The pilot was flying a night approach to a beach landing area marked by a circle of lights consisting of three motor vehicles and six flashing strobe lights. The approach was flown over water in conditions described as very dark, with no visible horizon below 500 feet altitude. The pilot reported that the approach appeared to be proceeding normally when, at what he thought was about 200 feet altitude, the helicopter suddenly yawed right and struck the water. No fault was found with the helicopter which might have contributed to the accident. Wreckage examination indicated that the helicopter contacted the water while in a right skid and that the main and tail rotors were under power at impact.

The pilots were competing in a triangular navigation exercise and were in the vicinity of the final turning point. The aircraft were orbiting in a thermal when they collided at a height of about 3500 feet above the ground. Both aircraft became uncontrollable and the pilots parachuted to safety. The investigation established that both aircraft were orbitting to the right when they collided. Examination of the wreckage showed that the right wing of VH-GXY hit the left wing of VH-GGV. The impact was on the leading edge of each wing. About two metres of the wing of VH-GXY was severed, and about one metre of the wing of VH-GGV. Neither pilot had been aware of the presence of the other aircraft in the thermal.

The pilots were competing in a race as part of the World Gliding Championships. The gliders were in a group climbing in a thermal, when they collided at about 3900 feet above mean sea level. The Italian pilot in LB did not see the other aircraft, while the Polish pilot of VH-GSO only became aware of the proximity of LB at the last moment. The collision severed the right half of the horizontal stabiliser of LB, however the pilot was able to retain control of the aircraft and landed without further damage.

The aircraft were part of a four aircraft formation taking part in a photography session. On return to Darwin it was intended that the aircraft land one after the other on the same runway. The first aircraft landed and the pilot requested a clearance to turn off the runway onto a cross strip. A clearance was not available due to other traffic on that strip and the pilot was instructed to continue taxying along the runway. As the second aircraft commenced the flare for landing it collided with the aircraft already on the runway. The flight had been poorly planned and the briefing conducted before DEPARTURE was inadequate. The pilot flying the second aircraft to land was inexperienced on the aircraft type and had no formation flying experience.

The pilots were competing in the Austraglide '86 international gliding championships. During a cross-country exercise a number of gliders were thermalling in the same general area. The pilot of D-2870 entered a thermal at about 4000 feet above ground level. His entry was made via a 45 degree bank right turn, but after turning through about 450 degrees the left wingtip of his aircraft contacted the forward under-fuselage area of VH-HNZ. This aircraft had been in a left turn with about 12 degrees angle of bank. Following the collision, both aircraft remained under control and were flown to the planned destination without further incident. Neither pilot saw the other aircraft prior to the collision. The pilot of VH-HNZ had been turning to adjust his track and had been watching other gliders well below his level. Visibility forward and downward is somewhat restricted in this particular model of glider. The pilot of D-2870 advised that he was turning towards the sun and climbing when the collision occurred.

Arrangements had been made for the aerobatic team to perform an air display over the water at Portsea, prior to the start of a large Regatta. These arrangements included advice to the organisers of the area in which the display would be made. The team carried out a successful practice session the night before. On the morning of the Regatta they proceeded to Portsea where change over was made to a discrete VHF radio frequency so that necessary radio communications could be made between team members and the display was commenced. The display sequences were completed as planned until after about 10 minutes the final sequence was commenced from a vee formation with the leader in front and numbers two and three positioned on each side of him. For this manoeuvre the aircraft were to pull up in turn, on a count of three, from level flight at about 500 feet to complete five eighths of a loop, followed by a 180 degree roll to upright and then dive to level off at 500 feet in line astern and depart the area. The first to pull up was to be number two, followed in turn by numbers one and three. For a significant proportion of the manoeuvre, pilots of the following aircraft are unable to see the aircraft ahead.

Successful conduct of the manoeuvre required that all team members perform compact loops of similar diameter. As planned and on the call of the leader the number two pilot commenced his pull up, followed by number one on a count of three and then by number three, also on a count of three. About three quarters of the way up the loop the leader realised something was wrong as he could see number two too early and called for number two to speed up. There was no response, but this was not considered unusual. As he pulled over the top of his loop the leader again lost sight of number two. The leader descended initially as planned but then levelled off, concerned about the location of number two and realising he would have to move sideways, to the left away from the shore crowds. He looked right and left and was suddenly hit from behind and above by number two aircraft. The aircraft collided at a height of about 750 feet. The number two aircraft was very badly damaged in the collision and descended steeply into the water, contacting the sail of a yacht as it fell. The leader's aircraft was significantly damaged by the collision but he was able to maintain partial control and was forced to limit engine power due the control difficulties. As a result of the damage, the aircraft was unable to maintain height.

A ditching was made in a clear area adjacent to some yachts. The pilot escaped from his sinking aircraft and was assisted by a person from a nearby yacht. He was subsequently taken on board a rescue vessel. The weather was fine with good visibility, the temperature was 18 degrees and there was a light westerly wind. The leader's aircraft was not recovered, but he reported there were no operating problems with it prior to the collision. About 70 percent of the number two aircraft was recovered. Examination of this did not reveal evidence of any pre-existing defects which might have contributed to the accident. The aircraft used for the display were all of the the same general type but had different performance capabilities. This was primarily because of different engines and aircraft weights. As was normal procedure, the leader flew the aircraft with the least performance, the aim of which was to allow a performance margin for the other two aircraft which in most team manoeuvres, had to be positioned with respect to the leader. A disadvantage in this type of manoeuvre is that it is necessary for the other two pilots to limit the engine power and ensure that they fly the same path. In his pre-display briefing the leader made a point of drawing attention to this aspect.

An amateur video was taken of the accident flight and this indicated that the total time from the start of the pull-up by the number two pilot, until the collision, was about 15 seconds. The video showed that on the pull-up, number two aircraft climbed much higher than normal and that during descent it completed some two and three quarter rolls to the left prior to the collision with the number one aircraft. Because of the relative positions of the two aircraft from the top of their respective climbs it would have been very difficult for either pilot to have seen the other in time to avoid the collision. Opinions were obtained from experienced aerobatic pilots concerning the rolling manouvers of the number two aircraft. In the main these opinions indicated that the manoeuvres were controlled and that the aircraft maintained the required line during descent. Earlier in the display sequence, a team manoeuvre with some similarity to that on which the accident happened took place. On this occasion, however, the number three pulled up first, followed by the number one, both of which then completed a manoeuvre similar to that during which the accident happened. Number two pulled up last and because he has to delay before his next sequence, he sometimes executed a large diameter pull-up followed by a diving manoeuvre which included one and a half rolls. A possible explanation for what happened on the accident sequence was that the pilot inadvertently employed a procedure generally similar to that he sometimes used earlier in the display.

The accident manoeuvre had only recently been added to the sequence, being completed three times previously, including once at an air display two weeks earlier and twice during practice sessions. In aerobatic terms the accident manoeuvre was not difficult. All pilots in the team were experienced aerobatic pilots with approvals to conduct aerobatics down to a height of 500 feet above ground level. The pilots in numbers one and three aircraft had been in the team from its formation some ten years earlier. The pilot in the number two aircraft had joined as a part-time member in 1982 and had been a full-time member since 1985. Air displays of this type require that the performing aircraft not track or manoeuvre towards spectators within a horizontal distance of 500 metres or pass within 200 metres horizontally from spectators. There were many official, spectator and competition boats in the area. The leader indicated that there were also large clear areas of water. He reported he conducted the display with the aim of remaining over the clear areas. At times there were water craft moving into the display area and he altered the path of the runs to avoid these.

Circumstances:

The PA-44 aircraft was cleared to take-off and given a clearance which included the instructions to maintain runway heading and to call Adelaide Approach airborne. At about the same time, the TB20 was approaching Adelaide at 2,000 feet from Parafield to conduct a practice Adelaide/Parafield non-directional beacon (NDB) approach, which uses the Adelaide NDB. The TB20 pilot was cleared to conduct the NDB approach. The PA-44 did not commence its take-off run until about 110 seconds after lining up and being issued with the clearance. During this period, Adelaide Approach East issued a restriction of 2,000 feet for the PA-44, which Tower passed on to the pilot. Once the PA-44 became airborne, Tower advised Approach East that Tower was able to co-ordinate the separation between both aircraft. Approach East then directed Tower to amend the PA-44 clearance to direct to Port Stanvac at 2,000 feet. Tower could not raise the PA-44 as the pilot had changed to Approach radio frequency as instructed. Approach East then reported that he had issued the revised clearance to the PA-44 pilot. Almost a minute passed before Tower advised Approach East that a conflict was rapidly developing between the PA-44 and the TB20. The TB20 pilot, on the outbound leg of the NDB, reported sighting the PA-44 at a distance of about 30 metres, level, on his right and tracking from right to left.

Significant Factors:

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

1. The PA-44 aircraft held on the ground for almost two minutes before commencing take-off.

2. Both Tower and Approach controllers allowed a situation to develop where neither was certain which section was responsible for separation between the two aircraft.

Recommendations:

1. The CAA might consider this incident as the basis of an article to illustrate to pilots the reasoning behind RAC/OPS-0-52 which states in part that if the pilot calls "ready" he should be prepared to "make a roll-on take-off in one continuous movement if take-off clearance is given". The implication is that the take-off should be commenced without delay and that the Tower controller will assume the aircraft is ready for immediate take-off.

2. The CAA should examine procedures at Adelaide to ensure that there is no doubt which controller is controlling which aircraft. Special attention should be paid to the Adelaide/Parafield NDB procedure and full traffic information should be given to pilots "under the hood" conducting instrument training. The CAA has agreed to prepare an article in response to the first recommendation for publication in the Aviation Safety Digest. The second recommendation was actioned by the CAA during the process of the investigation.

The pilot of VH-HCE was preparing to conduct solo circuits and landings, using runway 11 Right. The aircraft had stopped facing northwards on the bitumen section of runway 36 Right, just south of taxiway Lima, while the instructor vacated the aircraft. The Piper VH-EMZ had previously landed and was taxiing westward along taxiway Lima. As VH-EMZ approached the runway 36 Right intersection, VH-HCE began to cross taxiway Lima, heading towards the holding point for runway 11 Right. The two aircraft collided in the middle of the taxiway. The pilot of VH-EMZ subsequently reported that she had difficulty seeing along the taxiway because of the late afternoon sun. The pilot of VH-HCE reported that he had looked along taxiway Lima prior to moving forward, but had not seen the other aircraft.

Both aircraft were conducting scenic flights over North Stradbroke and Moreton Islands. Neither the pilot of VH-WAS nor the pilots in VH-DMB submitted a flight plan (nor was it a requirement) and were operating NOSAR, NO DETAILS outside controlled airspace on a "see and be seen" basis. No routine radio transmissions were heard from either aircraft when they were in the South Passage Bar area. VH-DMB had flown over Moreton Island and was turning left at an angle of bank of 25 degrees when it collided with VH-WAS at 1500 feet above mean sea level over the South Passage Bar. The pilot of VH-WAS stated that his aircraft was turning through east, in a shallow right turn when he felt and heard an impact. It was immediately obvious to him that a wingtip section from the left wing was missing, but he was unaware of what his aircraft had struck. An uncontrolled, left, descending turn ensued and the aircraft descended about 1200 feet before the pilot managed to level the wings after reducing the engine power to idle. He transmitted a brief MAYDAY call during the recovery. The pilot successfully ditched the aircraft some 4 kilometres east of Reeders Point, Moreton Island. After the aircraft came to rest, it floated for about a minute before sinking in 7-8 metres of water. The pilot and his passenger escaped from the wreckage and each clung to a separated aircraft wheel. They then began to swim for the shore on the incoming tide. VH-DMB plummeted out of control and impacted in a near vertical dive on a shallow sand bank some 800 metres from the shore of North Stradbroke Island. Inspection of the wreckage found that the left wingtip of VH-WAS had struck the cockpit area of VH-DMB. It is probable that this impact disabled both the front seat occupants of VH-DMB. The left mainwheel of VH-WAS had severed a 1.2 metre section of the left wing of VH-DMB. The investigation determined that both aircraft were in a position to have been visible from the cockpit of the other aircraft for at least 10 seconds before impact. Several factors affect a pilots ability to observe other aircraft. In this case it is likely that the relative position of each aircraft to the other meant that they were in a constant position in the other pilots field of view. The pilot of VH-WAS was also looking in the direction of the sun and VH-DMB was coloured such that it would not have contrasted with the backdrop of a high overcast. Although the pilots in VH-DMB were looking down-sun it is possible that the small frontal cross-section presented by VH-WAS would have been lost against the background of the island and the horizon. Because of the nature of the sight-seeing flights being undertaken by both aircraft it is also possible that all pilots may have been partially distracted from their lookouts by passengers. As a result of a previous accident involving a mid-air collision, the Bureau of Air Safety Investigation has undertaken to conduct an evaluation and prepare a report on the practicality of the "see and be seen" principle.

Circumstances:

Both pilots were conducting solo navigation exercises for the removal of the area restriction from their Private Pilot Licences. The pilot of VH-JGG, following a brief refuelling stop at Mudgee, took off from runway 04 and climbed to circuit height prior to setting heading from the downwind leg. At about the same time, VH-DAF entered the downwind leg for runway 04, after approaching the circuit area from the west. Both pilots made the required radio calls but possibly may not have heard each other due to preoccupation with their respective arrival and DEPARTURE procedures. An eyewitness reported seeing one aircraft being overtaken by a second aircraft which appeared to be taking evasive action. The right wing of the overtaking aircraft struck the left wing of the leading aircraft. The overtaking aircraft, which was subsequently identified as VH-DAF, lost its right wing in the collision and spun to the ground about two kilometres northwest of the aerodrome. The other aircraft was landed successfully in a paddock about two kilometres southeast of the aerodrome, despite extensive damage to the left wing which rendered aileron and flap systems inoperative and airspeed indications unreliable. At the time of accident, the weather was fine with scattered cloud at 4000 feet and visibility in excess of 10 kilometres.

Significant Factors:

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

1. The pilots of both aircraft failed to see each other for reasons which could not be determined.

2. VH-DAF overtook and collided with VH-JGG.