Wirestrike

Circumstances:

The pilot reported that he was aware of the location of the three-cable powerline during his spray runs. He had completed three runs under the line and was conducting a clean-up run at the opposite end of the paddock when he collided with the wires during a pullup. The wire deflector snapped, and the top of the vertical stabilizer and rudder were torn off. The pilot was able to land the aircraft safely. He indicated that he had forgotten about the location of the line when he moved to the other end of the paddock and it was no longer necessary to fly under them.

The pilot carried out one spray run at about 10 feet above the ground in an easterly direction over his own barley crop. The weather was fine with a north-easterly wind of about three knots. The area was very open with large, slightly undulating paddocks. About 40 metres beyond a fence marking the end of the spray run, the left wing struck a single strand power line about 18 feet above the ground. Without breaking, the wire severed a small portion of the upper surface of the wing, near the wing tip. Impact marks on the leading edge of the wing indicate that the aircraft was banked about 30 degrees to the right when it struck the wire. The wire was pulled off three adjacent poles which were about 400 metres apart. The aircraft collided with the ground inverted and nose first about 80 metres beyond the wire. At ground impact there was negligible ground slide. The engine partially dislodged from the airframe and the cabin was partially crushed. The sliding canopy slid open and the home-made hopper ruptured. An estimated 100 litres of herbicide spilled from the hopper. The pilot was not a trained, approved, agricultural pilot. The aircraft was not approved for agricultural operations, nor was the hopper installation. The wire was difficult to see because of the large distance between poles.

Circumstances:

The pilot was familiar with the area and had been given instructions by the property owner that he was to fly spray runs parallel to rows in the crop. The pilot misinterpreted these instructions which resulted in him flying parallel to the eastern boundary of the area rather than the western boundary. He then became partly disoriented with respect to the position of a single wire power line. The right wing of the aircraft struck the wire and the outer 120cm of the leading edge of the wing was lost. The rudder was also damaged by the wire. The pilot was able to retain control of the aircraft and landed without further incident. The pilot reported that the early morning light conditions were less than ideal for seeing wires.

Significant Factors:

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

1. The pilot did not clarify the instructions he was given.
2. Visibility was limited because of the early morning light conditions.
3. The pilot did not see or avoid the wire.

The pilot was contracted to spray three areas of sorghum of 160, 200, and 44 acres on adjacent properties. He was not familiar with the areas. The owner of the 44 acre area had arranged his spraying through his neighbour who owned the larger areas. The owner of the larger areas spoke to the pilot by telephone about his and the 44 acre areas. However, he spoke in detail only about his areas and the directions the pilot should follow to locate them from the air. The pilot was given a comprehensive briefing by radio by the property owner of the larger areas when he arrived overhead before he began spraying. This briefing included detailed information on power lines in the immediate vicinity of the areas. Mention also was made that one of the power lines continued through the property containing the 44 acre crop. The pilot completed spraying of the larger areas and was then told to follow a road to the property containing the 44 acre area. Radio communications between the owner of the 44 acre area and the pilot were difficult because of intermittent transmission problems with the property owner's radio. Nevertheless, the information about which contours were to be sprayed was passed to the pilot. There was no reference to power lines by either the pilot or the property owner during this exchange. The contours to be sprayed curved from a south-easterly through to a westerly direction. A single power line ran approximately east-west along the extreme southern edge of the contour area. Immediately beyond the power line was an area of tall trees. The pilot began spraying north-east/south-west and completed about three quarters of the task with runs in this direction. To spray the final southern-most section of the crop, the pilot changed the direction of his runs to approximately north-south. As the aircraft pulled up at the completion of the second run, it suddenly rotated to a near 90 degree nose-up attitude. The nose then pitched forward and the aircraft entered a steep dive to the ground, coming to rest inverted and bursting into flames. The power line across the southern edge of the crop had been severed. Marks were found on the right main landing gear leg of the aircraft indicating that the wire had contacted the leg some 30 cm above the wheel and then slid down the leg, possibly becoming entangled in the wheel before breaking. The aircraft impacted the ground 123 metres beyond the wire. No fault was found with the aircraft or its systems which might have contributed to the accident. The wire and poles were not hazards for the initial north-east/south-west runs. For the final run, the pilot would have had to pull up early, i.e. before the end of the crop, to avoid the wire. The pull-up appears to have been made in relation to the trees beyond the crop rather than the wire. The single pole which might have warned the pilot of the presence of the power line was of natural colour and against a background of tall trees. It was to the right of the flight path and therefore not in his direct field of view.

It was after sunset when the pilot was doing clean up runs after spraying a pea crop. Sufficient light remained to complete the job, however the pilot had the floodlights on. The spray runs had been in a north/south direction but the clean up runs were made east/west. A powerline ran obliquely through the paddock in a southwest/ northeast direction. A smaller SWER line ran south from the main line, above the eastern fence of the paddock. After turning west to fly along the southern fence of the paddock, the aircraft struck the SWER line. The pilot advised that he had known of the presence of the two powerlines. He had temporarily forgotten about the smaller SWER line because he was concentrating on the main powerline that he had been avoiding all afternoon. He saw the SWER line, pulled up and thought he had missed it, but when he landed he discovered that one of the floodlights was missing. The distance between powerpoles was 100 metres with a minimum clearance of 5.5 metres from the top of the fence. The aircraft struck the SWER line 40 metres from the nearest pole.

Circumstances:

The aircraft was engaged in spraying herbicide. The particular paddock being sprayed consisted of several north/south oriented strips. Earlier in the day the pilot had sprayed the strips in the western section of the paddock. A powerline ran approximately east/west across the northern boundary of the area being treated. The spray runs were aligned south to north, with the aircraft pulling over the powerlines at the end of the northward runs. The pilot then departed to spray another area, with the intention of returning later to complete the small eastern section of the paddock. On return to the area about an hour and a half later, the aircraft was observed to make a spray run from south to north. At the end of this run, the aircraft collided with the powerline and dived to the ground some 180 metres further north. The aircraft had struck the powerline at a height of about ten metres above ground. Only one of the two conductors was broken. The aircraft had struck the cable with the outboard right wing and tail. Marks on the severed section of the right wing indicated that the aircraft was in an estimated 40 degree left bank at the time. The top of the fin and rudder were also torn off, and the fin and rudder were bent to the right, jamming the rudder.

Significant Factors:

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

1. Pilot failed to see or avoid the powerline.

2. Flight controls buckled/ jammed.

3. Pilot encountered unforeseen circumstances beyond his capability.

The pilot departed the treatment area as darkness fell, to fly the 15 kilometres to Ayr aerodrome. His loader/driver had left the agricultural strip earlier after the last load of urea fertilizer had been loaded into the hopper of the aircraft. He had directions from the pilot to deploy kerosene lights on one side of runway 11 at Ayr for a night landing. Immediately before the accident, the aircraft was seen to orbit a farmhouse three kilometres north-west of the threshold of runway 11. It was flying low with the spray lights ON, in a very intense thunderstorm. Heavy rain was falling at the time. The farmer saw the aircraft lights disappear to the south and at the same time the electricity supply was cut. Convinced that the aircraft had crashed, he drove to the area where he had seen it disappear. When he arrived at a crossroads, he saw downed powerlines and the pilot, whom he recognised, standing among them. The pilot was in shock and incoherent. The aircraft had struck 11,000 Volt powerlines at a major junction of the electricity grid. It had cartwheeled and came to rest, upright, in tall sugar cane, 100 metres from the intersection. The pilot holds a Class Four and a Five Instrument Rating which entitle him to fly at night in Visual Meteorological Conditions (VMC). However, the aircraft was certified for Visual Flight Rules (VFR) only. Weather at destination was such that VMC was not met and flight by visual reference was not possible. The pilot had decided to return to Ayr so that spray gear could be fitted to the aircraft in preparation for work on the following day.

The pilot reported that he was to spray a 17 acre crop of cucumbers. He had flown the area twice previously, and knew the hazards to be powerlines and stay wires from the power poles. The stay wires were the more difficult to see so he concentrated on locating these during his aerial inspection of the paddock. At the completion of his first run, which was along the western edge of the area, there were two sets of powerlines. The pilot had planned to fly under both sets but hit the second set as he pulled up from the run. He stated that he had forgotten about the second set of wires. Although the aircraft sustained left wing and aileron damage, the pilot was able to land safely at the operating landing area.

The pilot was engaged in the chemical spraying of several properties in the general vicinity of his own property near Gatton. After completing the spraying of two properties, the pilot began positioning the aircraft in order to spray his own crop. A witness observed the aircraft as it turned to the right and flew at low level beneath power lines across a highway. The aircraft was then seen to bank slightly to the right and strike another set of power lines on the opposite side of the highway. Two of the wires were broken and the third remained entangled with the aircraft. The aircraft struck the ground in an inverted attitude. The power lines struck by the aircraft had been erected about three weeks before the accident. They had been erected at the request of the pilot to service a portion of his property. He had flown under the wires on several occasions in the preceding three weeks.

The pilot was conducting aerial spraying on a banana plantation in hilly country. While flying a clean-up run along one side of a section of the plantation, the aircraft struck a set of powerlines which ran diagonally across its flight path. The wires became entangled in the main landing gear and were dragged 160 metres before the aircraft impacted the ground and caught fire. The cockpit area was burnt out and the engine compartment severely damaged by the fire. The engine and remaining aircraft structure and components were examined and, not withstanding the severe heat damage to some engine components/accessories, no abnormality was found. The pilot, who suffered serious burns, told a friend a short time after the accident that he was distracted by a sprinkler pole and had forgotten about the wires. In hospital two days later, the pilot reportedly spoke of experiencing elevator control problems shortly before hitting the wires. When he was able to be interviewed, some seven weeks after the accident, the pilot maintained that he felt the engine lose power as he was aligning the aircraft for the run and that the aircraft descended into the wires as a result. The nature and extent of the pilot's injuries indicated that trauma induced amnesia was unlikely to have caused his conflicting accounts of the accident. There are, however, unconscious pyschological mechanisms which can explain these conflictions. The banana plants were served by a large number of sprinkler poles of narrow gauge water pipes which protruded above the plant tops. Seeing these would have required considerable attention from the pilot. The power poles supporting the wires the aircraft struck were well outside the pilot's forward field of view and the wires themselves would have been difficult to see against the background of dark vegetation. However, the weight of human behavioural evidence leads to the conclusion that the pilot was probably distracted and forgot about the wires. The pilot reported that he was unable to open the left cockpit door by the normal or emergency method and had to egress through the right door where the fire was more intense. Both cockpit doors were open when the wreckage was examined. No reason was found which would have prevented the emergency exit from operating normally.