45TH ANNUAL CONFERENCE, Kaohsiung, Taiwan, 27-31 March 2006WP No. 87Investigate Runway IncursionsPresented by PLC and TOC |
Introduction
1.1 The International Civil Aviation Organisation (ICAO) defines a Runway Incursion as:
“Any occurrence at an aerodrome involving the incorrect presence of an aircraft, vehicle or person on the protected area of a surface designated for the landing and take-off of aircraft.”
1.1.1 Because of a general lack of data that existed about runway safety occurrences, they were thought to be a relatively rare event. In 2001 a survey of occurrences was carried out in Europe and the statistics showed that pilots and air traffic controllers considered that runway incursions are one of the most serious safety issues in airport operations.
1.1.2 More recently there has been a steady increase in runway incursions due to improved reporting. It is noteworthy that the number of incursion reports has increased from states where a “Just Culture” open reporting system exists. This increase now reflects a more realistic record of the number of incursions taking place. Flight International reported that in 1999 there were 50 reports on potentially dangerous runway incidents in Europe; by 2004 this had risen to 530. A Transport Canada study showed that a 20% increase in traffic volume at an airport causes a 140% increase in runway incursion potential.
1.1.3 The possible consequence of a runway incursion affects the importance of the subject to both the ATC community and the aviation industry. The world’s worst aircraft accident was a runway incursion.
1.1.4 The factors causing runway incursions are many and varied: deficiencies in procedures; aerodrome layout; equipment deficiencies; human error by pilots, controllers and personnel on the aerodrome or a combination of all these. However, due to numerous reasons, usually economic, attention is often focussed on short-term solutions to the problems. It is simpler and often cheaper to pin the blame on “human factors” rather than look for the real underlying cause. This is especially true in cases where “aerodrome lay-out” is identified as a contributing factor where the true solution to the problem is often time consuming and very expensive.
1.1.5 The Transport Canada report, cited above, concluded that:
- the potential risk of a runway incursion increases more rapidly than traffic volume;
- many aerodrome improvement projects had resulted in a more complex aerodrome layout which, together with inadequate aerodrome design, marking and lighting, and a lack of standard taxi routes, had worsened the situation; and
- the effect of increased traffic volume, capacity enhancing procedures and aerodrome physical layouts may simultaneously exacerbate the runway incursion potential at certain aerodromes; and human error is the mechanism that translates potential occurrences, based on the factors above, into actual occurrences.
1.2 ICAO approach
1.2.1 A campaign of Regional ICAO Runway Safety Seminars was launched in October 2002 and has been concluded in September 2005.
1.2.2 Runway incursion reduction was closely examined by the 11th Air Navigation Conference (Montreal, September/October 2003). The conference agreed on the need for an effective global solution to the problem of runway incursion. Dissemination of standardised guidance material is considered to be essential for a worldwide improvement of the situation.
1.2.3 The 11th ANC also recommended that states take appropriate action to improve runway safety through implementation of runway incursion prevention programmes.
1.2.4 In consequence of this conference ICAO drafted the “Runway Incursion Prevention Manual”, which was also delivered to IFATCA for review. This manual aims to provide global standardisation and guidance essential for implementation of national or local runway safety programmes.
1.2.5 A standardised notification form and a standardised reporting form that support the ability to collect data across participating states is attached to the manual. Comprehensive global statistical analyses of data are essential to distinguish trends, causal factors and develop cost-effective risk reduction strategies.
1.2.6 The manual includes also a runway incursion severity categorisation (RISC) model produced by the United States’ Federal Aviation Administration (FAA). The drafting group claims that using this model will help provide feedback to determine if runway incursion events are becoming more or less severe over time.
1.3 European approach
1.3.1 In July 2001 a joint runway safety initiative was launched by the Group of Aerodrome Safety Regulators (GASR), the Joint Aviation Authorities (JAA), ICAO and Eurocontrol to investigate specific runway safety issues and to identify preventative actions. The task force, working group and steering committee that were subsequently formed to carry out this work comprised of representatives from a wide variety of professional organisations, including ANSPs and aircraft operators.
1.3.2 As a result of this action the “European Action Plan for the Prevention of Runway Incursions” (EAPPRI) was released in May 2003. An updated version 1.1 was subsequently released in August 2004. Currently work is ongoing to draft a more advanced sequel to the EAPPRI.
Discussion
The following analysis is based on the SHELL Model, globally recognized as a powerful system descriptor, that enable analysts to highlight issues in the single four fields of the aviation system, as well as their influence on the Human Factors.
2.1 S Software – (laws, regulations, procedures, etc.)
2.1.1 Procedures
2.1.1.1 The operation on the airport surface is insufficiently regulated. The lack of robust and mature operating procedures can lead to misunderstandings and confusion, which in turn leads to incidents. Ad hoc taxi routings, poor taxi guidance, the use of out of wind runways and multiple crossing runways all increase the chance of safety incidents. Low visibility procedures should be robust and strictly adhered to. Work in progress and non-standard taxi routings all increase the chances of incursions. The use of runways as taxiways and backtracking active runways should be kept to a minimum.
2.1.1.2 Procedures should be constantly reviewed and a proper safety management system should be in place. ICAO SARPS should be followed and a safety culture based on “just culture” fostered. The standardising of runway and taxiway movements is a way of helping to reduce runway incursions. The use of preferred and published taxi routes is the best option. “Best practice” should be followed as far as possible, e.g. if a clearance limit is beyond a runway it should include the instruction to “cross” or “hold short” of that runway. Departure instructions/clearances should be passed to aircraft before taxi clearance wherever possible. Conditional clearances should be issued with care to avoid misunderstanding.
2.1.1.3 The RISC scheme, proposed by FAA to ICAO for global adoption through the “Runway Incursion Prevention Manual”, may lead into neglecting of incidents, where only one aircraft/vehicle/person was involved and no traffic was in the vicinity. However, this is a matter of fate rather than an indicator for safety.
2.1.1.4 The FAA approach was already rejected by ICAO with the adoption of the present definition of runway incursion, opposing the one proposed by the USA, specifically with the purpose of taking into consideration any infringement of the protected area of a runway.
2.1.1.5 Recurrence of similar occurrences has often been found before an accident happens, that were not investigated because no interaction with other aircraft was caused. Once a safety net has failed an analysis is inevitable in order to avoid a similar event to occur in the future.
2.1.1.6 In order to gain complete and reliable data all runway incursions should be counted and investigated, no matter which severity category they belong to. This is crucial for identifying all possible risks at an aerodrome.
2.2 H Hardware – (Infrastructure, equipment, etc.)
2.2.1 Infrastructure – Aerodrome layout
2.2.1.1 Aerodrome layout is often the major cause of incursions. Aerodrome surface areas are developed with little regard to ergonomics, the main reason being cost.
2.2.1.2 Most aerodromes have areas liable to cause confusion and incidents, especially in Low Visibility Procedures (LVP) or at night. The European Action Plan calls these “hotspots.”
Figure 1 – Hotspots
2.2.2 Infrastructure – tower siting and obstructions to visibility
2.2.2.1 At some aerodromes the siting and design of the control tower, is less than adequate. There are blind spots caused by buildings, apron lighting, tower design and position. A badly sited tower can also cause communication blind spots, especially if low power standby radios are in use.
2.2.3 Infrastructure – markings and lighting
2.2.3.1 Non-standard or missing markings and signs on the manoeuvring area are often a factor in incidents. In some cases lack of maintenance has caused fading and damage or long term unserviceability. There are some aerodromes that operate in low visibility lacking stop-bars and basic runway guard lights.
2.2.3.2 The building of new aerodromes and the development of existing ones should be carried out in such a way as to avoid complex configurations, runway crossings and hotspots. Development should not impair the visibility from the control tower. Apron lighting should be masked to prevent glare. Blind spots to the controllers should be depicted on aerodrome charts. RTF blind spots should be covered by remote aerials, especially those near holding points. Known hotspots should be identified and published on charts.
2.2.4 Equipment
Technology can never substitute for adequate aerodrome design. However, in particular where so-called hotspots were identified suitable equipment should be provided to assist all contributing parties in avoiding runway incursions.
Aerodromes operating without basic Surface Movement Radar (SMR) are more likely to suffer serious incursions than those with. Modern systems such as Advanced Surface Movement Guidance and Control Systems (A-SMGCS) go a long way towards eliminating runway incursions.
As well as known devices like SMR, Multi-lateration (M-LAT) and Automatic Dependent Surveillance Broadcast (ADS-B) there are several technologies either in development or already operational (e.g. data link technologies, “Fog Eye” or night vision tools).
Today A-SMGCS facilities provide the most advanced technology for prevention of runway incursions in monitoring, control and guidance. A- SMGCS is not a system but a concept consisting of several components such as M-LAT, SMR and ADS-B. It covers all contributing parties (ATCOs, Pilots and drivers). Such systems can be a significant improvement for major airports.
Where M-LAT or SMR is installed it is important that all parts of the area of responsibility are covered and that such systems are augmented whenever necessary (e.g. expansion of the field, erection of new buildings that cause shaded areas).
A-SMGCS based systems may be too expensive for medium and small airfields. In particular medium sized aerodromes with seasonal traffic increase and mixed IFR/VFR traffic may need more affordable systems to prevent runway incursions.
2.2.4.1 Runway Incursion Monitoring and Conflict Alert System (RIMCAS)
Alerting systems for ATCOs are part of A-SMGCS level-2 concept. RIMCAS is a safety net focused on conflictions that affect runway traffic taking into account not only traffic on the runway itself but also in approach and line-up position. For such safety nets two levels of alerts are recommended in general:
- Stage-1 alert, also called “prediction step” to inform the ATCO about a potential hazard.
- Stage-2 alert, also called “alert step” to inform the controller about a critical situation where immediate action is required.
The final aim of RIMCAS is to cover all possible intruders no matter whether they are co-operative targets or not. However, until now no success has been made so far to establish satisfying parameters to cover non-cooperative targets as well (e.g. through SMR surveillance). RIMCAS parameters for co- operative targets, including aircraft and vehicles are about to be implemented currently as major A-SMGCS equipped aerodromes. The success of such a system depends mainly on suitable parameter settings, which have to be established for each aerodrome individually.
2.2.4.2 Stop bars
Operating stop-bars 24 hours a day may also reduce the risk of runway incursion. However not all aerodromes have successfully implemented 24H stop bar operation. Where aerodrome layout is not suitable for safe operation during normal visibility conditions this may also cause problems.
At aerodromes with positive experience with 24H stop bar operation there are only one kind of stop bar at each intersection, which is suitable for Cat 1 and Cat 2/3 operation. Parallel taxiways allow other aircraft to pass behind holding aircraft. The lighting panel is conveniently designed and located so that tower ATCOs can easily handle it.
On the other hand ATCOs on other aerodromes experienced serious problems with the recent implementation of 24H stop bar operation. The aerodrome layout may be designed to facilitate a continuous traffic flow only when CAT 1 holding points are used, which are not stop-bar equipped. When CAT 2/3 holding points are used, but are located so that they do block parallel taxiways and affect traffic flow in an unacceptable way an implementation might not be beneficial.
There are other aerodromes where stop bars are not switchable but pilots were instructed to cross them. IFALPA has a very clear position on that item. It says “Never cross a red bar”. This approach should be supported by IFATCA in order to gain support in creating an attitude towards never crossing red lights.
Stop bar crossing warnings should not be seen only as part of the very advanced A-SMGCS level-2 implementation only but as a tool on its own, because it can be implemented independently of M-LAT or SMR equipment.
2.3 E Environment
2.3.1 Environmental procedures are beginning to affect operations throughout aviation. There are some cases where environmental procedures have an impact on safety. Operating on out of wind runways for environmental reasons can cause difficulties especially when using reciprocal or cross runways.
2.3.2 There must be a safety assessment for such procedures.
2.4 L Liveware
2.4.1 There are a number of reasons why controllers might be unaware of a runway incursion. The most common cause of lack of awareness is workload. In a busy environment, the controller’s attention is divided between numbers of differing tasks. If there is a problem area or hotspot on the aerodrome the attention it receives will be diluted as the controller gets busier. The controller will “prioritise” his work tasks and there is also the risk that low priority tasks will be forgotten or missed. There is a tendency for controllers to reduce lookout as they get busier. They concentrate more on progress strips and the Aerodrome Traffic Monitor (ATM) and may miss something pertinent happening on the ground.
2.4.2 Errors can also be caused by low workload. It is often the case that an incident occurs during a quiet period, especially just after a busy spell.
2.4.3 Another reason for failing to detect an incursion is distraction, either internal or external. The source of the distraction can range from an incident on the aerodrome to visitors in the tower.
2.4.4 Deficiencies in communication and co-ordination are often prevalent in incidents. The breakdown of information exchange between parties is commonly cited as a factor in incidents. Incorrect phraseology, failure to obtain or monitor read-backs, language difficulties, inadequately trained operators, especially vehicular, are all deficiencies which can mislead or fail to alert a controller to an impending problem.
2.4.5 The lack of resources, especially human, plays a large part in incidents. Probably the most common resource issue is the lack of adequately trained staff. Combining air and ground positions in the tower, using qualified but inexperienced staff without adequate supervision and requiring staff to work in busy environments without adequate breaks are all examples of this. The use of poorly trained or inexperienced vehicle drivers can also increase the workload in the tower.
2.4.6 There are a number of possible solutions to the incursion problem; technology, training, airport improvements, procedures etc. Because the majority of operational errors result from a lack of awareness of an impending problem, the most obvious solution would be to improve surveillance monitoring of the manoeuvring area. The provision of A-SMGCS would provide the surveillance needed with problem detection.
2.4.7 Anyway proliferation of computer monitors and radar screens may lead to distraction and must be avoided. Data must be selected, redundancy avoided, information elaborated and made easily available and understandable by the ATCO, HMIs must be carefully designed and developed. IFATCA considers that displaying high mass of data on computer monitors or radar screens is not compliant with human factor principles.
2.4.8 The use of guidance material such as the EAPRI and the establishment of local runway safety teams will help to increase awareness of the problem and to improve education all round.
Conclusions
3.1 Runway incursion is a very complicated topic. The increase in incursions world-wide is a cause for concern. When a runway incursion occurs it is easy and cheap to blame the human in the system. Humans are fallible, especially in complex high workload systems such as aerodromes. The system in which they work should be designed in such a way that potential pitfalls are designed out as far as possible.
3.2 The ICAO “Runway Incursion Prevention Manual” and the EAPPRI include a couple of suggestions including best practices for pilots, air traffic controllers and vehicle drivers. These suggestions to operational people are useful as a first action to mitigate the situation. However core problems like inadequate aerodrome layout and insufficient equipment are hardly addressed. The aim should be that concerned ANSPs, aerodrome operators and Regulators should take responsibility as well to eliminate runway incursions.
3.3 The classification scheme of the severity of a runway incursion suggested by ICAO may result in incidents not being investigated, where only one aircraft/vehicle/person was involved and no traffic was in the vicinity. However, this is a matter of fate rather than an indicator for safety. Once a safety net has failed an analysis is inevitable in order to avoid a similar event to occur in the future. In order to gain complete and reliable data all runway incursions should be counted and investigated, no matter which severity category they belong to. This is crucial for identifying all possible risks at an aerodrome.
3.4 In development for the second EAPPRI IFATCA has demanded stronger statements on long-term actions related to infrastructure and for proposals to amend ICAO Annex accordingly.
3.5 Guidelines for aerodrome planning without taxiways crossing runways shall be the future aim to eliminate one of the main contributors to runway incursion. In particular when existing aerodromes are expanded strict guidelines to avoid construction of critical areas should become applicable.
3.6 Environment protection procedures at aerodromes must be reassessed, in order to consider the impact on runway operations and risk for runway incursion.
3.7 Wherever complex aerodrome layout, runway-crossing taxiways or known areas of danger (hot spots) exist adequate tools (e. g. SMR, A-SMGCS, stop bars, etc.) should be provided to increase controller, pilot and driver awareness.
3.8 IFATCA should support IFALPA policy and never instruct an aircraft to cross a red stop bar. The stop bar should be switched off rather than be crossed at red.
Recommendations
It is recommended that;
4.1 IFATCA Policy is:
“No procedures should be introduced that require the crossing of a stop bar at red.”
and is included in the IFATCA Manual on page 3 2 2 12 as paragraph 2.11 and that existing 2.11 be renumbered as 2.12.
References
Runway Incursions and Controller Critical Decision Making in Tower Operations – Donald O Weitzman 2001.
The Anatomy of Memory and Memory Lapses in Tower Operations – Donald O Weitzman 2001.
The Field Guide to Human Error Investigations – Sidney Decker 2001.
Methods of Preventing Runway Collisions – Transmit 2001.
Hindsight – Eurocontrol 2005.
Runway Safety – Antonio Travaglione 2005.
European Action Plan for the prevention of runway incursions.
Flight International.
ICAO Runway safety toolkit.
ICAO Runway Incursion Prevention Manual (Draft).
A Compendium of Technologies for the Prevention of Runway Incursions (NLR, v005 Draft).
Safety Analysis of Runway Incursions in Europe (Eurocontrol).
Operational Concept & Requirements for A-SMGCS Implementation Level II (Eurocontrol).
FAA, U.S Runway Safety Briefing (John Pallante, Oct. 2002).
Last Update: September 29, 2020