The pilot reported that when cruising at FL140 he noticed that the indicated airspeed was only 190 knots (normally 200 knots) and then noticed the nose down gear light was on. Attempts to rectify the problem were unsuccessful. The pilot contacted the company's chief engineer who advised him to return.

The nosewheel collapsed on landing at Kalgoorlie.

The investigation found that the aircraft had been used extensively on rough and soft strips. The nose gear actuator link had failed.

The pilot reported EICAS messages R Gen OFF, L Util Bus and R Util Bus.

Subsequently, acrid smoke entered the flight deck and cabin. Smoke removal procedures were effective.

The APU would not start at FL390, so the pilot informed ATC of the failed right generator and requested FL350 at 1633 WST. At 1638, the pilot advised ATC of smoke in the cabin, the second occurrence, and requested FL310 as the APU still would not start.

At 1649 the pilot advised ATC that the smoke had cleared and that operations were normal.

When power was reduced for the final descent, an EICAS message R Gen Drive came on. The right generator was then disconnected.

Following selection of flap 30 for landing, an unusual airframe judder was felt until touchdown.

The generator failure was traced to a lack of oil. No reason for the airframe judder could be determined.

ZK-NCJ, Auckland to Brisbane, at FL350 estimated position UDIKO at 0921 EST. ZK-NBI, Brisbane to Christchurch, was on climb to FL370 on reciprocal track (A464) estimating UDIKO at 0854. The Oceanic Controller calculated a time of passing at 0907 and on this basis required ZK-NBI to reach FL370 by 0855. The inbound aircraft revised the estimate for UDIKO, and the controller revised the time of passing to 0906.

The controller monitored the climb of ZK-NBI and became concerned that the requirement would not be met. He asked the crew to confirm that they would reach FL370 by 0855. The reply was that they would. At 0855 the aircraft was observed to be at FL355, and this was confirmed by the crew. Traffic information was then passed to both aircraft. ANZ76 reached FL370 at 0857.

FL330 was not available due to other crossing traffic.

The pilot-in-command of ZK-NBI later submitted a report which said that the aircraft's Flight Management Computer gave an indication that they would be able to reach the level by the required time. When they approached within a thousand feet of the level, the aircraft performance dropped off sharply. They then asked for FL350 which was not available.

The aircraft suffered an unexplained loss of performance which was not forecast by the Flight Management Computer. The reason for the loss of performance was not determined.

FACTUAL INFORMATION

Sequence of events

The B747 had departed Sydney and was maintaining flight level (FL) 310 on air route A576. The crew had reported passing the position reporting point MASDA at 1642 EST, with an estimate for reporting point KALUG of 1735.

The B737 had departed Alice Springs and was proceeding on A576 in the opposite direction. The crew had reported passing KALUG at 1616 with an estimate for MASDA of 1702. The aircraft was maintaining FL290.

When the B737 crew made their KALUG position report, the crew of the B747 was monitoring a different control frequency and was unaware of the presence of the B737. However, when the B747 crew made their MASDA position report, the crew of the B737 was on the same frequency, but did not hear the report and was unaware of the presence of the B747 on the reciprocal track.

At 1648, the crew of the B737 requested climb to FL330 and was instructed to "stand by" by Air Traffic Control sector 5 (Sec 5). Sec 5 then co-ordinated the request with the Sec 6 controller who concurred with the change of level for Sec 6 airspace. The Sec 5 controller proceeded to calculate a time of passing so that he could assess when a change of level for the B737 could be initiated.

The Sec 5 controller elected to use the ground speed method to calculate the time of passing. He asked each crew, in turn, to report the ground speed of their aircraft. It was at this time that both crews first became aware of the presence of the other aircraft, and that there was a possible confliction.

The controller made the initial calculation mentally and followed this with a written calculation on a note pad. As both calculations produced a result of 1724, he wrote this time of passing on the flight progress strip.

At 1652, Air Traffic Control approved the B737 to climb to FL330, with a requirement to reach FL330 by time 1714. The crew commenced the climb immediately.

The crew of the B747 received an information symbol indicating "Other Traffic" on their traffic alert and collision avoidance system (TCAS) when the B737 was approximately 40 NM ahead. The target information changed to a proximity alert followed by a traffic advisory warning. At this point, the crew decided that if the TCAS proceeded to a resolution advisory the pilot in command would manually fly the aircraft as directed by the advisory. The co-pilot would simultaneously make a radio broadcast indicating the action being taken.

At approximately 1653.20, the TCAS issued a resolution advisory advising "climb, climb". The pilot in command immediately commenced a climb in accordance with this advice. Aware that the other aircraft was also climbing, the pilot in command continued the climb at the best rate to approximately FL321, before returning the aircraft to the approved cruising level, FL310. The co-pilot made a radio broadcast indicating that they were carrying out a TCAS climb at the same time as the pilot in command initiated the climb manoeuvre.

Analysis of the B747's quick access recorder showed that the aircraft gained approximately 500 ft during the time that the resolution advisory was active and then gained a further 550 ft before descending.

The pilot in command of the B747 did not see the B737. However, immediately before the TCAS resolution advisory warning activated, the co-pilot sighted the B737 straight ahead and at a slightly lower level. He lost sight of it as his aircraft entered the climb. At that point, the B737 was passing directly below the B747.

The B737 was climbing at approximately 1,000 - 1,200 ft/min when the crew heard the TCAS climb radio call from the crew of the B747. They realised that their aircraft must have been the conflicting traffic and initiated an immediate descent. The crew looked up to see the underside of the B747 pass over and slightly to the right of their aircraft. The pilot in command levelled the B737 at FL305 and believed that his aircraft may have reached FL308 prior to the descent.

At 1653.30 (approximately ten seconds after the TCAS resolution advisory) the pilot in command of the B747 requested from air traffic control the position of the other aircraft. The Sec 5 controller responded by instructing the B737 to expedite climb to FL330. This instruction was carried out by the B737 crew.

The aircraft had passed with approximately 500 ft vertical separation and little or no horizontal separation. The required separation standard for two aircraft passing in the opposite direction on the same air route above FL 290 is a minimum of 2,000 ft vertical difference.

Air traffic control

During the investigation, several people involved in the training and performance appraisal of the sector 5 controller indicated their concern with certain aspects of his abilities. These concerns were notably in the area of procedural separation standards. Examination of check reports and interviews with supervisors, training staff, and workface controllers revealed that the official air traffic controller performance and check reports related only to some of the perceived deficiencies.

Many supervisors and training officers (including the former "Check" controllers) prepared formal reports for official filing but also retained other opinions in "private" files which were not readily available to management. However, the records that were available showed that his supervisors considered that the controller's performance was deficient in the area of procedural separation standards. When the controller was selected for training on another sector (Sector 6), the use of radar standards, which he had not used in previous ratings, was required. He subsequently failed this rating due to difficulty with procedural separation standards, rather than the radar standards. At the time of his final check for the Sector 6 rating the controller was experiencing personal problems which were not known to management.

There was no system in place to ensure that the responsible manager was specifically informed of a perceived weakness other than some review of the various reports prior to filing. This applied to ongoing performance appraisal as well as initial training and rating reports. As individual managers were often responsible for numerous controllers, the opportunity for them to adequately review all performance and check reports was not always available.

After the controller had failed to gain a rating on Sector 6, management elected to place him back on Sectors 1 and 5, those sectors on which he was rated prior to the Sector 6 training. The decision was made to retrain rather than refamiliarise the controller. Such a decision indicated a greater than normal concern for his ability to obtain the ratings which he had only recently held.

Having made this decision, management then elected not to provide the controller with simulator training to assist in this re-rating program, even though specific programs were available. The training officer was instructed to concentrate on separation standards during normal on-the-job training, especially time of passing and lateral separation problems.

Airborne collision-avoidance systems (ACAS)

ACAS are intended to improve air safety by acting as a last-resort method of preventing collisions or near collisions. The equipment utilises secondary surveillance radar technology to operate independently of ground-based aids and air traffic control. It monitors other aircraft in the vicinity and assesses the risk of collision by interrogating airborne transponders. Non-transponding aircraft cannot be detected. TCAS II, as fitted to the B747, is a version of ACAS which provides resolution advisories (for vertical manoeuvres only) as well as traffic information. The B737 was not equipped with any form of ACAS.

Time of passing calculation

Several attempts were made to replicate the calculation made by the controller for the time of passing. Neither the investigation team, air traffic services specialists, nor the controller concerned could determine how the time of 1724 was derived.

There was a 3 minute 20 second delay between the time the crew of the B737 requested the climb and the time the controller approved the climb. In this period the controller made two independent time of passing calculations, one mentally and one on a notepad. Whilst performing these tasks he was required to respond to nine separate air-ground and co-ordination communications involving 25 interchanges.

Two-way air routes

On 14 September 1995, a new upper air route network was introduced in the Australian Flight Information Region. The change resulted in numerous one-way air routes replacing many two-way routes and was intended, amongst other things, to reduce the potential for incidents such as this. The route being flown by the aircraft involved in this occurrence was not changed to a one-way route.

Flight crew response

TCAS resolution advisory

The pilot in command of the B747 was aware of the separation standard of 2,000 ft which was applicable at FL310. He chose to continue climb beyond that normally expected for a TCAS event, because of the known position and climbing attitude of the other aircraft. He wanted to ensure that his aircraft would outclimb the B737 and took into consideration the fact that any third aircraft in the area should be at least 2,000 ft above his aircraft.

ANALYSIS

This occurrence involved the provision of an airways clearance to permit an aircraft to climb through the level of another aircraft travelling in the opposite direction on the same air route.

Calculation of the closest point of approach indicates that, had the crews of both aircraft not responded following the TCAS activation, the aircraft would have passed with no horizontal separation and approximately 200 ft vertical separation.

Flight crew response - TCAS resolution advisory

The resolution advisory is an indication given by TCAS II to a flight crew that a vertical manoeuvre should or should not be performed to maintain safe separation from other aircraft. If required, such a manoeuvre should average between 300 ft and 400 ft. To prevent possible secondary separation problems, the manoeuvre should not normally exceed 700 ft. In this occurrence, the pilot in command decided to climb his aircraft in excess of this expected range because of the relative positions of the two aircraft.

The crew of the B737 did not see the B747 until after the TCAS broadcast by the crew of the B747, and the only visual acquisition was by the co-pilot of the B747 some seconds before the TCAS resolution advisory after he had received traffic advice from the TCAS. It is therefore reasonable to say that, had the B747 not been equipped with TCAS, neither crew would have seen the other aircraft in time to commence effective avoiding action.

Time of passing calculation

The separation standard based on the time of passing calculation was correct. It was the calculation itself that was in error.

The controller was confident that his calculations were correct because the time written on his notepad agreed with his mental assessment. However, he had been distracted by the amount of air-ground and co-ordination exchanges required in such a short period of time. This level of distraction would have resulted in a high mental workload and may have contributed to the erroneous time of passing calculation.

Management strategies

Having decided to re-rate the controller on Sectors 1 and 5 instead of refamiliarising his previous ratings, management indicated a greater than normal degree of concern for his performance. Information stored in "private files" would have given management a better insight into these perceived procedural deficiencies.

A re-rating program was devised to assist the controller, but this plan did not require simulator training for procedural separation standards. Such training may have provided a more comprehensive preparation for his rerating. Although adequate simulator exercises were available, finding appropriate training staff for the simulator proved difficult.

SIGNIFICANT FACTORS

1. The aircraft were travelling on a two-way air route in opposite directions.
2. Management strategies for the early detection and remedy of perceived deficiencies in controllers' competencies were ineffective.
3. The controller miscalculated the time of passing of the aircraft.
4. The TCAS on the B747 provided the only catalyst for avoiding action by the aircrew.

SAFETY ACTION

During the course of the investigation the Bureau of Air Safety Investigation issued the following interim recommendation to the then Civil Aviation Authority on 6 June 1995:

"IR 950117

"The Bureau of Air Safety Investigation recommends that the Civil Aviation Authority:

"(i)   mandate the fitment and use of an Airborne Collision Avoidance System (ACAS) in all aircraft engaged in Regular Public Transport (RPT) operations;

"(ii) consider the requirement for the fitment and use of a suitable ACAS in other aircraft engaged in the carriage of passengers for hire or reward;

"(iii) mandate the activation of any SSR transponder in aircraft so equipped at all times when airborne, irrespective of the class of airspace in which the aircraft may be flying;

"(iv) mandate the standard of ACAS equipment to be carried in each aircraft classification;

"(v)   set a timetable for the introduction of ACAS equipment; and

"(vi) ensure that air traffic services officers are given adequate and timely education and continuation training in the capabilities and operational impact of ACAS equipment."

The following response was received from the Civil Aviation Safety Authority on 21 August 1995:

"I refer to Air Safety Interim Recommendation IR950117 regarding Airborne Collision Avoidance Systems (ACAS).

"In response to the reported air miss occurrences referred to as justification, in part, for this recommendation, the Civil Aviation Safety Authority has commenced an examination and analysis of both BASI and AA incident data in order to identify and better understand the nature of these deficiencies within the Australian aviation system. Significant differences between BASI and AA data, in both number and classification of reported incidents, has complicated and restricted this process to date.

"Apart from analysis of risks in a non ACAS environment, CASA also recognises the need to assess the impact of ACAS on future major projects such as TAAATS and implementation of AACS. The Authority also intends to review any potential disbenefits that may arise from ACAS, including spurious activations and effects of resolution advisories (RAs) in complex air traffic situations.

"Industry and Public consultation will precede any adoption of requirements for aircraft to carry ACAS. The Authority continues to monitor world trends and is currently reviewing recent UK safety studies on ACAS." The Bureau has classified the response as OPEN and has initiated further correspondence on the matter.

Additionally, Interim Recommendation IR950218 was issued to the Civil Aviation Safety Authority and Interim Recommendation IR950219 was issued to Airservices Australia, after the 1995 reorganisation. These were issued on 11 January 1996:

"IR950218

"That the Civil Aviation Safety Authority in conjunction with other operators of TCAS-equipped aircraft, evaluate the initial and recurrent training requirements for aircrew of TCAS-equipped aircraft.

"The evaluation should ensure that the risks associated with excessive vertical deviations in response to TCAS RAs are identified."

The Civil Aviation Safety Authority responded on the 12 February 1996 as follows:

"I refer to your interim recommendation number IR950218 regarding the incident involving Boeing 747, G-BNLR and Boeing 737-476, VH-TJK, on 4 May 1995.

"Summary

"The authority accepts the Interim Recommendation.

"Background to response

"Details of the exact nature and extent of training currently undertaken by TCAS equipped operators will be determined to establish whether or not such training adequately addresses the risks associated with excessive and inappropriate pilot responses to RAs."

The Bureau has classified this response as CLOSED/ACCEPTED.

"IR 950219

"That Airservices Australia evaluate the TCAS initial and recurrent training requirements for ATS personnel. This evaluation should ensure:

"(i) thorough and consistent practical knowledge is achieved throughout ATS; and

"(ii) TCAS RA encounters are practised in simulator sessions."

Airservices Australia responded on the 22 February 1996 as follows:

"I am writing in response to your Interim Recommendation IR950219 which recommends that Airservices Australia:

"evaluate the TCAS initial and recurrent training requirements for ATS personnel.

"Preliminary evaluation of the level and extent of TCAS training provided to Air Traffic Services personnel indicates that training on TCAS was generally consistent across Air Traffic Services centres.

"The training provided consisted of local team development supported by a video presentation with accompanying booklet detailing TCAS procedures.

"The ATS Operational Training Unit is currently developing a comprehensive package for the purpose of evaluating TCAS training and awareness. The purpose of this evaluation is to assess both the level of initial training and the current appreciation of TCAS.

"Future TCAS training will be dependent upon the results of this evaluation. The focus of any proposal will be on improving and enhancing training delivery to ensure that both initial and recurrent training needs are clearly identified and addressed.

"A variety of instructional methodologies and strategies will be considered during the evaluation process. Any proposal for simulation of TCAS RA encounters will also be dependent on the results of the evaluation and the feasibility of successfully simulating such encounters."

The Bureau classified this response as CLOSED/ACCEPTED.

Note: In December 1996 CASA issued a Legislative Instrument Proposal which proposed the mandatory carriage of TCAS equipment in some classes of aircraft and addressed further the recommendations IR950218 and IR950219.

Final recommendations

The Bureau of Air Safety Investigation made the following recommendations on 1 November 1996:

"R950227

"That Airservices Australia further review the upper air route structure to create, wherever practicable, one-way air routes within the Australian Flight Information Region."

"R950228

"That Airservices Australia review the training given to ATC and Flight Service staff in coping with distractions in the workplace and consider improvements in the techniques to reduce the impact of distractions on staff performance."

"R950229

"That Airservices Australia:

"(i) develop strategies that encourage all officers who carry out performance appraisals to notate all concerns in an adequate and timely manner on the approved proforma;

"(ii) develop strategies for improved management oversight of appraisal reports, especially in the area of "below expected performance" assessments; and

"(iii) ensure that specific training programs, including simulator and desk-top exercises, are developed to address perceived deficiencies in each of the skill and knowledge items contained in any appraisal report."

The pilot said that he had been working for the operator for one week prior to the accident. He was employed on a casual basis, based in Cootamundra.

After conducting his normal freight flight to Hay, he arrived back at Cootamundra at about 1845, whereupon he unloaded the freight he had been carrying, and went to his car to collect personal belongings for a ferry flight to Bankstown. At the same time, the aircraft was being refuelled. A total of 313 litres of fuel was added to the aircraft, filling all tanks with the exception of the right auxiliary, which was filled to 20 litres less than capacity. By the time the pilot had returned to the aircraft the refueller had left. He said he carried out a fuel drain but then became distracted by the imminent arrival of another aircraft. He subsequently believes he did not check the status of the fuel caps.

The aircraft departed Cootamundra at about 1912 for an IFR flight to Bankstown. The planned cruising level was 5000 feet in order to minimise delays with entry to controlled airspace. Main tanks were selected for take-off and initial climb. Shortly after take-off, the left and right auxiliary tanks were selected to feed their respective engines. During the cruise the pilot said that he noticed, after some time, that the fuel contents indicators appeared to be giving erratic readings. He was not concerned at this because he was confident the aircraft was carrying a very large margin over the fuel required for the flight.

As the aircraft passed Bindook VOR the pilot said he changed back to both main tanks. Shortly after this the left engine stopped. He commenced to go through the appropriate checklist items when the right engine also stopped. He immediately changed back to the auxiliary tanks without effect, then tried a number of tank/crossfeed selections, combined with various fuel pump and mixture settings. A momentary surge of power from one engine was all that could be achieved. The pilot gave a Mayday call, extended half flap and reduced speed to 75-80 knots. Nothing could be seen outside the aircraft due to darkness, low cloud and rain.

The aircraft collided with trees in rugged terrain and came to rest, relatively intact. The pilot said he struck his head on the instrument panel, sustaining a small cut on the forehead. At the time of impact, he did not have his shoulder harness secured, being only restrained by his lap belt. He had unbuckled the shoulder straps during cruise because they were chafing his neck. After the loss of engine power, he did not have sufficient time to refasten the harness.

Immediately after the aircraft came to rest, he kicked open the main door and rapidly evacuated the aircraft, as he was concerned that the aircraft may have caught fire. There was no fire and so he was able to re-enter the aircraft after a short time and use the aircraft radio to notify his position, and to communicate with rescuers. Although located that evening by rescue helicopter, due to poor weather conditions, and hazardous terrain, he was not extracted from the crash site until the following morning.

Inspection of the wreckage revealed that all four fuel tank caps were unlatched, allowing fuel to be vented overboard during flight. It was subsequently reported that the refueller had been specifically instructed by a previous company pilot not to latch the fuel caps after refuelling. This procedure required the fuel contents to be checked, then the fuel caps to be fastened, by the pilot-in-command. The new pilot of VH-USP was aware of this procedure, however, when he failed to check the fuel caps there was no fail-safe capability to prevent a consequent loss of fuel during flight.

SEQUENCE OF EVENTS

When the crew of the aircraft listened to the Automatic Terminal Information Service (ATIS) before commencing their descent, there was no advice that an instrument approach could be necessary. After initial contact with Maroochydore Tower, the crew were cleared to descend to 3,000 ft. The controller co-ordinated another IFR aircraft and one VFR aircraft to give the regular public transport jet priority. However, the Aerodrome Controller did not advise the crew to expect an instrument approach but gave them the option of a DME Arrival or an 18 VOR/DME approach via the 10 DME arc. As the aircraft was still at 4,000 ft and close to the aerodrome, the crew accepted the only viable option of an 18 VOR/DME approach.

The aircraft did not become visual at the minimum descent altitude and the crew elected to divert to Brisbane where a 19 ILS approach was flown to a safe landing.

The captain later complained of the lack of operational information, "indecision" by the ADC, and no advice of an amended terminal area forecast (TAF), special forecast (SPECI) or advice from Brisbane Approach that an instrument approach would be required.

ANALYSIS

The captain's complaint about the lack of operational information regarding an "expect instrument approach" message is valid. He misunderstood the ADC's offer of a choice of instrument approaches as indecision.

The Bureau of Meteorology reviewed the forecasting aspects and conceded that the Maroochydore TAF should have continued with INTER which would have alerted the pilot to expect weather difficulties and to plan for it by carrying extra fuel.

The crew cramped their approach by descending to only 4,000 ft when they had been cleared to descend to 3,000 ft. They apparently did not remember the clearance even though the automatic voice recording tape revealed that they had acknowledged the 3,000 ft clearance.

SAFETY ACTION

Airservices Australia's Maroochydore procedures were modified on 17 May 1995 to include an "expect instrument approach" message in the ATIS when appropriate.

VH-LAP was cleared to track to Tea Tree (TTR) at 7000 feet.  Approaching TTR, the aircraft was instructed to enter the holding pattern and shortly afterwards was cleared to descend to 4000 feet and to make an ILS approach for runway 12.  Three minutes later, at 1812 hours, the pilot reported an ADF failure and asked for a climb. He was cleared to 5500 feet. He was then cleared to track outbound between the 301 and the 310 radials, and to turn inbound as required to establish the aircraft on the localiser at approximately 20 DME.  He could then expect an ILS approach.

Over an extended period, the pilot tried to establish himself on the localiser, with assistance from the pilots of two other aircraft holding above, both of whom had VH-LAP in sight from time to time.  Eventually another ILS was commenced but this was abandoned because the aircraft was too high (4500 feet at five miles from the aerodrome on final approach).

At the suggestion of the tower controller and with controller assistance a runway 30 VOR/DME was then successfully completed and the aircraft landed at 1859.

The pilot was using a GPS to establish distances, as he could not obtain distance readings from the international DME.  Use of the GPS as a primary navigation aid was not permitted. The pilot had selected the Hobart ILS frequency on both the NAV selector and the international DME selector. The pilot thought the international DME selector was a second NAV selector.  The number two NAV indicator, which the pilot thought was for a second NAV receiver, was in fact driven by the GPS.  Hence the tracking indications on the two NAV indicators were different. Because of the pilot's misunderstanding over the purpose of the second indicator, the indication differences created confusion in his mind.

The ADF equipment was later established to have been operating normally and the reason for the pilot reporting it had failed was not determined.

Another company pilot was holding at TTR and attempted to pass advice to the pilot of VH-LAP.  Recorded communications of the occurrence showed that the stream of instructions was considerable and may have contributed to overloading the pilot of VH-LAP.

Significant Factors

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

1. The pilot was not adequately familiar with the navigation equipment fitted to the aircraft and hence became confused over the indications obtained.
2. The pilot had a low skill level in regard to orientating the aircraft to proceed on the localiser track.

When the pilot selected the landing gear down, only the nosewheel locked down. He then followed the landing gear emergency extension procedure. This resulted in the left main gear being locked down but the right gear remaining unlocked. After discussing the problem with his company, the pilot landed the aircraft with the nose gear locked and both main gear unlocked. During the landing, the fuselage underside was scraped and the left tailplane bent. An inspection revealed that a seal in the right main gear actuator had failed.

Factual information

The F-27 aircraft had been carrying out circuit training and had landed on runway 05. The crew accepted the Aerodrome Controller's (ADC) offer to backtrack on runway 05 for further circuits and they reported ready for takeoff at 1002.32 CST. The TB-10 aircraft was making an approach to runway 12 for a touch-and-go landing. At 1003.05, the ADC cleared the aircraft for the touch-and-go and also passed departure instructions to that aircraft. Co-ordination between the ADC and Approach controller resulted in an agreement to sequence the F-27 so that it would land behind four jet aircraft arriving for runway 05. The ADC informed the F-27 crew of the sequencing difficulty and, at 1003.15, said there would be about a 30-second delay before he could issue a take-off clearance. At 1003.45 the pilot of the B737 contacted the ADC whilst on approach for runway 05. At 1004.58, the ADC cleared the F-27 for takeoff.

The crew elected to hold position as they had seen the TB-10 on its approach to land but had not seen it depart after the touch-and-go. From the position of the F-27 part of runway 12 was hidden from view behind buildings. Consequently, the F-27 was held by the crew with power on and ready to commence the takeoff once the TB-10 was clear of the intersection. The B737 crew saw the F-27 lined up on runway 05 and slowed their aircraft lowering, 40 degrees of flap to assist in the sequencing process. At 1005.04 the ADC informed the B737 crew to expect a late landing clearance. At 1005.12 the F-27 commenced its take-off run approximately two minutes after receiving the advice of the expected delay of 30 seconds. The TB-10 was airborne but still not clear of the runway intersection and at this time, the B737 was on short final. At 1005.30, as the F-27 was becoming airborne the ADC cleared the B737 to land. At the same time the B737 crew informed the ADC that they were commencing a go-around which they had started just prior to receiving landing clearance. The go-around decision was based on doubts that sufficient separation existed between the B737 and F-27, especially if the F-27 was to reject its takeoff. The B737's go-around was flatter than the normal climb profile so that the captain could maintain visual contact with the F-27 and to ensure a safe manoeuvring speed. At 1005.50, the ADC instructed the F-27 crew to maintain 500 ft and to turn left onto a heading of 300 degrees. As the F-27 was commencing its left turn, the B737 was turned right about 20 degrees to ensure continued sighting of the F-27.

Analysis

Aerodrome Controller

The ADC elected to process the F-27 by backtracking it on runway 05. The sequence chosen by the ADC was time-critical as it depended on the TB-10 crossing the intersection before the F-27 could take off, and the B737 was dependent on both these aircraft departing before it could land.

The controller realised that the sequence would be tight but he did not consider an alternative plan even though several options were available. Although after line up the F-27 crew were told to expect about a 30-second delay the actual delay was one minute and 43 seconds. When the crew of the F-27 were issued with their take-off clearance the TB-10 was still not clear of the runway intersection which led to a considerable erosion of the time base on which the ADC had based his original plan. Radar analysis indicates that the take-off clearance was issued to the F-27 approximately 20 seconds before the TB-10 had cleared the runway intersection. Paragraph 23 of the Manual of Air Traffic Services (MATS) 6-3-4 specifies the separation standard applicable to a situation in which two aircraft are departing from different runways stating that aircraft B [F-27] shall not be permitted to commence takeoff until aircraft A [TB-10] has crossed the intersection. Paragraph 26 of MATS 6-2-3 allows the controller to issue a take-off clearance prior to the prescribed separation existing if in the opinion of the controller no collision risk exists, and there is reasonable assurance that separation will exist when the aircraft commences its take-off roll. In this case, as the F-27 crew were expecting an immediate departure on receipt of take-off clearance, the ADC could not have reasonably expected the aircraft to delay its take-off roll. The investigation found that no uniformly accepted interpretation of the meaning of paragraph 26 existed between ATS management and some operational staff.

The B737 crew were told to expect a late landing clearance and the ADC issued this clearance between 1005.31 and 1005.33. Radar analysis indicates that the B737 was either just short of, or passing the runway threshold when the landing clearance was given. The F-27 became airborne at 1005.35. Paragraph 32 of MATS 6-3-5 states that aircraft B [B737] shall not be permitted to cross the runway threshold until aircraft A [F-27] (less than 136,000 kg MTOW) is airborne after takeoff. If the B737 was short of the runway threshold at 1005.35, then the clearance complied with the MATS instruction. If however, the B737 was passed the runway threshold at that time, the runway separation standard would have been breached. The ADC believed that had the B737 landed, the separation standard would have been achieved and that the F-27 would be airborne prior to the B737 crossing the threshold. Radar analysis could not determine if the separation standard had been achieved. The standard requires that an aircraft below 136,000 kg MTOW should be airborne before a landing aircraft of any size crosses the runway threshold. Therefore, as an example, an aircraft could be airborne at 70 kts and 500 ft along the runway when a landing jet aircraft crosses the threshold at up to 150 kts. The separation standard would then be breached if an unexpected event forced the departing aircraft to discontinue takeoff and reoccupy the runway. An ADC is required to take into account any unexpected manoeuvres by aircraft when issuing a clearance. In this occurrence, there was a 2-4 second period in which the standard may have been achieved. The B737 crew doubted that the standard would be achieved. Once the B737 had commenced its go-around, the ADC expected the climb to be similar to a normal B737 departure and believed this would solve any separation problems that may arise.

However, the climb profile was more shallow than expected, and the ADC considered further action was required to guarantee separation. Instructions were issued to both crews to ensure that vertical and lateral separation were maintained. Crew of the F-27 After lining up and holding on runway 05, the F-27 crew were given traffic information on the TB-10 which was on final approach for a touch-and-go on runway 12. They sighted the aircraft and monitored its descent and touchdown. The ADC had asked the F-27 crew to be ready for an immediate departure as soon as the TB-10 was airborne. When the take-off clearance was issued, they increased power but held position until they had sighted the TB-10 and this delayed the commencement of their takeoff for approximately 12 seconds. Crew of the B737 When on final approach for runway 05, the B737 crew became aware of the F-27 occupying the runway and aircraft speed was reduced as much as possible. On short final, the ADC issued a late landing clearance expectation and the crew briefed for a possible go-around. The B737 captain was concerned that if the F-27 rejected its takeoff or had a malfunction shortly after lift-off and landed again, there would be insufficient room for the B737 to land safely. As the B737 approached the threshold, the crew could see that the F-27 was still not airborne and well within the distance they would need to land and they initiated a go-around about the same time as they received a landing clearance. To regain safe climb speed and maintain visual contact with the F-27, the captain elected to climb at a sufficiently nose-down attitude until his aircraft was safely clear. The captain considered that the F-27 was sufficiently close to his aircraft that a risk of collision existed if he lost sight of that aircraft.

Findings

1. The ADC misjudged the time required for the TB-10 to clear the runway intersection.

2. The ADC issued a take-off clearance to the F-27 when the required runway separation standards were not met. (MATS provides the ADC with this discretion.)

3. The discretion shown by the ADC in finding 2 above, was inappropriate.

4. The F-27 crew could not see the TB-10 during the ground roll portion of its touch-and-go landing on runway 12.

5. The F-27 crew had good reason not to commence takeoff at the time the ADC issued the clearance.

6. The ADC cleared the B737 to land in the belief that the appropriate runway separation standard would be achieved.

7. The B737 crew executed a go-around manoeuvre when they judged that the runway may not be available for the safe operation of their aircraft.

8. At the time of the B737 go-around, it was unclear (to the investigation team) if the runway separation standard would have been maintained.

9. The B737 climbed at a more shallow angle than that expected by the ADC.

SIGNIFICANT FACTORS

1. The ADC placed undue pressure on himself by initiating a backtrack by the F-27.

2. The decision by the ADC to delay the F-27 until the TB-10 had completed its touch-and-go placed the three aircraft in a position whereby they each required the use of the runway intersection within a very short period of time.

3. The runway separation standard applicable in this case is such that it allowed the ADC to issue clearances whereby the B737 crew were unable to guarantee the safe landing of their aircraft.

4. The ADC did not have a fall-back plan for the sequence he initiated.

SAFETY ACTION

As a result of the investigation the following local action was taken. Air Traffic Services management clarified the interpretation of MATS 6-2-3 para. 26 to the satisfaction of the investigation team and ensured that all Adelaide Tower staff were in no doubt as to their responsibilities in this regard. Additionally, the Bureau of Air Safety Investigation issued the following interim recommendation to Airservices Australia on 29 May 1996.

IR960046 The Bureau of Air Safety Investigation recommends that Airservices Australia, in conjunction with the Civil Aviation Safety Authority, reviews the runway separation standards for landing aircraft in relation to departing aircraft. This review should consider what separation standards may be required to cover contingencies where slower departing aircraft may impede the safe passage of faster landing aircraft. Airservices Australia responded on 29 July 1996. IR 960046 Airservices, in conjunction with CASA, is currently reviewing runway separation standards for landing aircraft in relation to departing aircraft. This review includes an examination of the ICAO standards in relation to departing aircraft, as well as current international practices. The review will also attempt to assess the impact and safety benefit of the introduction of more restrictive practices on runway capacity at specific locations.

It is intended that the review be completed by the end of August.

Response Status: Closed - Accepted.

The Civil Aviation Safety Authority responded on 17 June 1996. In accordance with IR 960046 the separation standards in relation to a faster landing aircraft behind a slower departing aircraft will be reviewed. (Note: the Report states that there is a 2 - 4 second period where the standard may or may not have been achieved: were the tolerances of the radar taken into account in making that assessment?)

Response Status: Closed - Accepted BASI Note: The radar tolerances were taken into account in the investigation.

The pilot reported that on arrival in the circuit area he observed that the employee responsible for inspecting the strip was in attendance, and there were no indications that the strip was unserviceable. After a normal approach and landing with 40 degrees of flap set, the nose was being held off when a bump was felt causing the pilot to believe that a failure had occurred with the nose gear. The pilot continued to hold the nose off until elevator control was lost. The nose then settled, and the propeller struck the runway. The nose gear had failed after striking a hole made by wild pigs, and the hole been obscured by weed growth. A further three holes that were not readily visible were found, but they were not in the landing path.