Loss of control

Circumstances:

The aircraft was approaching to land into a 15-knot wind, with a slight crosswind component from the left. At about 60 feet above ground, the wind suddenly dropped completely, probably due to terrain and buildings. As the pilot yawed the nose of the aircraft to the right to line up with the strip the right wing stalled. The aircraft entered an incipient spin and impacted the ground nose first, approximately 100 metres to the right of the strip.

Circumstances:

During take-off, the pilot inadvertently allowed the engine/rotor rpm to decay. By the time he realised his predicament, the main rotor was overpitched and the helicopter slowly settled back towards the ground. With a loss of tail rotor thrust due to the overpitching, the pilot was unable to avoid the body of the helicopter rotating through 270 degrees. During the rotation, the tail rotor and main rotor struck a small tree. The helicopter landed heavily, spreading the landing gear skids.

During a low-level photographic flight, the pilot made a shallow left turn at about 400 ft agl and a low forward speed. When he increased the rate of turn, the helicopter began a rapid turn to the right and the nose pitched up. The rotation continued for 3 to 4 turns during which the nose pitched up and down. The pilot had almost regained control when the helicopter struck the ground heavily on its skids and rolled onto its right side. The cause of the accident could not be conclusively determined but no mechanical defects were detected. The most probable cause was the operation of the helicopter in a mode that induced tail rotor stall and at a height that precluded a safe recovery following loss of control.

Circumstances:

The pilot flew from Berwick to Bendigo as part of his solo navigation training. After resting on the ground for about an hour he decided to carry out circuit training before continuing the navigation exercise. Conditions were turbulent with a southerly wind of about 30 knots. On the first circuit, the aircraft made a normal approach for runway 17 with no apparent drift. However, during the landing flare the pilot experienced a change in wind speed and direction. The aircraft rolled right and drifted to the right side of the sealed runway. The pilot's attempt to correct the situation was unsuccessful and the aircraft landed heavily on the right wheel. The pilot applied full power for a go around, but the aircraft veered further right, and the right landing gear broke off.

Circumstances:

During a landing attempt, the pilot lost directional control of the aircraft. The aircraft entered foliage at the side of the strip.

The pilot, with his wife as passenger, was conducting a bore inspection. A search was instigated when the helicopter did not return by night fall. The wreckage was found the next morning. The helicopter had struck the ground in an inverted attitude amongst trees in a dry swamp. There were no witnesses to the accident. The subsequent investigation concluded that control of the helicopter had been lost at a low height and the helicopter had crashed inverted while the rotor was under positive 'g' flight loads, with little rolling motion. No evidence of pre-accident failure of the helicopter or occupant incapacitation was found. Examination of the wreckage and the surrounding area indicated that the helicopter had struck a tree, by settling into its crown, prior to control being lost. No reason for the descent into the tree could be established. It is probable that, following the tree strike the pilot over-reacted with the collective control and was then unable to regain control of the helicopter in the height available.

The pilot reported that the takeoff was being conducted in a crosswind which he estimated was from the left at 10-15 knots. The surface of the 10 metre wide strip was covered in loose gravel. At the beginning of the takeoff roll, the aircraft began to weathercock to the left. The pilot continued, believing that directional control would improve as aircraft speed increased. However, this did not occur and the aircraft ground-looped, striking an embankment at the edge of the strip. The pilot reported that the aircraft was equipped with a small tailwheel which had limited effectiveness on the soft loose surface. Also, the aircraft was a late model Thruster aircraft which had a greater keel surface than earlier models because of its enclosed fuselage. This was the first time the pilot had operated the aircraft in crosswind conditions. The operating manual for the aircraft indicates a demonstrated crosswind capability of 15 knots. This accident was not the subject of a formal on scene investigation.

The pilot had completed one circuit involving a touch and go landing and a go around from the second approach. Following the third approach the aircraft touched down then veered to the left as it commenced the landing roll. The pilot was able to arrest the left swing as the aircraft reached the left side of the runway but a swing to the right then developed and resulted in a ground loop. The left main landing gear collapsed and the left wing impacted the ground. The investigation revealed that the pilot had used an incorrect crosswind control technique and then failed to maintain directional control during the landing roll. There were no pre-existing defects with the aircraft which could have contributed to the accident.

A truck belonging to the pilot's company became bogged on the Normanton - Dunbar road. It was on its way to Rutland with materials needed at the property before the rain closed the road until the end of the Wet Season. A Carpenteria Shire grader was available to move the truck and two others also bogged. Unfortunately the grader had two flat tyres and no spares were available on site. Because of threatening rain the pilot offered to fly the grader driver to his camp to pick up some serviceable tubes. After locating the camp the pilot selected a stretch of road which after an aerial inspection appeared suitable for landing. Towards the end of the landing roll the aircraft veered left slightly under braking forces and the left wing tip struck a dead sapling not seen by the pilot during the aerial inspection.

Circumstances:

The flight was being conducted for the purpose of obtaining aerial photographs of a hospital located about two kilometres from the heliport. Two passengers were carried, one of whom was a photographer occupying the right seat. The weather was fine and mild, with scattered cloud at 2000 feet. The wind was reported to be south south-easterly at about 10-15 knots. The helicopter was seen to make a large right-hand circuit around the hospital at a height generally estimated to be between 600-1000 feet above the ground. It was then observed to commence a second circuit of the hospital. Whilst on a north-westerly heading, it was reported the aircraft either entered a hover, or slowed to a very low forward speed, for a short period. The nose of the helicopter was then observed to begin yawing to the right. The yaw developed into a series of tight spirals, during which the aircraft drifted in a downwind direction, at a relatively low rate of descent. Witnesses reported seeing the main rotor blades slow down during this phase. At about 50-100 feet above the ground, the helicopter was seen to then descend vertically in a steep, nose low attitude, substantially banked to the left, before impacting heavily in the front garden of an unoccupied house. Almost immediately after impact an intense fire broke out, incinerating the occupants of the helicopter before a rescue attempt could be made. The circumstances of the accident were consistent with a loss of tail rotor effectiveness, leading to an uncommanded yaw and loss of control. The aircraft was operating with a high-power setting at maximum all up weight, at a very low forward speed, out of ground effect. It is considered probable that the groundspeed of the aircraft was less than the tailwind component, resulting in a tendency for the aircraft to yaw to the right, into the relative wind. To counteract this tendency, the pilot would have required considerable left pedal to maintain a constant heading. If, as is considered probable, the aircraft yawed rapidly to the right, very little, if any, additional anti-yaw control would have been available from the pedals. In general, the most appropriate course of action available to the pilot, following an uncommanded yaw to the right, would have been to apply full left pedal to counteract the yaw and to apply forward cyclic control to increase airspeed and translational lift. A reduction of collective pitch could also have been used to assist in regaining directional control but may have resulted in an excessive rate of descent.

Significant Factors:

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

1. High gross weight combined with high required power.

2. Flight below translational speed, out of ground effect.

3. Tailwind component.

4. Uncommanded yaw due to loss of tail rotor effectiveness.

5. Following a loss of control, the pilot encountered conditions beyond his level of experience.