Distress calls don’t stop them, nor do pyrotechnics, lasers, shotgun blasts, cracking whips or introduced predators. Even the dulcet tones of Tina Turner, blared around a British aerodrome, are not enough to keep birds and aircraft apart.
Five years on from the most infamous of bird strike incidents, Captain Chesley ‘Sully’ Sullenberger, the pilot who guided a powerless Airbus A320 carrying 150 passengers into the Hudson River after a devastating encounter with a flock of Canada geese, says the near-fatal collision ‘could happen again tomorrow’.
Birds are the single most dangerous enemy of the United States Air Force. In the 1990s, the USAF lost 17 aircraft in combat with foreign powers, ranging from Iraq to Serbia: in the same period it lost 12 to bird strikes.
Wildlife-related incidents accounted for 23 per cent of all non-serious incidents for civilian air transport between 2002 and 2011. The Australian Transport Safety Bureau, (ATSB) reports that bird strikes have doubled over the last decade, driven by an increase in high-capacity aircraft movements, along with improved strike reporting, increasing urbanisation and faster, quieter aircraft.
In Australia, there is the additional hazard of wildlife strikes in general, including the many species of flying foxes and other bats who call large parts of the continent home, with incidents being recorded everywhere except Tasmania. In theory, bats pose a greater risk to aircraft because they have the dense bone structure of mammals, rather than the lightweight pneumatised bones of birds. This means a bat strike would have a more concentrated impact force, increasing the likelihood of damage to an aircraft.
Bat strikes are also the most common type of wildlife strike, with the ATSB recording 767 incidents between 2002 and 2011. Plovers follow closely with 760, and galahs complete the top three with 729.
Galahs were most commonly involved in strikes of multiple birds, due to their flocking tendencies and their slow, erratic flight behaviour. They were voted the ‘most dangerous bird’ by Australian aerodromes. However, the potential for a strike to cause aircraft damage increases with the size of the animal-the bigger it is, the more likelihood of damage. Galahs are relatively small (330g) compared to what else is out there.
The Australian bustard (6,900g), brolga (6,700g), black swan (6,270g), Australian pelican (5,500g) and the Cape Barren goose (5,000g) are the heaviest birds in the sky and all have high hazard rankings. Ironically, so does the flightless emu. One of our national icons represents a major risk due to its size (37,500g) and has caused plenty of close calls, particularly in rural destinations. In 2005, an emu strike incident was recorded in Western Australia.
However, wildlife on the ground, not in the air, is rated as the most problematic by Australian aerodromes, with kangaroos and wallabies topping the list. Although the frequency of animal strikes is low, due to the much larger size of ground-dwelling animals, damage is more likely.
For the Royal Flying Doctor Service, the risk of kangaroos bounding onto a desolate runway has become a dangerous and expensive reality, with three strikes over the last 12 months in Queensland alone, the most recent occurring 200 km west of Rockhampton at Blackwater Airport. As the plane carrying a patient came in for landing it hit a kangaroo and juddered to a halt. Luckily, no one was injured, but the kangaroo and the RFDS’s finances were less fortunate. ‘The engine will require a full strip-down’, an RFDS spokesperson said. ‘I don’t know the exact extent, but the last one cost $200,000’.
This snapshot of just one incident illustrates the expense faced by aviation when animals are unfortunate enough to find themselves at the business end of a propeller, or a jet engine. Worldwide, bird strikes alone cost the aviation industry US$1.2 billion each year.
Globally, momentum is building to implement a whole-of-industry approach to managing the bird strike risk, but current management models focus principal responsibility on the airport operator, with regulations varying depending on the country. In Australia, despite the frequency of bird strikes, very few airport operators rated the risk at their airport as high. In fact, most respondents to a 2011 CASA survey rated the risk posed by wildlife as low, with larger aerodromes more likely to report a medium risk (46 per cent).
Eighty per cent of certified aerodromes have wildlife hazard management plans (WHMP) in place, compared to only 20 per cent of registered aerodromes. No doubt the ability to allocate resources to a separate wildlife management plan has a bearing on whether one is implemented or not.
As Sullenberger says, ‘There’s this constant tension between doing what’s easiest, what’s quickest, what’s least costly, versus taking the time, making the effort, to do the right thing. But I think many are hoping we can continue to be lucky.’
Science is working to take luck out of the equation. A 2013 paper by three mathematicians from Beihang University, in China, proposed a new model, based on the mathematics of chaos theory, to predict bird behaviour in real time.
This model could lead to ‘bird strike risk assessment at airports with the detected data (e.g. data from radar systems), including the estimation of bird strike probability and collision severity,’ the authors say.
Principal consultant at Avisure Australia, Kylie Patrick, argues the need for an integrated approach to bird strikes. In a recent paper she says ‘There is no single management tool that will “solve” the bird strike problem’.
Instead, Patrick says all WHMPs should include active and passive forms of deterrents, along with involving stakeholders in co-developing risk mitigation strategies. These, along with training about and comprehensive reporting of all bird strike incidents, are cornerstones of long-term management plans.
Mention of bird control quickly gives rise to the contentious and highly sensitive issue of culling. Patrick acknowledges that ‘lethal control of hazardous birds is a useful and important component of management programs’, but she also says ‘reliance on only one or two devices quickly results in habituation by birds, significantly reducing their effectiveness, and ultimately having minimal, or no, influence on the strike rate.’
While shooting remains the most popular removal method used by Australian aerodromes, it generally complements other preventive measures such as grass, water, waste and tree modification, as well as auditory and visual repellents.
Bird strikes will always be part of aviation life-a war waged on birds would be unwinnable, not to mention ecologically and ethically unsustainable. No amount of killing or relocation alone will negate the possibility of aircraft coming into contact with one or more of the thousands of local wildlife species. Likewise, the killing of kangaroos and other ground-dwelling animals is a flawed ‘quick-fix’ solution if nothing is done to address and remediate the underlying issues.
Part 139 of the Australian Civil Aviation Safety Regulations requires certified aerodromes to have procedures in place for dealing with birds posing a danger on and around the aerodrome. Aerodromes, both certified and registered, are encouraged to implement a wildlife hazard management plan that incorporates various deterrent methods to mitigate the chance of bird and wildlife strikes.
Journal of Risk Research, Special Issue: Land, Sea and Air Transport Risk. Volume 16, Issue 5, 2013 Bird strike hazard management programs at airports – what works? – Kylie Patrick, and Phil Shaw, Avisure Pty. Ltd., Australia
In March 2013, a Mooney M20J was returning to Hedlow airport, near Rockhampton, Queensland. As the pilot came in to land, two large birds emerged from knee-high grass near the runway and one hit the left wing of the small aircraft. The pilot reported that the aircraft yawed slightly left, the left wing dropped, and he applied opposite aileron to maintain wings level. The pilot decided to go around and momentarily glanced inside the cockpit to confirm that the engine controls were in the full forward position. When he looked outside again, the pilot noticed the aircraft had drifted to the right of the runway into an adjacent paddock. As the pilot reached over to raise the landing gear lever, the aircraft’s left wing struck a bull.
Damage to the aircraft was substantial-and the bull had to be put down.
The Australian Transport Safety Bureau (ATSB) has identified a total of 340 animal strikes between 2002 and 2011, with six involving livestock, and half of these occurring at aerodromes where there is no clear separation (such as perimeter fencing) from the surrounding environment.
In a conversation with the ATSB, the pilot said the grass, which was abnormally tall due to recent rainfall, had hidden the large birds from view. Had he been able to see them sooner he would have initiated a go-around before they took flight.
The pilot learned a useful lesson. He told the ATSB that even if you are familiar with an airstrip (as he was), you should consider conducting a precautionary pass over the runway to scare animals away from the area.