Collision with terrain

The day before the accident, the pilot had made some modifications to the aircraft's spray equipment. Approximately 180 lts of water was then loaded to test the equipment.

Early the next morning, the pilot decided to test spray over a paddock. After checking the paddock for hazards, he commenced a spray run from west to east with the sun still below the horizon. The pilot noticed a loss of spray pressure and as he looked down inside the cockpit to adjust the pressure, the main landing gear struck the ground. The aircraft nosed over and slid upside down for approximately 40 m before coming to rest. The pilot was not injured and was able to extricate himself without outside assistance.

An emergency locator transmitter (ELT) was not fitted to the aircraft.

The aircraft was on final approach to Dubbo aerodrome when it suddenly descended, collided with power lines and cartwheeled to the ground. The aircraft was destroyed in the accident but the solo student pilot managed to escape with minor injuries.

The pilot subsequently reported that he had the aircraft configured for a short field landing with full flap and 60 kts approach speed. At about 400 ft on mid final, a sudden wind gust lifted the nose and right wing to a high attitude. The pilot applied full power and opposite aileron but the aircraft failed to recover before colliding with the power lines.

It is likely that the high nose attitude resulted in the aircraft stalling at a height which was insufficient to effect a recovery.

The pilot reported that while taking off from Lady Musgrave lagoon, just after the aircraft became airborne, a gust of wind caused the right wing to drop. The wing contacted the water surface, and the aircraft cartwheeled to the right. The windscreen was shattered and the cockpit filled with water immediately. The aircraft came to rest inverted under the floats in approximately 8 metres of water.

The rear seat passengers egressed safely from the right side of the aircraft with cuts and bruises. The pilot's door was jammed but the pilot kicked out the side window and egressed with the front seat passenger from the left side of the aircraft. The aircraft was eventually washed onto the reef and destroyed by wave and tide action. An attempt to salvage the aircraft was unsuccessful.

The pilot reported that the wind at the time was a 20-25 knot south-easterly, the general weather was squally conditions with wind gusts to 30 knots, and the sea state was choppy with waves to one metre.

The pilot of a Grob 115 aircraft was conducting solo circuits from runway 21L at Parafield. The pilot reported difficulty in maintaining directional control of the aircraft during the first landing flare and attempted to go around. However, the aircraft crash landed to the left of the runway and was substantially damaged. The pilot, who was uninjured, vacated the aircraft without assistance.

The floatplane was on a positioning flight from Broken Bay, north of Sydney, to Gunnamatta Bay, south of Sydney. Arriving in the area, the pilot found the turbulence was too severe to permit a landing and decided to divert to Rose Bay, on Sydney Harbour, until conditions improved.

At Rose Bay the pilot commenced an approach to land in a north-easterly direction, which was directly into wind. An eyewitness reported that just as the aircraft flared, it yawed sharply to the right, the right wing lifted until the left wingtip hit the water and the aircraft cartwheeled, coming to rest inverted. The pilot climbed out of the cockpit unaided and was rescued by the Water Police. He had received minor injuries.

A cold front, with an associated line squall, was passing through the area at about the time of the accident. Ahead of the front, there were strong winds from the north or north-east. Behind the front, the winds were from the south. Thunderstorms had been reported in the Sydney area, but were off the coast at the time of the accident.

A significant factor in this accident was that during the final stages of the landing approach, the aircraft experienced a sudden wind change. The pilot would have had little or no warning that this wind change was about to occur.

In a report to the Bureau the operator advised that the pilot was ferrying the Robinson R22 helicopter from Darwin to Katherine for maintenance when the pilot heard an unusual noise and decide to land to carry out an inspection. The helicopter was landed in a clearing 135 km south-east of Darwin but no obvious defects were found. The operator advised that shortly after taking off to continue the flight the noise was again evident, but worse. The helicopter crashed while attempting a precautionary landing.

Another agency involved with the occurrence was informed that the pilot felt a vibration while in flight and landed to investigate. He carried out a walk round inspection with the engine running and rotors turning but found nothing untoward. During the subsequent take-off he had to clear a knoll some 300ft high approximately 150m ahead. The pilot claimed there was no vibration evident during lift off and in hover, but as he accelerated there was a loud crack and from then on, he was unsure of the events that followed.

The BASI investigation was unable to have the pilot respond to a request for additional clarifying information, nor did the pilot return telephone calls.

A strip down examination of the helicopter failed to disclose any mechanical problem that may have resulted in the symptoms reported by the operator and the pilot. The personnel who recovered the helicopter found evidence that the tail rotor blades had impacted shrubs, most probably as the helicopter departed the clearing.

The investigation was not able to establish why the pilot had landed in the clearing.

The flying instructor stated that he was conducting a trial instructional flight in conjunction with visiting his property with the student. A few minutes after landing, he performed a vertical take-off into an estimated 10 kt northerly wind. Engine RPM was close to the desired 2,700. The helicopter climbed vertically using 28 inches of manifold air pressure, leaving about 1.5 inches in reserve. It cleared the tops of the trees at about 40 ft AGL. The instructor then lowered the nose slightly to gain airspeed. As airspeed increased to about 10 kts the helicopter climbed to about 45 ft AGL.

The instructor then allowed the helicopter to accelerate without increasing power when suddenly, after about 30 metres, the engine RPM commenced to decay. He immediately applied full throttle and lowered the collective slightly but RPM continued to decay and the helicopter lost height. He immediately turned the helicopter 90 degrees left towards a downhill path through the trees and lowered the nose hoping to gain more airspeed and rotor RPM. Engine RPM had decreased to approximately 2,450 and continued to decay. The instructor then tried to reach the junction of his driveway and a road but the engine stopped completely and the helicopter crashed into a tree right side first.

The main rotor blades severed the tree trunk several times and struck a smaller tree before the helicopter impacted the ground on its left side. At the time of the accident the helicopter's gross weight was about 22 kg below maximum. The accident site was about 496 ft above sea level. The outside air temperature was 17 degrees Celsius and the weather was fine. The instructor reported that the carburettor air temperature gauge read 15 degrees Celsius during the pre-take-off checks. As this reading was out of the yellow band on the gauge, he did not apply carburettor heat for the take-off.

The estimated relative humidity at the accident site was 50 to 55%. Subsequent concerns were expressed by the company operating the helicopter that carburettor icing may have caused the engine failure. The operator reported experiencing symptoms of carburettor icing and the engine stopping in this helicopter during past practice autorotations with the engine idling. Prior to the accident, the operator had prompted company pilots to be very vigilant of carburettor icing and diligent in the use of carburettor heat, particularly during practice forced landings.

The operator was also concerned at the higher-than-expected fuel usage in their 269C-1, which had the standard non-fuel-injected engine, compared to their 269C helicopters with the standard fuel-injected engine. (The Schweizer 269C-1 is also commonly known as the 300CB, whereas the 269C is commonly known as the 300C.) The operator reported that their 269C-1 used about 48 litres per hour, whereas their 269C helicopters averaged about 41 litres per hour. The operator wondered if the additional fuel used by the C-1 model may have made it more prone to carburettor icing.

The damaged helicopter was retrieved to a hangar and subsequently inspected. An engineer/investigator from Schweizer Aircraft Corporation assisted in the investigation. No fault was found with the airframe or the engine which may have contributed to the accident. No evidence was found to prove that carburettor icing had occurred. Carburettor icing is not normally encountered at or near full engine power unless high humidity or visible moisture is present. The reason the engine failed could not be determined.

The Precision Airmotive Corporation, HA-6 10-6030 carburettor was originally fitted to Schweizer 269C-1 helicopters. On 5 March 1998, the manufacturer issued Service Information Letter - Fuel Systems, SIL MS-3, Revision 1, for the mandatory conversion of carburettors in all Schweizer 269C-1 helicopters to the HA-6 10-6030-1. Helicopters with airframe serial numbers 0001 to 0073 were to be retrofitted, whereas all subsequent factory models will be equipped with the modified carburettor before sale. The conversion involved installing a new secondary nozzle, a new power jet, a new idle tube, adjusting the air metering valve and adding an acceleration pump circuit.

As well as the reconfigured carburettor, the retrofit included an air straightener, removal of one engine baffle, relocation of the cylinder head temperature probe and relocation of the optional exhaust gas temperature probe, if so equipped. The intention of the reconfigured carburettor, combined with the air straightener was to establish improved fuel distribution and better fuel economy.

The helicopter departed Mount Green in a northerly direction at approximately 1755 CST, for a survey of the locations of Army personnel in the area who were manning Rapier missile sites. The pilot said that while approaching one of the sites, he descended to approximately 100 ft AGL, and commenced a left-hand orbit while his passenger, an Army officer, was explaining the layout. When he was about halfway through the turn and maintaining approximately 60 knots with about 30 degrees angle of bank, the nose suddenly yawed to the left, and the helicopter descended rapidly in a nose low attitude. The helicopter impacted the ground, and slid backwards into a thicket of small trees 2 to 3 metres high.

One main rotor blade had sustained a spar fracture approximately 14 cms from the blade tip. Blade weight segments were installed in this region and could not be found after the accident. A section of the blade skin and honeycomb core extending over a distance of approximately 34 cms from the blade tip had also been lost. The nature of damage displayed by the blade was consistent with an impact between the blade leading edge and a solid rocky object, at a point approximately 20-25 cms from the blade tip, while the blade was rotating.

A series of unusual paint transfer markings along the upper surface of the leading edge of one main rotor blade was noted during examination. The paint was dark green in colour. Abrasive scores through some of these markings indicated that paint transfer associated with contact with some other material or component occurred prior to collision with the ground. It was established that the blade had struck a ground-to-air missile casing which was painted dark green. The stage in the accident sequence at which this occurred could not be determined.

The pilot reported that the strip had received heavy rain during the previous week and that only 680 m of the 1,000 m length was usable for operations. The centre of the strip was dry, but the edges were soft with water standing in the table drains at the side. The pilot said that the take-off run was normal until lift off when the aircraft lost 15 kts of airspeed as the right main wheel ran through a soft patch.

As result, the climb out was slow and shallow, and the aircraft veered to the right of the strip. The pilot was unable to avoid trees about 100 m to the right of the strip. The left wing struck foliage, but the pilot was able to keep the aircraft airborne. After landing the aircraft to assess the damage, the pilot found that the leading edge of the left wing was damaged.

The pilot of the C188 aircraft was carrying out spraying operations 12 km West of Clare. Due to his low experience level on the C188, the pilot was operating with a reduced internal chemical load of 600 litres rather than the maximum 757 litres. The pilot advised that on entry to a procedure turn at the completion of the fourth spray run he encountered excessive sink due to a tailwind.

The pilot attempted to arrest the sink rate by dumping the remaining chemical load and applying full power, however, due to late manoeuvering to avoid power lines this proved unsuccessful, and the aircraft impacted the ground left wing low. The pilot vacated the aircraft having suffered minor injuries in the accident.