Wirestrike

The pilot reported that during a steep approach to the landing area at Turtle Cove Resort, he heard a loud bang at approximately 250 feet followed by airframe vibration. A precautionary landing was made on the beach. Inspection of the aircraft revealed damage to two rotor blades, and after speaking to witnesses he realised that he had struck a power line.

The pilot said he had landed at the resort before but had not approached from this direction. He believed he had passed over the wires, but they were closer to the resort than he had anticipated. The pilot was not injured.

The pilot had been landing to the north on the agricultural strip. Because a 10 knot south-westerly wind had developed he decided to land to the south. On short final the aircraft landing gear caught in a power line which the pilot had not seen. The nose pitched down and the aircraft struck the ground very heavily and cartwheeled.

The aircraft was severely damaged. The pilot had sighted a power line, aligned east-north-east, from a house to a post. Another line, the one not seen, ran east-west from the same post, with the next pole out of sight among trees.

Significant Factors

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

1 The procedures adopted by the pilot did not detect the presence of the power line.

2 During the landing approach the aircraft landing gear caught on a power line not seen by the pilot.

The pilot was conducting spray runs parallel to an electrical power transmission line. During one run the aircraft collided with a feeder line at 900 to its track. The collision damaged the rudder and vertical stabiliser and although the aircraft remained airborne the pilot had difficulty with directional control. He did not attempt to jettison the load. The pilot continued to fly the aircraft straight ahead until it approached a field that was suitable for a forced landing. During the attempted landing the aircraft was affected by a strong crosswind and the pilot was unable to prevent it from weathercocking into wind and colliding with some trees.

The pilot had been made aware of the main but not the feeder line. He had not noted the feeder line during his pre-application inspection, probably because the line was not visible against the dark background created by the crop. The pilot later indicated that, after the collision, he was reluctant to jettison the load as he was uncertain what effect the sudden loss of weight would have on aircraft stability. When the aircraft weathercocked into wind the damage to the rudder prevented him from being able to exercise sufficient directional control.

The aircraft was engaged in crop spraying operations. The spray runs were being conducted in a north-south pattern across the area which was intersected by a three-strand power line running east to west.

The pilot advised that due to the crosswind conditions, it was necessary to fly close to the power line on each pass to adequately control the spray pattern. On the sixth spray run, the main wheels struck the uppermost strand of wire, causing the aircraft to descend into the crop. The pilot was not injured in the impact and was able to exit the aircraft safely.

The pilot stated that on the last spray run he either misjudged the height of the wires, or the aircraft encountered a down draft in the lee of tall timber growing along the paddock boundary.

The aircraft was spraying thistles when the accident occurred. There were several areas to be treated on the property. The first area had been completed, and the pilot was flying the first swarth run on the next area when the aircraft hit a double wire powerline which culminated in a severe impact with the ground.

The investigation revealed that the pilot had been given a map of the property by the property owner. The map had two powerlines depicted but did not show the powerline that the aircraft hit. The span was reported to be about 450 metres, and the poles were remote from the point of impact. Prior to commencement of spraying the pilot made an aerial inspection of the area for powerlines and other hazards. He did not identify the powerline that the property owner had neglected to mark on the map.

Significant Factors

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

1. The pilot was not made aware of the existence of the powerline that he hit, and he did not see it during his aerial inspection of the property before commencement of spraying.

2. The span of powerline that the aircraft hit was about 450 metres and the poles were remote from the impact point, thus denying the pilot cues as to its existence.

Prior to departure the pilot rang the owner of the airstrip to get information on the strip and permission to land.  He was told that there were powerlines on approach to the 180 degree strip and the 090 degree strip.  He overflew the airfield on arrival and noted there was a light easterly breeze so decided to land on the 090 degree strip which has a published length of 910 metres in the AOPA directory.  The strip also has a displaced threshold which the pilot observed.

On final approach he noted that the strip seemed short.  The strip surface was grass, and the pilot thought it may have been wet.  He therefore slowed the aircraft and selected full flap while keeping power on, aiming to touch down as close as possible to the displaced threshold markings. Approaching the end of the strip the pilot believed he must have been past the powerline although he had not actually seen it.  He lowered the nose to touch down on the displaced threshold and at that point hit the powerline.  The aircraft then hit the ground heavily, sustaining substantial damage.

During the investigation the owner of the airstrip advised that the strip was 900 metres fence to fence.  Landing into the east there was 680 metres available due to the displaced threshold at the approach end.  After the accident the pilot said he noted that the powerline was in fact over the "turning area" at the approach end of the strip and the poles were some distance apart, remote from the final approach path.

The day after the accident the electricity supplier installed marker devices on the powerline.

Significant Factors

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

1. The pilot was warned about the presence of a powerline on the approach end of the strip he was using but did not ensure that he sighted it prior to making his landing approach.
2. Although he had not sighted the powerline, on short final approach he made an assumption that he must have passed it and so lowered the nose to touch down as close as possible to the displaced threshold markers.
3. The pilot "dragged the aircraft in with power" on a low final approach profile instead of flying a normal glidepath.
4. The powerline was not fitted with any warning marker devices.

The pilot reported that during the commencement of a spray run he noticed a power line in the flight path and pulled up to avoid the wires. The aircraft struck the wires but remained airborne and was flown back to Warwick and landed safely. The pilot said he was not previously aware of the power line, and it was not marked on the map given to him by the property owner. The aircraft damage was confined to the propeller and wire grazes on the right wing leading edge.

The pilot was conducting agricultural spraying operations on a 12 ha cotton crop. He said he had a good knowledge of the field and had sprayed it several times during the season. He was aware of two power lines running across the field and planned to fly under them. One powerline ran diagonally across the direction of the intended spray run.

After passing under this wire the pilot felt a vibration through the helicopter. Although it continued to fly in a straight direction, the helicopter would not respond to the pilot's control inputs. It then descended, entered the crop, and slid along the ground for 20 m before coming to rest.

The pilot assessed that he had maintained inadequate clearance from the powerline, and that the main rotor blades had brought the powerlines into contact with the tail rotor. The clearance below the wires was reduced by the fully grown cotton. The diagonal orientation of the wires and reduced ambient lighting may also have impaired the pilot's judgement of the available clearance.

The pilot planned to visit a friend and land in a paddock at his property. He noticed the wind direction and speed from wind patterns on the sea, then commenced a survey of the property to find a suitable landing area.

He noticed three power lines across the selected paddock but failed to see a fourth. He then descended from 500 ft above ground level (AGL) to 100 ft AGL for a better look at the intended landing area, then continued the descent to about 25 ft AGL to check the surface conditions. The fourth power line suddenly appeared across the path of the aircraft, and with no time to take avoiding action the aircraft struck the wire with the propeller and windscreen, causing it to pitch nose down and impact the ground.

The emergency locator beacon (ELB) activated and was heard by an overflying regular public transport (RPT) aircraft.

Circumstances

The pilot had arranged to visit the property of a friend in the Kingaroy area. He planned to arrive at the property at about 0900. At 0930, the pilot rang his friend and advised that he would not arrive until 1200-1230. The delay was the result of maintenance needed on the aircraft which required the pilot to fly the aircraft to Caloundra and return to Redcliffe before departing for Kingaroy.

The pilot and his passenger arrived at the property at about 1230 where they lunched and spent the afternoon. When it came time to leave, the property owner decided to accompany his friend in his own Lightwing aircraft for part of the return journey. They boarded their respective aircraft and the Lightwing became airborne and waited in the area for about 10 minutes for the Skyfox to become airborne. The pilots eventually gained radio contact with each other but the pilot of the Skyfox gave no reason for his delayed departure.

Both aircraft set course for Nanango and the Skyfox, which had been above and behind the Lightwing, overtook the other aircraft and they continued at about 2,000 ft above ground level (AGL). The pilot of the Skyfox then

descended his aircraft, followed by the Lightwing, to overfly an old airstrip at an altitude of between 10 ft and 20 ft AGL, before climbing to a reported 2,000 ft AGL. The Skyfox pilot then advised his friend that he was going to overfly another airstrip and descended. The Lightwing remained at altitude. During the descent the pilot of the Lightwing reported seeing a short then continuous stream of whitish smoke from the rear of the aircraft. He attempted to contact the Skyfox pilot by radio but received no response.

The aircraft was observed by a ground witness to complete two to three orbits of a property homestead before commencing a flypast over the homestead in a southerly direction. The witness stated that he did not observe any smoke from the aircraft. He then reported hearing the sound of the two powerline wires coming together and then observing the aircraft with the wings level but in a shallow descent continue in a southerly direction and impact a tree.  The aircraft immediately caught fire and fell to the ground.  The wreckage was completely burnt out.

Site details

The powerline struck by the aircraft was strung between two poles on the top of ridgelines either side of the homestead. The span between the two poles was 560 m and the wires were estimated to have been in excess of 32 m above the ground at the point of impact. The poles were located in trees of a similar height and would have been difficult to see from the aircraft. The distance from the powerline to the tree struck by the aircraft was approximately 160 m.

Aircraft examination

The aircraft was extensively damaged by the post-impact fire. At the point of contact with the wires, the tip of one propeller blade and a piece of window Perspex had been torn from the aircraft. However, the aircraft appeared to have arrived at the impact point substantially intact. No defects were observed with the airframe that could have contributed to the occurrence.

The engine was removed from the aircraft for specialist examination. The examination did not reveal any defects that could have contributed to the accident. The examination of engine accessories was hampered by the intensity of the fire.

Smoke

The opinion of those experienced in the operation and maintenance of similar aircraft indicates that the most likely source of whitish smoke was a leak of engine coolant. The coolant is used to cool the heads of the four cylinders of the engine and a loss of coolant would result in an increase in cylinder head temperature but would not necessitate an immediate landing. The inspection of the engine did not indicate any signs of a loss of coolant, but the fire damage precluded any determination of the serviceability of the coolant system.

Pilot aspects

The pilot had visited the adjoining property, which is located to the east of the accident site, on the day prior to the accident. Both properties were owned by relatives of the passenger in the aircraft. While visiting the property he had discussed with the owner the upgrading of an airstrip, which was currently used in the operation of model aircraft, to a standard suitable for the operation of the Skyfox. Included in the discussion was a briefing by the property owner to the pilot of the wires surrounding the model airstrip. The briefing did not include the existence of the wires struck by the aircraft on the following day. The property owner was expecting the pilot to overfly his property on the morning of the accident. However, the owner of the property on which the accident occurred was unaware who the occupants of the aircraft were until some hours after the accident.

There was no airstrip in the area in which the aircraft was operating prior to its impact with the wires. The wires crossed a ploughed paddock which was unsuitable for the operation of an aircraft.

Analysis

It could not be positively determined if there was any fault with the aircraft prior to it striking the wires.  Likewise, the purpose of the orbits of the homestead near the accident site is unknown.  It is also unknown if the pilot had been previously aware of the existence of the wires struck by the aircraft but forgot about them on this occasion. Regardless, it appears that the pilot did not see the wires in time to avoid the collision.

Significant factors

1. It could not be determined if the pilot was previously aware of the   existence of the powerline struck by the aircraft.
2. The pilot did not see the powerline in sufficient time to avoid the collision.
3. The serviceability state of the aircraft prior to the accident could not be positively determined.