2. Availability of Exposure Data
The US FAA annually completes a survey of US operators, including hours of flight by operator type. Prior to 2006 IBAC was concerned that the gap between the total flying hours calculated by Robert Breiling was different from those of the FAA. However, over the last couple of years the gap has closed to the point that there is increased confidence in the survey results and IBAC has now concluded that the survey information is sufficiently accurate to provide a rea-sonable assessment of the differences between accident rates for each operator type.
The FAA survey is sent to 100% of general aviation and on-demand commercial operators of turbine aircraft in the US and follows up three times with operators that do not respond immedi-ately. Submissions are made annually by approximately 45% of the US turbine operator popu-lation. The US business aviation fleet consists of 65% of the world fleet and the distribution be-tween operator types is considered representative of the global fleet with the exception of the European fleet. The global distribution and an assessment of each region is as follows;
United States 65%
North America without the US 8% Distribution considered similar to the US
South America 7% Distribution considered similar to the US
Europe 11% Probable higher percent of on-demand commercial operations.
Rest of the World 9% Different rule structures but most would be similar to the US
FAA survey data was applied over a three year period to develop an average distribution by aircraft type (Jet, Turbo-Prop and Combined) and operator type (Commercial On-demand, Cor-porate and Owner-Operated). The data in Table C-1 was applied to the total business aviation hours to calculate the number of flying hours for each operational type.
3. Rate Calculation
Accident rates per operator type were calculated using accident data in the Safety Brief, along with exposure data as explained in S2 above. Tables were developed for both 100,000 flying hours and 100,000 departures.
4. Assumptions
IBAC recognizes that there is error built into the methodology, but given the lack of options the data is considered as accurate as anything available. The following assumptions that give rise to some error are:
The breakdown by operator types is derived from an FAA survey of US operators. An assump-tion is made that the remainder of the world will have an operator distribution similar to the US. Given that the US consists of approximately 65% of the global fleet, it is unlikely that the error due to this assumption will be very significant.
The FAA survey captured approximately 50% of the total global flying hours. It is assumed that the 50% is representative of the distribution for the complete population.
5. Sensitivity Analysis
As noted above, an assumption is made that the US distribution by operator type is representative of the global fleet distribution and yet it was also concluded that the European fleet distribution is likely different than that of the US. Given the potential that this may result in an unacceptable er-ror, a sensitivity analysis was completed to determine the impact of a higher percentage of the European fleet being operated as on-demand charters.
Two samples for European distribution were selected to test the impact.
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