Research and Analysis Report

Why have we done this report?

All incidents and accidents affecting aviation safety are required to be reported to the Australian Transport Safety Bureau (ATSB) under the Transport Safety Investigation Act 2003. However, anecdotal evidence suggested that there has been an under reporting of aviation wirestrikes in Australia by pilots and others in the industry.

To determine if this was the case, electricity distribution and transmission companies and a telecommunications company, who are not responsible for reporting aviation occurrences to the ATSB, were asked to provide the ATSB with data on any aviation wirestrike they were aware of on their network. This report also documents existing initiatives these companies have taken to reduce wirestrikes on their networks.

What the ATSB found

This research investigation found that, based on data from electricity distribution and transmission companies, at least 40 per cent of wirestrike occurrences in Australia between July 2003 and June 2011 had not been reported to the ATSB.

It was also found that many electricity distribution and transmission companies produce safety education material for pilots and land owners warning them of the dangers of wires from the air and from the ground. Others also actively liaise with aerial agricultural and balloon operators to promote strategies in managing wires while flying.

Safety message

It is important that all aviation wirestrikes are reported to the ATSB so that they can be investigated (if required) and so that occurrence details can be collected for research purposes to identify emerging safety trends. Information reported to the ATSB increases our understanding of wirestrikes, the trends, as well as how and why they happen. It is only with reported information that the ATSB can improve aviation safety by establishing the true extent of wirestrikes and determining how and where they occur so that actions can be directed towards the most appropriate areas to reduce wirestrikes.

Pilots and operators involved in a wirestrike occurrence should report to the ATSB. Notifications can be made via the toll-free number 1800 011 034 (available 24/7) or via the ATSB notification website.

What's been done?

The ATSB will engage in a range of safety actions aimed at increasing the reporting of wirestrikes. These safety actions include promoting safety messages to the aviation industry, wire infrastructure owners and state regulators with an oversight of powerlines, with respect to the importance of reporting wirestrikes. The ATSB is also proposing changes to the Transport Safety Investigation Regulations 2003 to the Government, which are expected will be agreed and released in September 2012, to make it clearer that all aviation wirestrikes are required to be reported to the ATSB based on the premise that any contact with a wire during flight always has an adverse effect or a potential adverse effect on safety.

Why we have done this report

A significant proportion of all occurrences reported to the Australian Transport Safety Bureau (ATSB) involve aircraft striking wildlife, especially birds. 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 controlling the risks associated with bird and animal strikes. This report updates the first edition published in 2010 with data from 2010-2011.

What the ATSB found

In 2011, there were 1,751 birdstrikes reported to the ATSB. Most birdstrikes involved high-capacity air transport aircraft. For high-capacity aircraft operations, reported birdstrikes have increased from 400 to 980 over the last 10 years of study, and the rate per aircraft movement also increased. Domestic high-capacity aircraft (such as Boeing 737 and Airbus A320) were those most often involved in birdstrikes, and the strike rate per aircraft movement for these aircraft was significantly higher than all other categories. Larger high-capacity aircraft (such as Boeing 747 and Airbus A340 and A380) had a significantly lower strike rate. One in eight birdstrikes for turbofan aircraft involved an engine ingestion.

Take-off and landing was the most common part of a flight for birdstrikes to occur in aeroplanes, while helicopters sustained strikes mostly while parked on the ground, or during cruise and approach to land. Birdstrikes were most common between 7:30 am and 10:30 am each morning, with a smaller peak in birdstrikes between 6pm and 8pm at night, especially for bats.

All major airports except Hobart and Darwin had high birdstrike rates per aircraft movement in the past 2 years compared with the average for the decade. Avalon Airport had a relatively small number of birdstrikes, but along with Alice Springs, had the largest strike rates per aircraft movement for all towered aerodromes in the past 2 years.

In 2010 and 2011, the most common types of birds struck by aircraft were bats/flying foxes, galahs, kites and lapwings/plovers. Galahs were more commonly involved in strikes of multiple birds. Not surprisingly, larger birds were more likely to result in aircraft damage.

Animal strikes were relatively rare. The most common animals involved were hares and rabbits, kangaroos and wallabies, and dogs and foxes. 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. While it is uncommon that a birdstrike causes any harm to aircraft crew and passengers, many result in damage to aircraft, and some have resulted in serious consequential events, such as forced landings and high speed rejected take-offs.

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.

In the 2010-2011 financial year, the Australian Transport Safety Bureau (ATSB) completed 51 aviation, 11 marine, and 8 rail investigations where safety factors (events or conditions affecting safety risk) were identified using the ATSB analysis framework. From these investigations, 121 safety issues (factors that have a potential to adversely affect the safety of future operations) were identified and 137 safety actions were undertaken by various parties to address these safety issues. This report documents and analyses these safety issues and safety actions and explores the risk levels (critical, significant or minor) assigned to them to provide an understanding of where the greatest risks to each transport mode appear to lie. 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.

Inadequate procedures were a common safety issue found by ATSB investigations for all transport modes. Specifically for rail, the design and operation of procedures were common issues. Risk controls to manage technical failures were also common in aviation. Marine investigations found that equipment problems and safety management systems were also of significant concern.

Once safety issues are identified in an investigation, they need to be addressed. Across the three transport modes, 71 per cent of safety issues of significant risk were addressed (that is, had their risk reduced to an acceptable level), while 15 per cent were only partially addressed. Only one safety issue (from marine) continues to be not addressed without any expected future safety action.

Proactive industry safety action during an investigation was the most common way that safety issues were addressed across the aviation and marine modes, while for rail the most common method of addressing safety issues was for the ATSB to issue formal Safety Advisory Notices. Only one safety issue, in aviation, was assessed to pose a critical risk to safety and was addressed by technical inspections, repairs or modifications and changes to mandatory requirements.

The most common avenue to address safety issues that posed a significant risk to aviation safety was to communicate with and/or educate those involved. For marine, changing or reviewing policy or conducting organisational surveillance were the most common ways to address significant safety issues. In rail, the most common ways to address significant safety issues involved technical actions and policy changes.

In 1995 the Bureau published a survey of agricultural aviation accidents 1985-1992, which has now been updated by including accident and incident data for the period 1993-1995.

The data shows that agricultural aviation accidents accounted for 12% of all Australian aviation accidents during the 10-year period 1986-1995 and that the accident rate continues to be higher than that for other sectors of general aviation.

The majority of accidents occur in the agricultural work phase, whereas with other types of commercial operations most accidents occur in the take-off and landing phases. The largest group of accidents are associated with contacting powerlines or overhead communication lines (commonly called wirestrikes) and are attributed to the pilot either not seeing the powerline or momentarily forgetting the position of the powerline. These factors are categorised as failures in the pilots' 'perception of their working environment'. The second largest category of accidents was where the investigator assessed that the pilot exercised poor decision making ('incorrect operational decisions').

The number of agricultural aviation incidents reported to the Bureau was relatively small. However, those that were reported involved factors very similar to those associated with the agricultural accidents. There is a need for greater reporting of incidents as a means of increasing safety awareness and improving accident prevention.

This review of agricultural aviation accidents reported to BASI in the period 1985 to 1992 indicates:

• there were no significant reductions in the number or rate of accidents
• there were higher accident and fatal accident rates than for other GA operations
• the majority of accidents occurred in the agricultural work phase of flight, although the taxi and take-off phase accounted for a significant percentage of accidents
• factors related to pilot perception and operational decision were most frequent
• accident prevention programs should address:
  • failure to see and avoid objects or obstacles;
  • inadequacy of pre-flight preparation and planning; and
  • distraction from operation of aircraft.

The Director of BASI reiterated the points highlighted in this review when addressing the 1994 annual conference of the Aerial Agricultural Association.

Since 1984, the Australian Transport Safety Bureau and the former Bureau of Air Safety Investigation have produced numerous aviation research and education reports. This brochure lists those reports in chronological order and arranged by the broad topic area. All reports are available electronically on the ATSB internet site.

Everyday errors such as incorrectly transcribing or inadvertently dialling a wrong telephone number normally have minimal consequences. For high-capacity aircraft operation, the consequence of such errors can be significant. There have been numerous take-off accidents worldwide that were the result of a simple data calculation or entry error by the flight crew. This report documents 20 international and 11 Australian accidents and incidents (occurrences) identified between 1 January 1989 and 30 June 2009 where the calculation and entry of erroneous take-off performance parameters, such as aircraft weights and 'V speeds' were involved. Importantly, it provides an analysis of the safety factors that contributed to the international occurrences and suggests ways to prevent and detect such errors.

A review of the international and Australian occurrences showed that these types of errors have many different origins; with crew actions involving the wrong figure being used, data entered incorrectly, data not being updated, and data being excluded. Furthermore, a range of systems and devices have been involved in these errors, including performance documentation, laptop computers, the flight management computer, and the aircraft communications addressing and reporting systems. The consequences of these errors also ranged from a noticeable reduction in the aircraft's performance during the take-off, to the aircraft being destroyed and loss of life.

The most common contributing safety factor identified related to crew actions (39 per cent), including monitoring and checking, assessing and planning, and the use of aircraft equipment. This was followed by absent or inadequate risk controls (31 per cent), mostly centred on poor procedures, non-optimally designed aircraft automation systems, inappropriately designed or unavailable reference materials, and inadequate crew management practices and training. Common local conditions (27 per cent) involved inadequate task experience or recency, time pressures, distractions and incorrect task information.

Different airlines use, and different aircraft types require, different methods for calculating and entering take-off performance parameters, which means there is no single solution to ensure that such errors are prevented or captured. This report also discusses several error capture systems that airlines and aircraft manufacturers can explore in an attempt to minimise the opportunities of take-off performance parameter errors from occurring or maximise the chance that any errors that do occur are detected and/or do not lead to negative consequences.

This report documents the number and types of safety occurrences involving loading of high-capacity aircraft across a 7-year period to raise awareness within the aviation industry of the associated issues. Incorrect loading of containers, pallets or bags into aircraft can result in them being outside of weight or centre of gravity operating limits, and this may influence aircraft controllability. Most high-capacity aircraft loading occurrences are relatively minor, with cargo locks not being raised being the most common. More serious occurrences have involved shifting cargo and unlisted cargo being loaded onto aircraft. Aircraft performance has been affected in a small number of cases, and the result has been rejected take-off, extra stabiliser trim, or aircraft control difficulties.

The Human Factors Analysis and Classification System (HFACS) is a hierarchical taxonomy that describes the human factors that contribute to an aviation accident or incident that is based on a chain of- events theory of accident causation and was derived from Reason's (1990) accident model.

The objectives of this exploratory study were to identify relationships between the factors of the HFACS taxonomy and to assess the usefulness of HFACS as a predictive tool. The associations found in this study may assist investigators in looking for associated factors when contributing factors are found. Also, when using the HFACS taxonomy to identify areas for intervention, the relationships found may also guide intervention in associated areas for a holistic, systems approach to improvement.

This exploratory study found a number of strong positive relationships between factors at different levels of the model. However, based on the amount of variation explained by the logistical regression statistical models, it appears that HFACS is a more effective predictive framework when used to predict unsafe acts than when used to predict higher levels within the taxonomy.

The Australian Transport Safety Bureau (ATSB) formalised the concept of outside influences and added five factors within this grouping to the HFACS model in this study. The outside influences factors proved to be important additions to the HFACS model as they were associated with factors at all levels of the HFACS taxonomy.

The results have also shown that it is not always the case that higher-level factors predict only the lower-level factors directly below them. For example, inadequate supervision predicted precondition for unsafe acts, such as adverse mental states and crew resource management issues, as well as skill-based errors (two levels down).

Most aerodromes in Australia are located in uncontrolled airspace and do not have an air traffic control presence. At these non-towered aerodromes, and in the vicinity of them, pilots are responsible for making themselves aware of nearby aircraft and maintaining separation. This report aims to give pilots an appreciation of the types of safety events that have been associated with operations at non-towered aerodromes and provide education on expected behaviours to assist pilots in being prepared for the risks.

Generally, operations at non-towered aerodromes can be considered to be safe, but this relies on all pilots maintaining awareness of their surroundings and of other aircraft, and on flying in compliance with procedures, while being observant, courteous and cooperative. Most of the 709 airspace-related safety occurrences reported to the ATSB between 2003 and 2008 at, or in the vicinity of non-towered aerodromes, were incidents, but they also included 60 serious incidents and six accidents (mid-air and ground collisions). Most of the occurrences involved conflicts between aircraft, or between aircraft and ground vehicles. The most common types of occurrences involved ineffective communication between pilots operating in close proximity, separation issues, incorrect assessment of other aircraft's positions and intentions, relying on the radio as a substitute for an effective visual lookout, or a failure to follow published procedures.

This report also documents changes in the number of aircraft movements and changes in the traffic mix into 20 non-towered aerodromes since 2003. Aerodromes experiencing significant growth could potentially be exposed to higher risk. Port Macquarie, Kununurra, Ballina, and Mt. Gambier all have experienced a recent increase in large passenger transport aircraft movements.

This report looked only at incidents and accidents prior to the introduction of changes by the Civil Aviation Safety Authority (CASA) to Civil Aviation Regulation (CAR) 166 on 3 June 2010, which affected procedures at all non-towered (non-controlled) aerodromes. Although the CAR 166 changes may in time be shown to reduce incidents and accidents, a number of issues highlighted by the occurrences documented in this report are likely to persist at non-towered aerodromes, but associated risks can be minimised through greater awareness of the importance of clear and concise communications, effective visual lookout and adherence to published procedures.