VH-EBX was tracking eastbound on air route Y44, and VH-HYG was tracking westbound on air route Q34B, both aircraft were at FL 370. These air routes diverge from Adelaide towards the west.

At approximately 75 km west of Adelaide, when the two aircraft were within 22 km of each other, with a track angle difference of 20 degrees, which was increasing as they came closer, VH-EBX experienced a traffic alert and collision avoidance system (TCAS) traffic advisory (TA). This was followed 20 seconds later by a resolution advisory (RA).

The pilot of VH-EBX responded immediately to the RA, initiating a climb to FL 380 followed by a descent back to FL 370. Neither aircraft changed heading.

The aircraft passed with a separation of 8.5 km horizontal and 900 ft vertical.

The air traffic controller had been monitoring the situation for some time and was confident that the aircraft would pass with at least the minimum required horizontal separation standard of 9 km.

The recommended vertical deviation following an RA should be no more than 700 ft. The pilot of VH-EBX climbed the aircraft through 1,000 ft before returning to the assigned level.

The B747-200 aircraft was departing runway 19 at Brisbane for Manila. As the aircraft rotated for take-off, tower controllers observed smoke coming from the left inner body main wheel tyres. Closer examination of the landing gear using binoculars, showed substantial damage and tyre loss to at least two of the main wheel assemblies. The crew was advised of the situation and elected to continue to the planned destination. Advice was received later the same day that the aircraft had landed safely.

Runway 19 was later closed for several hours after inspection revealed the presence of several large pieces of tyre tread, and a significant quantity of tyre debris. The debris covered almost the entire length of the runway. A small section of the left gear door actuating rod was also found on the main runway.

The investigation confirmed that two tyres on the left inner body gear had failed. Marks on the taxiway showed that the first tyre was flat approximately 500 metres before lining up at the departure threshold. The second tyre had burst 5 metres into the take-off roll. There were score marks on the main runway, from both wheels rims, for a distance of 1350 metres.

Specialist examination of the recovered tread section for both tyres, showed that both had failed as result of tread delamination. This report advised that the cause for the first delamination was a sudden loss of inflation pressure, most likely caused by foreign object damage. The second tyre delaminated as a consequence of overload due to the first failure. Information received from the operator shows that one of the failed tyres was re-treaded on three previous occasions, and the other tyre had been re-treaded five times.

The student pilot, who had very limited flying experience, was on his third solo training circuit for the flight when the accident occurred. The aircraft was in the ground-run phase of a touch-and-go landing when it began to veer to the left. The pilot applied opposite rudder, in an attempt to correct the situation, with no apparent effect. Realising that the aircraft would run off the strip the pilot closed the throttle and applied the brakes. However, the aircraft ran into a ditch, damaging the propeller and nosewheel leg before it stopped moving. The student pilot had completed three successful dual circuits prior to commencing solo training.

The helicopter had been chartered for a wild-pig eradication program and was returning to its base at the conclusion of the day's activities. The pilot reported that the "engine" out light came on as he was climbing through a height of about 300 ft and at about 80 kts. In the subsequent forced landing, the helicopter touched down heavily on the side of a hill and rolled over. The three occupants escaped with minor injuries, but the helicopter was destroyed.

Investigation of the engine, its components, and fuel system failed to identify any defect likely to have caused the loss of power. However, it was noted during the course of the investigation that the reasons for a large percentage of reported engine failures in this type of helicopter were not determined.

Any results from research into safety deficiencies identified during this investigation will be published in the Bureau's Quarterly Safety Deficiency Reports.

The task required the helicopter to carry a surveyor to locations two kilometres apart along north east lines. The time on the ground at each location averaged four minutes and flight time between locations was approximately one minute. Normal endurance for the helicopter, excluding reserve fuel, was 150 minutes (70 l/hr). Due to the amount of time spent with the helicopter ground running at each location, the pilot recalculated the endurance and increased it to 240 minutes (45 l/hr), excluding reserve fuel.

The recalculated endurance was checked daily for any variation in consumption rates. Also taken into account was variation of distance back to the base camp at normal power setting (70 l/hr) for arrival with reserve fuel (25 l) intact on all occasions. On the day of the accident, it was decided to carry two surveyors as they had to return to points which had already been surveyed. These points had been marked by pegs and surveyor tape to identify the locations. The second surveyor was carried to enable easier sighting of the survey pegs.

The pegs proved harder to locate than expected and the helicopter spent more time in the air than anticipated at each location. The aircraft had originally departed camp at 0700 and at 1045, 80 litres of fuel was added from jerry cans carried on board the aircraft. At 1140 the pilot advised the surveyors that they had to return to the camp which would have them back at 1200. A request by one of the surveyors to stop for a gravity reading at a position approximately one kilometre off the track to the camp site was agreed to. Approximately one kilometre from camp the engine stopped. The aircraft was at an approximate height of 80 ft on descent to the campsite with a tail wind of 15-20 kts at the time. The pilot attempted to turn the helicopter into wind to make a landing, however at 120 degrees from its original direction of travel to the left, the helicopter collided with the ground on the side of a dry creek bed.

Seven litres of fuel was drained from tanks, most of which would normally be unusable. At the time of the accident the fuel gauge indicated approximately one quarter full. The pilot did not consider the fuel gauge reliable enough to use as an indication of fuel contents and relied on a combination of dip stick readings, time in operations and fuel logs, based on average daily consumption rates, to determine the fuel state.

The investigation concluded that the extra weight of an additional passenger required more power when flying around to locate the survey pegs and the difficulty in locating the survey pegs required more hovering (at higher power settings) than anticipated. Overall hourly consumption rate had increased above planned levels leading to fuel exhaustion well before the pilot's fuel logging indicated it might happen.

The student had completed six circuits as part of a pre-second-solo check. The student's performance was accessed as satisfactory, by his instructor, and he was cleared to complete four solo circuits.

On the first solo circuit the aircraft ballooned during the landing flare. The aircraft was then observed to descend rapidly and land heavily on the main wheels after which, the nose came down starting a porposing action. The student applied full power to go-around but pitched the nose up too high (the student reported that the stall waring light and horn came on). The aircraft rolled to the left and descended impacting the ground initially with the left wing. The aircraft pitched nose first into the ground pivoting on the collapsed nosewheel in a clockwise direction whilst skidding away from the runway and coming to rest, upright, and facing the opposite direction to landing.

It is probable that the student's inexperience led to control mishandling which resulted in a stall and loss of control close to the ground.

FACTUAL INFORMATION

The Boeing 737 was being radar vectored to intercept the final approach path for a landing on runway 16R from a right base leg, to follow a Boeing 747 which was already established on the instrument landing system (ILS) final approach. The B737 turned onto the ILS localiser track below the glideslope whilst descending to 2,500 ft some 10.5 NM from the runway threshold.  Shortly after the localiser track was intercepted, the aircraft experienced several abrupt changes in bank angle, both left and right, the most severe being a roll to the right through 51 degrees to a maximum right bank of 34.8 degrees.  A missed approach was carried out, followed by a normal approach and landing. A post-flight inspection found no defects which may have contributed to the occurrence. The aircraft was subsequently cleared to continue scheduled operations.

A review of recorded radar data and of information derived from the flight data recorders of the B737 and the preceding B747. It showed that the B737 was about 450 ft lower than the B747 had been at the same point in space, reaching that point some 127 seconds after the B747 had passed.  The longitudinal separation between the B737 and the B747 at that time was 5.5 NM.

Recorded wind data, as derived from the inertial reference system of the B737, indicated the wind direction varied between 165 and 185 degrees, at a speed of 8-14 kts.

ANALYSIS

The circumstances described in this occurrence are very similar to those of an earlier occurrence (9500460).  The following features were common to both:

Both lead aircraft were B747s which were established on the localiser as well as the glideslope. Both following aircraft were B737s which were given a radar vector to intercept the localiser, below the glideslope, at 2,500 ft. This resulted in both B737s passing the same point in space some two minutes later, but 500 ft lower than the preceding B747s.

Atmospheric conditions in the vicinity of the approach path at the time of both occurrences were conducive to the slow decay of wake vortices. As the localiser track is 155 degrees, there would have been little, or no lateral displacement of any wake vortices produced by the B747s.

Both following aircraft encountered uncommanded rolls consistent with encountering wake turbulence generated by the preceding B747.

United Kingdom Civil Aviation Authority wake turbulence studies (August 1994) have shown that B747 aircraft produce high rates of wake turbulence affecting following aircraft.

For sequencing purposes during VMC operations in the Sydney terminal area, most domestic aircraft arriving from the south are radar vectored to join a downwind leg when runway 16 is the duty runway. These aircraft are routinely cleared to descend to 2,500 ft whilst being radar vectored to intercept final approach about 6 NM from touchdown. International flights, however, must be established on final approach at least 10 NM from the threshold.  Many of these aircraft, such as the B747, are in the "heavy" category. This sequencing often results in the following domestic aircraft passing through the same lateral airspace as the preceding aircraft but some 500 ft lower.

The relative positions of respective aircraft, the provision of minimum wake turbulence radar separation, and meteorological conditions conducive to the formation and slow decay of wake vortices can make it possible for aircraft to experience wake turbulence encounters whilst such procedures are being implemented.

Consideration, therefore, of the vertical positioning of the following aircraft relative to the leader may provide the greatest potential for preventing accidents and incidents as a result of wake turbulence encounters.

SIGNIFICANT FACTORS

1. Atmospheric conditions were conducive to the slow decay of wingtip vortices generated by the preceding B747.
2. The B737 was sequenced by ATC to intercept the localiser for runway 16 approximately 500 ft below the preceding B747.

SAFETY ACTION

As a result of the investigation into this occurrence and a number of other occurrences, the Bureau of Air Safety Investigation issued interim IR 960101 recommendations to the Civil Aviation Safety Authority and Airservices Australia on 7 November 1996.

"1. The Bureau of Air Safety Investigation recommends that the Civil Aviation Safety Authority and Airservices Australia:

"(i) Evaluate the current wake turbulence separation standards. Consideration should be given to the evaluation of technology being developed to aid in the detection, tracking and forecasting of wake vortices as a further means of reducing the risk of wake turbulence encounters.

"(ii) Critically evaluate all current airport arrival and departure paths and procedures to identify and eliminate potential wake turbulence problems.

"2. The Bureau of Air Safety Investigation recommends that the Civil Aviation Safety Authority re-institute a wake turbulence education program. This education program should highlight areas of possible wake turbulence encounters and advise ways to minimise the effects of the encounters".

The pilot received an airways clearance to track to Adelaide via Quarry. He was issued with air traffic control instructions to descend to 3,000 ft above sea mean level (AMSL) for an instrument landing system approach and to maintain 320 kt until 28 km from Adelaide. The pilot queried this requirement due to difficulty in scheduling the flaps and landing gear speeds in the distance remaining from the 28 km position to the landing. A more acceptable requirement to maintain 320 kt to 36 km was obtained.

At 33 km from Adelaide, while passing through 3,400 ft AMSL in cloud, with a sink rate of 1,300 ft/min and an airspeed of 310 kt, a ground proximity warning system (GPWS) mode 2 activation occurred. The pilot immediately followed company requirements by initiating a climb to 4,500 ft, being the lowest safe altitude for the area, and advised ATC accordingly. An uneventful instrument approach and landing was then carried out.

The Adelaide Approach Controller advised that the aircraft had been maintaining ground separation in accordance with the radar terrain clearance standards prior to commencing the climb.

A combination of a fast speed and high rate of descent in the vicinity of steep hills is a known cause for GPWS activation.

The pilot reported he arrived at Cooktown airport at 0615 EST to carry out a flight to Weipa. After carrying out a pre-flight inspection, and submitting a flight plan, he departed Cooktown at 0650. The flight was being conducted below cloud at 2,500 ft until about 130 NM from Cooktown when the cloud could be seen on top of the McIlwraith Range ahead. The pilot said he commenced a turn through 180 degrees and descended to 2,000 ft to clear the southern end of the ranges. Development Road was identified, and the pilot was about to commence tracking towards Cohen when the engine suddenly began to run roughly and vibrate. Power was immediately reduced, and trouble checks were carried out but to no avail.

The pilot said he had the impression that the engine was running on three cylinders. Due to the rising ground ahead the pilot made the decision to land on the road. During the landing roll the left wing impacted some small trees on the road verge which slewed the aircraft to the left. The nosewheel then got caught on the left side of the rill in the middle of the road and the pilot was unable to get it back to the right before the left wing impacted the side of a cutting. The aircraft was slewed through 90 degrees and the propeller struck the embankment. The aircraft then slid sideways for 20 metres into a table drain, and the right main and nose landing gear assemblies were torn off.

The cause of the engine malfunction was later found to be a failed exhaust valve.

That aircraft was Hudson 540, a type which is normally slower than a SAAB. Both aircraft were in visual conditions above broken cloud when the loss of separation occurred. Hudson 540 later advised experiencing a 290-knot groundspeed from Deniliquin to Albury. A check of recorded radar data and automatic voice recordings showed that Hudson 540 was actually only 12 miles from Albury when the pilot reported at 15 DME. The recorded radar data confirmed a cruise groundspeed for Hudson 540 of 290 knots from 70 miles west of Albury to commencement of descent at 30 miles west. From that point groundspeed decreased and was last observed to be 255 knots at loss of radar contact 12 miles west of Albury.

Radar contact with VH-SBA was lost when the aircraft was 23 miles south of Albury. At that point, its groundspeed was 250 knots. For comparison purposes, at that time Hudson 540 was 20 miles west of Albury with a groundspeed of 260 knots. This information was from a Melbourne radar tape. Albury tower is not radar equipped.

With VH-SBA inbound on the 207 radial and Hudson inbound on the 240 radial the aircraft were laterally separated until eight DME. It was the controller's intention to apply a specific longitudinal separation standard after the first aircraft passed the eight-mile lateral separation point. That standard allows for five miles longitudinal separation between two arriving aircraft provided that:

.  Angular difference between tracks is less than 45 degrees

.  No closing indicated airspeed

.  Leading aircraft within 15 miles of the aerodrome

.  Aircraft are assigned levels which are vertically separated.

Based on the respective DME reports of 15 DME and 11 DME for Hudson 540 and VH-SBA, the controller assessed that five miles longitudinal separation would exist when VH-SBA got to eight miles (loss of lateral separation point). This assessment was based on the assumption that the SAAB would be faster than the HS 748 and that the HS 748 would fly at least two extra track miles manoeuvring to track direct to the VOR.

Although the controller cleared Hudson 540 to divert right of track but no further south than the 240 radial, he did not actually check what radial the aircraft was tracking to the VOR. The aircraft could have tracked in on the 260 radial (only a minor diversion right of track) and commenced the VOR/DME approach without making a sector entry. If the HS 748 did track in on the 260 radial, then the two tracks would have been separated by more than 45 degrees which would mean the controller was applying an inappropriate separation standard. In addition, he did not check if there was a closing indicated airspeed. It would be reasonable to expect the SAAB, on a DME approach, to be slowing down, whereas the HS 748 could well be expected to maintain airspeed until over the VOR outbound because there is plenty of time to slow down on the outbound leg.

Factors

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

1. The controller did not take all necessary steps to ensure he had full situational awareness in that he did not establish on what radial the HS 748 would track to the VOR nor the extent to which the aircraft would manoeuvre to the right of track.
2. The controller did not establish that all the conditions existed that were applicable to the specific separation standard he was using.
3. The HS 748 reported at 15 DME when it was actually only 12 miles from the aerodrome. (Albury DME is located on the aerodrome)