ARIWS – Autonomous Runway Incursion Warning Systems

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ARIWS – Autonomous Runway Incursion Warning Systems

57TH ANNUAL CONFERENCE, Accra, Ghana, 19-23 March 2018

WP No. 88

ARIWS – Autonomous Runway Incursion Warning Systems

Presented by TOC

Summary

This paper highlights the implementation of autonomous runway incursion warning systems developed to improve runway safety. A comparison is made on the development of similar systems and to the standing provisions on ARIWS by ICAO and the existing IFATCA policy on runway status lights (RWSL).

Introduction

1.1 Definition

Autonomous runway incursion warning system (ARIWS). A system which provides autonomous detection of a potential incursion or of the occupancy of an active runway and a direct warning to a flight crew or a vehicle operator. Source: International Civil Aviation Organization

((ICAO), Annex 14 Aerodromes, Volume I Aerodrome Design and Operations, 7th Edition (July 2016), Chapter 1 – Definitions)


1.2 Relation of ARIWS to Runway Safety

As runway incursions have sometimes led to serious incidents and accidents with significant loss of life, it is therefore imperative that the hazards are controlled and the risks associated with runway operations are mitigated. While runway safety takes into account issues such as foreign object debris (FOD), wildlife hazards and other logistical deficiencies, the implementation of ARIWS specifically addresses the safe operation of aircraft and vehicle movement on the runway.


1.3 Operational Concept

ARIWS uses available surveillance data but operates independently from ATC systems or controller input to monitor the actual situation on a runway and to autonomously generate visual alerts in accordance with the motion and velocity of the detected traffic in the form of airfield lighting displayed directly to flight crew and vehicle operators.


1.4 Benefit of the System

These systems act as a visual verification of an occupied runway. They create an additional layer of runway safety that aids to increase situational awareness for pilots and vehicle drivers that the runway is not safe.


1.5 Existing IFATCA policy on RWSL

IFATCA existing policy on RWSL is referenced from WP 89 in Amman 2011 which covered the description and potential issues associated with the implementation of such systems to reduce runway incursions that are similar to the current ICAO standing provisions on ARIWS.

IFATCA supports RWSL provided the following criteria are met:

  • The system will be used as a safety net.
  • It will operate automatically with no controller input required.
  • The system specifications are globally harmonized under ICAO guidance.
  • Potential confusion with other lighting systems is eliminated or mitigated.
  • Clearance to proceed will still be required.
  • All surface traffic will be required to comply with the system.
  • Comprehensive training is provided to all pilots, drivers and controllers.
  • False activations are kept to an absolute minimum.

If RWSL activations are displayed to the controller, the following criteria should be met:

  • The information should be efficiently incorporated into existing surveillance displays at the appropriate control positions.
  • Legal responsibilities are clearly and unambiguously defined.

(IFATCA Technical and Professional Manual, 2017 edition, ADME 2.14 Runway Status Lights (RWSL), page 3 2 2 16, WP 89 – Amman 2011)

Discussion

2.1 Statistical Information

In the USA during the period between 2012 and July 2017, the total number of runway incursions that occurred were 7,864. 63% (4,947) of the runway incursions were related to pilot issues, 20% (1,529) were related to ATC issues and 17% (1,388) were related to vehicle/pedestrian crossings. While European member states between the period of 2010 and 2014 reported the number of serious (severity A) runway incursions almost doubled from 14 events in 2013 to 26 in 2014. Another significant increase of 21% is observed in the number of major events (severity B). The threat of runway incursions continues to be at the top of the list of major air safety concerns for these regions. Runway safety remains with no doubt a significant challenge and a top priority.


2.2 Program Development

As a result of improved identification of the areas of risk due to safety culture enhancements through the encouragement of employees to actively participate in the safety management systems of air traffic organizations, more data has been yielded than the decades before. This data has enabled the FAA to address safety risks more effectively and adopt new technology, operating procedures, training etc. It is from here that the Runway Status Lights RWSL program came in to development as a data-driven solution and in operating capability in the effort to improve runway safety. RWSL systems are already operational in the US, Japan and France.


2.3 RWSL System Description

RWSL is a fully automated system and independent safety enhancement that processes information from surveillance systems and provides runway status information to pilots and vehicle drivers. Potential conflicts are detected in real time in accordance with the position and velocity of the detected surface and approach traffic. Runway Entrance Lights (REL), Takeoff Hold Lights (THL), Runway Intersection Lights (RIL), and Final Approach Runway Occupancy Signal (FAROS) all activate autonomously to clearly indicate when a potential hazard exists on a runway. Activation of the lights does not substitute or convey an ATC clearance. Clearance to enter, cross, takeoff from, land on, or operate on a runway must still be received from ATC. ATC has limited control over the systems, personnel do not directly use and may not be able to view light fixture activations and deactivations during the conduct of daily ATC operations.


2.4 Similar Systems Comparisons & Future Developments

2.4.1 Stop Bars

Similar systems installed such as Stop Bars have been designed to provide protection at runway/taxiway intersections and to reduce the risk of runway incursions. They are a series of unidirectional lights at right angles to the taxiway centerline. However, these systems are manually controlled by ATC in conjunction with an ATC clearance. They do not operate autonomously and as such are not considered a part of ARIWS.

(Source: ICAO)

2.4.2 Final Approach Runway Occupancy Signal (FAROS) & Enhanced FAROS (eFAROS)

REL, THL, and RIL are all in-pavement light fixtures that are directly visible to pilots and vehicle drivers. However, FAROS/EFAROS are advisory systems that alert arriving pilots that the approaching runway is occupied by flashing the Precision Approach Path Indicator (PAPI). FAROS/EFAROS are not considered basic elements of a RWSL system and may be implemented as an add-on or as a standalone system at airports without a RWSL system.

(Source EFAROS.org)

Its activation does not affect the validity of an existing ATC landing clearance in the sense that an aircraft can be established on the approach and cleared to land following successive aircraft ahead on the final approach in sequence as is the practice in the USA to reduce VHF exchanges. Therefore, the pilot may observe the visual flashing signals activate all along the approach until their acquisition/contact point is reached and a decision will have to be made if the runway is still occupied. It must be also emphasized that a steady PAPI signal does not constitute a clearance to land. ATC must be contacted to verify the landing clearance should any safety concern exist.

It is also not intended to act as an effective system in the case of the collision hazard which may arise during simultaneous operation of intersecting runways.

FAROS concept was first tested from 08/2006 through 09/2010 using embedded loops to activate, flashing the PAPIs whenever a target was in an activation zone by detecting a change in the magnetic field irrespective of an aircraft on final. Operational evaluations determined the need to reduce unnecessary alerts and readjustment of activation parameters. As a result, the FAA introduced enhanced FAROS (eFAROS) conducting assessments from 09/2011. Its operational evaluation is continuing indefinitely as an experimental system using surveillance data to activate flashing PAPIs only if an aircraft is on final approach.

2.4.3 Runway Intersection Lights (RIL)

RIL are used where one runway intersects another to visually indicate to pilots and vehicle drivers that there is high speed traffic on the intersecting runway and that it is unsafe to enter or cross. However, in regard to RIL, airports with simultaneous operations of crossing runways may have potential problems with the flow of traffic when Land and Hold Short Operations (LAHSO) are enabled. LAHSO are ATC procedures for aircraft landing and holding short of an intersecting runway or a point on a runway. They are primarily enabled to increase the airport capacity and efficiency. IFATCA policy opposes the use of LAHSO unless certain concerns are satisfactorily addressed. However, when LAHSO is enabled, pilots will be able to see red RIL and misunderstand that they should remain stopped because the RILs are acting as RELs.

(Source: MIT)


2.5 ICAO Description of RWSL & ARIWS

ICAO defines RWSL as a type of ARIWS and that the two basic visual components of RWSL that compliment each other are REL and THL. RIL, FAROS/eFAROS are not mentioned as components of RWSL due to their current potential issues and their ability to be installed as stand-alone systems.

5.3.30 Runway status lights

Introductory Note.— Runway status lights (RWSL) is a type of autonomous runway incursion warning system (ARIWS). The two basic visual components of RWSL are runway entrance lights (RELs) and take-off hold lights (THLs). Either component may be installed by itself, but the two components are designed to be complementary to each other.

(Source: International Civil Aviation Organization (ICAO), Annex 14 Aerodromes, Volume I Aerodrome Design and Operations, 7th Edition (July 2016), Chapter 5 Visual aids for navigation)

 

The objectives of ARIWS and RWSL are the same and the end result is to give real time warnings of potential runway incursions to indicate if it is unsafe to enter, cross or depart from a runway. However, no type of airborne visual warning system to alert pilots that it is unsafe to land is mentioned in the description of ARIWS.

15.7.5 Other ATC contingency procedures

Note 1.— The generation of ARIWS warnings is a function based on surveillance data. The objective of the ARIWS function is to assist flight crews and vehicle drivers in the prevention of runway incursions by generating, in a timely manner, a direct warning of a possible runway hazard making it unsafe to enter, to cross a runway or take-off.

(Source: International Civil Aviation Organization (ICAO), PANS-ATM (Doc 44444), 16th Edition (November 2016), Chapter 15 Procedures related to emergencies, communication failure and contingencies)


2.6 ICAO Documentation and Existing IFATCA Policy

A comparison is made between the existing IFATCA policy regarding RWSL and ICAO ARIWS documentation to compare the operating criteria to see if both systems may be amalgamated.

The system will be used as a safety net.

(IFATCA Technical and Professional Manual, 2017 edition ADME 2.14 Runway Status Lights (RWSL), page 3 2 2 16, WP 89 – Amman 2011)

 

In regard to the above IFATCA policy, ICAO (November 2016) PANS-ATM (Doc 4444, 16th Edition) describes the function of ARIWS as a system which provides autonomous detection of a potential incursion or of the occupancy of an active runway and a direct warning to a flight crew or a vehicle driver which has the similar concept of a safety net.

Following subsequent meetings of IFATCA Technical and Operations Committee (TOC) that were held during September 2017 it was discussed that ARIWS was not considered either a ground-based or airborne safety net as also considered by ICAO. The term ‘ground-based’ implies that a warning is activated to ATC instead of the pilot. The functionality of a ground-based safety net must be within the ATM system with the sole purpose of monitoring the operational environment in order to provide timely alerts of a potential increased risk to flight safety. Airborne safety nets on the other hand provide alerts and resolution advisories of a shorter time frame directly to pilots to immediately take appropriate avoiding action.

Safety nets are implemented to help prevent imminent or actual hazardous situations from developing into major incidents or even accidents. Therefore, if a warning is received from a ‘safety net’ to a pilot or to ATC, then most probably an actual hazardous situation exists. In regard to ARIWS, the activation of warning lights does not necessarily mean that an imminent or actual hazardous situation has been detected, which hereby defies the concept of a safety net. However, this can be true for almost all other safety nets. Minimum Safe Altitude Warning (MSAW) for an example can generate a warning in a situation where the aircraft is flying safely with visual ground contact or when commencing a visual approach.

In conclusion, ARIWS may not yet be defined as a safety net or fit the definition of ground-based or airborne. However, its primary function is to autonomously detect runway incursions without the input of ATC and display a direct warning to pilots or vehicle drivers to prevent a hazardous situation which is the primary objective of the safety net concept. ARIWS does not change the normal way of working of ATC / pilots / vehicle drivers. It is implemented to provide an additional safety margin on top of the safety provisions of ATS and aviation operations. When implemented and operated appropriately, these warnings have been demonstrated in actual operations to prevent potential runway incursions from developing into an incident/accident, which is a clear risk reduction system that serves the purpose of a safety net.

This policy is important to reflect the function of ARIWS as a safety net until it is mandated as such for its use.

It will operate automatically with no controller input required.

(IFATCA Technical and Professional Manual, 2017 edition ADME 2.14 Runway Status Lights (RWSL), page 3 2 2 16, WP 89 – Amman 2011)

 

15.7.5 Other ATC Contingency procedures

Note 2 – The function of ARIWS is to operate independently from ATC, and the warnings are generated for pilots and vehicle drivers.

(Source: International Civil Aviation Organization (ICAO), PANS-ATM (Doc 44444), 16th Edition (November 2016), Chapter 15 Procedures related to emergencies, communication failure and contingencies)

 

5.3.30.10 – Recommendation RELs and THLs should be automated to the extent that the only control over each system will be to disable one or both systems.

(Source: International Civil Aviation Organization (ICAO), Annex 14 Aerodromes, Volume I Aerodrome Design and Operations, 7th Edition (July 2016), Chapter 5.3.30 – Runway status lights)

 

This policy has now become an ICAO standing provision and can therefore be deleted as IFATCA policy.

The system specifications are globally harmonized under ICAO guidance.

(IFATCA Technical and Professional Manual, 2017 edition ADME 2.14 Runway Status Lights (RWSL), page 3 2 2 16, WP 89 – Amman 2011)

 

ICAO Annex 14, Volume 1, (Seventh Edition), Chapter 5.3.30 Runway Status Lights describes the location of the lights and characteristics of RWSL (REL & THL) when provided. ICAO Annex 14, Volume 1, (Seventh Edition), Chapter 9.12 Autonomous runway incursion warning system, describes the characteristics of ARIWS.

This policy has now become an ICAO standing provision and can therefore be deleted as IFATCA policy.

Potential confusion with other lighting systems is eliminated or mitigated.

(IFATCA Technical and Professional Manual, 2017 edition ADME 2.14 Runway Status Lights (RWSL), page 3 2 2 16, WP 89 – Amman 2011)

 

Initial assessments during the implementation of RWSL in the US through feedback from pilots revealed that the THL needed to be distinct from end-of-runway lights and during low visibility they needed to be more conspicuous. During that time THL consisted of a single row of 11 lights along the centerline. Implemented resolutions to the feedback changed THL to a double row of 16 lights along the centerline. Five pair of lights were added and THL were made brighter than REL so each system was wired separately. ICAO documentation describes the orientation and the position of the lights, further operational evaluation and feedback from pilots for each airport is required to establish the optimum intensity and if any confusion exists.

5.3.30.3 Where provided, THLs shall be offset 1.8m on each side of the runway centre line lights and extend, in pairs, starting at a point 115m from the beginning of the runway and, thereafter, every 30m for at least 450m.

Note.— Additional THLs may be similarly provided at the starting point of the takeoff roll.

(Source: International Civil Aviation Organization (ICAO), Annex 14 Aerodromes, Volume I Aerodrome Design and Operations, 7th Edition (July 2016), Chapter 5.3.30 – Runway status lights)

 

450m is equivalent to 16 pair of lights extending from a point or starting point of the take-off roll.

Note 1.— An ARIWS may be installed in conjunction with enhanced taxiway centre line markings, stop bars or runway guard lights.

(Source: International Civil Aviation Organization (ICAO), Annex 14 Aerodromes, Volume I Aerodrome Design and Operations, 7th Edition (July 2016), Chapter 9.12.1 Autonomous runway incursion warning system – Characteristics)

 

This policy has now become an ICAO standing provision and can therefore be deleted as IFATCA policy.

ICAO has described the installation of the lights and given the possibility of installing additional lights to mitigate any potential confusion of lights. However, it is the operational evaluation of the system and feedback as mentioned above that is necessary to make any changes which may differ from one airport platform to another.

Clearance to proceed will still be required.

 (IFATCA Technical and Professional Manual, 2017 edition ADME 2.14 Runway Status Lights (RWSL), page 3 2 2 16, WP 89 – Amman 2011)

 

21.2.2 It must also be stressed that the extinguishing of the red lights does not, in itself, indicate a clearance to proceed. That clearance is still required from air traffic control. The absence of red warning lights only means that potential conflicts have not been detected.

(Source: International Civil Aviation Organization (ICAO), Annex 14 Aerodromes, Volume I Aerodrome Design and Operations, 7th Edition (July 2016), Attachment A, Chapter 21.1 Flight Crew Actions)

 

This policy has now become an ICAO standing provision and can therefore be deleted as IFATCA policy.

All surface traffic will be required to comply with the system.

(IFATCA Technical and Professional Manual, 2017 edition ADME 2.14 Runway Status Lights (RWSL), page 3 2 2 16, WP 89 – Amman 2011)

 

Even though ARIWS is designed to be complementary to ATS functions by increasing the situational awareness of pilots and vehicle drivers, the nature of the warnings generated are critical because the timeline involved leaves no room for misinterpretation or reconfirmation of the signal and therefore operational compliance is vital. The basic function and operational compliance of the system requires that pilots and vehicle drivers stop immediately to a universal signal (red light) and then verify with ATC. Technical compliance depends upon the use of multiple surveillance systems that may require vehicles to be equipped or by using existing systems that are able to detect and monitor all surface traffic and the actual situation on a runway independently from ATC.

15.7.5.1 a) the flight crew or vehicle driver shall give priority to the ARIWS warning over the ATC clearance. They shall not proceed onto the runway or commence the take-off roll. The flight crew or vehicle driver shall inform the controller of the ARIWS warning and await further clearance; and

(Source: International Civil Aviation Organization (ICAO), PANS-ATM (Doc 44444), 16th Edition (November 2016), Chapter 15 Procedures related to emergencies, communication failure and contingencies)

 

It must also be noted that, not all runway entrances and thresholds need to be equipped with ARIWS. This will depend on the characteristics of the airport platform and so will the technical compliance respectively. However, the warning provided must be understood by all and complied with.

This policy has now become an ICAO standing provision and can therefore be deleted as IFATCA policy.

Comprehensive training is provided to all pilots, drivers and controllers.

(IFATCA Technical and Professional Manual, 2017 edition ADME 2.14 Runway Status Lights (RWSL), page 3 2 2 16, WP 89 – Amman 2011)

 

The challenges faced in the prevention of runway incursions may be uniquely different from one airport to another due to the complexity of the airport platform, the density of air traffic, capacity enhancements and so forth. These factors when combined with inadequate training, can lead to an increased risk of runway incursions.

(Source: Airliners.net)

The majority of runway incursions statistically are due to pilot deviations. These may include inadvertent non-compliance of ATC clearances, but often the case is a result of a breakdown of communications or a loss of situational awareness.

Communication issues involves all participants. In order to maintain a high level of situational awareness, instructions being transmitted in an environment associated with runway operations must be accurately received, understood and confirmed.

(Source: Airliners.net)

Training is critical to the success of ARIWS implementation because it is a timely and complex issue. It requires the adjustment of multiple parameters, calibration of warning software and correct on/off timing of alerts. These aspects require operational evaluations and feedback from Pilots/ATC who are trained in the operation of the system. This is not only critical to eliminate implementation issues, but also in establishing a uniqueness of the lights and their conspicuousness compared to other lighting systems on the airport surface.

21.4.4 Each aerodrome where the system is installed will develop procedures depending upon its unique situation. Again, it must be stressed that under no circumstances should pilots or operators be instructed to “cross the red lights”. As indicated previously, the use of local runway safety teams can greatly assist in this development process.

(Source: International Civil Aviation Organization (ICAO), Annex 14 Aerodromes, Volume I Aerodrome Design and Operations, 7th Edition (July 2016), Attachment A, Section 21.4.4, Air traffic services)

 

21.5.2 Aircraft operators are to ensure that flight crews’ documentation include procedures regarding ARIWS and appropriate guidance information, in compliance with Annex 6, Part I.

21.5.3 Aerodromes may provide additional sources of guidance on operations and procedures for their personnel, aircraft operators, ATS and third-party personnel who may have to deal with an ARIWS.

(Source: International Civil Aviation Organization (ICAO), Annex 14 Aerodromes, Volume I Aerodrome Design and Operations, 7th Edition (July 2016), Attachment A, Section 21.5, Promulgation of information)

 

This policy is crucial to the success of the system. If pilots and vehicle drivers are not sufficiently trained and familiar with ARIWS installations, they may continue to follow ATC instructions believing that ATC directives supersede ARIWS activations not knowing that ATC may not able to observe these lights.

False activations are kept to an absolute minimum.

 (IFATCA Technical and Professional Manual, 2017 edition ADME 2.14 Runway Status Lights (RWSL), page 3 2 2 16, WP 89 – Amman 2011)

 

Not all airport layouts are complex and not every ARIWS installation requires comprehensive ground surveillance systems.

(Source: Airliners.net)

ARIWS utilize existing airport surveillance technology in conjunction with highly advanced data integration techniques and state logic to generate warnings. The location of traffic is provided by diverse surveillance sources such as 1) primary radar returns from airport surface detection equipment, 2) multilateration sensors, 3) terminal radars and 4) ADS-B. The practical problems associated with deactivated, malfunctioning or non-compliant transponders and multilateration systems is that they can produce both desired transponder replies and unsolicited replies which must be dealt with by the system even as integration techniques to these problems are still under development. The system as a consequence integrates data from multiple sensors to create ‘clean’ system tracks to address malfunctions or the nonexistence of other sensors or equipment. Surveillance data can also be used singlehandedly in case of other sensor outages or maintenance which makes it more flexible in various situations. However, after the integrated surveillance is accepted by a safety logic process, the operational state of the track (stopped, taxiing, landing, or departing) is determined and a future behaviour is predicted based on the current state to determine which lights to be illuminated. Location of traffic and other dynamic states drive the decision-making process for light illuminations. False activations may usually be a result of the parameters set by the user and the calibration of the system. This requires operational evaluation for each airport layout together with feedback from pilots/ATC to assess the parameters and avoid nuisance alerts.

In no case should the illumination of the ARIWS be dismissed without confirmation that, in fact, there is no conflict. It is worth noting that there have been numerous incidents avoided at aerodromes with such systems installed. It is also worth noting that there have been false warnings as well, usually as a result of the calibration of the warning software, but in any case, the potential conflict existence or nonexistence must be confirmed.

(Source: International Civil Aviation Organization (ICAO), Annex 14 Aerodromes, Volume I Aerodrome Design and Operations, 7th Edition (July 2016), Attachment A, Section 21.4.4, Air traffic services)

 

This policy is especially important in regard to ARIWS as false activations may disrupt the normal flow of traffic significantly since they must be complied with regardless a potential conflict exists or not. Compliance is therefore critical to the function of ARIWS because of the timeline involved and because the compliance serves to re-enforce the universal signal to stop. Furthermore, as airport layouts differ the calibration parameters may also differ.

If RWSL activations are displayed to the controller, the following criteria should be met:

– The information should be efficiently incorporated into existing surveillance displays at the appropriate control positions.

– Legal responsibilities are clearly and unambiguously defined.

(IFATCA Technical and Professional Manual, 2017 edition ADME 2.14 Runway Status Lights (RWSL), page 3 2 2 16, WP 89 – Amman 2011)

 

The objective of ARIWS is to generate warnings of a timely nature to pilots and vehicle drivers that need to be interpreted during a critical phase. If the warning is generated, then the potential for conflict may be present. Relevant surface traffic will stop in compliance to ARIWS and advise ATC for further instructions. ATC will have to assess the conflict area and provide further instructions. Any ARIWS activations displayed to ATC may increase the situational awareness of the runway environment in a timely manner. Poorly displayed information could increase controller workload and reduce situational awareness. ATC will have to establish procedures on the display of such information if necessary and have the possibility to control the system in the event of a malfunction.

21.4.3 While many installations may have a visual or audio warning available to ATS personnel, it is in no way intended that ATS personnel be required to actively monitor the system. Such warnings may assist ATS personnel in quickly assessing the conflict in the event of a warning and help them to provide appropriate further instructions, but the ARIWS should not play an active part in the normal functioning of any ATS facility.

(Source: International Civil Aviation Organization (ICAO), Annex 14 Aerodromes, Volume I Aerodrome Design and Operations, 7th Edition (July 2016), Attachment A, Section 21.4.4, Air traffic services)

 

15.7.5 Autonomous runway incursion warning system 15.7.5.2 ATS units shall have procedures in place for situations when controllers are informed of ARIWS warnings, including how to disable the ARIWS in case of malfunctions.

(Source: International Civil Aviation Organization (ICAO), PANS-ATM (Doc 44444), 16th Edition (November 2016), Chapter 15 Procedures related to emergencies, communication failure and contingencies)

 

21.2.4 Procedures should be developed to address the circumstance where the system fails in the illuminated condition. It will be up to the ATS and/or aerodrome operator to establish those procedures depending on their own circumstances. It must be remembered that flight crews are instructed to “STOP” at all red lights. If the affected portion of the system, or the entire system, is shut off the situation is reverted to the extinguished scenario described in 21.2.3.

(Source: International Civil Aviation Organization (ICAO), Annex 14 Aerodromes, Volume I Aerodrome Design and Operations, 7th Edition (July 2016), Attachment A, Chapter 21.1 Flight Crew Actions)

 

This policy is important to ensure that the quality of the displayed information, when installed, aids to increase the controller’s situational awareness and does not increase their workload. An amendment to the second part of the policy can be made as ICAO does not require ATC to actively monitor the system or that the system be an active part of the normal function of any ATS facility.


2.7 Operational Concept of ARIWS

The operational protocol of ARIWS is similar to that of RWSL (THL & REL).

21.1.1 The operation of an ARIWS is based upon a surveillance system which monitors the actual situation on a runway and automatically returns this information to warning lights at the runway (take-off) thresholds and entrances. When an aircraft is departing from a runway (rolling) or arriving at a runway (short final), red warning lights at the entrances will illuminate, indicating that it is unsafe to enter or cross the runway. When an aircraft is aligned on the runway for take-off and another aircraft or vehicle enters or crosses the runway, red warning lights will illuminate at the threshold area, indicating that it is unsafe to start the take-off roll.

(Source: International Civil Aviation Organization (ICAO), Annex 14 Aerodromes, Volume I Aerodrome Design and Operations, 7th Edition (July 2016), Attachment A, Section 21.1 General description)


2.8 Operational Procedures – Scenario 1

In the event of an ARIWS warning generated, the interpretation of the visual warning is distinct for pilots and vehicle drivers and the operational compliance is to stop immediately. They shall not proceed onto the runway or commence the take-off roll as they are instructed to stop at all red lights in response to a globally consistent visual signal. The function of ARIWS is to operate independently from ATC, therefore when a warning is generated that conflicts with an ATC clearance, pilots and vehicle drivers will give priority to the ARIWS warning over the ATC clearance until the situation is verified by the controller. Controllers must not issue a clearance to cross any red lights even if the system fails in the illuminated condition. This is to re-enforce the interpretation of the visual signal to stop and to aid in their timely reaction accordingly. Controllers should cancel previous clearances, visually scan the entire runway, assess the situation and then re-issue a new clearance.

15.7.5 Autonomous runway incursion warning system 15.7.5.1 In the event an ARIWS warning is generated that conflicts with the ATC clearance, the following action shall be taken by flight crew and vehicle drivers: a) the flight crew or vehicle driver shall give priority to the ARIWS warning over the ATC clearance. They shall not proceed onto the runway or commence the take-off roll. The flight crew or vehicle driver shall inform the controller of the ARIWS warning and await further clearance;

(Source: International Civil Aviation Organization (ICAO), PANS-ATM (Doc 44444), 16th Edition (November 2016), Chapter 15 Procedures related to emergencies, communication failure and contingencies)


2.9 Operational Procedures – Scenario 2

Operational procedures in the event that an ARIWS fails in the illuminated condition will require pilots and vehicle drivers to also stop, inform the controller of the warning and await further clearance. Controllers should cancel previous clearances, visually scan the entire runway, shut off the affected portion of the system, or the entire ARIWS system and then re-issue a new clearance. The procedures for pilots and vehicle drivers must stress that the extinguishing of the red lights does not indicate a clearance to proceed. The absence of red lights only means the potential of a conflict is not detected.


2.10 Operational Procedures – Scenario 3

Operational procedures in the event that an aircraft or vehicle has initiated actions to comply with a clearance that conflicts with an ARIWS warning permit the pilots or vehicle drivers to use their best judgement to resolve a conflict if it is not safe to abort the departure or crossing of a runway. They must still understand that it is unsafe to take-off or cross the runway. In all cases, ATC should be advised of their actions when practicable and of the ARIWS warning.

15.7.5 Autonomous runway incursion warning system 15.7.5.1 In the event an ARIWS warning is generated that conflicts with the ATC clearance, the following action shall be taken by flight crew and vehicle drivers: b) in the event the aircraft or vehicle has initiated actions to comply with a clearance that conflicts with the warning, the flight crew or the vehicle driver shall use the warning to exercise their best judgement and full authority in the choice of the best course of action to resolve any potential conflict. The controller should be informed, when practicable, of the ARIWS warning.

(Source: International Civil Aviation Organization (ICAO), PANS-ATM (Doc 44444), 16th Edition (November 2016), Chapter 15 Procedures related to emergencies, communication failure and contingencies)


2.11 Operational Procedures – Scenario 4

If an ARIWS fails in the extinguished condition, no procedural changes need to be made. Both ATC operations and flight crew procedures remain unchanged.


2.12 Runway Entrance Lights (REL) & Take-off Hold Lights (THL) Operational Survey

During December 2017, a survey was conducted and administered by IFATCA – TOC regarding the operation of ARIWS. The purpose of the survey was to receive feedback and operational evaluation of practical significance from the installed systems amongst pilots.

The invitation to participate in the survey was sent by IFALPA by email through which 125 pilots across 36 major airlines responded to the survey. The survey was conducted by means of an online questionnaire given to the pilots to complete. The first part of the questionnaire dealt with the operational feedback of REL and the second section was concerned with THL and finally an opportunity to comment. All pilots were 99% familiar with the airports surveyed.

2.12.1 Runway Entrance Lights Survey Data

From the table of data, the most significant items were as follows.

34% of the pilots who took the survey have never observed REL turn on in response to traffic. However, in total, 47% of the pilots do not think that REL have priority over ATC clearances and 13% think that extinguished REL indicate a clearance to proceed. These figures indicate a lack of awareness on the objective and operation of the system.

Over 80% of the operation of REL was consistent with ATC clearances and the traffic situation. Only 5% indicated a non-consistency with the traffic situation where the REL where still ON when they should have been OFF. This delay of switching OFF the REL and ATC anticipation of the traffic situation lead to queries from pilots and has shown a 12% increase in VHF exchanges even as reported in minimum occupancy runway operation.

It is also important to note from a pilot’s perspective that 88% of the pilots do not consider the operation of REL to increase their workload. In fact, 93% think the lights are visible enough and 97% indicate REL increased their situational awareness. In regards to the risk of confusion between REL and other airport lights, 11% indicate a possible risk of confusion between pilots unfamiliar with the lights and the resemblance to stop bar on and off operations. However, during LVP with joint operations of stop bars and REL the risk of confusion was reduced further with only 2% of the pilots who think that alternating lights on and off could cause confusions.

In an overall view, 89% of the pilots think REL provide an effective and direct means to make them aware the runway is safe to enter/cross. 93% believe REL will help reduce the number and severity of runway incursions. 95% have a positive overall opinion about REL.

2.12.2 Take-off Hold Lights Survey Data

In this second section, the most significant item was that 61% of the pilots do not think that THL have priority over ATC clearances and 9% think that extinguished THL indicate a clearance to proceed. This again as above indicates the lack of awareness on the objective and operation of the system.

Nearly 99% of the operation of THL were consistent with ATC clearances and the traffic situation. Only 1% indicated a non-consistency with the traffic situation where the THL were still ON when they should have been OFF. Increased VHF exchanges of only 7% were not related to any non-consistent traffic situation but rather as a result of being unfamiliar with the THL operation. 86% indicate the operation of THL was compatible with multiple line up operations.

Again from a pilot’s perspective, 90% of the pilots do not consider the operation of THL to increase their workload. 96% of the pilots think that THL increased their situational awareness. In regards to the risk of confusion between THL and other airport lights, 90% think the lights were visible enough and 92% do no think that there is any possible risk of confusion with other airport lights. The remaining 8% of the pilots were unfamiliar with the lights and others may interpret the extinguished lights as a clearance to proceed.

In an overall view, 95% of the pilots think THL provide an effective and direct means to make them aware the runway is safe to take-off. 95% believe THL will help reduce the number and severity of runway incursions. 99% have a positive overall opinion about THL.

2.12.3 Further Comments & Suggestions

Most of the comments in conclusion expressed the operation of the system as an excellent visual aid that can reduce runway incursions and increase situational awareness which can be installed at many other airports. The lack of knowledge when used at only one airport can make it more dangerous than useful as not many pilots are yet familiar with its operation.

Given the considerable time it takes to move an aircraft of several tons, ATC anticipation of clearances to increase runway usage has led at times to discrepancies with REL state being still on with a clearance from ATC to line up. There is still a margin where perhaps ATC is anticipating too much or there is too much delay before the REL extinguishes. This will require further evaluation and/or calibration and timing of the alerts.

The joint use of stop bars and REL can reduce the initial risk of unfamiliar pilots mistaking extinguished REL as a clearance to proceed. This is important to avoid confusion as not all airports are currently installed with ARIWS. A further suggestion was made to the shape of the lights to be made from red rectangles to red crosses to make them even more conspicuous.


2.13 Operational Experience & Challenges

Operational experience regarding ARIWS is still very limited. Issues to evaluate the calibration of the parameters and on/off timing of the alerts, optimum intensities of the lights, false warnings, increased VHF exchanges during alerts etc. require extensive operational evaluation which we are lacking to enhance the procedures that need to be established.


2.14 Use of Phraseology specifically on ARIWS

No phraseology has been adopted regarding ARIWS. Guidance must be disseminated to pilots and vehicle drivers to eliminate communication ambiguity. Non-standard phraseology may increase VHF exchanges during alerts, increasing ATC workload and may disrupt the normal flow of traffic.

Conclusions

3.1 Autonomous Runway Incursion Warning Systems (ARIWS) are advisory safety nets for surface movement that operate independently from ATC systems to autonomously generate visual alerts displayed directly to flight crew and vehicle operators in the form of airfield lighting in accordance to the motion and velocity of detected traffic. These systems create an additional layer of runway safety aiming to increase situational awareness for pilots and vehicle drivers in the prevention of runway incursions.

3.2 RWSL consist only of THL and REL and is considered a sub-system of ARIWS. Other sub-systems of ARIWS such as eFAROS and RIL are still under development due to the interference they cause to the normal ATC flow of traffic during simultaneous operations of crossing runways and airborne visual warning systems for pilots.

3.3 ICAO has taken the step to ensure global consistency in the implementation of ARIWS.

3.4 It is the responsibility of the pilot or vehicle driver to exercise their best judgement regarding any action taken in response to a warning generated which conflicts with an ATC clearance. ATC must be informed of the warning generated and of their actions as soon as practicable.

3.5 Controllers must be trained and actively involved in the implementation process and operational evaluation of ARIWS to ensure the adjustment of calibration parameters and timing of the alerts are suitable for the area involved. The system must be tested for nuisance alerts.

Recommendations

4.1 It is recommended that:

IFATCA supports RWSL provided the following criteria are met:

  • The system will be used as a safety net.
  • It will operate automatically with no controller input required.
  • The system specifications are globally harmonized under ICAO guidance.
  • Potential confusion with other lighting systems is eliminated or mitigated.
  • Clearance to proceed will still be required.
  • All surface traffic will be required to comply with the system.
  • Comprehensive training is provided to all pilots, drivers and controllers.
  • False activations are kept to an absolute minimum.

If RWSL activations are displayed to the controller, the following criteria should be met:

  • The information should be efficiently incorporated into existing surveillance displays at the appropriate control positions.
  • Legal responsibilities are clearly and unambiguously defined.

Is amended to read:

IFATCA fully supports and encourages the future development of Autonomous Runway Incursion Warning Systems provided the following criteria are met:

  • The system will be used as a safety net.
  • False warnings are kept to an absolute minimum.
  • Due consideration should be given to the phraseology to be used when an ARIWS warning conflicts with the ATC clearance.
  • Comprehensive training is provided to all pilots, vehicle drivers and controllers.

If ARIWS activations are displayed to the controller, the following criteria should be met:

  • The information should be efficiently incorporated at the appropriate control positions.
  • Legal responsibilities are clearly and unambiguously defined.

And is included in the IFATCA Technical and Professional Manual.

References

  • ICAO PANS-ATM Doc 4444, Sixteenth Edition, November 2016
  • ICAO Annex 14, Aerodromes, Volume 1, Seventh Edition, November 2016
  • ICAO 9870, Manual on the Prevention of Runway Incursions, First Edition, 2007
  • FAA Runway Safety Report 2011-2012
  • FAA National Runway Safety Report 2013-2014
  • Eurocontrol Annual Safety Report 2015
  • FAA Runway Status Lights, Airport Engineering Division, Engineering Brief 64D
  • FAA Web site: http://faa.gov/air_traffic/publications
  • Civil Aviation Bureau of Japan, Runway Status Lights (RWSL) in Japan, July 2015
  • IFALPA Runway Status Lights (RWSL) 6 July 2016
  • Runway Incursions, TAIC Air Accident Investigator, 1 June 2008
  • FAA Runway Status Lights (RWSL) and Final Approach Runway Occupancy Signal (FAROS), MIT Lincoln Laboratory, 13 August 2008
  • FAA Runway Status Lights (RWSL) Human Factors Update and Results, MIT Lincoln Laboratory, 6 August 2006, August 8 2007
  • FAA Human Factors Assessment of Runway Status Lights (RWSL) and Final Approach Runway Occupancy Signal (FAROS), LAX, DFW and SAN, MIT Lincoln Laboratory, 6 November 2009
  • FAA Training for BOS Operational Evaluation of eFAROS, MIT Lincoln Laboratory 25 August 2014
  • http://rwsl.ll.mit.edu
  • https://www.faa.gov/news/fact_sheets/news_story.cfm?newsId=14895

Last Update: October 1, 2020  

December 25, 2019   906   Jean-Francois Lepage    2018    

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