The industry’s greatest threat?

Flight 1549, ‘The miracle on the Hudson’ brought the risks aircraft face from birdstrikes to a worldwide audience. For those involved in managing this risk, it merely re-confirmed the potentially catastrophic consequences such events can have.

Birdstrikes are not an uncommon feature of air travel. Thousands of events occur around the world each year with the vast majority having little or no impact upon a flight. Managing the risks from events that do have the potential to cause damage, however, requires an understanding of how birds behave, what it is that attracts birds to a given environment, and what techniques and measures can be deployed to reduce the likelihood of a strike? Risk assessment therefore becomes the key driver for determining how and where management resources should be best deployed.

Whilst this process had lagged behind many other areas of the aviation industry, there are now very well accepted methods used for identifying birdstrike risks. Wherever possible, recording the type of bird involved in a strike is critical to this process. Modern techniques mean there is now virtually no reason for not being able to identify the species of bird involved in a strike. Local ornithological experts, for example, can identify whole birds where carcasses are found following a strike. Specialist organisations such as the Smithsonian institute in the USA or FERA based in the UK routinely use microscopic feather identification techniques to identify the smallest fragments of remains collected after a strike, whilst modern developments now deploy DNA methodology to classify strikes when only blood stains or no feather fragments are left on a fuselage or collected from an engine. Data from actual birdstrikes occurring at an airfield provide by far the best means of determining which species are present and being struck at individual aerodromes. A combination of simple physics and bird ecology, however, drives the management process.

Impact

When an aircraft hits a bird, the impact forces increase as the speed of the aircraft rises. Kinetic energy (described as ½ MV2 where M = mass of the bird and V = velocity of the strike), is the key to understanding how birds have the potential to cause so much damage to aircraft. Because the mass is halved and the velocity is squared, speed becomes much more important than mass. An aircraft on take-off, for example, may have engines rotating at 10,000rpm compared to 2,000rpm on landing. Similarly, a large passenger jet will have a take-off speed of around 160-180mph compared to a cruising speed of over 500mph. Engine strikes on take-off, or strikes with birds at high altitude therefore have the potential to cause far higher levels of damage than aircraft on low level approach. Fortunately, the vast majority of birds remain close to, or on the ground for the vast majority of the time and the habitats they choose to frequent can be largely managed within the aerodrome environment. When, for example, wetland birds are being struck at an airport, initial management action should determine whether there are any attractions present on the airfield that may be favourable to those species. Swales, ditches and balancing ponds, for example, may result in open water that provides an apparently safe environment for birds to roost or loaf (sit around) during the day. Management action can involve improved drainage, diverting water underground or simply netting over such areas to prevent access. Either way, it is a controllable issue and like most attractions, can be managed out of the airport environment.

Some issues will always remain. Most airports have vast expanses of open grassland which themselves can provide a home for invertebrates and a seed bank suitable for foraging birds. Modern cultivars and selective seeding methods, however, perhaps represent one of the biggest developments in airfield habitat management in recent years. Grass species can be selected for different soil types, airfield locations and climates to ensure a dense upright sward that repels as many problem species as possible have been developed. In New Zealand, grasses have been developed which contain an endophytic fungus that produces a natural insecticide and results in ‘digestive malaise’ (feeling nauseous), when eaten by animals and birds. Less insects and unpalatable grass means less birds on an airfield. Modern grass developments may provide a new opportunity to continue reducing the attractions of birds to airfields.

Deterrence

Assuming that the birds that are being struck at an airfield have been identified and the features that attract those birds to an airfield have been minimised, the final issue is to ensure that any remaining birds are deterred from using the airfield. It is a simple enough concept to envisage, yet probably one of the most difficult options to achieve; a bird free aerodrome. Whilst the holy grail of bird control techniques remains to be found, the key factor remains the dedication of staff and individuals who deploy deterrence. It is their knowledge of bird behaviours, deterrence techniques, legal options and implementation that determine how well any remaining residual risks are managed. Raptors (hawks, falcons and other birds of prey), do not respond to traditional deterrence methods such as distress calls or pyrotechnics, breeding waders will crouch low in the grass to avoid detection, gulls will circle and approach a vehicle playing a distress call, whilst pigeons will fly directly away from any form of deterrence implemented. Without understanding the responses of the birds themselves to the measures implemented, detterence staff are immediately at a disadvantage to the birds. One of the more recent developments has been the use of bird deterrence laser systems. With pilots reporting ever increasing problems with dazzling from laser pointers, the use of such systems on airfield need to be treated with great care, however, they do provide a modern day tool that can be particularly useful for dispersing flocks of birds at night. Redressing this balance is key to modern day good bird management and proper training of staff is becoming key to developing best practice. This remains, however, an area requiring further attention as many countries do not have a recognised standard for bird control qualifications despite the fact that international groups of experts eg the International Birdstrike Committee (IBSC), state that airport bird control personnel should be “properly trained”.

Technology

Once effective bird deterrence measures are in place on the airfield, logging and monitoring the effects of such actions provides the metric by which the effects of control can be measured and implemented within a safety management system. Developments in both hardware and software technologies mean that the traditional paper ‘bird log’ has now been largely usurped by computer based recording systems that automatically record the location and time any record is inputted as well as allowing the technique and response of birds to be recorded. A tool that was traditionally used to provide evidence that bird control was being implemented at an aerodrome now provides a whole dataset from which key risk areas can be identified and additional resources deployed. With suitable training, hard work and commitment of resources, the vast majority of birdstrike risks can be removed from the airfield environment.

Monitoring

This does not infer, however, that the issue has been resolved. Canada Geese on migration flying at an altitude of 3000 feet (such as those that were struck by flight 1549 with such devastating consequences), cannot be controlled by an on-airfield unit. In fact, with populations of some large bird species’ populations expanding around the world and many species becoming urbanised in nature, many birdstrike rates are on the increase. Understanding where birds move to and from, the times of movements and the seasonality of movements is essential for evaluating risk and managing environments. Monitoring populations off the airfield is becoming equally important to controlling birdstrike risks on the airfield. It is in this field that technological advancements may be developing towards a successful outcome.

• The European Space Agency (ESA), is looking at the potential for space technologies to identify bird rich areas around aerodromes to model bird movements and predict risk
• A network of military radar systems are currently used across European airspace to monitor mass bird migration events over the continent
• Individual radar systems have now been developed and deployed at airfields around the world that can be used to identify bird movements within the near environment

These radar technologies perhaps represent one of the biggest breakthroughs in recent years. Whilst radar has always had the ability to detect birds, it is only in recent years that smaller dedicated systems have been developed to monitor specific problems. In Durban, South Africa, for example, bird detection radar was deployed to highlight key risk periods associated with the daily roost dispersal of over three million Barn Swallows adjacent to the airport. In Kinloss, Scotland, a similar system has been in position to confirm the movements of local geese populations around a military airbase. Adjusting aircraft flight patterns represents perhaps the final option in avoidance but can only be done when risk is predicted accurately.

Notification

How information is interpreted or used becomes critical to the fight against birdstrike risk. Hazard warning systems such as ‘Notice to Airmen’ (NOTAMS) can be beneficial but the notification ‘Increased Bird Activity’ provides information only and does not require a specified action. It relies on individuals to judge the best way forward. If in the majority of cases, no actual birdstrikes occur or risk levels are not seen to be increased, users will begin to ignore the warnings. One of the key developments required within the industry is, therefore, to provide the evidence base by which accurate predictions of risk can be achieved. A pilot, for example, would not initiate a take-off if they could see a flock of geese sat on the runway in front of them. If a system was in place that warned of a flock of geese currently flying towards the airfield, however, it is not known whether they would continue and meet an aircraft at V1 (take-off decision speed), or deviate and avoid an aircraft altogether. Accurate prediction techniques and subsequent protocols for responding to predictions are therefore required.

Behaviour

Of key importance, however, is the behaviour of bird species themselves. Many birds appear to develop avoidance behaviours that reduce the probability of a strike. At a major European airport, for example, tens of thousands of gulls stream across a runway threshold every evening in winter on their return from feeding sites to their local roosts. Strikes during these periods are, however, extremely rare as birds literally wait for arriving or departing aircraft to pass before crossing the runway. Contrastingly, juvenile birds of the same species are routinely struck in July and August each year despite very few birds being present. They have simply not learned of the risks aircraft pose to their safety. Waterbirds appear faster and more direct in their flight patterns and are perhaps less able to initiate avoidance strategies. The behaviour of the same or different species at different times of year and by different ages can therefore have a dramatic impact on strike risk.

The future

For the near-term future, using the techniques available to monitor and predict movement of birds around airfields allows the habitats they are utilising to be clearly identified. Direct action to prevent sites linking bird movements across airspace environments may therefore, extend the deterrence successes of on-airfield bird control units and increase the safety buffer around airfields. Having a domestic waste landfill facility 10 miles to one side of an airfield and a suitable roost site for gulls 10 miles to the other, is currently well outside the remit of international standards for airfield influence, yet a 20 mile range for gulls, for example, is well inside their daily tolerances for a round-trip of winter foraging.

There have, therefore, been some excellent developments in the implementation and monitoring of wildlife hazard management issues on and around airports over the past decades. Tools and methods are available and it is clear that on-airfield bird control through careful habitat management and the dedicated actions of individuals around the world we are capable of creating significant and continued reductions in risk. The development of off-airfield strategies in combination with advanced monitoring techniques to help accurately predict strikes represents the next phase in birdstrike avoidance and the potential to increase further, the safety benefits already being seen.

Further reading

www.int-birdstrike.org

http://iap.esa.int/flysafe

http://fera.defra.gov.uk/wildlife/birdManagement/

http://en.wikipedia.org/wiki/US_Airways_Flight_1549

http://www.icao.int/nacc/meetings/2009/ECARDCA22/docs/ ecardca22ip22.pdf

http://www.mnh.si.edu/exhibits/birds_sin/index.html

About the Author

Andy Baxter is a trained biologist who has worked on ways to reduce the number of bird strikes at airports for over 10 years. He is currently leader of the bird strike avoidance team at the UK Food and Environment Research Agency (FERA) and is an expert on gull control at airports, urban settings and landfill sites.