Birdstrike

Investigation summary

What happened

On the morning of 14 July 2025, a Bell 206L-3 helicopter, registered VH-JMM, was being operated on multiple passenger charter flights around the Arnhem region in the Northern Territory. On board was a pilot and one passenger. 

During the fourth leg of the day at approximately 1338, while looking down and to the left out of the helicopter, the pilot heard a loud bang. The pilot saw a large bird laying between the 2 occupants, and what appeared to be serious injuries to the passenger’s upper body. The pilot reached over to the passenger to check for a pulse but was unable to feel one. Noting the passenger required immediate attention, they decided it would be better for the passenger to receive medical attention at Lake Evella Aerodrome where a police station was next to the airport.

Police, a local nurse and doctor attended to the passenger, however the passenger had succumbed to injuries. The helicopter sustained minor damage. 

What the ATSB found

While cruising at about 900 ft AMSL, the helicopter struck a white bellied sea eagle which passed through the windshield and impacted the passenger.

The pilot had limited opportunity to detect the bird as they were looking down and to the left of the helicopter’s trajectory, reducing the pilot’s ability to see the bird and change the helicopter’s flight path in time, and likely rendering the collision unavoidable under the circumstances.

The passenger was not wearing a helmet at the time, nor was there an aviation regulatory requirement for them to do so. In this case, the location of the bird strike on the passenger was such that wearing a helmet probably would not have reduced the level of injury.

Safety message

Birdstrike is an almost unavoidable and relatively common hazard for all aviation operations. While these strikes typically result in minor or no damage to an aircraft and no injuries to occupants, this is the third fatal birdstrike accident in Australia in recent years.

Pilots are reminded that maintaining effective lookout will assist in maintaining better situational awareness in flight, and also assist in providing better outcomes to see‑and‑avoid not only birds, but other airspace users. 

Additionally, pilots should maintain situational awareness, especially when flying over waterways or wetlands. It is relatively common for large birds, such as eagles, hawks, and gulls, to attack helicopters and drones, often perceiving them as threats or territorial intruders. These birds may display aggressive behaviour during nesting or breeding seasons, diving at or striking the aircraft in an attempt to drive it away. Helicopter operators should consider whether available occupant protections, such as the wearing of flight helmets and the fitment of impact-resistant aircraft windshields, are appropriate for their operations.

 

The investigation

The ATSB scopes its investigations based on many factors, including the level of safety benefit likely to be obtained from an investigation and the associated resources required. For this occurrence, the ATSB conducted a limited-scope investigation in order to produce a short investigation report, and allow for greater industry awareness of findings that affect safety and potential learning opportunities.

The occurrence

On the morning of 14 July 2025, a Bell 206L-3 helicopter, registered VH‑JMM, was being operated by Nautilus Aviation on multiple air transport (passenger charter) flights around the Arnhem region in the Northern Territory. On board was a pilot and a passenger. 

At approximately 0928 local time the helicopter departed Gove Airport for Donydji. The pilot reported that from Donydjii, they flew to ‘Nyquist tower’[1] and then on to Mirrnatja before departing for Burrum, which would be the last stop of the day before returning to Gove (Figure 1).

Figure 1: Flight path overview

Source: Google Earth, annotated by the ATSB

The flight departed for Burrum at 1313 (Figure 2) and the pilot established a cruise altitude of about 900 ft above ground level. The pilot recalled having a conversation with the passenger about a waterway which they were flying near, and was familiar to the passenger. The pilot recalled slightly deviating off track to view the waterway. At approximately 1338, while looking down to the left out of the aircraft, the pilot recalled hearing a loud bang. 

The pilot saw a large bird laying between the 2 occupants, and what appeared to be serious injuries to the passenger’s upper body. The pilot reached over to the passenger to check for a pulse, but was unable to feel one. Noting the passenger required immediate attention, the pilot deliberated whether to land nearby and attempt resuscitation, and initially began to descend. However, considering the logistical issues with getting medical attention in a remote location, they decided it would be better for the passenger to receive medical attention at Lake Evella Aerodrome where a police station was next to the airport. 

Figure 2: Accident flight overview

Source: Google Earth, annotated by the ATSB

The pilot landed the helicopter at Lake Evella Aerodrome at approximately 1346. They stated they attempted to call emergency services on 000, however the call did not connect. They decided not to attempt the call a second time and ran to the police station for assistance instead. 

Police, a local nurse and doctor attended to the passenger, however the passenger had succumbed to injuries. The aircraft sustained minor damage (see Helicopter damage). 

Context

Pilot information

The pilot held a valid Class 1 Aviation Medical Certificate and a Commercial Pilot Licence (Helicopter). The pilot had accumulated 2,553 hours of aeronautical experience, of which 1,319 hours was on the Bell 206L.

The pilot had been with the operator since September 2024 and had regularly flown these routes to remote communities as part of their employment. 

Passenger information

The passenger was a frequent passenger on the routes operated on the day and had travelled by helicopter regularly to remote communities as part of their employment since 1995.

The pilot reported to having flown this passenger to remote communities on multiple occasions. Familiar with the aviation environment, the pilot reported the passenger would assist with monitoring for birds during flights, as they were aware they presented a hazard in flight. 

The post-mortem examination report indicated the passenger was hit between the lower jaw and the upper chest, sustaining fatal injuries to the neck, chin, lower jaw and the right side of the chest. 

Helicopter information

General

VH-JMM was a Bell Helicopter Company B206L‑3 Long Ranger, S/N 51400, manufactured in Canada in 1990. It was first registered in Australia in June 2017. The aircraft was registered to the operator in January 2024.

VH-JMM was a helicopter with two‑bladed main rotor and tail rotor systems, powered by a single Rolls-Royce 250‑C30P gas turbine engine.

At the time of the accident, the helicopter had completed 13,250 hours in service and had a current maintenance release.

Helicopter damage

The helicopter sustained damage to the passenger side windshield. There was no other reported damage to the aircraft (Figure 3).

Figure 3: Helicopter damage

Source: Northern Territory Police Force, annotated by the ATSB

Helicopter windshields

VH-JMM was fitted with standard acrylic windshields, which were not rated for impact resistance.

In 2016 Bell Helicopter Company introduced polycarbonate windshields, through a supplemental type certificate (STC) for the Bell 206 series, including the 206L. These were available as an additional option for current owners, offering higher impact resistance compared to traditional acrylic, reducing the risk of breaches from birdstrikes or other impacts. These were rated to United States regulatory requirements of a 2.2 lb (1 kg) bird traveling at V_NE (the helicopter’s never-exceed speed).[2]

Despite having a higher impact resistance than acrylic, polycarbonate windshields are more sensitive to scratches, and reportedly susceptible to clouding or hazing due to ultraviolet light exposure, resulting in loss of optical clarity and necessitating more frequent replacements.

Weather information

The terminal aerodrome forecast for the accident region forecasted clear conditions for the flight with scattered cloud above 3,500 ft and visibility greater than 10 km.

At 1530, the weather station at Elcho Island Airport, 48 km north of the accident location, recorded the wind as 4 kt from 110° magnetic. There was scattered cloud at 1,000 ft, visibility was greater than 10 km and the temperature was 23°C.

The pilot reported that the weather varied depending on where they were flying, however it was mostly clear with some areas of cloud. They reported the clouds were above their cruise height. 

Recorded data

The aircraft was fitted with a Spidertracks flight tracking unit and the pilot used OzRunways electronic flight bag software; both recorded flight data. Flight data indicated that the aircraft was cruising at 900 ft above ground level at a groundspeed of 94 kt at the approximate time the bird was struck. The data showed an initial deceleration to 86 kt groundspeed and a decrease in altitude of 50 ft, followed by a secondary decrease in altitude of approximately 150 ft (likely associated with the pilot’s consideration of whether to land). The track showed that the helicopter then climbed to 800 ft and increased groundspeed to about 70 kt (Figure 4).

Figure 4: Recorded flight track

Source: Google Earth, annotated by the ATSB

Bird information

Recovered biological specimens of the bird, including wing feathers and residue from the carcass, were found both inside the helicopter and on the passenger. Through images of the bird, the ATSB determined the species to be a white‑bellied sea eagle. 

The white-bellied sea eagle (Haliaeetus leucogaster) (Figure 5) is a large raptor commonly found in coastal regions of Australia, recognised for its distinctive white head, belly, and tail contrasted by dark greyish‑brown wings and back. Adults measure approximately 66‍–‍85 cm in length, with a wingspan of 1.8‍–‍2.2 m (Debus, 2017). Adult males typically weigh between 1.8‍–‍3 kg, while females average 2.5‍–‍4.5 kg (Marchant & Higgins, 1993). The weight and sex of the bird in this accident was unknown. 

Figure 5: Some of the bird remains retrieved from the helicopter

Source: Northern Territory Police Force

These eagles are often observed soaring over coastlines, estuaries, or inland waterways, preying on fish, seabirds, or carrion, and can reach heights of up to 1,000 m (about 3,300 ft) (Ferguson‑Lees & Christie, 2001). Their activity increases during the June to January period in Australia, which is their breeding season (Debus, 2017). 

It is relatively common for large birds, such as eagles, hawks, and gulls, to attack helicopters and drones, often perceiving them as threats or territorial intruders. These birds may display aggressive behaviour during nesting or breeding seasons, diving at or striking the aircraft in an attempt to drive it away (Washburn & others, 2015). 

Limitations of see-and-avoid

The human visual system is inherently limited in detecting small objects such as birds at distances. Hobbs (1991) notes that effective visual scanning requires systematic eye movements across the visual field, yet pilots often employ unsystematic techniques, resulting in unsearched areas. Furthermore, the cognitive process of identifying a threat, assessing its collision risk, deciding on evasive action, and executing control inputs requires time that is often unavailable in low‑altitude, high‑speed scenarios.

Birds present unique challenges to the see‑and‑avoid principle due to their relatively small size, unpredictable flight paths, and speed difference compared with aircraft. Unlike aircraft, birds cannot be tracked electronically, meaning pilots must rely solely on visual identification.

Survivability

Restraints

The helicopter was fitted with 4‑point harnesses in the front seats. The pilot reported both they and the passenger had been fastened into the seats by the aircraft’s 4‑point harnesses. 

Helmets

The pilot reported wearing a flight helmet[3] and reported wearing a helmet whenever possible, noting that helmets had saved lives in the past. The pilot recalled previously having a discussion with the passenger about helmets and the benefits of them. 

The passenger was not wearing a helmet at the time, nor was there an aviation regulatory requirement for them to do so. Nautilus Aviation stated that there was no requirement for passengers to wear a helmet and the decision on their use rested with the passengers themselves or their employers.

Telstra helicopter charters

The passenger was on board the aircraft as part of their work for Telstra, a telecommunications company. Telstra reported that its employees took about 630 helicopter charters on average per year, a mix of passenger charter (transit) and aerial work.

The employer had an operational framework for chartering aircraft that addressed many risks typically associated with helicopter flights, outlining expectations for the aircraft operator. These included the requirement for the aircraft operator to perform a risk assessment ‘prior to the first flight of any new operation by the Charter operator.’ 

Telstra did not have prescribed or recommended personal protective equipment for employees travelling or working on helicopters. Telstra advised that it relied on the licenced and accredited aviation providers that it engages to advise on safety of flight aspects including the use of personal protective equipment (PPE).

Related occurrences

Global data

Birdstrikes are a recognised hazard in aviation and there are mitigators in place at certified airports, however, there are challenges when operating outside of these areas. 

A review of Australian and internation data was conducted using the Avisure serious accident database. Between 1912 and 2024, birdstrikes have resulted in 763[4] reported aviation occurrences worldwide that involved serious or fatal injuries, of which 204 were fatal. Among these fatal cases, 18 involved rotary‑wing aircraft such as helicopters. These 18 accidents comprised 13 civil and 5 military rotary‑wing aircraft (Figure 6).

Figure 6: Global birdstrike data resulting in fatalities

Data does not include this occurrence (AO-2025-039). Source: Avisure

United States data

In the United States, a total of 13,667 bird strike occurrences were reported to the Federal Aviation Administration (FAA) in operations involving aircraft (fixed-wing and rotary-wing) under 5,700 kg maximum take‑off weight from 2014 to 2024. Of these, 60 occurrences resulted in non-fatal injuries, and 11 were fatal. 

A subset of 334 occurrences involved birds striking and damaging the aircraft windshield, with 48 of these occurrences (14.4%) resulting in serious injuries and 6 (1.8%) leading to fatal injuries. 

Of the total, 3,001 occurrences involved rotary-wing aircraft, which equated to a birdstrike every 285,390 flight hours (Table 1). These included 201 recorded windshield strikes, that resulted in 28 (13.9%) serious injuries and 2 (1.0%) fatalities. 

Table 1: Reported helicopter birdstrikes comparison 2014–2024

Reporting country	Number of occurrences involving helicopters	Flight hours per birdstrike	Flight hours per birdstrike to windshield resulting in damage
Australia	412	39,690	8,819
United States	3,001	285,390	19,026

In comparison to the most frequently struck aircraft component, the wings, with 1,171 occurrences, only 6 (0.5%) resulted in injuries including 1 with fatal injuries (0.09%), indicating that the proportion of serious and fatal outcomes from windshield strikes is unexpectedly high relative to other aircraft parts. 

Australian data

Birdstrikes in Australia

Between 2014–2024 the ATSB aviation wildlife dashboard indicated there were 17,060 reported birdstrikes reported to the ATSB across all aircraft types (including fixed‑ and rotary-wing). There were 412 reported birdstrikes during helicopter operations (Table 2), which equated to a birdstrike every 39,690 flight hours. The data did not include what component was struck unless the component was damaged, so it was not possible to determine the proportion of windshields struck that were penetrated or damaged. Of the 412 reported birdstrikes to helicopters, 17 had damage to the windshield.

Table 2: Reported helicopter birdstrikes within Australia 2014–2024

Total reported incidents	Injury level			Aircraft damage
	Nil	Minor	Fatal	Nil	Minor	Substantial	Destroyed	Unknown
412	411	0	1[1]	352	37	2	2	19
This figure does not include this occurrence

ATSB records indicate there were 2 fatal accidents in civil aircraft in Australia due to birdstrike. Additionally, there was 1 serious accident involving a bird entering through the windshield. These investigations are described in the following subsections.

Birdstrike involving Glasair Sportsman GS‑2, N666GM, near Bathurst, New South Wales, on 24 December 2015 (

)

During take-off the aircraft collided with a wedge‑tailed eagle (Aquila audax), penetrating the windscreen and causing significant damage to the propeller and engine, while also striking the pilot, who sustained serious facial injuries and was temporarily unable to see. The pilot, who was wearing a headset and spectacles (both dislodged and damaged during the impact), managed to land safely. 

Birdstrike and in-flight break-up involving a Bell 206L‑1, VH‑ZMF, near Maroota, New South Wales, on 9 July 2022 (AO‑2022‑034)

Shortly after departing from a private helipad, the helicopter was struck by a wedge‑tailed eagle (Aquila audax) just below the front left windscreen. The pilot, likely startled by the birdstrike and distracted by sun glare and a required radio frequency change, made abrupt control inputs that caused the main rotor to sever the tail boom, resulting in an in‑flight breakup and collision with terrain. The pilot, who was the sole occupant, was fatally injured.

Birdstrike and collision with terrain involving Air Tractor AT‑502B, VH‑KDR, 32 km east‑north‑east of Chinchilla Airport, Queensland, on 19 September 2022 (AO‑2022‑043)

During low-level aerial spraying at about 8 feet above ground, the aircraft was struck by a large Australian bustard (Ardeotis australis), which shattered the right windshield. The bird entered the cockpit, likely impairing the pilot’s ability to control the aircraft. The aircraft continued for approximately 310 m before colliding with terrain, resulting in the pilot being fatally injured and destruction of the aircraft.

Safety analysis

Birdstrike

Images from the accident site showed that the aircraft collided with a white‑bellied sea eagle (Haliaeetus leucogaster). The pilot had limited opportunity to detect the bird as they were looking down and to the left of the helicopter’s trajectory, so it was probably in their peripheral vision where detection of small objects is very limited. Even if they had been looking ahead at the time, they may not have been able to see the bird in time to avoid it due to the inherent limitations of the see-and-avoid principle. The closure rate to the soaring bird would have been around 94 kt and the difference in speed between them would have also made the relative trajectory almost direct. These factors further reduced the pilot’s ability to see the bird and change the helicopter’s flight path in time, likely rendering the collision unavoidable under the circumstances.

Considerations for aircraft operators and employers

Windshield impact resistance

The analysis of bird strike data highlights the significant safety risks posed to windshields. In windshield impacts in the United States, 14.4% caused serious injuries and 1.8% caused fatalities. Australia’s occurrences included 3 fatal and 3 serious injuries. Comparison of the United States and Australian data indicated that there was a higher chance of both birdstrike and the strike resulting in windshield damage per flight hour in Australia.  

There is an elevated risk for helicopter operations due to low‑altitude operations and often less robust windshield designs. This is because if a bird penetrates the windshield, it can directly impact occupants, causing injury or incapacitation of flight crew, which may lead to loss of aircraft control or further operational hazards. While advancements in windshield design, such as laminated materials and reinforced structures, have mitigated many impacts, the data highlights vulnerabilities in extreme cases. 

Manufacturers like Robinson and Bell have both released birdstrike‑rated windshields that provide higher impact resistance and significantly decrease the likelihood of objects breaching the windshield upon impact. However, these windshields have been rated to withstand a 1 kg bird strike at the aircraft’s never‑exceed speed, and the occurrence scenario involving a 3 kg bird colliding with the helicopter would likely exceed the windshield’s design limits. Nevertheless, and noting there are some disadvantages of impact‑resistant windshields, operators are encouraged to consider installing impact‑resistant windshields if operating in areas with a high probability of birdstrike.

Helmets

Helicopter pilots often wear helmets as a safety measure due to their frequent exposure to the dynamic conditions of rotary‑wing flight, where turbulence, rapid manoeuvres, and potential accidents pose risks of head injury. In contrast, passengers often do not wear helmets, as the risk is lower for occasional travellers, particularly considering the other safety measures associated with commercial passenger transport operations.

Passengers who travel frequently in helicopters fall between these 2 extremes. They are naturally exposed to a higher risk (over the occasional passenger) simply due to the increased number of flights. While the pilot reported being a helmet advocate and had previously discussed the potential benefits with the passenger, the decision whether to wear a helmet was ultimately left to the passenger’s discretion.

Helmets provide an additional layer of protection against birdstrikes, particularly in aviation scenarios like the Glasair Sportsman GS‑2 incident (AO‑2016‑001). A helmet, often equipped with a sturdy visor, can shield the face and head from small‑object impacts, reducing the risk of injury from a shattered windshield. Additionally, a helmet, especially one designed for aviation, is engineered to absorb and disperse kinetic energy from impacts with larger objects such as a bird potentially mitigating the severity of injuries like those sustained by the pilot of the Glasair, who was not wearing a helmet and suffered serious facial injuries. The helmet’s hard outer shell and padded inner liner work together to reduce the force transmitted to the skull, significantly lowering the risk of traumatic brain injuries, concussions, or skull fractures.

A helmet would not have prevented the passenger’s injuries in this case due to the impact location. Nevertheless, wearing a helmet as standard practice would provide some protection against a range of other potential hazards.

Pilot response

The pilot maintained control of the aircraft despite the sudden disruption and potential aerodynamic effects of the compromised windscreen. They promptly identified the nearest suitable landing site with access to medical facilities and executed a controlled descent and landing. 

The pilot’s effective response and adherence to emergency procedures ensured the injured passenger was positioned for immediate medical response, highlighting sound decision‑making under extreme circumstances. 

Findings

ATSB investigation report findings focus on safety factors (that is, events and conditions that increase risk). Safety factors include ‘contributing factors’ and ‘other factors that increased risk’ (that is, factors that did not meet the definition of a contributing factor for this occurrence but were still considered important to include in the report for the purpose of increasing awareness and enhancing safety). In addition ‘other findings’ may be included to provide important information about topics other than safety factors.  These findings should not be read as apportioning blame or liability to any particular organisation or individual.

From the evidence available, the following findings are made with respect to the birdstrike involving Bell 206L‑3, VH‑JMM, 16 km west-north-west of Lake Evella Aerodrome, Northern Territory, on 14 July 2025.

Contributing factors

• While cruising at about 900 ft above mean sea level, the helicopter struck a white‑bellied sea eagle, which passed through the windscreen and impacted the passenger.

Other factors

• Despite the injuries to the passenger and the damage to the aircraft, the pilot demonstrated composure and maintained control of the aircraft, enabling a calm and controlled return to a location where medical assistance could be provided.

Sources and submissions

Sources of information

The sources of information during the investigation included:

• the pilot
• Nautilus Aviation
• Northern Territory Police Service
• recorded data from the Spidertracks unit on the helicopter
• OzRunways.

References

Australian Transport Safety Bureau (2002). The Hazard Posed to Aircraft by Birds. Canberra: ATSB.

Debus, S. J. S. (2017). Australasian Eagles and Eagle-like Birds. CSIRO Publishing.

Ferguson-Lees, J., & Christie, D. A. (2001). Raptors of the World. Christopher Helm.

Hobbs, A. (1991). Limitations of the See-and-Avoid Principle. Canberra: ATSB. 

Marchant, S., & Higgins, P. J. (Eds.). (1993). Handbook of Australian, New Zealand and Antarctic Birds: Volume 2 - Raptors to Lapwings. Oxford University Press.

Washburn, B. E., Begier, M. J., & Wright, S. E. (2015). Wildlife strikes to civil helicopters in the United States, 1990–2011. Wildlife Society Bulletin, 39(1), 115‑120.

Submissions

Under section 26 of the Transport Safety Investigation Act 2003, the ATSB may provide a draft report, on a confidential basis, to any person whom the ATSB considers appropriate. That section allows a person receiving a draft report to make submissions to the ATSB about the draft report. 

A draft of this report was provided to the following directly involved parties:

• the pilot
• Nautilus Aviation
• Telstra
• Civil Aviation Safety Authority
• Northern Territory Police Force
• TSB Canada.

Submissions were received from:

• Nautilus Aviation
• Telstra

The submissions were reviewed and, where considered appropriate, the text of the report was amended accordingly.

Purpose of safety investigations The objective of a safety investigation is to enhance transport safety. This is done through:  identifying safety issues and facilitating safety action to address those issues providing information about occurrences and their associated safety factors to facilitate learning within the transport industry. It is not a function of the ATSB to apportion blame or provide a means for determining liability. At the same time, an investigation report must include factual material of sufficient weight to support the analysis and findings. At all times the ATSB endeavours to balance the use of material that could imply adverse comment with the need to properly explain what happened, and why, in a fair and unbiased manner. The ATSB does not investigate for the purpose of taking administrative, regulatory or criminal action. Terminology An explanation of terminology used in ATSB investigation reports is available here. This includes terms such as occurrence, contributing factor, other factor that increased risk, and safety issue. Publishing information Released in accordance with section 25 of the Transport Safety Investigation Act 2003 Published by: Australian Transport Safety Bureau © Commonwealth of Australia 2025   Ownership of intellectual property rights in this publication Unless otherwise noted, copyright (and any other intellectual property rights, if any) in this report publication is owned by the Commonwealth of Australia. Creative Commons licence With the exception of the Commonwealth Coat of Arms, ATSB logo, and photos and graphics in which a third party holds copyright, this report is licensed under a Creative Commons Attribution 4.0 International licence. The CC BY 4.0 licence enables you to distribute, remix, adapt, and build upon our material in any medium or format, so long as attribution is given to the Australian Transport Safety Bureau.  Copyright in material obtained from other agencies, private individuals or organisations, belongs to those agencies, individuals or organisations. Where you wish to use their material, you will need to contact them directly.

Executive summary

What happened

On the morning of 9 July 2022, a Bell 206 L-1, registered VH-ZMF departed a private helipad at Cattai, NSW for a private flight. About 9 minutes later, the helicopter impacted terrain about 10 km to the north of the departure point. The helicopter was destroyed, and the pilot, who was the sole occupant, was fatally injured.

What the ATSB found

The ATSB found that shortly after crossing Dargle Ridge at about 500 ft above the ground and while approaching the Richmond airspace control boundary, a wedgetail eagle impacted the helicopter just below the front left windscreen. It was unlikely that the pilot saw or had time to avoid the wedgetail eagle due to sun glare and a required radio frequency change.

The pilot was likely startled and initiated abrupt control inputs leading to the main rotor severing the tail boom. This led to an inflight break-up of the airframe and collision with terrain.

Safety message

Birdstrike is sometimes an unavoidable and relatively common hazard for all aviation operations, one which is more prevalent at lower altitudes. Pilots are reminded that sound lookout and visual scanning processes, as well as avoidance of low-level flight and expected areas of large concentrations of birds are key to reducing the likelihood of birdstrike.

Maintaining effective lookout and taking steps to remove, reduce or eliminate reduced visual effectiveness will assist in maintaining better situational awareness in-flight, and also assist in providing better outcomes to see-and-avoid not only birds, but other airspace users.

 

The investigation

Safety analysis

Sources and submissions

Purpose of safety investigations The objective of a safety investigation is to enhance transport safety. This is done through: identifying safety issues and facilitating safety action to address those issues providing information about occurrences and their associated safety factors to facilitate learning within the transport industry. It is not a function of the ATSB to apportion blame or provide a means for determining liability. At the same time, an investigation report must include factual material of sufficient weight to support the analysis and findings. At all times the ATSB endeavours to balance the use of material that could imply adverse comment with the need to properly explain what happened, and why, in a fair and unbiased manner. The ATSB does not investigate for the purpose of taking administrative, regulatory or criminal action. Terminology An explanation of terminology used in ATSB investigation reports is available here. This includes terms such as occurrence, contributing factor, other factor that increased risk, and safety issue. Publishing information  Released in accordance with section 25 of the Transport Safety Investigation Act 2003 Published by: Australian Transport Safety Bureau © Commonwealth of Australia 2023 Ownership of intellectual property rights in this publication Unless otherwise noted, copyright (and any other intellectual property rights, if any) in this report publication is owned by the Commonwealth of Australia. Creative Commons licence With the exception of the Coat of Arms, ATSB logo, and photos and graphics in which a third party holds copyright, this publication is licensed under a Creative Commons Attribution 3.0 Australia licence. Creative Commons Attribution 3.0 Australia Licence is a standard form licence agreement that allows you to copy, distribute, transmit and adapt this publication provided that you attribute the work. The ATSB’s preference is that you attribute this publication (and any material sourced from it) using the following wording: Source: Australian Transport Safety Bureau Copyright in material obtained from other agencies, private individuals or organisations, belongs to those agencies, individuals or organisations. Where you wish to use their material, you will need to contact them directly.

What happened

On the night of 3 July 2017, AirAsia X^[1] flight D7207, an Airbus 330 aircraft, registered 9M-XXT, taxied at Gold Coast Airport, Queensland for a scheduled passenger transport flight to Kuala Lumpur, Malaysia. On board the aircraft were two flight crew, 12 cabin crew and 345 passengers.

During the taxi to runway 32, all engine indications were normal.

At 2249 Eastern Standard Time, the flight crew commenced the take-off roll. Flight data recorder data shows that Engine 2 vibrations increased as the aircraft approached its take-off rotation speed. After take-off, passing approximately 2,300 ft, the electronic centralised aircraft monitor (ECAM) displayed an ENG 2 STALL alert. At the same time, loud banging noises associated with an engine stall could be heard in the aircraft. The flight crew commenced the ECAM actions for the ENG 2 STALL procedure and made a PAN PAN^[2] call to air traffic control.

As the aircraft continued climb to 4,000 ft, the ECAM displayed an ENG 2 FAIL alert. About this time the flight crew received an interphone call from the cabin purser advising of a ‘starboard engine fire’, which was visible from the aircraft cabin and had been reported to the purser by a company pilot, who coincidentally was travelling as a passenger.

In response to the ECAM alert and report from the cabin purser, the flight crew carried out the ENG 2 FAIL procedure with damage actions, including discharging the fire suppression system.

The flight crew upgraded the distress phase to a MAYDAY^[3] with air traffic control and requested a diversion and approach to runway 01 at Brisbane Airport for an overweight, single engine landing. The aircraft landed safely at 2310.

After the aircraft vacated the runway, the captain held the aircraft on the taxiway to allow the airport emergency services to inspect the engine before they taxied the aircraft to the arrival gate.

 

Information from the Gold Coast Airport operator

After the aircraft departed, the Gold Coast Airport operator performed a visual inspection of runway 32. Bird remains and engine debris were recovered on runway 32 around the intersection of taxiway D. This included one complete carcass, as well as additional debris from another bird. Other than the evidence of birds, no foreign objects were found with the potential to have resulted in the damage to the engine.

Video recordings of the runway were reviewed by the airport operator. That review identified flashes of flame emitted from the rear of engine 2 during the take-off ground roll, and the location of these flashes coincided with the area near where the bird remains and engine debris were collected. Tissue samples from the bird remains were sent to the Australian Museum, which identified the bird species as a masked lapwing (commonly known as a plover). A masked lapwing is a common medium-sized, 30–37 cm in length and weighing between 0.23–0.40 kg (see the ATSB Bird information sheet number 3 for more detail).

A post-mortem examination of the complete carcass by a veterinary specialist determined it was unlikely to have been struck by a moving object and its damage was likely the result of wake vortex. Examination of debris from the other bird identified no evidence of burning, which could be expected if the bird had been ingested into an aircraft engine.

Aerodrome bird hazard management

Part 139 of the Australian Civil Aviation Safety Regulations requires that aerodrome operators have procedures to deal with the danger to aircraft operations caused by the presence of birds on or near the aerodrome. This includes arrangements for assessing any bird or animal hazard and the removal of any such hazard. The operator of Gold Coast Airport had a comprehensive wildlife hazard management plan in place.

In 2017, the ATSB published a research report (AR-2016-063) titled Australian aviation wildlife strike statistics. The report provided information 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. For the 10-year period 2006 to 2015, this report stated that 480 birdstrikes (average of 48 per year) were reported to have occurred in the aerodrome confines at Gold Coast Airport. This equated to an average of 5.15 birdstrikes per 10,000 movements^[4] at Gold Coast Airport.

Most birdstrikes involving large air transport aircraft do not result in damage (about 95 per cent). About 10 per cent of birdstrikes involving aircraft with turbofan engines result in the bird being ingested into an engine.

Across Australia, the lapwing/plover family of birds has been the third most common bird/bat struck by aircraft across the 10-year period (868 strikes). About 5 per cent of strikes involving lapwing/plover birds have resulted in some aircraft damage, and about 15 per cent involved more than one bird being struck.

The Australian Airports Association published Managing bird strike risk species information sheets focused on managing the strike risk of several bird species at Australian airports. The information sheet for the masked lapwing stated that risk assessments often ranked these birds as moderate to very high risk due to their presence on airfields, particularly in critical aircraft movement areas such as flight strips, and their highly territorial behaviour. The sheet also noted that masked lapwings often loaf at off-airport locations during daylight hours before moving to airports at night to forage. This results in increased numbers flying on and around airports during periods of decreased visibility, thereby increasing the probability of a strike.

Masked lapwings can occur in large flocks in periods just prior to their breeding season. The ATSB Australian aviation wildlife strike statistics report states that birdstrikes involving lapwing/plover birds peak between 1900 and 2100 in the evening and 0700 to 1000 in the morning.

Statistics provided by Gold Coast Airport indicated that over the previous 12 months (July 2016 to June 2017), 237 masked lapwings had been dispersed and 34 culled. The figures for previous years were generally similar, although the figures for the period July 2015 to June 2016 were much higher. It was not unusual for the birds to not require active management for several days at a time, and none had been dispersed or culled in the 4 days prior to the occurrence. Throughout the remainder of July 2017, 35 were dispersed and 45 culled.

Engineering examination of the engine

The aircraft was fitted with two Trent 700 engines, manufactured by Rolls Royce.

After the occurrence, an engineering examination at Brisbane Airport found a single fan blade-tip section, approximately 140 mm x 125 mm, had fractured from one fan blade and the fan rear seal was found broken into pieces and scattered throughout the bypass areas of the engine (Figure 1). There was also evidence of fire within the engine.

Figure 1: Damage to Rolls Royce Trent 700 engine fan blades

Source: Rolls Royce

A sample of visible organic debris was taken from engine 2 in Brisbane and sent for DNA analysis. Testing of this sample was unable to provide a result. The reasons for this could not be determined, but are usually associated with a sample being affected by heat or storage conditions.

The engine was later shipped to Hong Kong for a controlled engine strip and detailed inspection by the engine manufacturer. Some key results of the inspection related to the fan blades included:

• The front section of the engine was subjected to an ultraviolet (UV) light inspection to highlight areas of organic debris for swabbing for DNA evidence of bird ingestion. The UV light identified that organic debris was present in a number of locations around the circumference of the fan blade set and in other areas of the engine. DNA analysis identified that this debris was from masked lapwing bird(s).
• UV light inspection identified that blade 1 (the blade with the released tip) had organic debris in the area near the blade-tip release (Figure 2), and there was also organic debris on the blade- tip that was recovered at Brisbane Airport. DNA analysis confirmed the debris from the blade and the blade-tip was from a masked lapwing.
• Based on the distribution of the debris and engine speed conditions, the engine manufacturer concluded that multiple birds had impacted the fan. However, the damage on or near blade 1 was consistent with impact with a single bird.
• Blade 1 exhibited cupping damage consistent with soft body impact close to the point of material release. The radial height of the fracture on the blade was in a leading-edge impact cup at approximately 84 per cent blade-height (Figure 1 and Figure 2).
• Laboratory analysis of the fracture surface of blade 1 confirmed the fracture mode as overload. There was no evidence of fatigue or pre-existing material deficiencies that could have contributed to the release of the blade-tip.
• There was blade damage on a blade adjacent to blade 1 (see to the right of the red square in Figure 1). This damage to the adjacent blade was consistent with impact from a hard body, and laboratory analysis did not identify that any foreign object had impacted that blade.

Figure 2: Ultraviolet light showing bird remains on damaged fan blade

Source: Rolls Royce

The engine manufacturer conducted a theoretical analysis to determine under what conditions an impact with a bird with a mass of 0.85 lb (0.39 kg), such as a masked lapwing, could have resulted in the discovered condition of the engine fan blade. The analysis used the engine and aircraft speed conditions at the time of the event (88 per cent N1^[5] and an aircraft speed of 120–140 kt) and modelled variations of strike position (radial height) and angle of incidence (bird orientation). Only one of the modelled scenarios matched the results of the occurrence event. This was a strike from a bird with the bird’s longitudinal axis aligned with the relative velocity of the blade^[6] at a radial height of 83 per cent.

The engine manufacturer concluded that the release of the blade-tip was the result of an impact from a masked plover.

In terms of other aspects of the engine examination, the engine manufacturer advised:

• The loss of material from a single blade caused the fan to run out of balance while the engine was at take-off thrust. This out of balance operation generated high levels of N1 vibration, as recorded on the aircraft’s flight data recorder.
• It is most likely that the outboard section of the fan rear seal released following contact between the rotating and static members, as a result of high thrust engine operation with the fan out of balance. Fragments of this seal likely entered the core of the engine leading to significant damage to the compressors. This resulted in a series of compressor stalls, which prompted the flight crew to reduce the engine thrust setting to idle in response to the ECAM ENG 2 STALL alert.
• At about the time of the ENG 2 STALL alert, the oil quantity on the affected engine diverged from that on engine 1. There was a loss of clamping across the front bearing chamber elastomeric oil seal, as a result of bolt unwinding. This loss of clamping allowed oil to leak from this location, and the oil ignited either by the frictional heat from the rubbing seals or the relative movement between the front bearing housing and the low-pressure roller bearing housing.
• The resulting oil fed fire established in the cavity between the front bearing housing and the fan disc. This fire caused failure and melting of aluminium alloy components in this cavity but was not sufficient to affect the structural engine parts made from materials with higher melting points that were in the same region. It is likely that once the bolts had fully unwound, the air pressure and oil feed conditions changed sufficiently so that the fire self-extinguished.

Engine design requirements

The Rolls Royce Trent 700 engine met the engine certification standards for the ingestion of birds. These requirements were outlined in the European Joint Aviation Regulation JAR-E 800. For medium-sized and small birds, these requirements stated that:

It shall be established that when the front of the Engine is struck by a number of medium sized birds… or small birds… there is no unacceptable immediate or ultimate loss of Engine performance, no serious increase of Engine operating temperatures or deterioration of Engine handling characteristics, over the full range of Engine operating conditions, and no dangerous physical damage…

Medium sized birds were considered to have a weight of 0.7 kg (or 1.5 lb) and small birds up to 0.11 kg. The specified test required the impact with a number of birds to be tested over a short duration (not more than 1 second), with the number of birds dependent on the size of the engine and the size of bird.

According to the engine manufacturer, what occurred to the engine during the occurrence flight:

• …is not as experienced during the medium bird certification test when 8 birds of at least 1.5lbs [0.68 kg] were fired into the engine at >168 kts with the bird trajectory longitudinally aligned with the engine...
• The certification test point is intended to demonstrate a level of capability in a worst-case situation of aircraft above decision speed (V1^[7]) but below 1500 ft, where the aircraft is committed to flight but has minimum amount of forward speed and is therefore dependent on engine thrust to climb safely…
• The certification birdstrike test is a benchmark test which demonstrates a level of engine capability as required by certifying authorities. The findings of this event do not undermine the capability of the Trent 700 engine with respect to birdstrike and the engine today would be expected to replicate the behaviour demonstrated during the previous test. The Trent 700 has experienced over 430 reported in-service birdstrike events with only five events resulting in fan blade material loss, all except this event were caused by birds greater than 2.5lb [1.14 kg].
• It is concluded that in this event a rare combination of 0.85lb bird ingestion at adverse forward speed during the take-off roll (close to V1 but lower than VR^[8]) and angle of incidence combined to cause the release of a small section of blade which [led] to the engine producing only idle thrust after approximately 2 minutes and leading to commanded shutdown approximately 4 minutes after the release of fan blade material.

Safety analysis

Based on the available evidence, the engine failure was concluded to be the result of a birdstrike involving a masked lapwing. As the remains of the two birds found on the runway did not show signs of being involved in an engine ingestion, the engine failure was almost certainly a result of an additional bird.

The ATSB reviewed the aircraft’s flight data recorder, cockpit voice recorder and statements from the flight crew. From these data sources the ATSB determined that the flight crew effectively managed the abnormal situation and diversion. The cabin purser relayed to the flight crew relevant information about a possible number 2 engine fire observed from within the cabin. This information assisted the decision-making of the captain.

Although aircraft engines are designed to withstand most types of birdstrikes, including those involving medium-sized birds such as a masked lapwing, this event appeared to involve a rare scenario comprising a combination of aircraft and engine speeds, the height of the fan blade at which the birdstrike occurred, and its angle of incidence. It is extremely unlikely such a scenario would occur on multiple engines simultaneously.

Findings

These findings should not be read as apportioning blame or liability to any particular organisation or individual.

• During the take-off the number 2 engine was subjected to a birdstrike, which resulted in the release of a small section of a fan blade.
• Following an ECAM ENG 2 FAIL alert, the flight crew shut down number 2 engine, advised air traffic control of the situation and diverted to land as soon as possible at Brisbane Airport.

Safety action

Whether or not the ATSB identifies safety issues in the course of an investigation, relevant organisations may proactively initiate safety action in order to reduce their safety risk. The ATSB has been advised of the following proactive safety action in response to this occurrence.

Rolls Royce

Following this occurrence, the engine manufacturer met with the European Aviation Safety Agency, the certifying authority for the engine, to discuss the event and the manufacturer’s investigation.

The engine manufacturer also advised that its Trent 700 project team will review the design of the fan rear seal and the low-pressure roller bearing bolts to determine if there is a feasible solution to prevent the loss of a small section of fan blade leading imminently to an engine shutdown.

AirAsia X

As a result of this occurrence, AirAsia X advised the ATSB that it had conducted its own internal investigation. The occurrence information will be shared with flight crew in recurrent training programs and used to enhance simulator training exercises.

Safety message

This occurrence highlights the importance of effective crew resource management techniques, including cabin crew passing on pertinent information to flight crew, and robust emergency procedures. Additionally, regular proficiency checks in the simulator, including engine failure scenarios, allow flight crew to respond appropriately in the event of such an occurrence in flight.

About this report Decisions regarding whether to conduct an investigation, and the scope of an investigation, are based on many factors, including the level of safety benefit likely to be obtained from an investigation. For this occurrence, a limited-scope, fact-gathering investigation was conducted in order to produce a short summary report, and allow for greater industry awareness of potential safety issues and possible safety actions. Publishing information  Released in accordance with section 25 of the Transport Safety Investigation Act 2003 Published by: Australian Transport Safety Bureau © Commonwealth of Australia 2018 Ownership of intellectual property rights in this publication Unless otherwise noted, copyright (and any other intellectual property rights, if any) in this report publication is owned by the Commonwealth of Australia. Creative Commons licence With the exception of the Coat of Arms, ATSB logo, and photos and graphics in which a third party holds copyright, this publication is licensed under a Creative Commons Attribution 3.0 Australia licence. Creative Commons Attribution 3.0 Australia Licence is a standard form licence agreement that allows you to copy, distribute, transmit and adapt this publication provided that you attribute the work. The ATSB’s preference is that you attribute this publication (and any material sourced from it) using the following wording: Source: Australian Transport Safety Bureau Copyright in material obtained from other agencies, private individuals or organisations, belongs to those agencies, individuals or organisations. Where you wish to use their material, you will need to contact them directly.

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1. AirAsia X is the medium and long-haul, low-cost affiliate carrier of the AirAsia Group. AirAsia X is based in Malaysia and operates a core fleet of A330-300 aircraft.
2. PAN PAN: an internationally recognised radio call announcing an urgency condition which concerns the safety of an aircraft or its occupants but where the flight crew does not require immediate assistance.
3. MAYDAY: an internationally recognised radio call announcing a distress condition where an aircraft or its occupants are being threatened by serious and/or imminent danger and the flight crew require immediate assistance.
4. Movement refers to the combination of departures and landings.
5. N1: the rotational speed of the low pressure compressor in a turbine engine.
6. This vector is a combination of the blade’s rotational speed and the aircraft’s forward speed. It will generally be significantly different to the aircraft’s flight path.
7. V1: the critical engine failure speed or decision speed required for take-off. Engine failure below V1 should result in a rejected take off; above this speed the take-off should be continued.
8. VR: the speed at which a positive, nose-up, movement of an aircraft about the lateral (pitch) axis is commenced immediately before becoming airborne.

What happened

On 24 December 2015, the pilot of a Glasair Sportsman GS-2, registered N666GM, was conducting a private flight from Southport, Queensland, to Moruya, New South Wales (NSW). The pilot was the only person on board.

The pilot landed at Mudgee, NSW, to add fuel, before continuing to Moruya. While en route between Mudgee and Moruya, the aircraft collided with a large bird, believed to be a wedge-tailed eagle. At the time of the birdstrike, the aircraft was cruising at about 5,500 ft above mean sea level,^[1] over mountainous terrain, and below a solid layer of cloud. The autopilot was engaged, but not in a mode that would hold a set altitude. The airspeed was about 140 kt.

The bird broke through the windscreen on the left side of the aircraft and struck the pilot. The collision left the pilot with serious facial injuries and they were temporarily unable to see (due to the effects of the impact). The pilot had been wearing a headset and spectacles, which were both dislodged and damaged during the collision.

Following the birdstrike, the aircraft entered an uncommanded and rapid descent. The extreme wind-rush and noise, combined with the effects of their serious injuries, meant that the pilot was not immediately aware that the aircraft was descending.

Despite the extreme circumstances, the pilot recovered sufficiently to manually override the autopilot and control the aircraft sufficiently to prevent a collision with terrain. Although the pilot continued to have difficulty seeing, they were able to apply full power and establish the aircraft in a climb. Following recovery from the initial urgency of the situation, the pilot was able to settle the aircraft in level flight, clear of the surrounding terrain.

The pilot elected to leave the autopilot engaged to assist with aircraft control, because the circumstances made it extremely difficult to continuously monitor airspeed and the flight path of the aircraft. With the autopilot still engaged, the pilot made overriding manual corrections to the flight path as required.

The pilot was able to locate the microphone of the headset by following the headset cord (by hand). The headset itself was substantially damaged and the pilot could only locate the microphone and one broken ear-cup. The pilot transmitted a MAYDAY^[2] call using the damaged headset, hopeful that the microphone was functional despite the apparent damage. Air traffic control (ATC) received the MAYDAY call at about 1300 Eastern Daylight-saving Time (EDT) (see later section titled Air traffic control aspects).

Under the circumstances, the pilot was unable to ascertain an accurate position, so just referenced Mudgee and Moruya in the MAYDAY call. Damage to the headset prevented the pilot receiving transmissions, so they were unable to hear any acknowledgement of the MAYDAY call, and consequently were unsure if the transmission was successful. In addition to the MAYDAY call, the pilot attempted to communicate with an associate via a text message, in the hope that their associate may be able to alert relevant authorities.

The pilot succeeded in navigating the aircraft away from the more mountainous terrain. The aircraft was still tracking towards Moruya, but because Moruya was over an hour away, and with high terrain en route, the pilot began considering diversion options. By referencing an iPad mounted in the cockpit, the pilot was able to identify a built-up area, and track towards that area in anticipation of being able to locate an aerodrome. The pilot sent another text message to their associate with updated information, and made another MAYDAY call. Although uncertain at the time, the pilot believed that the built up area was the city of Bathurst, and was broadly aware of the location of Bathurst Airport relative to the city.

The pilot had been flying with the autopilot engaged, holding a high nose attitude, at relatively low airspeed (with the engine at full power) to try to reduce the wind rush and noise. The pilot had also selected half flap, to provide some margin over the aerodynamic stall^[3] speed. Although concerned about aircraft controllability and the effect of their injuries, the pilot disconnected the autopilot in order to navigate the aircraft towards the anticipated location of the airport. While handling the aircraft carefully, mindful that the birdstrike may have damaged the wings and/or tail section of the aircraft, the pilot was able to locate and overfly Bathurst Airport.

Although unable to see the windsock, the pilot decided that runway 35 was the preferred runway under the circumstances. The pilot made another emergency (MAYDAY) call and positioned the aircraft for a landing via a wide circuit. Despite continuing problems with the wind-rush and noise, and the effect their injuries, the pilot concentrated on maintaining a safe airspeed during the approach, and landed successfully.

After landing, the Airport Safety Officer met the aircraft and provided the pilot with parking instructions. The pilot shut the aircraft down and medical services were called. Aside from the damage to the windscreen (Figure 1) and some relatively minor marks around the propeller, there appeared to be no other damage to the aircraft. The remains of the bird were retrieved from the cockpit (Figure 2).

Figure 1: Damage to the aircraft windscreen

Source: Bathurst Airport Staff

Figure 2: Some of the bird remains retrieved from the cockpit

Source: Pilot

Pilot comments – use of the autopilot

At the time of the birdstrike, the autopilot was set to hold the heading selected by the pilot, and neutral/zero vertical speed (level flight). This was in anticipation of entering a climb and manoeuvring when a suitable gap appeared in the overlying cloud cover. In this mode, however, the autopilot allowed the aircraft to descend rapidly following the birdstrike. The pilot believed that had the autopilot been set to hold a specific altitude, the aircraft may have maintained that altitude rather than entering an uncommanded descent. Under the circumstances, given the extent to which the pilot was incapacitated (particularly immediately following the birdstrike), altitude hold mode may have been preferable.

Additionally, the pilot believed that continuing to use the autopilot following the birdstrike was a good strategy, given the effect of their injuries and their inability to see clearly. While use of the autopilot reduced the likelihood of a loss of control, the pilot was still able to manually override the autopilot to adjust the flight path of the aircraft as required.

Air traffic control aspects

The pilot’s initial MAYDAY call indicated that the aircraft had been involved in a birdstrike and that the pilot was unable to see. The call also included reference to aircraft control difficulties and mentioned Mudgee and Bathurst. ATC acknowledged the call and initiated a Distress Phase.^[4] ATC requested the callsign and location of the aircraft, which were not included or not clear from the MAYDAY call, but there was no response from the pilot. ATC attempted to establish contact with the incident pilot through the pilot of another aircraft who also heard the MAYDAY call, but those attempts were also unsuccessful. ATC also asked the pilots of other aircraft in the area to maintain a listening watch on relevant frequencies.

The pilot of the incident aircraft transmitted another MAYDAY call about a minute after the initial call, indicating that the aircraft was over hills and the windscreen was broken. The pilot added that they had no headset, and repeated that they were unable to see. No further calls or details were received by ATC from the pilot.^[5]

Among other activities in response to the situation, ATC contacted the Airport Safety Officer at Bathurst Airport to see if they were aware of any aircraft that was missing or experiencing difficulty. At that point, the Airport Safety Officer was unaware of the situation, and unable to provide any information.

At about 1330, the Airport Safety Officer at Bathurst airport contacted ATC to advise that an aircraft with a broken windscreen was in the process of landing. Several minutes later, they called ATC again, this time to inform them that the aircraft had landed at Bathurst. The Airport Safety Officer was able to provide more relevant information, following which ATC cancelled the DISTRESFA.

ATSB comment

In 2014, the ATSB published a research report (AR-2014-075) titled Australian aviation wildlife strike statistics.The report provides some insights into the nature and characteristics of birdstrikes, and comments that a birdstrike involving a general aviation aircraft is more likely to cause aircraft damage than a birdstrike involving an air transport category or military aircraft.

The August 2010 edition of the Flight Safety Foundation magazine, AeroSafety World, includes an article titled Bird Strike Mitigation Beyond the Airport. The article includes some comments relevant to this occurrence, including:

While general aviation airplanes typically do not have the same engine ingestion concern as transport category jets, their overall design and certification make them much less able to resist damage from bird strikes. Mid-size to large birds can penetrate the windshields and can cause pilot incapacitation or disorientation, resulting in loss of control. The drag caused by the loss of the windshield has also resulted in accidents because enough thrust is not always available to overcome the huge drag increase. Likewise, collision-caused deformation of wing or tail surfaces can increase stall speed considerably and affect handling qualities, especially at slower speeds.

If birds are encountered en route, on climb or descent, the flight crew should pull up — consistent with good piloting technique — to pass over the birds. If birds see the aircraft, they will treat it as an obstacle, but may misjudge the closing speed because the threat is usually beyond their experience.

Birds may turn or dive as avoidance maneuvers, but they rarely climb. So pulling up is the best and fastest avoidance maneuver.

Safety message

Birdstrikes continue to present a serious hazard to aviation, and can cause substantial damage. Such damage has the potential to significantly adversely affect the performance and handling qualities of an aircraft. In this case, despite the damage to the aircraft and their injuries, the pilot effectively managed an extremely challenging situation, resulting in a positive outcome.

This accident highlights to pilots the importance of regular position updates with respect to in-flight diversion options. An ongoing awareness of diversion options may assist pilots in dealing effectively with a stressful and challenging in-flight emergency, particularly where time is critical.

When declaring an emergency, pilots are encouraged to relay as much relevant information as reasonably possible. Although in this event, the damage to the aircraft and injuries to the pilot made all communications very difficult, positional information and information with respect to the intentions of the pilot may be critical to an effective response by emergency services.

Aviation Short Investigations Bulletin - Issue 49

Purpose of safety investigations The objective of a safety investigation is to enhance transport safety. This is done through: identifying safety issues and facilitating safety action to address those issues providing information about occurrences and their associated safety factors to facilitate learning within the transport industry. It is not a function of the ATSB to apportion blame or provide a means for determining liability. At the same time, an investigation report must include factual material of sufficient weight to support the analysis and findings. At all times the ATSB endeavours to balance the use of material that could imply adverse comment with the need to properly explain what happened, and why, in a fair and unbiased manner. The ATSB does not investigate for the purpose of taking administrative, regulatory or criminal action. Terminology An explanation of terminology used in ATSB investigation reports is available here. This includes terms such as occurrence, contributing factor, other factor that increased risk, and safety issue. Publishing information  Released in accordance with section 25 of the Transport Safety Investigation Act 2003 Published by: Australian Transport Safety Bureau © Commonwealth of Australia 2016 Ownership of intellectual property rights in this publication Unless otherwise noted, copyright (and any other intellectual property rights, if any) in this report publication is owned by the Commonwealth of Australia. Creative Commons licence With the exception of the Coat of Arms, ATSB logo, and photos and graphics in which a third party holds copyright, this publication is licensed under a Creative Commons Attribution 3.0 Australia licence. Creative Commons Attribution 3.0 Australia Licence is a standard form licence agreement that allows you to copy, distribute, transmit and adapt this publication provided that you attribute the work. The ATSB’s preference is that you attribute this publication (and any material sourced from it) using the following wording: Source: Australian Transport Safety Bureau Copyright in material obtained from other agencies, private individuals or organisations, belongs to those agencies, individuals or organisations. Where you wish to use their material, you will need to contact them directly.

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1. The aircraft was over mountainous terrain at the time of the birdstrike, suggesting that the height above ground level was substantially less than 5,500 ft.
2. MAYDAY is an internationally recognised radio call for urgent assistance.
3. Aerodynamic stall is a term used when the wing is no longer producing enough lift to support the weight of the aircraft.
4. A Distress Phase (DISTRESFA) is an emergency phase declared by ATC when there is reasonable certainty that the aircraft and its occupants are threatened by grave and imminent danger and require immediate assistance.
5. The pilot remembered making more emergency calls than the two initial MAYDAY calls, but ATC did not receive the later calls.

 

The aircraft was in the circuit area when it struck a pelican with the leading edge of the left wing. The approach was continued and the aircraft landed without further incident. Inspection found that there was a 500mm long tear in the wing skin about one metre from the wingtip. The metal had been pushed back to the front wing spar.

The helicopter flew through a flock of birds. The pilot felt and saw a number of birds strike the main rotor and also saw bird remains travel rearwards after this main rotor contact. After a short time of further flight with no apparent problems, the pilot heard a "bang" from the rear of the aircraft. He saw that the rear of the aircraft was vibrating so elected to land immediately. During the landing, the tail rotor contacted the ground.