped on a sandbar. The left hand float, float pylon and outboard three metres of the left wing were torn off during the deceleration. A strip examination of the failed engine revealed that there had been a failure of the compressor turbine section following a sulphidation attack which initiated a fatigue failure of the compressor blades. The compressor turbine was inspected 279 hours prior to the failure and sulphidation was detected at that time, however, the damage was recorded as being within acceptable limits. The engine manufacturers recommend that the engine be washed daily and that 200 hourly borescope inspections be carried out for signs of sulphidation on the blades. The operator washed the engine daily, however, a borescope inspection was not carried out during the period between the compressor turbine inspection and the engine failure. A borescope inspection 79 hours prior to the engine failure would probably have disclosed the advanced state of blade corrosion.

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.