Soon after take-off the right engine suffered an under-speed condition and was shut down. The aircraft was returned to Wynyard for a single engine landing.

Maintenance investigation disclosed that the overspeed governor had failed. The governor was removed and sent to the manufacturer for assessment and repair. The manufacturer tested the governor, finding it to be noisy in operation. The high-speed setting was found to be low, the governor was uncontrollable at the balance point and was unable to give an overspeed flow.

When the unit was stripped small pieces of aluminium were found in the solenoid body, along with other non-metallic particles. The manufacturer did not detail the origin of the contaminants.

A series of failures to governors, pitch control units and feathering solenoid valves fitted to this aircraft type has been traced to electrokinetic corrosion and a particular brand of propeller gearbox oil. The operator has changed to a different oil and incorporated a manufacturer's modification designed to gain equal electrostatic potential by improving the bonding between the propeller and gearbox.

The operator advised that these measures appear to have reduced the rate of deterioration of the components.

The instructor completed ten dual instructional circuits with the student pilot whom he assessed as competent for a first solo flight.

The instructor vacated the aircraft and observed the solo circuit from the ground. The take-off, circuit and final approach appeared normal until the flare, which appeared low, and the aircraft touched down earlier than expected. The pilot instinctively raised the nose causing the aircraft to balloon to about 1.5m above the runway.

The nose was then lowered and the aircraft touched down heavily on the nose wheel, bending the nose leg and allowing the propeller tips to strike the runway and destroy the nose wheel fairing. The aircraft settled back on its three wheels then veered left vacating the runway. The pilot shut the engine down and the aircraft stopped with no further damage or injury.

The pilot was completing an approach to runway 10 at the time of the accident. The wind was reported as blowing from 060 degrees at 10-15 kts. At a height of approximately 30 ft the aircraft was observed to roll and yaw to the left of the runway centreline. In what appeared to be an attempted correction by the pilot, the aircraft was observed to roll and yaw to the right. At a height of approximately 15 ft, it was observed to turn back to the left and track, in a nose high attitude and with decreasing airspeed, towards trees to the north of the runway. The aircraft collided with the trees and came to a stop in a nose-down position.

The pilot reported that the atmospheric conditions were turbulent, with a crosswind and some wind shear evident during the approach. He had decided to use only 20 degrees of flap for the landing because of the conditions. At approximately 30 ft the aircraft was affected by a sudden wind gust which caused it to turn left and away from the runway. He tried to correct and applied power to commence a go-around, but the aircraft continued to descend. He retracted the flap in an attempt to improve the aircraft's performance, but this aggravated the situation. He was unable to prevent the collision.

The aircraft departed Griffith for a chemical spraying operation in the Hillston area. A considerable amount of fog and low cloud was encountered enroute, however, the pilot said he had been assured by the farmer at Hillston that the area was clear.

Nearing Hillston the pilot was unable to find a break in the cloud cover, so he elected to track to the east to find an opening but was unsuccessful. Shortly after commencing a return to Griffith the pilot said, he found a large cloud break. He notified his base of his intentions and descended below the cloud base. After passing over a low range of hills he descended to about 300 feet above ground level to continue to remain clear of cloud, but shortly after he was unable to prevent the aircraft from entering lower cloud.

The pilot commenced a slow turn, still able to see the ground immediately below the aircraft. However, he was unable to outclimb rising terrain, despite attempting to dump the chemical load. The aircraft consequently struck the ground and was destroyed, however, the pilot was able to vacate the aircraft without injury.

The pilot reported that when on short final for runway 14, a golf ball passed from left to right, in front of, and higher than the nose of the aircraft.

SAFETY ACTION

The Federal Airports Corporation (FAC) was informed, and the Airport General Manager discussed the occurrence with the local Council. A public park located beneath the approach path to runway 14 was frequently used for golf practice. The Council reacted promptly by prohibiting golf practice in the park and signs were placed to warn the public. FAC Duty Safety Officers were requested to increase patrols of the area to warn off anyone seen playing golf in the area. Subsequently, a golf practice area was established in an area nearby which is clear of the approach path to the runway and meets Civil Aviation Safety Authority regulatory requirements.

VH-ANJ was tracking from over Canberra to Sydney at flight level 150. VH-WGW was tracking outbound from Sydney via Pager, Shelleys and over Canberra, climbing to flight level 140. VH-ANJ was turned right onto a heading of 050, for positioning on a 15-mile final approach for runway 34 at Sydney and cleared to descend to flight level 130. This heading change put the two aircraft on opposing tracks.

To maintain separation, VH-WGW was turned to the right 20 degrees. At that time the two aircraft were nose to nose and 15 miles apart with a closing speed of 450 knots. VH-ANJ was then turned a further 10 degrees to the right, however separation reduced to 3.5 miles laterally and 700 feet vertically as the two aircraft passed.

The minimum separation required was five miles horizontal or 1000 feet vertical.

Significant Factors

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

1. The controller did not take the appropriate action to ensure adequate separation was maintained.

The helicopter was being landed at the completion of a training exercise. The weather was reported as being fine and clear, with little or no wind. During the landing, shortly after making a normal touchdown, the helicopter commenced to shake violently. The transition from normal operation was very rapid and did not allow the instructor time to take any remedial action before control of the helicopter was lost.

The most probable reason for the loss of the aircraft resulted from the rapid onset of ground resonance. This problem is associated with fully articulated rotor systems and is the result of geometric imbalance of the main rotor system. This imbalance of the rotor causes an oscillation which is transmitted throughout the entire helicopter, giving movement from side to side, as well as fore and aft. This action can become violent enough to cause the helicopter to roll over or incur major structural damage. Although not determined in this investigation, the onset of ground resonance can be aggravated by a number of factors, including incorrect landing gear strut inflation pressures, and incorrectly adjusted friction type blade dampers.

The pilot stated that he departed Lismore at approximately 1030 hours for a flight to Evans Head. He carried out two touch and go landings at Evans Head before departing for the return flight to Lismore. At about 1115 when the aircraft was cruising at 1500 feet, the engine lost power and began surging. The pilot said he selected full rich mixture, applied full carburettor heat and gave two strokes on the fuel wobble pump at which time complete engine failure occurred. During this time the aircraft had descended to 1000 feet and the pilot selected a paddock and began an approach at 70 knots.

After flaring slightly to clear 20 metre high trees at the paddock boundary a soft touchdown was made at about 50 knots. The pilot said he had deviated slightly from his chosen path between scattered trees as forward visibility in the aircraft when on the ground is almost nil. Approximately 40 metres after touchdown the right upper wing clipped a tree spinning the aircraft clockwise. The right lower wing and aileron contacted the ground during the rotation. After vacating the aircraft, the pilot noticed flames in the rear of the engine and under the fuselage. The flames were extinguished with water from a nearby cattle trough.

Examination of the engine revealed that the gascolator bowl retaining clip had partially separated allowing the glass sleeve to become dislodged, and this had caused fuel starvation.

The student had returned from the training area, after a solo consolidation exercise, and entered the circuit for runway 24R. He made a normal approach but allowed all three wheels to touchdown together causing the aircraft to bounce back into the air. The pilot applied some power, in an attempt to rectify the situation, and landed the aircraft a second time. The landing was heavy, resulting in structural damage to the nosewheel and causing the propeller to strike the runway. The aircraft finally came to rest with the nosewheel completely separated from the nose undercarriage strut.

It is probable the student's inexperience was the major factor in his misjudgement of the initial approach and in the failure of his recovery action to prevent the heavy landing.

During climb the Boeing B737 crew noticed an un-commanded stabiliser movement. The stabiliser would continue to run on after a command had ceased. The aircraft returned to Melbourne where a normal landing was carried out.

Maintenance investigation determined that the fault was in the stabiliser clutch. The clutch was found to be sticking confirming the crew's observations.

Clutch sticking had previously been recognised by the manufacturer as a problem in B737-400 and 500 aircraft. The manufacturer devised a modification to prevent clutch sticking and an instruction to modify all actuators was notified to the industry via Alert Service Bulletin 737-27A1191 Rev 1 dated 3 November 1994.

On 10 February 1995, the operator acted on the manufacturer's advice, raising an internal engineering instruction EI-737-27-26 to expedite incorporation of the modification into its fleet. The actuator fitted to the incident aircraft was not one of those that had been modified.

The Civil Aviation Authority (now CASA) raised Airworthiness Directive AD/B737/88 on 12 June 1995. The AD was published in CAO Part 105 Amendment 8/95 (August 1995). The AD referenced the manufacturers Alert Service Bulletin and required that all affected actuators fitted to Australian registered aircraft be modified prior to 12 June 1996.

The operator has since amended the EI to conform with the requirements of the AD.

Significant factors

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

1. The stabiliser actuator clutch contained a known fault that allowed the clutch to remain engaged.

2. The clutch had not been modified to eradicate the fault.

3. The clutch stayed engaged after a command was removed.

Safety actions

The following safety actions were taken:

1. The manufacturer raised an Alert Service Bulletin to notify the need to modify the actuators.

2. The operator raised an Engineering Instruction to expedite the incorporation of the modification into its fleet.

3. CASA raised an AD to require all Australian registered B737-400 and 500 aircraft to be modified before 26 June 1996.