FACTUAL DATA

VH-CZK and VH-TAZ were both enroute from Melbourne to Sydney on the same track.  CZK departed Melbourne at 0544 UTC and was cruising at flight level (FL)330.  TAZ departed Melbourne at 0546 and was cruising at FL350.  Both aircraft transferred from Melbourne Sector 2 to Melbourne Sector 7 at 0613.  CZK was instructed to hold at Cullerin and was cleared to descend when ready to FL240 with a requirement to be at FL240 by Cullerin.  TAZ was also instructed to hold at Cullerin and cleared to descend when ready to FL250 with a requirement to be at FL250 by Cullerin.  At this time the two aircraft were separated by 18 NM with a closing speed of 20 kts. Both aircraft had previously been issued with standard arrival route (STAR) clearances for Sydney when they transferred from Departures Control to Sector 2.

At 0614 CZK reported leaving FL330 on descent and at 0617 TAZ reported leaving FL350 on descent. At 0617 the distance between the two aircraft had closed to 7 NM and the closing speed had increased to 125 kts. At 0618 the aircraft were 4 NM apart with a closing speed of 160 knots and approximately 4,000 ft vertical separation.

At 0618.44 CZK was instructed to cancel holding at Cullerin, resume the Rivet one STAR, hold at 70 NM Sydney and descend to FL220.  At 0619.06 CZK was instructed to reach FL220 by 70 NM Sydney.  The first requirement to reach FL240 by Cullerin was not cancelled.  By this time the two aircraft were 2 NM apart with a closing speed of 182 kts and 2,800 ft of vertical separation.

At 0619.30 when the radar blips for the two aircraft merged the vertical separation was 2,300 ft, and when the blips parted as TAZ overtook CZK, vertical separation was 1,600 to 1,800 ft. When TAZ was 2 NM ahead of CZK both aircraft were at FL256 just short of Cullerin.  CZK was at FL248 at Cullerin instead of FL240 as instructed.

At 0620.28 the controller noticed for the first time the minimal longitudinal and vertical separation between the two aircraft and instructed TAZ to maintain FL260.  TAZ did not respond so the instruction was repeated at 0620.40. Again, there was no response, and the instruction was repeated at 0620.47. By the time TAZ responded it had descended below FL260. The controller then asked CZK "do you have the traffic sighted in your twelve o’clock at five miles". At this time TAZ was estimated to have been only 2 to 3 NM in front of CZK.

The high closing speed that developed between the aircraft resulted from CZK slowing down in preparation for entering the holding pattern. CZK did not notify the controller of a variation to standard descent profile as required by AIP/OPS CTL 9 and the controller did not notice the speed differential developing between the aircraft.

When the holding requirement for CZK at Cullerin was cancelled and the new holding instruction to be at FL220 by 70 NM Sydney was issued, the crew of CZK believed the Cullerin descent requirement was no longer current.  The controller did not restate, nor was he required to restate, that the first descent requirement was still current.  CZK did not reach FL240 by Cullerin.

Neither aircraft were fitted with a traffic alert and collision avoidance system (TCAS).

ANALYSIS

When the aircraft transferred to Sector 7, they were separated by 18 NM with a closing speed of 20 kts.  As both aircraft were to hold at Cullerin they were issued with descent clearances and descent requirements which were intended to establish vertical separation before turning outbound in the holding pattern.  With 18 NM separation, about 60 NM to run to Cullerin and a closing speed of 20 kts, the controller would normally be confident that the aircraft could maintain sufficient longitudinal separation into the holding pattern.  The controller apparently assessed this to be the case and discounted the need to pay further attention to the closing speed.

The crew of CZK did not advise the controller that the descent speed had been reduced from standard profile in preparation to enter the holding pattern.  When crews wish to vary descent from standard profile by more than 10 kts or M.025, they are required to advise air traffic control in accordance with AIP/OPS CTL-9, para 20.1.

When the holding requirement for CZK at Cullerin was cancelled and new holding and descent requirements were issued, the initial requirement to be at FL240 by Cullerin was not cancelled.  The crew mentally discounted the original Cullerin descent requirement when the new holding and descent requirements were issued.  In such circumstances it is understandable how crews could make such an assumption simply on the basis that the descent requirement was associated with the holding requirement which was cancelled.  With hindsight, it would have been prudent for the controller to have stated that the Cullerin descent requirement was still current.  It may also have been prudent for the crew of CZK to clarify the matter.

When the controller finally noticed the ensuing separation problem with the two aircraft, he instructed TAZ to maintain FL260.  TAZ did not respond until the instruction had been issued three times by which time it was too late to prevent loss of separation between TAZ and CZK.

Neither of these aircraft was fitted with TCAS.  Had TAZ been so fitted, the crew may have received a resolution advisory as they approached CZK.

This occurrence also involves situational awareness considerations.  Both crews were monitoring the same radio frequency, and both should have heard transmissions to/from each other's aircraft. They were under radar control and should have been able to rely on the controller for separation advice. When the crew of CZK varied their descent profile without advising the controller, the potential arose for a reduction in longitudinal separation. Failure to comply with the Cullerin descent requirement then led to a breakdown of separation. The crew of TAZ were not aware of either of these aspects and therefore had no cues pointing to an impending problem.

CONCLUSION

Significant factors

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

1. The controller did not believe that longitudinal separation would be a problem. Consequently, he did not adequately monitor the progress of CZK and TAZ.
2. The crew of CZK did not advise the controller that they were descending at a speed well below the standard profile speed.
3. The crew of CZK incorrectly assumed that the Cullerin descent requirement was cancelled when they were issued with new holding and descent requirement instructions.
4. The status of the Cullerin descent requirement was not queried or clarified by the crew of CZK or the air traffic controller.
5. Neither aircraft was fitted with TCAS.
6. The crew of CZK did not maintain adequate situational awareness.
7. The crew of TAZ did not respond to a control instruction to limit their descent to FL260 until it was too late to prevent the loss of separation.

SAFETY ACTION

As a result of the investigation the Bureau of Air Safety Investigation issued an interim recommendation IR 950088 to the Civil Aviation Authority on 21 June 1995.  It stated:

The Bureau of Air Safety Investigation recommends that the Civil Aviation Authority revise ATS phraseologies and procedures so that whenever a new requirement is issued, the status of the previous requirements is clarified.

The Civil Aviation Safety Authority response was received on 15 August 1995.  It stated:

Reference IR950088

This recommendation relates to the application of subsequent altitude requirements and proposes that ATS phraseologies and procedures be modified to ensure that whenever a new requirement is issued the status of the previous requirement is clarified.

ATS agrees with this recommendation and proposes the inclusion of the following text into MATS/AIP documentation at the next opportunity:

xx.1 Except as stated in xx.2, whenever a level restriction or requirement has been imposed, and subsequently a further level/restriction is imposed, the subsequent instruction will cancel all previous restriction/requirement(s), unless:

1. all restrictions/requirements are re-stated; or
2. the subsequent instruction is prefixed "FURTHER REQUIREMENT";

xx.2 If a STAR or SID has been issued, the level of tracking restrictions will always remain in effect unless: a. the aircraft has been vectored away from the SID or STAR after commencement; or

b. ATC advises "CANCEL STAR/SID"

MATS ONLY

NOTE Controllers should be aware that where level requirements are imposed through a letter of agreement with an adjacent sector, issuance of new requirements may invalidate previous requirements unless the procedures xx.1 and xx.2 are adhered.

The Bureau has classified this response as CLOSED/ACCEPTED.

The aircraft arrived at the country airstrip ten minutes after first light. The pilot reported that there were no signs of animals in the area, but that during the subsequent landing roll a kangaroo jumped out in front of the aircraft. The animal collided with the left mainwheel which collapsed causing the left propeller to strike the ground and the aircraft to veer to the left. The aircraft ran off the strip into a ditch, tearing off the nosewheel. Neither occupant of the aircraft received injuries.

At approximately 500 ft after take-off the engine began to run roughly.

The aircraft was immediately positioned for a landing back on to the departure runway. The engine was still developing sufficient power at this point to complete a climbing turn to 800 ft. Approximately mid-down wind, the engine began to run very roughly and then lost all power. In the subsequent forced landing, the aircraft touched down approximately one third of the way along the runway. The pilot was unable to bring the aircraft to a halt in the distance remaining to avoid overrunning the the end of the strip. The aircraft came to rest part way down the sloping sea wall at the end of the runway. All three occupants were able to evacuate the aircraft safely.

Examination of the engine found that the centre electrodes for both spark plugs in the number four cylinder were excessively lead fouled and unable to fire. The porcelain surrounding the electrode on the top spark plug for number two cylinder was also cracked and indications were that this plug was firing intermittently. No other faults were found that could have contributed to to the power loss.

When the AFTN strip was made up from the aircraft's flight plan, the flight data officer did not designate the route by inserting the correct address code. When another flight data officer came to transmit the AFTN message he noted that the address code was missing. Instead of checking the flight plan he apparently made a best guess using the departure and destination aerodrome information. However, he guessed the wrong route. Consequently, some of the addressees were omitted, including the Townsville arrival's position. When the B747 departed from Brisbane, a departure message was also not sent to the Townsville arrival's controller.

When the aircraft came within the sector seven controller's jurisdiction he omitted to annotate his flight strip with the updated estimated time of arrival for the aircraft. This mistake was not recognised and coordination for the aircraft with the Townsville arrival's controller was not accomplished. The omission was not noted until the Townsville arrival's controller asked about an unknown aircraft entering his airspace from the south-east. The B747 had been maintaining 31,000 ft and there were no conflictions with other aircraft.

The sector was busy at the time with congested traffic in the Mackay/Whitsunday area which included an international aircraft with radio communications problems and unnotified light aircraft traffic asking for clearances at the new airspace boundaries in the Mackay area. While all the controller's attention was focused on this area, the high altitude B747 was overlooked.

The radar and procedural sector seven consoles were manned with a trainer and trainee at each console. The radar controller was undergoing a final check before being rated on the position. The radar console also suffered from some ergonomics deficiencies. The coordination intercom line was not operating, and the hand operated radio transmission switch was unserviceable. The radar operator had to lean across the procedural console to use its coordination line. The training was also a distracting factor because of trainer/student interaction and as a result the controllers had less opportunity to monitor each other.

The procedural console was manned by a trainee and trainer who had not operated together before. The trainee was being shown a method of laying out his flight strips which involved an altitude ranking rather than a chronological order as previously used by the trainee and his full-time instructor. This disrupted his scanning technique.

The complex combination of factors resulted in a lack of coordination between the various air traffic service units responsible for the supervision of the B747 flight.

The pilot reported hearing several unusual noises from the right side of the aircraft while backtracking in preparation for take-off from runway 08. The aircraft then veered sharply to the right and ran off the sealed surface before the pilot was able to bring it to a halt. The right mainwheel had collapsed.

The investigation found that several bolts had came loose from the inner and outer flanges of the three piece wheel assembly. The right main tyre had recently been replaced and only the outer wheel flange was removed to facilitate the tyre change. The torque on the inner flange bolts was not re-checked after the new tyre was fitted.

The pilot attempted to start the engine for the return flight to Darwin, but the starter motor failed to operate. He then applied the handbrake, chocked the nose-wheel and hand-swung the propeller. After several attempts the engine fired then ran at a high RPM speed causing the aircraft to jump over the chock and head towards the airport fence. After unsuccessfully attempting to enter the cabin the pilot tried to grab a main wheel, but missed. He next grabbed at the tailplane but was knocked to the ground. The empty aircraft then ran through the airport fence, across a road and into a ditch, where it came to rest suffering substantial damaged.

The pilot reported that he established the aircraft on final approach at 60 kt, with full flap selected. He assessed that the aircraft was slightly high on the approach, so he lowered the nose of the aircraft and flew it on to the ground to touch down near the runway threshold. The aircraft bounced and the pilot added some power to cushion the second touchdown. The aircraft then bounced again, more severely than the first bounce, so the pilot elected to go around and applied full power. He stated that the aircraft seemed sluggish and stabilised at about 2 m above the strip, so he retracted the flap to 20 degrees. He then became concerned about the high ground beyond the airstrip and flew towards a gap between trees about 30 m to the right of the strip. He banked the aircraft to avoid a fence and, on seeing more trees ahead, levelled the wings and closed the throttle. The left wingtip dug into the sloping terrain and yawed the aircraft. As the aircraft slowed further, the nose gear was torn off and the right gear bent backwards. The pilot could not recall hearing the stall warning horn operate at any stage during the sequence.

Witnesses reported that, while aircraft belonging to the operator involved in the accident always landed towards the north-west, other operators who used the strip landed towards the south-east when wind conditions dictated, by flying a curved approach to avoid the high ground beyond the end of the strip. The witnesses reported the surface wind as being from the south/south-east when the aircraft flew the approach. The aircraft was described as being close to the runway on base leg and to then fly a steep approach compared with other aircraft they had observed land at the strip. They stated that the aircraft touched down some distance into the strip, up to halfway between the end of the strip and the windsock, and to bounce four or five times before attempting to go around from a position past the windsock.

There was no apparent fault with the aircraft which might have contributed to the accident.

Neither the touch-down or attempted go-around positions could be determined accurately. The performance of the aircraft during the attempted go-around, particularly after the partial flap retraction, indicates that the aircraft probably was operating in ground effect.

Three local considerations were identified which could have contributed to the occurrence:

1. the high ground beyond the south-eastern end of the strip could have created an illusion that the aircraft was low and led the pilot to fly a steeper than normal approach path;
2. the actual wind at the approach end of the strip could have been different to that indicated by the windsock which could have been subjected to local effects caused by the high ground adjacent to the strip; and
3. the pilot was aware that he was operating a charter flight and perceived some pressure to land from the approach, rather than fly another circuit.

The factors considered relevant to this accident were:

1. The pilot's relatively low level of flying experience.
2. The position of the windsock was such that it might not have provided a realistic indication of the surface wind at the south-eastern end of the strip.
3. The terrain under the approach path could have contributed to the pilot experiencing an illusion relating to the aircraft’s approach angle.
4. The pilot perceived pressure to land from the approach.
5. The aircraft was probably high and fast on final approach.
6. The aircraft landed downwind.
7. The pilot made a late decision to go around.

When the landing gear was selected down for landing at Bundaberg, the landing gear motor was heard to operate only momentarily before the landing gear circuit breaker popped, and a burning smell entered the cabin. The circuit breaker was reset and again the landing gear motor appeared to function only momentarily before the circuit breaker tripped. The pilot advised that he then tried unsuccessfully to lower the landing gear using the manual emergency extension. A decision was then taken to return to Brisbane where a "gear up" landing was carried out. All five occupants were able to exit the aircraft safely.

VH-DBB was one of four aircraft conducting circuit training on runway 26L. The pilot was advised by air traffic control that her aircraft was number three in sequence and to follow an aircraft on mid-downwind, but she mistook a landing aircraft as the aircraft to follow and turned base in front of the number two aircraft. The air traffic controller noticed the conflict and alerted the aircraft so that avoiding action could be taken. The aircraft passed within 200 feet laterally of each other.

The owner-pilot of VH-DBB had been conducting refresher training and was familiar with the aircraft and Parafield and therefore conducting reasonably tight circuits. The other aircraft were being flown by ab initio students under dual instruction and carrying out wider than normal circuits. This led the pilot of VH-DBB to mistake the aircraft on final as the number two aircraft, which she had lost sight of in the ground clutter, and made her turn onto final approach to follow that aircraft. The correct aircraft was on a long final approach at the time. Both of these aircraft were of the same type and similar colour.

The helicopter arrived at Mildura at about 1745 EST. The pilot was marshalled to a parking spot by the refueller. After the helicopter was refuelled, the pilot offered to reposition the helicopter but the refueller suggested it remain parked where it was, as had been common practice in the past. The pilot complied with the refueller's advice. The helicopter was not parked on a taxiway.

At 2045 EST, while taxiing to the terminal, in very dark conditions, the Cessna 404 pilot followed a yellow taxi guideline with the aircraft's taxy light illuminated. He was momentarily distracted by the windsock lights flashing and inadvertently allowed the aircraft to drift about one metre to the right. As he returned his attention to the yellow line, he suddenly saw the parked helicopter in his peripheral vision. He attempted to stop but the right propeller contacted one rotor blade and the right wing tip impacted the windshield of the unattended helicopter. The collision occurred about 25 metres from the usual parking bay for the Cessna. The Cessna 404 pilot was not expecting a helicopter to be parked where it was.