A Cessna Conquest aircraft (VH-YFD) was enroute Perth to Meekatharra via the Mount Magnet VOR at FL250. Another Conquest (VH-FMQ) was flying in the opposite direction, Meekatharra to Perth via the Mount Magnet VOR at FL240. Both aircraft had filed IFR flight plans, were inside Perth controlled airspace and their Mount Magnet position estimates were within 2 minutes of each other. YFD had advised a DME position for descent to Meekatharra and the Perth Centre controller subsequently calculated that the traffic would be passing and may require separation.

When YFD reached Mount Magnet, the pilot transmitted the position to Perth FIS and reported that he was planning to commence descent 2 minutes later. Perth FIS acknowledged the transmission and passed known traffic. Soon after, Perth Centre, unaware that YFD had changed to FIS frequency, unsuccessfully attempted to establish radio contact with YFD to arrange separation with FMQ. YFD had descended through FMQ's level by the time YFD had returned to the correct frequency.

The Perth Centre controller reviewed the aircraft positions and assessed that a breakdown of separation had probably occurred. Day VMC existed at the time of the incident.

The pilot of YFD reported that whilst he was within regulated duty hours, the day's flying program had changed a number of times with diversions and periods of waiting at various airfields in the heat of the day. He also reported that air traffic and company frequencies were very busy at the time of his transit to Mount Magnet.

FIS staff reported that Perth Centre regularly instructed aircraft to call FIS on descent to Meekatharra for traffic. It was also common for aircraft to call on the FIS frequency without prior notice from Perth Centre due to time constraints and workload.

The planning and attention required to cope with flight diversions and associated effects of waiting in the heat, probably fatigued the pilot and reduced his level of attention. His attention may have also been diverted by the radio traffic during the transit to Mount Magnet. A combination of fatigue, distraction and the regular practice of contacting FIS for descent may have influenced the pilot to contact FIS without direction from Perth Centre.

Due to the regular occurrence of aircraft appearing on frequency without prior notification, the FIS operator did not realise that the aircraft was descending without a clearance.

Perth FIS have reported that they and ATC are reviewing coordination procedures.

The pilot stated that he had experienced a landing gear retraction problem the previous week, which was checked by a LAME, but no faults found. On the day of the occurrence, he decided to fly a circuit to verify the landing gear operation.

After take-off the landing gear retracted normally. The pilot continued with the circuit, maintaining separation with an ultralight aircraft also operating in the circuit area.

On the downwind leg the pilot reported the aircraft suffered a radio problem which he attempted to rectify while still maintaining a lookout for the ultralight aircraft. This allowed his attention to be diverted from operating the aircraft and failure to carry out the pre-landing checks, including landing gear extension, resulting in a wheels up landing.

During initial climb after take-off from Wynyard the engine suffered a power loss. The pilot observed the manifold pressure decreasing so he selected alternate air, checked the mixture control was set to rich and checked the fuel pump was switched on. He changed the fuel selection from the left tank to the right tank, but the engine did not respond. By this time the aircraft was low over the water, so the pilot transmitted a PAN call advising of the emergency and his intention to try to land on a beach. When the aircraft had descended to about three metres above the water and its speed had decayed to 60 knots, the pilot broadcast a MAYDAY call. Shortly afterwards the aircraft was stalled into the water at the mouth of the Inglis River. The impact forces broached the fuselage which rapidly filled with water. The pilot and his two passengers evacuated the aircraft before it sank and were rescued by the crew of a nearby fishing boat.

The investigation into the cause of the engine power loss was hindered because the aircraft was badly damaged during the accident and the subsequent recovery exercise. It was established that sufficient fuel was on board for the proposed flight and fuel was available to the fuel distributor, but the contents of the fuel filter assembly could not be determined.

The engine was inspected and disassembled, and relevant components were tested. It was found that the air duct hose fitted between the air filter and the fuel control unit was collapsed due to disbonding of the internal supporting wire. It could not be determined if this had occurred prior to the ditching and was the cause of the power loss or had occurred due to the forces/pressure of the water in the engine bay during the ditching.  No other anomalies were found that could have caused the power loss.

The air duct hose was one that is commonly called a 'SCAT' hose and was made up of a single layer of neoprene impregnated fabric material supported internally by a spring steel helix wire bonded to the fabric.  This SCAT hose is not approved by the manufacturer for this installation. The correct hose carries the manufacturer's part number and is constructed of a 2-ply silicone resin impregnated with woven fibreglass which is bonded and cured along with an inner liner and tabbed ends to facilitate retention. It is also wire reinforced with galvanised hard temper spring steel.

The manufacturer of the SCAT hose has recently changed the specification for these hoses to say that they are 'not recommended for negative pressure applications'. Many aircraft have SCAT or similar hoses fitted to negative pressure engine intake systems, as was the case with this aircraft.

Significant factors

1. It is suspected that the SCAT hose collapsed reducing the inlet air supply to a level that precluded the engine from delivering full power.
2. The SCAT hose was not the hose that was designated by the manufacturer to be installed in the air inlet system.
3. The pilot was forced to ditch the aircraft into water.

Safety action

1. Information on engine intake hose installations is available in an article 'SCAT/SCEET hoses linked to engine failure' published in the CASA Flight Safety Australia Summer 1997 issue.
2. CASA advise that a program is being developed to examine the ramifications of the widespread use of SCAT hoses in engine negative pressure air inlet systems.

The pilot reported that while flying at 4,000 ft, engine operation began to deteriorate. Initially this was manifested by intermittent coughing/missing but over the next few minutes RPM and power output decreased to the point where altitude could no longer be maintained. Engine instrument indications were all normal and throttle movement or carburettor heat application did not rectify the problem.

The engine finally lost all power, and the pilot was committed to a forced landing. The aircraft finally came to rest in a rough rock-strewn paddock, with substantial damage to the right main landing gear support structure.

A subsequent inspection of the engine revealed no internal faults that could have contributed to the power loss. However, the engineer who conducted the engine strip had been associated with the aircraft for a number of years. He said that the engine has no oil cooler and tends to overheat especially on hot days or with too lean a mixture. The carburettor/associated fuel lines are located such that when the engine does overheat, the system is highly susceptible to fuel vaporisation. In the absence of any other obvious reason for the failure, it was his opinion that the power loss was due to fuel vaporisation.

The crew were having problems with the survey equipment, so they decided to land at Bencubbin to investigate. The wind was from the west at 20 kts with gusts to 35 kts. The landing strip at Bencubbin is aligned 160/340 degrees. It slopes up to the north, is 970 m long with a gravel surface and power lines on both approaches. Field elevation is 1000 ft.

After conducting an airborne inspection of the strip, the pilot decided to land into the north. Because of the crosswind he decided to use 10 degrees of flap for the landing. The pilot reported that the first 100 m of strip was overflown due to its (unsuitable) surface condition. As the aircraft touched down, at approximately 80 kts, it was hit by a wind gust from behind, which resulted in a heavy touchdown and subsequent bounce.

The pilot immediately initiated a go-around but with the loss of airspeed associated with the initial bounce and an increasing tailwind component, the aircraft continued to run along the upsloping gravel surface. The go-around attempt was then abandoned in consideration of the powerlines off the end of the strip. The pilot was unable to stop the aircraft overrunning the end of the strip where it finally came to rest in adjoining scrub, substantially damaged.

As he initiated forward flight the helicopter began to sink and loose main rotor RPM, which he was unable to regain in the time available by lowering the collective control to reduce the main rotor blade pitch angle. He turned the helicopter through 90 degrees to the right, which would have reduced the tail rotor blade pitch angle, but it kept on descending without any rotor RPM increase. He then turned left and tried to find enough room through the trees to afford a recovery, but the main rotor struck a tree about 20ft above ground level and the helicopter rolled to the right before impacting the ground. The pilot and his two passengers evacuated with minor injuries.

The helicopter was 73kg below its maximum take-off weight at departure, and within its longitudinal and lateral balance limits. The temperature was about 28 degrees Celsius and a very high humidity, with the density altitude approximately 2,000ft. In these conditions the helicopter’s performance would have been reduced, but it still had sufficient engine power at take-off to effect a vertical climb, which would have reached its limit when the helicopter was hovering out of ground effect at the top of the climb.

As he changed from the hover to forward flight, the pilot probably increased collective pitch slightly to overcome a loss of height as the cyclic control was moved forward.  This would have started the rotor RPM decay as no more engine power was available to maintain it. There was insufficient height above the treetops for the helicopter to settle and allow time for the rotor RPM to recover when the collective control was reduced, or to obtain airspeed by diving to provide translational lift.

The pilot reported a nil wind condition, but thought he may have experienced a slight tailwind during the climb. In either condition, with the engine power available, he would have had difficulty hovering out of ground effect, then initiating forward flight without some form of translational lift being available, such as a headwind or by diving.

The tug pilot released the glider from tow shortly after take-off because the glider did not appear to be climbing. The tug pilot advised that he had lifted of at approximately 55 knots, allowed for drift, let the speed stabilise at 70 knots, then commenced to climb. After he had climbed to about 100 feet above the strip he noticed that the glider was very low behind him. He stated that he made a radio call to the glider telling him to "come up". He noticed the speed was deteriorating below 55 knots, he had full forward elevator applied and the stall warning had activated. The tug pilot considered that the glider was excessively out of station and that if the tow continued it would affect the safe operation of the tug. He therefore released the tow rope. The tug completed a circuit and landed safely.

The glider pilot stated that he selected negative flap during his preparation for launch. He stated that the tug commenced its tow and lifted off after a normal ground run. The glider was skipping and not lifting off. He moved the flap back two notches, looked at the airspeed indicator and it showed around 55 knots. He stated that the "tug went up like a rocket" and climbed well above the glider. He pulled back on the control column to try to catch up with the tug. Shortly after this he heard the tow rope release.

After being released he turned left, flew for a few hundred metres before turning right, and then outlanded into a small field covered in stubble. Once on the ground the glider ground looped in the stubble and slid backwards into a fence. The glider was substantially damaged.

After the accident the glider was found to be configured with the flaps in the "negative flap" setting. This setting is a feature that is used to reduce drag during high-speed cruise. The negative flap setting can also be used in the first segment of a take-off roll to increase the low-speed effectiveness of the ailerons. When this procedure is employed the flaps are reconfigured to the take-off setting as soon as the wings are levelled and under positive aileron control. The continued use of the negative flap setting during take-off and climb seriously degrades the climb performance of the glider.

The pilot was not able to explain to the investigator from the Gliding Federation of Australia (GFA) why the flaps were still selected to an inappropriate setting. 

There is no evidence of the flaps having moved as a function of the accident sequence therefore it can be concluded that the pilot did not apply landing flap during the approach into the stubble field. It is probable that the flap setting was not changed during the take-off run. This would explain the lack of climb performance experienced during the take-off sequence.

The student had just completed a dual check and was taxiing for a period of solo circuit training. He reported that as he taxied along the taxiway he checked the holding point for conflicting aircraft but did not see any navigation or anti-collision lights. As the Cessna approached the holding point the pilot's visibility was affected by glare from the landing light of an aircraft on final approach and he did not see the Grob parked in front of him. The Cessna's propeller struck the tail of the Grob.

ACTUAL INFORMATION

A Boeing 737 (B737) was following a Boeing 767 (B767) for arrival at Brisbane. Both aircraft were from Cairns and were being radar vectored by the Sector 3B controller. The controller was undergoing a periodic check and had seven aircraft on frequency with five being radar vectored for sequencing. The periodic check required the controller's performance at the position to be monitored and assessed by another rated controller (check controller). The aircraft being vectored were in two groups that were approaching Brisbane via different reporting points; SMOKA and PERCH. There was a considerable number of radio transmissions and co-ordination calls relating to the management of the two traffic sequences. The two Boeing aircraft were the last two aircraft in the SMOKA sequence. The controller of an adjacent sector was required, by local instructions, to establish a 20 NM trail between arriving aircraft. This controller asked the Sector 3B controller if this was required. The Sector 3B controller replied that that this was not required. Sector 3B is required to establish a 15 NM trail between aircraft by 40 NM from Brisbane. The following B737 was maintaining a slightly higher groundspeed on descent than the B767 and the distance between the aircraft was reducing. The Sector 3B controller instructed the crew of the B767 to turn onto a heading of 090 degrees, for sequencing, which caused the aircraft to cross the intended track of the B737.

The check controller assessed that the separation would be maintained and continued to monitor the Sector 3B controller's actions. The Sector 3B controller reassessed the situation and instructed the crew of the B737 to maintain FL220. The B767 was on descent to FL170 and the Sector 3B controller instructed the crew to continue descent to FL130. The controller believed that the flight profiles of the aircraft, while complying with his instructions, would achieve vertical separation of 1,000 ft between the two aircraft. This would be attained by the B767 passing through FL210 prior to the horizontal separation reducing to less than 5 NM. A controller on an another position had been observing the situation, with the diminishing horizontal and vertical separation between the two aircraft, and queried the Sector 3B controller as to whether the latter was satisfied with the situation. The Sector 3B controller did not acknowledge this query but immediately instructed the crew of the B737 to turn right a further 10 degrees. He intended to maintain horizontal separation by vectoring the B737 behind the B767. The check controller assessed that the horizontal separation standard would be infringed while there was no vertical separation standard being applied and instructed the Sector 3B controller to issue traffic information to the crew. The provision of traffic information was in accordance with the Manual of Air Traffic Services (MATS). The MATS states that when a separation standard does not exist and in a controller's opinion the proximity of aircraft warrants, traffic information shall be issued to the relevant crews. The crew of the B737 were aware of the B767 and had been watching the aircraft as they approached. The crew of the B737 had reduced speed and as they were discussing that separation appeared to be reducing the Sector 3B controller issued traffic information. The two aircraft passed with horizontal separation of 3.8 NM and vertical separation of 600 ft. There was a breakdown of separation.

ANALYSIS

The Sector 3B controller increased his overall workload by cancelling the requirement for the adjacent sector controller to establish all aircraft in a 20 NM trail. The establishment of a 20 NM trail by the adjacent sector controller would have assisted the Sector 3B controller in managing his workload. His level of work and complexity was compounded by having to achieve the required spacing between aircraft and to manage the two arrival sequences. He did not recognise that the horizontal separation between the B737 and the B767 was reducing. Also, he did not employ appropriate separation assurance techniques before issuing radar vectors to the crew of the B767 that would cause that aircraft to cross in front of the B737 with minimal horizontal separation. The intervention by another controller prompted both the Sector 3B and the check controller to act to maintain separation. However, the turn provided to the crew of the B737 was too late and the check controller was required to instruct the Sector 3B controller to pass traffic information to the crew. The situational awareness of the crew of the B737 assisted in the safe resolution of the incident.

SIGNIFICANT FACTORS

1. The Sector 3B controller cancelled the requirement for the adjacent sector controller to establish aircraft in a 20 NM trail.

2. The Sector 3B controller did not use appropriate separation assurance techniques.

3. The check controller and the Sector 3B controller were slow to react to the reduction in separation between the two aircraft.