The radar data indicated that the Warrior departed Jandakot via 'Yangebup Lake' and 'Lake Thomson', which were tracking points published for VFR aircraft departing to the south. After passing overhead Lake Thompson, the pilot of the Warrior turned onto a westerly heading, tracking towards the coast at an altitude of 1,500 ft. The aircraft turned onto a southerly heading approaching the coast and passed about 0.5 NM to the southwest of Shipyard (see Figure 1).

General Aviation Aerodrome Procedures (GAAP) were in use at Jandakot. Procedures published in the Airservices Australia Aeronautical Information Publication (AIP), ENR 1.1, 30.3(d) stipulated that when departing, the pilot must:

track via departure procedures (if any) for the particular GAAP aerodrome as specified in ERSA [En route Supplement Australia], or track well clear of GAAP approach points and associated VFR routes, to reduce possible conflict with inbound aircraft.

The ERSA entry for Jandakot stated that aircraft departing via Yangebup Lake should climb to an altitude above 1,500 ft as soon as practical upon leaving the control zone.

The AIP ENR 1.1, 31.5 stipulated that whenever possible, pilots of aircraft arriving from outside controlled airspace:

must track visually via a GAAP aerodrome approach point as specified in ERSA.

The ERSA nominated 1,500 ft as the inbound altitude for arriving aircraft and Shipyard as one of the aerodrome approach points.

The pilot of the Warrior held an overseas flight crew licence and was operating in accordance with a CASA-issued Certificate of Validation. That validation had been recently issued and recognised the pilot's overseas qualifications and permitted the pilot to operate Australian-registered aircraft, while engaged in private day VFR operations. As part of the process of validation, the pilot had undertaken training on local procedures for operating at Jandakot.

The pilot of the Warrior reported that he did not see the opposite direction aircraft.

At about 1125 Western Standard Time on 13 October 2004, a Cessna Aircraft Company 182R (C182), registered VH-WPF, was inbound to Jandakot at 1,500 ft. It was approximately 1 NM south of the aerodrome approach point 'Shipyard' when it conflicted with an aircraft travelling in the opposite direction. The pilot reported sighting the aircraft at close range and initiated a steep right turn to avoid a possible collision. The aircraft were outside controlled airspace and operating under the Visual Flight Rules (VFR). The Australian Transport Safety Bureau classified the occurrence as both an Airprox¹ and a serious incident². Recorded radar data and a subsequent radio transmission, positively identified the other aircraft as a Piper Aircraft Corporation PA28-151 (Warrior), registered VH-PMW.

1. An occurrence in which two or more aircraft come into such close proximity that a threat to the safety of the aircraft exists or may exist, in airspace where the aircraft are not subject to an air traffic separation standard or where separation is a pilot responsibility.
2. Annex 13 to the Convention on International Civil Aviation defines a serious incident as:
   An incident involving circumstances indicating that an accident nearly occurred.
   Note 1.- The difference between an accident and a serious incident lies only in the result.
   Note 2.- Examples of serious incidents can be found in Attachment C of Annex 13 and in the International Civil Aviation Organization's Accident/Incident Reporting Manual (Doc 9156).

The Australian Transport Safety Bureau did not conduct an on-scene investigation of this occurrence.

FACTUAL INFORMATION

On 11 October 2004, a Boeing Company 737-86Q (737) aircraft, registered VH-VOF, was being operated on a scheduled passenger service from Perth, WA, to Sydney, NSW. The copilot was the handling pilot for the flight.

At 1124 western standard time, as the aircraft became airborne from runway 03 at Perth, the cabin crew members seated at the rear of the aircraft felt and heard the aft fuselage scrape the runway. At about FL160 during the climb, the cabin crew alerted the flight crew of a possible tail strike during the take-off. The pilot in command assumed control of the aircraft and elected to return to Perth. The aircraft was descended to 9,000 ft, and during the descent the flight crew performed the 737 Quick Reference Handbook (QRH) Non-Normal Checklist for a tail strike on take-off. However, because no cabin pressurisation problems had occurred following the suspected tail strike, they elected to leave the aircraft pressurised.

Air traffic control cleared the crew to hold the aircraft to the west of Perth to allow sufficient fuel burn to reduce the aircraft to its maximum permitted landing weight, and the aircraft landed at Perth about 2 hours later.

Engineering inspection confirmed that the aircraft had sustained a tail strike during the take-off. The tail strike ground contact was slight, and resulted in minor scuffing to the base of the shoe on the tail-skid assembly. The crushable cartridge within the tail-skid assembly was undamaged.

The load trim sheet provided to the flight crew by the operator indicated that the planned take-off weight was 71,331 kg, which was used by the crew in conjunction with data from the operator's Airport Analysis Manual to determine the take-off speeds for the departure from Perth, using the full length of runway 03. Those speeds were the take-off decision speed (V1) of 142 kts, the take-off rotation speed (VR) of 147 kts, and the take-off safety speed (V2) of 151 kts.

Following the occurrence, all luggage and freight carried in the cargo compartments of the aircraft was re-weighed. The total cargo compartment load noted on the original load and trim sheet provided to the crew was about 160 kg less than the actual weight revealed by the re-weigh. The actual take-off weight was therefore 71,493 kg, and the take-off speeds for that weight were only 1 kt greater than the speeds determined by the flight crew. The minor discrepancy between the planned and actual weights was not a factor in the occurrence, and the aircraft was within its approved centre of gravity limits.

Perth aerodrome automatic terminal information service (ATIS) provided current, routine information to arriving and departing aircraft at Perth by means of continuous and repetitive radio broadcasts. Information Papa was current at the time of the occurrence and advised that the duty runway was runway 03 (wet), wind was 320 degrees magnetic at 20 kts, with an associated crosswind of 18 kts. The barometric pressure was 1010 hPa, and the temperature was 20 degrees C. The ATIS also included information that windshear was present in the vicinity of the aerodrome, and that the wind direction and speed at a height of 250 ft above ground level was 330 degrees magnetic at 25 kts, gusting to 35 kts.

The Bureau of Meteorology one-minute wind data at the time of the take-off indicated that the wind was a gusty crosswind. The average wind direction and speed was 325 degrees true at 19 kts. However, during the take-off, the wind direction and speed fluctuated between 319 and 331 degrees true, and from 18 to 21 kts.

The aircraft was fitted with an Allied Signal solid state flight data recorder. The ATSB analysed the recorded flight data to assist in establishing the factors that led to the tail strike.

The computed airspeed data revealed that acceleration was normal up to V1, at which point the aircraft's speed remained constant at 142 kts until rotation was initiated. At lift-off, the computed airspeed was about 152 kts. During the period between the commencement of rotation and the lift off of the main landing gears, the aircraft's nose-up pitch increased steadily from 0 degrees to 13.2 degrees. There was a 1.19g spike in the normal load factor data at the point of lift off.

About 23 degrees of left control wheel was applied throughout the take-off run until the aircraft was rotated. Left control wheel input increased from the point of rotation, and was about 43 degrees when the main landing gears became airborne. The left aileron was displaced 9.7 degrees up, and flight spoiler panels 3 and 4 were deployed 4.4 degrees and 11 degrees respectively at lift off. During the 2 seconds following lift off, left control wheel input increased to 48.8 degrees, then reduced to 28.7 degrees. The deployment of flight spoiler panels 3 and 4 increased to 13.9 degrees and 13.5 degrees respectively with the application of 48.8 degrees of left control wheel deflection. Right rudder was also applied during the take-off roll, which was consistent with the prevailing crosswind conditions.

Aircraft can achieve high angles of pitch relative to a runway during both take-off and landing segments of flight. If the pitch angle exceeds prescribed limits when an aircraft is close to the ground, the aft underside portion of the aircraft may contact the runway surface. That contact is referred to as a tail strike, and can result in significant damage to the aircraft. Aircraft manufacturers provide guidance to flight crews on the correct pitch rates and speeds to avoid tail strikes during take-off and landing manoeuvres.

The point of minimum tail clearance during take-off occurs after the lift-off speed has been attained. Initiation of rotation before the scheduled VR speed or rotation at an excessive rate will reduce the minimum tail clearance, and under those circumstances, contact with the ground will probably occur.

Chapter 3 of the operator's 737 Flight Crew Training Manual (FCTM) provided the following information on the take-off rotation manoeuvre:

When a smooth continuous rotation is initiated at VR, tail clearance margin is assured because computed takeoff speeds depicted in the QRH, airport analysis, or FMC, are adjusted to provide adequate tail clearance.

The FCTM also provided information that:

Take-off and initial climb performance depend on rotating at the correct airspeed and proper rate to the rotation target attitude. Early or rapid rotation may cause a tail strike.

The FCTM provided information that the lift-off attitude of the 737-800 was 8.2 degrees with the wing flaps extended 5 degrees. The minimum tail clearance at that pitch attitude was 51 cm, and the tail strike pitch attitude was 11.0 degrees with the main landing gear oleo struts extended.

The FCTM also provided information and recommendations on flight manoeuvres and techniques in gusty wind and strong wind conditions for the 737, as follows:

For take-off in gusty or strong crosswind conditions, maximum take-off thrust is recommended. This maximizes available runway and minimizes the airplane exposure to gusty conditions during the rotation and take-off maneuver [sic].

Avoid rotation during a gust. If a gust is experienced near VR, as indicated by stagnant airspeed or rapid airspeed acceleration, momentarily delay rotation. This slight delay allows the airplane additional time to accelerate through the gust and the resulting additional airspeed improves the tail clearance margin. Do not rotate early or use a higher than normal rotation rate in an attempt to clear the ground and reduce the gust effect because this reduces tail clearance margins. Limit control wheel input to that required to keep the wings level. Use of excessive control wheel may cause spoilers to rise which has the effect of reducing tail clearance limits. All of these factors provide maximum energy to accelerate through gusts while maintaining tail clearance margins at liftoff.

The aircraft manufacturer advised that deflection of flight spoilers and ailerons due to control wheel input reduces the lift coefficient of the wing and that the reduction in lift coefficient effectively reduces the tail clearance at rotation during the take-off manoeuvre.

The Terminal Area Forecast (TAF) provided information to the crew that moderate turbulence was likely to be encountered during the flight. The meteorology information provided no warning of severe turbulence until after the flight had landed at the Gold Coast. The TAF that the crew had used indicated that the change in wind direction and strength at 1600 would signify the passage of the front over the Gold Coast.

The turbulence encountered during the Dash 8's initial approach and the visual observations reported by the crew of a roll cloud and water spouts, were consistent with the aircraft having encountered the leading edge of the frontal zone. This was about 2 hours earlier than forecast. The indications from the weather stations at Evans Head and Cape Byron confirmed that the front was moving to the north faster than expected. However, the severe turbulence associated with the front could not be determined from those weather stations and was therefore unexpected.

The drop in temperature of 7 degrees provided the pilot in command of the B717 with an indication that conditions at the Gold Coast Airport were changing earlier than forecast. This temperature drop was also recorded by the automatic weather station at the Gold Coast Airport. While the drop in temperature cannot by itself indicate the degree and/or severity of turbulence likely to be encountered, it did indicate the arrival of the front.

As the aviation special weather report issued at 1258 was not passed to the crew of TNW, they were not in a position to appreciate that the passage of the front over the Gold Coast Airport was earlier than expected. The crew were aware that the B717 had encountered turbulence in the area of the Gold Coast Airport, but were not fully aware of the severity of that turbulence.

During the missed approach, the flap 5 limit speed was exceeded for a short period of time. At the time, the crew were likely to have been preoccupied with the low oil pressure warning and maintaining control of the aircraft due to the turbulent conditions. The overspeed did not result in damage to the aircraft. The extreme roll rates encountered by the aircraft could have given the perception that the aircraft rolled to unacceptably high roll angles, however the data recovered from the flight data recorder revealed that the roll angles encountered were within normal operating parameters.

The changes recorded in vertical `g' readings were indicative of a severe turbulence encounter. The decision by the crew to conduct a missed approach due to the turbulence was in accordance with normal operating procedures.

The Australian Transport Safety Bureau did not conduct an on-scene investigation of this occurrence.

FACTUAL INFORMATION

At approximately 1330 Eastern Standard Time (EST) on 8 October 2004, a de Havilland Canada DHC-8-102 (Dash 8) aircraft, registered VH-TNW (TNW), with a crew of three and 18 passengers, encountered severe turbulence during approach to the Gold Coast Airport, Queensland. The aircraft was being operated on a scheduled passenger service from Brisbane to the Gold Coast.

The flight crew reported that conditions were quite rough with moderate turbulence during the flight. Approximately 25 NM from the Gold Coast Airport, at an altitude of 5,000 ft, the aircraft encountered turbulence that resulted in a wing drop, while operating with the autopilot engaged. The crew were then cleared by air traffic control (ATC) to descend to 4,000 ft and to reduce speed, as they were being radar vectored behind a Boeing Company 717 (B717) aircraft that had conducted a missed approach at the Gold Coast Airport due to encountering turbulence.

The crew of TNW reconfigured the aircraft for a flap 15 landing. They were then advised by ATC that they would be in front of the B717, were cleared for a visual approach and advised to contact the control tower. Passing through approximately 2,500 ft, the crew reported that they encountered a severe updraft that stopped the aircraft's descent. They then disconnected the autopilot and continued the descent. The crew reported that as the aircraft was passing through approximately 1,500 ft, they encountered severe turbulence, which required them to apply almost full control inputs to control the aircraft. The pilot in command then carried out a missed approach and the aircraft was reconfigured for a climb. During the missed approach, the number 1 engine `low oil pressure' warning light illuminated for a short time. The crew checked the cockpit indications and confirmed that the oil pressure was within limits.

They climbed the aircraft to 3,000 ft and manoeuvred for another approach. The pilot in command reported that during the downwind leg they observed that the water off the coast appeared to be `foaming'. He also reported a number of small waterspouts present, and that there appeared to be a roll cloud forming ahead of the aircraft.

After landing, the crew advised the ground engineers that they had encountered severe turbulence. Following discussions with the operating company's base, a decision was made to ground the aircraft to allow a thorough engineering inspection. That inspection was to include flap over-speed and severe turbulence encounter inspections.

A review of the recovered data from the aircraft's flight data recorder revealed that, at a recorded altitude of 1,460 ft, the aircraft encountered a turbulence event that recorded +2.26 vertical `g'. At that point, the aircraft was banked to the left to 21 degrees. Almost immediately following this, the aircraft banked to the right to 20 degrees. The data also revealed that during the missed approach the engine torque values exceeded 100% for a period of two seconds and that the flap 5 limit speed of 148 kts was also exceeded.

The aircraft was not damaged during the turbulence encounter and none of the occupants were injured.

The pilot in command of the B717 reported that, when they had started descent, they were advised that the automatic terminal information service (ATIS) had changed. The new information that they received indicated that the temperature had dropped 7 degrees from the temperature that they had recorded just prior to starting the descent. He also reported that the conditions became very turbulent as the aircraft descended below 10,000 ft. While on approach, the conditions became very turbulent, and he conducted a missed approach when the aircraft became unstable on the approach.

The general meteorological forecast for the morning of 8 October 2004 indicated that a trough line was moving across south-east Queensland. Coincident with the movement of this trough, a front was moving north along the New South Wales coast and was expected to move through south-east Queensland in the mid to late afternoon.

The Terminal Area Forecast (TAF) for the Gold Coast Airport, issued at 1104, indicated that the wind was from 300 degrees at 18 kts, with gusts to 30 kts. It further indicated that the wind was to change direction and strength at 1600. The TAF also indicated that moderate turbulence was expected below 5,000 ft from 1100 until 1700.

An amended TAF was issued at 1335, which indicated that the wind was from 160 degrees at 20 kts. This TAF also indicated that moderate turbulence was expected below 5,000 ft from 1300 until 1700.

Data from the automatic weather station (AWS) at the Gold Coast Airport indicated that the wind direction started to change from a north-westerly direction to an easterly and finally a south-easterly direction between 1230 and 1326. The recorded temperature also decreased from 34.6 degrees to 26.8 degrees in the same period. An aviation special weather (SPECI) report related to a change in wind direction and a drop of temperature of more than 5 degrees was issued by the Gold Coast Airport AWS at 1258. That information was not passed to the crew of the TNW.

A significant meteorological (SIGMET) warning of severe turbulence was issued at 1449 that covered the area surrounding the Gold Coast Airport. This turbulence was expected below 8,000 ft.

The passage of the front along the New South Wales coast was detected by automatic weather stations at Evans Head and Cape Byron. These stations did not have the capability to provide 1-minute updates to the data. Therefore, they could only provide aviation routine weather (METAR) and SPECI reports.

SPECI data from Evans Head and Cape Byron stations indicated the passage of the front through those locations at 1025 and 1131 respectively.

Sequence of events

At 1940 eastern standard time (EST), on 4 October 2004, the Boeing Company 737-300 aircraft, registered ZK-FDM, became bogged (Figure 1) at Melbourne Airport. The aircraft was being taxied to runway 27 for a scheduled international passenger service to Hamilton, New Zealand.

Figure 1: Left main landing gear tyres after penetrating the blast-protection surface adjacent to taxiway Papa.

The flight crew commenced taxiing the aircraft to runway 27 from bay 'Delta 4' at the international terminal. Taxiing to Papa¹ via Tango was not available because of the stage A2a works in progress on the northern apron (depicted at Attachment 1), and the surface movement controller (SMC) instructed the crew to taxi the aircraft via Sierra and Echo to the runway 27 holding point on Papa. As the aircraft approached Sierra the crew requested confirmation of the taxiing instructions, and the SMC repeated those previously given. The SMC then told the crew to contact the aerodrome controller (ADC) on frequency 120.5 MHz.

The flight crew subsequently reported that while taxiing east along Echo, their attention had been drawn to the lighting associated with the apron works near the intersection of Tango and Papa. There was a holding bay located north of Echo, and the first lead-in light to the holding bay was about 40 m west of the first lead-in light to Papa. As the aircraft approached the lead-in lights to the holding bay, the pilot in command stopped the aircraft. The copilot asked the ADC "is it hard left Papa here?"

The ADC was located in the aerodrome control tower, which was about 1,450 m to the west-southwest of the aircraft's position. From the ADC's vantage point, and in the night conditions, the aircraft would have appeared to have been at the lead-in to Papa, and the ADC confirmed to the crew that it was Papa.

The pilot in command, in response to the advice from the ADC, turned the aircraft left and began to enter the holding bay, thinking it was taxiway Papa. It then became obvious to the crew that they were not on Papa, and the pilot in command turned the aircraft to the right to regain taxiway Echo and the lead-in to Papa. He subsequently reported that another aircraft taxiing on Quebec for runway 27 had its lights 'very brightly shining', and that he misidentified the double lines on the taxiway shoulder as being the taxiway centreline. As a result, the pilot in command inadvertently steered the aircraft onto the blast-protection surface adjacent to the taxiway shoulder pavement. The left main landing gear tyres of the aircraft penetrated the blast-protection surface, and the aircraft became bogged.

The aircraft could not be moved from its bogged position, and the 104 aircraft occupants, which comprised two technical crew, three cabin crew and 99 passengers, were disembarked and taken back to the international terminal.

The aerodrome operator reported that all airside signs, markings and lights complied with ICAO standards and CASA regulations, and that they were serviceable and operating normally at the time of the occurrence. The circumstances of the occurrence did not suggest that there were any deficiencies in the aerodrome airside signs, markings and lighting systems.

The aircraft weight and balance data for the planned flight revealed that its taxi weight was 54,434 kg, and the centre of gravity was at 20.4 percent mean aerodynamic chord. Under those conditions, about 90 percent (49,500 kg) of the aircraft's total landing gear pavement load was exerted by both the main landing gears, that is, each main landing gear pavement load was about 24,750 kg. The left main landing gear pavement load was of sufficient magnitude to result in the left main landing gear tyres penetrating the blast protection surface.

The aircraft was recovered from its bogged position on the following day and subjected to a heavy landing engineering inspection. The inspection revealed no damage resulted from the incident, and the aircraft was returned to service.