The pilot was conducting a familiarisation flight in the local area. After conducting a series of circuits and landings, he departed on a short cross-country flight. Shortly after levelling off in the cruise at about 2200 ft AGL, the pilot heard a muffled bang, followed by a severe shudder through the airframe. The engine then stopped. The pilot immediately transmitted a Mayday call and then proceeded to conduct a forced landing on to a newly ploughed field. During the landing roll, the nose wheel broke through the loose soft surface and the aircraft nosed over.

The pilot was able to exit the aircraft unaided, suffering only minor injuries to his neck and back.

Later examination of the engine found that the engine crankshaft had failed.

FACTUAL INFORMATION

The Boeing 737 had landed on runway 35 and commenced taxiing back to the terminal.  There was a requirement to cross that runway again in order to reach the terminal. After being instructed to hold short of runway 35, the crew were subsequently given a clearance to cross and to hold short of runway 30.  The crew replied to this instruction with the aircraft callsign only, consistent with the requirements of AIP OPS CTL paragraph 15.1 to 15.3 and OPS CTL paragraph 25 - note 1 and 3.

At this time, the crew turned on the navigation and landing lights in accordance with their company Standard Operating Procedures (SOPS) and crossed runway 35.

A Cessna 152 was on final approach for runway 30 and was cleared for a touch-and-go.

After crossing runway 35, the crew of the Boeing confirmed between themselves that they were cleared to cross runway 30 and, in doing so, left the navigation and landing lights on as they proceeded to cross this runway.

Before entering the runway strip, they checked both approaches.  The co-pilot looked to the right while the pilot in command looked to the left, the direction from which the Cessna was approaching.  At this time, the Cessna was in the final stage of its approach.  The pilot-in-command did not see the Cessna. As the two aircraft were transmitting on different frequencies, the crew of the Boeing did not hear the landing clearance given to the pilot of the Cessna.

As the Cessna was touching down the Surface Movement Controller (SMC) and the Aerodrome Controller (ADC) observed the Boeing infringe the flight strip of runway 30.  The crew of the Boeing were instructed to hold position by the SMC while the ADC instructed the pilot of the Cessna to stop immediately.

The Cessna stopped at the intersection of runway 35 and 30. The Boeing stopped within the flight strip of runway 30.  The distance between the two aircraft was 525 metres.  The crew of the Boeing were then cleared to cross runway 30, after which, the pilot of the Cessna was given a clearance to take off.

Analysis of the Automatic Voice Recorder (AVR) tape confirmed that the SMC had, in fact, issued the instruction to hold short of runway 30. The tape also indicates that, at the same time the instruction was given to hold short of runway 30, there was a transmission from another station which was not discernible. The over-transmission made it difficult to clearly hear this part of the clearance. The crew of the Boeing were sure, however, that they heard a clearance to cross both runways.  It has been common in the past for such a clearance to be given at Canberra.

The weather at the time of the incident, as described by the Automatic Terminal Information Service (ATIS), indicated light and variable winds with a visibility of more than 10 kms in haze.

ANALYSIS

As it was not uncommon to receive a clearance to cross both runways at Canberra, the crew of the Boeing appeared to have the expectation of such a clearance in this incident.  Even though the transmission from another station may have made it difficult for the Boeing crew to clearly hear the instruction to hold short of runway 30, this expectation appears to have overridden any possible ambiguity the crew may have had about the clearance instruction.  As the crew were sure they had heard the instruction to cross both runways, it was not necessary for them to clarify these instructions.

The acknowledgement of the clearance instruction with the aircraft callsign indicated an understanding of that instruction. ATC would not, therefore, have been alerted to the misunderstanding.

At the time the pilot-in-command scanned the final approach area to runway 30, shortly before the Boeing commenced crossing that runway, the Cessna may have been difficult to sight. At that time, it is likely that the Cessna was below the line of hills to the south-east of the aerodrome.  The haze that existed at the time of the incident would have affected the visibility and may have increased the difficulty in sighting the Cessna.

CONCLUSIONS

Findings

1. The SMC issued the Boeing with a clearance instruction to cross runway 35 but to hold short of runway 30.
2. The instruction to hold short of runway 30 was over transmitted by another station.
3. The crew did not check or confirm the unclear instruction.
4. The crew acknowledged the instruction with the aircraft callsign only.  Such an acknowledgement indicated to SMC that the crew understood the instruction to hold short of runway 30.
5. As the crew of the Boeing was transmitting on a different frequency to the pilot of the Cessna, they did not hear the landing clearance that was given to the Cessna.
6. The pilot in command did not see the Cessna on its final approach to runway 30.

Significant Factors

1. The crew appeared to have had an expectation to be issued with a clearance instruction to cross both runways.
2. The acknowledgement of the instruction with the callsign only did not alert ATC to the misunderstanding.
3. The Cessna may have been difficult to see on its approach path due to a line of hills to the south-east of the aerodrome.
4. The visibility at the time of the incident was affected by haze.

The aircraft was spraying thistles when the accident occurred. There were several areas to be treated on the property. The first area had been completed, and the pilot was flying the first swarth run on the next area when the aircraft hit a double wire powerline which culminated in a severe impact with the ground.

The investigation revealed that the pilot had been given a map of the property by the property owner. The map had two powerlines depicted but did not show the powerline that the aircraft hit. The span was reported to be about 450 metres, and the poles were remote from the point of impact. Prior to commencement of spraying the pilot made an aerial inspection of the area for powerlines and other hazards. He did not identify the powerline that the property owner had neglected to mark on the map.

Significant Factors

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

1. The pilot was not made aware of the existence of the powerline that he hit, and he did not see it during his aerial inspection of the property before commencement of spraying.

2. The span of powerline that the aircraft hit was about 450 metres and the poles were remote from the impact point, thus denying the pilot cues as to its existence.

The pilot stated that, when the aircraft was about 900 ft above the ground on approach to the runway, the engine began to lose power. She then commenced engine failure checks. The electric fuel pump was turned on, the throttle, pitch and mixture levers were moved fully forward and the circuit breakers, master switch and magnetos were checked. As there was no response from the engine the pilot then changed from the right to left fuel tank, then subsequently back to the right. The engine still did not respond, and a forced landing was made in a cane field.

All six occupants evacuated the aircraft and were not injured.

The pilot later said that the left fuel gauge read one quarter, and the right gauge read three quarters full.

Post flight inspection found the left fuel tank empty, but the right tank had sufficient fuel for continued flight. The inspection also determined that both fuel tank gauges were misreading and that no fuel calibration card was available in the aircraft.

The pilot's management of the fuel system was not in accordance with the Aircraft's Pilot's Operating Manual which indicates that the fuel should be managed in such a way as to balance the aircraft laterally or handling/trim penalties would result. However, the pilot operated from the left tank for almost the entire flight. There had been approximately two hours of fuel in each tank at the commencement of the flight with a flight plan indicating a requirement for a little under two hours of fuel.

Correct operating procedures for changing tanks also require the change to be made at the selector before the electric fuel boost pump is switched on, in order to prevent air entering the fuel line to the engine. It is probably a co-incidence that the switching took place as air from the empty left tank entered the line. This would have had the effect of totally confusing the pilot who diagnosed a fault with the half full right tank and switched back to the empty left tank. Once the fuel feed line to the engine contains air, it takes a considerable time for it to be purged by fuel under pressure from the electric boost pump. The pilot did not have this time available when the engine lost power at 900ft altitude.

The sector 12 controller was responsible for ensuring separation was maintained between the two aircraft. ZK-NZY was tracking direct from over Sydney to Melbourne and this track took it close to over Canberra. VH-EWI was proceeding via over Cooma and Canberra to Sydney. Both were cruising at flight level 280. It was necessary to retain either 1000 feet of vertical separation or five miles horizontal separation.

The controller considered the option of vectoring in the vicinity of Canberra to ensure separation was maintained. However, she assessed that the lateral separation of five miles would be retained without the need for this. In spite of this assessment the horizontal distance between the two aircraft reduced to 4.5 miles.

Significant Factors

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

1 The controller did not take positive action to ensure that the minimum required separation was maintained.

The pilot was conducting a bore inspection at a height of approximately 300 ft above ground level at the time of the occurrence. He had just flown over the No. 7 bore when the engine started to run roughly. The pilot completed a magneto function check which did not disclose any problems. He decided to turn the ignition switch off and then back on to make the engine backfire in an attempt to clean any lead off the spark plugs. When the pilot attempted to turn the switch back on, instead of the key turning in the ignition, the whole ignition box turned in the dash, leaving the key in the off position. The pilot applied additional pressure to the key and the whole switch became detached and fell inside the dash as the key came out in his hand. He attempted, briefly, to correct the problem, then realising that he was going to have to land the pilot transferred his attention to the emergency landing.

The pilot aimed the aircraft between two trees knowing that the wings would be damaged, but hoping the fuselage would be safe. The aircraft went between the trees then skidded for about 10 metres before the propeller dug into the ground and it flipped over onto its back.

The aircraft had flown approximately 95 hours since its last periodic servicing and there had been no indications that the ignition switch mountings were faulty during that period. The reason for the rough running was not determined.

The pilot of VH-UBM called Wagga Tower inbound at 45 miles on the 065 radial of the Wagga VOR, at 8000 feet. He was instructed to maintain 8000 feet and track inbound on the 075 radial. The assigned track was to ensure separation was maintained with VH-SBA, which was tracking outbound on the 053 radial, initially at 7000 feet.

Once VH-SBA had passed the lateral separation point for the two tracks, at 10 miles from Wagga, the aircraft was cleared to climb above the level of VH-UBM. Although separation was arranged by procedural means by Wagga Tower, VH-UBM was observed on radar by Melbourne air traffic control crossing the 050 radial from south to north. A loss of procedural separation occurred due to VH-UBM being off track to the north of the 075 radial.

The pilot of VH-UBM made an error in mentally orientating himself with respect to the Wagga VOR and turned right instead of left. In retrospect he was uncertain of how this occurred.

Significant Factors

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

1. The pilot made an error in orientating himself with respect to the Wagga VOR.

2. The precise reason for this happening was not determined.

After the aircraft suffered a power loss at 1000 feet AGL, the pilot commenced an autorotational descent. The aircraft was flared above trees and the aircraft fell into a clearing.

A post flight inspection by the pilot found that the fuel system was contaminated by water. He had refuelled out of a 200-litre drum on the previous night and had omitted to carry out preflight fuel drains.

The pilot reported that while on approach to a three foot hover, he commenced a right turn to position the aircraft for refuelling. As he did so an unsecured object in the cockpit shifted, preventing movement of the cyclic control to the left. The pilot tried to recover the situation by increasing altitude, but the aircraft continued to roll right until the main rotor blades hit the ground. The aircraft was then thrown back onto its skids after which it rolled onto its left side.

VH-HYG departed Melbourne (ML) for Perth (PH) tracking ML - Yarrowee (YWE) - Q23 - CRENA cleared to climb to flight level (FL) 350. At approximately 20 nm from ML, VH-HYG was recleared direct to CRENA. VH-HYG contacted the Inner West (IW) radar controller 30 nm outbound from ML.

VH-HYA contacted the IW controller 120 nm inbound to ML, tracking from Mount Gambier (MTG) direct ADAMS - ML on descent to FL 210.

The controller was aware of the potential conflict with the tracks and the traffic disposition. He determined that both aircraft would pass with at least six miles separation and, in his judgement, would also have established vertical separation.

When the aircraft were approximately 10 nm apart (nose to nose) the outbound aircraft, VH-HYG, appeared to turn approximately 10 degrees to the right, towards the track of VH-HYA. The controller observed this but assessed that both aircraft would still pass abeam each other with minimum allowable lateral separation of five miles.

Both aircraft entered an area of potential separation conflict at approximately 60 nm from ML. Lateral separation reduced to 3.5 nm with no vertical separation.

The controller had used his experience to assess current/future positions of both aircraft but had failed to alter his plans to ensure separation after VH-HYG altered track. At the time of the loss of separation, the controller did not pass traffic information to either aircraft because of lack of time and because from the 3.5 miles nearest proximity the aircraft tracks began to diverge.

Significant Factors

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

1. The controller failed to alter his plans to ensure separation standards were not infringed after VH-HYG turned approximately 10 degrees towards the track of VH-HYA.

SAFETY ACTION

Since this incident, the CAA has reminded all inner sector controllers of the importance of:

1. Separation assurance; specifically, that profile separation is not separation assurance.

2. Radar technique and the action required when using minimum radar separation.