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39
CHAPTER 4
Practical Application of Models
Upon developing the risk models, it is necessary to inte- 6. Determine the weighted frequency distribution for all
grate them to allow risk assessment of RSAs under specific types of incidents together.
conditions. A practical application of such models for exam- 7. Repeat the analysis for the remaining runway ends of the
ining a specific RSA will involve estimating the risk that an airport.
aircraft operating under specific airport conditions will chal- 8. Account for the risk exposure and estimate the probabil-
lenge the existing RSA and stop beyond the available RSA ity, in terms of accidents per year, for each type of incident
limits or crash into existing obstacles. and for each RSA of the airport.
This chapter includes a step-by-step procedure to evaluate 9. Classify the RSA according to the percentage of high-risk
an RSA using the models and the approach developed in this operations.
study. The example presented is for a hypothetical Runway
07/25, but actual NOD for an existing airport was collected
Step 1--RSA Details
from 2002 to 2004 and is used to illustrate the practical
application of the approach developed. The procedure repre- The RSA to be evaluated should be characterized by type of
sented in Figure 34 will allow assessing the probability that an terrain, dimensions, and type, size, and location of obstacles.
incident will occur during the aircraft operation and that as a The analysis is for the approach end of Runway 25 and is a
result, the consequences are likely to be severe. The initial simple example because the obstacles that can cause severe
process will involve the following steps: consequences are well defined; the RSA is rectangular and
The initial process will involve the following steps: symmetric, and it is surrounded by a body of water, as de-
picted in Figure 35.
1. Select the specific RSA to analyze and gather information
to include dimensions, type of terrain, and existing obsta-
Step 2--Collect Representative
cles adjacent to the RSA.
Traffic Sample
2. Collect (or estimate) a representative traffic sample for the
three crash scenarios (LDOR, LDUS, and TOOR) chal- This step will involve gathering normal operations data for
lenging the RSA being evaluated. the airport. A second alternative for this step is to estimate the
3. Divide the RSA into sections comprising specific crash expected operations based on the planned flight schedule for
scenarios. Each scenario should include the distance from the facility. When using historical data, two possible sources
the threshold and two lateral distances relative to the ex- are: the Aviation System Performance Metrics (ASPM) data,
tended runway axis. which identify the takeoff and landing runways in hourly seg-
4. Using the frequency models and location models, estimate ments, the runway, and direction for each flight; and the
for every operation the probability for each crash scenario Enhanced Traffic Management System Counts (ETMSC),
and type of operation. Based on these data, develop the which provides information on traffic counts by airport or by
frequency distribution for each crash scenario and for city pair for various data groupings. These same sources were
each type of incident (LDOR, LDUS, and TOOR). used to obtain NOD for this study. The sample flight data are
5. For each type of operation, determine the percentage of oc- for operations that may challenge the RSA being evaluated in
currences having a risk higher than a selected level or TLS. the event of an aircraft overrun or undershoot.
