Circumstances:

The pilot of VH-CXE was flying in company with, but about two miles ahead, of another aircraft flown by his daughter. VH-CXE was observed apparently flying a straight in approach to the sealed Runway 01 at Mt Margaret and to then go around from the approach (there was a 15 knot crosswind from the right at the time). The following aircraft also went around from its initial approach and flew another circuit. Neither occupant of this aircraft saw VH-CXE during the second circuit and a radio query failed to bring any response. A fire was noticed on the western threshold of the dirt cross strip, but this was not associated with VH-CXE. Later, when VH-CXE could not be located, the position of the fire was examined and confirmed as the wreckage of VH-CXE. Investigation revealed that the aircraft had struck the ground in a near vertical nose-down attitude while rotating left. The wreckage had burnt out and the extent of fire damage precluded a complete examination of the aircraft and its systems. However, no evidence was found to suggest that the aircraft was not capable of normal operation prior to the accident. It was established that the landing gear was locked down, the wing flaps were fully extended, and the engine was producing substantial power at impact. It was not possible to determine if the pilot experienced incapacitation prior to the accident.

Significant Factors:

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

1. The aircraft struck the ground, probably in uncontrolled flight, for reason(s) which could not be determined.

Circumstances:

The pilot, accompanied by two employees, was carrying out an aerial inspection of a harvesting operation in a large open paddock. The aircraft had approached from the north, flying at approximately 150 feet above ground level, and carried out a right hand orbit. It then proceeded for a short distance in a southerly direction, before entering a steep descending turn to the left towards a three wire powerline positioned north-south across the paddock, the spans of which were approximately 30 feet above ground level. Approaching the powerline the aircraft was observed to climb rapidly, and a noise like a breaking stick was heard as the left hand wingtip contacted the centre wire of the powerline. The aircraft continued to climb steeply to about 80 feet above ground level. It faltered momentarily before stalling and impacting the ground 100 metres east of the powerline. The aircraft impacted on its left hand wing and nose. It bounced a further 25 metres while turning inverted and became engulfed in a ball of fire which reduced it to ashes. In 1988 the pilot received a serious head injury which resulted in the Civil Aviation Authority not renewing his pilot licence pending additional information from the pilot regarding his medical condition. The pilot did not provide sufficient information but continued to fly up to the time of the accident.

Significant Factors:

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

1. The pilot was conducting a low flying operation.

2. The pilot probably saw the powerline too late to avoid it.

3. The aircraft stalled at a height from which it was too low to effect a recovery.

Circumstances:

While the helicopter was flying at about 60 knots and 400 feet above the ground, the pilot heard a loud bang. The helicopter yawed slightly, and the pilot felt an airframe vibration. As the pilot reduced airspeed and initiated a descent, he saw the red fire warning light illuminated and realised that the engine had failed. After a successful autorotative landing, the pilot extinguished several small scrub fires under the helicopter tail boom. These fires were ignited by hot metal ejected from the engine. He also extinguished a small oil fire in the engine bay. The engine failure resulted from the failure of the intermediate gear/pinion in the reduction gearbox. The gear failed due to fatigue cracking which commenced at an overstress crack. This crack, plus similar cracks found in the root of five adjacent gear teeth, probably occurred as a result of main rotor blade strikes which occurred when the helicopter rolled over during a ground run approximately 765 hours time-in-service earlier. After this earlier rollover accident, the reduction gearbox was inspected and returned to service in accordance with the Turbomeca Arriel 1 Engine Maintenance Manual. The engine manufacturer is aware of two other total ruptures of intermediate gears of the same modification status as was fitted in the reduction gearbox of VH-HRR. Eight more failures of intermediate gears of a later modification status have been detected by pilots, without ensuing engine failures, because of warning lights triggered by metal particles on an electric magnetic plug.

Significant Factors:

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

1. VH-HRR experienced a rollover accident involving main rotor blade strikes approximately 765 hours time-in service previously.

2. Engine maintenance manual inspection requirements do not necessarily require overhaul or crack testing of a reduction gearbox after main rotor strikes/sudden stoppages.

3. Fatigue cracking commenced at an overstress crack on the intermediate gear within the reduction gearbox.

Recommendations:

It is recommended that the CAA liaise with the engine manufacturer to consider the desirability of incorporating more stringent inspection requirements in the engine maintenance manual to detect cracks in components after rotor blade strikes/sudden stoppages. RESPONSE TO S The CAA has been in contact with the engine manufacturer (Turbomeca) and the relevant certification authority (DGAC) with respect to reduction gearbox failures. Turbomeca intends to be more precise in the wording of the Engine Maintenance Manual concerning inspections to be carried out after rotor blade strikes/sudden stoppages.

The Boeing B747 was under radar control by Sydney Approach (North). The aircraft had descended to 2000 feet and intercepted the Runway 16 localizer in preparation for an ILS approach to Sydney (Kingsford Smith) International Airport. The Piper PA28 was engaged in a solo navigation exercise from Bankstown Airport which is 16 km west of Sydney International. The exercise required the Piper to depart Bankstown tracking in a northerly direction along the Lane of Entry (LOE) outside controlled airspace (OCTA) while remaining below 2000 feet. The LOE abutts the western boundary of the Sydney Control Zone (CTR) and the Sydney Control Area (CTA).

The surface wind in the Sydney and Bankstown areas was light and variable the cloud base 3500 to 4000 feet and the visibility 10 km or more. The PA28 departed Runway 29 at Bankstown and the pilot identified and flew over the first aeronautical ground strobe light (at Clyde) marking the departure track in the LOE but was unable to sight the second light (at Carlingford). The pilot did not make good the required track of 007 degrees magnetic to follow the LOE but allowed the aircraft to fly on into the Sydney CTR on a north-easterly heading. The pilot subsequently recognised Macquarie University and then changed course to depart the Sydney CTR.

As the B747 was intercepting the glideslope at 2000 feet the Second Officer saw a light aircraft ahead at the same level. It was in the 12 30 relative position tracking generally towards the B747 and crossing from right to left. The Captain and First Officer of the B747 also sighted the light aircraft as it passed abeam to the left at an estimated 200 feet horizontally and at the same altitude. The B747 crew identified the aircraft as a PA28 but did not observe the rotating beacon on the PA28. The PA28 pilot first sighted the B747 as it passed abeam to the left. The Sydney Approach (North) controller first noticed a faint primary paint radar contact very close to the B747 at about the same time as the B747 crew reported the near miss. The radar return became stronger and recognisable as the aircraft turned to the North. At the time of the incident the PA28 pilot had a total of 110 hours flying experience. The pilot had flown northbound in the LOE on three previous occasions; twice dual and once solo. The last time being some 10 weeks before the incident. Prior to boarding the aircraft the pilot's flight plan was checked by an instructor but formal briefing on the particular navigation exercise or the LOE was not provided.

The procedure in place at the relevant flying organisation relied on the student to find an available instructor to provide flight plan checking and exercise briefings. No self-briefing aid eg video was available at the Bankstown Pilot Briefing Office for pilots to familiarise themselves with the features of the LOE. The PA28 pilot stated that after take-off on Runway 29 Centre at Bankstown the aircraft was climbed straight ahead to 1000 feet before commencing a right turn. The pilot then identified the Rosehill refinery and the first ground strobe light. The aircraft was then on a heading of about 013 degrees magnetic from Bankstown. After passing over the first ground strobe light the pilot was unable to find the next strobe light at Carlingford. Attempts to find the second light were made without reference to the aircraft heading and the pilot then became directionally disoriented. The position of the Carlingford light was correctly depicted on the current Visual Terminal Chart being used by the pilot. Eyewitness evidence indicates that the Carlingford strobe light was operating.

The PA28 was flown on headings well to the right of that required to maintain correct track from the first ground strobe light to the second one. This led to a penetration of the Sydney CTR and conflict with the inbound B747. Sydney Approach (North) was not able to detect the impending conflict as the PA28 was not transponding. It was not required to have an active transponder and there were no primary radar returns which was probably due to tangential fading. The PA28 was not displayed until the B747 and the PA28 were in close proximity and the PA28 changed heading. Sydney Approach Control (North) is not able to identify monitor or readily communicate directly with aircraft which stray into the Sydney CTR from the LOE. The rotating beacon of the PA28 was ineffective in giving the B747 crew early warning of conflicting traffic. The PA28 was sighted against a background of suburban housing presenting a nearly head-on aspect. None of the B747 crew recalled observing the PA28's rotating beacon. The B747 crew considered that the PA28 was sighted in sufficient time for avoiding action to have been taken had it have been warranted. Neither aircraft took avoiding action. The performance of the Sydney air traffic control radar was not a factor.

RECOMMENDATIONS:

For CAA Central and NSW Offices.

Consideration should be given to the following

a. Establishment of facilities whereby ATC can identify monitor and communicate directly with all aircraft which enter the Sydney CTR and CTA from the Bankstown LOE without authorisation.

b. Revising the inbound and outbound tracks in the LOE so as to minimise the risk of traffic penetrating the Sydney CTR and CTA.

c. Installing a more effective visual guidance system in the Bankstown LOE then the present aeronautical ground strobe light facilities.

d. Amending the Sydney VTC so as to accurately show the relative positions of aeronautical ground lights and other significant land marks.

e. Ensuring that all unserviceable aeronautical ground lights are repaired within hours of the notification of failure.

f. Establishing a procedure which enables Sydney ATC to identify aircraft intentionally operating in R409 A&B.

g. Providing self-briefing facilities at the Bankstown pilot briefing office as a matter of urgency for pilots to study prior to operations through the LOE.

h. Considers a requirement for all Australian registered general aviation aircraft to be fitted with multiple rapid flashing omnidirectional white strobe lights.

i. Taking action to ensure that pilots undergoing navigation training are properly supervised and maintain a satisfactory level of proficiency in negotiating the Bankstown LOE.

This accident was not the subject of an on site investigation. CIRCUMSTANCES: "The pilot stated that when she was on final approach to land on runway 28, and at about 30 feet above ground level, another aircraft which had previously been stationary near the threshold moved to the middle of the runway and began to take off. The pilot stated that there was no time or avenue for a go-around and avoiding action was taken. During the avoiding manoeuvre the aircraft stalled and impacted the ground near the edge of the runway."

CIRCUMSTANCES: "During a routine maintenance inspection on 2 March 1988 numerous creases were found in the surfaces of both wings. In addition, spar cap rivets were found to be damaged by shear load. The damage was indicative of the aircraft having been subjected to excessive positive `G' loading in flight. The circumstances leading to permanent deformation of the wings were not determined."

Circumstances:

"A Boeing 747 (B747) operating a scheduled regular public transport flight from Singapore to Melbourne and a Boeing 767 (B767) operating a scheduled regular public transport flight from Perth to Auckland were involved in an alleged close proximity incident near Narrandera NSW. Due to staff shortages in the Melbourne Area Approach Control Centre (AACC) the Melbourne Sector 4 airspace was declared to be deactivated by the issue of a Notice To Airmen (NOTAM) 1523. Whilst this airspace was deactivated transiting aircraft were required to comply with Traffic Information Broadcast Area (TIBA) procedures specified by NOTAM 1522.

The B767 flight path would transit this airspace during the period of deactivation. The B747 was offered route shortening at a non-standard level of Flight Level 37 000 feet (FL370) within Sydney controlled airspace under the jurisdiction of the Sydney Area Approach Control Centre Sector 6. The non-standard level was assigned due to other international traffic inbound to Sydney operating below the B747. No positive information update had been provided to the Sector 6 controller about the progress of the B767. Flight paths of both aircraft were within radar surveillance range and jurisdiction of the Sydney Sector 6 controller for some time prior to the incident.

The shortened route would place the B747 on a track which would cross that of the B767 at the same level and approximate time near Narrandera unless some separation action was taken. The B767 subsequently entered Sydney Sector 6 airspace three minutes earlier than flight planned estimates indicated. As soon as that aircraft contacted Sector 6 it was instructed to descend from FL370 to non-standard level FL350 to provide vertical separation with the crossing B747. The aircraft queried the instruction which was verified by Sector 6. However, communications with the aircraft were then lost and no readback of the assigned level was received.

Because of this the Sector 6 controller then instructed the B747 to change heading intended to maintain separation and to eventually pass behind the B767. ZK-NBE (B767) The B767 flight plan was submitted at Perth at 1438 Coordinated Universal Time (UTC) for a flight from Perth to Auckland via waypoints overhead Adelaide and Sydney. The flight would transit deactivated airspace promulgated in Melbourne NOTAM 1523 at 0848UTC. This airspace was normally under the jurisdiction of Melbourne AACC Sector 4. The B767 would then enter airspace under the jurisdiction of Sydney AACC Sector 6 at Narrandera.

The flight plan Estimated Time of Departure (ETD) was 1530UTC with the associated Estimated Time Intervals (ETI) and Estimated Times of Arrival (ETA) providing en-route timings for the following coded waypoints ETI to MALIM 02.51 - ETA 18.21UTC NYA 02.58 - 18.28 ASSS 03.05 - 18.35 NAR 03.17 - 18.47 RUG 03.31 - 19.01 Once the departure message was received from Perth notifying the actual departure time as 1542UTC (12 minutes later than flight planned) the above estimates could then have been updated as follows ETI to MALIM 02.51 - ETA 18.33UTC NYA 02.58 - 18.40 ASSS 03.05 - 18.47 NAR 03.17 - 18.59 RUG 03.31 - 19.13.

This could have given Sydney Sector 6 some expectation that the B767 would enter the deactivated airspace at 1828UTC (prior to MALIM waypoint) and exit deactivated airspace at NAR at 1859UTC. Because of the deactivation of Melbourne airspace, the normal step-by-step co-ordination exchanges between the Adelaide Melbourne and Sydney controllers were not completed and the Narrandera strip and estimate could therefore not be accurately updated by the Sector 6 controller. The last actual reported position of the B767 was to Adelaide control at 1748UTC when the aircraft reported over waypoint T6B 1747UTC FL370 estimating MALIM waypoint at 1830UTC, i.e. three minutes earlier than could have been expected by the Sydney Sector 6 controller.

VH-EBU (B747) The B747 flight plan was submitted in Singapore at 1132UTC for a flight from Singapore to Melbourne via waypoints overhead Derby Parkes Bindook (near Katoomba) Shellys (near Goulburn) and Eildon Weir. This circuitous route was planned to keep the aircraft within controlled airspace and clear of the Melbourne deactivated airspace which had been notified at 0856UTC (Melbourne NOTAM 1523). The aircraft had planned to descend from FL370 to the standard level of FL350 after passing Bindook and tracking towards Shellys and onwards to Melbourne. The aircraft departed within a few minutes of the notified ETD of 1215UTC and proceeded as planned.

Subsequently at 1808UTC Adelaide control instructed the B747 to contact Sydney control on Very High Frequency (VHF) 128.2 Megahertz (MHz) at the next waypoint T34A. (At 1812UTC Adelaide control instructed another international aircraft also to contact Sydney control on 128.2 MHz as primary frequency but offered 118.5 MHz as a secondary (alternative) frequency). The B747 contacted Sydney control on 128.2 MHz at 1813UTC and reported passing waypoint T34A maintaining FL370 and estimating Parkes at 1849UTC. At 1836UTC Sydney control Sector 6 advised Melbourne control Sector 2 of the B747 inbound via Parkes and requested if a shorter track from Parkes to Wagga and Melbourne would be available in the Melbourne airspace.

Melbourne control analysed the situation and concurred that the B747 could be given amended clearance to track Parkes Wagga Albury Eildon Weir Kinglake and Epping. At 1838UTC Sydney Sector 6 passed this amended clearance to the B747. Then the B747 was given a frequency change from 128.2 MHz to 118.5 MHz to maintain continuous communications for the amended route. Investigation Summary Investigations indicated that the crew of the B767 were given the Melbourne NOTAMs 1522 and 1523 on the flight deck just prior to departure from Perth. They did not consider that there had been a breakdown of separation resulting from the incident.

The B767 crew considered that the incident had been resolved as a Sydney control supervisor had spent some time discussing the matter on air with them. They acknowledged that they had the appropriate NOTAMs but had not fully understood the significance of Para.7 of NOTAM 1522. The B767 crew believed that their clearance from Perth via planned route was valid through all Australian airspace and that the wording of Para 7 ""SHOULD"" was not a mandatory requirement even though they had been advised of the frequency by Adelaide as 128.2 MHz. It should be noted that the VHF site for the 128.2 MHz facility is at Mt Oxley approximately 260 nautical miles north of Narrandera near Bourke.

As VHF communications are restricted to line-of-sight propagation characteristics the use of this frequency placed the B767 at the limit for communications over this distance at FL370 and out of communications at FL350. The crew of the B767 were using Jeppesen charts which similar to the Australian documentation carried ambiguous frequency data indicating that the choice of frequencies to be used in the Trans Continental Control Area (TCTA) and Western Routes (from Sydney) were 128.2 MHz or 118.5 Mhz when beyond 150 nautical miles Sydney. Whereas the latter frequency was the correct frequency to be used in the Southern portion of Sector 6 airspace.

The 118.5 MHz VHF facility site is located at Mt Canobolas near Orange almost on the direct track and only 130 nautical miles from Narrandera. The B767 crew had made all the required broadcasts on the TIBA frequency 128.95 MHz whilst within deactivated airspace. They first became aware that the event had been reported as an incident when they heard it from the media after arrival at Auckland. Investigation of the incident indicated the following. the Sector 6 controller had no co-ordination update provided for the Narrandera waypoint. the flight progress strip ETA Narrandera was correctly based on ATD.

The Sector 6 controller was unable to descend the B747 due to other crossing traffic. an SSR return was observed in the vicinity of Narrandera indicating FL370 which was believed to be the B767. the Sector 6 controller could not determine the frequency used by the B767 on first contact because of the placement and operation of the VHF control and presentation facilities on controller workstations. the B767 did not respond to the level change instruction and the level readout display was slow to indicate a descent had been initiated. the Sector 6 controller was not permitted to use the Mode C level readout for separation purposes.

The Sector 6 controller discussed the situation with more senior controllers and elected to turn the B747 right of track to avoid crossing the flight path of the B767. radar separation standards were maintained at all times. the aircraft had vertical separation of 2000 feet at the time of passing. the B767 had not called 15 minutes prior to entering Sydney airspace for clearance in accordance with TIBA NOTAM procedures. The investigation concluded that there was no breakdown of the prescribed separation standards and that although both aircraft had not been formally identified on radar there was sufficient information for the Sydney Sector 6 controller to anticipate that the aircraft painting over Narrandera at FL370 was the B767.

The off-airway route shortening of the B747 initiated by air traffic control added complexity to the prevailing traffic airspace management and co-ordination requirements. The investigation noted that at the time that the B767 first made contact with Sydney Sector 6 on 128.2 MHz the VHF transmission was very broken. This can be indicative of an aircraft either with transmitter problems or on the extreme range of VHF communications. On the first communication Sector 6 instructed the B767 to descend to non-standard level FL350. This was intended to maintain vertical separation between the B767 and the crossing B747.

The VHF reception of Sector 6 by the B767 was also most probably broken for the same reason (i.e. equipment problems or out of range) and the B767 aircrew queried that instruction. Sydney Sector 6 verified the instruction and added that the aircraft was required to report reaching FL350. There was no response to this instruction or readback of the new assigned level by the B767. This was most probably because it was then out of range of the Mt Oxley VHF facility even at FL370. Loss of communications with the B767 left the Sydney Sector 6 controller with minimal options to maintain separation between the B747 and the B767.

The chosen action was to vector the B747 away from the flight path of the B767. Sydney Sector 6 contacted the B747 thirty seconds later and instructed that aircraft to turn right onto a magnetic compass heading of 270 degrees for separation purposes. Sector 6 continued to call the B767. When no contact could be established the B747 was given traffic information with the relative bearing (2 o'clock) and distance (30nm) from the B767 with the advice that the aircraft was out of communications at that time. The B747 reported sighting the B767 traffic. Subsequently at the time of passing (1900.30UTC by radar plot) the aircraft were separated by 10.5nm horizontally travelling in opposite directions and achieving 2000ft vertical separation.

Sydney Sector 6 continued to call the B767 until communications were established on 118.5 MHz at 1901.40UTC some 4 minutes 20 seconds after contact was lost at 1857.20UTC. The B767 then reported maintaining FL350. At that time, the aircraft was 2000 feet below and 17 nm from the B747 and increasing the horizontal separation. The investigation also revealed that the crew of the B767 and the Air Traffic Service staff did not fully understand the intentions and procedures expressed in the appropriate Melbourne NOTAMs. This is not a reflection of the comprehension skills of the personnel but an indictment of the complexity and ambiguity of the NOTAMs and the procedures."

Recommendations:

"It is requested that the Civil Aviation Authority give consideration to the following recommendations to ensure that air traffic control personnel.

1. Use consistent phraseology when initiating frequency change instructions.

2. Issue the correct frequency change instruction for the area in which an aircraft is or will be operating.

3. Are reminded of the necessity to accomplish frequency changes before an aircraft is out of VHF range from the previous VHF outlet.

4. Are provided with documentary evidence of the VHF coverages available from the outlets under their control.

5. Are provided with training in VHF communications characteristics of the CAA radio telephony systems.

6. Have the control and presentation of the VHF/UHF frequency call lights modified so that controllers can immediately determine the frequency on which an aircraft is calling.

7. Have procedures prescribed to indicate the frequency coded, if necessary, on which an aircraft is communicating and all subsequent frequencies recorded on the flight progress strip applicable to a particular controller where more than one frequency is terminated at that workstation.

8. Be advised of this incident as an example of where the offering of track shortening and non-standard levels can result not only in increased communications control workloads and co-ordination but may suddenly and unexpectedly result in reduced safety standards."

CIRCUMSTANCES: "The pilot reported that during the takeoff roll the aircraft was slow to accelerate. At about 50 knots the aircraft became airborne in a nose-high attitude, and the pilot experienced difficulty in lowering the nose. Shortly afterwards the aircraft stalled, the left wing dropped and the aircraft turned through about 120 degrees before impacting the ground. It was determined that the takeoff had been conducted with the flaps in the fully extended position. The pilot had not previously flown this particular aircraft, and was not aware that a flap position indicator was fitted. He had judged the takeoff setting by watching the flaps extend, and had then released the selector, expecting it to be spring-loaded to the neutral position. However, the centering spring was broken and the flaps continued to full extension. The aircraft was found to be about 57 kilograms above the maximum permitted all-up-weight, and the centre of gravity was close to the rear limit. It was evident that the pilot was surprised by the aircraft attitude and the unusually high control column forces required after takeoff, and was unable to react to the situation in time to avoid losing control of the aircraft."

This accident was not subject to an on scene investigation. CIRCUMSTANCES: During a maintenance inspection substantial damage was found to the wing structure in the vicinity of the left main landing gear. It was considered that the damage was consistent with a heavy landing. The aircraft had been flown on several occasions in the previous month by different pilots. No reports had been made of any occurrence likely to cause the damage found to the aircraft. The damage should have been readily noticeable during pre-flight inspections.

CIRCUMSTANCES: "VH-TAB was eastbound from Perth to Melbourne. VH-TAD was westbound Melbourne to Perth. The eastbound aircraft was initially flying air route T6/T10 at Flight Level 330 (Fl 330) and the westbound aircraft on an air route further to the south, T15 at Fl 310. When the eastbound aircraft passed position T6E the Adelaide Sector One controller contacted Perth Sector with a request that the eastbound aircraft be asked if it would accept clearance to track direct from position T6D to Mr William on track T10. (See attached chart) T6D direct Mt William represents a short cut compared with the standard route T6T10. The eastbound aircraft accepted the revised track at 1925. At the time of the track change the Adelaide Sector was being operated by a 'controller-under-training' and the rated training controller for the sector was away from his position taking a meal break. However, before going for the meal break the controllers had discussed ""track shortening"" for both aircraft. Track shortening was not offered to the Westbound aircraft because problems may result with radio communications if aircraft are given routes to the South of T15. The short cut took the eastbound aircraft further to the south than the standard route and eliminated the lateral separation between the tracks of the two aircraft. When the rated controller returned to duty from his meal break the trainee 'handed over' the Sector and went to dinner. A short time later, at 2006 hours, the westbound aircraft reported at position T15B and requested climb to FL 330. This report was relayed to the Adelaide Sector One controller who then cleared the aircraft to FL 330. Each aircraft was on a different radio frequency and each was unaware of the position and altitude of the other. At about 2032 hours, the pilot of the eastbound aircraft observed an aircraft approaching and turned on more of his lights. The pilot of the westbound aircraft responded in a similar manner. The crews report the aircraft appeared to pass at about the same level and within two kilometres laterally. The trainee controller who offered the 'track shortening' for the eastbound aircraft was aware that he was giving away the lateral separation existing between the normal eastbound and westbound routes, and he was conscious that the vertical separation, which existed, had to be maintained. One of the functions of ATC is that of expediting the flow of air traffic. Controllers at Adelaide believed that track shortening saved the airlines considerable sums of money. However the 'T' route structure across the Great Australian Bight is designed to provide the most direct routes possible while laterally separating eastbound and westbound traffic. Short-cuts on these routes will result in insignificant savings in flight time. Furthermore, the loss of lateral separation can preclude the use of optimum cruise levels. The saving, in flight time, for the eastbound aircraft involved in this incident would have been about one minute. When the rated controller returned from his meal break the traffic situation was explained to him and he was made aware that the eastbound aircraft had been given track shortening. This information was also displayed on the flight progress board. Nevertheless, when the westbound aircraft requested FL 330 the controller cleared the aircraft at that amended level in the belief that the required lateral separation would exist at the time the aircraft passed each other. Following the investigation, safety recommendations have been made. These have led to a review of training, checking and supervision procedures for controllers and to track shortening being prohibited on 'T' routes outside of radar cover, except when requested by aircraft for operational-safety reasons."