runway incursion severity categorization (risc) model

Presented to: International Civil Aviation Organization

By: LaGretta Bowser

Date: September 2005

Federal AviationAdministration

Runway Incursion Severity Categorization (RISC)Model

2Federal AviationAdministration

Runway Incursion Severity Categorization (RISC) Model September 2005

Current FAA Runway Incursion Severity CategoriesOperational dimensions affecting runway incursion severity:

EnvironmentalConditions

Speed ofAircraft and/or

Vehicle

Proximity ofAircraft and/or

Vehicle

Increasing Severity

Category D

Little or no chance of

collision, but meets

the definition of a

runway incursion.

AvailableReaction

Time

Evasive orCorrective

Action

Category C

Separation decreases, but there is ample time and distance to avoid a potential collision.

Category B

Separation decreases and there is a significant potential for collision.

Category A

Separation decreases

and participants take

extreme action to

narrowly avoid a

collision, or the event

results in a collision.



Proposed Severity Categories• “A” = A very serious incident in which a collision

was narrowly avoided.

• “B” = An incident in which separation decreases and there is significant potential for collision, which may result in a time-critical corrective/evasive response to avoid a collision.

• “C” = A minor incident characterized by ample time and/or distance to avoid a collision.

• “D” = Insufficient information, inconclusive or conflicting evidence precludes severity assessment



Background• The categorization of the severity of runway

incursions is a tool to help represent risk in the system.

• Risk = probability of an event x severity of the outcome

• In order to be defensible, ratings need to be valid and reliable.– Valid = an “A” is really an “A”– Reliable = an “A” is always an “A”

• Inter-rater: An “A” for Peter is an “A” for Paul• Over time: An “A” today is an “A” tomorrow



Components of the Model

• A rating is assigned based on the closest proximity (CP) and the factors that contribute to the variability of that proximity (probability of a collision).– CP - both horizontal and vertical - is measured at the

end of the conflict OR the point at which all parties are aware of the situation and have the aircraft under control at taxi speed or less.



Components of the Model (continued)

• Assumptions– Some scenarios are more serious at the same CP

than others (e.g, head-on is worse than tail-chase) – There are factors that increase the variability of the

response and resulting CP, for example:• Actions with short response time• Larger aircraft (more variable stopping distance)• Contaminated runways



Benefits of the Model

• Rankings are reliable – same event will result in the same rating every time.– Reliable ratings are necessary to have confidence in

trends of system performance.

• Counts of types of scenarios (e.g., crossing in front of a takeoff, landovers) is automatic.



How the Model Works• Rater is asked a series of questions and

selects answers to classify the event as a scenario– For example, what was the aircraft doing? (taking

off, landing, taxiing, stopped)• If taking off, did the aircraft takeoff or abort takeoff?

– What did the other aircraft or vehicle do? (For example, crossed runway, crossed hold short line, etc)

• Rater enters additional information about the event into three categories: visibility, avoidance maneuver, human error.



Information Selected by the Rater

• Ceiling and Visibility, RVR, Day/Night• Aircraft type• Types of human error – pilot error,

controller error, communication error• Avoidance maneuvers

(initiated/commanded)• Characteristics of avoidance maneuver (for

example, point at which go-around was initiated)



Aircraft Type

• Aircraft Type = FAA weight categories– S = less than 12,500 lbs– S+ = 12,500 – 40, 999 lbs– L = 41,000 – 254,999– H = or greater than 255,000



Avoidance Maneuver Categories

• Early rotation on takeoff (as reported by pilot)

• Aborted takeoff (reported distance rolled)• Swerve (reported or observed)• Hard/maximum braking (reported or

observed)• Go-around (point at which GAR was

initiated/commanded)



Examples of Error Categories - (Degree of Control)

• Controller unaware of (or forgot about) aircraft or vehicle.

• Controller forgot runway was closed.• Controller misidentified aircraft and

issued instruction to wrong aircraft.• Pilot took off/landed on wrong runway.• Wrong aircraft accepted a clearance.



Examples of Communication Factors• Total communication failure (e.g., stuck mike)• One or more party (e.g., vehicle) not on

frequency• Completely blocked transmission• Partially-blocked (stepped-on) transmission • Controller unable to contact aircraft • Pilot unable to contact controller



ExampleInput: • C-150 crossed hold short lines (but did not enter

runway) with another aircraft (C-150) taking off. • Aircraft taking off rotated normally after passing

through the intersection (no avoidance maneuver).

• Closest horizontal proximity = 100’ as aircraft passed through the intersection

• Visibility: 10 miles - day• Error: Pilot read back “hold short” instruction

correctly but then crossed the hold short lines.



Example

• Output:– Rating = 1.0 = “D”



Example of Most Common ScenariosN = 906

SITUATION OF CROSSING/POTENTIAL CROSSING IN FRONT OF A LANDING : 406 (44%)

Landing a/c went around 282 (70%) The taxiing aircraft crossed the hold-short line, and the landing aircraft went around. 93 The taxiing aircraft entered the runway, and the landing aircraft went around. 136 The taxiing aircraft crossed the runway, and the landing aircraft went around. 53

Landing a/c landed – touched down after intersection 13 The taxiing aircraft crossed the hold-short line, and the landing aircraft landed after the intersection. 7 The taxiing aircraft entered the runway, and the landing aircraft landed after the intersection. 3 The taxiing aircraft crossed the runway, and the landing aircraft landed after the intersection. 3

Landing a/c landed – touched down before intersection 111 The taxiing aircraft crossed the hold-short line, and the landing aircraft landed before the intersection. 35 The taxiing aircraft entered the runway, and the landing aircraft landed before the intersection. 29 The taxiing aircraft crossed the runway, and the landing aircraft landed before the intersection. 47



Example of Most Common Scenarios (continued)N = 906

SITUATION OF CROSSING/POTENTIAL CROSSING IN FRONT OF A TAKEOFF : 242 (27%)

Aircraft took off – rotated before the intersection 112 The taxiing aircraft crossed the hold-short line, and the takeoff rotated before the intersection. 37 The taxiing aircraft entered the runway, and the takeoff rotated before the intersection. 33 The taxiing aircraft crossed the runway, and the takeoff rotated before the intersection. 42

Aircraft took off – rotated after the intersection 51 The taxiing aircraft crossed the hold-short line, and the takeoff rotated after the intersection. 17 The taxiing aircraft entered the runway, and the takeoff rotated after the intersection. 2 The taxiing aircraft crossed the runway, and the takeoff rotated after the intersection. 32

Aircraft aborted take off 78 (33%) The taxiing aircraft crossed the hold-short line, and the takeoff aborted. 36 The taxiing aircraft entered the runway, and the takeoff aborted. 42 The taxiing aircraft crossed the runway, and the takeoff aborted. 1

runway incursion severity categorization (risc) model

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