The pilot reported that while cruising at about 350 feet above ground level, the engine began to run roughly to the extent that he was unable to maintain height. In the subsequent landing, the aircraft struck a tree, cartwheeled, and was extensively damaged. The spark plug in one of the engine's two cylinders was fouled by carbon deposits.

Circumstances:

The pilot reported that on arrival in the circuit area he noticed that the wind was from the north-east at 20 to 25 knots. As the wind was mostly crosswind he elected to land uphill on strip 28, which is 920 metres long. Shortly after landing the pilot became aware that the aircraft was not slowing down normally. Heavy braking was used to little effect. The engines were shut down, and the aircraft ran off the end of the runway. Some fallen logs caused the nose gear leg to collapse. The Cairns meteorological office estimated that the wind would have been 10 to 12 knots from the east to the south-east.

Significant Factors:

The following factor was considered relevant to the development of the accident:

The pilot landed with an excessive tailwind component.

The pilot was carrying out a series of aerobatic manoeuvres when the propeller separated from the airframe. A forced landing was carried out in a suitable paddock. The pilot then noted that one wing had sustained damage from the departing propeller. The evidence available indicates that the propeller fell from the aircraft when the remaining five of the six propeller retaining bolts failed as a result of fatigue cracking and overload. The sixth bolt was not found but lack of marks on the crankshaft flange indicate that it had fallen out prior to failure of the other five bolts. All bolts were in place and secured with lock wire prior to take off. CAA Airworthiness Directive AD/PEP/1 AMDT 2 addresses a known problem which relates to propeller wood shrinkage and loosening of the retaining bolts. The directive recommends special checks on the propeller bolt torque in certain circumstances. The propeller was fitted to the aircraft in Victoria, in a cool moist environment, and the aircraft was then transferred to Perth and operated in a warm dry environment. This change in environment is one of the circumstances set out in the airworthiness directive. No evidence was found to indicate recent compliance with the directive. It is probable that shrinkage of the propeller wood caused loosening of the propeller retaining bolts. The loose bolts were than able to "work" eventually resulting in the failure of the lock wire and loss of one bolt and the failure of the other five bolts.

The pilot was carrying out a "cleanup" swath run on a 50 acre potato crop which he had sprayed on the previous evening, but had not finished due to poor light. The cleanup run was conducted below a power line at right angles to the flight path and about eight metres above the crop. This power line was near another line which traversed the crop, and was at an angle of about 30 degrees to the flight path. The pilot was aware of the location of the second power line and had intended to fly over it after pulling up from the run under the first line. The run under the first line was completed, and when the pilot began to pull up, he noticed that the second line was closer than he had expected, and he decided to go under instead of over the line. During the manoeuvre, the right wing contacted the 3 strand 12 gauge steel wires, and the aircraft slid along the wires for some 200 metres before cartwheeling into the crop tail first. The aircraft then bounced upright and caught fire. The right wing had been severed by wire contact outboard of the wing strut supports prior to ground impact and the pilot had been sprayed with fuel. The pilot received burns to his right arm and left leg. He was wearing leather gloves, a short sleeved shirt and shorts under polyester and cotton overalls. He also wore a helmet. Despite the fact that the helmet was damaged during the accident sequence the pilot received no head injuries.

Until the day prior to the accident the pilot had not flown for over three months. He was carrying out a period of touch-and-go landings. On about the third or fourth landing the aircraft was apparently caught in an area of sink at the approach end of the strip, and touched down in a flat attitude and bounced slightly. The aircraft was recovered and touched down again in a normal attitude. The pilot lowered the nosewheel onto the strip, then applied power to go-around. The aircraft was observed to become light on the mainwheels and commence a swing to the left. As the swing increased the right wingtip hit the ground and the nosegear leg broke off. The aircraft slid to a halt on the mainwheels to the left of the flight strip.

During mustering operations, the helicopter was landed near a fence which had to be opened to allow cattle through. The stockman who was to open the fence required a pair of pliers from the helicopter. As the pilot threw the pliers, one handle caught in his coat sleeve, deflecting them upwards towards the main rotor. Despite the application of left cyclic control, the pilot was unable to prevent the pliers being struck by, and causing substantial damage to, both main rotor blades. This accident was not the subject of an on-site investigation. The relevant information was provided by the pilot of the aircraft.

Upon arriving in the area to be sprayed, the pilot carried out an airborne inspection and located the obstacles, including a powerline beside a road just outside the eastern boundary. Three wheat paddocks adjoining each other were to be sprayed. The first spray run was about one and a half kilometres long in an easterly direction. During the run the pilot concentrated on the drift of the herbicide spray and forgot about the power line. He saw the wires a split second before impact. The aircraft struck the north/south power line and severed one of three wires before crashing inverted into the ground about 80 metres beyond the road. Weather conditions at the time were fine and ideal for spraying. This accident was not the subject of a formal on scene investigation.

Circumstances:

On final approach, the pilot observed that the single gear down light (green) was illuminated. Following a smooth touchdown near the threshold, the aircraft rolled along for about 150 metres before the pilot noticed the left side of the aircraft had settled lower than normal. Suddenly the aircraft veered uncontrollably to the left and struck a T vasis light box before coming to rest with the main gear partially collapsed. Post flight inspection revealed that the main landing gear had not been fully extended. Examination of the landing gear system revealed no evidence of pre existing failure or damage. The gear collapse was evidently the result of inadequate maintenance and inspection of the system. This had allowed the gear down light to be illuminated when the maingear had not been locked in the overcentre position.

Significant Factors:

The following factor was considered relevant to the development of the accident:

1. Inadequate maintenance and inspection of the landing gear system.

The pilot had completed his last spray run and had pulled up into a procedure turn to make a clean-up run. He was aware of two power lines, one running parallel to the spray run and the other at an angle to the first. He was intent on avoiding the line at an angle to his run but struck the other as he positioned for the clean-up run. Visibility at the time was reduced in light rain. The line hit the right wingtip and windshield wirecutter. Thw wirecutter bent under the load and the wire broke the windscreen and tore off the top of the cockpit before it separated. The pilot was able to recover the aircraft without further damage.

The pilot was to land the helicopter in a clearing which was some 80 metres in diameter and surrounded by trees up to 20 metres tall. He conducted a 40 knot power check some 200 feet above the trees and concluded that he would be able to hover the aircraft out of ground effect with 1-1.5 inches Manifold Air Pressure (MAP) margin. The helicopter was landed in the clearing without incident. To depart the clearing one hour later, the pilot set 31" MAP/3100 rpm (full power is 32" MAP/3200 rpm) and climbed the helicopter at about a 60 degree angle. He reached tree-top height and had just started to accelerate the aircraft when it began to settle. The pilot immediately applied full power and full collective pitch but was unable to arrest the descent. Although the engine rpm decayed to below 2500, the pilot was able to manoeuvre the helicopter into a confined area and land adjacent to a creek bed. Just prior to touchdown, the main rotor blades hit the trunk of a dead tree. No fault was found with the helicopter which might have contributed to the accident. The pilot had limited experience in high weight operations into confined areas. The pilot described the wind as light but varying substantially in direction at times. The power check conducted by the pilot would have been valid only if conditions at takeoff were exactly the same as those existing at the time and place of the check i.e. 200 feet above the tree tops and one hour before the accident. There is no guarantee that conditions were the same and 1-1.5 inches MAP was not sufficient buffer in the circumstances to ensure safe operations. By climbing at 60 degrees, the pilot was committing himself to the takeoff without any fall-back option. The correct technique required the helicopter to be climbed vertically in a "towering lift" type DEPARTURE.