Wildlife risk assessment

“The risk assessment protocol provides airport managers with a tool that enables them to objectively evaluate the risk at their airport, to target offen scarce resources to those areas where the will provide the greatest benefit, and to illustrate due diligence in that, despite their best efforts, a serious incident does occur.”

John Allan

The risk (R) of a birdstrike is defined as how likely it occurs (P) multiplied with the severity or the harm (S) it causes. This is expressed as R = P x S.

Fundamentally, we have to know the species ID of the birds involved in birdstrikes before we can use the ‘Birdstrike Risk Assessment’ procedure as described below. According to this procedure, the severity is defined as the proportion of the total strikes of the specific bird causing damage to the aircraft involved. And this proportion is strictly influenced by the body weight of the bird.

The severity of a Kestrel is 2% or 0,02 if two out of one hundred Kestrels have caused damages to the aircraft. However, a number of one hundred kestrels is too small a sample to calculate a valid mean value for severity. When plotting all damaging strikes against the birds weight known in UK an overall relation of y = 0.014x has been calculated, i.e. if a bird species has a weight of x gram you can multiply the body weight by 0.014 to give a reasonable value of the bird’s severity (Allan, 2006*). In fact, very few bird species have been involved in birdstrikes for a sufficient number of times to give a more accurate species specific value of the severity. Therefore, the value of 0.014 is useful when calculating the severity for every bird species. The body weight of birds can easily be found on the web using a search engine.

The probability of birdstrikes is in fact the frequency of strikes experienced at the location over a given period of time. According to this risk assessment procedure, you have to use a running annual mean of strikes during the last 5 year period.

When all the bird species involved in strikes are listed with their calculated severity and frequency for the location, a 5×5 matrix can be produced.

This matrix is widely used in many other aspects, however, the border values of severity and frequency are proposed by Allan (2006)

When you have placed the bird species in the boxes of the matrix correctly, you have to consider the associated consequences if the species are placed in the red or yellow boxes.

The AscendXYZ Wildlife solution offers a calculation as where to place your birdstrike species in the matrix. You just have to input the number of strikes of the species from the last five years. Further, the Wildlife solution offers a list of possible mitigating actions to imply if this is needed, according to your risk assessment.

*): Allan, John, A Heuristic Risk Assessment Technique for Birdstrike Management at Airports. Risk Analysis, Vol. 26, No. 3, pp. 723-729, June 2006