Forced/precautionary landing

The pilot stated that the helicopter was given a full daily inspection. The engine had full oil and there was approximately 55 litres of fuel on board. After start, the engine was kept at idle until oil temperature was about 75 degrees. the rotors were then engaged and warm up was continued at 2000 RPM and then 2500 RPM. The magneto check showed no rough running. After pre-take-off checks, the helicopter was brought to the hover and moved forward about 6 feet, then put back on the ground for about 3 minutes while a load was placed on board. The pilot stated that after checking that all nozzles were working and pre-take-off checks were complete, he brought the helicopter to the hover. At 3200 RPM the manifold pressure was 26 inches. Transition to forward flight was normal, and height and speed began to increase. At about 60 to 70 feet agl and about 40 knots the engine note changed, and the pilot noticed RPM had reduced to about 2700. The pilot lowered the collective and wound on full throttle. A landing straight ahead was carried out with some forward speed, and during the landing the main rotor struck the tail boom and severed it. The helicopter was fitted with an NARCO 10 Emergency Locator Transmitter, which did not activate during the heavy landing.

Subsequent examination of the engine failed to reveal any defect, but engineering opinion was that the engine malfunction was most likely due to a sticking valve.

The pilot reported that he was conducting sheep spotting operations at 500 ft above ground level when the engine suddenly lost power. He was forced to complete an emergency landing in rough terrain, damaging the aircraft in the process.

The pilot had refuelled the aircraft to full tanks and conducted a water drain test 45 minutes flying time prior to the power loss.

The carburettor was removed, tested and inspected. On the test bench, the carburettor flooded each time it was tested. The inspection disclosed some faults that probably led to the flooding. The float level had been incorrectly set, there was significant wear in the float attachment pin and the floats had been making contact with the carburettor body and the head of the needle valve had been repaired using silver solder. Additional tests also indicated that it was possible for the needle valve to jam in the closed position, starving the carburettor of fuel. The head of the needle valve was badly worn. This permitted it to become jammed in a corresponding wear mark on the carburettor body. Other faults, such as the use of locking wire instead of a split pin to secure the float pin and disintegration of the accelerator pump leather plunger were also evident.

An inspection of the aircraft logbooks indicated that the carburettor float level had been adjusted by a LAME 12 flying hours prior to the power loss. Float adjustment requires the carburettor to be opened. Some of the faults, which the inspection indicated had been present for a considerable time, should have been apparent during the adjustment. They were not corrected.

It is probably that the faults in the carburettor caused it to be starved of fuel or to flood and one of these situations led to the power loss.

Prior to departure from Ceduna, the pilot refuelled both fuel tanks. This should equate to about two hours endurance per tank. Approximately 55 minutes after departure, while cruising at 7,000 ft, the engine suddenly lost power. The pilot established the best glide speed and performed trouble checks. Engine instruments were all in the green range. The fuller fuel tank was selected and the electric fuel pump switched on but except for an occasional surge, the engine would still not produce power.

The pilot informed Adelaide Flight Service of his situation and then concentrated on a forced landing approach to a wheat paddock, where the aircraft was landed without damage. After landing, the pilot ran the engine, but it would still not produce significant power. Initial engineering investigation indicated a faulty fuel injection system.

The pilot reported that he had descended with the intention of moving a mob of cattle when some ran under the helicopter. He turned to follow the cattle but then realised that he was travelling downwind. Power to maintain height was not adequate and the main rotor was overpitched. As a result, the helicopter struck the ground hard with a ground speed of about 20 kts. The pilot assessed the wind as south-easterly at 15 to 20 kt.

Prior to recovery of the helicopter, the owner checked the engine and was satisfied that it was capable of normal operation.

The fixed emergency locator transmitter was activated but was not used or required for the rescue. The occupants walked to a nearby hill and used a citizen band radio to contact a truck which took them to a local mine.

The pilot reported that while conducting an aerial inspection of cattle, he flew the helicopter through a descending right turn into wind. As he commenced to flare the helicopter at about 100 ft AGL, the engine RPM dropped rapidly. He lowered the collective control and wound on more throttle. There was no response from the engine.

The helicopter rapidly developed a high sink rate which the pilot was not able to arrest completely before impact with the ground. The helicopter bounced twice and rolled onto its left side. Neither of the two occupants were injured. They escaped from the wreckage through the right cabin exit.

The licenced aircraft maintenance engineer who recovered the helicopter from the accident site reported that he could not find a mechanical reason for the power loss. He said that the helicopter was being operated on mogas which is a more volatile fuel than avgas and in the higher temperatures, it tends to vaporize in the fuel line, causing an interruption of fuel to the engine.

The helicopter was fitted with an approved emergency locator transmitter which operated, alerting the Search and Rescue Centre in Brisbane.

He initiated a practice forced landing and conducted the required checks. At about 2,800 ft he attempted to warm the engine but obtained no response. The throttle was retried, still without response. The emergency checks were carried out again and a Mayday call was transmitted. The pilot attempted to restart the engine using the starter.

With no engine response, the pilot continued with the forced landing. Two fields were selected, with the secondary field being beyond an earth bank at the far end of the desired field, as the pilot had been experiencing a tendency to overshoot during the earlier flights. Since no response was obtained from the engine, the engine shut down checks were completed prior to landing.

Witnesses reported that the engine note had not varied during the approach to land. There was no surging or back firing. The aircraft touched down at the end of the primary paddock and rolled some 18 m before colliding with the earth bank which was about 1.8 m high. The fire wall and rudder pedal areas were distorted by the impact.

Subsequent investigation involved analysis of a fuel sample from the aircraft and examination of a section of exhaust pipe from the engine. The fuel was within specifications, and the exhaust pipe temperature was below the detectable limit. Since an idling engine could also have exhibited temperatures below that limit, no conclusion concerning engine operation could be reached. An examination of the engine and its systems did not find any abnormalities which could have caused the problem. The Bureau of Meteorology reported that the air was very dry and there was no possibility of carburettor icing. No reason for the engine's failure to respond has been established.

The aircraft was not equipped with an emergency locator transmitter.

SIGNIFICANT FACTORS

1. The engine failed for reasons not determined.
2. The pilot had low total flying experience.
3. The pilot misjudged the approach to land.

The pilot of the Pawnee Brave was conducting a procedure turn to the right, at the end of a spray run. At a height of about 150 ft he heard a loud bang, felt the aircraft shudder, and saw flames passing down the left side of the engine cowling. From the apex of the turn, at a height of about 250 ft, the pilot elected to land in an open field adjacent to the wheat crop he had been spraying. He kept the engine running, as it was still developing some power, until the landing was assured Before he had crossed the boundary fence, the cockpit had started to fill with smoke.

Once the landing was assured, the pilot completed the emergency shut down checks and landed. His vision was obscured by engine oil on the windscreen, smoke in the cockpit and flames and smoke outside the aircraft. After landing, the pilot found that directional control and braking were hampered due to the left brake failing. Once the aircraft had stopped the pilot was able to escape safely but was unable to extinguish the fire with the portable fire extinguisher. The aircraft was totally burnt out within 30 minutes.

A subsequent examination of the wreckage found that a cylinder had separated on the left side of the engine, fracturing a fuel injector line. Fuel had sprayed onto an adjacent high tension ignition lead conductor, which was shorting to the sparkplug body. The left brake failed due to the airborne fire burning through a flexible hydraulic brake line.

The helicopter was on a scenic flight over the Bungle Bungle National Park. As it passed an outcrop it appeared to be rocked by turbulence. The helicopter yawed to the right and commenced an uncommanded descent. The pilot stopped the descent and checked the engine indications. Although no warning lights were illuminated the rotor and N2 RPM were still increasing. The pilot was able to stop the N2 overspeed at 104 per cent. He turned the helicopter towards the airfield and commenced a cruise descent. As the helicopter descended through 150 ft, on final approach, the engine-out alarm sounded, and the pilot heard the turbine RPM decreasing. He turned the helicopter into wind and completed an autorotational approach, landing short of the airfield. After landing, the pilot observed the engine was still operating at idle RPM.

Post-landing inspection disclosed damage to the tail boom, probably as a result of a heavier-than-normal touchdown.

It was reported the rotor and N2 RPM problems were the result of a sheared engine governor drive shaft.

The pilot was conducting a flight to land three passengers onto the top of Mount Sonder. Prior to making an approach to the cleared area he carried out an engine power check which confirmed that the engine was developing sufficient power to accomplish a landing at the high altitude. The pilot then carried out an inspection of the landing area and completed all four legs of the circuit. While turning onto final approach for landing he noticed a rapid reduction of the manifold pressure indication from 26"hg to 20"hg, accompanied by a loss of engine power.

The pilot was unable to continue to the intended landing area, and was committed to a landing on the sloping, rocky mountain side.

As the pilot reduced the helicopter's forward speed prior to landing the tail rotor struck a rock, causing a yaw. The pilot immediately closed the throttle, and the helicopter came to a stop facing up the slope suffering substantial damage to the landing skids, and separation of the tail rotor blades.

No faults or malfunctions were found with the engine which may have contributed to the loss of power.

An inspection of the turbocharger revealed slight scuffing of the turbine wheel, but the assembly spun freely. The density controller and wastegate were removed for overhaul, obvious problems with these units being difficult to detect.

The reason for the loss of engine power could not be determined.

The pilot was operating a helicopter joy flight from Coolangatta to Cook Island and return. On board were the pilot and four passengers. The pilot reported that the helicopter's engine failed while flying about 50 metres offshore, at a height of approximately 500 ft. He said that at the same time he noticed the power loss, the engine-out light started flashing. During the subsequent forced landing, the helicopter landed heavily, coming to rest upright, but slightly nose down in about 30 cm of water. During the landing the main rotor blades flexed downwards and severed the tail boom.

After the helicopter came to rest the pilot assisted the passengers to safely exit the aircraft.

The pilot advised that the engine continued to run at a very low idle for some time before he re-entered the helicopter and closed the fuel shut-off control.

Based on information provided by the pilot the helicopter's weight and balance were assessed to be within limits.

The investigation revealed that the nut which secures the bleed air sensing line between the power turbine governor and the fuel control unit was loose at the fuel control end. The loss of this sensing function limited the available fuel flow. As a result, engine rpm reduced uncontrollably to a low idle.

Fret marks on the mating surfaces of the nut and the male nipple at the rear of the fuel control indicated that the engine may have operated for a period of time with the nut loose. Specialist metallurgical examination was unable to determine how long the nut had been loose. After the accident, a substitute sensing line was fitted and the engine operated normally. Examination of the maintenance documentation could find no evidence of any recent work being carried out on the sensing line.