The Avgas contamination event that happened over Christmas 1999 caught everyone by surprise. It had not been seriously considered as a potential hazard to aviation anywhere in the world, therefore the consequences had not been considered. The reasons behind why the fuel became contaminated were unexpected. Mike Watson, one of a team of transport safety investigators who had the task of sifting through an overwhelming amount of data and publishing the final report, gives some insight.

No one was hurt as a result of contaminated aviation fuel, and there were no accidents that could be attributed to a loss of power caused by fuel contamination. At the time of the crisis the fuel refiner responded immediately and recalled all Avgas that had been manufactured at the refinery, and CASA grounded all Avgas powered aircraft that could have been contaminated until it was known that they were safe to fly.

The chemical contaminant is now known to have been ethylene diamine. At the time of the event, there was a concerted effort to define what the contaminant was (concentration in the Avgas was low); how the contaminant had got there; and what the contaminants behaviour would be in an aircraft fuel system.

In the initial response a method to guarantee aircraft would be safe again was developed, and a testing process to detect ethylene diamine was also developed in a number of weeks. Components for the test kits were sourced from all over the world.

The ATSB's investigation looked at what had happened. It looked at what could have prevented it from happening and why it didn't. It also looked at lessons that could be learnt and applied to other aviation systems. This included what would have happened if a similar contamination event occurred in a large turbine-engine passenger aircraft operating with contaminated jet fuel.

The main defence against any safety-critical system failure in an airliner is to have backup, or redundant, systems for any system that is essential for safe flight. The problem with fuel storage and supply systems in an aircraft is that they simply don't have a redundant backup. If fuel is contaminated, the contaminant will be supplied to all an aircraft's engines at the same time and could make them all unreliable at the same time.

As the primary defence of a redundant system isn't available to protect against the safety critical problem of fuel quality, we could reasonably expect there to have been a number of fuel quality related accidents in the recent past; however, that was not so. This can only be attributed to a highly reliable system for manufacture and distribution of aviation fuels, with a well-managed quality control processes.

Despite this, it is clear that complacency on the part of any group that has a responsibility towards maintaining fuel quality, be they refiner, distributor, regulator or consumer, can have catastrophic consequences.

This Avgas contamination event must be seen as a clarion call to highlight an aspect of the system of safe aviation that is more vulnerable to abuse or neglect than most other safety critical aviation systems.

Avgas contamination investigation report released

The Australian Transport Safety Bureau (ATSB) released its report on the contaminated aviation gasoline (Avgas) investigation at a media conference on 30 March 2001. The investigation followed the grounding in January 2000 of thousands of piston engine aircraft across eastern Australia when a black gunk was found in fuel systems.

The investigation found that a very small amount of an anti-corrosion chemical that was not removed in Mobil's Avgas refining process in late 1999, and not detected by the usual tests, led to the safety problem.

The ATSB made 24 separate recommendations as a result of its investigation that included recommended safety actions for Mobil Oil Australia, US and UK fuel standards bodies, the Civil Aviation Safety Authority, and other Australian regulatory organisations.

ATSB Executive Director Kym Bills told the media that the scale of the Avgas contamination was an unprecedented event anywhere in the world and was unexpected in such a mature industry as fuel refining. As a result, it caught the refiner and regulators by surprise and also revealed deficiencies in international fuel standards.

The investigation found that a temporary variation in the production process at Mobil's Altona refinery in late 1999 involving problems with reduced caustic wash and increased acid carry over, led to an increased dosage of an alkaline anti-corrosion chemical by a contractor. This was not totally removed from the final Avgas. The normal tests for the quality of Avgas did not pick up the very small concentration of the chemical contaminant in the Avgas that was sufficient to react with brass in aircraft fuel systems and form a black gunk that clogged them.

Mr Bills said it was not the ATSB's role to ascribe blame to any party. The task was to uncover the facts including all of the significant contributory factors (including weaknesses in defences), and then to publish findings and recommendations in a report.

Accordingly, it was important that relevant parties learnt from the identified safety deficiencies and acted promptly on the 24 recommendations made to reduce the chances of a recurrence, either with Avgas or jet fuel.

On 3 July 2009, the Australian Transport Safety Bureau (ATSB) was notified that a SAAB Aircraft Company 340B (SAAB), registered VH-ZLW, had commenced its take-off roll along the runway 25 left edge lights at Sydney Kingsford Smith Airport, New South Wales. This was one of three occurrences over the previous 2 years that involved aircraft commencing take-off on the runway edge lighting.

In addition, within the previous 2 years the ATSB investigated two other occurrences involving pilot misidentification of runway alignment cues or lack of those cues during take-off. All five Australian misaligned take-off and landing occurrences involved aircraft with weights greater than 5,700kg and three of the six occurrences involved scheduled regular passenger transport (RPT) operations. The remaining two occurrences involved charter operations.

This research investigation examined each of these occurrences and relevant international occurrences to identify the common factors associated with misaligned take-off and landing occurrences.

After reviewing the Australian and international occurrences, eight common factors were identified that increased the risk of a misaligned take-off or landing occurrence. The factors included: distraction or divided attention of the flight crew; confusing runway layout; displaced threshold or intersection departure; poor visibility or weather; air traffic control clearance/s issued during runway entry; no runway centreline lighting; flight crew fatigue; and recessed runway edge lighting.

A significant proportion of all occurrences reported to the Australian Transport Safety Bureau (ATSB) involve aircraft striking wildlife, especially birds. This report provides aviation birdstrike and animal strike occurrence data for the period 1 January 2002 to 31 December 2009. It also describes the results of an ATSB survey of aerodromes concerning current wildlife control measures.

Reported birdstrikes have been generally increasing since 2002. In 2009, there were 1,340 birdstrikes reported to the ATSB. For high-capacity aircraft operations, reported birdstrikes have doubled from 2002 to 2009. However, taking into account an increase in aircraft movements, this increase is modest and is probably accounted for by a generally improving reporting culture within this time.

Birdstrikes have increased for the period of study in every Australian state and territory. Queensland, New South Wales, the Northern Territory and Western Australia have the highest birdstrike rates. The higher birdstrike numbers for Queensland and the Northern Territory may be related to bird populations within the tropics, while New South Wales has the highest number of major aerodrome aircraft movements in Australia.

Most birdstrikes occur within the confines of aerodromes (less than 5 km). Major and regional towered aerodromes had significantly higher rates of reported birdstrikes than General Aviation Airport Procedures (GAAP) aerodromes, and had considerably increasing rates from 2002 to 2009. GAAP aerodrome birdstrike rates do not appear to have changed.

Engine ingestion makes up 11 per cent of all birdstrike occurrences in high-capacity air transport for the 8- year period, and the highest number of damaging birdstrikes occurs in high-capacity air transport. Birdstrikes causing multiple parts damaged were not common throughout the period. General aviation had the highest proportion of damaging birdstrikes, with almost 24 per cent of birdstrikes causing damage. Aeroplane wings and helicopter rotor blades are the most commonly damaged aircraft components across all operational types, particularly in general aviation. There have been eight occurrences from the period of 2002-2009 that have resulted in serious aircraft damage, and four that have resulted in injury.

The most common types of birds struck by aircraft were lapwings/plovers, bats/flying foxes, galahs, and kites. Not surprisingly, larger birds were more likely to result in aircraft damage.

Animal strikes were relatively rare. High-capacity air transport had the highest average with 11.5 animal strikes per year, with general aviation having the second highest average with 9.3 animal strikes per year. The most common animals involved in strikes were hares/rabbits, kangaroos, wallabies, and foxes/dogs. Damaging strikes mostly involved kangaroos, wallabies and livestock.

Bird hazard control at aerodromes was found to be mostly related to the control of grass height (short or long) and growing specific plants or grass, and the daily or weekly use or auditory deterrents, especially car horns and shotguns.

Forty-four per cent of all accidents and over half of fatal accidents between 1999 and 2008 were attributed to private operations. These figures far surpassed the proportions for any other flying category, even though private operations contributed to less than 15 per cent of the hours flown in that decade.

This report aims to identify the factors contributing to fatal accidents in private operations and how these factors differed from non-fatal accidents. This was achieved through exploring common occurrence types (what happened), contributing factors (why the accident happened), contributing pilot errors, and aircraft and pilot characteristics.

Three occurrence types accounted for the majority of fatal accidents: collision with terrain (90%); loss of control (44%); and wirestrikes (12%). When all incidents and accidents are taken into account, the likelihood of being killed was about 36 per cent for a collision with terrain occurrence, 30 per cent for loss of control occurrences, and about 50 per cent for a wirestrike. For non-fatal accidents, there was greater variability in the common occurrence types - forced landings, hard landings, problems with the landing gear, and total power loss/ engine failure were also common.

Problems with pilots' assessing and planning were identified as contributing factors in about half of fatal accidents in private operations, and about a quarter involved problems with aircraft handling. Other contributing factors associated with fatal accidents to a smaller extent were visibility, turbulence, pilot motivation and attitude, spatial disorientation, and monitoring and checking. Non-fatal accidents were just as likely to involve aircraft handling problems, but had fewer contributing factors than fatal accidents.

Action errors and decision errors were both common to fatal accidents. Violations, while less frequently found, were mostly associated with fatal accidents.

In light of the contributing factors that were associated with fatal accidents in private operations, the report provides advice to pilots for improving the odds of a safe flight. Pilots are encouraged to make decisions before the flight, continually assess the flight conditions (particularly weather conditions), evaluate the effectiveness of their plans, set personal minimums, assess their fitness to fly, set passenger expectations by making safety the primary goal, and to seek local knowledge of the route and destination as part of their pre-flight planning. Also, becoming familiar with the aircraft's systems, controls and limitations may alleviate poor aircraft handling during non-normal flight conditions. Finally, pilots need to be vigilant about following rules and regulations that are in place - they are there to trap errors made before and during flight. Violating these regulations only removes these 'safety buffers'.

The ATSB receives around 15,000 notifications of aviation occurrences each year; 8,000 of which are accidents, serious incidents and incidents. It is from the information provided in these notifications that the ATSB makes a decision on whether or not to investigate. While further information is sought in some cases to assist in making those decisions, resource constraints dictate that a significant amount of professional judgement needs to be exercised.

There are times when more detailed information about the circumstances of the occurrence would have allowed the ATSB to make a more informed decision both about whether to investigate at all and, if so, what necessary resources were required (investigation level). In addition, further publicly available information on accidents and serious incidents would increase safety awareness in the industry and enable improved research activities and analysis of safety trends, leading to more targeted safety education.

To enable this, the Chief Commissioner has established a small team to manage and process these factual investigations, the Level 5 Investigation Team. The primary objective of the team is to undertake limited-scope fact-gathering investigations, which result in a short summary report. The summary report is a compilation of the information the ATSB has gathered, sourced from individuals or organisations involved in the occurrences, on the circumstances surrounding the occurrence and what safety action may have been taken or identified as a result of the occurrence.

The summary reports detailed herein were compiled from information provided to the ATSB by individuals or organisations involved in an accident or serious incident between the period 1 April 2010 and 30 June 2010.

The aviation industry has been slow to acknowledge the risks associated with ground operations. While most occurrences on airport aprons and taxiways do not have consequences in terms of loss of life, they are often associated with aircraft damage, delays to passengers and avoidable financial costs to industry. The focus of this report is to examine ground occurrences involving high-capacity aircraft operations.

This report examines occurrences involving ground operations and foreign object debris that occur at Australian airports which receive high-capacity aircraft. It uses occurrence and investigation data reported to the Australian Transport Safety Bureau to create a picture of ground occurrences. This picture begins when an aircraft is being prepared for takeoff and ends when passengers and crew have disembarked from the aircraft. It explores contributing factors associated with each type of occurrence, with the objective of providing some insight into what happened and why various events occurred. The key to preventing ground occurrences appears to revolve around ensuring effective communication between pilots, ground crews and air traffic services through a process of checks and balances.

This report tables rail safety occurrence data by state and territory between 1 January 2001 and 31 December 2009. Data is adjusted biannually to reflect new information that comes to light during the reporting period. There is a lag period of approximately 3 to 4 months between the end of the 6-monthly reporting period and publication of this data. The data is presented as counts, and normalised using kilometres travelled and number of track kilometres. Data presented in this report conforms to ON-S1: Occurrence Notification Standard 1 (2004) and OC-G1: Occurrence Classification Guideline 1 (2008). This report excludes tram and light rail or monorail operations.

Each year, 'responsible persons', as defined in the Transport Safety Investigation Regulations 2003, Part 2.5, provide the Australian Transport Safety Bureau (ATSB) with reports on aviation accidents and incidents, collectively termed occurrences. These reports are used by the ATSB to assist with the independent investigation of occurrences and for identifying safety trends.

This report provides aviation occurrence data for the period 1 January 1999 to 31 December 2009. The data contained herein is dynamic and subject to change pending the provision of new information to the ATSB. The data will be adjusted biannually to reflect new information received during the reporting
period.

For commercial air transport (high-capacity regular public transport (RPT), low-capacity RPT and charter), although the accident rate had climbed in 2007 and 2008, the number of accidents reduced from 29 (2008) to 11 in 2009. This accident trend was mostly driven by changes in the accident rate for charter operations. Similarly, the number of serious incidents for commercial air transport reduced from 45 (2007 and 2008) to 26 in 2009. There were no fatal air transport accidents in 2009. One significant accident in 2009 involved the tail scrape and runway excursion at take-off of a foreign-registered Airbus A340-500 in Melbourne on 20 March. Charter has an accident rate that is about five times that of low-capacity and high-capacity RPT. Most fatal accidents in commercial air transport are in charter operations, and it has a similar rate of fatal accidents to all general aviation.

For general aviation (aerial work, flying training, and private/business and (VH-registered) sport aviation), accidents and serious incidents have remained generally consistent since 2007. In 2009, there were 126 accidents, including 18 fatal accidents, and 95 serious incidents. Compared with flying training, aerial work has an accident rate per million hours that is two times higher, and private/business has an accident rate that is 2.5 times higher. In terms of fatal accidents per million hours, the fatality rate in aerial work is three times higher than flying training, and private/business is at least six times higher.

Summary

The ATSB receives around 15,000 notifications of aviation occurrences each year; 8,000 of which are accidents, serious incidents and incidents. It is from the information provided in these notifications that the ATSB makes a decision on whether or not to investigate. While further information is sought in some cases to assist in making those decisions, resource constraints dictate that a significant amount of professional judgement needs to be exercised.

There are times when more detailed information about the circumstances of the occurrence would have allowed the ATSB to make a more informed decision both about whether to investigate at all and, if so, what necessary resources were required (investigation level). In addition, further publicly available information on accidents and serious incidents would increase safety awareness in the industry and enable improved research activities and analysis of safety trends, leading to more targeted safety education.

To enable this, the Chief Commissioner has established a small team to manage and process these factual investigations, the Level 5 Investigation Team. The primary objective of the team is to undertake limited-scope fact-gathering investigations, which result in a short summary report. The summary report is a compilation of the information the ATSB has gathered, sourced from individuals or organisations involved in the occurrences, on the circumstances surrounding the occurrence and what safety action may have been taken or identified as a result of the occurrence.

The summary reports detailed herein were compiled from information provided to the ATSB by individuals or organisations involved in an accident or serious incident between the period 1 December 2009 and 30 March 2010.

On the early evening of 31 January 2001 at Melbourne International Airport, Boeing 777-300 A6-EMM aborted its take-off run at low speed as a result of a failure within the left (No.1) engine. Although the failure was associated with a large compressor surge within the engine, no subsequent fire developed and the aircraft was able to safely return to the terminal building on its remaining serviceable engine.

Failure of the RB211 Trent 892 engine as fitted to the aircraft was a result of the release of a single blade from the low-pressure compressor (fan) rotor disk. The blade release caused extensive damage to the remainder of the fan and the intake shroud, however the event was fully contained. The only escape of debris from the engine was small, low energy fragments, causing minor damage to the fuselage and the opposite engine.

Field and laboratory examination of the released blade found that progressive fatigue cracking had resulted in the loss of two major sections from the blade dovetail root. The remaining material was subsequently unable to carry the centrifugal loads associated with the accelerating engine and failed in ductile shear, allowing the release of the blade from the rotor slot. No defects or other anomalous material or manufacturing features were found to have contributed to the crack development.

The blades installed within the Trent 892-17 engine were an approved variant of the original design, incorporating an undercut radius between the dovetail faces and the blade body. The modification was developed in order to avoid 'edge of bedding' stresses that had been implicated in blade cracking on development engines. Cracking of the released blade had initiated within this undercut radius on both sides of the shear key slot; locations that had been identified by finite element techniques as areas of high localised stress. Extensive galling of the seating surfaces was also found on all blades, indicating the long-term inadequacy of the dry film lubricant applied to the blade dovetail faces. The galling and micro-welding damage can readily interfere with the distribution of loads across the seating surfaces, leading to elevated stresses within the blade root.

Blade failure was thus attributed to an interaction of the following -

• Design - provided for areas of localised high tensile stresses arising from operating loads.
• Operating Stresses - act on the blade to produce cracking in areas highlighted by the design. In the absence of defects predisposing the blade to failure, the development of cracking implies elevated operating stress levels.
• Blade - Disk Connection Problems - galling of the dovetail surfaces indicates the potential for uneven load distribution through the connection, leading to increased stresses within the blade root and thus a greater disposition to fatigue cracking.