Collision with terrain

The pilot of a Piper Pawnee Brave had undertaken to spray an extensive area of land with a herbicide. He commenced operations at around daybreak, departing from his base with a load of chemicals. After that trip, and for the rest of the day, he operated from an airstrip on a property closer to the spray area.

The strip was a private access road that had been upgraded for a length of 800 m to serve as an airstrip. It ran perpendicular to a north-south sealed public road. Adjacent to the sealed road, and running parallel to it, was a powerline about 5 m high. The western end of the airstrip was about 50 m from the powerline. There were no signs on the road to warn motorists that low flying aircraft may be operating from the strip and crossing the road at low level. On each flight the pilot was landing the aircraft towards the east and taking off towards the west.

Because of its weight, the aircraft was flown under the powerline during most take-offs. Prior to commencing each take-off, the pilot checked for traffic on the road. From the cockpit he had a view of the road for about one kilometre in each direction. The pilot commented that he had to wait for traffic on a number of occasions during the day. He reported that because of fatigue and the low sun angle during the accident flight, he did not notice a vehicle travelling south. Just after becoming airborne the pilot saw the car but was unable to take avoiding action.

The left main wheel of the aircraft collided with the front left corner of the car's cabin and ran across its roof before breaking off and coming to rest in an adjacent paddock. The pilot considered that the aircraft was operating normally so he continued with the intended spraying operation and then returned to his home base for a landing. He provided no explanation as to why he did not report the accident immediately.

The driver of the car stated that she saw the aircraft just prior to the impact but was unable to take avoiding action. A passenger in the front seat received lacerations from the broken windscreen.

History of the Flight

The Agusta /Bell 47G-2A1 helicopter, registered VH-FLI, was borrowed by the pilot to fly his sister to her wedding at the family property near Holbrook NSW.

The pilot arrived at the helicopter owner's property around 0900 Eastern Standard Time on the day of the accident, and with assistance from the owner, he completed a pre-flight inspection of the helicopter. The pilot subsequently conducted a number of flights on the day of the accident.

At about 1730, the pilot and his sister boarded the helicopter and departed in an easterly direction. The pilot then followed a route that ran adjacent to the Holbrook to Jingellic road in order to remain near the car being driven by his mother.

Witnesses reported that the helicopter was flying at a very low height as it neared Chinamans Gap. At approximately 1745, when the helicopter was about 6 km from its destination, it struck a powerline, pitched nose down and impacted the ground on its left side. The impact and the subsequent fire fatally injured the occupants and destroyed the helicopter.

Pilot Information

The pilot held a Commercial Pilot Helicopter licence, issued in September 1993. The pilot's Bell 47 qualification had been gained in August of that year. The pilot had also served as a helicopter pilot in the Royal Navy, the Australian Army, and the Royal Australian Navy. His military pilot logbooks indicated that he had significant helicopter low-level flying experience and his civilian logbook showed that he had completed civilian helicopter low flying training. As part of that training he had been alerted to the dangers of powerlines during low-level flight, and of the need to carry out a reconnaissance of an area before conducting a low-level flight. The pilot had not previously flown the route followed to the property where the wedding was to be held.

Records of his Bell 47 flying experience were incomplete, with the last recorded flight being in August 1994. However, witnesses reported that he had flown this Bell 47 on numerous occasions since that time. The pilot's total recorded Bell 47 flying time was 23.8 hours. His friends and colleagues indicated that he was a careful pilot.

While the pilot was required by the Civil Aviation Safety Authority to have "visual correction for distant vision" during commercial flights, his uncorrected vision was adequate to meet the private pilot licence standard. No evidence was found that the pilot was wearing spectacles at the time of the accident. Witnesses indicated that the pilot had received adequate rest prior to the flight. There was no evidence found to indicate that the pilot's performance was adversely affected by any pre-existing physiological condition.

Wreckage Information

Examination of the wreckage indicated that the powerline first entered the area between the skid landing gear and the cockpit floor, severing the landing light before contacting the landing gear forward cross tube. The main-rotor blades severed the tailboom approximately 1 m forward of the tail rotor assembly. The two fuel tanks, which had detached during the initial impact, burst open. The main wreckage of the helicopter was subjected to an intense fire fed by the fuel from the burst tanks.

Examination of the wreckage revealed no mechanical faults that may have contributed to the accident. No wire-strike protection devices were fitted to the helicopter.

Weather

The wind was light and variable, visibility was 40 km, and there was 1 to 2 octas of high-level cloud. The temperature was 29 degrees Celsius, the dew point was 2 degrees Celsius and the QNH was 1012hPa. The likelihood of carburettor icing at the time of the accident was extremely low. The sun was behind the helicopter at the time of the accident.

Accident Site

The helicopter had impacted the tarmac road surface, just beyond a road cutting in a ridgeline. The powerline ran approximately 90 degrees to the helicopter's flight path and was strung between two poles that were each located on peaks of the ridge. The distance between the two poles supporting the powerline cables was about 900 m. At the point where the helicopter contacted the powerline cables, the cables were at a height above the roadway of approximately 31 m. The powerline had been erected several years before the accident and had developed a dull oxidised finish. There were no high visibility devices on the powerline cables to make them easier to detect from aircraft. No maps were found with the wreckage, and due to the relative recency of the erection of the powerline they did not appear on topographic maps of the area.

Pilots who regularly flew in the area indicated that the powerline was difficult to see from the air because the cables blended with the background of trees and other vegetation. One pilot advised that he had previously reported this to the power transmission company, suggesting that the powerline cables were a hazard to aircraft and that something should be done about making them more visible. The power transmission company reportedly replied that the height of the powerline was lower than the minimum height for powerlines requiring the fitment of high visibility devices as laid down in Australian standards.

Regulations and Standards

The Australian standard relating to cables and their supporting structures, required them to be marked with warning markers if the height of the lines exceeded 90 m above ground level. There was, however, a proviso that this standard could be varied if an air operator referred the matter to the appropriate Regional Airspace Advisory Committee for resolution.

The Civil Aviation Regulations require a helicopter that is not over a town or populous area, to remain a minimum of 500 ft above ground level. Further, the helicopter must be 500 ft above any obstacle within a 300 m radius of the helicopter's flight path, unless taking-off or landing.

The pilot was conducting a visual flight rules (VFR) flight from Walgett to an airstrip near Merriwa. The aircraft had departed from Walgett earlier in the day, but had returned a short time later when it was reported that the weather at the destination was not suitable for VFR flight. The pilot felt that he was under pressure to complete the flight that day. He continued to monitor the weather by telephoning for weather reports that were available from an automatic Bureau of Meteorology outlet, and by contacting a friend near the destination airfield. The aircraft later departed at about 1415. A search was subsequently initiated when the aircraft failed to arrive at its destination. The wreckage of the aircraft was located two days later on the top of a ridge, 3,880 ft above mean sea level (AMSL), slightly to the left of the direct track between Walgett and Merriwa.

The aircraft was found to have collided with trees during a right turn, at a rate of descent of about 2,500 ft/min. The impact severed the outboard section of the right wing. The aircraft had then collided with other trees before striking the ground. The right fuel tank had ruptured during descent through the trees and an intense post-impact fire had consumed the cabin area and the fuselage section immediately behind the cabin. Although the accident was survivable, both the pilot and passenger received extensive burns while escaping from the burning wreckage. The pilot died sometime later from his injuries, before the aircraft was located by search-and-rescue services personnel during the morning of the second day of the search. A fixed emergency locator transmitter (ELT), mounted in the aft cabin area of the aircraft, was destroyed by the fire. While it was not possible to determine if the ELT had activated during the accident sequence, no signal from the ELT had been received by the satellite monitoring system. The pilot was known to possess a personal ELT; however, this was not located after the accident.

Examination of the wreckage did not reveal any deficiencies that were likely to have contributed to the accident. Data extracted from a portable global positioning system unit found at the accident site confirmed that the aircraft had been in a right turn when it collided with the trees. Shortly after the accident the pilot had written a brief message on the left tailplane of the aircraft. That message indicated the pilot's perception of the accident sequence, and was generally consistent with the analysis by the investigation team.

The pilot held a private pilot licence for aeroplanes, and a commercial helicopter licence, together with valid medical certificates; however, he did not hold a rating for flight in instrument meteorological conditions (IMC), nor was the aircraft approved for flight in IMC.

Reports from National Park rangers who were in the area at the time of the accident, and from the Bureau of Meteorology, indicated that the cloud base was 3,600 ft AMSL, and that cloud was covering the ridge where the wreckage was found. The weather over lower terrain to the south-west of the accident site was reported to have been suitable for VFR flight.

The pilot was conducting a private flight from King Island to Moorabbin in a Piper PA32R (Lance) with five passengers. The group had flown from Moorabbin to King Island two days earlier.

A witness saw the aircraft appear to accelerate normally along runway 35, becoming airborne before the intersection with runway 28 after a take-off roll of about 430 m. A short distance beyond the runway intersection, at a height of about 100 ft, the aircraft pitched steeply nose up and banked left about 30 degrees. The aircraft appeared to hang in the air momentarily, with the engine at high power, before banking further left in a nose high attitude and being lost to sight behind trees. The aircraft impacted the ground in a steep nose-down, left wing low attitude, tearing off the left wing, before sliding along the ground for about 65 m and coming to rest on runway 28.

The airport groundsman reached the accident site quickly, and shortly after was joined by three other people, all of whom assisted the injured. A fire truck arrived at the site 15 to 20 minutes after the accident and an ambulance arrived in about 30 minutes.

The pilot and passengers remained strapped in their seat belts throughout the accident. The pilot, front seat passenger, and a passenger occupying the rear left seat suffered fatal injuries. The three remaining passengers suffered serious injuries. Those who sustained the least injuries were the two passengers in the two aft facing centre seats.

Five minutes after the accident the automatic weather station at King Island airport recorded the wind velocity as 059 degrees at 18 kts, gusting to 25 kts. The outside air temperature was 20.6 degrees Celsius. Conditions were described by a witness as sunny, with no cloud and good visibility. A pilot who took off from King Island about 30 minutes after the accident reported experiencing strong wind gusts and windshear.

The pilot held a valid private pilot licence endorsed for single-engine aeroplanes below 5,700 kg maximum take-off weight, equipped with retractable undercarriage and constant speed propeller. She had a total flying experience of 172 hours, including 7.7 hours in the Piper Lance, and 1.2 hours in a Piper Cherokee Six.

An investigation subsequently found no defects with the airframe or engine that may have contributed to the accident. The landing gear was extended at impact, consistent with the position of the landing gear selector. The wing flaps were set 10 degrees down, and the engine had been producing power.

The pilot's seat was found locked on its rails in a position appropriate for the pilot's size when controlling the aircraft. The aircraft was equipped with the standard manual trim wheel on the floor as well as an electric trim switch on the pilot's control column. The stabilator trim setting, evidenced by the indicator in the cockpit, and confirmed by the trim jack position, was found slightly forward of neutral.

An emergency locator transmitter (ELT) located in the rear fuselage was armed but had not activated on impact. Subsequent tests found the ELT to have been serviceable. The reason why the ELT did not activate was not determined. The pilot also carried a marine EPIRB for the over-water Bass Strait crossing between King Island and Moorabbin.

Fuel records indicate that the pilot probably departed Moorabbin with full fuel tanks and subsequently took off from King Island with an estimated 286 L of AVGAS remaining.

During the night after the accident police weighed most of the bags found on the aircraft. They described the baggage as having been dampened externally by fire-fighting foam, leaving the contents dry. A small amount of gear remained with the wreckage until the following day. Rain saturated some of this remaining gear. Two of the survivors subsequently attempted to recall where the baggage had been positioned in the aircraft prior to the accident. They also provided estimates of baggage weights. Their recall was enhanced because the pilot had insisted they weigh themselves and their baggage using scales before the flight. These scales were reported to over-read slightly. No evidence was found that passengers had added unweighed items to their luggage. The gear carried in the nose locker was estimated to total about half of the 45 kg allowable weight. The weight of gear behind the rear seats ranged from about 35 kg using passenger estimates, to possibly 83 kg using the police weights, which included an unknown factor for dampness. The maximum allowable baggage weight behind the rear seats was 45 kg. Several items of luggage were distributed throughout the cabin.

Using the baggage weights recalled by the passengers, the estimated take-off weight at King Island was probably slightly below the maximum allowable. Using the damp baggage weights provided by the police, the aircraft may have been up to 48 kg above the maximum allowable take-off weight.

The aircraft was originally fitted with a two-bladed propeller. Records show that in 1994 a three-bladed propeller was fitted, which was 7.2 kg heavier. An approved supplement for the three-bladed propeller was included in the flight manual, but a revised weight and balance sheet referred to in the supplement, was missing. The additional weight of the three bladed propeller would have had the effect of offsetting a tail-heavy condition rather than aggravating it.

Because of the disruption to the baggage following the accident and associated rescue efforts, and because of doubt as to the exact location of individual items of baggage and the unknown weight factor for the damp baggage, it was impossible to accurately determine the position of the aircraft centre of gravity. Based on information provided by the passengers, the centre of gravity was probably within the aft limit. Using baggage weights provided by the police, the centre of gravity could have been slightly less than 7 mm aft of the approved limit at the time of the accident. The pilot was reported to have been familiar with weight and balance calculations.

The Pilot's Operating Handbook for the PA-32-300 contains a general statement which indicates that if the centre of gravity is too far aft an aircraft may rotate prematurely on take-off, or tend to pitch up during climb, with an associated reduction in longitudinal stability. This can lead to inadvertent stalls and even spins, with spin recovery becoming more difficult as the centre of gravity moves aft of the approved limit. The handbook also states: "The stall characteristics of the Cherokee Lance are conventional. An approaching stall is indicated by a stall warning horn which is activated between 5 and 10 kts above stall speed". One of the surviving passengers described the last sounds she heard before impact as a beeping noise.

The Pilot's Operating Handbook provided take-off ground roll data based on either flaps up or flaps 25 degrees down. At maximum allowable gross weight with flaps up, under the prevailing conditions, the calculated ground roll was about 415 m for the take-off at King Island. In accordance with the Approved Flight Manual for the aircraft, the maximum permissible crosswind component for take-off and landing was 17 kts. The estimated crosswind component for the take-off ranged between 16kts and 23 kts.