Remote Tower Services

CONCEPT

AREAS OF CONCERN

ECA POSTION

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Remote Tower Services (RTS) is a new concept where the air traffic service at an airport is performed remotely, i.e. somewhere else than in the local control tower. Over the coming decade, this concept is likely to develop further, to gain maturity, and to gradually spread within the industry. This paper outlines the European pilots’ perspective and position on RTS. ECA accepts the development of RTS that meet an equivalent level of safety or increase the safety of flight operations subject to a number of conditions, which are explained below.

CONCEPT

The concept of Remote Tower Services (RTS), also referred to as Remote and Virtual Tower, is being studied in the context of the Single European Sky Air Traffic Management Research Programme (SESAR) in Europe, as well as in other countries such as the United States (“Blended Airspace” in NextGen) and Australia, while it is already operational to a certain service level in countries such as Japan.
 
ICAO is assessing the concept with regard to the need to update ICAO regulations and it is included in ASBU module B1-81. Work on new/updated provisions is expected to start not before 2016 and might take place in the ATMOPS panel, pending agreement by the Air Navigation Commission.
 
Modes of Operation
For many years, visual observation of traffic in the pattern and on ground from a local air traffic control tower was the single means of observing and separating traffic at airports worldwide. With the appearance of radar and new surveillance systems for airborne and ground movements, as well as an ever-increasing size of airports, camera and ground-surveillance systems have been installed in accordance with ICAO DOC 4444. Nevertheless, ICAO procedures still regard visual observation has the method of choice whenever possible.
 
As the concept of Remote Tower Services was being researched, it became clear that it would differ fundamentally from traditional modes of tower operation. Cameras and sensors could be placed anywhere on the field, and not just in one location, and air traffic controllers would be presented a virtual picture of reality, enhanced by a number of gadgets. While some manufacturers favour a rather real presentation of the outside world, others would present only infrared images to controllers. Therefore a distinction has to be made between Remote Tower Services displaying a real-life picture that is possibly enhanced by some gadgets and Virtual Towers that partially or completely display an artificial picture.
 
In the concept as outlined by SESAR, radar coverage and radar separation are vital. This means that new separation methods might be necessary. Airspace design might have to be reviewed to take the necessity of transponder carriage into account. Also, there is neither provision on charting requirements nor flight procedures for RTS.
 
As the current ICAO provisions are clearly out-dated in regard to RTS, there is an urgent need for globally accepted SARPS, common definitions and procedures.
 
Common standards and recommended practices, definitions and procedures shall be developed covering flight procedures, separation standards and minimum requirements of systems and sensors among others.
 
  • Single Remote Tower
› One air traffic controller is responsible for operations at one airport at a time. Yet, he/she might hold multiple ratings to control different airports, one after the other.
  • Multiple Remote Tower
› One air traffic controller is responsible for operations at more than one airport at the same time. This requires multiple ratings for each controller and careful staffing schedules. This concept is completely new compared to current operations.
  • Contingency Tower

› A contingency facility to be used when an airport tower is unserviceable for a short period of time (e.g. fire, technical failure). Remote Tower operation will then assure at least a basic level of service.

Remote Towers can be operated from a Remote Tower Centre (RTC) that can be located anywhere, but is usually planned to be at a reasonable distance from all the airports to be controlled in order to reduce latency of signals and increase technical reliability.

Benefits

While the conventional concept of operating an ATC tower is proven to be safe in current day-to-day operations, the deployment of RTS does have potential safety benefits.

Smaller airfields currently only receiving Aerodrome Flight Information Service (AFIS) might be upgraded to fully controlled airfields. Other airports facing cutbacks due to low number of flight movements might still be able to provide ATS services, even if only for a limited time per day. The same is true for areas where destroyed infrastructure (e.g. after a fire) or an unstable safety situation (e.g. war zones) requires the quick set-up and operation of a control facility.

Modern RTS concepts include a number of tracking features. Aircraft position can be followed easily with a label attached next to the tracked target on the controller’s out-the-window screen, giving information on the call sign, altitude, and distance among others. Ground staff and vehicles can be tracked, as well as birds and other animals or human intruders. Runway incursions can be automatically detected.

Whilst increasing the alertness of the controller, care has to be taken as not to overload the controller with too much information, leading to a situation where controllers develop a certain alarm-fatigue due to constant inputs. Task coordination needs to be carefully assessed, as controllers will probably spend more time “head-down”, concentrating on managing the systems (e.g. electronic flight strips) instead of actually watching movements.
 
The opposite may also be true at airports with very few movements, when performance of controllers and stimulation levels increase due to optimal workload distribution (Yerkes-Dodson law).
 
The increased possibilities of presenting multiple data inputs are likely to lead to enhanced visual reproduction, especially during twilight and night, as well as bad weather. The use of infrared cameras allows for weather assessment and target detection even during complete darkness.
 
The idea of a remote contingency tower providing at least some level of service or the same service at a decreased movement rate is safety-wise beneficial compared to having to close an airport completely.
 
Having multiple controllers present in the same RTC might also lead to better coordination between ATS units.
 

 

AREAS OF CONCERN

 
Contingency measures at conventional towers include the use of handheld transmitters or light-guns, as well as signal rockets. Should the tower building become unusable, contingency operations could easily continue from a nearby location with the above-mentioned means, at least at small and medium-sized airports. This is different for RTS, where no controller is located at the airport itself. While data transmissions can be backed-up by a second system or other measures, the impact of hardware failures might be fatal for operations. Cases have been reported, where bugs sat on the camera blocking the view. The outage of a camera or a display at the controller working position (CWP) covering essential parts of the airport area or traffic circuit are likely to happen at some stage.
 
Adequate contingency procedures in case of hardware malfunctions (e.g. camera, controller working positions) and system downgrades shall be in place.
 
Cyber-security has become an increasing source of concern within the aviation community and remote tower operations have the potential to increase the vulnerabilities of the system given the very nature of the concept. Precautionary measures and contingency procedures shall be established to prevent an attack, and to minimise its consequences. ANSPs and aircraft operators shall establish a mandatory reporting system for cyber-related occurrences, and cyber security shall become an essential part of their security management system.
 
All aircraft systems, on-ground systems/networks and data transfers between aircraft and ground shall be protected from hacking, data manipulation and viruses.
 
Traffic separation, especially for VFR flights is usually based on visual observation in conventional towers. Displays at RTS CWPs do not allow for visual evaluation of airborne aircraft positions. This is why the usage or radar data appears to be essential for RTS operation. This in turn might necessitate the need for transponder carriage by aircraft intending to use that airport. It has to be evaluated how far adjustments to current airspace design and specifications are necessary, e.g. mandating the use of transponders for all aircraft. General aviation aircraft are likely to be affected by revised rules.
 
From a pilot’s point of view there should be no changes to current operations. Yet, it might be necessary to revise communication procedures and charting requirements. Especially in a Multiple RTS environment, the re-transmit function that allows users to listen to radiotelephony on multiple frequencies might be a feature to ensure safe operations. Mentioning the airport’s name in clearance (e.g. cleared to land runway 20 Dresden) might be another option of avoiding misunderstandings.
 
Communication procedures and regulations for airspace design around RTS airports (e.g. transponder mandatory zones) shall be evaluated and changed where necessary.
 
Coordination between airspace users and ANSPs will have to be increased to accommodate all aircraft movements, be they planned or unplanned. As in today’s ATC environment, staff shortages may happen. While this is usually a problem in the en-route part of flights today, availability of tower controllers might be the limiting factor in RTS operations, with not enough staff available to cater for all flights. Unexpected flights such as VFR traffic or flights that have to land due to emergencies or diversions might push the remotely controlled tower even further beyond capacity. While slot allocations or per-prior-request-only operations might counteract such problems, there is a clear shift of responsibility for safety from ANSPs to pilots and operators. It is not acceptable that unavailability of tower controllers leads to hazardous situations.
 
Holding patterns, diversions or hazardous situations due to ATC staff shortages shall be avoided.
 
It is air traffic controllers who nowadays often do weather assessment and the evaluation of the runway surfaces status. In case of RTS operations these would have to be performed by dedicated staff or adequate systems and sensors. It is also questionable how far weather assessment can be done by RTS controllers when being presented with a compressed or limited view of the airport. The quality of reports must not be lower than in today’s environment.
 
Ensure that real-time weather data and runway surface status is accurately assessed and transmitted to pilots.
 
The concept of RTS fundamentally changes the working environment of tower controllers and different procedures and techniques have to be used. This is especially true for Multiple Tower operations. While research has shown that the concept can generally work, not all implications on daily operations are yet fully understood. It would be advisable to first evaluate experience of prolonged live Single RTS, before establishing Multiple RTS. There are currently no long-time studies on how human performance is affected in Remote Tower operations and current results indicate that there are certain limitations for humans with regards to working in an RTS environment.
 
Nowadays only few air traffic controllers hold ratings for more than one tower and it is highly unlikely that these would be exercised in a single shift. In Multiple RTS controllers might be required to work at airports with completely different or very similar layouts and weather patterns. Both can lead to a fragmented situational awareness, causing misunderstandings, mix-ups and other working errors, thus having the potential to significantly decrease the safety of operations. Competency of controllers to evaluate the situation at a specific airport might also decrease with increased workload and numerous distractions. Studies have shown that head-down time increases in a Multiple RTS environment. Other factors like usage of a common frequency or aligning procedures and airport markings have not been studied yet.
 
ECA does not support the implementation of Multiple RTS, until sufficient experience with Single RTS has been gained and until human factors and technical implications have been thoroughly researched and are adequately mitigated to ensure safe ATC operations.
 
The technology of RTS will afford providers the ability to offer RTS across state borders. This will open opportunities for providers to seek a different regulatory environment to that of the state where the aerodrome is based. In a competitive market, this risks to open the door to ‘regulatory forum shopping’ where providers may seek a forum with more lenient and commercially expedient regulatory (including social and taxation) regimes. This could leave some RTS providers with less oversight and regulation than others, distort the market between RTS and normal on-site staffed aerodromes, and expose ATS staff to the risk of casualised employment relationships with the attendant possible degradation in safety culture.
 
ECA does not support the implementation of cross-border RTS service, until a legal EU framework is in place to effectively prevent regulatory forum shopping and market distortion.
 
EUROPEAN COCKPIT ASSOCIATION POSITION
 
Taking into consideration all relevant factors towards the establishment and operation of Remote Tower Services (RTS), the European Cockpit Association's position to RTS is:
 
ECA accepts the development of RTS that meet an equivalent level of safety or increase the safety of flight operations subject to a number of conditions:
 
  • Common standards and recommended practices, definitions and procedures are developed covering flight procedures, separation standards and minimum requirements of systems and sensors among others.
  • Risks in regards to RTS are being studied and solved. These including the following aspects (in no particular order):
› Adequate contingency procedures in case of hardware malfunctions (e.g. cameras, controller working positions) and system downgrades shall be in place;
› All aircraft systems, on-ground systems/networks and data transfers between aircraft and ground shall be protected from hacking, data manipulation and viruses.
› Communication procedures and regulations for airspace design around RTS airports (e.g. transponder mandatory zones) shall be evaluated and changed where necessary;
› Avoiding holding patterns, diversions or hazardous situations due to ATC staff shortages;
› Ensuring that real-time weather data and runway surface status is accurately assessed and transmitted to pilots;
 

ECA does not support the implementation of Multiple RTS until sufficient experience with Single RTS has been gained and until human factors and technical implications have been thoroughly researched and are adequately mitigated to ensure safe ATC operations.

ECA does not support the implementation of cross-border RTS service, until a legal EU framework is in place to effectively prevent regulatory forum shopping and market distortion.

 

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