Risk of a Fatal Large
Jet Transport Bird Strike
The following is a risk assessment that will show that from 1997-2006 there is about a 25% probability of a bird strike event in the U.S. or Canada causing a fatal large jet transport accident. For the ten year period beginning with the current year, a new rate can be computed using appropriate numbers for the total number of historical flights since 1959, and different numbers for the estimated number of flights for future years, updated load factors, updated bird strike cost estimates, and updated information for hull losses and fatal events (if appropriate).
Bird strikes to aircraft have been a concern since the first recorded fatal bird strike in 1912. More recently, bird strikes have led to fatal accidents for large military aircraft in both 1995 and 1996 and to a commercial airliner in 1988. Increasing North American populations of birds such as geese and ducks have led to a significant increase in the threat to aircraft, especially in areas on or near airports. The probability of a fatal bird strike accident can be estimated based on the past bird strike record. Specifically, the following analysis will estimate the probability of a fatal accident involving a bird strike to a large jet transport aircraft occurring in the next ten years in the U.S. or Canada.
Risk Assessment Basics
Risk is defined as the combination of a specific hazard and the likelihood of that hazard occurring. The specific hazards dealt with here are bird strike events that result in in the following combination of effects:
- Both fatalities and aircraft hull loss,
- Aircraft hull loss only, and
- Other economic losses ($26 million wildlife losses 1993-1995 from FAA reports.
The likelihood of these three hazards can be roughly estimated from the following information:
- From 1959 to 1997, there have been five hull losses (one fatal) involving a large civil jet transport aircraft.
- Total number jet transport flights from 1959 to 1996(about 300 million)
- Estimated U.S. and Canadian large commercial jet transport flights 1997-2006, 80 million
- average load factor of 54% (60% for airliners, 0% for cargo jet transports, 10% cargo flights)
- Average passenger capacity of 130 for these jets flights.
- A 50% probability that a passenger dies in a fatal bird strike event.
- The cost of average jet transport is $30 million (in 1997 dollars.
Assuming that the historical world hull loss rate is roughly current underlying rate in the U.S. and Canada,
P(Hull Loss From a Bird Strike Event) = 5/300M = 1.67 x 10-8
P(Fatal | Hull Loss) = 0.2
P(Fatal Hull Loss Event) = 3.3 x 10-9
P(Fatal Hull Loss Event in U.S. or Canada) = (3.3 x 10-9)(8 x 10+6) = 0.027/year
Assuming a binomial distribution of events, this would imply that over the next decade,
P(Zero Fatal Hull Losses) = 0.763
P(One Fatal Hull Loss) = 0.209
P(Two Fatal Hull Losses) = 0.026
P(Three Fatal Hull Losses) = 0.001
Estimated Fatal Hull Losses = 0.209 + 2(0.026) + 3(0.001) = 0.263
Note: This last figure means that in the next 10 years there is about a 25% chance of a fatal bird strike accident involving a large jet transport in the U.S. or Canada
Estimated Fatalities = 9.2 = (0.263)(130)(0.54)(0.5)
Estimated Non-Fatal Hull Losses = 1.05 = 4(0.263)
|Lives Lost||9.2||23 million*|
|Aircraft Losses||1.3||39 million|
|Other Losses||-||87 million**|
* Assume $2.5 million in liability claims per life lost
** Based on 1993-1995 FAA figures for wildlife losses, may represent only 1/20th of total economic losses (cost data from "Wildlife Strikes to Aircraft in the U.S.: 1993-1995")
http://airsafe.com/bird/birdrisk.htm -- Revised 29 May 2008