Spraying runs were being conducted over a paddock which had power lines along one boundary. The pilot had been passing beneath the lines during each run, however after completing about two thirds of the task the wire deflector on the aircraft snagged and broke the powerline. The pilot carried out a precautionary landing and discovered that the rudder of the aircraft had been substantially damaged by the wire strike. At the point where the wire strike occurred there was less clearance between the wires and the ground than that available during previous swath runs. The pilot was aware of the situation, but had been subject to a visual illusion, which had led him to believe that there was sufficient clearance to allow the aircraft to pass beneath the wires. By the time he realised that the clearance was insufficient he was unable to take avoiding action, and had elected to allow the wire to strike the deflector, rather than risk the landing gear contacting the ground. The anti-snag deflector plate on top of the rudder had failed, allowing the wire to contact the rudder. The upper portion of this component had then been torn from the aircraft.

The flight was intended to provide familiarisation for the pilot on the aircraft type. After loading water into the hopper the pilot took off and carried out a series of turns before positioning for a spray run along one of the flight strips. At the end of the run the aircraft pulled up steeply and began banking to the right. It then appeared to enter a spin to the right and subsequently struck the ground in a steep nose-down attitude with little forward speed. The pilot had been instructed to load 100 gallons of water for the purpose of this exercise. Unsupervised, the pilot loaded 200 gallons of water which resulted in the aircraft being operated at the maximum all up weight approved agricultural overload. It subsequently stalled in a procedure turn at a height from which the pilot was unable to effect recovery before impact with the ground.

The pilot was conducting spraying operations on a pea crop. Swath runs were being made at right angles to a power line and low trees which were located just beyond the end of the crop. On the final run, the aircraft was flown beneath the power line, but the right wing then struck the top branches of a dead tree. The aircraft was seen to climb to about 200 feet, before descending steeply and striking the ground some 370 metres beyond the point of collision with the tree. A fierce fire broke out on impact and engulfed the wreckage. Previous swath runs had almost certainly been made with the aircraft passing above the power line. The reason the pilot chose to fly under the line on the final run could not be established, as there appeared to be no operational reason for this course of action. Expert opinion indicated that after passing below the line, a collision with the tree was virtually inevitable.

The pilot undergoing the check flight had completed a helicopter instructor course about two months earlier and had not flown this helicopter type for nine years. He was being checked for future employment as a Grade 2 helicopter instructor. The early part of the flight was conducted in the training area where various types of circuit and approaches were carried out satisfactorily. On return to the aerodrome the instructor demonstrated an autorotation to touchdown. The pilot under check then conducted two autorotations to touchdown. The instructor reported that during the touchdown phase on the second landing the other pilot applied excessive collective control. He attempted to correct the situation but was physically unable to prevent the other pilot from raising the control. Rotor rpm decayed excessively and the tail boom was severed in the ensuing hard landing. The pilot under check was experienced on another type of helicopter requiring a different landing technique from this one. He was also not used to having another pilot making control inputs and did not give precedence to these inputs. The instructor had evidently made no verbal comment to the other pilot that he was applying corrective inputs to the controls.

Before take-off the pilot had been briefed on the operation of the aircraft by the owner. The owner had suggested the pilot make a short flight along the strip or that if he had the "feel" of the aircraft he could complete a circuit before landing. After becoming airborne the aircraft initially flew about 25 feet above the strip before entering a shallow climb. At a height of between 100 and 150 feet the engine noise suddenly ceased and pieces of the propeller were observed falling from the aircraft. The aircraft continued straight ahead for a short time before commencing a turn to the left. During the turn, the left wing and nose dropped and the aircraft struck the ground in a steep nose down attitude. Inspection of the wreckage revealed that one of the three propeller blades had disintegrated. The blade had failed due to the progressive propagation of spanwise splits along its length. Similar spanwise splits were also found in the other two blades. The splits were found to have originated from radial cracking at the hub of the blade which had been caused by local overstressing of the wood in the area of the blade retainers. Also, the widely spaced power strokes of the four stroke engine fitted to the aircraft would have contributed to the spanwise splitting of the propeller blades. The propeller manufacturer does not recommend the use of this type of propeller with the engine fitted to the aircraft. No other defects were found with the aircraft that could have contributed to the occurrence. Following the propeller failure, the pilot inadvertently stalled the aircraft while attempting to manoeuvre it for landing.

The pilot hovered the helicopter at about 20 feet above ground, in front of cattle, in an attempt to head them off. He became aware that an uncommanded descent had commenced and almost immediately the Low Rotor RPM Warning Horn sounded. He lowered the collective control in an attempt to regain control of the rotor rpm, however, the main rotor blades hit several small trees. A heavy landing resulted during which the tail boom was cut off by the main rotor and the skids were spread. The helicopter remained upright. At the time, the temperature was about 32 degrees Celcius the helicopter was hovering into a 15 knot wind. With the helicopter some 50 kilograms below maximum gross weight and a density altitude of 3000 - 3500 feet, an out of ground effect hover was within the machine's capability. However, the pilot said that he required maximum power to hover the helicopter. It is possible that the wind conditions changed momentarily, unnoticed by the pilot, or that during manoeuvring the power requirement exceeded the maximum available. The machine was flying at too low an altitude to allow a controlled recovery from an over-pitch situation. This accident was not the subject of a formal on scene investigation.

The pilot had landed and was taxying into the parking area on a slight down slope. He became aware that he had misjudged his distance from a fence post and applied a burst of power in an attempt to turn the aircraft and avoid the post. The lower right wing struck the post, causing the main spar to break. This accident was not the subject of a formal on-scene investigation.

The pilot reported that he was turning the helicopter at low level when he was confronted by trees which were higher than he thought. He had to manoeuvre the helicopter harshly to avoid the trees and in the process overpitched the main rotor blades, causing a loss of rotor RPM and thus helicopter performance. As the pilot attempted to land the helicopter in a cleared area, the tail rotor struck a fence. The helicopter yawed left, contacted the ground heavily, and came to rest lying on its side. This accident was not the subject of a formal on-scene investigation.

The company chief pilot, who holds an Agricultural 1 Rating, accompanied the pilot on the ferry flight. They surveyed the paddocks to be sprayed from the air before landing at a nearby agricultural strip where they discussed the order of work with the farmer and studied a local map. The pilot prepared a diagram of the paddocks and plotted wires and obstacles. The aircraft was then loaded with liquid chemicals and the pilot sprayed the first paddock while the chief pilot remained at the airstrip. Weather conditions were a light south westerly wind, with excellent visibility. After spraying the first paddock, the aircraft was reloaded. The pilot circled the second paddock before flying a spray run in a southerly direction between a highway and a railway line. During the run the pilot glanced at the boom pressure gauge and adjusted the setting. As he approached the railway line he commenced a pull-up during which the undercarriage struck a railways communications wire. The wire was about 4 metres above the ground and ran parallel to and just north of the railway line. Realizing that the aircraft had caught a wire, the pilot commenced a gentle, left turn starting at about 50 feet above the ground with the intention of landing as soon as possible in a safe area. During the turn, because of the drag of the wire, the aircraft vibrated and lost airspeed, despite the application of full power. After the turn the aircraft stalled from about 20 feet with wings level. The aircraft struck the ground in a slightly nose-low attitude and slid for 42 metres before coming to rest south of the railway line. Approximately 140 metres of wire was found trailing from part of the spray boom which had detached from the left wing and was located 5 metres behind the aircraft. The communication wires about 10 metres north of the railway tracks were the only significant obstruction near the crop. The steel poles supporting the wires were spaced reasonably close but the spray run was midspan such that the poles did not assist depth perception. The pilot could see the wires ahead at the end of the run. The wires were too low for the aircraft to fly beneath. It was the pilot's intention to fly over the wires. The pull-up was late and too shallow. The pilot had been given 17 hours flight training under close supervision by his employer immediately before commencing operational flying. At the time of the accident he was flying in a suitable area for an Agricultural 2 rated pilot with low experience.

Circumstances:

When nearing its destination after a flight of about three hours, the helicopter struck a set of power lines, eight metres above ground level, spanning a ridge line. Witnesses described flight path as "quite low and fast" compared to other helicopters they had observed approaching the Airport. Examination of the wreckage revealed wire strike damage to the upper surface of one blade, suggesting that the helicopter was in powered forward flight when it contacted the wires. A test run of the engine found it to be capable of normal operation.

Significant Factors:

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

1. The pilot crossed the ridgeline at low level.

2. The pilot did not see or avoid the power line. This accident was not the subject of an on-scene investigation.