44TH ANNUAL CONFERENCE, Melbourne, Australia, 17-22 April 2005
WP No. 93
Investigate Remote Aerodrome Control Concepts
Presented by TOC
1.1. This topic was raised last year in Hong Kong.
1.2. The current situation, in particular the growing low cost sector and the high fuel price, forces national and supranational Air Navigation Service Providers (ANSP) to reduce their costs and increase capacity. At the same time, safety shall be maintained or even improved.
1.3. This topic was added to the TOC work programme 2004/2005 in order to investigate in principle the legality of this course of action.
1.4. The Remote Aerodrome Control Concept that will be addressed by this paper is based on the limited information available from the ANSP that is proposing this action.
2.1. The Concept
2.1.1. The following section provides an introduction to an ANSP’s idea of cost reduction. After implementation of single man operation on several control towers at night the ANSP plans to completely abandon the tower at one airport and to provide its aerodrome control service from a tower a hundred kilometres away. That tower controller will provide, in addition to his original task of controlling aerodrome traffic at their own airport, an aerodrome control service for the remote airport, including control of the manoeuvring area. The tower controller will switch runway stop bars on for the remote airport, clear aircraft for taxi, line-up, take off and landing and will base on pilots position reports, in particular “runway vacated” reports, only. The tower controller will not be supported by SMR, Multilateration, ADS-B or any other advanced surveillance system. This service will be provided in a mixed IFR/VFR environment on an international airport giving the pilot the impression of real aerodrome control service based on visual observation. To make it clear, it is not a concept of “virtual tower control” supported by sophisticated systems like A-SMGCS or ADS-B we speak about. It is all about aerodrome control provided from a remote position in order to reduce costs.
2.1.2. The target date for implementation for this new “service”, 1st of July 2004, could not be met. One of the reasons for the delay is a problem with the switching of stop bars from a position more than 100km away. However, implementation is still the aim. Since the ANSP is obviously not interested in making this idea public before implementation, it is hard to gather information on the details of the planned procedures. ATCOs are kept uninformed as well as customers – a point that is unacceptable. There is no information available about any safety case performed. From earlier safety assessments that have been done in regard to other reduction of service, like single man operation, it seems that results were defined in advance. An argument often heard from the supporters of this new idea is that during low visibility operation the tower controller is not able to maintain visual contact, therefore it cannot be a problem for a tower controller who is not on site – a cynical statement to ATCOs and pilots.
2.1.3. One IFATCA Member Association (MA) and Union took a very strong stand on this issue:
“According to this MA such a plan is contradictory to all principles of ATS. It is also contradictory to multiple international and national recommendations, regulations and laws.” (magazine of MA)
2.2.1. Overview of relevant definitions in ICAO Doc 4444 PANS-ATM:
|Aerodrome control tower: A unit established to provide air traffic control service to aerodrome traffic.
Controlled aerodrome: An aerodrome at which air traffic control service is provided to aerodrome traffic
Note: The term “controlled aerodrome” indicates that air traffic control service is provided to aerodrome traffic but does not necessarily imply that a control zone exists.
Aerodrome control service: Air traffic control service for aerodrome traffic.
Aerodrome traffic: All traffic on the manoeuvring area of an aerodrome and all aircraft flying in the vicinity of an aerodrome. Note: An aircraft is in the vicinity of an aerodrome when it is in, entering or leaving an aerodrome traffic circuit.
2.2.2. In the following paragraphs containing statements concerning the discussed item are quoted and commented when applicable:
|4.3.1 Aerodrome control service
Aerodrome control service shall be provided by an aerodrome control tower.
This statement is very clear and leaves no space for interpretation.
|22.214.171.124 Aerodrome controllers shall maintain a continuous watch on all flight operations on and in the vicinity of an aerodrome as well as vehicles and personnel on the manoeuvring area. Watch shall be maintained by visual observation, augmented in low visibility conditions by radar when available.
Traffic shall be controlled in accordance with the procedures set forth herein and all applicable traffic rules specified by the appropriate ATS authority. If there are other aerodromes within the control zone, traffic at all aerodromes within such a zone shall be coordinated so that traffic circuits do not conflict.
This paragraph gives a very clear idea of the tasks of a tower controller, tasks that cannot be performed from a position other than the control tower (which has to be located – see above – at the aerodrome). Still there is no space for interpretation.
|126.96.36.199. Obstructed runway In the event the aerodrome controller observes, after a take-off clearance or a landing clearance has been issued, any obstruction on the runway likely to impair the safety of an aircraft taking off or landing, such as runway incursion by an aircraft or vehicle, or animals or flock of birds on the runway, appropriate action shall be taken as follows:
a) in all cases inform the aircraft concerned of the obstruction and its location on the runway
b) cancel the take-off clearance for an aircraft which has not started to roll
c) instruct a landing aircraft to go around
Observation is the main tool to prevent incidents or accidents and maintain a safe and expeditious traffic flow, a service, which can hardly be provided from a remote position.
|188.8.131.52.1 Whenever an abnormal configuration or condition of an aircraft, including conditions such as landing gear not extended, or unusual smoke emissions from any part of the aircraft, is observed by or reported to the aerodrome controller, the aircraft concerned shall be advised without delay.|
|7.4.4 When a not previously notified condition pertaining to the safe use by aircraft of the manoeuvring area is reported to or observed by the controller, the appropriate aerodrome authority shall be informed and operations on that part of the manoeuvring area terminated until otherwise advised by the appropriate aerodrome authority.|
|184.108.40.206.1 SMR should be used to augment visual observation of traffic on the manoeuvring area and to provide surveillance of traffic of the manoeuvring area which cannot be observed visually.|
Based on these three paragraphs, it is concluded that observation is a crucial thing.
2.3.1. IFATCA Manual 2003, Page 3224, Para 2.4
|Provision of ATS at Aerodromes
Not all aerodromes have the volume or type of traffic which necessitate the provision of Air Traffic Control Service, at some aerodrome it may suffice merely to provide Aerodrome Flight Information Service. IFATCA believes that;
“Air Traffic Control service must be provided at aerodromes that:
a) serve commercial air transport operations, or
b) have published IFR approach, departure or holding procedures
At aerodromes at which Air Traffic Control is provided the appropriate grade of controlled airspace should be provided.
Where the above factors do not apply Aerodrome Flight Information Service (AFIS) may be provided, but shall never be used as a substitute for Air Traffic Control Service. Where AFIS is in operation the limitation of the service shall be added to the station RTF call sign.”
2.3.2. IFATCA Manual 2003, Page 3225, Para 2.5
|Responsibility and Function of Aerodrome Controllers with Regard to Surface Movement
The task of apron control is not solely the responsibility of ATC, therefore all staff involved in the provision of this service should be trained to the appropriate standard.
It is important that the siting of control towers, the markings of taxiways, the use of visual aids and the introduction of future technology should have a minimal impact on operations.
Developments in new Advanced Surface Movement Guidance and Control Systems and their introduction should be an integral part of low visibility operations.
IFATCA Policy is:
“A control tower must afford an aerodrome controller with direct visual observation of the manoeuvring area. The use of CCTV equipment is not acceptable as a substitute for direct visual observation.
Where a separate apron management service is established, personnel engaged in issuing specific ground clearances, instruction and clearance delivery should be trained and licensed to exercise these functions.
Surface Movement Surveillance Systems should be installed at all airfields where low visibility operations take place and their operation should be mandatory while these operations are in progress.
Safeguards should be imposed to prohibit the development of any structure that would impede the direct visual observation from the tower.”
The EUROCONTROL Airport Operation Strategy documents (Volume 1 and 2) are focused on major airports and therefore do not contain anything about remote tower concepts. However, the concerned concept of remote tower control may be considered to be contradictive to the philosophy of a gate-to-gate environment.
2.5. Visual observation
Why is visual observation so important for aerodrome control?
Under normal conditions:
First of all, it is simply the observation of all traffic and the compliance with the clearances issued. There is no place in aviation where aircraft get closer. Beside aircraft several other parties like vehicles and pedestrians are involved. Such a traffic mix in such a limited area cannot be observed and controlled with the help of technical devices like radar or SMR. However in this scenario it is not even intended to support the ATCO with such devices. In particular mixed traffic (IFR/VFR) can become a hazard when the ATCO is not able to observe the correct application of procedures and clearances.
Under special circumstances:
The tower controller is the first one outside the aircraft to see what is wrong. The tower controller is the first one to see the aircraft with a broken gear, a flat tire or smoking engine. He can see obstructions or unauthorised movements on the manoeuvring area before anybody else can see. The most critical phases of flight are take-off and landing. According to ICAO Circular Accident/Incident Annual Report the majority of such events happen during take-off and landing. Pilots operating at controlled aerodromes are expecting full aerodrome control service, but are not receiving it.
2.6. Low visibility operation and procedures
As already mentioned above, an argument used by supporters of the “remote tower concept” is that, during low visibility operation, the tower controller is not able to maintain visual contact, therefore it cannot be a problem for a tower controller who is not on site to observe the situation. However, even when all possible safety related procedures for low visibility conditions are applied, it is still more risky than operation under normal visibility, simply because the most important tool of a tower ATCO – visual observation – cannot be provided. To intentionally operate under such conditions is unacceptable.
Under low visibility, a main contributor in TWR traffic – VFR flights – are banned. If this is not the case during “remote tower control” the responsible ATCO has no possibility to observe the compliance of clearances issued. The observation is absolutely necessary, not only because tower control is based on the “see and be seen” principle but also non-compliance or misinterpretation of traffic is a widely experienced problem tower ATCOs are faced with daily, problems which can be solved easily by visual detection in due time. This is impossible to obtain from a position other than the control tower.
2.7. Weather observation
According to ICAO standard, met-reports are regularly issued every 30 minutes; special met-reports are issued when the situation makes it necessary. Still a met-report containing the standard information does not give a complete idea of the situation on the field itself. In particular under marginal conditions, pilots often ask for more detailed information about occurrence of clouds, visibility in a certain direction or location of fog patches. This is a service supporting safety, which can certainly not be provided from a remote position.
2.8. Light signals/loss of communication
In case of loss of communication a pilot may expect to be supported from an aerodrome control tower by the use of light guns or signals indicating landing is approved or not. Aircraft can also indicate if they have understood. This mainly applies for VFR traffic but should be considered as important in an mixed environment with aerodrome control service. This is one more example where reduction of costs means decrease of safety.
2.9. Controller workload
Having in mind the entire picture of the situation on a remote aerodrome while providing control based on visual observation on the other aerodrome may result in problems concerning controller workload. One controller providing aerodrome control service at two or more aerodromes is unsafe. It may cause a potential risk for confusion or misinterpretation of reports and messages or traffic situations.
3.1. In Europe and North America there is currently no use of remote aerodrome control. According to international regulations as well as national laws this is considered to be illegal.
3.2 The idea of a “Remote Tower Concept” as raised by this one ANSP is unique and neither follows ICAO provisions nor any concept found in Europe or North America.
3.3 If this concept for “remote tower” control is implemented, a decrease of safety may occur and a decrease in quality of service will occur. This clearly is unacceptable to IFATCA.
3.4 Before any such concept can be considered for implementation, a safety assessment must be made available to stakeholders, such as controllers, pilots and aerodrome operators.
3.5 Pilots operating at controlled aerodromes should always receive full aerodrome control service.
3.6 This concept is not supported by ICAO rules and regulations.
3.7 Information to and cooperation with IFALPA and the relevant IFALPA member associations is considered to be helpful.
It is recommended that;
4.1. This paper be accepted as information material.
Last Update: September 29, 2020