Power v Northam Air Services Pty Ltd - [2001] WADC 154

JURISDICTION : DISTRICT COURT OF WESTERN AUSTRALIA
IN CIVIL

LOCATION: PERTH

CITATION: POWER -v- NORTHAM AIR SERVICES PTY LTD [2001] WADC 154

CORAM: WISBEY DCJ

HEARD: 26, 27 APRIL 2000, 29, 30 JANUARY 2001

DELIVERED : 26 JUNE 2001

FILE NO/S: CIV 4357 of 1997

BETWEEN: ROBERT POWER
Plaintiff
AND
NORTHAM AIR SERVICES PTY LTD (ACN 070 416 661)
Defendant

Catchwords:

Negligence - Duty of care - Causation - Claim that aircraft forced landing due to unserviceable carburettor - Whether defendant repairer negligent in failing to bench test carburettor and detect defects - Whether accident caused by defective carburettor

Contract - Breach of implied warranty as to fitness of repair work

Legislation:

Trade Practices Act 1974 (Cth) s 74(1)

Fair Trading Act 1987 (WA) s 40(1)

Result:

Claim dismissed

Representation:

Counsel:

Plaintiff: Mr P G McGowan
Defendant: Mr R J L McCormack

Solicitors:

Plaintiff: Phillips Fox
Defendant: Srdarov Richards Burton

Case(s) referred to in judgment(s):

Jones v Dunkel (1959) 101 CLR 298

Case(s) also cited:

March v E & M H Stramare Pty Ltd (1991) 171 CLR 506

WISBEY DCJ: The plaintiff, Robert Francis Power, a pastoralist, was at the relevant time the lessee of Mulgul Station via Meekatharra, and the owner of a 182E Cessna aircraft VH-RHJ (hereinafter referred to as "the aircraft"). He was a licensed pilot and used the aircraft inter alia for mustering, checking mills, and associated purposes.
The defendant operated a light aircraft maintenance and service facility at Northam.
In the statement of claim the plaintiff alleges that in or about September 1996 the defendant agreed for reward to perform maintenance work on the aircraft, and expressly undertook to check and adjust the float level of the carburettor. It is alleged that it was an implied term of the maintenance contract that the defendant would repair and/or replace any defective or unserviceable components necessary to adjust the carburettor float level; advise the plaintiff of any repairs required to the carburettor; and advise the plaintiff if because of any defective or unserviceable carburettor components it was dangerous to fly the aircraft. The plaintiff alleges that on or about 20 September 1996 pursuant to the agreement referred to, the defendant worked on the aircraft and certified that it had checked and adjusted the float level of the carburettor at 9,512 airframe hours. It is alleged that in breach of the contract, and/or negligently, the defendant failed to repair and/or replace defective and unserviceable components of the carburettor so that an appropriate adjustment to the float level could be made; failed to advise the plaintiff of the defective state of the carburettor and of the danger of flying the aircraft without repairing and/or replacing the defective and unserviceable carburettor components; and generally failed to exercise due care and skill when carrying out the work. The plaintiff claims that as a result of the defendant's breach of contract and/or negligence the carburettor malfunctioned when he was flying the aircraft during mustering operations near Wiluna on 17 October 1996 resulting in a "total loss of engine power" and necessitating a forced landing which caused extensive damage to the aircraft. The plaintiff claims damages for breach of contract and/or negligence. Quantum having been agreed, the issue for judicial determination is liability.
By agreement the evidence‑in‑chief of the witnesses was given by tendering a signed statement of evidence upon which they were subject to cross‑examination.

The evidence

Robert Francis Power

The plaintiff's statement dated 14 April 2000 was received in evidence as Exhibit 2. He recorded that he purchased the pre‑owned aircraft in approximately 1980 for the purposes referred to. The engine had been overhauled immediately prior to purchase, and the aircraft had not flown since overhaul. The plaintiff was required to have the aircraft's engine checked by a licensed aircraft maintenance engineer at the expiry of every 100 hours flying time, and the inspection and service had previously been carried out at Northam by Western Australian Aviation. If any service difficulties were encountered between the compulsory 100 hour inspections, the plaintiff arranged for a licensed aircraft maintenance engineer to fly to wherever the aircraft was located to work on it. He claimed that in the 14 years prior to October 1996 approximately 90 per cent of the 100 hourly services were done on location. The licensed aircraft maintenance engineer who generally performed the work for the plaintiff was Roger Gordon Brodie Watson, the managing director of the defendant, who services an aircraft presently owned by the plaintiff. The aircraft log books recording the service history were held by the defendant at Northam.
The plaintiff carried out minor work on the aircraft such as changing spark plugs and oil, and daily inspections, but claimed that he did not do substantial mechanical work.
The plaintiff's practice when having the aircraft serviced was to write out a list of the items requiring attention, or alternatively advise the defendant orally as to the work he required. If during the course of working on the aircraft the defendant considered that additional matters required attention, then unless that work was mandatory, the plaintiff required the defendant to seek his consent before proceeding. The plaintiff believed that prior to September 1996 the defendant had not carried out any work on the carburettor because it was not a mandatory requirement of the 100 hour service.
In September 1996 the plaintiff flew to Perth to attend his son's wedding, and used the occasion to take the aircraft to the defendant's premises at Northam because he had been having trouble with the brakes and tachometer, and the engine had been running rich at low level idling . When he delivered the aircraft to the defendant the plaintiff spoke to Mr Watson and explained that he was having problems with the brakes, and that the engine appeared to be running rich. He required the brakes fixed and asked Mr Watson to check the carburettor float level. Mr Watson supposedly told him that the engine was almost due for overhaul, and because of that asked whether it was worth checking the float level. The plaintiff responded casually that Mr Watson should check the float level if he had time.
When the plaintiff collected the aircraft after about six or seven days he was told by Mr Watson that everything was okay; that he had reset the float level; and that the carburettor was worn and would need work done on it at the time of the overhaul. The plaintiff flew the aircraft back to Mulgul Station without incident. After arriving home it became necessary for him to tighten the clamps on the exhaust muffler and in the course of carrying out that work the plaintiff observed that the carburettor heat control butterfly was slightly open, whereas it should have been closed. The heat control is operated by a Bowden wire, and the plaintiff made a minute adjustment to the Bowden wire to close the heat control. In the process of doing up the holding screw the locking device for the carburettor heat control broke and the plaintiff wound the Bowden wire cable around the carburettor heat control arm to secure it, but stated that this did not involve separating or dismantling the carburettor. He did not see or do anything to the internal components of the carburettor, and claimed that the foregoing was the only work he did on the aircraft between collecting it from the defendant, and the accident.
On the morning of Thursday 17 October 1996 the plaintiff flew the aircraft from Mulgul homestead to Wiluna, and then to Deep Well on Wongawol Station where he landed on a graded road, refuelled the aircraft from a 200 litre drum, and carried out a standard fuel check. He then engaged in the aerial location of cattle until he landed at Junction Bore for lunch . As a result of a request from another station owner, he left Junction Bore to do further aerial work, and had been flying for about 10 to 15 minutes at about 600 - 700 feet when the engine suddenly shut down and the aircraft lost power. The plaintiff checked the fuel selector and ignition control, and applied the fuel primer pump, to try and restore power, but to no avail, and was forced to land. The aircraft had flown a total of approximately 9,000 hours at the date of the accident.
In cross‑examination the plaintiff stated that the defendant had been servicing the aircraft since about 1994 or 1995, and that prior thereto it had been serviced by one Bob Geary who had a business in Bunbury. He confirmed that he was required to keep a pilot's log book, but stated that he misplaced it in May or June 1996. In fact his belief was that one of his family inadvertently destroyed it. In the result he did not have any written record of his involvement with the aircraft before the accident. He confirmed that when he collected the aircraft from the defendant on or about 24 September 1996 and flew back to Mulgul Station it operated "as sweet as could be". There was no problem with the acceleration schedule or the earlier problem of the engine appearing to be running rich. He stated that the return flight took approximately 4/5 hours at a cruising airspeed of approximately 110mph at 2,200rpm and 23 inches of manifold pressure.
The plaintiff stated that on the morning of the accident he flew the aircraft to Wongawol Station to assist in mustering activities which involved the aerial location of cattle, and directing stockmen on the ground. During such activity it was necessary to fly at around 200 - 250 feet and sometimes higher. When he left Mulgul homestead that morning the fuel tank in each wing was full resulting in a total fuel capacity of 360 litres. He agreed that approximately 17 litres of residual fuel in each tank was unusable.
The plaintiff stated that when flying it was his practice to select a tank and exhaust that tank of fuel such that "when that tank of fuel runs out, when the engine stops and coughs and so forth, I will look at my watch and I will say right I've got 2½ or 3 hours out of that tank of petrol. I will switch over to the other one and I say right I'm going to give myself half an hour so I'll use it to within half an hour and then I go and refuel. That's the way I operate". Although the issue was not specifically addressed, it appears that the plaintiff expected to fly for 2½ to 3 hours per tank, depending upon weather conditions.
The plaintiff's evidence was that between leaving Mulgul Station and landing at Junction Bore for lunch, he had been flying for 4 to 4½ hours during which time the engine was running "as sweet as could be". He had been flying for 15 minutes without any indication of difficulty, and the aircraft was cruising when the engine shut down. He stated that upon experiencing the engine shut down he switched from the lefthand to the righthand fuel tank. After the forced landing the plaintiff checked the fuel at the drain points on each wing. The plaintiff was evacuated from the area and did not return until three days later when he searched the aircraft for his log book and cheque book. He returned to the accident site with a Mr Bridge a couple of weeks later. He confirmed that he did not check for any blockage in the fuel tank notwithstanding that on a previous occasion, whilst mustering at Mt Edgar Station via Marble Bar, he had experienced a blockage when a hornet got stuck in the fuel tank vent.
The plaintiff stated that he believed that Mr Watson had carried out a 50 hour service in September 1996. His recollection concerning the work required was that there was a broken brake line which he was unable to repair, and a faulty tachometer, but "that's about all I remember apart from suggesting to him that if he had time would he have a look at the float level for me".
When it was put to the plaintiff that his practice was to personally carry out repairs, he stated that he limited his activities to matters external to the engine. He stated that he concluded that the engine was running rich prior to the service because it was puffing black smoke when idling. It was not flooding. He agreed that there were previous occasions when the engine had been running rich and required adjustment, including the replacement of the needle and seat, which work was carried out on the station by Bob Geary.
The plaintiff's attention was directed to page 29 of Exhibit 1 which he confirmed correctly recorded the work that he requested to have done in September 1996. He confirmed that between the service and the accident he would have used the aircraft for normal purposes around Mulgul Station.
The plaintiff denied doing any work on the carburettor between the date of the service and the accident, and in particular denied replacing the split pin with a piece of wire, or applying solder to the needle. His attention was drawn to a document appearing at page 12 of Exhibit A which recorded an order he placed with the defendant between the service and the accident, for a needle and seat and an accelerator pump assembly. The plaintiff did not immediately recall placing the order, and indicated that he would not have ordered the parts for personal use, but that because of his remote residential location he was in the practise of carrying such parts so that they would be readily available for use by aircraft engineers working on the aircraft on location. It was for that reason that he had always carried external small parts for the engine. He confirmed that he had a good mechanical working knowledge. It appears that the plaintiff could recall his intention to order a needle and seat when he took the aircraft to be serviced. He confirmed that during the time he had had the aircraft (approximately 8,000 flying hours) there had only been one occasion when it had been necessary to replace the needle and seat, that being an in-field service by Mr Geary. He denied that he had ever worked on the carburettor.
The plaintiff recollected that during the course of discussing the supply of parts with him, Mr Watson volunteered information concerning the correct float setting for the carburettor. He confirmed that when placing the order for the carburettor parts he requested they be supplied as soon as possible, and stated that the reason was that he was going down to Fortron gold mine to pick up other parts, and wished to collect all the parts at that time. The forced landing occurred before the parts arrived.
The plaintiff stated that he had made an adjustment to the carburettor heat control butterfly because he noticed it required attention when he had been removing the cowls, but pointed out that the heat control and carburettor were separate items.
Some time after the forced landing the plaintiff telephoned Mr Watson to advice him thereof, and he agreed that he told Mr Watson that there had been engine failure which could have been due to fuel problems. By fuel problems he was referring to a possible fuel starvation in the venting system of the fuel tanks. As he put it, "if that vent gets blocked up air can't get in to replace the fuel. You get a vacuum in the fuel tanks, and the fuel ceases to flow. On a Cessna aircraft its all done by gravity. There are no pumps or any mechanical aids to the fuel getting to the carburettor. Its by - purely by gravity and if that vent becomes blocked you get a vacuum in the tank and you just run out of fuel". That was the type of problem that he had experienced on the earlier occasion at Mount Edgar Station. He agreed that in discussion with Mr Watson he also speculated that an electrical fault was a possible cause of the sudden engine failure, but on reflection did not regard that as a likelihood. He also agreed that he discussed camshaft difficulties as a possible cause of the problem, although again he stated that on reflection he had discounted that as a likely cause.
The plaintiff's attention was drawn to a facsimile that he forwarded to Mr Watson approximately a month prior to trial (Exhibit B). He stated that he sent the transmission to Mr Watson because he did not believe the accident was his fault, and expressed the view in the facsimile that "the problem seemed more in line with fuel starvation caused by a blocked fuel tank vent". The transmission recorded that the circumstances relating to the loss of power were almost identical to the loss of engine power at Mount Edgar Station in 1981.
The plaintiff stated that about two weeks after the accident he attended at the crash site with Mr Bridge, and upon inspection of the aircraft noted that the fuel selector switch was forced in the off position, whereas his recollection was that the position was otherwise immediately after the accident, when he had been unable to turn the fuel selector off. The plaintiff confirmed that considerable work was done to the aircraft in approximately May 1993 following a forced landing caused by diesel fuel contamination, but was not in a position to say what work was done to the engine on that occasion, and in particular whether any work was done on the carburettor. It would be surprising if that was not the case.
In re‑examination the plaintiff confirmed that he always kept spare parts for the aircraft, including a propeller seal, a set of magneto points, battery regulator, fan belt, regenerator brushes, exhaust valves, seals, push rod guards, carburettor needle and seat, spare tyres and the like.

John McKenzie Bridge

Mr Bridge, formerly a senior aircraft airworthiness surveyor, and a licensed aircraft engineer, was at all relevant times an aviation consultant. His statement of evidence dated 18 April 2000 was received in evidence as Exhibit 3. In that statement Mr Bridge noted that he inspected the aircraft with the plaintiff at the accident site on 29 October 1996, and took samples of fuel from the aircraft's fuel system tank drains and fuel filter bowl drain. He subsequently arranged for another person to drain 56 litres of fuel from both tanks, and that fuel did not reveal any indication of contamination. Mr Bridge stated that initial examination did not indicate any mechanical failure likely to have caused engine stoppage. The carburettor did not show any signs of fuel containment or staining from flooding, which caused Mr Bridge to conclude that the engine was probably starved of fuel prior to the accident. He described the operation of a float type carburettor, noting that if there was malfunction such that the fuel level in the carburettor was too high, it would cause the engine to flood, or if too low, would starve the engine of fuel.
Mr Bridge reported that the carburettor was removed from the engine by Hawker Pacific, and he, together with David Theodore of BASI, Lewis Peake of Hawker Pacific, and Hilton Wilson was present at an inspection of the carburettor at the Hawker Pacific Jandakot premises on 22 November 1996. The carburettor was dismantled and tested by Mr Peake. Mr Bridge stated that examination revealed that the float level shaft, float, float pin, float needle, needle seat housing, needle valve and ball joint gasket were extremely badly worn and in need of replacement. The accelerator pump bucket washer had disintegrated with approximately a third of the bucket washer remaining. There was marking on the float indicating that it had been in contact with the sides of the carburettor bowl, and the float needle had solder build‑up on its top to ensure positive float needle seat contact. There was obvious wear on the shoulders of the needle corresponding to wear in the seat body. It was possible to find a position where the needle remained suspended within the seat body, and Mr Bridge considered that it was possible to cause the worn needle to jam in the worn seat body such that it would have restricted fuel entering the carburettor, or alternatively resulted in flooding. The float level shaft was not split pinned in accordance with required practice, but was retained by a piece of stainless steel lock wire. The appearance of the lock wire and solder suggested that both had been in situ for some considerable time.

Mr Bridge stated that in 24 years in the aircraft industry he had inspected many hundreds of carburettors but could not recall having seen one in such a defective and unserviceable condition. He concluded from the appearance of the carburettor that it had been in that condition for a considerable period of time. He stated that the float level could not be adjusted because of the generally unserviceable condition of the carburettor.
Mr Bridge referred to the manufacturer's manual recommendations, pointing out that it was not possible to rectify a defect in a carburettor without removing it from the engine, and carrying out a disassembly. In particular he asserted that the float level of the carburettor could only be adjusted by removing the carburettor from the engine, separating the body halves, and adjusting the float in accordance with the manufacturer's instructions. He claimed that if the float level required adjustment it was usually because of wear between the rubber or steel needle tip and seat contact, and that it would not be correct to carry out an adjustment of the float level without first inspecting the needle and seat. He acknowledged that some engineers adjusted float levels in situ to save time and money, but pointed out that it was not a satisfactory way to fully assess wear.
It was Mr Bridge's conclusion that the accident was caused by the excessive carburettor wear which resulted in interrupted engine fuel supply, probably due to the float either jamming on the carburettor body, or the needle jamming in the seat body, resulting in fuel starvation. Based on the repeated flooding of the carburettor on testing after the accident, he concluded that there was also the possibility that the engine may have flooded and caused engine failure, although he thought that less likely than interrupted fuel supply.
Mr Bridge's view, relevant to a determination of this controversy, is that a competent repairer would have removed the carburettor for the purpose of adjusting the float level, and separated the body of the carburettor. He should then have seen the state of wear of the components and concluded that the carburettor was defective and unserviceable, requiring substantial remedial work.
He observed that the log book recorded three prior instances of float level adjustment on 16 May 1990, 14 October 1992 and 9 September 1994, and stated that more than one adjustment to the float level between engine overhauls was indicative of a problem with the carburettor, and should have prompted further investigation of the carburettor mechanism by the defendant.
In his evidence Mr Bridge dealt with the contents of his report.
He referred to the solder on the head of the needle stating:
"Its my opinion that no aircraft engineer would place solder on the tip of one of these needles. He would replace the whole needle and seat. I cannot believe any self‑respecting aircraft engineer would do that."
He noted that the gasket was fairly aged but serviceable, stating that it (presumably the carburettor) has been obviously opened and closed a number of times.
Notwithstanding the contents of his report, Mr Bridge seemed prepared to concede that if there was not substantial wear within the carburettor it would have been possible to adjust the float level without removing and dismantling the carburettor.
In cross‑examination Mr Bridge confirmed that his report and conclusions had been based exclusively on an examination of the carburettor, and not upon any statements relating to the circumstances of the accident. He stated that he took into account a test he observed undertaken by Mr Peake which demonstrated that the carburettor flooded without any interference, indicative of the fact that the needle was not seated correctly.
Mr Bridge's understanding of the circumstances of the accident was that immediately prior to the engine shutdown the aircraft was flying at 500ft, and turbulence would have been a factor. It also seemed apparent from his evidence that he was convinced that there would have been significant manoeuvring of the aircraft at the relevant time.
Mr Bridge confirmed that the lock wire holding the carburettor screws in place had been incorrectly fixed.
When addressing wear to the pin Mr Bridge said:
"I've seen a few of these carburettors or parts over the years and overhauled and repaired them myself and have never seen one with the hours it is claimed that this engine has done with that amount of wear."
He confirmed that on preliminary inspection of the aircraft with the plaintiff he ascertained that there was fuel at the fuel filter, but no fuel in the carburettor. He agreed with counsel that if prior to the engine shutdown the aircraft had been flying straight and level with the engine running perfectly, it suggested that the needle and seat was not jammed, and the float was not stuck. He agreed that on an examination of the carburettor he identified some particles or portions of the accelerator pump bucket washer in the fuel bowl, but would not accept that there was a likelihood that if there was a small portion thereof in the float bowl it could be sucked up into the main jet in the carburettor causing a complete blockage of fuel. When pressed he reluctantly accepted that as a possibility. He was quite satisfied that there were marks on the cheeks of the float indicating that it was making contact with the sides of the bowl, but was unable to indicate the contact position in the bowl.
Mr Bridge expressed the view that the testing carried out indicated that the float could have been jamming at any position. He agreed that if the float jammed below the mid‑way point of the fuel bowl it would have created an excess of fuel in the carburettor and would have been unlikely to have caused a sudden cessation of engine power.
Essentially Mr Bridge summarised his views in cross‑examination when he said:
"As I have said before, that carburettor is excessively worn, excessively worn. There's evidence that the float is jamming in the carburettor. You're making a proposal as to where its jammed. I'm saying that it could have jammed in any position at all. It may have jammed with what you're describing as material in the carburettor. You can't prove that, your client can't prove that, I can't prove that but what I can show you is that the carburettor is mechanically unserviceable and is in a position, in a situation where the float will jam and the needle will jam in the seat. Now having said that, if somebody advances that throttle in that position, the mixture will automatically lean and, if it leans, the engine will stop. … And that's what I believe occurred here."
He agreed that the situation he envisaged having occurred would necessarily have required an adjustment by the plaintiff to the accelerator schedule. Clearly he would not have expected the problem to occur if the aircraft had been flying with no alteration at all to the acceleration schedule, but doubted that could be the position - in fact refused to accept position.
Mr Bridge accepted that it would be highly unusual for a licensed aircraft engineer to attempt to solder the needle; use wire instead of a split pin to secure the float to its assembly; and miswire the securing nuts.
He was emphatic that the only proper way to set the float level of a carburettor was in fuel and not in the air, pointing out that if that procedure had been followed, the problems with the carburettor would have been identified. He referred to the Cessna manual and was emphatic that float adjustment required the removal of the carburettor from the aircraft, stating that although there was a practice adopted by some aircraft engineers to adjust the float by simply removing the bottom half of the carburettor:
"All he's doing is adjusting something in the air which the moment its immersed in fuel assumes a totally different situation. If you look at the log books of this aircraft you will see that on three previous occasions this carburettor has been adjusted for the same reasons and nobody has pulled the bloody carburettor off and had a look at it. That is the problem."
Mr Bridge seemed prepared to accept that with a new carburettor there could be a float adjustment in the air, but considered that it was impossible to do so with a carburettor suffering excessive wear. He agreed that if the engine had operated normally for approximately five hours subsequent to the float correction it could be indicative of the fact that the float was properly adjusted.
Mr Bridge claimed that he had excluded the possibility of a venting problem by determining that there was usable fuel in the aircraft, and as the fuel was selected to both tanks the possibility of an unport was remote. He referred to the fact that the documentation suggested that the aircraft had been fitted with tank cap vents subsequent to an earlier problem, and that should have precluded venting problems. He expressed the view that unporting was likely to occur if the fuel selection was not to both tanks stating:
"If you're flying on one tank and you're manoeuvring around the sky, not flying straight level, there is every chance that you can have an unporting situation - and that is, if the aircraft is not coordinated in turns. However, if it is selected to both tanks and the evidence is that equal amounts of fuel were withdrawn from both tanks which would suggest the aircraft had been flown on both tanks selected which would be the logical thing flying at 500 feet. To fly at those sort of altitudes, flying on one selected tank would be quite stupid and Power, to my knowledge, was a fairly experienced pilot."
He agreed that he did not carry out a careful investigation of the venting system to exclude it as a possible cause of the failure.
Dealing further with the issue of unporting, Mr Bridge said:
"Well, one tank, you only select the one tank. If an uncoordinated turn is carried out, you can shift the fuel across the surface of the tank and, as counsel have said, unport the tank and you get air coming through the system."
He considered there was a clear risk of unporting in the practice of running one tank completely dry before switching to the other tank.

Lewis Charles Peake

Mr Peake is an experienced licensed aircraft maintenance engineer and his statement of evidence dated 18 April 2000 was received as Exhibit 6. In addition he produced a new float hinge pin (Exhibit 5). Mr Peake has worked for Hawker Pacific as an aircraft maintenance engineer for approximately 15 years, and had considerable experience in repairing and servicing aircraft carburettors.
In November 1996 at the Hawker Pacific workshop he inspected and tested the carburettor which he described as a fairly common type. He carried out the inspection and testing of the carburettor in accordance with the carburettor manufacturer's recommendations which were contained in the facet aircraft carburettor service manual. He stated that he placed the carburettor on a level test bench to check the float level, and it flooded. He then proceeded to partially dismantle the carburettor to determine the cause of flooding, and by taking a measurement with a 13/64 drill bit discovered that the float level was too high. He concluded that the higher than normal float level was due to excessive wear in the carburettor, and noted that a high float level gives rise to the flooding of a carburettor because of an oversupply of fuel. He recorded that there was particularly severe wear to the float, the pin that held the float to the bracket, and the holes in the bracket the pin penetrated. He concluded that those components should have been replaced, as the extent of the wear could well have affected its operation. He concluded from wear marks on the pontoon of the float that it had been catching on the carburettor fuel bowl. He recorded that the float needle had obvious wear on the shoulders, and was loose fitting in the seat. The needle, valve and tab were also badly worn, and the needle had solder on it. The pin was held in place with lock wire rather than a split pin. There was, however, no indication that the carburettor had been incorrectly assembled. He regarded the wear to the carburettor as particularly bad, stating that it was unusual to see wear of that extent in a carburettor.
Mr Peake considered that the wear had developed over a significant period of time. He set out the manner in which he bench tested the carburettor in accordance with the manufacturer's instructions to determine that it was flooding, and was of the view that the poor condition of the needle and seat was the cause of the flooding.
On 17 April 2000 Mr Peake carried out an inspection and testing of the float for bowl clearance, and stated that the float failed the test as he was unable to run a drill rod freely between the float and the bowl. He stated that contact could result in the float jamming closed, resulting in fuel starvation. Alternatively, the float could jam open, causing the carburettor to flood.
Mr Peake expressed the view that in order to properly adjust the carburettor float it was necessary to remove the carburettor from the engine, dismantle it, and disassemble the needle and seat so that it was possible to inspect the needle and seat prior to adjusting the float level. He conceded that it was possible to adjust the float by bending the tab without taking the needle and seat out, but did not consider that proper practice. He stated that it was not good practice to check and adjust the float level whilst the carburettor was still attached to the engine.
In cross‑examination Mr Peake indicated that it would take approximately three quarters of an hour to an hour to remove the carburettor from the engine. He confirmed that his testing demonstrated that the carburettor flooded badly, and it does not seem that he was prepared to accept that the engine could have run properly with the carburettor in its tested condition. He acknowledged that if the engine was running properly it was indicative of the fact that the float, needle, valve and seat were correctly functioning, with the result that there would be a constancy of fuel in the bowl.
When it was put to Mr Peake that for the needle to go from a position of normal operation to jamming, an adjustment of the throttle would be required, he responded that if the aircraft went into a bank or turned it was quite possible because of the extent of wear, for the needle to jam. He agreed that he had never heard of a situation when a plane which was flying straight and level with the engine operating normally, encountered a situation when the carburettor float moved from its position of constancy in the fuel bowl, to shut off the fuel.
Mr Peake appeared to favour the view that if the carburettor was to malfunction, it was likely to have jammed in the open position (that is with fuel flowing in causing flooding) rather than in a position of fuel starvation. It seems that he was prepared to acknowledge in that situation it was unlikely to result in an engine shut down, or at least not without some indication to the pilot that there was a problem.
Mr Peake identified the position in the fuel bowl where it appeared that the float had been touching, stating that was the point of contact where the float was likely to jam, and that if it in fact jammed in that position, it was probable that it would result in excess fuel, rather than restricted fuel. He agreed with the proposition that if the engine had been running rich and that problem was corrected by a float adjustment such that the engine then ran normally, there would be no reason to further examine the carburettor.
Mr Peake expressed the view that the aircraft would need to be involved in some fairly steep turns to cause the float to jam in the closed position. He accepted that it was appropriate in adjusting the float seating, to use a screwdriver to set the float. He agreed that the use of a 13/64 drill bit to measure the aperture between the top of the float and the carburettor gasket was appropriate. He also agreed that fragments of a disintegrating washer might enter the main jet restricting the fuel flow to the engine, although he pointed out that the entrance to the main jet was baffled.

Ivan Frederick George Burrows

Mr Burrows a senior airworthiness inspector with the Civil Aviation Safety Authority is a licensed aircraft engineer, having obtained his trade certificate approximately 30 years ago. His statement dated 17 April 2000 was received as Exhibit 7.
In his statement Mr Burrows advised that he attended Hawker Pacific's premises where Mr Peake showed him the carburettor. He had no independent recollection of his inspection of the carburettor, but after refreshing his memory from correspondence that he forwarded to the defendant, was able to recall that there was solder on top of the float needle; wear in the hinge pin of the float; and wear in the holes of the bracket holding the carburettor pin. He did not observe any tests of the carburettor.
Mr Burrows agreed that it was possible to adjust the float level of a carburettor in situ, but indicated that it would be difficult, and considered that the carburettor should be removed from the aircraft and split to properly carry out a float level adjustment. Following adjustment it should be tested in accordance with the manufacturer's requirements to determine that the needle and seat were not leaking. From the inspection he concluded that the carburettor was unserviceable.
In cross‑examination Mr Burrows recalled that there was wear on the hinge pin and the hinge itself, damage to the accelerator pump bucket, solder on the needle, and locking wire used in the hinge pin.
Mr Burrows stated that he had about 15 years practical experience working on engines such as the one in the aircraft. He indicated that there were strict limits on the work that a private pilot could carry out on his aircraft, and that a private pilot was precluded from working on the engine. He stated that the throttle on the aircraft was a Bowden controller with a push/pull function controlling the acceleration schedule. He agreed that the float was high in the bowl of the carburettor in the idle position, and depressed when increased fuel was required. He had never before observed solder on a needle, and stated that he would be absolutely horrified if a licensed aircraft engineer had been responsible for its application. Similarly he agreed that it would be inappropriate and unusual for a licensed engineer to use wire, rather than a split pin, to secure the float pin. He was prepared to accept that a small portion of the leather pump washer in the fuel bowl could enter the main jet and cause fuel starvation.

Roger Gordon Brodie Watson

Mr Watson is and was at all relevant times the defendant's managing director and chief engineer, having held that position since August 1995. He stated that the defendant carried on the business of aircraft maintenance including engine overhauls, rebuilds, paint jobs, and general maintenance. His statement of evidence was received as Exhibit C.
Mr Watson qualified as an aircraft maintenance engineer in 1993 following a four year apprenticeship. During his apprenticeship, and for several years after qualifying he was employed by Clearview Aviation, becoming a part owner of that business which became Northam Air Services Pty Ltd in late 1995. He had dealings with the plaintiff whilst he was working for Clearview Aviation, and in 1995 the plaintiff became a customer of the defendant company which has since carried out various work and services on the aircraft. Mr Watson stated that in about mid‑September 1996 the plaintiff arranged for the aircraft to be booked in for a 50 hour service and to repair a flat brake, and expressed concern that the engine was possibly running slightly rich. A 50 hour service included a check of the tyres, battery, brakes, fluids, dressing the propeller, checking the oil, oil filter and air filter, and other minor items, but did not require specific attention to the carburettor. The flat brake problem was attended to, and during the course of a cylinder compression check it was discovered that there was a lack of compression in one of the cylinders. As a result that cylinder was removed and found to have a worn exhaust valve and guide, resulting in an inadequate sealing and low compression. Remedial work was undertaken.

Mr Watson pointed out that low compression in a cylinder would produce symptoms similar to the engine running rich. Although he considered that the correction of the compression problem would have eliminated such symptoms, he checked the carburettor float by removing the lower portion of the carburettor. That enabled him to see the float and hinge mechanism, the gasket, and the accelerator pump, including the leather washer on the pump.
Mr Watson found the float level was marginally out, and as a consequence carried out a very minor adjustment, using a tool to make a small bend to the metal tab attached to the float hinge mechanism. He stated that the manner in which he adjusted the float level was in accordance with manufacturer's requirements. He also determined by blowing into the fuel inlet pipe that the needle was sealing properly.
Mr Watson noticed some movement with the float on the hinge mechanism indicating that the hinge or pin was worn, but the movement was not to the degree that suggested rectification could not await a complete overhaul in a further 50 hours flying time. He did not notice wear or damage to the gasket, and observed that the accelerator pump washer was intact and serviceable. He could not specifically recall the float pin, but stated that if it was secured by wire rather than a split pin he would have observed and rectified it. Because he was simply making an adjustment to the float, and not carrying out a service or overhaul of the carburettor, there was no requirement for him to remove and examine the needle and seat. Consequently he reassembled the carburettor, tightening and placing locking wire on the retaining screws.
On completion of the work the engine was ground tested up to full power with no indication of it running rich or flooding. Mr Watson could not recall seeing any solder on the head of the needle, although he did not specifically inspect it. When the plaintiff collected the aircraft Mr Watson informed him that the carburettor required attention but that it was serviceable up until the compulsory overhaul. He denied placing solder on the needle, using lock wire instead of a split pin, and incorrectly applying the lock wire to the retaining screws.
Mr Watson recalled that about a week after taking delivery of the aircraft the plaintiff rang expressing the view that the engine was still running a little rich. Mr Watson told him that that could be caused by an incorrect carburettor float level, worn main jet nozzle, or economiser valve failure. It was apparently at about that stage that the plaintiff asked Mr Watson to order him a new needle, seat, and accelerator pump, although those items were not delivered before the crash. When the plaintiff reported the crash to Mr Watson he advised that he had tried everything to get the engine restarted, including changing the fuel tanks, pumping the primer, operating the throttle, and operating the magneto switches.
Mr Watson examined the aircraft at Jandakot several weeks after the accident. He noticed that two retaining nuts were loose on the carburettor mounting flange, and some of the lock wire on the screws securing the head of the carburettor to the bowl had been wired backwards, which was not the result of his work on the aircraft. He thought that the nuts on the mounting flange must have been loosened after the accident, for if they had only been finger tight whilst the engine was operating, they would have rattled off.
On 3 April 2000 Mr Watson examined the carburettor at the plaintiff's solicitors' office and was quite amazed to see the degree of damage to the leather bucket on the accelerator pump, which he considered could only have occurred as a result of improper assembly. He stated that there was no way that he would put the carburettor back together with the washer in such a damaged condition.
At the time the defendant carried out the work on the aircraft the people in its employ were an administrative manager, a leading hand who was a qualified licensed aircraft maintenance engineer, a fourth year apprentice, a second year apprentice, and Mr Watson. The leading hand worked on the brake system, and Mr Watson worked on the engine.
Mr Watson was emphatic that it was a common practice to adjust the float level of a carburettor in the air. He described the carburettor as a very basic type, stating that the main problem that was experienced with that type was flooding, which was easy to detect.
Mr Watson was referred to the defendant's order job No 280, being document 12 in Exhibit A, which recorded the plaintiff's request for a needle and seat and accelerator pump to be sent on Overnighters to Fortron Goldmine "ASAP", and he stated that when the order was placed, the plaintiff wanted the parts before he left Mulgul to go to Wongawol.
In cross‑examination Mr Watson confirmed that the defendant had a carburettor bench test facility, and stated that at an overhaul most of the working parts of a carburettor were replaced with new parts. He agreed that the defendant retained the aircraft for about a week in September 1996, and that so far as remedial work was concerned, time was not a problem. He agreed that when the plaintiff brought the aircraft to the defendant he said that it was running rich at low idle, but denied that the plaintiff specifically requested that he check the float level on the carburettor. He agreed that he told the plaintiff when he collected the aircraft that the carburettor was worn and work was required on it in the near future.
Mr Watson was referred to the defendant's records concerning the work performed in September 1996 and estimated that the work on the carburettor took something of the order of a half to one hour. He agreed that it would have taken less than an hour to remove the carburettor from the aircraft. He stated that he did not remove the carburettor, but checked it in the manner in which he did, because it was quicker.
Mr Watson was referred to entries in the log book which demonstrated that on 16 May 1990, 14 October 1992 and 9 September 1994 the carburettor required servicing because of problems with the float level and needle assembly. He agreed that when he worked on the aircraft in September 1996 he was aware of that history, but stated that since the history was one of flooding it did not suggest to him that the carburettor should be removed. At the time he was working on the aircraft he was essentially checking to see if the float level was too high.
Mr Watson agreed that as at 1996 he was, comparatively speaking, inexperienced as an aircraft mechanical engineer. He agreed that the condition of the carburettor when inspected following the forced landing showed that it was unserviceable. When it was put to him that the relevant manual dealing with the carburettor, directed its removal for checking, Mr Watson stated that it was an overhaul manual, and that he was not performing an overhaul of the carburettor. He indicated that during the life of the carburettor it was not required to be separated. He agreed that he had not followed the steps set out in the manufacturer's manual for servicing the carburettor, pointing out that he was not carrying out an overhaul but simply addressing a specific issue, and that the steps he had taken were entirely appropriate to address that issue.
Mr Watson agreed that because of wear, the float pin was unserviceable in September 1996, but pointed out that the engine required a complete overhaul in a further 50 hours, and that the carburettor was not an item that generally had wear problems. He stated that when he separated the carburettor he was able to observe the float and there was no abnormal wear mark on it. He could also see the accelerator pump in its entirety. He agreed that the accelerator bucket was old and exhibited the expected wear having regard to its age. He confirmed that when the plaintiff collected the aircraft he was told that the carburettor was worn and required overhaul.
Mr Watson's answers to interrogatories dated 14 September 1999 were received in evidence (Exhibit D).

Hilton Richard Wilson

Mr Wilson, an aircraft insurance loss adjustor, stated that he qualified as a licensed aircraft engineer in 1960. His statement of evidence made February 2000, and a further supplementary statement dated April 2000, were received as Exhibits E1 and 2.
Mr Wilson disagreed with the proposition that the engine failure was caused by fuel starvation resulting from excessive wear in the carburettor. He accepted that various carburettor components were worn, but considered that the extent of wear was consistent with the fact that the carburettor was nearing the end of its serviceable life. He agreed that the wear had occurred over an extended period of time, save in respect to the disintegration of the accelerator pump washer, which he thought probably occurred between September 1996 and the forced landing.
Essentially the view he expressed was that as the defendant was providing an infield minor adjustment to the float level of the carburettor, a full examination and replacement of worn parts was not appropriate. He expressed the view that when the only requirement is to make an infield adjustment to the float level of the carburettor, it was not necessary to remove it from the engine and carry out a total disassembly. The removal of the lower half of the carburettor to check and adjust the float level was a common and accepted practice when carrying out infield adjustment.
He would not accept that the engine failure resulted from jamming of the needle, or the float becoming stuck restricting the supply of fuel to the engine, principally because prior to the failure, the aircraft had been flying in a cruise configuration for some minutes, and the throttle would have been in a constant position. He stated that because of the design of the float there was very little chance of it becoming jammed on the wall of the bowl.
Mr Wilson agreed that he had a close relationship with Mr Watson.

Findings of fact

The contract between the parties

The starting point to a resolution of this controversy is to identify the terms of the contract for work and labour entered into between the parties. The evidence discloses that the contract was not as expansive as pleaded in the statement of claim. The plaintiff's evidence was that when he delivered the aircraft to the defendant it was essentially for the purpose of correcting a brake problem and a faulty tachometer. Additionally, the plaintiff advised the defendant that the engine appeared to be running rich and requested that the defendant check the carburettor float level "if it had time". It also appears that there was to be a 50 hour service which required the checking of minor items. Although that seems to have been the extent of the agreed work to be undertaken, the defendant also rectified a cylinder compression problem which was identified during the service. The work agreed to be carried out and addressed is recorded in the defendant's worksheets at pages 30 and 31 of Exhibit 1. The plaintiff agreed that the maintenance sheet at page 29 recorded the work agreed to be done.
It is to be noted that the plaintiff's evidence inter alia was to the effect that unless remedial work was mandatory the defendant was to perform only those services requested by the plaintiff. I am satisfied that upon completion of the work Mr Watson advised the plaintiff that the carburettor required attention but that it could wait until the compulsory overhaul in a further 50 hours flying time.
The defendant performed its contractual obligation.

Was the defendant negligent in not removing and completely dismantling the carburettor?

There is no dispute on the evidence but that there was considerable wear to the carburettor and that objectively it was unserviceable. Clearly had the defendant removed, dismantled, and bench tested the carburettor, that would have been apparent. The issue, however, is whether the defendant had a duty to do those things.
The burden of the evidence of Messrs Bridge and Peake was that although it was the practice of some aircraft engineers to adjust the float level in situ, proper practice required the removal, disassembly and bench testing of the carburettor when adjusting the float level because the adjustment would then be carried out in operating conditions, and a proper inspection of the carburettor components could be carried out.
Mr Watson was firmly of the view that it was appropriate practice to carry out a float adjustment in situ, and that view was endorsed by Mr Wilson.
Having regard to the nature of the plaintiff's request to the defendant concerning the carburettor, together with the fact that adjustment of the float level in situ is not only possible but common practice, and that the engine operated normally following the float level adjustment indicating that the level was satisfactory, I am not persuaded that the defendant was negligent not removing and dismantling the carburettor. As Mr Watson stated, he did not perform and was not requested to perform an overhaul of the carburettor, which was required to be undertaken in a further 50 hours flying time.

Was work done on the carburettor subsequent to the defendant's service?

Mr Watson gave evidence that when he serviced the aircraft he did not observe that the float pin was secured by wire rather than a split pin, and when he replaced the carburettor bowl the leather bucket on the accelerator pump was intact, and he correctly lock wired the screws securing the head of the carburettor to the bowl. I accept that evidence. It is improbable that an aircraft engineer would have replaced the bowl if the accelerator pump bucket was damaged, or damaged it when replacing the bowl, and would have incorrectly lock wired the holding screws. It is more likely those problems occurred subsequent to the service. It is to be remembered that the plaintiff rang Mr Watson subsequent to the service suggesting that the engine was running rich, and it is probable that having basic mechanical skills he endeavoured to correct that problem.

How did the accident happen?

This is the issue central to a resolution of the controversy, because the plaintiff carries the burden of establishing not only that the defendant was negligent not removing and dismantling the carburettor and identifying and advising that it was unserviceable, but additionally must demonstrate that the negligence was causative of the accident. Put simply that there was a breach of duty by the defendant giving rise to loss.
The plaintiff seeks to prove that because of the excessive wear in the components of the carburettor the float and/or needle jammed in a position causing starvation of fuel, and consequently cessation of combustion in the engine.
Although the absence of the pilot's log book prevents an accurate calculation of post‑service engine operating time, the evidence does establish the following:
(i)Subsequent to the float adjustment by the defendant the engine was ground tested up to full power and determined to be running properly.
(ii)After taking delivery of the aircraft the plaintiff flew it back to Mulgul Station which took some 4/5 hours, during which time the engine was operating "as sweet as could be".
(iii)Between the arrival of the aircraft at Mulgul Station and the date of the accident the plaintiff used the aircraft for normal purposes and apart from the suggestion of richness of mixture, about which he spoke to Mr Watson, it appears that the aircraft flew normally.
(iv)On the day of the accident the plaintiff had been flying the aircraft for 4/4½ hours prior to cessation of power and the engine was operating normally.
All that indicates that the defendant had correctly adjusted the float level and that the carburettor was functioning as it should. It is important to appreciate that the evidence that the motor was operating normally was provided by the plaintiff who because of his mechanical knowledge was in a position to give an accurate assessment.
The conclusion that the engine stopped because of fuel starvation due to the jamming of one of the carburettor components is necessarily inferential; and one suspects that in drawing that inference Mr Bridge was clearly influenced by the anomalies and excessive wear discovered within the carburettor on inspection. It is likely that detracted from a proper consideration of other potential causes. When the carburettor was bench tested the problem evident was one of flooding, but the plaintiff had not experienced a difficulty with flooding prior to the service; there was no indication of flooding when the aircraft was examined by Mr Bridge subsequent to the accident; and it does appear that it was a lack of fuel rather than an excess thereof that caused the problem. Mr Bridge and Mr Peake accept, and indeed it is axiomatic, that if the engine is operating normally, the carburettor is functioning correctly.
The plaintiff's evidence was that for about 10 to 15 minutes prior to the cessation of engine power the aircraft had been cruising at a steady air speed, at a height of approximately 600 to 700ft. During that time there was no alteration to the accelerator schedule, and there was no suggestion of turbulence. It is therefore unlikely that there would have been any movement of the needle or float within the carburettor, and hence no reason to suppose that either of those parts jammed causing a restriction to the flow of fuel to the engine. Mr Bridge would not accept that there was no alteration to the acceleration schedule immediately prior to the cessation of engine power, clearly because that was difficult to reconcile with his hypothesis.
It is unfortunate that other possible causes do not appear to have been properly investigated. Mr Bridge indicated that a third party drained some 56 litres of fuel from the aircraft, but the evidence does not establish whether that fuel came from one or other of the tanks, and/or whether that was the total usable fuel left in the tanks. The evidence does demonstrate that portion of the disintegrated bucket washer was found in the fuel bowl, and that there was the potential for such material to enter the main jet and cause fuel blockage. It was clear from the plaintiff's evidence that it was his practice to fly on and exhaust all the fuel in one tank before switching to the remaining tank, a practice which Mr Bridge denigrated in the strongest terms because of the potential to cause unporting and a resultant cessation of the supply of fuel to the engine.
In Jones v Dunkel (1959) 101 CLR 298 at 304 his Honour Dixon CJ said:
"In an action of negligence … the plaintiff must fail unless he offers evidence supporting some positive inference implying negligence and it must be an inference which arises as an affirmative conclusion from the circumstances proved in evidence and one which they establish to the reasonable satisfaction of a judicial mind. It is true that 'you need only circumstances raising a more probable inference in favour of what is alleged.' But 'they must do more than give rise to conflicting inferences of equal degree of probability so that the choice between them is mere matter of conjecture.' "
The cause of the cessation of engine power is a matter of conjecture. I am not persuaded that it was caused by the malfunction of a component of the carburettor.
The plaintiff's claim is dismissed.