After conducting 15 joy flights from the Geelong helipad from about 1145, the pilot flew two passengers on an advertising project. One of the passengers, a local radio announcer, was tasked to perform a live radio cross from the helicopter.

On the commencement of the last approach to land to the south-east, the pilot estimated the wind to be 15 kts from the north-west. He advised that when on short final, 200 metres from the helipad, he noticed a sudden wind shift and the helicopter experienced loss of lift. He increased throttle and collective in an attempt to maintain height and reach the helipad. However, rotor RPM decayed and the helicopter settled into the sea 60 metres short of the helipad.

Subsequent viewing of amateur video footage showed the latter part of the landing approach to be very shallow, followed by a classic example of overpitching with the main rotor disc coning and the RPM audio decreasing as the helicopter descended into the sea.

No fault was reported with the airframe or engine which may have contributed to the accident.

FACTUAL INFORMATION

A Cessna 550 aircraft had departed Wagga on a training flight to Canberra and was maintaining flight level (FL) 170.

A Saab SF340B aircraft had departed Sydney on a regular public transport flight to Albury and was maintaining FL 120 on the route section between Canberra and Albury. Both aircraft were under radar control.

At 1218 ESuT, the crew of the C550 requested descent and were cleared to FL 130 by air traffic control. The pilot read back FL 120 but this incorrect level was not detected by the controller. One minute later the controller informed the crew of the C550 that there would be a delay for further descent due to crossing traffic (the SF340B) on the Canberra to Albury track.

At 1222, the controller noticed that the radar return for the C550 was indicating FL 120 and was 3 NM from the SF340B on crossing tracks. There was a breakdown of separation.

Radar analysis indicated that at the time vertical separation broke down, the C550 had passed through the intended track of the SF340B by approximately 1 NM and that the closest point between the aircraft was 3 NM. The required separation standard was 5 NM horizontally or 1,000 ft vertically.

ANALYSIS

Air traffic control

Because the controller believed he had heard the crew of the C550 read back FL 130 he annotated this on the flight progress strip. This meant that, in his mind, he had provided separation for the conflict he was expecting to occur. He then monitored the aircraft as they passed in the belief that vertical separation would be maintained until he could re-establish radar separation. It was only when he observed on radar that the C550 was maintaining FL 120 that he realised that a breakdown in separation had occurred. At that time, the aircraft had already passed each other, and separation was increasing.

Flight crew of the C550

The crew thought they heard FL 120 given as the descent instruction and when this read back was not questioned, they continued a normal descent to FL 120, believing it to be the assigned level. They did not see the other aircraft and considered that, as air traffic control were providing separation, any instructions to the other aircraft would not have been queried, even if they indicated a climb through the level of the C550.

SIGNIFICANT FACTORS

1. The crew of the C550 read back an incorrect assigned flight level.

2. The air traffic controller did not detect the incorrect read back.

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.