Loss of control

Whilst returning from an aerial agriculture task, the Chief Pilot for the company elected to conduct some low flying over a lake. During this exercise, he misjudged his height, and the wheels contacted the water. The pilot lost control of the aircraft and it tipped over and came to rest inverted in the water. The pilot escaped without injury.

The aircraft was to carry out insecticide spraying operations at a rice farm. The pilot made an approach to the airstrip from the south, with a tail wind of about 3 kts. The pilot said that, shortly after touchdown, he observed cattle straying near the edge of the strip and elected to go-around. As the aircraft became airborne the right main landing gear struck an adjacent levee bank. The impact detached the gear leg which then struck the right horizontal stabilizer, detaching the elevator. The pilot said that, by remaining in ground effect, he was able to complete a right circuit and land the aircraft back on the strip. On touchdown, directional control was lost and the aircraft ground looped, colliding with large water pipes and associated equipment.

The pilot was landing the aircraft on a strip beside a paddock of barley. The right wing tip became entangled in the barley causing the aircraft to ground loop.

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.

The helicopter had been used for mustering throughout the day and had been refuelled from drums.

When the mustering was completed the last 15 litres from a partly used drum was pumped into the auxiliary fuel tank of the helicopter. Fuel samples were taken from the main tank and filter and the helicopter flown to nearby stockyards.

After a short time on the ground, the helicopter departed for the station homestead, about 37 km away. Approximately 10-15 minutes after refuelling, while cruising at 200-250 feet above ground level, the engine began to run roughly, and the rotor RPM began to decay. The pilot lowered the collective control and the engine stopped.

The helicopter was flying downwind in a 20-30 knot wind and the pilot was committed to a downwind autorotational landing. Touchdown was at 20-30 knots on rough ground made heavy by recent rains. The skids dug in and the helicopter nosed over and was substantially damaged. The pilot was uninjured and walked to the homestead for assistance.

Subsequent inspection by recovery personnel revealed water and dirt in the fuel filters.

The aircraft was engaged in aerial mustering operations. Whilst landing to disembark the passenger the pilot experienced intermittent cyclic control problems. He then took off again and during the next 5 to 10 minutes of cattle mustering he tested the cyclic control, but response was normal. A short time later, as the helicopter approached touchdown to re-embark the passenger, all cyclic control was lost. To avoid hitting the waiting passenger the pilot applied power to go around but was unable to control the helicopter's flight path and it impacted the ground nose first.

Inspection of the wreckage revealed that the cyclic control column had fractured at the location of the electrical wiring access hole near the base of the column. The fracture was caused by fatigue crack growth. The access hole had been elongated by mechanical filing and the fatigue origins were located at these abrasion damage sites.

Safety Action

The following interim recommendation was sent to the Civil Aviation Authority on 22 June 1993:

IR930094

That the Civil Aviation Authority advise all operators of this failure and mandate an inspection of the cyclic control column electrical loom access hole to ensure control column integrity.

The CAA in response issued AD/HU-269/102 on 2 August 1993.

Subsequently, results of finite element stress analysis of the failed cyclic pitch control column indicated that material yielding, at the lower electrical loom access hole, occurs below the design limit load. Evaluation of this cyclic control column design is being considered by the Civil Aviation Authority in consultation with the Federal Aviation Administration and the aircraft manufacturer.

During the landing roll the right wheel brake failed to function. The pilot was unable to maintain directional control, resulting in a ground loop, during which slight damage to the left landing gear strut and right wingtip occurred.

Air in the right brake line rendered the right brake ineffective. It was not determined how the air was admitted to the system as no maintenance had been performed on the system since the aircraft had been delivered from the factory.

The pilot inspected part of strip 17 and found it to be dry and firm. He took off on sealed strip 08. Later he landed on 17. Near the end of the landing roll the main wheels sank in a softer area and the aircraft overturned. This happened in an area the pilot had not checked on his inspection.

At about 400 feet on climb after take-off the engine began to run roughly and lose power. The pilot was forced to attempt a landing in a cane field. During the landing one wing struck the cane and the aircraft nosed over coming to rest inverted.

Inspection of the aircraft found that the internal timing of the magneto was incorrect and that the magneto was also in a poor state of repair. In addition, the spark plugs were of different types and in varying condition. It was the opinion of the maintenance engineers who inspected the ignition system that the loss of power was a result of the overall condition of the system.

The pilot had commenced a take-off from a low hover when the helicopter nosed up sharply. He lowered the collective pitch lever and opened the throttle, suspecting over-pitching as the cause. The helicopter struck the ground in a slightly nose low attitude with the right hand skid while moving forwards and to the right. The skid separated and the helicopter cartwheeled forwards before coming to rest on its right side.

A bellcrank from the cyclic control system of the helicopter was found fractured after the accident. Metallurgical analysis of the part found that the failure was caused by impact forces experienced during the accident sequence.

The reason for the loss of pitch control was not determined.