The separation standard was compromised between two international flights on crossing air routes. UAL862 was flying north-east along A579 at FL290 when the crew asked for clearance to climb to FL310 to avoid turbulence. This request was granted at 1255 and the aircraft climbed to the new level. Its calculated time at position RUSUM was 1312.

`ANZ39 was flying north-west along A464 at FL310. Its calculated time at RUSUM was 1311. The controller did not realise the confliction until 1309, and she immediately issued a descent to UAL862 which was relayed through the International HF Net manned by Flight Service. The aircraft did not respond to SELCAL. At 1312 an instruction to climb to FL330 was issued to ANZ39 via the HF link. The crew of ANZ39 reported that they had another aircraft displayed on their TCAS 14 to 15 nm south-east and at the same level.

The separation standard of 15 minutes was breached at 1256 when UAL862 climbed to FL310.

The Sector 8 controller had no direct communications with aircraft under her control. All air traffic instructions were relayed through Flight Service International on HF. The controller had approximately 6 to 8 aircraft under control in the sector. For reasons not established, the crew of UAL862 did not answer SELCAL.

The New Zealand Air Traffic Controllers were on strike and international aircraft were directed on nonstandard tracks. This added to the complexity of the operating position where lateral separation points had to be calculated for each situation.

Both aircraft crews were aware of the other aircraft due to the TCAS fitment in each aircraft.

The nose landing gear failed to extend when the gear was selected down for landing at Weipa. Several unsuccessful attempts were then made to extend the gear using the manual emergency extension. Later the nose landing gear collapsed during the landing roll when the pilot was forced to land with the nose gear in the unlocked position. All five persons on board were able to exit the aircraft safely. The aircraft sustained damage to both propellers and the forward underside of the aircraft in the incident.

After departing from Bankstown, the pilot of the Turbo Commander was instructed to climb to 5000 ft. At the same time a Boeing 767 was being vectored for a right downwind for runway 16R, on descent to 6000 ft. As the B767 approached that altitude the Departures (S) controller noticed that the Turbo Commander had climbed above 5000 ft and was approaching 6000 ft. The Turbo Commander was immediately turned right but lateral separation between the aircraft reduced to about 2 NM. The required separation standard was 3 NM lateral or 1000 ft vertical.

The pilot of the Turbo Commander later reported that he thought he had been cleared to 6000 ft, but may have confused the altitude clearance with a heading change to 160 degrees given at the same time.

After departing Sydney, the SAAB 340B was being radar vectored to intercept the 297 radial whilst maintaining 5,000 ft. The BAE146 was on a right circuit for runway 16R, and had been assigned 6,000 ft. The departures radar controller subsequently noticed the altitude readout of the BAE146 indicating 5,500 ft and passed traffic information to the SAAB. The BAE146 was then observed to climb back to its assigned altitude.

An examination of recorded radar data indicated that the BAE146 had descended to 5,600 ft. As a result, vertical separation between the aircraft was reduced to 600 ft, with a horizontal separation of 1.4 NM. The required minimum separation standard was either 1,000ft vertically, or 3 NM horizontally.

The captain of the BAE146 subsequently reported that the first officer was the handling pilot and was under training at the time of the incident. He had observed the aircraft to descend below the assigned altitude and informed the handling pilot of the error. The aircraft was then climbed back to its assigned altitude.

The crew of VH-KDO were given a runway 16 Strathbogie standard instrument departure (SID) and were told to maintain 3000 feet. After take-off they were cleared to climb to 4000 feet.

Shortly afterwards, the air traffic controller noticed the transponder mode C altitude readout increase to above 4000 feet. When the crew were queried on the altitude deviation they promptly descended back to 4000 feet. However, a loss of separation occurred with VH-JQF, an Airwork aircraft, tracking in an easterly direction to the south of Melbourne and maintaining 5000 feet.

Significant Factors

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

1 The crew of VH-KDO did not maintain the assigned altitude of 4000 feet.

The pilot was conducting a noxious plant inspection and contour flying about 50 ft above hilly terrain at an indicated airspeed of 20kts to 25 kts.

The helicopter struck a single powerline which slide up the bubble and contacted the flying controls before breaking. Although cyclic control was partially lost, the pilot was able to land the helicopter without further incident.

The powerline had a span of approximately 200 metres between supporting poles and was difficult to detect from the air.

When the pilot selected the landing gear down for landing it failed to extend, and the circuit breaker (CB) popped. He reset it, but each time the gear was selected down it popped again.

He decided to return to Broken Hill because of the emergency services availability. On arrival he attempted to extend the gear manually, but he could not turn the handle. He was now committed to a wheels up landing.

An inspection revealed that the "up" limit microswitch attachment bracket had broken, preventing the lever arm making contact with the microswitch. This allowed the gearbox motor to continue running when the landing gear was selected up after take-off. The motor then ran the gearbox pinion and segment gears to the end of their travel, forcing and jamming their teeth together. When the gear was selected down the motor was unable to move the pinion gear and stalled, causing the CB to pop.

The jammed pinion and segment gears also prevented the manual extension handle being turned.

FACTUAL INFORMATION

Sequence of events

The pilot was conducting a visual flight rules scenic flight. These flights were done on a regular basis by the operator and the pilot had flown the DH-82 type on many of these. Commonly, the route flown was from Jandakot to the Fremantle area, north to about Mullaloo Point, then Observation City, Perth City and back to Jandakot. The pilot occupied the rear cockpit seat and the passenger the front cockpit seat. Shortly after passing the Fremantle Golf Course, at an altitude of 1,000 ft, the engine misfired and commenced to vibrate badly. The pilot transmitted a Mayday call to the Perth Radar Advisory Service (RAS). At this stage, the indicated altitude was 900 feet.

The pilot told the RAS controller that he had a partial power failure and said he was going to put the aircraft down in an area near Leeuwin Barracks, on the bank of the Swan River. The pilot was aware of the general details and location of the selected area. He tracked for a left base, while losing altitude, intending to land towards the west. The aircraft was halfway through the turn onto final, at a height of about 300 feet and with everything proceeding as planned, when the pilot suddenly saw a set of high-voltage power lines across his track. A large transmission-line tower for these lines was also now directly in front of him.

The pilot decided to complete a 270-300 degree right turn over the water to avoid the tower and pass under the wires and still land in the selected area. It was a tight, gliding turn and when passing through a heading of about east, at a height of about 150 feet, the aircraft stalled and started to spiral right. The pilot applied left rudder but was unable to prevent the aircraft from diving into the river at a steep angle. After impact, the aircraft floated vertically with the tail out of the water and both cockpits under water. The pilot found himself out of his cockpit swimming on the surface, but the passenger was still in the front cockpit.

Shortly afterwards, assistance arrived, and the passenger was released from his seat by a water-police diver. Both pilot and passenger were then conveyed to hospital.

Wreckage examination

Inspection of the engine showed that the number one connecting rod had failed. Approximately half the rod, including the big end attachment to the crankshaft, was missing. Inspection of the remaining fracture surfaces showed that the fracture was caused by fatigue crack growth. The crack had propagated along the centre of the connecting rod 'I' beam from the region of the connecting rod/crankshaft bearing housing. The reason for the initiation of the fatigue cracking could not be determined, due to the absence of pieces crucial to the investigation. The other three connecting rods were inspected but no cracks were found in any of these. The investigation was unable to trace the history of the failed connecting rod.

Each shoulder harness was attached to a transverse cable which in turn was attached, via a bracket at each end, to the aircraft structure. One of the attachment brackets for the rear seat shoulder harness had failed, with the bolt pulling out of (tearing) the bracket. The rear seat lap strap also failed. This probably happened because the seat moved during the impact sequence and the strap was cut by the metal edge of the seat. Even with the failures the rear seat harness absorbed considerable impact energy before failing although, the pilot did receive some facial injuries. One of the front seat shoulder harness attachment brackets, which was attached by three bolts, sustained a partial failure when two of the bolt heads separated. The harness however, remained intact.

The aircraft was equipped with leading edge slats on the upper wing. These devices have the facility to be locked closed. When unlocked, they open up when the aircraft approaches stalling speed. The slats have the effect of slightly reducing the stall speed and also provide a warning to the pilot that the aircraft is close to the stall. The flight manual for the aircraft included a statement that slat extension provides acceptable visual warning of approaching stall.

There were two placards in the cockpit that stated that the slats were unserviceable and not to be operated. Also, the operator's handling notes for the type included instructions that the slats were not to be used for take-off or landing. The slats were locked closed.

Weather data

The surface wind at Jandakot on departure was from the south-west at about 12 knots.

Forced Landing Options

The power loss occurred over a built-up area. There were very few forced landing areas available within gliding range. The Fremantle Golf Course, which was behind the aircraft when the engine malfunction occurred, was probably one option. Another was the area, near Leeuwin Barracks selected by the pilot. This latter area was aligned approximately east-west and had a set of high-tension power lines across the eastern end, aligned approximately north-south. The pilot was not previously aware of the power lines. The power lines and associated tower were not particularly obvious when looking down on them from above, and the restricted visibility from the rear cockpit of the DH-82A was another inhibiting factor.

ANALYSIS

The major reason for the accident was the engine malfunction which forced the pilot to attempt an emergency landing in a built-up area. The location of the engine malfunction meant that the pilot's options were limited. His choices were the golf course, which by then was behind the aircraft and out of sight, or the Leeuwin Barracks area.

To use the golf course the pilot had to execute a 180-degree turn. To reach the Leeuwin Barracks area the pilot only had to make a right turn of about 90 degrees. As a result, he opted for the site near the Leeuwin Barracks.

The pilot was satisfied all was going well until late in the approach when he suddenly saw the power lines and tower. This late sighting caused him to rapidly change his plans and attempt to avoid them. The aircraft was in a poor position, at a height of about 300 feet, for the pilot to attempt a large turn. However, this appeared his only option. During this attempted turn through 270-300 degrees, the pilot allowed the airspeed to reduce to stalling speed and he lost control of the aircraft. There was insufficient altitude to recover control before impact.

The fact that the slats were unserviceable and locked closed possibly deprived the pilot of an important stall warning indication. Had they been available and unlocked, they may have assisted in preventing the loss of control.

SIGNIFICANT FACTORS

The following factors were considered relevant to the accident:

1. Fatigue cracking of the engine's number one connecting rod caused it to fail. The factors which led to the fatigue crack could not be determined.
2. The failure of the connecting rod caused significant vibration and loss of power. These led to a forced landing.
3. There was a lack of suitable landing areas.
4. The pilot did not detect a power line and its associated tower until very late in the approach.
5. The pilot's attempt to avoid the power line led to a significant loss of airspeed.
6. The loss of airspeed led to a stall followed by loss of control at a height that was too low to effect recovery before impact.
7. The unserviceable slats may have been a factor in the pilot's failure to recognise the impending stall in time to prevent loss of control.

The pilot flew the aircraft with an instructor on the day before the accident flight. The instructor said that the pilot had not flown recently, and the pilot had not previously flown a Beechcraft Debonair. The next day the pilot proceeded to Caloundra with two passengers as planned. Witnesses at Caloundra airport saw the aircraft approaching to land. The aircraft was very high over the runway, and when it was obvious a landing could not be accomplished, the pilot carried out a go-around. The aircraft was seen making a second approach which was also very high, but not as high as the first. The pilot continued the approach, and the aircraft was seen to flare high and fast. The aircraft then landed nosewheel first and "wheelbarrowed" along the runway. The witnesses said it appeared that the engine had not been throttled back, as the aircraft did not slow down until it ran off the end of the runway into soft ground causing the nose gear to collapse.

The pilot was contacted and said that he had submitted a report, however, no report has been received. A check with the operator and the insurance loss assessor revealed that they had not received a report.

FACTUAL INFORMATION

Following a normal climb, the pilot dropped two parachutists over Hamilton Island. A power-off descent to circuit height followed. The pilot did not select Carburettor Heat during the descent. When on a long final approach, the pilot attempted to arrest a high descent rate with the use of engine power. The engine failed to respond. The pilot found that the aircraft was outside gliding range of the runway and he decided to ditch the aircraft in shallow water. Engine trouble checks failed to restore power to the engine.

The aircraft was ditched in shallow water and after a successful escape from the cabin, the pilot was picked up by an island launch.

The aircraft's engine was transported to a maintenance facility at Archerfield where it was examined. The engine was extensively corroded by salt water. No fault was found as far as could be determined.

The Bureau of Meteorology data showed that the relative humidity at ground level was 65%. The Carburettor icing - probability chart showed that serious icing at descent power was to be expected at such a humidity level.

ANALYSIS

Although there are other possible reasons for the power loss, it is most likely that the engine failed to produce power due to carburettor icing.