Loss of control

The aircraft had been operating for two hours without any apparent problems. Shortly after lift off, following a refuelling stop, the pilot was unable to maintain directional control and the aircraft began yawing rapidly to the right. The pilot attempted to land the aircraft in a clear area, however, one skid dug in and the aircraft rolled over. A fractured tail rotor drive shaft intermediate flexplate was the only mechanical defect found during the investigation. The specialist engineering investigation established that the flexplate failure was caused by the main rotor blades contacting an external object. The only main rotor strike evident at the accident site occurred when the aircraft rolled over following the landing. Damage to the tail rotor control rods indicated that full left peddle had been applied at the time of the flexplate failure. Aircraft weight, power requirements, wind conditions and take-off and DEPARTURE techniques were not conducive to loss of tail rotor effectiveness, however, loss of tail rotor effectiveness will cause the aircraft to yaw to the right. The reason for the initial yaw was not determined. The aircraft rolled over when the pilot was forced to make an emergency landing on unsuitable terrain whilst he was attempting to recover from a difficult control situation.

After six dual check circuits the pilot commenced his second solo flight from the 18 strip. The surface wind was 150`/15 knots. At about five feet above the ground on the first landing the aircraft started veering to the left. The pilot commenced an overshoot but the left wing dropped and the aircraft continued to veer left. The throttle was closed but the pilot was unable to prevent the aircraft running off the strip into the trees. This accident was not the subject of an on-site investigation.

Circumstances:

Neither pilot had landed at Porepunkah before. They obtained details of the strip which was at an elevation of 935 ft and had an average downslope of 1.25 percent to the north. There were trees just beyond the southern end of the strip. Because of the trees the landing distance available to the north was 740 m whereas to the south 840 m were available. Accordingly, it was recommended to land to the south in light northerly wind conditions. On arrival over the strip the pilot noted the wind was a light northerly. He therefore elected to land to the south. On the first approach the pilot found he was too high on final and made a go-around. A second approach was made with full flap selected. After touchdown, the aircraft floated and touched down again three or four times. By this stage, the aircraft was some two thirds of the way along the strip and power was applied for go-around. The aircraft swung 30 degrees left with the left wing low. Alarmed because he thought the left wing would hit the ground, the pilot closed the throttle. After touching down firmly, the aircraft ran off the side of the strip, went through two fences, then over a road, finally colliding with a tree before coming to a stop.

Significant Factors:

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

1. The pilot was inexperienced in landing on sloping strips and in downwind conditions.

2. The pilot did not initiate a timely go-around when the aircraft continued to bounce along the strip.

3. The pilot lost directional control on the attempted go-around.

Circumstances:

The pilot reported that he had flown to the destination area but was experiencing difficulty in locating the strip. He located an area that he thought might be the strip and carried out an inspection from a low height with full flap selected. About halfway along the paddock the pilot decided that the area was not the strip he was looking for and applied power to climb and retracted the flaps. The aircraft stalled and struck the ground in a nose down attitude.

Significant Factors:

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

1. The pilot made an improper decision to conduct the inspection using full flap.

2. He did not maintain adequate airspeed.

3. He retracted the flaps prematurely during the go around. This accident was not the subject of an on-scene investigation.

Circumstances:

As the aircraft was making an approach into a confined area, it was struck by a local wind condition known as "willy willy". The aircraft began to rotate in a clockwise direction, and the pilot was unable to obtain a response from any of the controls. The aircraft touched down heavily, causing damage to the right hand skid and the tail rotor.

Significant Factors:

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

1. The pilot lost control of the helicopter when it was affected by a "willy willy".
2. The aircraft collided with the ground before the pilot was able to regain control.

The pilot had flown that morning from Bringelly to Kincumber to visit his brother and family. The flight was reported as normal and the helicopter as serviceable. Following lunch the pilot agreed to take his nephew for a ride "to wave a cheerio to friends at Wamberal". After takeoff he climbed to 1200 feet and set heading over Empire Bay. When he had passed Terrigal he descended quickly to 200 feet, and then flew north along the beach towards Spoon Bay. He observed that the sea was very rough, with large waves breaking on the headland and a strong southerly wind blowing. When he arrived over the headland, abeam Wamberal, the pilot initiated a turn to the right away from the land, and commenced to climb using cyclic control. His intention was to gain sufficient height during the turn so as to recross the coast and a built up area. The pilot increased the angle of bank to approximately 40 degrees, which he maintained during the climbing turn, allowing the airspeed to decrease to best climb speed. When the helicopter had climbed about 50 feet and turned through 120 degrees the pilot increased the collective pitch and power to continue the climb. He reported that the machine then appeared to buck and tend to corkscrew, without any accompanying unusual noises. It then lurched violently to the right and assumed a steep nose down attitude. There was no apparent response from application of left pedal which made the pilot believe that he had suffered a tail rotor failure. He lowered the collective control and pulled back on the cyclic in an attempt to raise the nose, which slowly came up and the lurching stopped. The helicopter was now facing towards the land, but too low and not close enough for the pilot to make an auto-rotational landing on the beach. The helicopter descended rapidly, and the pilot moved the cyclic control full back in an attempt to flare the machine for a ditching in the sea. At the same time he raised the collective and applied some power. The helicopter touched down relatively gently on the water, but sank almost immediately. Both occupants were able to evacuate through the cabin bubble and stayed together for about half an hour. When help did not appear to be forthcoming, the pilot, who was the stronger swimmer, decided to to swim against the current and surf to the shore to find help. After assuring himself that his nephew was alright, and floating satisfactorily, he set off for the beach, where he was assisted by police and other people who had witnessed the accident. An immediate air search by helicopters failed to locate the passenger in the sea. His body was eventually washed up on the shore about a week later. Attempts to locate and salvage the wreckage of the helicopter were unsuccessful, except for the recovery of the tail rotor and part of the tail boom. An inspection found no evidence that these components had suffered any pre-impact malfunction or failure. As the helicopter was in a steep turn to the right the pilot may have failed to recognise and then compensate, by applying left pedal, for the yaw, also to the right, which would have occurred as he increased the collective pitch. It is likely that he did not apply left pedal until the roll was well developed. Recovery should have been possible by rolling the helicopter level with cyclic and balancing with the pedals. When the pilot decreased the collective pitch, torque to the main rotor was reduced, slowing the yawing motion. As he was still applying full left pedal the tail rotor would have now taken effect, slowing or stopping the turn just prior to the helicopter entering the sea. The wind would have been creating a considerable amount of turbulence over the headland, but not enough to cause loss of control. Mechanical and/or tail rotor failure was considered unlikely. Without the tail rotor anti-torque effect the fuselage should have rotated at a fast rate to the right, and still been rotating at impact, even with the collective lever lowered. This accident was not the subject of a formal on-scene investigation.

The helicopter was carrying 360 litres of water based Herbicide and about 90 litres of fuel when it took off the second time that morning. Flying activity had commenced later than planned due to local fog and low cloud in the area to be sprayed. A level area on the bank of the creek was used for loading and the pilot availed himself of the open space over the creek to accelerate before commencing a climb out to the treatment area. This technique involved an immediate loss of ground effect as the helicopter moved off the elevated creek bank. The aircraft failed to achieve translational flight and the pilot "sensed" a power loss as it descended towards the fast flowing creek. The left skid fractured when it struck a log protruding from a low island. The impact rotated the helicopter through 180 degrees causing the pilot to lose sight of the only reasonable landing area on the opposite bank. The helicopter settled and balanced on sloping ground whilst the engine wound down due to fuel starvation caused by a fuel feed line separation in the initial impact. As the rotor system slowed down, the helicopter fell onto its damaged left side. The pilot was using a pad that was not suitable for the operation. The pad was limited by a fence line at one side which was high enough to prevent operations over it at high all up weights and a creek at the other side which caused an immediate loss of ground effect as soon as the helicopter moved off the pad. Trees and high terrain prevented other take-off options. The pilot was using the potential energy of pad height above the creek to gain airspeed quickly and early translational flight. On this occasion he did not obtain translational flight and the helicopter descended into the creek. The pilot overpitched the main rotor blades causing a loss of RPM and power. The engine and fuel components were examined in detail and no mechanical reason for a power loss was discovered. The helicopter was fitted with a spray system that was not authorised for the type in Australia, the performance combination of helicopter and spray system was unknown.

The pilot had arranged to take some friends for a flight and to have a flight check with a flying instructor beforehand. Initially the instructor was unhappy with the pilot's circuit planning and landings. The pilot was given some information on the aircraft and a circuit diagram and another check was scheduled for the following day. On the next day the instructor gave the pilot a substantial briefing prior to the flight. The pilot's flying had improved significantly and the instructor assessed him as competent to fly the aircraft. After a scenic flight in the local area the aircraft joined the circuit on right downwind for runway 12. Surface wind at the time was 120` at 15 knots. The aircraft was observed to touchdown aligned with the centreline, near the runway threshold, and a short time later was seen to bank left. It touched down on the grass within the left hand side flight strip heading about 40` to the left of the runway direction. At around this time the pilot elected to go-around and he applied full power. From this point the aircraft made a gentle left turn until it was tracking 330`. Initial impact with the ground occurred when the aircraft was descending at an angle of approximately 15` and banked at least 30` to the left. Indicated airspeed at this time was 35 knots. The aircraft landed heavily on the nosegear and rolled backwards before coming to rest 20 metres from the point of initial impact.

The pilot was herding a bull along a shallow valley and he decided to hover behind it. He entered the hover about 20 feet above the trees from a slight descent and with some right lateral movement. The heading of the helicopter was westerly in a wind from the south at 10 knots. The pilot then initiated a pedal turn into wind. The helicopter stopped turning when nearly into wind and the pilot added almost full left pedal to complete the turn. The helicopter then began to rotate smoothly and rapidly to the right, and the pilot applied full left pedal in an attempt to stop the yaw. As the application of full left pedal had no effect, the pilot closed the throttle but there was no perceptible reduction in the rate of turn. The helicopter rotated through at least 360 degrees before striking the trees and crashing on its side. The on site investigation did not reveal any mechanical defects or anomalies that would have contributed to the loss of tail rotor control.

At about 50 knots during the landing roll, the pilot discovered that the right wheel brake had failed. The aircraft had swerved to the left when both brakes had been applied. With the rudder control ineffective at low speed, the pilot intentionally ground looped the aircraft to avoid running into the perimeter drainage ditch. The right main gear collapsed and the right wing was damaged as a result of the ground loop. Examination of the right brake unit revealed that the master cylinder was corroded internally, allowing brake fluid to bypass the seal.