Research and Analysis Report

Why the ATSB did this research

Through routine trend monitoring of safety occurrence reporting, the ATSB became aware of a potential issue surrounding the frequency of light aircraft engine failures and malfunctions (both Australian VH and recreationally-registered). To formally and more fully examine the contributing factors behind these statistical observations, the ATSB initiated this Aviation Research investigation (under the provisions of the Transport Safety Investigation Act 2003).

What the ATSB found

Over the 6-year study period between 2009 and 2014, 322 engine failures or malfunctions involving light aircraft were reported to the Australian Transport Safety Bureau (ATSB) and/or Recreational Aviation Australia (RA-Aus). These reports involved single-engine piston aeroplanes up to 800 kg maximum take-off weight. Aircraft powered by Jabiru engines were involved in the most engine failures or malfunctions with 130 reported over the 6 years. This represents about one in ten aircraft powered by Jabiru engines in the study set having reported an engine failure or malfunction. Reports from Rotax powered aircraft were the next most common with 87 (one in 36), followed by aircraft with Lycoming (58 – one in 35) and Continental (28 – one in 35) engines. When factoring in the hours flown for each of these engine manufacturers, aircraft with Jabiru engines had more than double the rate of engine failure or malfunction than any other of the manufacturers in the study set with 3.21 failures per 10,000 hours flown.

Unlike the engines of other engine manufacturers in this study, nearly half of the Jabiru engine failures or malfunctions related to a fractured component. Engine through-bolt failures were the most commonly reported failure mechanism in Jabiru powered aircraft with 21 through-bolt fractures reported between 2009 and 2014. Taking into account the number of aircraft registered in the study period, through-bolt failures occurred in about one in 55 Jabiru powered aircraft. Although originally designed to be replaced after 1,000 hours, 19 through-bolts failed before the 1,000 hour mark, with seven failing before 500 hours. At least four failures involved engines with upgraded 3/8 inch diameter through-bolt nuts. There were no failures reported involving the newer 7/16 inch diameter through-bolts which are used in currently manufactured engines (present in about 20 per cent of Jabiru engines).

What's been done as a result

Jabiru Aircraft Pty Ltd have designed and tested a modified 3/8 inch diameter through-bolt which incorporates aspects to alleviate the effects of thermal expansion and damp resonant vibrations.

The ATSB has issued recommendations to Jabiru Aircraft Pty Ltd and the Civil Aviation Safety Authority to reduce the risk of engine failure or malfunction in aircraft fitted with Jabiru engines and to assure future reliability of these engines.

Safety message

Owners and operators of light aircraft with Jabiru engines that have 3/8 inch diameter through-bolt configurations need to be aware of the continued elevated risk of a through-bolt failure leading to an engine failure or malfunction in flight. It appears that Jabiru engine service bulletins, requiring upgraded through-bolts of the same thickness and upgraded nuts to the 12-side ARP nuts, may not have fully addressed this issue. Thicker 7/16 inch through-bolts (installed in newly manufactured engines and recommended as a retro-fit for aircraft conducting flight training), appear to have improved the reliability of Jabiru engines, although future monitoring will provide more definite evidence.

This is the first publication in a series from the ATSB on aerial application (agricultural spraying and firefighting) accidents during the previous operational year (May 2014 to April 2015). Aerial application operations have a notably high accident rate relative to other aviation sectors. These operations involve inherent risks that are not present in most other types of flying. Risks include low-level flying with high workloads and numerous obstacles, in particular powerlines and uneven terrain. This report will focus on the aerial application accidents that occurred between May 2014 and April 2015 and fatal accident reports published in this period to coincide with the agriculture season in most parts of Australia.

Media release: Report to educate aerial agriculture and firefighting pilots

Why we have done this report

Occurrences involving aircraft striking wildlife, particularly birds, are the most common aviation occurrence reported to the Australian Transport Safety Bureau (ATSB). Strikes with birds continue to be a significant economic risk for aerodrome and airline operators and a potential safety risk for pilots. The aim of the ATSB’s statistical report series is to give information back to pilots, aerodrome and airline operators, regulators, and other aviation industry participants to assist them with managing the risks associated with bird and animal strikes. This report updates the last edition published in 2012 with data from 2012-2013.

What the ATSB found

Between 2004 and 2013, there were 14,571 birdstrikes reported to the ATSB, most of which involved high-capacity air transport aircraft. Although the number of birdstrikes has continued to increase for all operation types, due to increasing aircraft movements, the rate per aircraft movement has actually decreased slightly in recent years. In the 2 years since 2011, the rates for seven of the ten major airports have reduced. Indeed, Adelaide, Melbourne, Perth and Sydney had lower rates in 2013 than in 2004. The largest increase in birdstrike rate was observed in Darwin, where the rate has more than doubled in the two years since 2011 and maintains the highest average birdstrike rate of all the major airports. Alice Springs Airport has shown the most significant reduction in rate.

Domestic high-capacity aircraft were those most often involved in birdstrikes, and the strike rate per aircraft movement for these aircraft was significantly higher than all other categories. The number of engine ingestions for high-capacity air transport operations had been increasing until 2011, but has since decreased to the lowest level in 10 years. Still, one in nine birdstrikes for turbofan aircraft involved an engine ingestion.

The four most commonly struck types of birds have not changed in the 2012 to 2013 period, those being kites, bats/flying foxes, lapwings/plovers and galahs. Kites had the most significant increase in the number of reported strikes per year in the last 2 years, with these species being involved in an average of 129 strikes per year for 2012 and 2013 compared with 84 per year on average across the entire 10-year reporting period. Galahs were more commonly involved in strikes of multiple birds, with more than 38 per cent of galah strikes involving more than one galah. However, larger birds were more likely to result in aircraft damage.

Historically, birdstrikes have not been a significant safety risk to civilian air travel in Australia. ATSB data dating back to 1969 show no civilian aviation fatalities attributed to birdstrikes. Additionally, the vast majority (98.7%) of birdstrikes over the 10 year study period were assessed using the ATSB event risk classification (ERC) framework as being low risk occurrences.

Compared to birdstrikes, animal strikes are relatively rare. The most common animals involved were hares and rabbits, kangaroos, dogs / foxes and wallabies. Damaging strikes mostly involved kangaroos, wallabies and livestock.

Safety message

Australian aviation wildlife strike statistics provide a reminder to everyone involved in the operation of aircraft and aerodromes to be aware of the hazards posed to aircraft by birds and non-flying animals. Timely and thorough reporting of birdstrikes is paramount. The growth of reporting to the ATSB that has been seen over the last 10 years has helped to better understand the nature of birdstrikes, and what and where the major safety risks lie. This helps everyone in the aviation industry to better manage their safety risk.

The ATSB has been advised that the hours flown data provided by the Bureau of Infrastructure, Transport and Regional Economics (BITRE) and used for the calculation of occurrence rates by aircraft type, may have been under-reported for some aircraft types used in charter operations. The ATSB is awaiting new hours flown data from BITRE and will update the reports accordingly when this data is available.

Why the ATSB did this research

This is the first in a series of research investigations looking at technical failures reported to the ATSB between 2008 and 2012. This report reviews power plant problems reported to the ATSB affecting turbofan-powered aircraft, and the types of incidents they are associated with.

By summarising power plant-related occurrences across all operators, this report provides an opportunity for operators to compare their own experiences with others flying the same or similar aircraft types, or aircraft using the same engines. By doing so, the ATSB hopes that the wider aviation industry will be able to learn from the experience of others.

What the ATSB found

Despite the complexity of modern turbofan engines, their reliability is evidenced by the remarkably low rate of power plant occurrences. With a combined total of over five and a half million flight hours for turbofan engine aircraft between 2008 and 2012, there were only 280 occurrences relating specifically to the power plant systems (or approximately one occurrence every 20,000 flight hours). Additionally, the vast majority of these (98%) were classified as being a low risk rating occurrence with a low or no accident outcome. Only four were classified as medium risk, two as high risk and one as very high risk. None resulted in injury to passengers or crew.

Although the rates were low for the turbofan engine aircraft group as a whole, there were large differences between individual aircraft models. Three aircraft types in particular, the Boeing 747 classic, the Fokker F28/F100 and the British Aerospace BAE 146/Avro RJ, had far greater rates of power plant occurrences between 2008 and 2012 than any other aircraft in this study. Although these three aircraft types represented some of the older fleets, there were other fleets of aircraft of similar ages with far lower rates of occurrences.

Safety message

The small number of high and very high risk power plant occurrences between 2008 and 2012 remind us that even highly sophisticated modern power plants can, and do, fail. Timely and vigilant reporting of all technical problems is therefore strongly encouraged to ensure as much information as possible is collected to better understand these problems. Of particular importance in technical occurrences are the follow-up reports from engineering inspections. These are often the only way that the root cause of the problem can be determined. The more comprehensively these are reported to the ATSB, the more insightful and useful reports like this become.

This report was updated on 23 October 2014 with revised hours flown data used for the calculation of occurrence rates by aircraft type.

 Why did we do this research

This study has been undertaken in order to further understanding of the nature and impact of fumes and smoke related occurrences in relation to the safety of aircraft operations in Australia and, in doing so, evaluate associated data availability and suitability. This report also addresses recommendations from a 2011 report commissioned by the Civil Aviation Safety Authority (CASA) by an Expert Panel on Aircraft Air Quality that aviation safety agencies work together to provide a comprehensive study of cabin air contamination incidents.

The study was undertaken in two parts; the first involved an in-depth analysis of aviation safety data sets held by the Australian Transport Safety Bureau (ATSB), CASA and the Department of Defence for the 2008-2012 period. The second part of the study involved a basic risk analysis of smoke/fumes safety events using the bowtie risk model.

What the research found

There were over 1,000 fumes/smoke events reported to both the ATSB and CASA over the 5-year period. From a flight safety perspective, most were found to be minor in consequence. There was a single flight crew incapacitation event and a further 11 minor injury events to crew. In the higher risk occurrences, precautionary defences (most commonly diversions) were found to be effective in avoiding escalation of the event.

The British Aerospace BAe 146 was the aircraft type most commonly involved in fumes/smoke events when taking into account flying activity. The Airbus A380, Boeing 767, Embraer EMB-120 and E-190 were among other aircraft types that also had a higher-than-average rate of fumes/smoke occurrences over the period.

The most common source of fumes/smoke was aircraft systems issues, primarily relating to failure or malfunction of electrical and auxiliary power unit (APU) systems. Equipment and furnishings also featured highly as a source of fumes and smoke. Within this category, air conditioning and galley equipment were the most common sources of fumes/smoke. External sources of fumes/smoke and cargo/baggage related events were relatively rare.

The matching of CASA and ATSB data records provided valuable information on the issue of fumes/smoke which enabled visibility of occurrences from both an engineering and operational perspective. However, many reports of fumes/smoke events contained insufficient detail for coding of the source or affected components.

Safety message

Fume and smoke events are generally appropriately managed by flight and cabin crew resulting in little consequence. Good reporting by aircraft operators, with sufficient detail, to both the ATSB and CASA where relevant will assist ongoing efforts to monitor the risk of fume and smoke events.

Why the ATSB is doing this research

One of the main objectives of air traffic services (ATS) is to prevent the collision of aircraft. Aircraft separation standards are set to ensure that the chance of a mid-air collision is very remote. When they are infringed, there are fewer defences left to guard against a mid-air collision. This ATSB research investigation looks at loss of separation (LOS) incidents in Australian airspace to understand how often they occur and in what contexts, how and why they are occurring, and whether there are any wider implications that the air traffic system is not functioning appropriately.

What the ATSB found

Although there had been an increase in the number of occurrences reported to the ATSB over the 2 years ending in June 2012, there were fewer LOS occurrences during that period than during 2005 to 2008. Traffic levels have generally increased during the same period. A LOS between aircraft under air traffic control jurisdiction happens on average about once every 3 days. In almost 90 per cent of LOS occurrences, there was no or minimal risk of aircraft colliding. On average, however, there are six occurrences per year where an elevated risk of collision exists. There have been no mid-air collisions in Australia between two aircraft under ATS control.

The investigation found that military controlled terminal area airspace in general, and all airspace around Darwin and Williamtown in particular, had a disproportionate rate of LOS (for civilian aircraft). Most of these LOS occurrences were contributed to by air traffic controller actions. This may be a result of the nature of aircraft operations and airspace constraints at some military airports, leading to reduced use and effectiveness of strategic separation defences, thereby placing more responsibility for separating aircraft directly onto the controllers. Furthermore, as military ATS are not subject to safety oversight by the Civil Aviation Safety Authority (CASA), there is no independent assessment and assurance as to the safety of civilian aircraft operations at military airports.

In civil airspace, LOS occurrences attributable to pilot actions are not monitored as a measure of airspace safety nor actively investigated for insight into possible improvements to air traffic service provision. As about half of all LOS incidents are from pilot actions, not all available information is being fully used to assure the safety of civilian airspace.

What's been done as a result

The ATSB has issued recommendations to the Department of Defence to review all processes and controls in place for aircraft separation in military ATS and to CASA to review whether its current level of involvement with military ATS is sufficient to assure the safety of civil aircraft operations. The ATSB also recommends using all available information, including pilot attributable LOS occurrences, to assure the safety of civilian airspace, and will itself investigate all serious LOS incidents.

Safety message

Aircraft separation is a complex operation with many levels of defences to avoid errors and to safely manage the results of the errors that will inevitably be made from time to time by air traffic controllers and pilots. The defences ensure that even if a LOS does occur, the chance of an aircraft collision is still very remote. Safety could be enhanced through understanding and addressing the reasons for the disproportionate rate of LOS occurrences involving civil aircraft in military airspace, and through the ongoing monitoring and investigation of all LOS incidents in civil airspace.

Why have we done this report

Significant debate has occurred within the aviation industry regarding the issues of pilot training and experience, particularly with regard to the introduction of new pilot training programs that are focused on training cadet pilots. The main concern being presented by some sectors of the industry that are not in favour of these concepts is that these low-hour co-pilots are not as competent as their high-hour peers.

The ATSB gathered data from three airlines to explore the issue of pilot performance as a function of both flight hour experience, and entry pathway. Entry pathway analysis compared cadet pilots (who generally had not accumulated prior flight hours or experience) to those pilots who entered an airline after accumulating flight hours in other areas of the aviation industry.

Data were collected on a number of metrics from simulator check flights, which covered non-normal operations, and line checks, which covered normal day-to-day flight operations.

What the ATSB found

The overall performance of cadets and low-hour pilots matched that of their direct entry and high-hour peers. All pilots were marked as proficient at the completion of the check flights, with the only differences between the groups being a function of how many exceeded the required standard.

The differences between the low and high-hour pilots in ‘meeting’ and ‘exceeding’ the standard across all metrics were variable within airlines and inconsistent across all three airlines. This suggests that the differences between the groups were not of a systemic nature that would highlight an area of concern for industry. While the metric normal landing showed a difference across two of the three airlines, none of the other required regulatory manoeuvres or technical metrics were significantly different in more than one airline. For non-technical metrics, both leadership and situation awareness were significantly different in all three airlines. Although this is understandable given the low experience of cadet and low-hour pilots, focused exposure to those metrics during initial airline training may reduce this difference as was seen in the data for cadets collected at the 5-year mark in one airline.

Safety message

The evidence in this report indicates that the cadet pathway for low-hour pilots is a valid option for airlines. There was no evidence to indicate that cadets or low-hour pilots within the airlines studied were any less competent or proficient than their direct entry and high-hour peers.

Why the ATSB did this research

Emergency locator transmitters are radio beacons carried on most aircraft so that in the event of an accident in a remote location the aircraft wreckage and its occupants can be located quickly by search and rescue (SAR) operations. Finding the aircraft wreckage quickly not only increases the chance of survival of the occupants, but also reduces the risk to pilots of SAR aircraft who commonly need to operate in marginal weather conditions and over mountainous terrain.

Airframe mounted emergency locator transmitters (ELTs) are designed to automatically activate following an impact typical of a collision. However, the effectiveness of airframe ELTs in aviation accidents has been questioned for some time by accident investigation agencies and by the aviation community. Beyond individual examples of ELTs not activating following an accident, there has been little research done to date to review how reliably ELTs operate as designed after an aircraft accident. In this research investigation, the ATSB identifies safety concerns regarding the operation of ELTs and presents data on the effectiveness of ELTs activating following an accident.

What the ATSB found

Data from the ATSB database show that ELTs function as intended in about 40 to 60 per cent of accidents in which their activation was expected.

Records of the Australian Maritime Safety Authority’s SAR incidents shows that search and rescue personnel were alerted to aviation emergencies in a variety of ways including radio calls and phone calls, and that ELT activation accounted for the first notification in only about 15 per cent of incidents. However, these ELT activations have been directly responsible for saving an average of four lives per year.

In accidents where ELTs did not work effectively (or at all) it was found that their performance could be affected by:

• not selecting the ELT activation to armed before flight
• incorrect installation
• flat batteries
• lack of water proofing
• lack of fire protection
• disconnection of the co-axial antenna cable from the unit during impact
• damage and/or removal of the antenna during impact
• an aircraft coming to rest inverted after impact.

Safety message

Pilots and operators of general aviation and low-capacity aircraft need to be aware that a fixed fuselage mounted ELT cannot be relied upon to function in the types of accidents in which they were intended to be useful. The effectiveness of ELTs in increasing occupant safety and assisting SAR efforts may be enhanced by using a GPS-enabled ELT, using an ELT with a newer 3-axis g-switch, ensuring it is installed correctly, ensuring your beacon is registered with AMSA and pre-emptively activating the beacon if a forced landing or ditching is imminent. Additionally, carrying a personal locator beacon (PLB) in place of or as well as a fixed ELT will most likely only be beneficial to safety if it is carried on the person, rather than being fixed or stowed elsewhere in the aircraft.

Why is the ATSB doing this research?

Each year, the ATSB conducts investigations into transport safety matters in aviation, rail and marine. Most of these reports document safety issues (factors that have a potential to adversely affect the safety of future operations) identified during the investigation, along with the assigned risk level for each safety issue. The ATSB also individually documents safety actions completed by industry or regulators in response to the identified safety issues. When no or inadequate safety action occurs, the ATSB may also release a safety recommendation, which is required to be responded to within 90 days.

This report documents the ATSB identified safety issues and related safety actions and recommendations for the 2011–12 financial year and trends across 3 financial years. It will explore the risk levels assigned and provide an understanding of where the greatest risks to each transport sector appears to lie, based on investigation findings. The results will be useful for government decision makers, regulators and the aviation, rail and marine industries to understand if and where attention to risk needs to be applied.

What the ATSB found

In the 2011–12 financial year, the ATSB completed 56 occurrence investigations into air transport, general aviation, rail and marine accidents and incidents. These investigations identified 100 safety issues, of which 28 posed a significant risk to safe ongoing operations and required safety action. More significant issues were identified in marine operations than in any other transport sector. Most safety issues were addressed with safety actions, especially those taken proactively by industry (more than 90 per cent of all safety actions).

The types of safety issues identified in investigations completed in 2011–12 were similar to those found in previous financial years, though there were more issues relating to marine operations, and less relating to general aviation. Safety issues were most often found with risk controls, particularly procedures. Safety management processes of organisations were an emerging issue in marine accidents and incidents in 2011–12, as were on-vehicle safety procedures and equipment in rail.

In all transport sectors, the most commonly identified safety factors that contributed to the accident or incident were the actions of individuals. In aviation, aircraft operation actions usually contributed to accidents and incidents – in marine, navigation and deck operation actions, and in rail operations, maintenance and vehicle operation actions most commonly contributed. Effects of local conditions (such as weather, training and skill level, workload, stress or fatigue) were common contributors to accidents and incidents.

Safety message

The ATSB plays a central role in identifying where areas of safety concern exist in Australia’s transport system. While investigations tend to show that individual actions contribute to most accidents and incidents, there are many latent safety issues that have the potential to cause further accidents if not addressed. Issues with training, fatigue, operating procedures, and the quality of safety management systems frequently contribute to accidents, and are wholly avoidable.

The ATSB continues to promote safety actions initiated by industry as the most timely and effective way to drive safety improvements to close identified gaps in safety. The misfortunes of others are a timely reminder to everyone involved in transport to look for similar safety risks in their operation that could lead to a similar accident or serious incident.

Why have we done this report?

Australian aviation, marine and rail industries have all recently incorporated safety management systems into regulations and operations as a required way of managing safety. Safety management systems (SMS) refer to organisations having a systematic approach to managing safety, including organisational structures, accountabilities, policies and procedures. They generally include several common elements such as explicit management commitment to safety, appointment of key safety personnel, hazard identification and risk mitigation, safety investigations and audit, and safety performance monitoring. Although Australia’s transport industries’ SMS approach is following world’s-best practice, little empirical research evidence has been presented to determine the impact on safety of a structured SMS. The objective of this research investigation was to examine the published research literature into the efficacy of safety management systems, safety programs and related management processes that is applicable to high-reliability transport operations. The examination also aimed to identify which characteristics of these systems, and/or other organisational characteristics or external influences, are most related to the quality of an organisation’s safety management. The outcome of this review may help organisations and regulators prioritise their efforts on those areas most likely to improve safety performance, and provide guidance for reviewing, auditing or investigating an organisation’s safety management processes.

What was found

A comprehensive search of the literature found 2,009 articles, with 37 directly relevant to the objectives of this investigation, and a significant amount of literature published in the past 5 years. However, only 14 involved an SMS designed to avoid low-probability/high-consequence (LP-HC) accidents, with the remaining 23 studies relating to work health and safety. In addition, very few of these studies were undertaken in transport domains, and many studies only measured subjective perceptions of safety rather than objective measures. The limited quality empirical evidence available relate to the difficulty of measuring objective safety improvements in industries where the SMS is aimed at avoiding LP-HC accidents and the relative recency of the application of SMS.

Nineteen studies analysed objective metrics such as safety performance, employee behaviours, and accidents. Several of these found that organisations with a certified SMS had significantly lower accident rates. However, across these studies, there was a lack of agreement about which components of a safety management system individually contributed the most to safety performance.

A further 18 studies used self-report metrics about perceptions of safety within the organisation to examine the effectiveness of an SMS. Although there was also a general lack of consistency across which elements of an SMS affected safety the most, it was commonly found that both management commitment and safety communication were important.

Safety message

Incorporating safety management systems into normal business operations does appear to reduce accidents and improve safety in high-risk industries. At present, there have only been a small number of quality empirical evaluations of SMSs, and it is unclear as to whether any individual elements of a SMS have a stronger influence on safety over other elements, although management commitment and appropriate safety communications do affect attitudes to safety. Transport organisations that provide an appropriate investment and commitment to a safety management system should receive a positive return on safety.