The pilot declared a "Mayday", approximately 15 NM from runway 15 at Cairns. He advised "I think I've run out of fuel, going in". The aircraft ditched a short time later, 2 NM off the coast of Wangetti Beach.
All 5 persons on board were rescued safely.
FACTUAL INFORMATION
History of the flight
The pilot was to fly a normally aspirated PA23-250 (Aztec) aircraft from Cairns to Horn Island and to return in VH-CAR, a turbo-charged Aztec. Three non-paying passengers were to be carried on each flight. The flight from Cairns to Horn Island was conducted on 2 November and the return flight was planned for the afternoon of 3 November. The senior pilot at Horn Island tasked the pilot to divert to Bamaga to pick up a fare-paying passenger and transport him to Cairns. At that time the senior pilot explained to the pilot the changes to aircraft equipment requirements and other aspects related to the change of category from private to charter.
Prior to departure from Horn Island, the pilot obtained a briefing on some aspects of the operation of the aircraft, as this was the first time he had been tasked to fly the turbo-charged variant of the Aztec. The engine turbo system involved differences in engine handling, fuel flow and aircraft performance. The pilot refuelled the aircraft to full tanks. The aircraft departed from Horn Island at 1508 and after boarding the passenger at Bamaga, departed there at 1543. Fuel was drawn initially from the outboard tank in each wing. Both fuel gauge readings initially reduced evenly. The aircraft was flown at 9,000 ft with a ground speed of 135 kts until about Princess Charlotte Bay, when the ground speed increased to 140 kts. During the flight the pilot monitored all tank caps for evidence of leaking, as was his normal practice. No leaks were observed.
The aircraft was equipped with four fuel tanks, one located inboard and one outboard in each wing. Fuel can be drawn from any of the four tanks to provide fuel to either engine by the use of two three-position selectors (inboard, outboard and off) and a cross-feed selector in the cockpit of the aircraft. It is normal for fuel to be drawn from either tank in each wing to feed the adjacent engine. There were two fuel gauges, one for each wing of the aircraft. The gauges indicate the fuel remaining in the tank which is selected on the cockpit fuel tank selector.
About 10 NM before the aircraft crossed the coast at the southern shore of Princess Charlotte Bay, the left engine began running roughly. This position was earlier than the pilot's intended fuel tank change point; however, he regained smooth engine operation by selecting the left inboard tank to feed fuel to the left engine. Prior to the engine running roughly, the left gauge had been reading between one-half and three-quarters full. The gauge indicated full when the inboard tank was selected. The right fuel selector was changed from right outboard to the right inboard tank about 10 minutes later, the time at which the pilot had expected to make that selection. Its gauge reading then changed from below one-quarter full to a full indication.
The flight continued uneventfully until about 50 NM from Cairns when, at 1825, the left engine again began to run roughly. The pilot reported that on this occasion he could only regain smooth operation by cross-feeding fuel from the right inboard tank. Both engines were then drawing fuel from the right inboard tank. He did not notice the left fuel gauge at that time but saw that the right gauge was indicating half-full. Shortly afterwards, the pilot initiated a descent from 9,000 ft.
At 1829, the pilot changed his radio frequency from the Cairns Centre frequency to Cairns Approach. During the initial contact with Cairns Approach he reported maintaining 7,000 ft and was told to expect an ILS approach for runway 15. He then requested minimum delay and was cleared to use maximum speed to the field. The recorded radar data indicated a speed reduction at 1838, when the aircraft was at 3,600 ft. Normal operational transmissions between the controller and pilot continued until 1839, when the pilot made a Mayday transmission during which he said "I think I'm out of fuel here. I'm just going over towards the coast". Radar contact was lost by the Cairns Approach controller at 1842, when the aircraft was descending through 1,000 ft with a ground speed of 84 kts. The controller subsequently calculated the last known position of the aircraft, a datum for search purposes, as a point on the 317 VOR radial at 13 NM from the Cairns DME site.
The pilot told the passengers to ensure that they were strapped in and to prepare for a ditching. He directed the front right seat passenger to unlock the aircraft's entry door and hold it ajar for the ditching. The pilot aligned the aircraft to ditch along the sea swell and did not extend the landing gear or flaps. Because he was concerned that he might hinder the evacuation of the passengers by the need to undo his seat belt, the pilot undid his seat belt prior to the ditching.
The ditching occurred about 1.5 km from shore, after which all occupants promptly vacated the aircraft. The pilot was dazed after his head struck the instrument panel, and was the last to leave the aircraft, assisted by a passenger. The survivors stayed together and commenced moving towards the shore. No life jackets were carried in the aircraft, nor were they required by legislation. After about 45 minutes in the water, two people decided to swim for shore ahead of the others. Soon after this a rescue helicopter located all the survivors about 500-600 m from shore and began rescue winching operations. The survivors determined the order in which each would be rescued, depending on their well-being at the time. During winching of the fourth person, an inflatable rescue boat operated by the Cairns Airport Rescue and Fire Fighting Service arrived at the scene and was able to rescue the remaining survivor.
The pilot and one passenger received minor injuries during the ditching. One passenger was injured during the winching operation. The other two passengers were not injured. The aircraft sank within minutes of the ditching.
Pilot in command
The pilot had been working as a flying instructor and held a Grade 2 instructor rating prior to commencing employment with the company as a Cairns-based pilot. He had recently gained a command instrument rating for multi-engine aircraft. The flying for the rating had included his Aztec aircraft type endorsement training. Before the trip to Horn Island, he had refamiliarised himself with aircraft handling procedures and had conducted simulated instrument approaches for Horn Island and Cairns, in the company's simulator. He believed that the indications provided by fuel gauges fitted to this category of aircraft were generally unreliable. The pilot was appropriately qualified to undertake the flight.
Operational aspects
The operator employed a chief flying instructor and a chief pilot at Cairns. The chief flying instructor was responsible for type conversion training as well as pilot check-and-training duties. A senior base pilot and a senior pilot were employed at Horn Island in addition to three other pilots. Flying statistics were forwarded to Cairns regularly; however, the operations at the two bases were conducted independently. New pilots employed at Horn Island usually commenced by flying the Aztec aircraft, progressing to other types as they gained additional experience. Each day's flying in the Torres Strait area was arranged by Horn Island staff on the previous day. The arrangements for the diversion to pick up the Bamaga passenger were also made on the day prior to the accident flight.
An air operators certificate (AOC) had been renewed to the operator on 26 June 1996 and was valid to 30 June 1997. An amendment to the AOC, to introduce a new aircraft type, had been promulgated on 11 September 1996. This revised AOC was also valid to 30 June 1997.
Operational surveillance of the operator by the Civil Aviation Safety Authority (CASA) had last been conducted on 16 January 1996, in accordance with planned schedules. Ramp checks of the operator had been conducted in accordance with CASA schedules, mainly in the Torres Strait area. No significant shortcomings had been detected during the various checks. The latest ramp check on the operator was conducted on 18 April 1996. The latest ramp check involving VH-CAR was conducted on 20 June 1995. Dangerous Goods inspections of the operator were conducted on 4 December 1995 and again on 23 July 1996.
VH-CAR was maintained by its owner, who was a licensed aircraft maintenance engineer based in north Queensland and not an employee of the operator. Surveillance of the maintenance organisation had been conducted early in 1996 because the owner had established the business under its own certificate of approval. No deficiencies likely to have contributed to the problems encountered during the accident flight were found.
Fuel system
The aircraft was fitted with four flexible rubber fuel cells, two in each wing outboard of the engines. Each cell was fitted with button-type fasteners on the bottom, and bayonet-type clips on the top side, to allow the cell to be attached to the wing structure. These fasteners were intended to retain the cell in its correct shape. As a result of tank material deterioration or problems with the tank venting system, these fuel cells can detach from their retaining points and become distorted. Such distortion can reduce the tank capacity, prevent fuel flow to the engine, and/or cause erroneous fuel gauge indications. Instructions for operation of the fuel system were contained in the aircraft flight manual and in the manufacturer's owner's handbook. The VH-CAR flight manual section on fuel management stated, in part, that "Crossfeed shall be used only to extend range after failure of one engine". Flight manuals for other Aztecs were checked and found to contain no such instruction. The pilot indicated that he had not read the flight manual for this aircraft. The investigation found nothing in the manufacturer's owner's handbook for this aircraft to indicate that crossfeed should not be used when both engines were operating. In fact, the owner's handbook gave instructions for the use of crossfeed to run both engines from one tank. A number of experienced pilots provided information to the investigation, indicating that the engines ran quite successfully when both were fed from one fuel tank, provided the manufacturer's procedures were followed. Tests conducted in 1979 by an experienced pilot, following an incident involving fuel crossfeeding in an Aztec, showed that it could take up to 17 seconds to restart an engine after fuel starvation.
The investigation team conducted an analysis of estimated fuel consumption. At the time of the first rough-running event, the left outboard tank should have been almost empty. When the right fuel tank selection was changed, its outboard tank should have been empty. On the second rough-running occasion, the left inboard tank should have contained about 78 L of fuel. At that time, when both engines began operating from the right inboard tank, the tank should have contained about 84 L of fuel. When both engines stopped some 13 minutes later, there should still have been 57 L of fuel in the right inboard tank.
Two passengers reported seeing smoke, mist or vapour coming from each engine during the flight. The pilot's attention was drawn to the matter but he indicated that it was not of concern. The pilot could not recall this event during interview. The investigation was unable to discover any evidence of possible defects involving either engine.
The pilot said that no unserviceabilities which would have affected the aircraft's operational capability for the flight had been recorded in the maintenance release. He had been instructed by the senior base pilot on Horn Island to enter on the maintenance release any problems he discovered so that they could be corrected. Because of the apparent anomalous indications from the left fuel gauge experienced during the flight, the pilot intended recording the gauge as faulty upon his arrival in Cairns. He considered that the left gauge reading was too high on a number of occasions during the flight.
Examination of the aircraft maintenance records did not disclose any ongoing problem with the fuel system of this aircraft. All fuel system maintenance undertaken had been as a result of normal wear or airworthiness directive requirements. There was no record of recent maintenance work performed on the aircraft which could have had an influence on the problems encountered during the accident flight. The operator provided flying times and refuelling quantities for some months prior to the accident. Comparison of the hours flown and the fuel used did not reveal excessive fuel consumption rates, nor was there a trend towards high fuel consumption.
Weather information
The general weather was such that most of the flight was conducted above cloud. Scattered cloud was encountered during the descent. Throughout the flight, a headwind component of about 20 to 25 kts was experienced. In the area of the ditching the surface wind was south-easterly at about 15 kts.
Communications
Communication and radar facilities operated normally throughout the period of the flight. Contact with the aircraft was lost at about 1,000 ft above sea level due to terrain shielding. The same problem hindered communications during the search and rescue operations.
The approach controller handling the aircraft provided prompt assistance when the pilot reported his problem. Telephone system congestion between Cairns and the Rescue Co-ordination Centre in Brisbane hindered communications between the parties. Steps have since been taken to provide additional capacity through another service provider should a similar problem occur. Air traffic controllers also experienced difficulty contacting the Queensland Emergency Services helicopter crew because they were using an outdated list of telephone numbers. The list has since been corrected.
The ditching
No ditching instructions were contained in the various publications relating to the operation of the aircraft. The pilot ditched the aircraft using information derived from prior discussions of the circumstances likely to be encountered in a ditching. He did not extend the flaps because he wanted to keep the aircraft attitude flat and was concerned about a possible "pitch-down and nose-dive" if the flaps contacted the water first. The propellers were not feathered after engine power was lost. During the latter stages of the flight, the pilot noticed an indicated airspeed of 80 kts. He was not aware of the airspeed at touchdown, nor was he trying to maintain a particular speed.
Search and rescue
The Queensland Emergency Services helicopter crew was available at its Cairns Airport base. In accordance with their procedures, a second pilot was required because the flight was likely to involve night winching over water. The departure for the accident location was delayed by about 5 minutes for the second pilot to arrive. The crew used the ditching position of the aircraft calculated by the approach controller as a datum for the search. The helicopter was equipped to conduct a visual search using the night sun searchlight. The crew commenced the search 1 NM before the datum and continued until 1 NM after the datum. Their intention was to search a small area either side of the likely position of the aircraft. Although the sun had set there was still some light from the west and they elected to fly a reciprocal track further to the east in the hope that survivors might be silhouetted against the light. This was unsuccessful, so the next search leg was flown to reposition the helicopter at the datum. A reciprocal track towards the west was then flown as the start of a series of search patterns working from the search datum towards the coast. The survivors were found about half-way along that first search leg. A crewman was lowered to assist each survivor from the water and to supervise each winching aboard the helicopter. The first person to be winched aboard the helicopter was suffering from asthma and was given oxygen. The helicopter pilots, aware that the survivors might have difficulty countering the downwash from the main rotors, moved the helicopter away from the survivors during each winching operation.
Two inflatable boats crewed by Rescue and Fire Fighting Service (RFFS) staff from Cairns Airport arrived near the end of the helicopter winching activities. These boats carried only flotation devices (similar to inflatable rafts) for survivors of an aircraft ditching because the boats were intended to be operated within 2 km of the airport. On this occasion the boats were transported by road to a beach close to the search area before being launched. The last survivor was passed a life jacket from the helicopter so that he would have one to wear in the boat.
ANALYSIS
Fuel system handling
Although the pilot considered that the left fuel gauge read higher than he had expected on a number of occasions, he did not perceive any trends in the fuel gauge indications, probably due to his mistrust of the accuracy of fuel gauges. However, had he consistently monitored the gauges, he may have recognised the need for earlier alternative action. Fuel system management by the pilot was in accordance with the operator's procedures, which were compatible with the manufacturer's owner's handbook. The first rough-running engine event took place to the north of Cooktown. Since the pilot needed to change tanks to correct the problem, and this was before his planned tank-change time, a landing at Cooktown to visually check the actual fuel state would have been prudent. Such a decision should have been reinforced by the left gauge indicating between one-half and three-quarters full. This was markedly different from the right gauge and much higher than the reading should have been for the elapsed flight time. The pilot continued towards Cairns, still satisfied that sufficient fuel remained. This decision was probably influenced by his opinion that fuel gauges in this category of aircraft were generally unreliable. When the second rough-running engine event occurred, the pilot should have become more concerned. He regained engine power by cross-feeding both engines from the right inboard tank. This situation was not planned, nor should it have been considered normal. Options to increase range were available. A reduction to long-range cruise power would have significantly reduced the fuel flow, and by maintaining 9,000 ft or 7,000 ft until much closer to Cairns, the aircraft's range could have been extended.
These options were not considered by the pilot. Examination of the aircraft logbooks and maintenance worksheets found no history of fuel system problems. The aircraft should have contained sufficient fuel for the flight plus company-required reserves. No trends or possible explanations for the fuel problem could be determined by the analysis of refuelling records for a number of months earlier, nor from an examination of the timings and circumstances described by the pilot. Consideration was given to a number of scenarios which could have led to the problems encountered on this flight:
1. One or more fuel tanks could have been deformed prior to the refuelling at Horn Island. This would have reduced tank capacity and may not have been noticeable during a visual inspection.
2. Tank venting problems during flight could have deformed one or more tanks, resulting in reduced fuel flow to the engines.
3. Fuel leakage could have developed during the flight. As the aircraft wreckage was not recovered, the reason for the loss of engine power could not be determined.
Survival aspects
The pilot's decision to release his seat belt prior to the ditching was unsound. He had not considered that he could be incapacitated by impact forces. Had he been injured more severely he may have been a considerable handicap to the egress of the other occupants from the aircraft.
SIGNIFICANT FACTORS
1. Fuel-flow interruptions involving the left engine were experienced on two occasions during the flight.
2. The pilot did not divert or take actions to minimise the effects of possible fuel starvation or exhaustion.
3. It is likely that both engines failed due to fuel starvation or exhaustion.
4. The pilot's head injuries resulted from his decision to not wear a seat belt during the ditching.
SAFETY ACTION
As a result of the investigation into this occurrence, the Bureau of Air Safety Investigation issued Safety Advisory Notice SAN970048 to Airservices Australia. The SAN highlighted the following deficiencies in the role and use of inflatable rescue craft in the rescue operations:
1. The rescue boats were designed and equipped to respond to an aircraft ditching within a distance of 1,000 m from the boundary of the airport. In this case they were operating some 12 NM from the airport. The rescue crews experienced radio communication problems with the control tower due to the distance from the aerodrome and the terrain between the ditching area and the aerodrome. Also the crews of the boats were not able to communicate with the police service. The police service is responsible for the coordination of all rescue services at the scene.
2. The boats were dispatched by the local RFFS district officer. There was no definitive policy in place at the time to cover the operation of the boats at this distance from the airport. No coordination was conducted between the crews of the inflatable boats and the Rescue Coordination Centre in Brisbane, which was responsible for the conduct of the search-and-rescue operation.
3. The survivor who was rescued by boat had been in the water for over one hour, and had removed most of his clothing in an attempt to remain afloat. The boat crew had no clothing or other material available for the survivor to prevent any further heat loss.