Loss of control

Circumstances:

A night take-off was initiated from runway 21. The runway was wet, with patches of standing water on the surface. Light rain was falling, with a south-easterly surface wind of 10 to 15 knots. The crosswind component was close to the maximum specified for this type of aircraft. Just prior to reaching rotation airspeed the left mainwheel apparently entered a pool of standing water, and the pilot reported that at the same time the aircraft was subjected to a strong wind gust. The aircraft swung to the left and the pilot was unable to maintain directional control. The pilot thought that the aircraft may have commenced to aquaplane, and he closed the throttle immediately. There was no attempt made to apply brakes. The aircraft departed the runway to the left, crossed the grass flight strip, and continued for approximately 85 metres, before colliding with a levee bank and coming to rest in a drainage ditch. No evidence of aquaplaning was subsequently found. This accident was not the subject of an on-scene investigation.

Significant Factors:

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

1. Patches of standing water on the runway which were not visible to the pilot.
2. Loss of directional control following penetration of standing water and/or sudden wind gust.
3. The pilot did not apply braking in an attempt to slow the aircraft prior to the collision with a ditch.

The helicopter was lifting an industrial straddle platform from the top of a large, 300 foot high, cooling tower at an electric power station. As the helicopter took up the load, the sling-rope snagged on a small lug on the right landing gear skid. The 420 kilogram load, hanging from the right skid, caused the helicopter to bank rapidly to the right. During this rapid bank, one end of a 2 metre long plastic pipe, held by the crewman at the right rear doorway, contacted 3 of the main rotor blades. Within less than 5 seconds the rope unsnagged from the skid with a sudden jolt as the load positioned itself at the full extension of the rope beneath the cargo hook. Simultaneously the pilot regained a level attitude but found that the helicopter was already descending slowly, under control, within the approximately 30 metre wide opening of the top of the cooling tower. Because the pilot feared that the "jolt" had been possible damage sustained by the helicopter, he continued the descent gently towards the inside base of the cooling tower. A few metres above the base, the pilot jettisoned the load which subsequently damaged the inside of the tower. After jettisoning the load, the pilot landed the helicopter lightly on its skids inside the tower. The crewman got out and inspected the helicopter as best he could as the pilot kept the engine running. As no damage was seen the pilot carefully flew the helicopter out of the tower and landed nearby as the crewman proceeded out on foot. There was nowhere inside the tower for the helicopter to safely shut down. The sling rope had been lightly attached to the skid before the flight by availing of a loop in the rope and one wrap of adhesive tape. The intention of lightly attaching the rope to the skid was to avoid the possibility of the rope being accidently caught on the rear protrusion of the skid during the lift. During the hook-up of the load, the helicopter encountered some turbulence which caused the helicopter to move forward of the desired hover position. During this forward movement, the thick rope slid aft along the right skid and a core strand of the rope snagged on a small lug which meant that the pilot could not jettison the load. At the time, the crewman was restrained at the right rear doorway. His task was to give manoeuvring directions to the pilot and to attach a hook on the far end of the sling rope to the load with a length of plastic pipe. The 420 kilogram load hanging from the right skid placed the helicopter outside the lateral centre of gravity limits for pilot control. Just as the helicopter banked rapidly right, the straddle platform lifted clear of the tower long enough for the helicopter, with the load still dangling from the right skid, to move into the stack opening where a slow descent commenced in a slight downdraft. During the preflight planning, the pilot and the crewman did not consider it possible for the thick rope to snag on either of the 2 small lugs which are designed for the attachment of ground handling wheels. The use of the adhesive tape held the rope close enough to the top surface of the skid for the rope to come into close proximity with the lugs.

Circumstances:

On the flight to Bathurst Harbour immediately prior to the accident the pilot-in-command occupied the left pilot seat, and the co-pilot occupied the right pilot seat. Shortly after take-off on that flight the pilot-in-command handed over control of the aircraft to the co-pilot who was very experienced on tailwheel aircraft. The co-pilot landed the aircraft at Bathurst Harbour without any problem. After a short time sightseeing the party boarded the aircraft for DEPARTURE. The copilot was again handling the controls. Taxiing and the initial take-off run appeared normal but when the tail was raised the aircraft swung to the left. The take-off was discontinued but directional control was not regained. The aircraft left the strip and came to rest in a peat bog a short distance further on. After the accident, the co-pilot's rudder pedals were found to be in the stowed position which disconnects them from the rudder control system. It was not determined when the pedals were put in the stowed position, but it was determined that the co-pilot had not been briefed on the rudder pedal stow system.

Significant Factors:

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

1 Inadequate preflight inspection carried out.

2 The co-pilot was not briefed on the rudder pedal stow system.

3 Take-off was attempted with the rudder pedals stowed. 4 Loss of directional control on take-off.

Circumstances:

The pilot was commencing a practice flight in preparation for a 600-kilometre soaring competition task. The weather was fine with a north-easterly wind of 15-20 knots and a temperature of approximately 40 degrees Celsius. Following line-up, the pilot was delayed for approximately fifteen minutes before his aero-tow became available. He then advised the tug pilot that a climb speed of 65 knots was acceptable. The subsequent tow initially appeared normal although observers at the airfield noticed some apparent roll instability. At approximately 1000 feet above ground level (agl) the tug pilot detected thermal activity and began a left orbit to regain the area of lift. With the turn almost completed the right wing was violently "kicked-up" as the aircraft re-entered the area of lift. The tug pilot corrected the upset checked that the glider was not affected and continued the left turn. Approximately five seconds after the upset at about 1300-1500 feet agl the glider released. Observers reported that the glider had banked steeply to the right while apparently still under tow. Following the tow release the angle of bank increased past the vertical the nose dropped steeply, and the glider entered a spiral dive from which it did not recover. It struck the ground in an almost vertical nose-down attitude. The investigation was unable to find evidence of any pre-existing structural or system defect. Pilot medical evidence is inconclusive. The reason the aircraft entered an abnormal flight manoeuvre at an altitude from which recovery should have been possible could not be determined.

Significant Factors:

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

1. Control of the aircraft was lost following tow release. The cause of the loss of control was not able to be determined.

Circumstances:

The pilot was conducting mustering operations at low level at the time of the accident. Shortly after the aircraft made a low pass to indicate the position of some animals, it was observed descending at a steep angle. The aircraft commenced rolling to the right just prior to ground impact and was destroyed by a post-impact fire. All essential aircraft systems appeared capable of normal operation prior to the accident. There was no evidence that the pilot had suffered any pre-impact illness or sudden incapacitation. Although all of the precise factors leading to this accident could not be determined, the sequence of events is similar to many other accidents investigated by the Bureau, where the loss of control at low level following a low pass has been due to inattention to aircraft operations by the pilot. It was disclosed during the investigation that although the pilot had a valid mustering endorsement, he had not received any training in recovery from stall/spin conditions, typical of a loss of control in a Cessna 150, at low level.

Significant Factors:

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

1. It is probable that the pilot did not pay sufficient attention to the operation of the aircraft during low-level mustering operations.

2. The aircraft probably stalled and entered an incipient spin.

3. The loss of control occurred at too low an altitude for any recovery attempt to be successful.

Recommendations:

This type of loss of control is a factor in many of the low-level accidents investigated by the Bureau. Training and exposure in incipient loss of control situations, particularly in Cessna 150 type aircraft, is not included in all mustering and associated low flying endorsement programs. The Civil Aviation Authority in Western Australia advised all local pilots of the desirability of obtaining this type of training. It is recommended that the Civil Aviation Authority extend this advice to all pilots in Australia who have approval to conduct fixed wing operations at low level.

The pilot intended to position a beacon on the roof of the Perth Control Tower. The task was to be accomplished by sling loading the beacon, which weighed 199 kilograms, below the helicopter. The aircraft was positioned about 40 metres to the north and about 25 feet above the tower. The pilot carried out an approach to the roof and hurriedly deposited the load. The load was then released from the sling, which was left attached to the helicopter. The aircraft was then manoeuvred across the roof with the sling being dragged over the surface. The hook on the sling became snagged on the tower guard rail and halted the helicopter's progress away from the tower and causing it to pitch nose down and roll to the right. With the cable being tensioned by the pull of the helicopter the hook freed itself from the railing and the sudden relaxation of the load on the cable caused it to spring towards the helicopter. The cable flew up around the tail boom and became entangled in one of the main rotor blades. The other main rotor blade severed the tail boom which fell free of the helicopter striking the side of the tower on its way to the ground. The major section of the helicopter then fell to the ground at the base of the tower, caught fire and was burnt out. The tower roof was 90 metres above the ground and the baseplate, onto which the beacon was to be positioned, was triangular in shape with sides of about 60 centimetres long. Specialist opinion was that such a task would be difficult even under ideal conditions but there is evidence that a wind shear was present at about 300 feet at the time of the accident. The pilot's licence was not endorsed for sling loading operations and he was not sufficiently current on the aircraft type, considering its handling characteristics and suitability for sling operations, to undertake such a job. The ground crew were inadequately briefed about the job and their duties, and an inappropriate communication system between the ground crew and the pilot was used. The electric quick release for the lifting hook fitted to the helicopter was unserviceable although the alternate manual system was checked and found to be working. The pilot had recently been retrenched from his permanent employment and had not found other work. It is likely therefore, that he was excessively motivated to complete the task even though he was experiencing difficulty in accurately controlling the helicopter.

It was the student's fourth flying lesson and the effects of power were being revised. The student turned the aircraft 90 degrees to the left onto downwind but when he attempted to level the wings after the turn, the bank angle increased from about 30 to 50 degrees. The instructor took over the controls and attempted to recover by applying right aileron, full power and holding the nose up briefly. When the aircraft did not immediately recover, the instructor lowered the nose but the aircraft struck the ground, in a left wing, nose low attitude, before full control could be regained. After revising the effects of power, the engine speed was set too low for the aircraft to sustain a level turn. The student maintained altitude by progressively applying up elevator and the instructor did not notice the incorrect setting because speed was assessed with reference to the ground in a 20 knot tailwind. The instructor delayed taking over the controls, because he thought that the aircraft was being subjected to mechanical turbulence generated by trees, over which they had flown.

The pilot was conducting cattle mustering operations. Weather conditions at the time were very hot, with a 10 to 15 knot wind. The pilot advised that while flying downwind at 30 knots and 80 feet above the ground, he commenced a pedal turn to the right. After some 90 degrees the turn suddenly stopped and the aircraft sank rapidly to about 35 feet above the ground. The main and tail rotors struck trees, but the pilot was able to maintain control and fly the helicopter to a clear area, where a safe landing was made. No defect was found with the helicopter or its systems which may have contributed to the occurrence and the reason for the loss of control, reported by the pilot, was not determined. This accident was not the subject of an on-site investigation.

The aircraft had been parked in the open and was exposed to a heavy frost. The pilot and his son attempted to clear ice accumulations from the top surfaces of the aerofoils by throwing warm water over them. Some 20-25 minutes elasped between the ice clearing operation and the takeoff attempt, during which time the aircraft was taxied to the airstrip and a second passenger emplaned. No further checks were made for new accumulations of ice. Following lift off, the aircraft commenced an uncommanded turn to the right. By the use of full left aileron and left rudder, the pilot was able to regain some directional control, but could not prevent the aircraft from striking boulders on the side of the strip. During the subsequent ground slide, the fuel system was broached and the aircraft was destroyed in the resulting fire. Post crash inspection of the aircraft revealed that the rudder had been fouling the elevator control, thereby preventing adequate control travel, for continued flight under the existing conditions.

The aircraft had been engaged in mustering cattle in flat, open country. The pilot elected to land near a utility to obtain further instructions from stockmen in the vehicle. Approaching the vehicle, the aircraft suddenly commenced to vibrate severely and to lose height. The pilot was unable to avoid a collision with the utility, following which the aircraft struck the ground heavily and overturned. No fault was subsequently found with the helicopter which might have contributed to the development of the accident. The symptoms described by the pilot suggested that the vibration experienced was associated with a main rotor blade tracking problem. It was likely that while manoeuvring to reduce speed prior to landing, the aircraft was placed in a position where the lead and lag action of the rotor blades temporarily exceeded the capacity of the blade dampers. Because of the low height above the ground at which this occurred, there was insufficient time or height in which the pilot could effect recovery.