The aircraft was being flown on the final phase of the student's multi-engine endorsement training. A general handling period was completed before arriving at Camden to carry out normal and asymmetric circuit procedures.

The instructor pilot reported that the first approach was normal, but the aircraft touched down firmly on the mainwheels, followed by a firm touchdown on the nosewheel. A touch-and-go was carried out and the landing gear retracted normally after take-off. On downwind, during the next circuit, the landing gear extended normally with three green landing gear locked indications. The nose gear was also confirmed to be extended, using the mirror on the right engine nacelle. Both pilots again confirmed three greens during the turn onto final. The touchdown was smooth, but the nose gear collapsed, and the aircraft slid to a halt on its nose.

The repair agency later reported that the nose gear downlock was found out of rig to the extent that the hydraulic pump continued cycling with the gear down. It is probable that this condition allowed the nose gear to unlock when it took the weight of the aircraft during landing.

Witnesses reported seeing the helicopter land in the corner of a fenced paddock. A short time later the helicopter took off again but after climbing to about three metres above the ground, it began rotating and gyrating erratically, contacting the ground a number of times. It came to rest in an upright position but with the tail boom severed and damage to the main rotor assembly and gear box.

The pilot reported that he had recently recovered from a viral complaint which was characterised by severe coughing bouts but had been free of these symptoms for a few weeks. As he flew over the area of the accident, however, he had experienced the incipient stages of a coughing fit, so he landed the helicopter, shut the engine down, and walked around for a short time until the symptoms disappeared. He then reboarded the helicopter to continue the flight but shortly after lift-off was overcome by a severe coughing fit. This caused him to partially lose control of the helicopter, and it contacted either the fence or the ground.

The take-off was rejected when the left engine torque indication was noted to be 13% below target torque. The subsequent investigation found that a fuel control unit drive shaft seal failure had allowed fuel to wash the lubrication from the shaft bearings which then failed. The drive shaft and spacer were badly worn and had caused a restriction to the governor flyweights which had signalled the lower torque during take-off.

Circumstances

The helicopter had just lifted off and was about 30 feet above the ground when the pilot noticed that main rotor RPM was beginning to decay. He reduced collective pitch, but the helicopter lost height as the engine power slowly decreased towards flight idle.

Height could not be maintained with the power available, so the pilot had no option but to perform a downwind run-on landing onto rough terrain. The tail rotor struck the ground, and the tail boom was damaged by the main rotor blades. The engine was still running at reduced RPM when the helicopter came to rest.

Investigation revealed significant contamination in the airframe and engine fuel filters. The filters were not completely clogged, and the material was mainly of a sandy nature. Some of the material found in the filter bowls was probably displaced from the filter surface during the rough landing.

Engine components, including the fuel control unit, power turbine governor, fuel nozzle, PC air filter and all pipes and hoses were inspected by an approved overhaul facility.

Some of these components showed signs of wear sufficient to require overhaul before being returned to service but no fault could be found that would have definitely caused the power loss.

During the investigation it was found that the fuel supply hose became discoloured after being in contact with jet fuel for only a short period of time. Samples of the hose (both new and used) were sent for laboratory testing which revealed that the rubber compound used was not fuel proof, although it was rated for use with jet fuel.

Neither the partial filter clogging, the effects of wear in the engine fuel supply components nor the dissolved material from the faulty hose, individually, could explain the power loss. A combination of these factors at a time of high-power demand may have been sufficient to cause the loss of power.

Safety action

The Civil Aviation Safety Authority is aware of the information relating to the degradation of the interior of the fuel hose assembly and has taken it up with the hose manufacturer.

When the pilot selected the landing gear down in the circuit area the gear down light failed to illuminate. He recycled the landing gear then carried out the emergency extension procedures, but without success. The aircraft was fitted with a mirror and the pilot was able to observe that although the main landing gear appeared to be down and locked, the nose landing gear had not extended.

The pilot decided to divert to Gove and advised Adelaide Flight Service of his intentions. He requested that Emergency Services be made available.

On arrival in the circuit area the pilot discussed the problem with company engineers, then over a period of about 30 minutes made several unsuccessful attempts to extend the nose landing gear.

When the Emergency Services were in place, the pilot made an approach to runway 13. He shut down the engine on short finals, landed on the main wheels and held the nose up as long as possible. As the airspeed decreased, the nose dropped and slid along the runway, damaging the propeller and nose cowls.

Subsequent investigation revealed that the nose gear doors were jamming and had trapped the nose landing gear in the up position. The aircraft had suffered a landing gear collapse during a take-off run some months previously and had only been flown a few hours in the two months since the repair. The nose landing gear doors had been causing extension problems during that time which had not been correctly rectified.

After selecting the landing gear down the pilot reported that the hydraulic pump motor made an unusual sound for about 20 seconds, then stopped. He attempted to pump the gear down manually but was unable to obtain a safe indication although all landing gear legs appeared to be in the down position.

Because of failing light, he decided to land as soon as possible, and when flares had been arranged made an approach for runway 10. During the landing roll the pilot applied heavy braking which was evident due to scuffing and a flat on the right main wheel tyre tread. This caused the right main gear leg, which had not locked down, to rotate rearward around the hinge point and collapse. The aircraft slewed to the right, coming to rest in a shallow ditch alongside the runway.

A corrosion hole was found in the left main gear door hydraulic line which had allowed hydraulic fluid to escape overboard.

The helicopter was engaged in a search and rescue (SAR) training exercise over the sea at night, in visual meteorological conditions. The task was to drop two small, improvised marker buoys from the helicopter in flight and for the pilot to record the latitude and longitude of the buoys by using the global positioning system (GPS) fitted to the helicopter. Small boats were tasked to search for the buoys.

As planned, the helicopter crewman dropped the two marker buoys through the left rear passenger window while the pilot flew at 100 feet radar altitude above the sea with about 15 knots forward airspeed. As soon as the buoys were released the pilot directed his attention to the GPS to obtain a fix. Then, just as the pilot raised the collective lever to climb, with the helicopter moving forward at about 15 knots, its landing skids, fitted with emergency popout floats, contacted the water and the helicopter nosed into the sea. The four persons on board, none of whom was wearing a life vest, were rescued within 20 minutes. There was no life raft in the helicopter. The helicopter was swamped before the pilot had a chance to inflate the emergency floats.

The radar altimeter had been set for its warning light to illuminate at or below 100 feet above terrain or water. The pilot confirmed the operational serviceability of the radar altimeter (RADALT) enroute to the buoy drop site which was two kilometres out to sea. During the buoy drop and the position fix, the helicopter was facing towards land where the pilot could see lights. While fixing the GPS position of the buoys, the pilot was unaware that the helicopter was descending.

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

1. The pilot channelised his attention to the GPS while flying at a low height at night.

2. The pilot was not aware that the RADALT warning light had illuminated.

3. The visual cues available to the pilot were insufficient to enable him to monitor the height of the helicopter above the water.

The pilot was taking some friends on joy flights. She obtained permission to use a glider parked and ready to fly. Although she had not flown the type before she had flown a type considered to be almost identical. She was also briefed on the altimeter setting procedures in use by the club but was permitted to use her preferred method.

On the first aero-tow the glider released at 4200ft, some 3000ft above the field elevation. This was in accordance with advice received during the pre-flight briefing. No difficulty was encountered with height control during that flight. The second aerotow was terminated at 3200ft, only 2000ft above field elevation. In the latter stages of that flight the aircraft was very low near the landing area. However, the flight was continued in accordance with a standard circuit.

When turning on to the final, the aircraft was just above the trees. Speed brakes were deployed, and the right wingtip struck a tree. The aircraft collided with the ground in a steep nose-down attitude and came to rest inverted. Witnesses assisted in evacuating the occupants.

The gliding community had recently changed altimeter setting procedures from setting zero altitude on the ground (QFE) to setting airfield elevation (QNH). This should have presented no problems to new pilots who would be trained in the new method, but it could present problems to experienced pilots familiar with the old system. This pilot expressed a dislike for the new procedure, saying that it required additional calculations to be made. She was permitted to use whatever system she desired.

For this flight she had set the rear altimeter (she was in the rear seat) using QFE and the front altimeter to QNH. As a result, she should have been quite familiar with the readings on her altimeter and been able to correlate those readings with the external appearance of aircraft height.

Some confusion evidently developed during the flight, leading her to become confused as to the significance of the readings from the altimeter. The result was that the aircraft was much lower in the circuit area than she expected and she did not detect the low height from observation outside the aircraft.

The operation of speed brakes on final approach appears to have been a reflex action which was inappropriate under the circumstances.

It is likely that the whole sequence was initiated when the pilot released from the tow about 1000ft lower than on the previous flight. This was probably unintentional and due to misinterpretation of the altitudes indicated on the altimeters. The false perceptions initiated at that time remained with her for the duration of the flight.

Significant Factors

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

1. The pilot was not familiar with the altimeter setting procedures to be used.
2. The glider was released from the tow about 1000ft lower than intended.
3. The pilot relied upon altimeter readings rather than external reference for height close to the ground.
4. The pilot mis-handled the speed brake on final approach.

The pilot had been briefed on a number of treatment areas some days earlier. When he approached this area, he did not see the powerline. At the end of the first spray run he flew into the wire. The helicopter developed a vibration, and the pilot landed as soon as possible.

Inspection found that one main rotor and one tail rotor blade was damaged and required replacement.

He had been advised of the presence of the wire during the earlier briefing.

During a cattle muster along a laneway, the pilot positioned the helicopter to head off a beast which broke away from the mob. As he descended in front of and to one side of the beast, he felt a sudden vibration through the helicopter and at the same time noticed an overhead powerline.

He lowered the collective for an immediate landing. The landing which followed was heavy, spreading and breaking the skid gear. The helicopter then rolled onto its side. Post flight inspection by the pilot revealed that the tail rotor had struck the wire.

The powerline was a single wire earth return line strung about 35 ft above ground. The span was reported to be 800 m long. The wire was struck some 100 m from the nearest pole which was partially hidden among foliage.