During the take-off roll, the cabin manager of the BAe 146 aircraft became aware of a smoky, burning smell coming from an air vent in the region of her crew seat at the forward (L1) exit door. Initially there was a mild odour. That was followed by the rapid onset of strong fumes for a short period after which the fumes dissipated quickly. The event was of 2-3 minutes duration.

The cabin manager felt overwhelmed by the fumes and was on the verge of passing out when her colleagues became aware of the situation and provided her with portable oxygen. After approximately 10 minutes of using oxygen, the cabin manager felt well enough to attempt a resumption of her duties but was unable to continue due to the effect of the fumes exposure.

The cabin manager, who had ten years of operational experience on the BAe 146, spent the duration of the flight seated at the rear of the aircraft; breathing portable oxygen for most of that time. The cabin manager reported that when she was not using oxygen she felt unwell, she had difficulty in thinking clearly and she found it difficult to coordinate her thoughts with her actions. No other members of the crew or any of the passengers reported being affected by the fumes.

Upon arrival in Kununurra, engineering inspections were performed on the aircraft and further action was deferred in accordance with the Civil Aviation Safety Authority airworthiness directive AD/BAe146/086. That airworthiness directive required certain actions to be performed whenever a cabin air quality problem was identified, which was suspected of being associated with oil contamination of the air supply from the air conditioning packs. Subsequent engineering inspections revealed that the cause of the oil contamination was a worn number one bearing seal in the number 3 engine. The engine was replaced and no further fumes were evident during following flights.

The cabin manager sought medical treatment and tests in Kununurra on the day of the incident and in Perth on the following day. Although she was eventually cleared to return to work, symptoms of anxiety, impaired judgement, and light-headedness remained with her for in excess of one week. Of note was the result of a blood test that revealed she had been exposed to a higher than normal level of carbon monoxide (CO). When inhaled, CO combines with the haemoglobin, the blood's oxygen-carrying molecule, to form carboxyhaemoglobin (COHb). Once in that state, the haemoglobin is unable to carry oxygen. Thus, the blood's ability to carry oxygen to body tissues, including vital organs such as the heart and brain, is inhibited.

CO is the product of incomplete combustion of carbonaceous material. It is found in varying amounts in the smoke and fumes from burning aircraft engine fuels and lubricants. The gas itself is colourless, odourless, and tasteless but is usually mixed with other gases and fumes that can be detected by sight or smell. Individuals that have been exposed to CO should be removed from the exposure and administered 100 percent oxygen through a tight fitting mask until all symptoms have been resolved. If blood testing for measurement of COHb level is required, the samples should be drawn as soon as possible after the exposure, as COHb has a short half-life in the body of 4-5 hours. If an individual is administered 100 percent oxygen, the half-life is reduced to 40 to 80 minutes.

The same aircraft was the subject of a pilot report three days prior to the cabin manager's experience, in which an oil-like smell was evident in the cockpit but not in the cabin. The event was of short duration and occurred just after take-off, when the source of air supply was changed from the Auxiliary Power Unit (APU) to the engines. Inspection by maintenance engineers of the engines, APU, and air-conditioning system revealed no signs of contamination and the defect was cleared.

Evidence from previous incidents of air system contamination on this type of aircraft has indicated that fumes were associated with engine or APU oil contamination of the air conditioning system. The BAe146 is similar to many aircraft in that the supply of cabin air originates in the aircraft's engines. Air is bled from the final stage of the engine's high-pressure compressor just prior to the combustion chamber. The air destined for the cabin then passes through a catalytic converter in order to clean the air of any oil contaminants. Catalytic converters operate at maximum efficiency under highly specific conditions of temperature and contaminant to air ratio. The air is then passed through a heat exchanger and then through one of two air conditioning packs before entering the cabin. During normal operation bleed air from engines one and two is fed to pack one, which in turn supplies conditioned air to the flight deck and cabin. Bleed air from engines three and four is fed to pack two, which normally only supplies air to the cabin. Additionally, bleed air from the APU is used by either pack during the take-off and landing phases or when air conditioning is required on the ground.

The Boeing 747-400 (B747) was tracking northwest on air route R340 at flight level (FL) 330 and estimated TASHA, a position 61 NM northeast of Mount Isa, at 1530 Eastern Standard Time. The Boeing 737-400 (B737) was tracking northeast on air route J64 at FL330 and estimated TASHA at 1531. The Isa sector controller, located in the Brisbane Air Traffic Control Centre, identified the potential conflict between the aircraft and offered the B747 crew a change of level to FL350. The crew preferred a lower level due to the ability to maintain a greater ground speed; the flight had departed later than scheduled and the crew were endeavouring to make up time en route.

At 1501, the controller instructed the B747 crew to descend, when ready, to FL310 with a requirement to reach that level by 31 NM southeast of TASHA. That position was the lateral separation point between the air routes and the controller required the 2,000 ft vertical separation standard to be established between the aircraft before they entered the area of conflict. The pilot in command (PIC) readback the amended clearance in accordance with Aeronautical Information Publication (AIP) procedures. Subsequently, the crew did not descend the aircraft in accordance with the clearance and it entered the area of conflict at FL330. There was an infringement of separation standards as the required vertical standard was not achieved before the aircraft entered the area of conflict.

At about 1508, a change of controllers occurred at the Isa sector position. The new controller instructed the B747 crew to change frequency at 1512. The crew contacted the Isa controller on the new frequency and reported maintaining FL330. The AIP required a crew operating in controlled airspace to report, after any en route frequency change, the last assigned level and whether the aircraft was on climb, in the cruise, or on descent. The crew did not report the assigned level of FL310 and the controller did not query the crew regarding that report.

The controller became concerned, as the B747 approached the lateral separation point, by the lack of a report indicating that the aircraft was on descent to the amended level. The AIP required a report from a crew when an aircraft had left a level at which level flight had been conducted in the course of a climb, cruise, or descent.

The controller conducted a single interrogation (one shot) of the aircraft's automatic dependant surveillance (ADS) system and attempted to contact the crew by very high frequency (VHF) radio. Automatic Dependant Surveillance was a system dependant on a datalink and a series of reporting `contracts' (a rate of reporting) established between an aircraft and a ground system. The Australian Advanced Air Traffic Control system (TAAATS) automatically initiated contracts and specified the type of report, the content of a report, and the reporting frequency required. As the contracted reporting occurred automatically, it required no flight crew action. There was no cockpit indication that a "one shot" request had been actioned by an aircraft's ADS system.

The ADS response from the aircraft at 1527 indicated that it was maintaining FL330 and was 26 NM from TASHA, within the area of conflict. The controller again attempted to contact the crew by radio and also by the controller pilot datalink (CPDLC) facility. The controller made another "one shot" interrogation of the aircraft's ADS. That ADS response at 1529 indicated that the aircraft was at FL329 and 14 NM from TASHA.

Flight crews were required to maintain continuous communications with air traffic control while in controlled airspace and within VHF radio coverage. Crews of ADS equipped aircraft were able to report to ATC using that facility; however, they were required to communicate using VHF radio when operating within radio coverage. The B747 was operating in non-radar airspace and the crew reported their position via ADS. The route was within VHF radio coverage for the sector.

The controller was about to instruct the B737 crew to climb to FL340 when an ADS altitude report of FL312 was received from the B747. That report established that the 2,000 ft separation standard had been achieved as it was within 200 ft of the assigned level.

At 1529:43, after five unsuccessful attempts to contact the B747 crew on VHF radio, the controller asked the crew of the B737 (on the crossing route) to contact the B747 crew and have them call on 125.2 Mhz. At 1531, the B747 crew contacted the controller on the VHF radio and reported maintaining FL310. At the same time the B747's ADS issued a Waypoint Report for TASHA which reported the aircraft's level as FL309. Later analysis of the ADS reports indicated that the B747 had descended 1,700 ft in about 28 seconds.

The automatic reporting rate for ADS tracks was set by TAAATS. The flight information region was divided into cells that were allocated a reporting rate for a Basic Report. The rate was normally 30 minutes (or 40 minutes for oceanic areas). A controller with the jurisdiction of an aircraft on an ADS track can manually amend the rate as required. Also, when the aircraft passed a designated waypoint the system automatically generated a Waypoint Change Event report that was appended to a Basic Report. Furthermore, an Altitude Range Event report was automatically generated when an aircraft left a contracted vertical range. When in the cruise, that vertical range was plus or minus 200 ft of the cleared flight level (CFL). Assignment of an amended level reset the range. When on climb, the reset range was the present level minus 200 ft to CFL minus 200 ft, with the reverse range for aircraft on descent. At that time, for the B747 maintaining FL330 and then assigned FL310, the vertical range would change from FL332 - FL328 to FL332 - FL312. As the aircraft descended through FL312 the Altitude Range Event report was generated and the contract reset to FL312 - FL308; to monitor the amended CFL (FL310).

The B747 PIC later reported that they had endeavoured to remain at FL330 for as long as possible due to turbulence at FL310 that would have likely required a speed reduction, which in turn, would have constrained their efforts to make up time during the flight. At the time of the issue of the amended clearance, the PIC was the pilot flying the aircraft and the first officer had left the flight deck shortly before to take a break. On the return of the first officer, the PIC briefed him on the clearance as per company procedures and the FO wrote the clearance on the flight plan. The incident report submitted by the crew stated that the annotations used by the FO on the flight plan indicated that descent should commence at 31 NM from TASHA, instead of the requirement to be at FL310 at that point.

The crew then became involved in troubleshooting a problem with balancing the main fuel tanks. The PIC stated that they had been distracted and forgot about the requirement to descend to FL310 by 31 NM southeast of TASHA. The PIC reported that he was aware of the B737 on the crossing track as he had heard the controller request the B737 crew to contact them (the B747 crew).

The South Pacific Air Traffic Services Coordinating Group's Southern Pacific Operations Manual (SPOM) V3.1 set the standard for ADS operations for air traffic control service providers and operators. The system status and serviceability was checked following the occurrence. Between 1332 and 1719 there were 31 downlink messages of which the minimum transit time was 6 seconds and the maximum transit time was 24 seconds. Those times were within the required SPOM system performance parameters. During that period there were no reported failures of the communication or TAAATS systems.

The investigation did not establish why the B747 crew did not respond to the controller's radio calls.

The Sikorsky S76C helicopter was in cruise flight with the automatic flight control system engaged, when the flight crew noted a loud noise and the helicopter yawed to the left, rolled left, and the nose pitched down. The flight crew disengaged the automatic flight control system and resumed flying the helicopter manually, stabilising it in level flight. The right engine-out and fire-warning annunciators were illuminated, with the engine-out aural warning sounding. The right engine instruments displayed zero rotational speed of the gas generator (GG) and extremely high turbine outlet temperature (measured at point T4 within the engine). The crew activated the right engine fire bottles and simultaneously closed the fuel firewall shut-off valve. The fire indication extinguished. They then configured the helicopter for single engine flight with the remaining engine operating approximately ten seconds into the two and one-half minute One Engine Inoperative (OEI) limitation. The flight crew adjusted power requirements for the OEI condition and then completed an uneventful single engine landing at their Longford base.

Examination of the helicopter revealed minor shrapnel damage to the right engine exhaust extension, and fracture separation of the engine oil pressure switches and rear bearing external oil vent and return pipes.

The Turbomeca Arriel model 1S1 engine comprised five modules. Module three (or the high-pressure section) contained the gas generator first and second stage wheels. The left side of the right engine, forward of the external rear bearing oil return line near the outer surface of module three, displayed evidence of fire and oil residue.

The right engine was removed and shipped to the engine manufacturer's Australian facility for disassembly and examination with Australian Transport Safety Bureau (ATSB), operator, and engine manufacturer representatives in attendance.

Engine examination

Disassembly and preliminary examination of Arriel 1S1 engine, serial number 15038, revealed a separation of one GG second stage turbine blade. Blade number sixteen was separated above the blade 'fir tree' attachment point, below the blade platform, and had punctured the second stage nozzle guide vane turbine ring. The rear bearing of the GG had collapsed and was significantly damaged. Separated pieces of the centrifugal diffuser of module three were found inside the module. There were indications that several fracture surfaces of the separated sections were pre-existing before the incident. In addition, the engine exhibited signs of severe overheating and significant damage in the air path downstream of the turbine blade separation.

The fracture surface of the separated blade was typical of ductile tensile overload, with the exception of the small corner area of fatigue cracking. The dendritic patterns within the fracture were indicative of the normal underlying microstructure of the blade casting. Failure of the blade in that mostly ductile overload manner indicated exposure to a transient or sustained stress level above the ultimate strength of the blade material at its operating temperature. Refer to ATSB Technical Analysis Report 200103038 (BE/200100017) for further details.

Engine history

The engine was installed on 4 March 2000 and had accumulated 7,935.0 hours and 6,784.1 cycles since new. It had been overhauled on 12 February 1999, and had accumulated 1,992.0 hours time since overhaul (TSO) and 1,878.1 cycles since overhaul. The GG assembly second stage turbine disc, serial number DC3666YC, had been installed during the overhaul with zero hours and cycles accumulated. The turbine disc and blades were well within the life limit of 10,000 cycles established by the manufacturer. Arriel engine modification TU204 (GG turbine blade plasma coating) had been incorporated.

Previous Australian occurrences

Occurrence report 200100584

On 7 February 2001, a Sikorsky S76C helicopter belonging to the same operator, with two crew and ten passengers on-board, was in a hover with the flight crew completing before take-off checklist items. The pilot reported that while trimming the engines, a "pop" was heard. He then noted that the left engine turbine gas temperature (measured at point T4 within the engine) was in excess of 1000 degrees C. The helicopter was then landed uneventfully. The flight crew reported that the only cockpit indication of imminent failure was the almost simultaneous illumination of the left engine chip (magnetic particle) detector advisory.

Examination of the helicopter revealed minor shrapnel damage to the left engine exhaust extension and engine cowling. There was no reported engine fire. The left engine was removed and sent to the engine manufacturer for disassembly and examination. The manufacturer's final report noted a separation of turbine blade number six of the GG second stage disc. The blade was separated above the 'fir tree' attachment point but below the blade platform, and had punctured the second stage nozzle guide vane turbine ring. One adjacent blade (number seven) in the direction of turbine wheel rotation was also noted as cracked.

Metallurgical examination by the manufacturer attributed the blade failure to a low-cycle fatigue cracking mechanism. The manufacturer concluded that abnormal loading was the major contributing factor in the failure, given the reported absence of anomalous material features or evidence of high-temperature operation. Dimensional inspections failed to reveal any sign of non-conformity that could have led to the development of the abnormal loads. However, the manufacturer stated that turbine blade platform/GG disc interferences were also a potential factor that could have aggravated the fatigue failure of the blade.

At the time of the occurrence, Arriel 1S1 engine, serial number 15522, had accumulated 4,737.4 hours and 4,471 cycles since new. It had accumulated 1,740.0 hours TSO and 1,615 cycles since overhaul. Following overhaul, the engine was installed on March 11, 1999. Module three did not have turbine blade plasma coating modification TU204 incorporated.

Occurrence report 199602839

On 9 September 1996, a Sikorsky S76C helicopter belonging to the same operator, experienced an in-flight engine failure of the right engine while taking off from an oil platform. A loud noise was heard before the engine failure. The right engine was shut down and the crew completed an uneventful single engine return to the Longford base. There was no reported associated engine fire. The right engine was removed and sent to the manufacturer for disassembly examination.

At the time of the occurrence, Arriel 1S1 engine serial number 15513, had accumulated 2,282.0 hours and 1,949 cycles since new. The manufacturer provided the operator with a final report noting the rupture (separation) of one GG turbine blade with subsequent rear bearing damage and GG seizure. Their report stated that the separation was suspected to be the result of blade rubbing with the second stage nozzle guide vanes with no signs of fatigue or abnormal over temperature operation. Module three had turbine blade plasma coating modification TU204 incorporated.

Other overseas occurrences

The French airworthiness authority, Direction Generale de l'Aviation Civile (DGAC), reported knowledge of three other overseas occurrences involving GG second stage turbine blade separation failures. Of those three incident engines, all had the TU204 modification. Cycles since overhaul on those incident engine turbine discs and blades varied from 1,978 to 5,933 cycles.

Engine service bulletin history

Turbomeca Service Bulletin (SB) 292 72 0151 was originally issued on 5 June 1992 specifying the incorporation of modification TU204, the protection of the GG second stage turbine blades from corrosion or erosion with a Heurchrome low pressure plasma coating. That modification also permitted a performance improvement by allowing the more accurate machining of the turbine tip diameter to control the tip clearance. The service bulletin addressed all Arriel variants, with Arriel 1S1 engines having incorporated TU204 from the first production engine. For all other variants, TU204 implementation was optional and installed at the customers' request.

In July 1998, the engine manufacturer implemented internal documentation and procedures to remove all GG turbine blades with TU204 installed during overhaul of module three. Consequently, SB 292 72 0151 was amended on 18 August 2000, to recommend removal of all TU204 modified blades, citing possible weight mass increases and suspected increased stress on the turbine blade root. The manufacturer stated that if the plasma coating was not applied as per drawing requirements, the resulting stresses could be more than anticipated, resulting in abnormal loading of the blade root. Both incorporation and removal of modification TU204 required removal of the engine and/or module and shipment to the manufacturer.

External oil pipe description

Three external oil related pipes provided lubrication of the GG rear bearing. Those pipes passed through hollow support struts and were then physically secured to module three. The supply oil pipe provided oil from the engine driven gear type oil pump to the bearing after passing through a restrictor and a tube screwed into the bearing housing. Oil was then sprayed onto the bearing. After lubricating the bearing, the oil fell by gravity to the bottom of the housing, through a tube and was returned to the tank through an oil pipe to the scavenge pump. The air/oil mist that resulted from the lubrication of the bearing was vented overboard through a vent pipe attached to the top of the housing.

Engine oil flashpoint/autoignition

The engine oil temperature of a normally operating Arriel 1S1 engine in a S76C helicopter was approximately 100 degrees Celsius (C). The flash point of the turbine engine oil was approximately 223 degrees C. The flash point of a liquid was defined as the lowest temperature at which a material would produce a flammable vapour, and was a measure of the volatility of the material.

The auto-ignition temperature of engine oil was approximately 388 degrees C. Auto-ignition temperature was defined as the temperature at which auto-igniting materials spontaneously combust. According to the engine manufacturer, during normal operation, the external surface temperatures of number three modules ranged between 280 to 450 degrees C, dependent upon location on the module, with a maximum surface temperature of 450 degrees nearest the rear bearing. The surface temperature maximum values of module three were well within the auto-ignition temperature of the engine oil.

A Saab SF340B aircraft (Saab) departed Tamworth aerodrome and was tracking to the southeast on climb to flight level (FL) 120. A Mooney Aircraft Corporation M20J (Mooney) was travelling in the opposite direction en route from Bankstown to Inverell via Scone and Tamworth at 8,500 ft. The Mooney was in Tamworth class "C" controlled airspace. The Saab crew received a traffic alert from that aircraft's traffic alert and collision avoidance system as the Saab was approaching 8,000 ft. The Saab crew levelled their aircraft at 8,200 ft and rolled the aircraft to the left to avoid the Mooney. The pilot of the Mooney did not request or obtain an airways clearance from the Tamworth Aerodrome Controller (ADC) to enter Tamworth control area prior to the occurrence. The Saab passed within 1.8 nautical miles (NM) horizontally and 300 ft vertically of the Mooney. The required separation standard was either 1,000 ft vertically or a minimum horizontal distance determined using the appropriate "Lateral Separation" table in the Manual of Air Traffic Services (MATS). There was an infringement of separation standards.

Tamworth Air Traffic Control (ATC) provided a non-radar, or procedural control, service to aircraft operating within the Tamworth control area and control zone (CTR). Controllers used non-radar information to establish and maintain procedural separation standards in accordance with MATS. Tamworth class "C" control area steps extended to 36NM when above 6,500 ft AMSL to the south-southeast of the Tamworth aerodrome in the area that encompassed the flight path of the Mooney. Class "G" non-controlled airspace surrounded the Tamworth CTR and control area.

The Saab crew was conducting a scheduled fare-paying passenger flight under instrument flight rules (IFR) and had been cleared by the Tamworth ADC to climb to FL120. The standard altitude Tamworth ATC could assign to aircraft leaving Tamworth control area and entering the overlying Brisbane sector in accordance with the letter of agreement between Tamworth ATC and Brisbane ATC, was FL120 (subject to other aircraft). Otherwise, a procedural separation standard was applied by Tamworth ATC and coordinated with the Brisbane sector controller, or responsibility for separation was specifically assigned to the Brisbane sector controller.

The pilot of the Mooney was an IFR pilot and was normally provided with radio frequency management instructions by ATC along the route. On this flight however, the pilot of the Mooney was operating under visual flight rules (VFR) and no such advice was provided. All aircraft crews that planned to enter class "C" controlled airspace, whether operating under IFR or VFR, were required to establish two-way radio contact with ATC and obtain an airways clearance prior to entering class "C" airspace. The Tamworth visual terminal chart (VTC) depicted the lateral boundaries of class "C" control area surrounding Tamworth aerodrome above 4,500ft AMSL. However, neither the VTC nor the Aeronautical Information Publication (AIP) En-Route Supplement Australia (ERSA) specified the vertical boundary between Tamworth control area and the overlying Brisbane sector. The pilot later reported that he had studied the Jeppessen low altitude en-route chart relevant to Tamworth, prior to the flight, and believed that he would not require an ATC clearance to enter Tamworth control area above 6,500ft AMSL.

Airservices Australia reported that the Brisbane sector controller had seen the occurrence on that controller's air situation display (ASD) in the Brisbane Air Traffic Services Centre and had received a short term conflict alert (STCA) from The Australian Advanced Air Traffic System (TAAATS). The Brisbane sector controller reported that STCA's between aircraft operating within Tamworth control area were common but did not necessarily indicate a potential infringement of separation standards. Short term conflict alerts, in those circumstances, occurred when the procedural separation standard being used by Tamworth ATC was less restrictive than the STCA activation parameters used in TAAATS.

Although the track symbol and a label, showing the secondary surveillance radar code and the altitude from the Mooney, were displayed to the Brisbane sector controller on the ASD, the Brisbane sector controller had no control or jurisdiction over the Mooney and was not aware that the pilot had not established two-way radio contact with Tamworth ATC. The Brisbane sector controller was also not aware that the pilot had not received an airways clearance to enter Tamworth control area. The Brisbane sector controller believed both aircraft were under the control of Tamworth ATC because both aircraft were within the Tamworth control area. The Tamworth ADC was unable to provide a separation service to the Saab in relation to the Mooney as he had no information on that aircraft.

The crew of the Beech 1900D (B1900) aircraft had been cleared by the aerodrome controller (ADC) 1 to descend to 4,000 ft and were instructed to join the circuit via a left base leg for runway 12L (northern) circuit at Tamworth. The ADC 1 also instructed the crew to report approaching 4,000 ft. The crew acknowledged the clearance but later advised that they were unable to report approaching 4,000 ft due to frequency congestion. The ADC 1 had assigned 4,000 ft so that a procedural separation standard of 1,000 ft could be maintained with other aircraft until he could see the B1900 and apply visual separation.

The crew of the B1900 subsequently requested confirmation of their assigned level and reported their position when at 2NM north of the aerodrome. The controller then sighted the aircraft and cleared the crew to make a visual approach. The controller also asked the crew if they would need to extend through the centreline of runway 12L. The crew acknowledged the visual approach but did not advise the controller that they would need to extend through the centreline. The visual approach clearance authorised the crew to descend below 4,000 ft.

The crew of the B1900 could not comply with the instruction to join the circuit via a left base for runway 12L because the aircraft was too high and too fast. The co-pilot was the non-flying pilot and was undergoing command upgrade training. He had acknowledged the clearance for the visual approach and had previously acknowledged the instruction to join the northern circuit via a left base leg for runway 12L. At the time that the visual approach clearance was issued, the pilot-in-command was aware that they could not comply with the circuit entry instruction. He believed that the controller would have been aware that they were unable to enter the circuit on a left base leg, given their proximity to the circuit at that time and the height and speed of the aircraft. He also believed that the controller would have taken those circumstances, and the disposition of traffic in the southern circuit, into account when issuing the visual approach instruction.

The B1900 continued to descend and entered the runway 12R (southern) circuit airspace which was under the control of the ADC 2. The ADC 1 notified the ADC 2 that the B1900 had entered the southern circuit. The ADC 2 advised the ADC 1 that there was a Pacific Aerospace Corporation Airtrainer CT4B (CT4) on a right base leg for runway 12R. The ADC 2 provided traffic information about the B1900 to the crew of the CT4. There were four other CT4 aircraft inbound to the circuit at that time but the ADC 2 had not sighted them. The ADC 1 was unable to apply the required separation standard, either 1,000 ft vertically, or a minimum horizontal distance determined using the appropriate `Lateral Separation' standard from the Manual of Air Traffic Services (MATS), between the B1900 and the traffic inbound to the southern circuit. There was an infringement of separation standards.

The ADC 1 reported that he had sighted the CT4 on right base. He then instructed the crew of the B1900 to make a right turn and track via a right base leg for runway 12L. He believed that the B1900 was visually separated from that CT4 and that he could maintain visual separation between the B1900 and that CT4 with that instruction. He did not think that there had been an infringement of separation standards between the B1900 and the aircraft inbound to the southern circuit because all parties had enough time to ensure that visual separation was not infringed.

A Boeing 747-200 (B747) was being radar vectored from the west for sequencing to runway 21 at Perth. A de Havilland Canada DHC-8-102 (Dash 8) was being radar vectored from the east for sequencing to land on runway 21 behind the B747. When the crew of the Dash 8 reported that they had sighted the B747, the air traffic controller assigned them the responsibility for separation from the B747. The rate of closure between the two aircraft was high and the crew of the Dash 8 received a traffic advisory from their traffic alerting and collision avoidance system. Although the Dash 8 crew was being issued with radar vectoring instructions by air traffic control, they were obliged to turn their aircraft to the right to avoid the B747.

Radar data and air traffic control automatic voice recordings were reviewed to establish the sequence of events. The investigation found that the approach controller had assigned the responsibility for separation to the pilot of the arriving Dash 8 while the aircraft was being radar controlled. The radar separation standard required 3NM horizontal separation while there was less than 1,000ft of vertical separation. During the occurrence, radar separation reduced to 1.82NM when there was 100ft vertical separation. A radar or vertical separation standard was not required when some other form of separation was being applied. In this situation the controller was relying on visual separation.

Visual separation of air traffic may have been a valid method to use in circumstances where less than the required radar separation is achievable. However, the criteria for the application of the standard were clearly detailed in the Manual of Air Traffic Services (MATS) Part 4 Section 5. In particular, MATS 4.5.1.11 stated:`In circumstances where an aircraft has been instructed to maintain separation from, but not follow, an IFR aircraft, traffic information shall be issued to the IFR aircraft, including advice that responsibility for separation has been assigned to the other aircraft'. The arriving B747 was an IFR aircraft but was not provided with the required traffic information.

The pilot of the Cessna 402 (Cessna) had been cleared by the aerodrome controller (ADC) to land on runway 16R at Sydney Kingsford Smith airport. The ADC monitored the aircraft's approach and after landing it was established that the pilot had landed on taxiway Alpha, which was parallel to, and to the right, of runway 16R. There was no other aircraft on taxiway Alpha at the time. The weather was visual meteorological conditions (VMC).

The pilot of the Cessna had approximately 3,000 hours flying experience and had planned to operate an instrument flight rules (IFR) charter flight from Broken Hill to Bankstown via Dubbo. En route the pilot amended the destination to Sydney in an attempt to assist the passengers to connect with their next flight. The pilot had never operated into Sydney but had recently operated into Adelaide and felt that he could self-brief satisfactorily using the Aeronautical Information Publication (AIP) documents. He was familiar with Bankstown but predominantly operated in country areas where, generally, runways had limited or no markings.

Runway 16L was 2483 m long and runway 16R was 3962 m long. Each runway had a parallel taxiway located to the right. Runway 16L was 1037 m to the left of runway 16R and taxiway Alpha was 183 m to the right of runway 16R. Runway 16R threshold was 2,862 m north of the runway 16L threshold. Runway 16R threshold was 497 m north of the intersection of taxiways Alpha and Foxtrot. The colour of the surface of taxiway Alpha changed between taxiways Foxtrot and Golf due to a bitumen/concrete join.

The flight departed Dubbo at 1445 Eastern Standard Time. The pilot tracked via Bindook and was issued with an Odale 2 standard arrival clearance to the aerodrome. He was using the AIP En Route Supplement to assist in orientating himself with the aerodrome layout and made a visual approach to final for runway 16R. He reported that when the aircraft was on the [right] base position he had an uninterrupted view of the area and could see what appeared to be the parallel runways. At the time, the pilot did not appreciate the distance between the runways and the extent of the offset of the runway thresholds. He aligned the aircraft with what he thought was runway 16R, but in fact was taxiway Alpha, with the intention of landing. The ADC issued a landing clearance and as the aircraft passed 1,500 ft on descent the pilot saw a Boeing 747 enter the taxiway he had intended to use. The pilot elected to go around and advised the ADC that he was initiating a go around. The ADC coordinated a clearance with the departure controller and instructed the pilot to turn onto a heading of 170 degrees, to climb to 3,000 ft and to contact the departure controller. The pilot did not query the ADC with respect to the aircraft entering his intended runway as he immediately complied with the instructions and changed to the departure radio frequency.

The ADC saw that the Cessna was high on final and believed that the pilot conducted the go around because the aircraft was too high and did not query the pilot about the approach. The prime means for the ADC to establish aircraft positions was by monitoring aircraft visually. The ADC had an air situation display (ASD), plus access to a surface movement radar (SMR) display to assist in confirming positions of arriving and departing aircraft, and aircraft on the aerodrome. The resolution of both displays was dependent on the selected scale and was also limited, to some extent, by the lateral proximity of runway 16R and taxiway Alpha.

The aircraft was re-sequenced for another visual approach to runway 16R. During the second approach the pilot again aligned the aircraft with what he believed to be runway 16R and subsequently landed on taxiway Alpha.

Runway 16R and taxiway Alpha were marked in accordance with Civil Aviation Safety Authority Rules and Practices for Aerodromes.

Taxiway Alpha had:

1. centreline markings, and
2. sideline markings.

Runway 16 had:

1. threshold markings,
2. designation or number (16R) markings,
3. centreline and sideline markings,
4. fixed distance markings, and
5. touchdown zone markings.

Runway 16R was served by an instrument landing system (ILS) navigation aid which provided centerline and glidepath guidance to pilots of aircraft that were fitted with ILS avionics. It also had a T-VASIS that provided a visual approach slope indication. The Cessna was not fitted with an ILS and the pilot was not qualified to conduct an ILS approach. The pilot was instructed by the director controller to report the runway in sight. The pilot reported he had the "aerodrome in sight". The controller did not subsequently query the pilot to confirm that he had the runway in sight. The requirement to report the runway in sight was a function of independent visual approach procedures and was not a runway allocation procedure.

During the second approach, the distance between the Cessna and an aircraft ahead in the approach sequence was reducing and was likely to infringe the required wake turbulence separation standard of 6 NM. The director asked the pilot if he was happy to continue the approach with less than the standard separation. The pilot reported to the director that he was happy to continue. Manual of Air Traffic Services (MATS) procedures required controllers to "ensure that the appropriate wake turbulence minima are applied at the landing threshold" for aircraft on final approach to the same runway. The intention was for only pilots to initiate requests for wake turbulence waivers. Controllers were not to initiate such requests.