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39 Only aircraft manufacturers can use actual aircraft data dur- ments and planning efforts. The approach can be similar to ing operations to estimate actual aircraft performance. the one presented in this study--using evidence of aircraft ac- The models and the approach were developed using actual cidents in the vicinities of airports to develop risk models data from accident and incident reports, and the models are based on causal and contributing factors to aircraft accidents. simply based on evidence gathered from that type of informa- The study should address the risk of accidents in areas within tion. For example, to estimate the runway distance required, a a 10-mile radius of the runway. basic distance for the type of aircraft and model was used and The methodology should consider local factors, historical corrected for temperature, elevation, wind, and surface charac- operation conditions for the airport, and the type of land use for teristics. Wind corrections are considered to be average adjust- specific regions near the airport runways. The recommended ments, and surface conditions are estimated based on weather study would improve the capability of land use committees and conditions only, rather than relying on actual runway friction. airport operators to assess third-party risk associated with air- It was not possible to incorporate the touchdown location craft accidents in the vicinity of airports. or the approach speed during landing. These are important The approach should be rational, non-prescriptive, and factors that may lead to accident, but there are no means to provide a quantitative assessment of third-party risk associ- account for these factors, except for assuming average values ated with aircraft operations at a specific airport. The study with a certain probability distribution that will lead to some should associate aircraft operations with existing runway and level of model uncertainty. environmental conditions, and aircraft type for a specific air- Additional simplifications were necessary to address the in- port. Thus, the results of such a study would help decision teraction of incidents with existing obstacles. In many cases, makers to evaluate alternatives and associated safety benefits. the pilot is able to have some directional control of the aircraft and avoid some obstacles. The approach simply assumes that Development of Risk Tool for Airspace the aircraft location is a random process and the deviation Analysis in Vicinity of Runways from the runway centerline follows a normal probability dis- The RSA analysis methodology and software presented tribution and that, during overruns and undershoots, the air- in this study can only address the ground roll phase of op- craft follows a path that is parallel to the runway centerline. eration; however, aircraft have both lateral and vertical de- One major limitation to obtain more accurate models and viations from their nominal flight path during landing and estimates is the difficulty in accounting for human factors. takeoff operations. Some type of human error was present in the majority of the Currently, the aviation industry still relies on the Collision events reported, and this factor is reflected as a component of Risk Model (CRM) developed in the 1960s with very limited the model error. data to evaluate risk during instrument approaches during the Also, obstacle categories were defined according to the max- non-visual segment and missed approach phases. The CRM imum speed to avoid an accident with substantial damage to has many limitations and does not cover all phases of the flight the aircraft and possibly injuries to its occupants. The classifi- and types of approach. Only data for precision approach Cat- cation was defined in this project using engineering judgment egories I and II can be evaluated using the existing model. and assuming that consequences depend only on the collision There is a need to have an updated CRM that can be used to speed and the area of the aircraft that has collided with the ob- prioritize risk mitigation actions associated with obstacles in stacle. Again, only engineering judgment was used to classify the vicinity of the runway. different types of obstacles according to the categories. Currently, the FAA is developing a tool called Airspace Sim- ulation and Analysis Tool (ASAT) that has comprehensive Recommendations for Future Work capabilities and accounts for aircraft performance, NAVAIDs, environmental conditions, terrain, wake turbulence, and hu- Extend Analysis for Non-RSA Areas man factors. However, the tool is not available to other air- Even with its limitations, the approach presented in this port stakeholders. report is quite robust for the analysis of RSA. It takes into The improved tool should have the capability to assess risk consideration many local factors and specific conditions to associated with fixed or movable obstacles when they are very provide estimates of risk. close to the runway. It should address all types of approach Still, the analysis presented can only cover the areas in the (visual, non-precision, precision, and possibly global position- immediate vicinity of the runway. The development of a risk- ing system [GPS] approach technology). Many airports would based methodology to evaluate land use compatibility and benefit from such a tool for safety management associated with third-party risk could be very helpful to support State require- the presence of obstacles.