Shortly after take-off, at a height of about 250 feet above the ground, the engine lost power. The pilot applied carburettor heat which he said resulted in a brief surge of power after which all power was lost. The pilot dumped the load but while he was manoeuvring to avoid a fence the aircraft stalled and hit the ground heavily.

Subsequent investigation revealed that the engine fuel system was contaminated with water. The pilot had refuelled the aircraft from a 200-litre drum prior to take-off. Although he checked the drum for water contamination prior to refuelling and then completed a fuel drain check of the aircraft fuel tanks, he did not detect water.

Further investigation revealed that the 200-litre drum from which he refuelled had been sitting in a utility in heavy rain for a number of days and the drum bung had a faulty seal. The pilot believed there was no doubt that he had pumped water contaminated fuel into the aircraft fuel tanks which then found its way into the engine.

Factors

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

• The pilot did not detect water in the fuel when he checked the drum source prior to refuelling the aircraft tanks.
• The pilot did not detect water in the fuel when he did his fuel drain check of the aircraft tanks after the refuelling.
• The aircraft engine lost power when it ingested water contaminated fuel.
• After the engine failure, the pilot stalled the aircraft at a low height while manoeuvring to avoid a fence.

When VH-CZM was transferred to the arrivals controller, the aircraft was observed to turn left at Wonthaggi and track 298 degrees towards BAYSI instead of 320 degrees towards Plenty. The controller subsequently radar vectored VH-CZM to Plenty. There was no breakdown in separation.

By replaying the communications tape, it was discovered that at 14.04.35 EST, the sector three controller had issued the following clearance: "Charlie Zulu Mike, STAR clearance Plenty One arrival, runway 34, maintain flight level 370."

The pilot read back: "Charlie Zulu Mike BAYSI One arrival, runway 34, flight level 370."

When the pilot read back a different clearance, the controller failed to notice the pilot's error. When the aircraft turned left, the pilot genuinely thought that he had been cleared for a BAYSI one arrival.

Significant Factors

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

1. The pilot misheard the Plenty One clearance and read back BAYSI One.

2. The controller misheard the pilot's incorrect clearance read back.

The pilot reported that he had made an approach to land on runway 32. During the landing roll the pilot became concerned that the aircraft would not stop before the end of the runway, and he decided to go around for another circuit. The pilot applied power and attempted to fly the aircraft off the ground at the end of the runway. The aircraft did not climb, and the right wing collided with a three metre high tree causing the aircraft to slew around and touch down again. The right wing, engine cowl and nosewheel were also damaged as the aircraft came to a stop, still on its landing gear and pointing in the opposite direction to the landing, approximately 70 m from the end of the strip.

It is probable that the pilot flew the aircraft off the ground at too low an airspeed and the combination of the low airspeed and its associated drag prevented the aircraft from climbing clear of the obstacles.

Soon after take-off the aircraft was observed to drift to the right of the runway centreline and disappear into cloud. Subsequently the pilot broadcast a PAN call advising that the right engine had failed. The aircraft was vectored for a return to the airfield where a single engine landing was accomplished.

Maintenance checks disclosed that the engine was slow to accelerate and, that at 90% N2, the compressor stalled. A fuel control unit change and rigging check did not clear the problem; therefore, the engine was changed.

The engine has been placed into long term storage consequently the cause of the problem has yet to be established. A major defect report has been submitted to the Civil Aviation Safety Authority.

The pilot reported that he was having difficulty lowering the landing gear. He later advised that he was unable to lower the gear and that he intended conducting a wheels-up landing.

Later engineering examination found that the push pull cable, between the gear selector handle and the power pack, had broken. CASA Airworthiness at Coffs Harbour were advised the details of the occurrence and were able to recover the broken cable for further specialist examination.

FACTUAL INFORMATION

History of the flight

The aircraft had departed Bankstown for a dual instrument flight rules (IFR) training flight, including aerial work at Goulburn followed by two practice instrument landing system (ILS) approaches at Canberra, before returning to Bankstown.

After completion of the second ILS approach, the pilot was instructed to carry out a missed approach and climb to 7,000 ft.

As the aircraft was levelling in instrument meteorological conditions (IMC), the instructor noticed that engine Manifold Absolute Pressure (MAP) had reduced from 30 inches to 25 inches. He asked the pilot if he had adjusted the power and the pilot replied in the negative. At 1127 EST, the instructor advised Canberra Approach (APP) that the aircraft had experienced a loss of power. He reported that the aircraft was able to maintain 7,000 ft and confirmed that he wished to return to Canberra for landing. Air Traffic Control then instructed the pilot to turn the aircraft onto a southerly heading.

Between 10 and 15 seconds later, the aircraft occupants heard a loud thump that shook the aircraft, and the engine RPM reduced significantly. At 1128 the pilot advised APP that the engine had failed and requested that APP provide headings to the vicinity of Lake George. APP identified the aircraft on radar at a position 17 NM to the north-east of Canberra over the western shores of Lake George. APP then passed information to the pilot about an airfield near Bungendore as a possible landing area.

At 1129, the pilot advised that assistance was still required and confirmed that the aircraft was still in IMC. APP advised the pilot to disregard the previous vectoring instructions, indicated that a landing on the Federal Highway might be possible and instructed the pilot to turn onto a heading of 020 degrees. At 1131, the pilot advised that the aircraft was descending through 4,200 ft.

At 1132, APP requested that the pilot activate his emergency locator transmitter (ELT). The pilot then advised that the aircraft was still in IMC and passing 3,500 ft. APP advised that the aircraft was passing over the northern shores of Lake George and requested the pilot to turn the aircraft right to an easterly heading to avoid high terrain in the area. No reply was received.

Another aircraft, VH-DUP, was in the Goulburn area at this time and the pilot offered to relay a message to VH-SMA. APP requested the pilot of VH-DUP to listen out on 121.5 MHz to determine if an ELT had been activated. The pilot of VH-DUP advised that he was unable to make contact with VH-SMA and confirmed an ELT signal on 121.5 MHz.

The time of the accident was 1133. A rear-seat occupant, who was also a qualified pilot, later stated that he estimated that the aircraft broke through the cloud base below 300 ft above ground level (AGL).

An army helicopter was dispatched from Canberra at approximately 1155 and proceeded to the area of the last known position of VH-SMA. A second helicopter carrying a medical team was dispatched to the area at 1230.

At 1240, one survivor from the aircraft was located by a search helicopter. Two other survivors were located soon after. All three had suffered severe burns.

Wreckage examination

Wreckage was distributed along a 49 m trail aligned approximately east. The aircraft had entered the timbered area on this track and had partially broken up as it descended through the trees. As the aircraft penetrated the timber, it struck and severed tree branches and trunks over 150 mm in diameter, starting 49.3 m and ending 28.5 m from the main wreckage, before coming to rest on a south-westerly heading against the trunk of a large tree approximately 1 m in diameter.

The main wreckage consisted of the fuselage, the fin, the right horizontal tailplane and most of both wings. The left horizontal tailplane had been torn off during the impact sequence. The empennage showed evidence of oil streaking, indicative of engine oil loss in flight. The fuselage had been almost completely destroyed by post-impact fire. The engine and propeller remained attached to the fuselage. Inspection of the propeller indicated that the engine was not producing power at impact.

The engine was basically intact and unaffected by fire. Both magnetos had separated from the engine. There were two holes in the top of the crankcase aligned with cylinders number 2 and 3. When the engine was turned over for examination, approximately 1 L of oil flowed out of the holes in the crankcase.

Pilot information

The aircraft owner occupied the left control seat. He held a valid private pilot (aeroplane) licence, issued on 1 July 1976, with PERPETUAL status. He had about 1,000 hours total experience, of which almost 600 hours were in VH-SMA. He had held a command instrument rating (single engine), issued 7 December 1987 and expired 31 January 1994, and was practising for renewal of the rating. His medical category was valid to 18 June 1996.

The right control seat was occupied by an instructor who held an air transport pilot licence, issued 1 September 1992 and with PERPETUAL status. He held a Command Instrument Rating issued 28 March 1983 and valid to 30 September 1995. He had almost 14,000 hours total experience of which approximately 3,000 hours were on Cessna 210 aircraft and more than 2,000 hours were in VH-SMA. He had held chief flying instructor and chief pilot approvals since 24 April 1990. His medical category was valid to 12 October 1995.

Weather

An intense low-pressure system was centred at 45 degrees south, 133 degrees east. This system was coupled with a low-pressure system in the Tasman Sea and a series of cold fronts were embedded in the strong south-westerly airstream associated with these systems.

The Bureau of Meteorology estimated conditions in the Lake George area as:

Wind 330/08

Visibility Less than 1,000 m

Weather Drizzle and rain throughout the area

Cloud Broken stratus, base ground level

Overcast nimbostratus, base 1,000 ft AGL

Freezing level 6,000 ft

Icing Moderate in cloud above freezing level

Surface temperature 8 degrees C

Dew point 8 degrees C

QNH 992 hPa

Upper winds 3,000 ft 310/15

5,000 ft 310/25

7,000 ft 310/30

10,000 ft 270/35

Detailed engine inspection

The engine was removed from the wreckage for detailed inspection. The engine was completely disassembled by Bureau engineers in the presence of representatives from the engine manufacturer and the Civil Aviation Safety Authority. The most significant findings were:

(a) less than 1 L of oil remained in the engine;

(b) numbers 2 and 3 connecting rods had failed;

(c) numbers 2 and 3 big end shell bearings plus their associated column supports, were severely damaged;

(d) there was significant fretting on the number 2 main bearing column support mating surface to a depth of at least 0.002 inches;

(e) minor fretting damage was present on the other column supports;

(f) one connecting rod big end bearing housing bolt had failed earlier than the rest;

(g) the torques on some cylinder retaining nuts were well below the expected values;

(h) a number of the through bolts showed evidence of fretting at the crankcase split line location;

(i) the turbocharger oil reservoir return line was broken;

(j) there appeared to be no blockage of the main oil galleries;

(k) the oil pump appeared to be working at the time of impact;

(l) the turbocharger had received no discernible damage; and

(m) there was no evidence of the typical sludging of the engine following the use of Mobil AV-1 synthetic oil.

The damage to the engine was consistent with oil starvation. The damaged turbocharger oil reservoir was considered as a possible source of oil loss and was examined in a metallurgical laboratory. The examination revealed that, in the past, the welded joint between the outlet fitting and the top cover had cracked and had been repaired by welding. Inside the lower cap were marks matching the position and shape of the outlet pipe; these marks were consistent with the outlet pipe being jammed downwards and rearwards during the impact sequence.

Maintenance history and documentation

The engine logbook showed that in August 1987, the engine had undergone a bulk strip to inspect the crankshaft and crankcase for cracks following a propeller strike. The inspection found the components to be satisfactory and the engine was returned to service. The logbook indicated that this was the last occasion on which the crankcase had been split.

The aircraft was operating with a valid maintenance release (Maintenance Release 209476, dated 4 August 1994). No daily inspections had been written up since 23 April 1995. At the last major servicing the aircraft had flown 2,400 hours and had flown a further 93.3 hours to the last entry on the maintenance release.

Air traffic control

The Canberra Approach controller later stated that the aircraft was to the west of Lake George when the pilot reported the initial engine problem. As the pilot initially stated that he could maintain altitude, the controller vectored the aircraft onto a southerly heading for a return to Canberra.

By the time that the pilot reported the engine failure, a second controller, who was very familiar with the Canberra area, was standing by. The second controller suggested the possibility of a landing on the Federal Highway to the north-east of Lake George. The approach controller then vectored the aircraft onto a northerly heading, but soon concluded that the aircraft would not reach the highway and that it was approaching an area of high terrain. He then turned the aircraft onto an easterly heading to have it fly parallel to the foreshore, where the terrain was lower and, he believed, the weather clearer.

The controller stated that he believed that there was high terrain in the vicinity of the proposed landing site near Bungendore and decided to discontinue his initial plan to vector the aircraft to that area.

ANALYSIS

The accident was the result of an engine failure in weather conditions that precluded a visual forced landing. The cloud break below an estimated 300 ft AGL, in poor visibility and over timbered terrain, denied the pilot any effective choice of landing sites.

Detailed examination of the engine established that it failed due to a loss of effective lubrication. The Bureau's technical investigators reviewed the findings from the engine examination with specialists from the engine manufacturer and the Civil Aviation Safety Authority. The condition of, and damage to the engine and other powerplant components pointed to some possible sources of loss of effective lubrication:

(a) failure of the return line to the turbocharger reservoir, causing oil loss and subsequent oil starvation to the engine;

(b) fretting of the crankcase mating surfaces and through-bolts, indicating lack of sufficient pre-load on the crankshaft bearings, and consequently allowing the bearing(s) to rotate, blocking the supply of oil to key areas in the engine; or

(c) a combination of the above.

The exact cause of the loss of effective lubrication could not be established.

Air traffic control

Had the engine failure occurred in visual meteorological conditions (VMC), the pilot would have had more options available for him to have carried out a safe forced landing in the Lake George area. However, the engine failure in IMC meant that the crew was totally dependent upon the Canberra Approach radar controller for positioning. The cloud was estimated to include broken stratus to ground level with an overcast of nimbostratus from 1,000 ft AGL, with drizzle and rain throughout the area. The controller would therefore have been required to vector the aircraft almost to touchdown to be of practical assistance in the final stages of flight.

Although he received advice from another controller who was familiar with the Canberra area, the approach controller was not so familiar. The limitations of the radar display, which depicted Lake George only in general terms (vector lines), prevented the controller from being certain of the aircraft's position with respect to terrain features. As the aircraft descended in IMC, the controller's range of options diminished rapidly and he finally concentrated upon positioning the aircraft as far as possible from known high terrain.

SIGNIFICANT FACTORS

1. The engine failed due to a loss of effective lubrication. The reason for the loss could not be established beyond doubt.

2. The engine failure occurred in weather conditions that did not permit the pilot to carry out a visual forced landing onto favourable terrain.

3. The approach controller was unable to vector the aircraft to an obstruction-free landing site due to equipment and time limitations.

When the pilot lowered the landing gear the indications were that the left main gear had not extended. After several attempts at freeing the gear by recycling, the pilot decided to return to Horn Island where a ground inspection by maintenance staff was available together with emergency services. He also ascertained that the gear bulb was serviceable.

After a fly past, it was decided that the gear appeared to be down. The hydraulic system had pressurised which indicated to the pilot that the gear was most likely locked down. The pilot decided to land. On late final approach he feathered both propellers and made all switches safe. During the landing roll the left main gear collapsed rearwards to the trailing edge of the wing but the wheel continued to rotate. The wing of the aircraft did not touch the ground. All persons on board evacuated the aircraft safely.

Post flight inspection revealed that the centre drag bolt had sheared allowing the left gear to fold rearwards.

Evidence from the major defect report indicates that the bolt had failed as a result of being overstressed on a previous occasion probably as a result of an unreported heavy landing.

On left base for runway 26 at Essendon the right engine started to run roughly and surge and continued to do so until the aircraft landed. Towards the end of the landing roll the right engine stopped. The pilot reported that after the aircraft was parked the fuel gauges were indicating 200 lbs per side. When inspected, the right fuel tank was found to be empty. The right engine subsequently ran normally during a ground run with the left tank selected.

The aircraft was delivered to its maintenance organisation where it was determined that the indicating system for the left fuel tank was faulty. A signal condition unit was replaced and a fuel calibration carried out after which the aircraft was returned to service.

Investigation of the operational factors revealed that it is the operator's standard practice to fill the tanks to a total of 1250 lbs of fuel for a typical day's operation. It is not possible to see the fuel through the filler point when the tanks are only filled to this level. It is therefore normal practice to cross check fuel added against calculated fuel used on the previous flight and gauge indication as a check of fuel in the tanks.

On the flight that terminated in this incident, the pilot had crossfed fuel in flight from the right tank due to unbalanced gauge indications. Hence, the reason that the right tank ran dry while there was still plenty of fuel in the left tank.

Factors

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

• The fuel quantity gauge indication for the right tank was inaccurate due to a faulty signal condition unit.
• The inaccurate indication for the right tank led the pilot to believe that there was an imbalance between the left and right tanks.
• Because of this perceived imbalance he crossfed from the right tank during flight until the imbalance appeared to be corrected.
• This in turn resulted low fuel quantity in the right tank which eventually led to the right engine being starved of fuel.

FACTUAL INFORMATION

History of the flight

The PA-28 aircraft was inbound to Essendon using the Essendon Special Aerodrome Procedures. On initial contact with the Essendon aerodrome controller, the PA-28 was cleared to proceed from Point Ormond to Essendon runway 35. As the PA-28 passed west abeam the city, the controller instructed its pilot to maintain best speed and report on short final. Shortly after, the pilot reduced speed to lower flap for the approach. The approach was then made with partial reference to the visual approach slope indicator system (T-VASIS).

The CL600 aircraft was inbound from Sydney via the Plenty locator to Essendon. While the aircraft was on approach frequency, its pilot had accepted an offer from the controller to use runway 26 at Essendon. Twenty-five seconds after the PA-28 had reported abeam the city, the CL600 pilot contacted the aerodrome controller and reported at the Plenty locator.

He was instructed to report on short final, advised of the crosswind and that he was number two in the sequence. The pilot then conducted a practice instrument landing system (ILS) approach, believing that the number one aircraft was also landing on runway 26.

Approximately 2 minutes after the CL600 had reported at the Plenty locator, the PA-28 was cleared to land. It was then about 2 NM from the threshold of runway 35. At that time, the CL600 was about 4 NM from the threshold of runway 26. The landing clearance given to the PA-28 pilot was not heard by the CL600 crew as the outer marker audio tone came through at that moment and they were conducting final checks.

After a further 1 minute and 40 seconds, the controller advised the CL600 pilot that the number one aircraft was just crossing the threshold and to expect a late landing clearance. That landing clearance was given 20 seconds later. After a further 35 seconds, the CL600 pilot advised the controller that an aircraft had run into them. The two aircraft had collided at the intersection of runways 26 and 35.

Radar flight profiles

Radar data indicated that the original sequencing of both aircraft was appropriate. However, the situation soon changed and the CL600 maintained a position relative to the PA-28 in both distance and ground speed by a factor of two; that is, the speed of the CL600 was twice that of the PA-28, and its distance from the aerodrome remained constant at about twice that of the PA-28.

Radar data indicated that the aircraft symbols merged at the runway intersection. The PA-28 indicated a ground speed of 50 kts and the CL600 55 kts at the time of impact, 1747 EST. All available data indicates that the flight profiles were normal for both aircraft types.

Damage to aircraft

Damage to the CL600 aircraft was confined to the left wingtip and winglet. The winglet remained intact, but its leading edge was severely delaminated and there were scratches on the wing surfaces.

The left wing of the PA-28 aircraft was destroyed outboard from the wing fuel tank. The wing was partially pulled from the fuselage at the wing root and the fuel tank was damaged. There was some wrinkling of the left fuselage skin surface to the rear of the left wing.

Flight recorders

The CL600 aircraft was fitted with a Lockheed Aircraft Services flight data recorder (FDR) and a Loral Data Systems cockpit voice recorder (CVR). The PA-28 aircraft was not equipped with a FDR or CVR.

Flight planning

The pilot of the PA-28 aircraft had submitted a valid visual flight rules (VFR) SARTIME flight plan to the Melbourne Regional Briefing Office. The transmitted plan was correct and complete for the proposed flight. The flight plan indicated that the pilot intended to proceed from Moorabbin to Essendon using the Essendon Special Approach Procedures and then return to Moorabbin following orbits over the city area. Correct and completed flight progress strips were prepared and held at the Essendon Tower for the Essendon stages of the flight.

The inbound flight progress strip was held at the aerodrome controller position and the outbound flight progress strip at the surface movement controller position. The pilot of the PA-28 aircraft established contact with the aerodrome controller in accordance with the special aerodrome procedures and was cleared to enter controlled airspace and track to Essendon at 2,000 ft for runway 35.

The CL600 flight crew had submitted a valid instrument flight rules flight plan to the Melbourne Regional Briefing Office. The transmitted plan was correct and complete for the proposed flight. The flight plan indicated the final stage of the flight from Sydney was to track via the Plenty locator to Essendon.

A correct and complete flight progress strip was prepared and held at the Essendon aerodrome controller position for this flight. The CL600 crew had established contact with Melbourne Approach Control and advised they had received Essendon Automatic Terminal Information Service (ATIS) information Hotel, but did not report in-flight conditions. Approach Control advised the crew that Essendon ATIS had changed to information India and that the duty runway was now runway 35. They were also advised that runway 26 was available for landing with a 15-kt crosswind. The crew accepted runway 26 and, as they had not reported visual, were cleared for final and instructed to contact Essendon Tower at the Plenty locator. They established contact with the Essendon aerodrome controller at the Plenty locator and were then cleared to continue descent and track direct to Essendon for runway 26 as the number two aircraft.

Meteorology

At the time of the occurrence, the wind was 350 degrees at 10-15 kts, the cloud was 2 octas at 2,000 ft and 3 octas at 3,000 ft. Both controllers were aware that there had been strong northerly winds of 30-40 knots at 1,500-2,000 ft. The collision occurred about 2 minutes after last light. Although it was dark on the ground, visibility was good, and both aircraft were identified visually on first contact with the aerodrome controller. The ATIS reported visibility as 10 km. There was considerable background illumination along the flight path of the PA-28 between the city area and the runway intersection. It was clear overhead with showers and dark cloud reported to be low on the western skyline.

Orders, regulations and instructions

The Aeronautical Information Publications (AIP) OPS-CTL-18 and the Manual of Air Traffic Services (MATS) 6-3-35 define separation standards required for crossing runway situations.

Essendon Tower local operating instructions (section 4.22) provided directions on the confirmation of the landing clearance under a heading of reduced visibility in which the hours of darkness appear to be considered as constituting reduced visibility. However, these instructions related only to runways 26 and 08 and did not include runway 35.

Personnel

At the time of the accident, the tower was staffed with both an aerodrome controller and a surface movement controller who were both rated as full performance controllers.

The aerodrome controller had held a surface movement controller rating at Essendon since September 1994 and an aerodrome controller full performance rating since 28 May 1995, some 7.5 weeks before the accident.

Prior to September 1994, he had worked for approximately 15 years in the air traffic services training environment at Melbourne. Before this period, he had held a rating for approach/departures radar control at Melbourne which he last exercised in December 1979. The controller had been employed as a controller for 26 years. Prior to 28 May 1995, he had gained actual experience as an aerodrome controller for 2 years at Melbourne (December 1970 to November 1972) followed by a 9 month term at Essendon.

The pilots of both aircraft held licences and ratings appropriate for the flights undertaken.

Essendon Aerodrome

Essendon Aerodrome is 282 ft above sea level, with runways 08/26 and 17/35 crossing at right angles. Runway 26 is equipped with a localiser, ILS and high-intensity approach lighting. Each of the other three runways is equipped with a T-VASIS.

Essendon Control Tower

The control tower is located about 600 m north of the runway intersection on the west side of runway 35. At night, observation of the thresholds for runways 26 and 35 and the runways' intersection requires the controller to look into the distant lights of Melbourne and the very close lights on surrounding roads. The tower workstation is located such that the operating positions face east. Tower cabin roof stanchions are the only obstructions to visibility, but were not considered to be a factor in this occurrence. Depth of field judgement and the assessment of angular changes of landing aircraft can be difficult under poor ambient light conditions such as at night.

The runway in use at Essendon had changed a number of times during the afternoon due to simultaneous runway operations (SIMOPS) changes at Melbourne. Runway 26 had been the runway in use until about 12 minutes before the accident, when runway 35 was designated the runway in use. Runway 35 (1,585 m long), crosses runway 26 (1,921 m long) about 450 m from the runway-35 threshold and 1,000 m from the runway-26 threshold. Both runways had stage-two selections set for their relevant lighting.

Radar facilities

The aerodrome controller had access to a radar display for monitoring and traffic sequencing purposes only. There are no control settings other than range selection, and there are no velocity projections displayed on this equipment. The display was operational and continually monitored by the controller until the PA 28 was about 2 NM from the runway 35-threshold, after which the controller reverted to visual surveillance of both aircraft. The aircraft symbols on the radar display included groundspeed and altitude readouts.

Essendon Tower staffing

Normal staffing configuration during the hours of 0700 - 1700 local, specified that the Essendon Tower be staffed with an aerodrome controller, a surface movement controller, and a coordinator. At the time of the accident, the coordinator was not required to be present in the tower cabin.

Traffic processing

The controller intended the PA-28 to be number one in the landing sequence, as that aircraft was the closest aircraft to the runway in use and was landing into wind. At the time the sequence was formulated, both aircraft were on the radar display, but the CL600 had not passed the Plenty locator and was not on the Essendon Tower frequency.

The controller's strategic traffic processing plan was to maintain the PA-28 as number one and to monitor that aircraft past the intersection of runways 26/35 before issuing a landing clearance to the CL600, the number two aircraft in the sequence.

The controller informed the investigation he believed he had visually confirmed that the PA-28 had passed through the intersection before he gave the CL600 landing clearance.

The two accident aircraft were the only aircraft inbound to Essendon. There were no other surface movements at Essendon in the vicinity of the runway intersection. At the time of the accident the workload at the aerodrome controller operating position was low and not complex.

ANALYSIS

Aerodrome controller

The controller's strategic traffic processing plan for both aircraft was based on an approach and landing sequence using crossing runways. However, at no stage during this sequence did the controller pass traffic information to the crew of either aircraft, alerting them that both aircraft were being sequenced to land on crossing runways. Furthermore, neither crew was aware of the other's aircraft type, performance capabilities, or relative position.

From the time that the CL600 was at 10 NM, the controller knew that the sequence was likely to result in achieving separation close to the minimum allowable. He had available a number of alternative strategies to ensure separation. When the PA-28 was about 2 NM from the runway-35 threshold, the controller adopted visual surveillance of both aircraft to maintain separation. The controller was unable to recall the visual scanning pattern he adopted in relation to confirming his judgement that separation would be maintained.

As the sequence progressed, the controller incorrectly assessed the position of the PA-28 in relation to the runway intersection as well as its position relative to the CL600. At the time when the controller advised the CL600 crew that the PA-28 was crossing the runway (35) threshold and that they should expect a late landing clearance, radar data shows that the PA-28 was still on approach with 0.41 NM yet to be flown to the runway threshold.

This distance was approximately twice that of the distance from the runway threshold to the runway intersection. The investigation was unable to determine why the controller did not verify the position of the PA-28 in relation to the runway threshold or the CL600. Subsequently, the controller did not use the radar display to check his visual surveillance of the PA-28 position relative to the runway intersection. Furthermore, the controller did not verify his assumption by seeking confirmation from the PA-28 pilot that the aircraft had in fact crossed the runway intersection. The controller was unable to explain to the investigation why he did not avail himself of these options. C

L600 crew

After the crew advised the aerodrome controller that they had passed the Plenty locator, they were instructed by the aerodrome controller to report short final and that they were 'number two'. The crew told the investigation that on receipt of this instruction, they assumed that the number one aircraft was in the sequence ahead of them on approach to land on runway 26. The crew were making a practice ILS approach in visual meteorological conditions. The investigation was unable to determine whether either of the CL600 pilots conducted an external visual scan to verify their assumption.

The crew were subsequently advised that the 'number one' aircraft was crossing the threshold and that they should expect a late landing clearance. Twenty seconds later, they were given clearance to land. On receipt of the advice to expect late landing clearance, the pilot in command apparently felt some concern and was considering a go-around but did not discuss this with the other crew member. The co-pilot also had some concerns which he did not communicate to the pilot in command. Their concerns, although unshared, represented a potential cue for the crew to resolve with the controller, any doubts they may have had that the number one aircraft in the sequence was in fact preceding the CL600 to land on runway 26. Before the crew could speak to each other, the controller cleared them to land.

After receiving this clearance, the crew would have concluded that, as they were operating under positive control, the runway was clear, and they would have confirmed this by visual observation.

Pilot in command PA-28

A number of factors would have influenced the pilot's ability to maintain a complete awareness of his environment. He was occupied with the process of flying the aircraft to ensure a smooth landing for the comfort of his passengers. Furthermore, due to his low level of experience in night flying, he was also concentrating on the T-VASIS approach and for the correct taxiway on which to exit.

SIGNIFICANT FACTORS

1. The controller adopted and maintained a traffic sequence, which as it progressed, was unlikely to result in achieving the required separation.

2. The controller misjudged the position of the PA-28 in relation to the runway-35 threshold and the position of the CL600.

3. The controller did not seek verification from the PA-28 pilot that his aircraft had crossed the runway intersection.

4. The controller did not provide the required separation.

SAFETY ACTION

The Bureau of Air Safety Investigation issued interim recommendation IR950209 to Airservices Australia on 23 November 1995. It stated:

"The Bureau of Air Safety Investigation recommends that Airservices Australia revise the standard operating procedures in relation to runway separation standards applicable to intersecting runway operations at locations where azimuth resolution is difficult to assess or not available.

"The procedure should ensure that under such conditions, whenever runway separation is based on an assurance that an aircraft is clear of a runway intersection, corroborative evidence is obtained to confirm that separation will be achieved."

Airservices Australia replied on 11 December 1995 as follows:

"BASI IR 950209 recommends that "Procedures should ensure ... whenever separation is based on an assurance that an aircraft is clear of a runway intersection, corroborative evidence is obtained to confirm that separation will be achieved."

"The current procedure described in MATS 6-3-6 is clear -

"B shall not be permitted to cross the runway threshold until preceding .. landing aircraft A has crossed the relevant runway intersection or has stopped short of the intersection."

"How this procedure is achieved and ensured at specific locations is a matter of technique, and should therefore be an issue of local training and rating, with possible incorporation in Local Instructions (LIs).

"Discussions have been held with the manager ATS Training regarding ATC responsibilities for ensuring the procedure and for specific inclusion of the issue into the training syllabus. "No change to current national procedures is proposed."

The Bureau assessed this response as OPEN and further correspondence was entered into. A letter was sent to Airservices Australia on 12 August 1996. It stated, in part:

"Thank you for your response to Interim recommendation 950209 regarding azimuth resolution for intersecting runway operations. While I am pleased to read that you intend to modify the training syllabus so that it will include specific instruction related to achieving a standard, I feel that the main point of the recommendation may have been missed.

"While I agree that the procedure in MATS 6-3-6 is clear, I would wish to see some corroborative evidence available to the controller in situations where azimuth resolution is either difficult to assess or not available at all.

"The application of any such device/procedure may vary from location to location and even from runway to runway at the same location. It may also be deemed to only apply on certain runways at certain times, for instance, night operations."

Airservices Australia further replied on 18 September 1996 as follows:

"I refer to your letter dated 12 August 1996, regarding Airservices' initial response to BASI Interim Recommendation 950209. In that letter, you highlighted concerns that our proposals regarding azimuth resolution for intersecting runways, did not provide any corroborative evidence to a controller that the requirements of MATS 6-3-6 Para 35 had been met.

"While still of the opinion that the issue remains one that should be incorporated as part of local training and rating requirements, we propose to include additional guidance in MATS by amending the relevant paragraph as follows:

"Aircraft B shall not be permitted to cross the runway threshold until preceding departing or landing Aircraft A has crossed the relevant runway intersection or has stopped short of the intersection. Azimuth resolution, particularly at night or in reduced visibility, can affect the ability to visually determine an aircraft position on a runway. When visual determination is limited by azimuth resolution, the pilot shall be instructed to report when either of the above requirements has been met."

The Bureau assessed this subsequent response as CLOSED-ACCEPTED.

The pilot reported that the flight proceeded normally to Mt Holland. In the circuit at Mt Holland gear was selected down as well at 15 degrees of flap. The flap extended normally, however only the nose gear and the right main gear indicated down and locked. The gear was recycled several times with the left main gear continuing to indicate unsafe. As the gear problem couldn't be rectified a decision was made to return to Perth. On departure from Mt Holland the flaps would not retract from their 15 degrees position. The aircraft was diverted to Jandakot to avoid congestion at Perth and to allow the use of a grass landing strip.

The aircraft was landed on the left hand edge of runway 30 at Jandakot. The plane touched down normally and as it slowed the left wing touched down on the grass alongside the runway. The plane slewed slightly to the left and slowed gradually to a halt.

A post-accident inspection indicated that the left main gear up-lock pivot bolt was corroded. The corrosion caused increased drag during gear extension and the up-lock had not released by the time gear extension had started. The left main gear actuating rod fractured in overload and the left gear remained in the up position. The right main and nose gear extended normally. The actuating rod had fractured in the vicinity of the flap motor and part of the rod had dislodged the electrical supply to it. This caused the flaps to remain at 15 degrees.

The pivot bolt is an on-condition item and is not normally checked during regular servicing. The aircraft had recently been returned to service following a two year absence after a gear-up landing. The right main pivot bolt had been removed and greased during the maintenance recovery process, but the left had not.