Forced/precautionary landing

The aircraft lost power shortly after take-off. A successful forced landing was made in a field adjacent to the strip. An inspection of the aircraft disclosed that a hose directing cooling air to the fuel injector manifold was kinked restricting the amount of cooling air available at the manifold. It is suspected that the manifold overheated and vapourised the fuel causing the loss of power experienced by the pilot.

The aircraft was being ferried from Bankstown to Perth, a journey expected to extend over several days. During the first sector, the pilots became aware of non VMC weather at Wagga and decided to divert to Cootamundra. It was reported that at about the time this decision was taken, they noticed the left fuel tank was not feeding and that fuel was being drawn from the right tank only. Assuming a fuel system malfunction, and a reduced endurance of about 15 minutes, the pilot-in-command decided to carry out a precautionary landing.

A section of gravel road was chosen for a landing site, as nearby paddocks were unsuitable. Although the touchdown was normal, the aircraft began to veer to the right on the heavily cambered road surface. When the pilot was unable to regain directional control, full power was applied for a go round. The aircraft became airborne, still diverging to the right, and collided with a boundary fence before nosing over into an adjacent paddock. The Skyfox CA 22 aircraft has two fuel tanks, one in each wing, which feed into a common collector tank via a two position, on/off fuel selector. Each tank is vented via a port in each fuel cap.

Asymmetric fuel flow from the tanks is known to occur occasionally and one tank is exhausted first, upon which the remaining tank feeds normally. The manufacturer is expected to soon issue an amendment to the Flight manual by which pilots will be warned by a cautionary note of this phenomenon.

The pilot reported that during cruise he noticed fuel flow fluctuations on both digital and analog fuel flow indicators. This was followed by power fluctuations which progressively worsened.

The pilot had decided to carry out a precautionary landing into a clear area he had located, when the engine failed completely. A power off landing was carried out into a small clearing in mountainous terrain approximately 4,000 ft AMSL.

Relevant Factors

• Fuel starvation led to an engine power loss.
• The cause of the fuel starvation was not determined.

The aircraft was engaged in a shooting operation at the time of the accident. Whilst in a shallow descent about 180 feet above scrubby trees, the pilot applied power to fly away. The engine failed to respond and the main rotor RPM reduced. The pilot was forced to land the helicopter amongst the trees. It was reported that the power reduction may have been caused by a faulty fuel control unit.

The pilot stated that he had just refuelled the aircraft. The subsequent engine start and take-off were normal. However, as the helicopter was accelerating through about 60 knots, the engine began to lose power, with decreasing RPM evident. As the pilot lowered the collective pitch control, the engine stopped. The pilot conducted an autorotation on to a road, but touched down in a high nose attitude and broke the right skid.

The engine had operated normally prior to the occurrence. The refuelling operation was the first from a newly opened drum but there was no indication of fuel contamination. Operation of the aircraft requires the fuel boost pump to be ON during take-off and landing and when flying below 140 metres above ground level. The pilot was not certain that he had switched the pump on before take-off. It is possible, therefore, that the engine failed due to fuel starvation.

Barwon Heads Airfield has two strips. The main strip is aligned 350/170 degrees, has a level gravel/grass surface and is approximately 760 metres long. The shorter strip is aligned 080/260 degrees, has a grass surface, is approximately 470 metres long and slopes down to the east. When the aircraft arrived in the circuit area the wind was calm. The pilot intended to land into the north, but he noted that there were several power chutes operating from that strip, so he opted for an approach into the east.

The first approach resulted in a go-around due to a power chute landing into the north. This chute was pulled up just prior to the intersection. The second approach resulted in a touchdown which was later measured to be 73 metres in from the threshold markers. Full flap was used. The pilot reported that the aircraft skipped over a small mound at the intersection of the two strips. Braking then seemed to be ineffective. The aircraft felt as though it was skidding. The pilot applied some rudder correction and checked the brakes and hand brake were both off.

He said that he then decided to go around but delayed power application due to the proximity of a power chute. Power was then applied, and the aircraft became airborne with full flap still selected. It clipped the top strand/strands of a wire fence at the end of the strip. Because the pilot did not know what damage may have been done, he closed the throttle and mixture controls and landed beyond the fence. The aircraft touched down, ran through another fence, entered thick tussocks in a swamp and overturned.

The investigation found that the short grass strip was wet with dew and had an uneven surface due to cracks in the ground and a tufty grass surface. This would have provided a very poor braking surface. In addition, the strip had an increasing down slope, the last third of its length measured as approximately 3% downhill. The pilot reported that he landed on the same strip the previous week in similar conditions and stopped in about two thirds of the strip length.

The pilot reported that the helicopter's engine lost power during normal cruise flight. A forced landing was conducted into small trees resulting in the helicopter catching fire and being destroyed. Later inspection of the wreckage by an aircraft engineer revealed a hole in the crankcase caused by a connecting rod which had separated from the crankshaft.

The aircraft was undergoing a check flight after a 100 hourly inspection. It had not been used for at least 10 months, nor had it been stored correctly. After a number of simulated spray runs across the aerodrome the pilot climbed to conduct an approach to land. On late downwind at 350 ft agl the engine and propeller stopped. The pilot manoeuvred the aircraft towards a clear area but the aircraft landed heavily short of the area. The reason for the engine stopping was not determined.

The pilot gave a 'mayday' call advising that the aircraft had suffered an engine failure, and that he would be carrying out a forced landing. The aircraft was landed in a swampy area between trees which damaged both wings during the landing roll.

The pilot stated that he had not visually checked the fuel contents, or the security of the caps and access covers before departing Darwin as he had filled the right tank before the previous flight.

The fuel gauges did not indicate the expected amount of fuel even after the aircraft was established in cruise, but the pilot elected to continue to his destination.

About 6 km from the destination, with the left hand tank selected, the engine stopped. The pilot switched to the right tank, but the engine did not restart.

It is possible that the right tank was losing fuel from a faulty venting system on the flight into Darwin.

The aircraft had operated a normal scheduled service, arriving in Adelaide early that afternoon. 100 litres of avgas was added to its fuel tank from the airport refuelling facilities for the return flight to Port Augusta.

The aircraft departed with the pilot and five passengers on board, but about five minutes into the flight, climbing through 4000ft, the pilot noticed the left-hand fuel pressure gauge flickering and immediately turned the left fuel boost pump on which momentarily restored the fuel pressure back to normal. Several seconds later the fuel pressure indication dropped below the red line (minimum pressure) and the engine began to surge and lose power.

The pilot commenced a descent and advised air traffic control that the aircraft was returning to Adelaide. His attention was now directed to the right-hand fuel pressure gauge which had also fallen to a low pressure. Turning the boost pump on failed to rectify the problem, and this engine also surged and lost power.

With almost no power available the pilot realised that the distance to Adelaide Airport was too far, so positioned the aircraft for an emergency landing along the coast. He attempted to gain more power by opening the throttles, but this only resulted in erratic surging from both engines with a further decrease in power.

It now appeared that the aircraft would not reach the shoreline, so the pilot shut down both engines and feathered the propellers to extend the glide. When a landing on the beach was assured, he prepared and briefed the passengers for the landing, and to avoid a group of people on the beach delayed extending the landing gear and flaps until the aircraft was clear of their position.

Because of insufficient time for the landing gear to fully extend, the aircraft touched down on the firm sand with the landing gear trailing and skidded for approximately 200 metres along the beach on its belly.

The pilot and passengers were uninjured, and the aircraft received some damage to the rear cabin area lower fuselage skin panels.

The aircraft had been carrying sufficient fuel for the flight, the fuel tank caps were correctly secured, and the fuel tank vents were not blocked. Fuel samples taken from the fuel tanker which had recently refuelled the aircraft showed that the correct type of fuel had been supplied and was not contaminated.

The fuel filters were removed and fuel samples taken from the aircraft for analysis. The filters were found to be blocked by a considerable amount of foreign matter restricting the fuel flow.

Analysis of the fuel samples and sediment indicated that there were no obvious contaminants present which may have been cause for concern.

The particulates present in the samples are always found during testing, being present in the environment and probably introduced during different stages of the fuel handling. The overall amount did not exceed the specification limits.

The particles present in the fuel would not have been responsible for blocking the filters on their own but would have resulted from the combined effort of a large quantity of individual particulates.

All fuel samples met the specification requirements.

This type of aircraft is unique in that it has only one interconnected fuel tank feeding both engines. Each engine has a 5-micron fuel filter, and a fuel vent system which can allow the ingestion of dust into the fuel tank when the aircraft is operated in dusty conditions.

The aircraft often operates through the channel countries of South Australia and Queensland, a lot of the time in dusty conditions. Refuelling is carried out using drum stock when contaminants could easily be introduced into the fuel system.

The rapid blockage of the fuel filters, which occurred after the aircraft departed, was probably the result of the aircraft fuel system being contaminated over a period of time with an accumulation of extremely fine particles which would have been difficult to detect during water drain checks, and settled forming a sediment at the bottom of the tank. These remained relatively undisturbed until fuel was added to the low level of fuel in the tank, stirring the particles into suspension. This may have concentrated the contamination so that the filters, already partially degraded by contaminants, were further degraded quickly to a point when fuel flow to the engines was severely restricted.

The inherent design weakness of the fuel system in this type of aircraft, including the very fine mesh filters which are intolerant to any fuel contamination, is well known amongst operators, including the operator of this aircraft, who over a long period of time have developed successful control systems and methods for minimising the problem. Immediately following this occurrence the operator instigated more stringent controls and instructions to its pilots concerning the fuel system, and improved quality control for refuelling operations, especially from drum stock.