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A-1
APPENDIX A
Risk Assessment Methodology
CONTENTS
How to Use This Methodology, A-2
Limitations, A-2
Risk Criteria, A-3
Section 1 Taxiway to Taxiway or Taxiway to Taxilane, A-5
Section 2 Taxiway to Object, A-5
Section 3 Taxilane to Taxilane, A-7
Section 4 Taxilane to Object, A-8
Section 5 Runway to Taxiway, Taxilane, or Object, A-8
Attachment--Risk Plots, A-13

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A-2
How to Use This Methodology Table A-2. Airplane Design Groups
(FAA, 1989).
This methodology is intended to serve as a screening tool
for analysis associated with requests for modification of stan- Group # Tail Height (ft) Wingspan (ft)
dards (MOS) related to airfield separations. In no case should I < 20 < 49
II 20 to < 30 49 to < 79
this methodology be used to justify changes to current FAA III 30 to < 45 79 to < 118
design standards for airfields. Conclusions drawn based on IV 45 to < 60 118 to < 171
V 60 to < 66 171 to < 214
this methodology shall be subject to further analysis and
VI 66 to < 80 214 to < 262
approval by the FAA before the non-standard separation is
adopted. Additional mitigating procedures and risk control
measures may be required to achieve an acceptable level of
Table A-2 presents a summary of tail height and wingspan
safety for operations in the airfield.
ranges for each ADG.
This appendix provides a step-by-step methodology to eval-
As mentioned earlier, the outcome of the analysis is the
uate the risk of aircraft collision associated with airfield sepa-
risk of collision. Both the FAA and the International Civil Avia-
rations in parallel segments. The methodology uses informa-
tion Organization (ICAO) have been using a collision risk value
tion on existing or planned conditions and provides estimates
of one in 10 million operations (1 × 10-7) as the acceptable level
of risk. The level of risk should be compared to acceptable
during the approach phase under instrument conditions. This
levels of risk recommended by the FAA.
is also the level criterion suggested when applying this method-
Different procedures are used depending on the type of ology.
analysis desired, as explained in ensuing sections. The method-
ology is divided into five basic sections, and each section pres- Limitations
ents the procedure to assess the risk for a specific scenario.
The outcome of the analysis is the risk of collision between This methodology should be used carefully, and the user
two aircraft or between an aircraft and an object, depending on must be aware of its limitations. This methodology can be
the type of analysis required. To determine the appropriate sec- applied to estimate the risk of collision between two aircraft
tion containing the methodology and step-by-step procedure or an aircraft and an object only on straight parallel segments
for the desired type of analysis, the two types of structures of taxiways and taxilanes. Also, because the taxiway deviation
must be selected from Table A-1. For example, to analyze the models used in this study were developed from lateral devia-
separation between a taxiway and an object, the user should tion data collected on taxiways with centerline lights, the
use the procedure described in Section 2 and the risk plots conspicuity of the taxiway/taxilane centerline is an added risk
presented in Figures AA-8 to AA-14 presented in the attach- mitigation measure that should be used when justifying an
ment to Appendix A. MOS request for separations that do not include runways.
When describing the procedure, some acronyms are used to Although lateral deviation data in taxiing operations used
characterize specific parameters. Definitions of these acronyms to develop the risk plots were measured only for the B-747
can be found within the section in which they appear. When an aircraft, it is assumed that smaller aircraft have lateral devia-
equation is included in the procedure, a number located in tion distributions that have smaller ranges. Thus, the model
parenthesis to the right of it is used to reference the equation in applied can be considered conservative when applied to smaller
the text. aircraft.
Many of the risk plots presented in this methodology should The FAA/ICAO Collision Risk Model (CRM) during missed
be used for specific Aircraft Design Groups (ADGs) as defined approach was developed based on data for two- and three-
in FAA Advisory Circular (AC) 150/5300-13 (FAA, 1989). engine jet airplanes. The veer-off models developed under this
Table A-1. Procedure selection.
Taxiway Taxilane Runway
Taxiway Section 1 Section 1 Section 5
(Figures AA-1 to (Figures AA-1 to (Figures AA-29 to
AA-7) AA-7) AA-54)
Taxilane Section 1 Section 3 Section 5
(Figures AA-1 to (Figures AA-15 to (Figures AA-29 to
AA-7) AA-21) AA-54)
Object Section 2 Section 4 Section 5
(Figures AA-8 to (Figures AA-22 to (Figures AA-29 to
AA-14) AA-28) AA-54)

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A-3
ACRP study are based on data from veer-off accident/incident ing severity, and at the same time, likelihood should not be
reports taken from several countries and for aircraft with max- considered when determining severity.
imum takeoff weight (MTOW) larger than 5,600 lb. Definitions for each level of severity and consequence are
The collision risk during the approach phase of landing is presented in Tables A-3 and A-4.
modeled for missed approach during instrument approaches Two cases can serve as examples: (1) risk of collision between
under Cat I and II. This is assumed to be the highest risk con- an aircraft landing and an aircraft located in a parallel taxiway
dition, and the phase when the pilot is under visual condi- and (2) risk of wingtip collision between aircraft taxiing in
tions is not modeled in the risk curves presented. parallel taxiways. The first step is to determine the worst cred-
CRM risk is estimated for an aircraft located on the cen- ible consequence for each of these events. The worst credible
terline of a parallel taxiway. The taxiing aircraft is of the same consequence for runway veer-offs in most cases is hull loss and
ADG as the approaching aircraft, and the maximum tail height multiple fatalities, which is classified as catastrophic. Accord-
for the ADG is taken to characterize the obstacle located in the ing to the FAA risk matrix, such a condition is acceptable only
taxiway. The same plots may be used to assess risks associ- if it occurs less than once every 100 years or less than once in
ated with other types of obstacles at a certain distance from the 25,000,000 departures.
runway centerline; however, such obstacles must be lower For the second case, based on historical data of accidents
than the maximum tail height of the ADG used to develop the and incidents, the worst credible consequence may be classi-
charts. fied as major. In this case, the risk is acceptable if it is expected
to occur about once every year or every 2.5 million departures
Risk Criteria (4 × 10-7), whichever occurs sooner.
The suggested risk criteria to use with this methodology are The ICAO Obstacle Clearance Panel (OCP) has set the
those used by the FAA and represented by the risk matrix shown acceptable risk of collision during the approach phase at a
in Figure A-1 (FAA, 2010). A risk classification (high, medium, value of one in 10 million operations (1 × 10-7). Since this is
or low) is provided based on the combination of severity and the risk level used to establish most of the airfield design stan-
likelihood. dards defined by the FAA, and this methodology will serve as a
Severity is the measure of how bad the results of an event screening tool, this criterion is used in this screening method-
are predicted to be and is defined as the worst credible conse- ology. However, the risk classification based on the risk matrix
quence that may take place for risk associated with a given defined by the FAA must be highlighted when submitting
hazard. Likelihood should be considered only after determin- MOS for FAA approval (FAA, 2010).
Figure A-1. FAA risk matrix (FAA, 2010).

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A-4
Table A-3. FAA likelihood levels (FAA, 2010).
ATC Operational
General Airport Specific
Per Facility NAS-wide
Probability of Expected to occur Expected to occur Expected to occur
Frequent occurrence per more than once per more than once per every 12 days
A operation is equal week or every week
to or greater than 2,500 departures
1×10-3 (4×10-4),
whichever occurs
sooner
Probability of Expected to occur Expected to occur Expected to occur
occurrence per about once every about once every several times per
Probable
operation is less month or 250,000 month month
B
than 1×10-3, but departures (4×10-6),
equal to or greater whichever occurs
than 1×10-5 sooner
Probability of Expected to occur Expected to occur Expected to occur
occurrence per about once every about once every about once every
Remote
operation is less year or 2.5 million 110 years few months
C
than 1×10-5 but departures (4×10-7),
equal to or greater whichever occurs
than 1×10-7 sooner
Probability of Expected to occur Expected to occur Expected to occur
Extremely
occurrence per once every 10100 about once every about once every
Remote
operation is less years or 25 million 10100 years 3 years
D
than 1×10-7 but departures (4×10-8),
equal to or greater whichever occurs
than 1×10-9 sooner
Probability of Expected to occur Expected to occur Expected to occur
Improbable
Extremely
occurrence per less than once less than once less than once
operation is less every 100 years every 100 years every 30 years
E
than 1×10-9
Note: Occurrence is defined per movement.
Table A-4. FAA severity definitions (FAA, 2010).
Hazard Severity Classification
Minimal Minor Major Hazardous Catastrophic
5 4 3 2 1
No damage to - Minimal damage - Major damage to - Severe damage to - Complete loss of
aircraft but to aircraft; aircraft and/or aircraft and/or aircraft and/or
minimal injury or - Minor injury to minor injury to serious injury to facilities or fatal
discomfort of little passengers; passenger(s)/ passenger(s)/ injury in
consequence to - Minimal worker(s); worker(s); passenger(s)/
passenger(s) or unplanned airport - Major unplanned - Complete worker(s);
workers operations disruption to unplanned airport - Complete
limitations (i.e. airport closure; unplanned airport
taxiway closure); operations; - Major unplanned closure and
- Minor incident - Serious incident; operations destruction of
involving the use - Deduction on the limitations (i.e. critical facilities;
of airport airport's ability to runway closure); - Airport facilities
emergency deal with adverse - Major airport and equipment
procedures conditions damage to destroyed
equipment and
facilities

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A-5
Figure A-2. Example of taxiway/taxiway separation analysis for specific aircraft.
Section 1--Taxiway to Taxiway or WS1 is the wingspan for the first aircraft, and
Taxiway to Taxilane WS2 is the wingspan for the second aircraft.
Procedure to Estimate Risk of Collision c. Using Figure AA-7, enter the wingtip separation and
estimate the risk.
1. Identify the taxiways and the centerline separation to be 5. Using the risk level estimated, compare to 1 × 10-7, the
evaluated. upper probability for risk of major consequences accord-
2. Identify the ADG for analysis or the aircraft with the largest ing to the risk matrix recommended by the FAA.
wingspan that will be using each taxiway. It is possible
that each taxiway is assigned to a different ADG or specific
aircraft. Example 1--Taxiway/Taxiway Separation
3. If the assessment is for a specific ADG, the simplified col-
lision risk plots can be used based only on the taxiway cen- An airport is planning to build a new taxiway to accommo-
terline separation (Figures AA-1 to AA-6 in the attachment date larger capacity. The airport handles aircraft up to ADG V;
to this appendix). however, the space available is enough for a taxiway/taxiway
4. If the risk assessment involves specific aircraft or two dif- centerline separation of only 233 ft, as shown in Figure A-3.
ferent types of aircraft, the wingtip separation chart in Fig- The standard separation for ADG V is 267 ft, and an MOS was
ure AA-7 should be used, and in this case, the following deemed necessary to demonstrate that the available separa-
steps will be required: tion is safe.
a. Place both aircraft at the centerlines of the parallel taxi- For taxiway/taxiway separation involving ADG V, Figure
ways (see Figure A-2). AA-5 is used. Entering the separation of 233 ft, the risk of colli-
b. Calculate the wingtip clearance for this situation using sion when two ADG V aircraft are taxiing is approximately 2.3
Equation 1: E-08(seeFigureA-4),oronecollisionin 43,500,000 movements.
The risk is lower than 1.0E-07 and therefore it is acceptable.
WD = CS - (WS1 + WS 2 ) 2 (1)
where Section 2--Taxiway to Object
WD is the distance between wingtips of the two aircraft
Procedure to Estimate Risk of Collision
when both are positioned at the centerline of the taxiways,
CS is the centerline separation between the parallel 1. Identify the taxiway and the object separation to be
taxiways, evaluated.
Figure A-3. Example of analysis for taxiway/taxiway separation.

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A-6
1.E-05
ADG V Standard = 267 ft
Risk of Collision per Operation
1.E-06
1.E-07
2.3E-08
1.E-08
1.E-09
226 228 230 232 234 236
Taxiway/Taxiway Centerline to Centerline Separation (ft)
Figure A-4. Example of analysis of taxiway/taxiway separation (ADG V).
2. Identify the ADG for analysis or the aircraft with the largest 5. Compare the risk level estimated to 1 × 10-7, the highest
wingspan that will be using the taxiway. acceptable probability for risk of major consequences
3. If the assessment is for a specific ADG, the simplified colli- according to the risk matrix recommended by the FAA.
sion risk plots can be used based only on the centerline to
object separation (Figures AA-8 to AA-13).
4. If the risk assessment involves a specific aircraft, the wingtip Example 2--Taxiway/Object Separation
separation plot in Figure AA-14 should be used, and, in this An airport is planning to use an existing taxiway for ADG
case, the following steps will be required: III aircraft; however, it currently is used by ADG II aircraft,
a. Placetheaircraftatthetaxiwaycenterline(seeFigure A-5). and the separation between the taxiway and an exist-
b. Calculate the wingtip clearance for this situation: ing service road is only 72 ft. The scenario is presented in
WD = CS - WS 2 (2) Figure A-6. The airport does not have space to move the
service road because it is limited by the airport peri-
where meter fence. The standard separation for ADG III is 81 ft,
and an MOS is necessary to evaluate whether the separation
WD is the distance between the wingtip and the object when
is safe.
the aircraft is positioned at the centerline of the taxiway,
For taxiway/object separation involving ADG III, Figure
CS is the separation between the taxiway centerline and the
AA-10 is used. Entering the separation of 72 ft, the risk of col-
object, and
lision when an ADG III aircraft is taxiing is approximately
WS is the aircraft wingspan.
1.0E-06 (see Figure A-7), or one collision in 1,000,000 move-
c. Using Figure AA-14, enter the wingtip separation and ments. The risk is not acceptable based on the criterion of
calculate the collision risk. 1.0E-07; however, it may be possible to evaluate mitigation
Figure A-5. Example of taxiway/object separation analysis for specific aircraft.

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A-7
Figure A-6. Example of analysis for taxiway/object separation.
measures (e.g., restricting the wingspan of taxiing aircraft, 3. If the assessment is for a specific ADG, the simplified col-
using centerline lights) or to evaluate the expected number of lision risk plots can be used based only on the taxilane
years for one collision event based on the volume of operations centerline separations (Figures AA-15 to AA-20).
in the taxiway. 4. If the risk assessment involves specific aircraft or two dif-
For smaller airports with lower volumes of traffic, an acci- ferent types of aircraft, the wingtip separation plot in Fig-
dent may be expected to occur less than once every 100 years, ure AA-21 should be used, and, in this case, the following
and this condition is classified as extremely improbable. In steps will be required:
this case, the risk may be considered acceptable according to a. Place both aircraft at the centerlines of the parallel tax-
the criteria suggested by the FAA. ilanes (see Figure A-8).
b. Calculate the wingtip clearance for this situation:
Section 3--Taxilane to Taxilane WD = CS - (WS1 + WS 2 ) 2 (3)
Procedure to Estimate Risk of Collision where
1. Identify the taxilanes and the centerline separation to be WD is the distance between wingtips of the two aircraft
evaluated. when both are positioned at the centerline of the taxilanes,
2. Identify the ADG for analysis or the types of aircraft that CS is the centerline separation between the parallel taxilanes,
will be using each taxilane. It is possible that each taxilane WS1 is the wingspan for the first aircraft, and
is assigned to a different ADG or specific aircraft. WS2 is the wingspan for the second aircraft.
1.E-05
ADG III Standard = 93 ft
Risk of Collision per Operation
1.E-06
1.E-07
1.E-08
1.E-09
1.E-10
68 70 72 74 76 78 80 82 84 86
Taxiway Centerline to Object Separation (ft)
Figure A-7. Example of analysis for taxiway/object separation (ADG III).

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A-8
Figure A-8. Example of taxilane/taxilane separation analysis for specific aircraft.
c. Using Figure AA-21, enter the wingtip separation and c. Using Figure AA-28, enter the wingtip separation and
calculate the risk. calculate the collision risk.
5. Using the risk level estimated, compare to 1 × 10-7, the 5. Using the risk level estimated, compare to 1 × 10-7, the
upper probability for risk of major consequences accord- upper probability for risk of major consequences accord-
ing to the risk matrix used by the FAA. ing to the risk matrix used by the FAA.
Section 4--Taxilane to Object Section 5--Runway to Taxiway,
Taxilane, or Object
Procedure to Estimate Risk of Collision
The runway/taxiway, runway/taxilane, or runway/object
1. Identify the taxilane and the object separation to be
separation has two scenarios: takeoff and landing. For land-
evaluated.
ing operations, the analysis is divided into two parts: air-
2. Identify the ADG for analysis or the aircraft with the largest
borne (approach) phase and ground (landing rollout) phase.
wingspan that will be using the taxilane.
For takeoff operations, the analysis considers only the
3. If the assessment is for a specific ADG, the simplified colli-
ground (takeoff roll) phase. In most cases, the runways are
sion risk plots can be used based only on the taxilane center-
used for both landing and takeoff operations, and the analy-
line to object separation (Figures AA-22 to AA-27).
4. If the risk assessment involves a specific aircraft, the wingtip sis for takeoff operations will not be necessary because the
separation plot in Figure AA-28 should be used, and, in risk of major lateral deviations during takeoff is lower than
this case, the following steps will be required: the risk during landing.
a. Place theaircraftatthetaxiwaycenterline(seeFigure A-9). The airborne collision risk during the approach for land-
b. Calculate the wingtip clearance for this situation: ing is characterized using the FAA/ICAO CRM. A series of
plots, one for each ADG, was developed to facilitate the use
WD = CS - WS 2 (4) of this methodology.
For the landing ground roll phase, risk plots were derived
where: based on a two-part model: frequency and location. Each
WD is the distance between the wingtip and the object when plot integrates historical runway veer-off accident/incident
the aircraft is positioned at the centerline of the taxilane, rates with veer-off location models to simplify the use of this
CS is the separation between the taxilane centerline and the methodology. Given that the aircraft veered off the runway,
object, the chance that the aircraft deviates more than a certain dis-
WS is the aircraft wingspan. tance from the runway edge is given by the location model.
Figure A-9. Example of taxiway/object separation analysis for specific aircraft.

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A-9
Table A-5. Average probability of The basis for the analysis is the FAA/ICAO CRM and ranges
occurrence by type of incident of -300, 0, 750, 1,500, 3,000, and 4,500 ft along the runway,
(U.S. data--1982 to 2009). which were evaluated to develop the curves presented in Fig-
ures AA-29 to AA-34. The range corresponding to the nega-
Type of Incident Probability
tive number represents a distance before the runway end for
Landing veer-off
(LDVO)
1 per 837,002 landings an approaching aircraft, and positive values are for distances
Takeoff veer-off
after the runway arrival end.
1 per 3,860,665 takeoffs The plots provide the highest probability of collision dur-
(TOVO)
ing missed approaches under instrument (Cat I or Cat II) con-
ditions. Although the CRM was developed in the 1970s and
The combination of the frequency and location models will the FAA has made modifications to improve these models, the
provide the probability that an aircraft will veer off the run- original CRM will serve as a screening tool to lead to further
way and deviate more than a given distance from the run- analysis by the FAA if the risk estimated is within a feasible
way edge. range for additional analysis. The runs were made with obsta-
Table A-5 provides the average incident rates for landing cles located at various distances from the runway centerline
and takeoff veer-offs. and along the runway length.
It is also possible to use an alternative approach that may be The following steps apply to the estimation of risk during
more accurate but will require intensive calculations and the landings:
need to use an electronic spreadsheet or computer software.
Details of the second approach can be found in the attachment 1. Calculate the risk during the airborne phase.
to this appendix. 2. Calculate the risk during the landing rollout phase.
3. Calculate the total risk during landing.
Subsection 5.1--Landing
Each of these steps is explained below.
For landing, it is necessary to estimate two types of risk: the
risk of collision during the approach phase before the touch-
5.1.1--Risk in Airborne Phase (Landing)
down and the risk of collision during the ground phase in case
the aircraft veers off the runway during the landing rollout. For this phase, the obstacle to the approaching aircraft is
These two risks may be combined to provide the total risk. The assumed to be another aircraft located in any segment of the
veer-off risk is estimated for every landing operation, whereas parallel taxiway. This is a conservative assumption because,
the airborne risk is computed only for missed approaches in most cases, the obstacle will be an aircraft moving on a par-
under instrument conditions, which are assumed to be the allel taxiway and the obstacle will have a small length com-
worst scenario. pared to the total runway length.
For the airborne phase, because this analysis is intended to Figure A-10 presents a typical scenario for this type of analy-
evaluate the risk of collision between the approaching aircraft sis. The plots are based only on the horizontal separation
and an aircraft located in a parallel taxiway or an object, the between the runway and taxiway centerlines, and the vertical
analysis will focus only on the area within the immediate vicin- separation is already considered in the plots presented in this
ity of the runway threshold and touchdown zone. section.
Figure A-10. Example of runway/taxiway separation analysis.

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A-10
Procedure to Estimate Risk of Collision. The following 2. Calculate the frequency of landing veer-offs for the run-
presents the procedure to estimate risk of collision: way by applying the frequency model (see "Event Prob-
ability" and Table 7 in Chapter 4).
1. Identify the runway and the taxiway (or taxilane or object) 3. Calculate the probability that the aircraft veers off beyond
centerline separation to be evaluated. a given distance:
2. Identify the ADG for analysis based on the aircraft with the a. Obtain the wingtip clearance WD between the aircraft
largest wingspan that will be using both the runway and landing and the nearest obstacle, as shown in Figures
the taxiway or taxilane. A-11 and A-12, by placing the center of the aircraft land-
3. Select the plot for the specific ADG involved and estimate ing at the edge of the runway.
the risk based only on the runway centerline to taxiway b. Use WD and apply the location model (see Table 10)
centerline separation (see Figures AA-29 to AA-40). to calculate the probability of a lateral deviation
4. Using the risk level estimated, compare to 1 × 10-7, the beyond WD.
lowest probability for risk of severe consequences accord- 4. Multiply the frequency probability by the location proba-
ing to the risk matrix used by the FAA. bility and repeat Steps 2 and 3 for each historical landing
operation on the runway.
5.1.2--Risk in Ground Phase (Landing) 5. Calculate the average value for the probabilities estimated
with historical landing data for the runway.
There are two alternatives that may be used to estimate
the risk for the ground phase of landing, i.e., during the WD = CS - RW 2 - (WS1 + WS 2 ) 2 (5)
landing rollout. Alternative 1 is the default analysis and pro-
where
vides a simpler and direct estimate based upon generalized
inputs. Alternative 2 provides a more accurate estimate for WD is the wingtip distance,
specific cases but also requires a significant amount of data CS is the separation between the runway and the taxiway,
and computation. RW is the runway width,
WS1 is the wingspan for the aircraft taking off, and
Procedure to Estimate Risk of Collision. The following WS2 is the wingspan for the aircraft in the parallel taxiway.
are the steps to estimate risk for the landing rollout phase. For
Alternative 1 (Default): If the analysis is for a specific ADG, WD can be picked up
from Table A-6.
1. Figures AA-41 to AA-47 represent the risk curves that Another possibility is the evaluation of separation between
integrate both the frequency and location models for the the runway and an object. Figure A-12 shows an example using
specific case. a runway and a service road. In this case, the wingtip separa-
2. Characterize the separation between the runway center- tion is calculated using Equation 6:
line and the parallel taxiway, parallel taxilane, or object.
WD = CS - RW 2 - SW 2 - WS 2 (6)
3. Characterize the ADG involved in the analysis.
4. Select the correct plot for the ADG involved in the analysis. where
5. Enter the centerline separation to obtain the risk of collision
in the plot selected. WD is the wingtip separation,
CS is the separation between the runway and the service
For Alternative 2: road,
RW is the runway width,
1. Obtain 1 year of historical landing operational data and SW is the width of the service road, and
information on weather conditions for the runway. WS is the wingspan of the aircraft.
Figure A-11. Typical runway/taxiway scenario for runway veer-off incidents.

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A-11
Figure A-12. Typical runway/object scenario for runway veer-off incidents.
The frequency and location models for veer-off are presented 1. Figures AA-48 to AA-54 represent the risk curves that
in Tables 7 and 10. integrate both the frequency and location models for the
specific case.
2. Characterize the separation between the runway center-
Subsection 5.2--Takeoff line and the parallel taxiway, parallel taxilane, or object.
For takeoff, the risk is that an aircraft will veer off the run- 3. Characterize the ADG involved in the analysis.
way and strike an obstacle in the vicinity of the runway obsta- 4. Select the correct plot for the ADG involved in the analysis.
cle free zone (OFZ). In this case, the obstacle is assumed to be 5. Enter the centerline separation to obtain the risk of collision
an aircraft or another object (fixed or movable) that is closest in the plot selected.
to the runway centerline. This is a conservative assumption
because an aircraft may not be present in the parallel taxiway, For Alternative 2:
and the obstacle has a small length compared to the total
runway length. 1. Obtain 1 year of historical takeoff operational data and
Analysis for takeoff is only applicable to runways with depar- information on weather conditions for the runway.
ture operations only. This is because when the runway is used 2. Calculate the frequency of takeoff veer-off for the run-
for both landing and takeoff, the highest risk condition is for way by applying the frequency model (see "Event Prob-
landing. ability" and Table 7 in Chapter 4).
Similar to the case for landings, there are two alternatives 3. Calculate the probability that the aircraft veers off beyond
for estimating the risk of collision. Alternative 1 is the default a given distance:
analysis and is simple and direct, based upon generalized a. Obtain the wingtip clearance WD between the aircraft
inputs. Alternative 2 provides a more accurate estimate that taking off and the nearest obstacle, as shown in Figures
A-11 and A-12, by placing the center of the aircraft
takes into account specific operation conditions for the air-
landing at the edge of the runway.
port; however, it requires a significant amount of data and
b. Use WD and apply the location model (see Table 10)
computation.
to calculate the probability of a lateral deviation be-
Procedure to Estimate Risk of Collision. The following yond WD.
are the steps to estimate risk for the takeoff roll phase for 4. Multiply the frequency probability by the location proba-
Alternative 1 (Default): bility and repeat Steps 2 and 3 for each historical takeoff
operation on the runway.
5. Calculate the average value for the probabilities estimated
with historical takeoff data for the runway.
Table A-6. Wingtip separation
based on largest wingspan
in ADG. Example 3--Runway/Taxiway Separation
ADG RW (ft) WD (ft)
In this example, an ADG II airport wants to bring regu-
I 100 CS-99 lar flights of ERJ-170 aircraft. The runway is 150 ft wide
II 100 CS-129 and has a Cat I instrument landing system (ILS). The wing-
III 100 CS-168
IV 150 CS-246 span of an ERJ-170 is 85.3 ft, and it is classified in ADG III.
V 150 CS-289 The existing separation between the runway and the paral-
VI 200 CS-362 lel taxiway centerlines is 320 ft; however, the standard for

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A-30
1.0E-07
ADG III Approach Cat C
Standard = 400 ft
Risk of Collision per Operation
1.0E-08
1.0E-09
1.0E-10
1.0E-11
200 250 300 350 400 450 500
Runway/Taxiway Centerline Separation (ft)
Figure AA-34. Missed approach collision risk for ADG III Cat II.
1.0E-06
ADG IV Approach Cat D
Standard = 400 ft
1.0E-07
Risk of Collision per Operation
1.0E-08
1.0E-09
1.0E-10
1.0E-11
250 300 350 400 450 500 550 600 650 700 750 800
Runway/Taxiway Centerline Separation (ft)
Figure AA-35. Missed approach collision risk for ADG IV Cat I.

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A-31
1.0E-06
ADG IV Approach Cat D
Standard = 400 ft
Risk of Collision per Operation
1.0E-07
1.0E-08
1.0E-09
1.0E-10
1.0E-11
250 300 350 400 450 500 550 600 650 700 750 800
Runway/Taxiway Centerline Separation (ft)
Figure AA-36. Missed approach collision risk for ADG IV Cat II.
1.0E-06
ADG V Approach Cat D
Standard = 400-500 ft*
Risk of Collision per Operation
1.0E-07
1.0E-08
1.0E-09
1.0E-10
1.0E-11
450 300
500 350
550 400
600 650 700 750 800 850
Runway/Taxiway Centerline Separation (ft)
*For specific standard, please check Table 2-2 in FAA AC 150/5300-13.
Figure AA-37. Missed approach collision risk for ADG V Cat I.

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A-32
1.0E-05
ADG V Approach Cat D
Standard = 400-500 ft*
1.0E-06
Risk of Collision per Operation
1.0E-07
1.0E-08
1.0E-09
1.0E-10
1.0E-11
450 300 350
500 400
550 600 650 700 750 800 850
Runway/Taxiway Centerline Separation (ft)
*For specific standard, please check Table 2-2 in FAA AC 150/5300-13.
Figure AA-38. Missed approach collision risk for ADG V Cat II.
1.0E-06
ADG VI Approach Cat D
Standard = 500 ft
Risk of Collision per Operation
1.0E-07
1.0E-08
1.0E-09
1.0E-10
400 450 500 550 600 650 700 750 800 850 900
Runway/Taxiway Centerline Separation (ft)
Figure AA-39. Missed approach collision risk for ADG VI Cat I.

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A-33
1.0E-05
ADG VI Approach Cat D
Standard = 500-550 ft*
Risk of Collision per Operation
1.0E-06
1.0E-07
1.0E-08
1.0E-09
1.0E-10
400 450 500 550 600 650 700 750 800 850 900
Runway/Taxiway Centerline Separation (ft)
*For specific standard, please check Table 2-2 in FAA AC 150/5300-13.
Figure AA-40. Missed approach collision risk for ADG VI Cat II.
Section 5.1.2--Landing Veer-Off Collision Risk Plots (Ground Phase)
1.E-06
ADG I Approach Cat C
Standard = 300-400 ft
Risk of Crossing the Taxiway
1.E-07
1.E-08
1.E-09
100 200 300 400 500 600 700 800
Centerline Separation (ft)
Figure AA-41. Landing veer-off collision risk for ADG I.

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A-34
1.E-06
ADG II Approach Cat C
Standard = 300-400 ft
Risk of Crossing the Taxiway
1.E-07
1.E-08
1.E-09
150 250 350 450 550 650 750
Centerline Separation (ft)
Figure AA-42. Landing veer-off collision risk for ADG II.
1.E-06
ADG III Approach Cat C
Standard = 400 ft
Risk of Crossing the Taxiway
1.E-07
1.E-08
1.E-09
200 300 400 500 600 700 800
Centerline Separation (ft)
Figure AA-43. Landing veer-off collision risk for ADG III.

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A-35
1.E-06
ADG IV Approach Cat D
Standard = 400 ft
Risk of Crossing the Taxiway
1.E-07
1.E-08
1.E-09
250 350 450 550 650 750 850 950
Centerline Separation (ft)
Figure AA-44. Landing veer-off collision risk for ADG IV.
1.E-06
ADG V Approach Cat D
Standard = 400-500 ft*
Risk of Crossing the Taxiway
1.E-07
1.E-08
1.E-09
300 400 500 600 700 800 900 1000
Centerline Separation (ft)
*For specific standard, please check Table 2-2 in FAA AC 150/5300-13.
Figure AA-45. Landing veer-off collision risk for ADG V.

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A-36
1.E-06
ADG VI Approach Cat D
Standard = 500-550 ft*
Risk of Crossing the Taxiway
1.E-07
1.E-08
1.E-09
400 500 600 700 800 900 1000 1100
Centerline Separation (ft)
*For specific standard, please check Table 2-2 in FAA AC 150/5300-13.
Figure AA-46. Landing veer-off collision risk for ADG VI.
1.E-06
Note: The wingtip separation is
measured with the landing aircraft
centered at the edge of the runway
Risk of Crossing the Taxiway
1.E-07
1.E-08
1.E-09
1.E-10
0 200 400 600 800 1000
Wingtip Separation to Taxiway Centerline or Object (ft)
Figure AA-47. Landing veer-off collision risk based on wingtip
clearance--any ADG.

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A-37
Section 5.2--Takeoff Veer-Off Collision Risk Plots
1.E-06
ADG I Approach Cat C
Standard = 300-400 ft
Risk of Collision (Acc/Op)
1.E-07
1.E-08
1.E-09
100 200 300 400 500 600 700 800
Centerline Separation (ft)
Figure AA-48. Takeoff veer-off collision risk for ADG I.
1.E-06
ADG II Approach Cat C
Standard = 300-400 ft
Risk of Collision (Acc/Op)
1.E-07
1.E-08
1.E-09
150 250 350 450 550 650 750
Centerline Separation (ft)
Figure AA-49. Takeoff veer-off collision risk for ADG II.

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A-38
1.E-06
ADG III Approach Cat C
Standard = 400 ft
Risk of Collision (Acc/Op)
1.E-07
1.E-08
1.E-09
200 300 400 500 600 700 800
Centerline Separation (ft)
Figure AA-50. Takeoff veer-off collision risk for ADG III.
1.E-07
ADG IV Approach Cat D
Standard = 400 ft
Risk of Collision (Acc/Op)
1.E-08
1.E-09
1.E-10
250 350 450 550 650 750 850 950
Centerline Separation (ft)
Figure AA-51. Takeoff veer-off collision risk for ADG IV.

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A-39
1.E-07
ADG V Approach Cat D
Standard = 400-500 ft*
Risk of Collision (Acc/Op)
1.E-08
1.E-09
1.E-10
300 400 500 600 700 800 900 1000
Centerline Separation (ft)
Figure AA-52. Takeoff veer-off collision risk for ADG V.
1.E-07
ADG VI Approach Cat D
Standard = 500-550 ft*
Risk of Collision (Acc/Op)
1.E-08
1.E-09
1.E-10
400 500 600 700 800 900 1000 1100
Centerline Separation (ft)
Figure AA-53. Takeoff veer-off collision risk for ADG VI.

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A-40
1.E-07
Note: The wingtip separation is
measured with the landing aircraft
centered at the edge of the runway
Risk of Collision (Acc/Op)
1.E-08
1.E-09
1.E-10
100 200 300 400 500 600 700 800
Wingtip Separation (ft)
Figure AA-54. Takeoff veer-off collision risk based on wingtip
clearance--any ADG.