The SMC did not anticipate the aircraft conflict. The night environment, lack of aircraft taxi lights and the distraction with entering system data may have limited his situational awareness despite the availability of the SMR. The use of a segmented or a conditional clearance to the pilots of either aircraft would have assured that the aircraft would not conflict. Alternatively, the SMC could have requested assistance to either enter the system data, or to monitor the taxiing aircraft visually or by using the SMR.

The situational awareness of all the pilots was reduced by the lack of specific traffic information on the other potentially conflicting aircraft. They did not see the other aircraft's taxi light as they carried out their standard lookout. Even if the other aircraft had been seen, it may have been interpreted as an aircraft holding, or even preparing to give way, because the taxi light was selected off.

Both aircraft were being taxied at speeds that limited either crews' ability to react to a conflict in a known busy area of the airport. In this instance a slower taxiing speed would have been appropriate. However, a limiting factor for both aircraft was the lack of a practical means to monitor or assess groundspeed, especially at night.

The SMC's use of the term 'expedite' and a perceived need to not delay taxiing, to assist both pilots and controllers, may have led the pilots of both aircraft to taxi faster than they might normally do. While high taxi speeds may be acceptable in some locations on the movement area, reduced taxi speeds are warranted in potential areas of conflict near runway exits, multiple crossing taxiways and apron access areas. The use of slower taxi speeds in those areas should assist pilots to more readily maintain separation from other taxiing aircraft while complying with air traffic control clearances.

The requirement for pilots to monitor the company frequency throughout the taxi period is a potential distraction for pilots, when the priority for their attention should be on operational duties. Procedures for non-operational radio usage could be better managed so as to have minimal impact on operational duties. This is particularly relevant in a busy taxiway environment like Sydney Airport. If the Dash 8 copilot had also been busy or distracted, a collision may have occurred.

On 2 July 2004, at about 1805 Eastern Standard Time, a de Havilland DHC-8-315 (Dash 8) was taxiing at Sydney Airport for a night departure on a scheduled fare-paying passenger flight to Williamtown, NSW. The Sydney Tower Surface Movement Controller (SMC) had issued a clearance for the crew of the Dash 8 to taxi from Domestic Terminal 1 to the holding point for runway 16 Left. The clearance was via taxiway Charlie, across runway 25 to Bravo 10.

Figure 1: Sydney aerodrome chart

A Saab 340F (Saab) had landed on runway 16 Right and taxied from that runway via runway 25 then turned left onto taxiway Bravo. The SMC issued a clearance for the crew to taxi via taxiway Golf to the apron. The SMC had instructed the crew of the Saab to expedite. The dictionary definition of expedite means to 'speed up the progress of, or to hasten'. The Saab pilot in command (PIC) interpreted this instruction as to not waste any time and to keep the aircraft moving but at a safe speed.

As both aircraft were about to enter the intersection of taxiways Golf and Charlie (see figure 1), the copilot of the Dash 8, seated on the right of the cockpit, saw the Saab. He called for the PIC to stop. The PIC brought the Dash 8 to an abrupt stop as the Saab taxied through the intersection at a constant speed. Neither of the PICs saw the other aircraft until they had crossed at the intersection. The copilot of the Saab was busy with after-landing duties during the initial taxi period after vacating the runway. As the Saab taxied through the intersection he was occupied with a company frequency transmission on the radio and did not see the Dash 8 at any stage. The SMC was unaware of the situation until queried by the PIC of the Dash 8 regarding which aircraft had right of way.

A replay of the surface movement radar (SMR) of the occurrence showed that the taxi speed of the Saab was 26 knots. At 1800:08, the taxi speed of the Dash 8 was 21 knots. It then decelerated and stopped at 1800:11 with the Saab passing directly in front, moving from right to left. The SMR displayed the distance between the aircraft as 42 m. The impression of both PICs was that the aircraft passed in very close proximity.

Normally, pilots use a technique of scanning left and right to check for other aircraft that may conflict with them at intersections. Generally pilots on the left observe the left side and those on the right observe the right side. The standard procedure for the Saab operator was for pilots to survey the area to both the left and the right of the aircraft before entering or crossing any taxiway.

Neither operator had a policy or general guidance material in relation to aircraft taxi speeds, although the Saab operator did require turns in the aircraft to be 'at a speed below 20 kts'. Consequently, the speed at which aircraft were taxied varied between pilots.

Pilots recalled taxi speed limits from their training as 'fast walking pace' but agreed that this was impractical over the long distances involved at Sydney Airport. Neither the Civil Aviation Regulations (CARs) nor the Aeronautical Information Publication (AIP) nominate any specific aircraft taxi speed limits.

A groundspeed readout (utilising a Global Positioning System (GPS)) is available in the Dash 8, but its use is limited by its position on the lower pedestal in the cockpit. This makes it difficult for pilots to cross refer to it while taxiing and looking out for other taxiing aircraft. Similarly, a groundspeed readout is available in the Saab from either the lower pedestal or from the electronic horizontal situation indicator. In addition, a pilot's ability to estimate speed is more difficult at night due to the lack of visual cues used in judging the relative motion of the aircraft with other objects.

The Saab taxi light was unserviceable. The pilots' recollection of the event indicates that the Dash 8 taxi light was not illuminated. Some pilots turn taxi lights off while holding or passing close to other aircraft, to prevent a dazzling effect. The navigation lights and rotating beacons of both aircraft were operating. Both aircraft were backlit to some degree by the domestic terminal and suburban lighting on the far side of the airport.

The SMC was operating the SMC east and SMC west positions on combine. Immediately prior to the occurrence, the controller was endeavouring to manage the arrival and departure from the apron of four aircraft while updating radar system data. System updating included the assigning of labels to radar returns on the SMR for aircraft taxiing for departure. The controller was aware of the disposition of aircraft but his impression, at the time he issued the clearance to the crew of the Dash 8, was that the Saab would pass through the intersection before the Dash 8 would be near that intersection. Consequently, he did not provide traffic information on the other aircraft to either crew, nor did he assess that there was a need to use a segmented or a conditional clearance to either crew. A segmented clearance enables a crew to taxi and to stop at a possible point of conflict, while a conditional clearance enables a crew to taxi subject to specified requirements. In this situation, the Dash 8 crew could have been instructed to taxi and to hold short of the intersection of taxiways Charlie and Golf; or alternatively, to taxi to the runway, with a requirement to pass behind the Saab on taxiway Golf.

Even though crews receive and acknowledge clearances to taxi on the aerodrome manoeuvring areas, the CARs and AIP put the onus on the PIC to maintain a good lookout and observe other traffic to avoid collision.

Both airlines have a procedure where one or both of the pilots listen (and transmit as required) to the company frequency from taxi to just before take off and, from after landing till after shutdown at the parking bay. The Saab copilot was the only pilot reported to be operating a radio at the time of the occurrence.

Sequence of events

On 19 June 2004, at about 1908 Coordinated Universal Time (UTC), two Australian registered Boeing Company 767-338ER aircraft were involved in a serious incident in the Ujung Pandang Flight Information Region (FIR) on air route B473, approximately 60 NM northwest of waypoint SAMGE (latitude 02o21/10//N, longitude 129 o39/00//E).

Flight number QF 83, registered VH-OGP was northbound and flight number QF 98, registered VH-OGQ was southbound on the same air route. The crew of QF 83 reported at SAMGE at 1901 UTC. The crew stated that Ujung Control cleared the crew to `Descend flight level (FL) 350, cross SADAN at FL350 and report leaving FL360'. At about 1906, while continuing to maintain FL360, the crew observed an aircraft (QF 98) on the reciprocal track. The crew of QF 98 were cruising at their cleared level of FL350. This aircraft passed 1,000 ft below QF 83 at about 1908. The crew of QF 98 asked Ujung Control to confirm their clearance. The controller then replied `Maintain FL360, report at time 1917'. If the crew of QF 83 had descended their aircraft from FL360 to FL350 there would have been an infringement of separation standards and an increased risk of collision, with QF 98.

The Australian Transport Safety Bureau (ATSB) was advised of the incident and commenced an investigation. The crews of both aircraft were interviewed and data from each aircraft's quick access recorder was analysed. A review of that data subsequently revealed that the incident occurred inside Indonesian territory. Accordingly, the Indonesian National Transportation Safety Committee (NTSC) had the responsibility to conduct an investigation in accordance with Annex 13 to the Convention on International Civil Aviation.

On 8 July 2004, the NTSC informed the ATSB that they had commenced an investigation into the incident and the ATSB appointed an accredited representative to that investigation. The NTSC, being the investigation agency of the country in which the incident occurred, will be preparing the report and has control over the public release of any investigation findings.

The ATSB will publish the NTSC report on its website www.atsb.gov.au when released by the NTSC.

Factual Information

On the morning of 18 June 2004, a Saab 340 aircraft, registered VH-KEQ, with a crew of three and 31 passengers, was being operated on a regular public transport flight from Albury to Melbourne, Vic. The pilot in command (PIC) had levelled the aircraft at flight level (FL) 120 (12,000 ft) with indicated air speed (IAS) and half bank selected on the autopilot. The engine anti-ice system and propeller and airframe de-ice systems were activated.

The PIC reported that the outside air temperature was -10 ºC, while the IAS was 145 to 150 kts. As the PIC increased the propeller RPM to aid with ice shedding, the IAS rapidly decreased to 137 kts. The PIC disconnected the autopilot and initiated a descent to 10,000 ft. During the autopilot disconnection, the stick shaker activated for about 1 to 2 seconds. The PIC reported that there were no autopilot miss-trim indications during the event. Ice was still present on the aircraft radome after landing.

The stall warning system fitted to the Saab 340 consists of two independent dual channel stall warning computers, left and right angle of attack sensors, two stick shakers and a stick pusher. The system provides five distinct warnings of an impending stall, commencing with stick shaker and aural clacker, followed by autopilot disengage, a visual warning in the form of stick pusher initialisation lights on the instrument panel, and a stick pusher.

The stall warning computers receive inputs from separate angle of attack sensors that are situated on the forward section of the fuselage, which measure airflow relative to the fuselage. Activation of the wing de-ice system increases the angle of attack signal by 0.4 degrees to increase the stall margin by 1 to 2 kts when the de-ice boots are inflated.

The stall warning computer activates the stick shaker at 12.5 degrees angle of attack and the stick pusher at 19 degrees angle of attack, with zero flap deflection and wing de-ice systems deactivated. Activation of the stick shaker causes the autopilot to disengage. Initiation of this warning for both pilots occurs when either of these sensors reaches the predetermined angle of attack. The stick pusher command requires a stall warning output from both sensors, while one or both sensors is required for stick pusher in the event of stall identification.

Following the incident, the data from the aircraft's flight data recorder was downloaded and analysed by the Australian Transport Safety Bureau (ATSB). The data indicated that from the time the aircraft levelled at FL120, the autopilot was maintaining that flight level by providing nose-up elevator movement and automatically re-trimming. At the same time, the IAS was decreasing and the angle of attack was increasing. About one minute later, the RPM of the propellers began to increase from 1,240 RPM to 1,370 RPM. However, over the same period, torque values decreased from 73 to 65 percent and the IAS continued to decrease.

About 1 minute later, with an IAS of 134 kts, the angle of attack reached the value required for stick shaker activation and the autopilot was disconnected. However, because of the disconnection, the subsequent nose-down elevator movements are considered to have been in response to control inputs from the crew, thus the angle of attack did not reach the value required for operation of the stick pusher (19 degrees).

No airframe buffet was evident in the recorded lateral, longitudinal or vertical acceleration data for this event. Recording limitations (sampling rates and the accelerometer frequency response) mean that light buffeting may have occurred and not been evident in the recorded data.

The stick shaker and subsequent control inputs from the crew were initiated before a loss of control of the aircraft.

Recorded data of the incident.

An investigation by the operator following the incident indicated that the probable reason for the rapid decrease in IAS was the altitude capture mode being used at the time of the incident.

As the aircraft approaches the altitude selected on the autopilot, the autopilot will command a capture profile and will hold the selected altitude. The capture point is variable and it is a function of the vertical speed. For this to occur, the autopilot changes the mode from IAS to ALTS (altitude capture) mode, thus giving no airspeed protection during the transition of modes. Without an increase in engine power the airspeed will decrease if the autopilot continues to increase the angle of attack to maintain the captured flight level.

The flight recorder data was also forwarded to the manufacturer to conduct further analysis to establish the reason for the stall and ascertain if the aircraft 'behaved' according to type design. The manufacturer commented that above 10,000 ft, the rate of climb began to decrease and reaching 11,600 ft, the rate of climb had reduced to almost zero. The IAS was 160 kts with propeller RPM 1,240 and engine torque of 69% and 73% on the left and right engine respectively. Thirty five seconds after reaching 11,600 ft the aircraft began climbing at the same time as the indicated airspeed reduced to 150 kts. The aircraft then levelled off at 11,900 ft before making a final altitude adjustment, reaching 12,000 (FL120) at 145 kts, while propeller RPM remained constant at 1,240, but then began increasing about 60 seconds later. Approximately 30 seconds after reaching FL120, the IAS began reducing, until the aircraft entered a stall 100 seconds later. The autopilot, which had been engaged during the climb, was disengaged at the stall warning activation. The aircraft recovered from the stall and descended to 10,000 ft.

The manufacturer commented that the data, illustrated two indications of a stall. The first indication was the increase in angle of attack with no or very small increase in the corresponding lift coefficient. The second indication of a stall was the hysteresis effect in the lift curve seen during the stall. As the aircraft entered the stall and the angle of attack was reduced, the aircraft was not able to attain the normal lift coefficients until the angle of attack was significantly reduced. The analysis also shows that the hysteresis effect was rather moderate, which indicated that the stall had began to build, but was not fully developed, that is, not all parts of the wing were stalled. It is possible that due to the partial stall, the crew may not have recognized it as a stall, especially if control inputs were made simultaneously.

The manufacturer reported that the stall, which happened approximately two and a half minutes after reaching top of climb at FL120, was probably caused by a combination of significant, or extreme, ice accumulation on the airframe, possibly also in combination with run-back ice accretion on the propeller blades. There is an indication from the analysis of the data, that ice was accumulating on the airframe and possibly also on the propeller blades during the final part of the climb above 10,000 ft. The aircraft encountered an aerodynamic stall at the same time as the stick shaker was activated and the autopilot was disconnected. The indicated airspeed at the time of stick shaker activation was 134 kts. The aircraft sustained a moderate roll disturbance to the left during the stall, which was corrected by the crew with moderate opposite aileron deflection. The manufacturer estimated that when the aircraft encountered the stall, the accumulated ice had a combined effect corresponding to a drag increase of more than 500 drag counts, which is in the same order as the total aerodynamic drag for an aircraft without ice accumulation.

The procedure as prescribed in the Aircraft Flight Manual - ref 3 (AFM), as well as in the Aircraft Operators Manual - ref 3 (AOM), is to operate the de-ice boots at the first sign of ice build up anywhere on the aircraft. It is recommended to use the continuous mode of the de-ice boot operation. The continuous mode automatically starts a de-ice boot cycle each 3 minutes and each cycle takes about 30 seconds. However, ice formation on the airframe might in some conditions be so severe that manual de-ice boot operation will be necessary to avoid large ice build-up on the leading edges.

The manufacturer commented that the findings from their aerodynamic analysis show that there was significant, or even extreme, ice accumulation on the wing leading edges as well as other parts of the airframe. It was not possible to determine from the recorded data, if or when the de-ice boot system was operated. Considering the significant increase in aerodynamic drag during the last minutes before entering the stall, the de-ice boot system was probably not operated manually to further enhance the de-icing capability. Had the de-ice boot system been manually and frequently operated during the final part of the climb and during the short cruise segment before entering the stall, ice accumulation would most likely still have been present, but with a significantly less amount and subsequently with less aerodynamic consequence.

According to the manufacturer, the procedures prescribed in the AFM and AOM stated that the propeller de-ice system should be operated in the NORM mode for temperatures between -5 ºC and -12 ºC and MAX mode at temperatures -13 ºC or colder.

Using MAX or NORM modes at warmer temperatures than specified may result in the ice melting, running backwards and refreezing in the form of ridges behind the propeller boots, instead of being shed off the blades. The so-called run back ice will cause a drastic reduction in propeller thrust, up to about 30%.

Above -5 ºC the centrifugal self-shedding capacity is usually enough to avoid ice build-up. Should ice build-up be severe, it is recommended to increase propeller RPM to improve the self-shedding capacity.

From the recorded data, the manufacturer concluded that the aircraft reached an outside air temperature of -5 ºC when climbing through 9,500 ft. Considering the significant loss in rate-of-climb above approximately 10,000 ft, there is a possibility that part of this can be attributed to loss of thrust. The recorded data also reveals that the propeller RPM was low for a climb in icing conditions, approximately 1,240 RPM, which might have reduced the centrifugal self-shedding capacity. The fact that the crew, shortly before entering the stall, increased the propellers to maximum RPM, might indicate that the crew suspected ice formations on the propeller blades.

It is likely that the aircraft had more ice accumulation than the crew realised, which resulted in a degradation of aerodynamic performance that led to a decrease of the IAS, and the subsequent stick shaker activation. Additionally, the crew did not increase power to compensate for the decreasing IAS as the autopilot attempted to maintain altitude by trimming the aircraft to increase angle of attack.

The pilot in command (PIC) of a Saab 340 registered VH-KEQ, had levelled the aircraft at 12,000 feet (FL120) with IAS and half bank selected on the autopilot. The aircraft engine, propeller and airframe anti-ice and de-ice was activated.

The PIC reported that the outside air temperature was minus 10 degrees while the indicated airspeed (IAS) was 145-150 knots. As the PIC increased the propeller RPM to aid with ice shedding, the IAS rapidly decreased to 137 knots. The PIC disconnected the autopilot and initiated a descent to 10,000 feet. During the autopilot disconnection, the stick shaker activated for about 1 to 2 seconds. Ice was still present on the aircraft radome after landing.

The recorded data indicates that from the time the autopilot levelled the aircraft at FL120 the autopilot was maintaining the flight level by providing nose-up elevator movement and automatically re-trimming. At the same time, the IAS was decreasing and the angle of attack was increasing.

About one minute later, with an IAS of 134 knots, the angle of attack reached the level required for stick shaker activation.

A company investigation indicated that the probable reason for the rapid decrease in IAS was most likely caused by the altitude capture mode at the time of the incident.

A manufacturer investigation reported that the wing partially stalled, probably due to a combination of significant ice accumulation on the airframe, and run-back ice accretion on the propeller blades.

The company decided that the current Crew Simulator programme, containing elements of unusual attitude recovery and flight in severe icing conditions, would be extended until the new flight proficiency simulator programme had been trialled and approved. During a visit, the manufacturer informed Australian operators about winter operations in icing conditions.

The Australian Transport Safety Bureau did not conduct an on-scene investigation of this occurrence. The report presented below was prepared principally from information supplied to the Bureau.

REPORTED INFORMATION

At 1855 on 21 June 2004, a Boeing 717-200 aircraft, registered VH-VQB, was being prepared for departure at gate 49 at Sydney Airport. At the same time, another company Boeing 717-200 aircraft, registered VH-VQE, was being prepared for departure at the adjacent gate 53.

Both aircraft had been prepared for pushback and had remote control Power Push Units (PPU) positioned on the respective aircraft main landing gear. VQB was in the final stages of preparation for departure with all ground service equipment clear of the aircraft, all passengers on-board and seated with door 1 Left (L1) open and the aerobridge connected to the aircraft. The cabin service manager was completing documentation in the aircraft near door L1, and two customer service officers were located on the aerobridge.

VQE was ready for departure ahead of schedule and the flight crew received a pushback clearance. They then advised the ground crew that the aircraft was 'clear to push'. A push back was commenced by a ground crewmember, using a hand-held remote control unit, however the PPU did not respond to the ground crew's command to commence reversing. The ground crewmember, initially believing the remote control unit battery was discharged, replaced the battery and attempted a second pushback without success.

At the time the command to pushback was sent to the PPU attached to VQE at gate 53, VQB began to move rearwards at gate 49. The flight crew of VQB, sensing the unexpected movement, immediately applied the aircraft brakes; however, the aircraft had moved rearward more than a metre. As the aircraft moved, the two customer service officers in the aerobridge became unsteady on their feet and a flight attendant in the aircraft galley received a minor scratch on one arm. Once the aircraft was stopped and secured, all passengers were disembarked through door 1 Right using portable stairs.

A subsequent examination of the aircraft revealed that VQB had been damaged as a result of contact between the aircraft and the aerobridge. The left angle of attack vane was bent, there was some minor skin damage around the angle of attack vane mounting and the L1 door trim was damaged. The damage was repaired and the aircraft was returned to service the following day.

Aircraft Ground Handling

Ground handling services for the aircraft operator were provided by a contracted ground handling agent. The agent owned and operated the PPUs and trained staff in their operation. The PPUs were attached to the aircraft main landing gear and provided motive force for aircraft pushback without the need for a towbar. The PPUs were activated via a hand-held remote control unit. The remote control units had an operating range of approximately 100 metres and were digitally encoded to ensure that the remote control unit would only operate its assigned PPU. The two PPUs and controllers used by the operator in Sydney were marked with matching serial numbers and two amber lights would illuminate on the PPU when any remote control button was pushed, signifying that the PPU was the one being activated.

At the time of the occurrence, the ground handling crews for gates 49 and 53 had inadvertently obtained the incorrect remote control units for their respective PPUs prior to the commencement of aircraft pushback.

MD Helicopters, Model MD520N, VH-MPI, 21 June 2004

Examination brief

The right front and rear landing gear strut assemblies from the helicopter (without fairings) were submitted to the ATSB's Canberra Technical Analysis Laboratory for examination and analysis of the failures. The parts were identified as follows:

Front strut:	91 - 369H 6001-42 D Rev. 6 1-24-91 S/O. A0201132
Rear strut:	PNo: 369H 6001-32

The front strut carried the identification as ink stencilled print on the elbow section of the assembly. The rear strut did not carry any permanent markings and was identified solely by reference to the attached tag.

The aircraft coordinated estimate RIGMI at 0338 UTC. The aircraft passed seven minutes late, nil details were passed on from the New Zealand control centre.

At about 0630 Eastern Standard Time on 21 June 2004, a MD Helicopters MD520N helicopter, registered VH-MPI, took off from Gladstone, Queensland, to transport a marine pilot to the deck of a bulk carrier ship that was preparing to enter Gladstone harbour. During the landing on the ship, the right landing gear struts fractured. The helicopter collapsed onto its right side and the main rotor blades struck the ship's deck. The helicopter was substantially damaged and the pilot and passenger exited the helicopter uninjured.

The pilot satisfied Civil Aviation Safety Authority (CASA) recency requirements and was familiar with both the helicopter and the mission to be flown. He reported that he had conducted over 100 deck landings and was familiar with landing on ships of the type involved in the occurrence.

The pilot reported that weather conditions were fine with a clear sky, temperature about 17 degrees Celsius, wind from the south-west at about 25 knots, and a slight sea state.

The ship had a number of large hatches aligned longitudinally along the deck. The pilot was using one of those hatches as a landing area. The hatch was of a suitable size to accommodate the helicopter and there were no obstructions in the vicinity of the landing area. The pilot reported that the ship was underway and steaming at about 10 knots. The ship sustained minor damage to the hatch from main rotor blade impact.

The helicopter was fitted with a fixed utility float installation system on the landing gear. The floats had been fitted to the helicopter in July 2001 in accordance with the instructions contained in a CAR 35 engineering approval. The helicopter manufacturer was not able to provide engineering advice on the effect that the float installation would have had on the helicopter.

The primary damage to the helicopter was confined to the landing gear; in particular, the right front and right rear struts, and the main rotor assembly. A metallurgical examination of the landing gear components identified an existing fatigue crack, emanating from the drag brace attachment lower hole in the strut, as an initiation site for the failure of the right rear strut. The fatigue crack was due to the fitment of a non-standard drag brace bushing to the rear landing gear strut. The drag brace bushing also was not fitted using protective coating material and would not have been provided with corrosion protection from the marine environment. The right front strut failed in gross overload. A copy of the technical analysis investigation report, BE200400015, is at Appendix A.

Examination of the helicopter's maintenance documentation revealed the following:

• The helicopter had a valid maintenance release for the flight.
• The landing gear fairing fillets were removed and the landing gear was visually checked for cracks and damage during 100-hourly/annual inspections. The last 100-hourly inspection prior to the occurrence was conducted on 3 June 2004.
• Every 300 hours a landing gear inspection was carried out in accordance with the helicopter's maintenance manual. Those inspections required that the helicopter be jacked and the landing gear checked. Any elongated, enlarged or worn holes in the strut were to be repaired. The last 300-hourly inspection prior to the occurrence was conducted on 3 June 2004.
• There were no CASA or US Federal Aviation Administration Airworthiness Directives applicable to the 520N helicopter that would have required an inspection of the affected area to check for defects such as cracking of the strut.
• All required landing gear periodic and special inspections were carried out.
• Other than routine inspections, no maintenance action had been conducted in the region of the failure.
• No record could be found to indicate when the non-standard drag brace bushing had been fitted to the rear landing gear strut.