Many articles start with the claim that “drones have many positive use cases and open new perspectives” but when it comes to integration at airports, this vision rapidly hits a reality-check. Airports are like a honeypot for drones: this is where the most profitable use cases exist. Air taxi passenger transport directly from the apron to city centres is the holy grail of Advanced Air Mobility (AAM) and drone delivery from airport cargo facilities would also be hugely beneficial.

Stakeholders in manned aviation can see the potential but also the threats posed by unmanned aircraft systems (UAS), and managing those threats is challenging at technological, operational and organisational levels. This article looks at those challenges specifically from an air traffic management and airport perspective.

A three-pronged approach

Integrating unmanned traffic and managing the related threats requires three capabilities:

  •  Drone detection – knowing where drones are and whether they are cooperative or not
  •  Unmanned traffic management (UTM) – matching drones with approved missions and checking whether or not detected drones are operating as planned
  •  Counter-UAS (C-UAS) – neutralising drones which are not flying according to their mission plan

The complexity of drone detection depends on which threats shall be identified. A pilot operating an off-the-shelf drone using standard frequencies and protocols is easy to locate using radio frequency (RF) detectors. Drones using WiFi can be a specific challenge at airports because of strong networks existing in terminal buildings. Detecting malevolent drones using non-standard RF channels or flying fully autonomously is a different task, which requires radar technology. The rate of false detection requires a human in the loop to validate detections and evaluate threat levels, and this comes at high costs.

Many sensor technologies on the market are not suitable for use at airports. The acoustic sensors’ range is typically far too limited, and the environment is too noisy anyway. Drone detection radars with a range below 4 kilometres (the typical length of a runway) also pose difficulties as getting full coverage requires many individual radars. Optical systems can be used, and they often cope well with the multiple moving objects around airports. However, in many European countries, the regulatory framework makes it hard to obtain authorisation to point a camera towards staff working on the apron.

Once drones are detected, the UTM system must match them to mission plans, identifying which ones are allowed, which ones deviate from their plan and which ones can’t be matched with a plan at all. An important feature of UTM systems for flights close to airports is the integration with air traffic management (ATM) systems used by air traffic controllers (ATCO). This is required for flight approval and for communication with the drone operators during the flight, if required. The level of certification required by ATM systems is high and makes integration a complex task.

The use of C-UAS technologies at airports presents additional challenges compared to other locations. Most physical methods can’t be used. Shooting laser beams around people working on the tarmac or passengers in terminals is not really an option. A drone falling from the sky onto an aircraft is also not acceptable. At airports, non-destructive mitigation methods are generally preferred. Examples include protocol take-over techniques that guide a drone to a safe landing area, or capture systems using interceptor drones.

GNSS jamming is often used by C-UAS systems and this creates specific challenges at airports too. Aircraft and ground vehicles use GPS for guidance and location. Many airport and ATM systems also use GPS as a source for time reference, making widespread use of jamming more problematic.

The organisational sandwich

Another factor to consider when deploying C-UAS systems at airports, beyond the technical complexity, is the operational and regulatory sandwich. Typically, three organisations are involved: the airport operator, the air navigation services provider (ANSP) and one or more law enforcement agencies.

In a nutshell, the airport operator oversees the terminals and aprons, the ANSP is in charge of the main taxiways, runways and air traffic in the vicinity, and the police are responsible for law enforcement.

Crucially, airport operators or ANSPs have no legal basis to operate C-UAS systems. Only law enforcement forces can legally seize, damage or destroy a rogue drone which still is someone’s property. An efficient integration and defence system therefore requires quick communication and response. To add one more layer to this sandwich, different law enforcement agencies are usually responsible for the airside and landside parts of the airport.

In Germany for example, everything happening within the airport fence is under the responsibility of the federal police and an unauthorised drone flying over an airport is a federal issue. However, if the pilot is outside the fence, it falls under the responsibility of the local state police.

ANSPs, airport operators and law enforcement agencies also focus on other areas and have different views on drone threats. Airports are only concerned about what happens inside the fence. ANSPs also consider the airspace nearby and often at multiple airports. From a police perspective, airports are just one more entry in a long list of critical assets requiring protection. This implies different time horizons and working methods, which must be harmonised.

In this complex context, having relationships with the right decision makers is as important as offering a system with the required level of performance.

What have we learned?

Drone threats affecting airports gained a sudden visibility between 19 and 21 December 2018, when hundreds of flights were cancelled at Gatwick Airport in the UK. Seven years later, the culprits remain unidentified. The number of drone sightings at airports increases year after year and temporary airspace closures happen on a regular basis.

There is no standard, perfect solution yet. Some airports and ANSPs have installed drone detection systems in an attempt to ensure safety by responding when drones are detected. Without counter-measures, detection is only half the solution. The only possible reaction is to inform aircraft pilots about the threat and potentially close the airspace around the airport for a while. Detecting a threat is possible, but the complexity lies in detecting the end of such an event, especially if the operator can’t be identified.

It is not possible to predict drone intrusions and it is also not possible to know how long the traffic will be disrupted, making such cases even more complex to handle for airlines, airports and ANSPs.

Geofencing and remote ID are a good start

Some measures make it possible to protect airports against threats in a proactive manner, assuming that drone operators comply. States publish no-fly-zones and drone manufacturers can implement flight control software preventing drones from entering such no-fly-zones. This approach has limitations too: drone operators can get an authorisation to fly at airports and need a way to bypass such a mechanism. Obtaining the no-fly-zones is not easy either. There are different data formats and each country has its own rules for defining no-fly-zones.

Remote ID is also a step in the right direction. With a proper receiver, airport operators and ANSPs can know where cooperative drones are and make better decisions. As for RF detection systems, this works only with collaborative drones equipped with a transmitter. It also makes a-posteriori research and identification of the pilot easier.

Remote ID is almost standard now but with a range of 0.5 to 5km, it requires the installation of a network of antennas. That range limitation implies that it cannot be used aboard manned aircraft directly. The time left for cockpit crews to react would be too short, therefore it becomes one more input in the ATM system, enabling ATCOs to take appropriate measures.

Geofencing and remote ID are both good measures which can prevent drone intrusions at airports, helping well prepared pilots to avoid mistakes. However, they are of no use when it comes to preventing threats by malevolent operators.

Integration in progress

Airports and ANSPs around the world are working on ways to integrate drones and AAM based on the three capabilities of drone detection systems, UTM systems and C-UAS. Doing so in a safe way is not easy and it will take time. Aviation has significant safety management systems targeting objectives in the 99.9% safety range and cycles are measured in years, not in months or weeks. The organisational complexity, the legal implications and, in some cases, countries with nationwide plans add extra layers of concern that must be addressed. Success will depend not only on technological performance, but also on the ability to integrate multiple stakeholders, regulatory frameworks and operational procedures.

Technology progresses and there is no first-principle reason for which drones could not fly at airports in the future but this will not happen in a “move quick and break things” way.