ATC Director, Mike Slack

In a recent industry consultation document, Airways Corporation has indicated it is exploring the option of using a Remote Aerodrome Air Traffic Service (i.e., a Digital Tower) to replace the ageing Auckland Tower. In the next two articles, the ATC director and the Technical Director discuss this technology, providing insights from both the controller and pilot perspective, including safety challenges, parameters for appropriate installation and dispelling myths about Digital Towers.

A hot topic around Air Navigation Service Providers for the last few years has been “Digital Towers”. Vendors tout them to “increase flexibility”, “increase capacity”, “reduce staffing”, “reduce costs” and “increase safety”. Unfortunately, these claims cannot be substantiated but tend to  be grasped by executive decision- makers to support significantly increased risk in adopting the new technology. Airways Corporation of New Zealand Ltd has been investigating this technology for a number of years now but cancelled that project during the COVID pandemic. In a recent industry consultation document, Airways is now proposing to use a Digital Tower as a contingency installation for whatever replaces the ageing Auckland Tower. To understand whether this decision is wise we must first fully understand what a Digital Tower is.

In the most basic form, a Digital Tower (sometimes referred to as a remote or synthetic tower) replaces an air traffic controller’s out-of-the- window tower view with cameras, communication lines (usually fibre optic) and video processing hardware/ software, and displays the view on multiple video screens. High-definition camera arrays on masts replace physical towers, whilst the tower cab is replaced by a digital tower centre that may contain multiple digital tower modules (being the individual controller’s workstation). A typical centre will have a large panoramic wall display of the aerodrome and surrounding airspace available to all controllers with individually tailored views available to each controller on his/her individual module. Pan/tilt/ zoom cameras replace a controller’s binoculars, sometimes with infrared (“see in the dark”) capabilities. Whilst to the untrained eye this technology looks pretty spectacular, it does have an associated complexity and risk that must be evaluated against any benefits that the technology may (or may not!) deliver.

A useful analogy is to consider motor vehicles. We are yet to see any manufacturer deliver a production car with cameras and screens completely replacing windscreens and windows. And yet most modern cars are delivered with reversing cameras and some with 360-degree parking cameras. Some have infrared “night vision” and parking assist lines superimposed over the camera view. These are appropriate uses of optical technologies to increase safety by enhancing a driver’s view of blind spots or providing alternative perspectives of difficult-to-see extremities of the vehicle and its surroundings. (It is noted that Auckland Tower currently utilises a number of cameras to view areas of the manoeuvring and movement area that aren’t directly visible from the tower, including parts of Taxiways Lima, Foxtrot, Charlie 5, Charlie 1, and the Heliport). Higher- specification cars also have adaptive cruise control, parking sensors, collision avoidance, emergency braking, self-driving ability, etc. But, as with Digital Towers, here is where one needs to make an important distinction between what is a digital view technology and what is merely technology – digital or otherwise.

Many of the claims listed in my opening paragraph result from technologies that are not specific to Digital Towers. London City airport is often cited as enjoying increased capacity since the introduction of its Digital Tower, when actually it was the second parallel taxiway that had the greatest impact on expediting departures – hardly a Digital Tower benefit. Technologies such as the following are all available in a traditional tower environment and will assist in increasing capacity, reducing controller workload, and improving safety:

• Advanced Surface Movements Guidance and Control Systems (A-SMGCS) that provide routing,  guidance and surveillance for the control of aircraft and vehicles in order to maintain a declared movement rate under all weather conditions. At its lowest level, it provides increased situational awareness to the controller but may also include many safety-net functions such as conflict probing, conflict resolution, aircraft/vehicle clearance compliance monitoring, intruder alert, etc

• Advanced electronic flight progress boards (ATRiCS) to enhance a controller’s situational awareness and streamline ground movement clearances and instructions, again with associated safety net functions

• Drone and Foreign Object Debris (FOD) detection, utilising specific radar installations or optical monitoring beyond the visual range of the controller

• Collaborative decision making (CDM) involving scheduling information being shared across multiple agencies (airlines, airport companies, air traffic control), enabling effective planning and reaction to the peaks and troughs of traffic movement

• Arrivals and departures management systems that manipulate slot times, “off blocks” times and allocated arrival times to even out those peaks and troughs

Similar systems are often installed along with the Digital Tower technologies, but the benefits
are often attributed directly to the Digital Tower rather than the individual systems that actually provide the benefit.

Whilst the purpose of this article is to dispel some of the myths around Digital Towers, it is important to understand that NZALPA is in favour of the technology where appropriate. When considering the “appropriateness” of a Digital Tower installation, the following factors need to be examined:

1. Airspace classification: the ability to adequately separate traffic using a purely surveillance-based solution without the ability to physically sight aircraft in order to use visual separation in the vicinity of an aerodrome. Civil Aviation Rules (CAR) Part 172 does not currently provide minimum standards for the safe and efficient use of surveillance technology for visual separation.

2. Traffic density and complexity: ensuring that either density or complexity is low. High- volume traffic should follow simple procedures – straight- in approaches (Instrument Landing System (ILS) or Required Navigation Performance (RNP)) and limited departure tracks allowing observation of approaching traffic through dedicated hi-def cameras. Where complexity increases (e.g. integration of curved approaches, integration of circuit traffic, integration of Visual Flight Rules (VFR) arrivals, transits, and departures with Instrument Flight Rules (IFR) arrivals and departures) then the volume of traffic needs to be low.

3. Location: many Digital Tower installations worldwide are, indeed, remote. Nordic controllers are on record as favouring digital towers because they aren’t required to live in remote locations to man a tower for only one or two movements a day. They can instead live in larger cities and be validated at multiple Remote Towers enabling them variety and avoiding boredom.

4. Terrain: the vicinity of the aerodrome should be free from significant terrain. Whilst currently available camera technology adequately detects airborne targets against plain backgrounds (blue sky, uniform cloud, snow), they appear less adept at detecting targets on complex backgrounds (rocks, bush, buildings, etc.).

5. Prevailing weather conditions: for similar reasons to (3), if visibility is often obscured by precipitation, cameras do not give an accurate representation of what the naked eye (both controller and pilot) can see. Cameras tend to enhance low-light conditions (by boosting ISO or opening the camera iris) which may give the controller an unrealistic expectation of what an airborne pilot may be able to see.

In addition, the project to install a Digital Tower should:

• be adequately resourced using local and current controllers and technicians as subject matter experts throughout the entire project (in line with international best practices), to ensure staff buy-in and project acceptance;

• have realistic timeframes for development, training, installation, testing, and parallel running (if required) before cutting over to the purely digital solution;

• have regulatory approval.

In light of the above, it is NZALPA’s opinion that Auckland Airport falls short of the “appropriateness test” for even a Digital Contingency Tower.

It would appear more appropriate that a digital solution be trialled, introduced, and validated at another location before being considered for New Zealand’s busiest and primary aviation port for international arrivals and departures.

It would also seem more appropriate to introduce a digital service at a location where no service is currently offered and which meets the criteria listed above. Introducing a trial Digital Tower at a location that currently has regular passenger transport services but no Air Traffic Service (e.g. Whangarei or Timaru) could not only validate the technology in New Zealand but also increase safety for our pilot members, the travelling public, and those they fly over. Instead, it appears that Airways may be positioning itself to be forced down the Digital Tower path at Auckland due to tight timelines and the perceived higher cost of building a conventional “bricks and mortar” solution.