On 25 May 2002, at 1157 hours Eastern Standard Time, a Cessna 172 (Cessna) came within approximately 600 m of a departing Boeing 747-300 (B747) while the B747 was climbing through the altitude of the Cessna. The pilot of the Cessna was tracking in accordance with what he believed to be the visual clearance issued by Cairns air traffic control at 1,000 ft AMSL. The B747 crew was tracking via a standard instrument departure (SID) which specified a left turn after take-off.

The aerodrome controller issued the pilot of the Cessna with a clearance to track via the 'southern shores'. The term 'southern shores' was referred to in the Cairns local air traffic control instructions as the 'southern shores of Trinity Inlet'. The aerodrome controller understood that the clearance referred to the shoreline between the Cairns inlet and False Cape along the southern shore of the Cairns harbour. The pilot of the Cessna was not familiar with the term 'southern shores' and thought the controller meant the shoreline on the southern side of Cairns airport (which was the northern shore of the Cairns harbour). The term 'southern shores' was not specified in any document available to the pilot.

The pilot correctly read back the clearance to the aerodrome controller. That correct readback indicated to the aerodrome controller that the pilot could comply with the clearance.

The Cairns local air traffic control instructions stated that a clearance to aircraft to track via the 'southern shores' was meant to provide wake turbulence separation between an aircraft departing Cairns via a runway 15 SID and an aircraft over the southern shore of the Cairns inlet.

The aerodrome controller reported that he had kept both the B747 and the Cessna in sight and that visual separation was maintained between the two aircraft throughout the occurrence. The ADC provided the Cessna pilot with turn instructions, to enable him to avoid the B747, and traffic information about the B747 and a wake turbulence advisory. The B747 crew received a resolution advisory from their traffic alert and collision avoidance system about the Cessna.

The controller issued a clearance to the pilot of the Cessna that was, to the aerodrome controller, a specified route but one that was not known to the pilot. The aerodrome controller was not aware that the pilot's understanding of the 'southern shores' differed from his own. The meaning of the term 'southern shores' was not available to the pilot of the Cessna and therefore the potential existed for the misunderstanding between the pilot and the aerodrome controller that resulted in this occurrence.

The Hughes 369E helicopter, with the pilot the sole occupant, departed Strahan aerodrome at 0815 hours Eastern Standard Time (EST) for charter operations in the Western Tiers area of north-western Tasmania. Multiple flights were required from a base at Lake Mackenzie to a number of dispersed mountain hut locations. The flights involved transport of varying amounts of external loads and personnel, and included extensive periods on the ground with the helicopter engine running.

At approximately 1500 hours the pilot conducted a flight with an external load from Lake Mackenzie to Lake Nameless Hut. He then landed to embark three passengers for transfer to another hut. Two of the passengers occupied the remaining two front seats and the third passenger occupied the cabin right rear seat. The pilot reported that, while on the ground, the fuel low level advisory light had momentarily illuminated, but that he attributed that illumination to the distribution of fuel in the tank due to the slope of the ground. At that time, he reported also noting 100 lbs (86.9 lbs useable) of fuel indicated on the fuel quantity indicator. At 1515 hours, the helicopter departed Lake Nameless Hut for Tom Whitely's Hut, which was located approximately 5 km to the north-east. A passenger reported that, during that flight, a caution advisory light had illuminated. The investigation could not confirm the identity of that light. Having overflown the hut landing area, the pilot initiated a left descending turn to the south prior to commencing an approach to land.

The pilot reported that at 1524 hours, as the helicopter descended through about 200 ft above ground level (AGL), and at a speed of 70 kts, the main rotor speed decreased and the engine auto reignition advisory light illuminated. Assessing that the engine had lost power, the pilot reported that he initiated an autorotation to land. He stated that "...the aircraft landed normally, although heavily". He reported that, after the initial ground contact, the aircraft was "...suddenly rotated through 180 degrees". That rotation was reported by the pilot to be as a result of entanglement with an unseen "...little wire or whatever hooked the aircraft".

The helicopter was destroyed by impact forces. There was no fire. The pilot and three passengers sustained serious injuries.

Wreckage information

The helicopter impacted the ground heavily on the rear of the right landing skid, collapsing it and separating the left landing skid. The fuselage impact ground scar measured about 2 m in length. The main rotor blades struck the ground and severed the tail boom. The helicopter came to rest about 7 m and bearing 200 degrees magnetic from the initial impact point, facing the direction from which it had approached, and lying on a fence line. There were no ground impact scars between the fuselage impact ground scar and the helicopter's final position. The right side rear fuselage floor area sustained severe impact damage and the right fuel cell bladder was ruptured.

The forward section of the cockpit was destroyed during the impact sequence. The two front seat passengers were ejected from the helicopter, in the direction of flight. On-site inspection found the pilot's and passengers' seat belts and attachment points intact and that the pilot's shoulder harness was separated at the harness-to-inertia reel strap buckle. There was no evidence that the passengers' seat belt buckles had received damage due to impact forces. The pilot and front seat passengers' seat structure was deformed and wrinkled. Information from the helicopter manufacturer indicated that a vertical impact force loading of the airframe in excess of 10 g would have been required to deform the seat structure in that manner.

The investigation determined that there was minimal rotation of the tail rotor driveshaft at ground impact. That was confirmed by the lack of any impact or rotary damage to the tail rotor blades. The engine output driveshaft was separated at the driveshaft lobes and displayed little or no rotation at the time of separation.

The external load long-line was found attached to the cargo hook. There was no evidence that the long-line had snagged on the ground, other obstacles or the helicopter prior to impact.

An old wire and timber post fence was located in the vicinity of the accident site. The fence was about 1 m high and aligned about 050/230 degrees magnetic. The fence was laterally displaced about 3.5 m from the initial impact point. The fence posts and wire exhibited no evidence of having been contacted prior to, or during the helicopter's initial ground impact.

Testing of components

Analysis of the helicopter fuel system determined that a common fuel-sending unit activated the fuel quantity indicator and fuel low level advisory light. The fuel-sending unit, fuel quantity indicator and fuel low level warning system were removed from the helicopter and tested. Testing indicated that those components were serviceable in accordance with the manufacturer's maintenance manual. The fuel low level advisory light illuminated at 35 lbs fuel indicated on the fuel quantity indicator, in accordance with the manufacturer's maintenance manual. Testing, disassembly and inspection of the engine fuel pump, fuel control unit, fuel nozzle, bleed valve and power turbine governor, revealed no anomalies.

Meteorological information

The Bureau of Meteorology Area Forecast, valid at the time of the accident, indicated Visual Meteorological Conditions with moderate southerly winds. The pilot and passengers reported bright, sunny conditions and a light and variable southerly wind.

Personnel information

The pilot in command held an Air Transport Pilot (Helicopter) Licence, a Command Multi-Engine Instrument Rating and was endorsed on the Hughes 369E helicopter type. At the time of the occurrence, the pilot had accumulated a total of 3,565 flying hours, including 74.0 hours on type. He had flown 34 hours in the previous 90 days, of which 5 hours was on type. He was reported to be fit and well rested prior to the flight.

On the afternoon prior to the occurrence, the pilot completed a 0.5 hour proficiency check flight with the company Chief Pilot, in accordance with the company Operations Manual and CAO 20.11 appendix 4. It was reported that the check flight did not include external load or autorotation sequences. The pilot reported that he had significant prior external load experience, conducted in several helicopter types. He was unsure when he last practised an autorotation in the Hughes 369E. He reported, however, that he had completed autorotation and other emergency training in an Augusta 119 Koala helicopter about one week prior to the occurrence, and in a Bell 205 helicopter about one month prior to the occurrence.

Helicopter information

The maintenance release was current and there were no outstanding maintenance requirements. A routine 100-hourly engine inspection was carried out on 25 May 2002. Post-accident technical examination of the engine and wreckage indicated that the helicopter was capable of normal operation prior to the occurrence.

The gross weight of the helicopter at the time of impact was estimated to be within the authorised maximum operating and Height Velocity Diagram weight limits. The longitudinal and lateral centres of gravity were estimated to be within published flight manual limits. Helicopter performance was estimated to be sufficient for both in and out-of-ground effect flight.

Fuel planning/loading

The company Operations Manual stated a flight planning fuel consumption rate of 100 L (176 lbs) per hour for the Hughes 369 type. Charter helicopter fuel planning was required to include the provision of 20 minutes fixed and 15 per cent variable reserve. However, a reduction to a 10-minute fixed reserve was authorised for helicopter external load operations. That amounted to 42.4 lbs (29.3 lbs useable) indicated on the fuel quantity indicator at the company planning fuel consumption rate.

The pilot reported that the company Chief Pilot suggested a planning fuel consumption rate of 200 lbs per hour and that 100 lbs (86.9 lbs useable) indicated on the helicopter fuel quantity indicator equated to about 15 to 20 minutes flying time. He stated that, throughout the day's operations, he maintained a fuel log indicating an average fuel consumption of approximately 200 lbs per hour. The ground search and rescue party reported that, on arrival at the accident site, they collected paper and other loose items in the immediate vicinity of the wreckage. Those papers and items were secured in a large bag left at the accident site. The pilot's log was not recovered from that bag of items.

The pilot reported that a total of 280 L of fuel was added to the helicopter during the day using the operator's drum fuel stock and hand rotary fuel pump located at Lake Mackenzie. That amount of fuel was based on the pilot's understanding that approximately 280 turns of the rotary pump were made during the day's refuels and that pump output was 1 L per turn. He reported that he visually checked the fuel quality after each refuel. Post-accident examination of the remaining company drum fuel stock confirmed that it was JetA1 and did not reveal any contamination. Post-accident testing of the hand rotary pump used to refuel the helicopter determined an actual pump output of 0.7 L per turn.

Operational information

The helicopter flight manual stated that the fuel low level advisory light illuminated when approximately 35 lbs of fuel (21.9 lbs useable) remained in the fuel tank. The manual further stated that illumination of the fuel low level advisory light required the pilot to 'land as soon as possible', which was defined as:

Execute a power-on approach and landing to the nearest safe landing area that does not further jeopardise the aircraft or occupants.

A warning was included in the flight manual that, with the fuel low level advisory light illuminated:

Sideslips may cause fuel starvation and result in unexpected power loss or engine failure.

The flight manual also contained a Height Velocity Diagram that represented combinations of altitude and airspeed from which "a successful autorotation landing would be difficult to perform". Those figures were calculated at mean sea level, over a smooth hard surface and on a standard day (15 degrees C temperature, 1013.2 mb atmospheric pressure). The manual mandated adjustment to the helicopter gross weight limits, as a function of density altitude, in order for the Height Velocity Diagram to remain applicable. The pilot reported that he entered autorotation from a descending left turn at approximately 200 ft AGL. While the speed of the helicopter as the pilot rolled out of the turn could not be accurately determined, the pilot reported that he established 65 kts in the autorotation descent.

Organisational information

The Civil Aviation Safety Authority (CASA) had conducted regular surveillance audits of the company since issuing the company with an Air Operator's Certificate. The last on-site audit was conducted on 6 July 2001 and a remote audit was conducted on 30 January 2002. Those audits did not indicate any safety deficiencies.

The Civil Aviation Safety Authority approved company Operations Manual directed that "...all operating personnel associated directly with..." the company were to observe the "...instructions, procedures and information contained in..." the manual. The Manual also directed that "...all company personnel associated with piloting and flight line management..." must sign the signature sheet in the master copy of the Operations Manual "...as evidence of having read, understood and agreed to apply the procedures and data contained in it". The occurrence pilot was employed by the operator on a "standard day" contract, and was therefore required to comply with the provisions of the Operations Manual, but was not required to sign the master copy of the Manual.

The coordinator for the Western Tiers operation reported that there was no formal contract in place with the operator for the day's operations and no formal audit of prospective helicopter support organisations by the charter client. It was reported that the operator was contracted for the day based on extensive previous experience operating with the charter client and the statewide experience of its pilots. The occurrence pilot had not previously flown in the Western Tiers area of Tasmania.

Survival information

The pilot reported that a flight operations brief was conducted with personnel present at Lake Mackenzie prior to commencement of the day's operations. That brief included operating around the Hughes 369E helicopter and the operation of the aircraft doors and safety belts. The pilot also reported that, prior to takeoff for the occurrence flight, he had asked the passengers to confirm their seat belts were secure. Passengers reported that they were not wearing headsets during that flight.

Flight notification details for the flight were not submitted to Airservices Australia, nor was there any requirement to do so. There was no formal flight-following process undertaken by the operation. The pilot reported that radio communications with Air Traffic Services (ATS) had not been possible. The pilot reported making a Mayday broadcast on the forestry service channel following the reported engine power loss. That broadcast was not reported as having been received by any station.

Prior to being noted overdue, the pilot had departed Lake Mackenzie for Lake Nameless with an external load and was to return to Lake Mackenzie. At about 1600 hours, the helicopter was reported overdue to the operator by the coordinator of the Western Tiers operation. The operator then alerted Melbourne ATS of the overdue helicopter. At 1652 hours, ATS alerted Australian Search and Rescue (AusSAR). The pilot reported manually activating the Emergency Locator Transmitter (ELT) shortly after 1700 hours. AusSAR directed an aircraft to the area to conduct a beacon search at 1715 hours. That aircraft flight crew made the initial detection of the ELT signal on 121.5 MHz at 1720 hours. The ELT signal was first detected by the COSPAS/SARSAT satellite constellation at 1756 hours.

At about 1900 hours, a rescue helicopter from Hobart located the wreckage and survivors. A number of attempts were made to land at the accident site. Low cloud and fog prevented the landing and the rescue helicopter departed for Launceston airport to refuel. The survivors reported that departure of the helicopter resulted in a marked decrease in their morale.

The ground search and rescue party arrived at the accident site at 2338 hours. The four survivors required treatment for varying degrees of hypothermia and spinal and other injuries. They were transported from the site by rescue helicopter and arrived at Launceston General Hospital by 0516 hours on 29 May 2002.

An infringement of separation standards occurred 70 NM east of Darwin, NT, between a descending Boeing 737-376 (737) and an Embraer EMB-120 (Brasilia) that was maintaining level flight. The event took place during the hours of darkness and in visual meteorological conditions. The crew of the 737 intentionally flew the aircraft through its assigned level in response to a traffic alert and collision avoidance system (TCAS) warning. The Brisbane sector controller also received a short-term conflict alert (STCA) between the two aircraft from the Australian Advanced Air Traffic System (TAAATS). The STCA alerted controllers when the radar trajectories of two aircraft indicated that separation standards might be infringed. The 737 and the Brasilia passed within 1.6 NM horizontally and 600 ft vertically. The required separation standard was either 3 NM or at least 1,000 ft.

TCAS is an airborne device that functions independently from the ground based air traffic control system and provides collision avoidance protection for a broad range of aircraft. The system fitted to the 737, TCAS II version 6.04, provided recommended escape manoeuvres in the vertical dimension, to either increase or maintain the existing vertical separation between the aircraft. The escape solution was communicated directly to the flight crew via a cockpit display and a synthesised voice attention getter. The TCAS alerts in the 737 used a liquid crystal display (LCD) instantaneous vertical speed indicator (IVSI) with red and green markings to indicate the vertical speeds to be avoided (red), and the desired vertical speed to be flown (green). The display was 70 mm square and had a fixed range of 6.5 NM. Aircraft were depicted using geometric symbols, depending on their threat status. A partial aircraft symbol was displayed at the extremity of the screen for aircraft detected beyond the display range. TCAS information could, in principle, have been incorporated in the electronic flight instrument system display (EFIS) of that aircraft but wiring and space available in the electronics racks of the aircraft would have required a major modification programme. TCAS information that is incorporated in the EFIS display allows the pilot to show traffic at longer ranges.

TCAS equipment interrogates the transponders of other aircraft to determine their range, bearing and altitude. Accordingly, the TCAS does not provide protection against aircraft that do not have an operating transponder. The Brasilia was fitted with an operating mode C transponder (altitude encoding) but was not TCAS equipped and the crew was not immediately aware of the infringement of separation standards. The Brasilia, which had 30 passenger seats and had a maximum take-off weight of 11,990 kg, was not required to be TCAS equipped by the Australian legislation current at the time. That legislation mandated the carriage of TCAS for all turbine-powered aircraft with more than 30 passenger seats or a maximum take-off weight greater than 15,000 kg. When both potentially conflicting aircraft are fitted with TCAS, both TCAS units co-ordinate their intentions to provide appropriate co-coordinated avoidance manoeuvres.

TCAS II can issue two types of alerts:

• Traffic Advisory (TA) to assist the pilot in the visual search for the intruder aircraft and to prepare the pilot for a potential RA; and
• Resolution Advisory (RA) to recommend manoeuvres that will either increase or maintain the existing vertical separation from an intruder aircraft.

Once the risk is over, the TCAS issues a synthesised voice `clear of conflict' message.

The 737 crew were on their fourth consecutive day of duty and completing the last sector of a four-sector day when the incident occurred. It took place at the transfer of control point between Brisbane Centre and Darwin Approach. The 737 was en-route from Cairns to Darwin and was on descent to FL220. The Brasilia was enroute to Groote Island, under the control of Brisbane Centre, with instructions to maintain flight level (FL) 210. Those routes placed the two aircraft on almost reciprocal tracks. As the 737 was passing FL235, the crew were instructed by the Brisbane sector controller to contact Darwin approach control for further descent, but were not advised of the opposite direction traffic.

The Manual of Air Traffic Services (MATS) gave guidance to controllers on how best to manage the situation and advised:

`6.6.5.5 Frequency change management in relation to the transit of an aircraft across airspace boundaries shall be arranged in a manner that normally enables pilot communication with the unit responsible for the airspace within which the aircraft is operating. A lateral tolerance of 10 NM either side of the boundary is permitted, except that when entering controlled airspace, the frequency change shall be within the 10 NM prior to the boundary.

6.6.5.10 Aircraft should normally remain on the frequency appropriate to the airspace in which it is operating. However, aircraft may be transferred to another ATS frequency provided that:

1. significant operational advantage will be gained;
2. workload, communications and equipment capabilities will permit the responsible controller to take such action as is necessary to preserve the separation without delay;
3. the actual separation is in excess of the minimum;
4. there is no possibility of separation being reduced to the minimum with the normal operation of the aircraft.'

MATS does not require controllers to provide traffic information to either crew in these circumstances.

In order to comply with MATS 6.6.5.10, the Brisbane sector controller could have either:

• Initially assigned the crew of the 737, FL230 on descent, instead of FL220, then assigned the responsibility for separation to the Darwin approach controller, coordinating the terms of the transfer of the 737 with him, before transferring the aircraft to the Darwin approach frequency; or
• Assumed the separation responsibility, coordinated the terms of the transfer of the 737 with the Darwin approach controller, and transferred the aircraft once the 737 had passed the Brasilia and a horizontal separation standard existed.

Airservices Australia believed that MATS section 6.6.5.10 did not apply to a change of frequency in these circumstances. According to Airservices Australia the action of the Brisbane sector controller, in assigning the crew of the 737 FL220, was consistent with MATS in that the controller applied a 1,000 ft separation standard between the two aircraft and the 737 crew was transferred to the Darwin approach controller within 10 NM of the lateral boundary between the Brisbane sector and Darwin airspace.

Shortly after acknowledging the instruction to change frequency, the 737 crew received an aural `traffic, traffic' warning and a display indication of an aircraft 5 NM ahead. The pilot in command stated that the TA quickly changed to a RA with a `descend, descend, descend' aural alert. As the aircraft was approaching its assigned level he disconnected the autopilot and pitched the aircraft nose down with the intention of following the RA commands. He stated that the required rate of descent shown on the IVSI was 1,200-1,500 ft/min. On passing FL220 the TCAS command abruptly reversed to a climb RA (aural `climb, climb now') which was followed positively. The climb annunciation continued until the aircraft was at FL225. No more commands were issued and there was no TCAS `clear of conflict', which is normally generated once a RA is removed.

Analysis of recorded data indicated that as the 737 descended through FL230, its rate of descent was approximately 2,900 ft/min. At FL227, the automatic flight system commenced a transition manoeuvre to achieve level flight at FL220. At approximately FL225 the autopilot was disengaged and the descent was continued manually at a rate of descent in excess of 3,200 ft/min to FL215. That was followed by a climb to FL225 at 2,900 ft/min as the pilot responded to the RA reversal (`climb now' advisory).

Maintenance files from the TCAS computer were examined and no indication of TCAS failure was found. Technical expertise was requested from the manufacturer of the TCAS equipment. Their evaluation of the event presented two possible scenarios.

`Explanation 1. The reported `descend' advisory was actually a `reduce descent' advisory that was misunderstood by the crew. A `reduce descent' would be consistent with the expected TCAS response per the reported geometry of the aircraft. Because the advisory was misinterpreted, the rate of descent was increased rather than decreased until the aircraft was below the TCAS required 700 feet vertical separation. Thus, the TCAS was required to issue a `climb now' advisory. The lack of a `clear of conflict' annunciation is explained in the following paragraph.

`Explanation 2. There is a possibility that the intruder aircraft's (equipped with mode C transponder) altitude report was not correctly received by the TCAS. There have been instances when a Mode C reply will not contain all the appropriate pulses in the message or it transmits pulses that are too narrow for the TCAS to detect. This could cause differing altitude reports and could result in multiple unstable tracks at different altitudes for the same intruder aircraft. This being the case, the TCAS could have issued a `descend' advisory for the intruder because it appeared (due to erroneous altitude report) that it was actually above its own aircraft. If subsequent replies had the correct altitude, the erroneous track would be dropped by the TCAS and the TCAS would issue a `climb now' advisory on the track with the correct altitude.

`The reason that `clear of conflict' was not annunciated can be attributed to low track firmness of the intruder aircraft. Mode C equipped aircraft are typically only equipped with a single antenna mounted on the lower hull. Since the intruder aircraft was below the 737 aircraft, it is likely that the TCAS was not able to receive regular replies at close proximity. The TCAS computer unit will `coast' the track of a previously established intruder file if it does not receive a valid or reasonable interrogation response. If the track of the intruder that generated the RA is coasted during the time of the associated RA, then the `clear of conflict' is not announced.'

Since the incident, the operator's TCAS software has been updated to Version 7. The objectives of the Version 7 update were to further increase the safety benefits of TCAS, make TCAS more compatible with the procedures used by ATC and to address operational concerns identified by pilots operating the older versions of TCAS. Improvements to the aural annunciations included a change from `reduce descent, reduce descent' to `adjust vertical speed, adjust'.

The pilot and passenger of a Robinson R22 helicopter were conducting an aerial inspection and cattle mustering flight. During the flight, cattle were observed outside the fenced area and the pilot descended the helicopter to direct the cattle back towards the fence. The passenger then directed the pilot to fly the helicopter along the eastern fence to check its security. The passenger reported that the pilot had just commenced to climb higher, at his request, when the helicopter collided with a single-wire powerline. Recorded Global Positioning System data indicated that the helicopter struck the powerline at a speed of 55 kts. The wire did not break and the helicopter pitched nose down. The main rotor severed the tail boom and the helicopter collided with the ground 69 m beyond the powerline. It impacted in an inverted attitude, facing back along its direction of travel and rolled forward onto its left side. There was no evidence of fire in-flight or after the impact.

The main rotor, mast and upper right side of the helicopter cabin took the main impact and the mast was partially driven into the cabin. The pilot, who occupied the right seat, received fatal injuries. The passenger, although seriously injured, walked 200 m to a track and waited almost 2 hours until found by a passing motorist. The passenger reported that injury prevented him from picking up and activating the portable Emergency Locator Transmitter that was ejected from the helicopter cabin.

The powerline supplied electrical power to a nearby property and was aligned approximately east-west at right angles to the helicopter's flight path. It spanned a distance in excess of 500m from a pole in a saddle on a ridge east of the fence, to another pole set among trees in a timbered paddock. Strike marks on the wire indicated that the helicopter had struck the powerline at approximately mid-span. There were no markers on the powerline. Australian Standards (AS 3891.1-1991) specified markers on powerlines where the height of a cable exceeded 90m. The powerline did not exceed that height and at the point of contact was about 20m above ground level (AGL).

The pilot held a current Commercial Pilot Licence (Helicopter) and was appropriately qualified for cattle mustering operations. He held a valid Class 1 medical certificate and did not require any vision correction. An article on the visual aspects of wire detection by Dr Gordon Cable in the Directorate of Flying Safety-Australian Defence Force's special wirestrike edition (1997) of their safety journal "Spotlight" stated that under ideal conditions, the human eye can resolve detail down to an angle of 30 seconds of arc. That equated to being able to see a 5 mm thick wire from a distance of 150 m. However, contrast between the wire and the background against which it is viewed and the medium through which it is viewed, affect detection. The pilot was wearing a helmet with tinted visor. The fragments of perspex from the helicopter's windshield did not show any sign of being scratched or crazed.

The operator's Operations Manual required pilots to familiarise themselves with the area to be mustered, including any obstructions, before commencing mustering operations. Although the passenger had engaged the operator on previous occasions for the same work, no map of the area to be mustered was held on the operator's file. The passenger was aware of the existence of the powerline and stated that on previous occasions some pilots had him draw a "mud map" on the ground to indicate the area to be mustered, including powerline hazards. The pilot had reportedly not asked the passenger about any powerline hazards prior to the flight. There was no evidence that the pilot had previously flown over or inspected the area to determine the presence of hazards.

Forty minutes after departing Cairns en-route to Japan, the flight crew of the Boeing 747-300 aircraft noticed the number 5 left main entry door warning light illuminate. The flight engineer investigated and found that the door handle had moved from its fully locked 4 o'clock position to an unlocked 3-o'clock position. The flight engineer, with the assistance of one of the cabin crew, attempted to move the handle back to the fully locked position but was unable to do so. Returning to the flight deck, a check of the aircraft's technical logbook revealed that this problem had occurred on previous occasions. The pilot in command contacted the operator's maintenance headquarters, where he was advised that the door would not be able to open due to the cabin being pressurised and the flight could continue on to destination.

The cabin crew were advised to monitor the door for the rest of the flight. Shortly before landing, the flight attendant seated adjacent to the door observed the handle moving slowly upwards. Just prior to touch down, the door handle jumped to the 2-o'clock position at which time a loud wind noise could be heard. Leaving his seat, the flight attendant grabbed the handle and forced it down. Paper was observed being sucked under the door as the passenger seated directly in front of the door (adjacent to the window) turned and grabbed the door handle giving assistance in pushing the handle down towards the locked position. The handle reached the horizontal 3-o'clock position with the flight attendant keeping weight on it until the aircraft had landed and taxied to the terminal.

A minor adjustment of the door upper gate was carried out by maintenance engineers before the aircraft's next departure. The next two flights were uneventful, however on the third flight the left main entry door-5 warning light again illuminated and the handle moved from the fully locked to the unlocked, 3-o'clock position. On arrival at the destination, an inspection by engineers found the force required to move the door handle from the locked to unlocked position was lower than required, necessitating further adjustments to the door. An entry was also made in the aircraft's technical log for a full rigging check and an inspection of the door bearings to be carried out on the aircraft's return to its main base. The aircraft then flew for two further flights, without any reported defects, before returning to its main base.

Upon returning to the operator's main base, the door was removed and disassembled for an inspection of the door bearings. No defects were found and the door was returned to the aircraft where it was refitted and a rigging check carried out. The aircraft was then returned to service.

The Boeing 747 aircraft was being operated on a scheduled passenger flight from Melbourne to Perth with an estimated time of arrival (ETA) at Perth of 0945 WST. The flight crew had been provided with an aerodrome forecast (TAF) for Perth, valid until 0600 the following day, which indicated that the visibility and cloud base would be above the alternate criteria throughout the period of the forecast. As there were no operational requirements, the aircraft departed Melbourne without alternate or holding fuel being carried for Perth.

Three minutes after the aircraft's departure from Melbourne, an amended TAF for Perth was issued with fog being forecast until 0800. After that time, conditions at Perth were forecast to improve above the alternate criteria. A trend type forecast (TTF) for Perth, also issued soon after the aircraft's departure, indicated that the visibility would be reduced in fog until 0800. Subsequent Perth TTFs issued from 0635 until 0759 indicated that the visibility would be reduced in fog or mist until 0800 when the conditions were forecast to improve above the alternate criteria.

The FLAKE waypoint, 465 NM east of Perth, was the flight planned point of safe diversion (PSD) based on a return to Adelaide. The crew obtained the 0730 Perth TTF that indicated an improvement in conditions above the alternate criteria from 0800 and, as the aircraft proceeded to the FLAKE waypoint, the Perth TTFs continued to forecast that improvement. The aircraft passed the FLAKE position at 0824 and soon after, a Perth TTF was issued that indicated the meteorological conditions would be below the alternate criteria until 15 minutes after the ETA of the aircraft at Perth.

As the aircraft was not fitted with an aircraft communications addressing and reporting system (ACARS), the operator's flight dispatch section attempted to contact the crew via high frequency (HF) radio but the attempts were unsuccessful. At 0845, a message from the operator about the 0825 TTF was provided to the crew by air traffic services. As the aircraft had flown past the PSD and fuel was not carried to divert to an alternate airport, the crew decided to continue the flight to Perth. The aircraft made an uneventful landing at 0938.

A report from the Bureau of Meteorology (BoM) indicated that a weak cold front with a fragmented cloud band was expected to move through the Perth area between 0800 and 0830. No showers were expected ahead of the front and the BoM aviation forecasters assessed the formation of fog in the expected weather situation as being unlikely. However, a weak ridge formed overnight ahead of the front and in the light wind regime caused by the weak ridge, advection fog formed at Perth Airport.

As the front approached Perth it became apparent to the aviation forecasters that the frontal passage was being enhanced by north-easterly winds in the Perth area. This meteorological situation resulted in reduced visibility and low cloud being observed until 0930. The forecasters had not previously encountered this type of situation, which produced a mix of advection fog and frontal fog that was difficult to forecast.