Wirestrike

The landing strip at Compressor Station 13 on the natural gas pipeline between Moomba field and Adelaide is situated in flat tree-less terrain and runs approximately north and south. Adjacent to the strip on the western side nine hundred feet from the northern end and 350 feet from the centre-line of the strip, stands a radio mast )00 feet high supported by an array of guy wires. The most easterly of the wires was anchored at a point 150 feet from the strip centreline and attached 25 feet below the top of the mast. The pilot had carried out a previous charter flight to the strip on 5 January, 1972. Prior to that flight he had been briefed by the operator's chief pilot and during the briefing it had been pointed out that caution was l necessary when operating at this strip because of the proximity of the mast and its supporting guy wires. The outward flight from Adelaide, earlier in the day, was uneventful and the pilot rested for several hours before taking off on the return flight. The take-off was made to the south in clear, almost calm conditions. Alter take-off the pilot made a shallow turn to the left at approximately 200 feet above ground level. At this height the pilot completed a left-hand circuit of the strip then flew south tracking some 250 feet west of the strip centreline in a shallow dive. The aircraft passed low over the heads of three persons who had farewelled the passengers. Three hundred feet further on, and with no apparent deviation from its previous flight path, the aircraft struck the most easterly of the radio maot guy wires at a point lid feet above ground level. The wire sheared off the outer a feet of the left wing leading edge and the aircraft immediately rolled to the left and pitched into a steep dive, striking the ground 400 feet beyond the point of impact with the wire.

The pilot intended to visit friends at a cottage close to the bank of the Ovens River. On previous trips he - had landed at Yarrawonga and had been driven to the cottage. On such visits he had inspected a paddock, to the west of his friend's cottage, with a view to its use as a landing site. The field was bordered by a row of SEC power wires, aligned north-south, just outside the eastern boundary and a further set of power wires, parallel to these, was located 135 feet to the west, inside the paddock. The wires outside the paddock were prominent by virtue of the number of supporting poles, but those within the paddock were less obvious as the wires were suspended across the approach path, between two poles 511 feet apart. A row of trees was located just inside and parallel to the western boundary and the distance between these trees and the wires in the field was about 2,800 feet. Arriving over the field after the flight from Moorabbin the pilot circled, sighting both sets of wires. With the intention of making a close inspection of the field and thus going around to make a landing he made a full flap approach towards the west. The aircraft cleared the eastern set of wires but the nose wheel leg struck and broke the top cable of the three wires comprising the second set. The aircraft then fell to the ground, nose first, from a height of about 30 feet and overturned.

At Bankstown, the pilot submitted a flight plan which indicated that the aircraft would cruise at 5,500 feet to Port Macquarie and then at 6,500 feet to Archerfield. Fuel consumption was shown as 8 gallons per hour and fuel on board the aircraft as 40 gallons. The time required for the flight was 237 minutes but, through a miscalculation, this was shown as 227 minutes. The pilot's normal operating procedure was to lean the fuel mixture only while cruising above 5,000 feet. After departure the pilot elected to cruise at altitudes between 2,300 and 3,000 feet and the mixture control remained selected to Rich. At Grafton, because of the weather ahead, the pilot diverted to a coastal route and this was expected to add seven minutes to the flight time. Whilst on descent to Archerfield, after some 242 minutes of flight, the fuel pressure indication dropped to zero and the engine lost all power. The pilot was unable to restore engine power so he advised Archerfield Tower of his predicament and decided to attempt a forced landing on the airport. About one mile from Archerfield, it became obvious to the pilot that he would not reach the landing area. He attempted to turn the aircraft sharply to the right for a landing on a suburban street, but whilst in the turn the port wing of the aircraft struck and severed power lines adjacent to the street. The aircraft then plunged to the ground, right wing first, and came to rest, severely damaged against a timber house. Examination of the aircraft revealed no evidence of pre-impact malfunction. Records of past flights with this aircraft and fuel consumption tests conducted subsequently indicated that by operating at the relevant power setting with the mixture correctly leaned a fuel consumption consistent with that appearing on the flight plan could be realised. When the engine was operated with the mixture in full RICH the fuel consumption was significantly higher and the engine failure had occurred after a flight time compatible with fuel usage at this higher rate. At the accident site, despite both fuel tanks having been punctured, there was no evidence of any significant quantity of fuel having been spilt. There was attached to the instrument panel an ambiguous placard of undetermined origin for converting the fuel contents indication to imperial gallons.

A section of road near Narrabri West had been marked for use as an emergency airstrip in connection with flood relief. This section, some 3000 feet in length, was obstruction free over a width of approximately 100 feet, the bituminous sealed road in the centre being 18 feet wide. At the southern end of the selected area a power line crossed the road, 28 feet above the surface, with one supporting pole adjacent to the western side of the road. A line indicating the strip threshold had been painted across the road 140 feet north of this position and a large Cross was painted on the road surface immediately below the power line. The steepness of the approach gradient had been recognised and a diagram of the situation was displayed in the pilot briefing room at Narrabri aerodrome. The strip was in constant use by light aircraft, but although the pilot had been engaged on flood relief for several days he had not previously landed at the strip. On this occasion the pilot sought information concerning the strip before departing Narrabri and he determined the location and length of the strip, but he has since stated that he was not aware of the presence of the wires. He flew across the emergency strip at about the mid point and joined left downwind for a landing from the south, approaching over the wires. The approach was lower than that made by other aircraft and the nosewheel assembly contacted the wires. The aircraft struck the ground in a steep nose down attitude, 116 feet from the power lines and 24 feet short of the strip threshold.

The pilot had flown various Cessna types of aircraft but his experience on the Cessna 177 type was limited. The Cessna 177 differs from the other types which the pilot had flown in that it has a fuel shut-off selector located near the carburettor heat control. After taking off from an authorised landing area on the property of one of his passengers the pilot decided to land in another nearby field. At about 500 feet on final approach he selected what he thought was carburettor heat and shortly afterwards there was a complete loss of engine power. He then prepared to make a forced landing into a nearer field and during a subsequent cockpit check found that he had inadvertently operated the fuel shut-off instead of the carburettor heat. The fuel was selected on, the engine re-started and the pilot applied full power with the intention of abandoning the landing. The nose leg then struck and was damaged by a power wire of which the pilot was not aware. The aircraft was landed straight ahead and the nose leg collapsed when it contacted the ground.

The weather was fine with a light breeze and occasional slight turbulence. The pilot, who held a first-class agricultural rating, made preliminary inspections of the area both from the ground and from the air, but did not accurately establish the position of overhead wires and other features. He decided on a broad spraying plan which he intended to develop as the operation progressed. The main section of the undulating terrain was treated by making runs in a single direction during which the aircraft passed beneath a primary power line approximately 40 feet above ground level. The pilot then commenced a run in the opposite direction to cover a small section which remained. While on the approach to this final run the pilot selected a fence as the point at which he could begin his climb away. He believed he would then have passed safely below both the primary power line and a spur line which ran to a nearby house. The spur line was in fact some 90 feet beyond the fence and as the aircraft climbed away it struck the wire and became inverted. After continuing out of control for a short distance the aircraft struck a group of telephone wires then continued on its descending path and made violent contact with a road. There was no outbreak of fire and the pilot was able to release himself from the wreckage.

The weather was fine with a light breeze and occasional slight turbulence. The pilot, who held a first-class agricultural rating, made preliminary inspections of the area both from the ground and from the air, but did not accurately establish the position of overhead wires and other features. He decided on a broad spraying plan which he intended to develop as the operation progressed. The main section of the undulating terrain was treated by making runs in a single direction during which the aircraft passed beneath a primary power line approximately 40 feet above ground level. The pilot then commenced a run in the opposite direction to cover a small section which remained. While on the approach to this final run the pilot selected a fence as the point at which he could begin his climb away. He believed he would then have passed safely below both the primary power line and a spur line which ran to a nearby house. The spur line was in fact some 90 feet beyond the fence and as the aircraft climbed away it struck the wire and became inverted. After continuing out of control for a short distance the aircraft struck a group of telephone wires then continued on its descending path and made violent contact with a road. There was no outbreak of fire and the pilot was able to release himself from the wreckage.

The pilot, who was the general manager of the irrigation property on which the accident occurred, and his passenger, who was the farm manager of the same property, were on an inspection flight to observe accumulations of water from recent rain. The aircraft circled and manoeuvred over various sections of the property at a height of about 500 feet for approximately fifteen minutes and was then seen to make a shallow descent towards the homestead buildings. It flew towards a position where two employees were working adjacent to the property workshop and at a height of some 28 feet while still approaching the workshop area, it struck power cables. The forward movement of the aircraft was retarded, it nosed up steeply, then rolled to the left and dived to the ground steeply nose down. Several seconds after impact, the aircraft burst into flames and was completely destroyed by fire.

The flight was undertaken to provide some "unofficial" dual instruction towards endorsement of the type on the licence of the pilot under training. The aircraft was of the dual tandem cockpit type and communications between the two pilots was by means of voice tubes. At a low level during the approach for a practice forced landing the pilot-in-command took over the controls, adjusted the power and levelled the aircraft. He states that he then handed back control to the trainee pilot and accepted that the latter had control although he did not receive the usual response, "taking over". The trainee pilot states that he understood that the pilot-incommand continued to have control of the aircraft. The aircraft continued to fly in a wide shallow left turn at a low level and although each pilot thought that the other had control, each momentarily moved the controls to avoid an unsafe situation. Neither pilot observed that the aircraft was converging with a set of three power lines with which it ultimately collided. The wires did not break but the aircraft was flung sideways striking the ground with the port wing tip and rolling on to its back. There was no fire and the trainee pilot was able to vacate the rear cockpit unaided. He assisted the pilot-in-command to vacate the front cockpit.

After receiving a sketch plan of the area to be sprayed, the pilot made an aerial inspection and noted the position of power lines. He then made nine spraying runs which involved pulling up over a power line which crossed the paddock approximately one third of the distance along the spray runs. On the tenth spray run the pilot allowed his attention to be temporarily distracted through watching a marker change to a corrected position. When he again gave his attention to the flight path he became aware that the power line was immediately ahead and at the same height as the aircraft. He attempted to climb the aircraft, but the wires became hooked on the tail wheel assembly. The aircraft decelerated rapidly and contacted the ground on the port main wheel and wingtip. The power lines did not break, but three of the wooden supporting poles were pulled to the ground.