The aircraft was landing on runway 29 centre. After the initial touchdown, the aircraft ballooned and then again touched down firmly in a three point attitude. The nosewheel hub collapsed and the propeller blades struck the runway.

Inspection of the nosewheel indicated it had failed in overload as a result of the firm touchdown.

Following lift-off, at approximately 50 ft AGL, the pilot heard a loud bang and drive to the main rotor was lost. In the subsequent heavy landing, the main rotor struck and severed the tail boom. The aircraft remained upright.

Wreckage examination revealed that, while under power, both main rotor drive belts had rolled off the drive pulleys. It was found that both the forward and intermediate flexplates had also failed. The front flexplate had fractured and separated first, causing the intermediate flexplate to fail when it was free to move forward out of alignment. The main rotor drive shaft assembly, including all broken pieces of the forward and intermediate flexplates, was removed from the wreckage and forwarded for specialist metallurgical examination.

The examination determined that the forward flexplate had failed under load as a result of metal fatigue. The fatigue cracking had initiated at an area of corrosion pitting on the forward edge of the flex plate. Areas of corrosion were also observed under sections of blistered paint at several other sites on the flexplate surface. The edges of the flexplate had been painted with a chromate primer and a protective topcoat. The paint had blistered and formed sites that acted to trap moisture next to the metal. Chlorides contained in the moisture then acted as the electrolytic agent that caused the corrosion.

The investigation was not able to determine the source of the chlorides. However, they could have resulted from environmental factors caused by the helicopter operating in coastal areas or over dry salt lakes. A further possibility was that 'hard' water (containing minerals) from artesian or other sources could have found its way on to the plates.

The maintenance records indicate that with respect to main rotor drive shaft alignment, the helicopter was maintained in accordance with the manufacturer's maintenance procedures.

The maintenance documentation indicated that the failed flexplate (p/n A947-1) had been in service for a total of 3,136 hours. Striations in the surface of the fatigue crack indicated that crack growth had occurred over a period of about 180 flights.

Subsequent to this accident, a flexplate fitted to VH-HBO (BASI report 9303302) failed in similar circumstances. Crack initiation to failure occurred over 350 flights on the flexplate which had been in service for a total time of 1,249 hours. A similar failure occurred in New Zealand. In the New Zealand example, the number of cycles to failure was not determined. However, the total time in service for this component was 1,486 hours. The Bureau recently obtained a flexplate which had been in service for 4,500 hours and which showed no visible evidence of cracking. The manufacturer does not specify a service life for the flexplates.

Significant Factors

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

1. Localised corrosion pitting was created under regions of blistered and lifting paint on the edge of the flexplate.

2. Fatigue cracking had initiated from one area of pitting.

3. The flexplate failed as a result of fatigue cracking.

Safety Action

The safety deficiencies identified in this investigation were found to be similar to those identified in occurrence 9303302.

The Bureau of Air Safety Investigation issued a recommendation, R940092 with Air Safety Occurrence Report 9303302 and the recommendation is detailed in that report.

The pilot had flown from Bankstown to Baradine and return on many occasions in VH-FMB. Prior to departure from Bankstown on the day before the accident, the aircraft's fuel tanks were filled to the maximum capacity of 285 litres. On arrival at Baradine the pilot added 50 litres of motor spirit. The aircraft was parked on the apron at Baradine airport.

The following morning the pilot visually checked the fuel contents but did not use a dip stick. During a water drain check, 5-6 cups of water were taken from the under-fuselage drain point.

The return flight proceeded normally until the aircraft was about 20 kms north of Bankstown airport. The engine then began to run intermittently, followed by a complete loss of power. At this time the fuel gauges indicated that about 1/4 of the fuel capacity in each tank remained. The pilot declared an emergency and conducted a forced landing on cleared land near Winston Hills shopping centre. During the landing roll the nose gear leg was torn from its mounting.

The loss of engine power was determined to be the result of fuel exhaustion. The pilot had calculated the fuel tanks should have contained 100 litres at the time of the power loss. He concluded that about 100 litres of fuel was removed from the aircraft whilst it was parked at Baradine overnight. The aircraft fuel gauges were evidently over reading.

The pilot travelled to his property on a regular basis. As seven inches of rain had fallen in the previous five days, the strip on the pilot's property was unserviceable due to the surface being soft. The pilot decided to land on a nearby strip which had a gravel surface and was not rain affected. This strip was aligned north south.

On arrival overhead the strip, the pilot assessed the wind velocity as westerly at 10 knots and gusty. He positioned the aircraft to land into the north. After touchdown the aircraft was struck by a severe wind gust which caused the aircraft to become airborne, bank to the right and drift to the right off the gravel surface. The aircraft touched down on soft cultivated land and overturned.

VH-WZI entered the Mandatory Traffic Advisory Frequency (MTAF) area with the intention of a straight-in approach. The captain of VH-WZI copied traffic information on two other aircraft from Flight Service and monitored these on the MTAF frequency. At about 4 miles out turning final he copied an aircraft on Flight Service frequency taxiing at Mildura. VH-WZI immediately tried to contact the taxiing aircraft on both the MTAF and the Flight Service frequencies, but without success. Another aircraft in the area confirmed that the taxiing aircraft, a Seneca VH-BJQ, did give a call on the MTAF frequency. It is believed that this call probably occurred as VH-WZI was calling the taxiing VH-BJQ on the Flight Service frequency. The pilot of VH-BJQ is adamant that he called both on the Flight Service frequency and on MTAF before he entered runway 27 to back-track for take-off. After about the third attempt VH-WZI managed to contact VH-BJQ on the Flight Service frequency, by which time he was well down the runway with no chance of exiting before the arrival of VH-WZI. VH-WZI asked the pilot of VH-BJQ to expedite at which time the captain of VH-BJQ was about 100 metres from the take-off threshold and had not fully completed his pre-take-off checks; thus he refused to expedite and suggested that VH-WZI should carry out an orbit.

The captain of VH-WZI considered that the failure of the taxiing aircraft to ascertain the position of VH-WZI before entering the runway was worrying. The captain of VH-BJQ claims that VH-WZI was a long way out when he elected to back-track. Neither the captain of VH-BJQ or his passenger saw VH-WZI until it was turning finals at about 3 or 4 miles out by which time VH-BJQ claims to have been backtracking for about 2 minutes.

Significant Factors

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

1. The pilots of both aircraft had problems communicating with each other.

A simulated engine failure after take-off was initiated by retarding the left engine power lever to flight idle. A pronounced yaw to the left occurred and altitude could not be maintained. The engine did not respond to power lever movement, so the crew initiated feathering action. A successful single engine climb out was accomplished from a very low level and the aircraft was recovered to Essendon Airport.

Significant maintenance had been carried out prior to the incident. Both propellers had been overhauled, and the engine fuel control units were modified. At the completion of the maintenance a successful and uneventful test flight had been carried out.

An extensive investigation involving BASI, the operator, the CAA, the engine manufacturer and the propeller manufacturer, did not find the reason why the engine/propeller combination was not able to be controlled during this routine exercise.

Although some minor discrepancies in engine and propeller control adjustments were noted, these were discounted as having any bearing on the incident.

The aircraft has since been returned to service and is reported to be operating satisfactorily with no repeat of the problem.

The Boeing 737 (VH-TAF) had been cleared to taxi to and hold short of runway 16. Approaching the hold point at runway 16, the pilot switched to Tower frequency and advised that he was ready. The controller replied with 'Good morning'. Mistaking this transmission for 'line up' the pilot proceeded onto the runway. As he taxied across the hold line, he noticed a light aircraft about 2-3 NM on final approach to runway 16 and heard the tower controller clear the aircraft to land. The pilot then asked the controller to confirm that he had been given clearance to lineup. The controller responded in the negative and cleared VH-TAF for an immediate take-off.

The landing clearance of VH-XLA was cancelled and the pilot advised to continue the approach. After VH-TAF became airborne, VH-XLA was cleared to land.

During the landing roll the right landing gear collapsed. The pilot reported that the indication was that the gear was locked down prior to the landing gear collapse.

Prior to this flight the aircraft had undergone maintenance which included some work on the right main landing gear. While damage to the components of the collapsed gear precluded assessment of the downlock switch settings, it is likely that incorrect adjustment of the switch allowed the hydraulic power pack to be switched off before the right main gear was properly down and locked.

As a consequence, it is probable that the aircraft was landed with the right main gear not locked down, although the cockpit indication was that the gear was locked down.

Circumstances

VH-FRI was carrying out airwork at Wagga and was preparing for a practice VOR/DME approach to runway 05. Wagga air traffic control (ATC) were using runway 23 as the runway in use and this was also the runway to which most training aircraft were making their approaches.

At 1235 hours the pilot of VH-FRI requested a runway 05 VOR/DME approach and ATC replied that he could expect a runway 23 VOR/DME approach and wrote this detail on the flight progress strip. The two crew members in VH-FRI did not realise that the controller had issued an expectancy for a different runway to that requested and continued to position their aircraft for an approach to runway 05.

At 1244 hours ATC approved VH-FRI to make a sector entry for a runway 23 VOR/DME approach. Again the crew did not notice that the runway given was not the one requested. The controller passed overshoot instructions to VH-FRI that would keep that aircraft clear of VH-WGX which was approaching Wagga on a flight from Albury and had been instructed to track for a landing on runway 23.

The cloud was five octas at 2,000ft and therefore a visual sighting by ATC was not guaranteed. However the controller had sighted VH-WGX at approximately 5 - 8 NM from the field and he continued to look for VH-FRI in the same direction but nearer to the runway as VH-FRI was sequenced to be first.

At 1259 hours the controller had still not sighted VH-FRI and decided to look in the direction of the runway 05 final approach and saw VH-FRI commencing an overshoot on that runway. He immediately issued new instructions to both aircraft that maintained visual separation standards and a breakdown in separation was averted.

Significant Factors

1. The crew of VH-FRI, having requested runway 05, continued to hear runway 05 even though the controller was saying runway 23.

2. The air traffic controller, having expected a request for runway 23, misheard the pilot request an approach for runway 05 and continued to issue instructions for a runway 23 approach procedure.

The student pilot was conducting solo consolidation flying. While taxiing after a landing on runway 27 the nosewheel assembly collapsed.

An engineering inspection of the nosewheel assembly discovered that a fatigue failure had occurred. A forging which attaches the nosewheel hydraulic actuator to the fuselage broke.

A Civil Aviation Authority Airworthiness Surveyor has inspected the aircraft and intends to have the failed component further inspected in a laboratory.

Significant Factor

The following factor was considered relevant to the development of the accident:

1. A forging failed because of fatigue.