Bird use, bird hazard risk assessment, and

Elements of Risk

To construct the Safety-Risk Framework, it is necessary to understand the steps needed to build the framework. These are the elements of risk and are as follows:

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  Identify and categorize areas of exposure by examining aircraft flight paths, and the differing degrees of risk associated with different phases of flight (exposure and vulnerability);
  

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  Identify and categorize the various bird species that could strike aircraft with regard to the potential severity of impact (i.e. bird weight and behaviour);
  

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  Identify land-use as it affects nesting, feeding, night roosting, and daily and seasonal flight patterns of hazardous species of birds identified in the previous step. The degree of risk associated with different land-uses can then be determined and applied to the areas associated with the various aircraft operations (probability of loss due to birds attracted by particular land uses).
  

Aircraft Operations

Determining the flight paths of aircraft is a first and necessary step to discern categories of high- and low-risk land use near airports. Aircraft operate to, from, and in the vicinity of an airport with a high degree of predictability, enabling flight paths to be projected and mapped onto the lands around the airport. It is assumed that all runways at the new airport will be serviced by precision approach aids. It is also assumed that aircraft using the Pickering Airport will be transport-category aircraft powered by turbine engines, either jet or turbo-prop.

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  take off (take-off roll to 400 ft AGL)
  
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  initial climb (400 ft AGL to 3,000 ft AGL)
  
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  enroute climb (3,000 ft AGL to 10,000 ft)
  
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  descent (10,000 ft to 3,000 ft AGL)
  
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  approach (3,000 ft AGL to 400 ft AGL)
  
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  landing (400 ft AGL to touchdown);
  
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  the missed approach (50 ft to 3,000 ft AGL)
  

The airport runways are the references from which the flight paths are mapped. The subsequent projections depict the lateral and vertical zones in which, predictably, aircraft operate, and which, therefore, are the “potential” hazard zones for bird strikes.

1. 
   Take off and initial climb. The highest risk from a bird strike may occur during the take off and could result in loss of aircraft control and collision with terrain. The aircraft is low to the ground; it is often operating at or near the performance limits of the aircraft; it has a large fuel load; and it is at a critical angle-of-attack. Crew activity is high and coordination is imperative. As the climb out progresses and aircraft altitude increases, the risk of loss of control and collision with terrain is reduced. However, the risk of serious damage to the airframe and engine as a result of a bird strike increases because of higher impact forces from increasing airspeeds. In summary, the maximum potential losses can be classed as Category A during the initial climb-out (from ground level to 1500 ft above ground level [agl]) and as Category B during the climb out above 1500 ft agl.
   

[The use of 1500 ft agl as the likely break-point between Category A and B risks is based on the following factors. A bird strike occurring above 1500 ft elevation should provide sufficient time for an average flight crew to deal with the emergency and prevent a collision with terrain. This is the altitude that marks the end of the initial climb and the point at which most transport aircraft select climb thrust. It is also the point at which aircraft commence acceleration and retraction of flaps. On approach, 1500 ft agl represents the altitude at which the aircraft is configured for landing (gear down, flaps selected), which makes the aircraft less capable of maneuvering to avoid/recover from bird impacts. Also, below 1500 ft, the loss of thrust on one or more engines leaves little or no performance margin to complete the landing.]

2. 
   Missed approach. The most severe risk of a bird strike event during this phase of flight is a loss of control and subsequent impact with the terrain. This would likely occur if the bird strike event took place while initiating the missed approach, when the aircraft is low to the ground, the aircraft is in a low energy state, and the flight crew is reconfiguring the aircraft. At this time a Category A event would be possible. However, because much of the initial climb in the missed approach would occur over the runway, the exposure to bird hazard risk is reduced as a result of the airport bird management procedures. [Because runways are operated reciprocally as departure and arrival runways, the Category A hazard zone resulting from a missed approach coincides with the area included in the Category A zone associated with departures from the reciprocal runway.] At other times, if a strike occurred during a missed approach, then the maximum effect would likely be a Category B event.
   

3. 
   Instrument approach and landing. The most severe risk of a bird strike event during the instrument approach is a category B loss. A Category A loss is remotely possible if the event occurs in close proximity to the ground (e.g., a go-around because of unrelated and pressing operational conditions⁵).
   

4. 
   Descent to approach. The most severe result of a bird strike event during the descent to the approach is probably a Category B loss.
   

5. 
   En-route climb. The most severe result of a bird strike event during the en-route climb phase is a category B loss.
   

The foregoing information is summarized below.

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  During takeoff and initial climb from ground level to approximately 1500 feet agl;
  
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  During a missed approach (or during a go-around) from ground level to approximately 1500 feet agl;
  

Category B (Major Loss)

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  All other operations during the descent to the approach, the approach, the initial climb and en route climb.
  

Category A or B damage would only result from bird strikes involving certain species under worst case circumstances. Therefore, the identification of bird species by category of risk is an important step in assessing the risks to aircraft operating near the airport.