Article

A practical approach to civil-military interoperability

Mariana Anguelova

The Operational Air Traffic (OAT) harmonisation and OAT/General Air Traffic (GAT) interface is an essential enabler for military mobility and cross-border operations in European airspace. Mariana Anguelova, Stakeholder Relations Manager and Senior Civil-Military ATM Cooperation Expert at EUROCONTROL explains why EUROCONTROL’s Civil-Military Cooperation (CMC) Division has a vital role to play in this.

The use of airspace faces a lot of challenges. Civil and military airspace users have to adapt to a new security environment but also prioritise safety to all operations. Airspace becomes congested with more demands by new actors entering the system with their specific requirements and significantly different performance, such as uncrewed aircraft systems (UAS), drones, urban air mobility, high altitude operations (HAO) including space launches, and newgeneration military aircraft requiring a larger volume of airspace to operate, train and exercise.

As air traffic management (ATM) and the European civil and military airspace user needs evolve, it is vital that all stakeholders are engaged in finding the best solutions to accommodate all requirements in the most performant manner possible to ensure a resilient, adaptable and environmentally sustainable aviation in Europe.

One of these challenges is related to a harmonised integration of the operational air traffic (OAT) into the European ATM ecosystem and the development of operational and technical interfaces with the general air traffic (GAT), for the benefit of both civil and military airspace users.

Background

The Single European Sky (SES) addresses the needs of all airspace users, including the military. An efficient and coordinated integration of military flights into ATM network operations brings benefits to the overall ATM network performance.

However, SES Regulations govern only the provision of services for aircraft operating as GAT – they do not define any specific requirements for the provision of services for military airspace users, especially when flying as OAT.

The most applied definitions for flights which are conducted in accordance with the rules of GAT and OAT are:

  • GAT encompasses all flights conducted in accordance with the rules and procedures of ICAO. These may include military flights for which ICAO rules satisfy their operational requirements.
  • OAT is an agreed term applied in Europe to all flights which do not comply with the provisions stated for GAT and for which rules and procedures have been specified by appropriate national authorities.

The ATM system is designed to accommodate civil instrument flight rules (IFR) traffic and military IFR traffic capable of/choosing to comply with the procedures established for civil IFR traffic.

The current definition of OAT could be misleading, since it states that OAT means all flights that do not comply with GAT, although most military aircraft are able to comply with both GAT and OAT rules.

Moreover, operating military and other State aircraft (that is, with reference to article 3(b) of the Chicago Convention, aircraft used in military, custom and police services) requires skills and capabilities for aircrews, ATM and air defence personnel and organisations beyond the scope of civil aviation.

To gain and maintain the levels of readiness and proficiency mandated for these skills and capabilities, the military perform aerial activities, which are not covered by ICAO provisions, for GAT flights, neither by the EU Regulations. Examples of such aerial activities include airborne air to air refuelling, formation flying, air policing, intelligence surveillance and reconnaissance (IS) flights, air combat manoeuvrings, airspace reservations, search and rescue (SAR), etc.

The EUROCONTROL EUROAT document and some States' legal documents, define OAT as:

“The status that facilitates military and other State aircraft flights, for which the GAT framework is not suited to provide the rules, regulations and ATM support needed to fully ensure successful mission accomplishment”.

Simply, OAT could be understood as GAT + additional rules with specific ATM services to support the miliary mission. The military needs OAT to exploit the full range of operational and training mission requirements, as well as aircraft capabilities to reach and maintain expected levels of readiness and proficiency.

Drivers towards OAT harmonisation and OAT-GAT interface

The idea to harmonise OAT rules and to define military requirements for military flying OAT-IFR started in 2005 at the EUROCONTROL MilHaG (Military Harmonisation Group), further introduced to CMIC (Civil Military Interface Committee) and tasked for development by DG/MIL (the current EUROCONTROL Civil-Military Cooperation Division).

To accomplish this task and to develop OAT-GAT harmonised rules/procedures, three-step approach has been proposed: harmonisation of OAT rules; European-wide OAT transit service (OATTS) development; and European-wide use of military training areas.

The changed security environment in Europe has resulted in revisiting the concept. The hybrid/precrisis environment at the eastern border of Europe has generated a significant increase of cross-border military flights. Most procedures in place work seamlessly within one State, but cross-border aspects are difficult to coordinate, hence harmonisation of existing tools/processes/procedures and exploring new possibilities for managing military air traffic and airspace are needed.

The principle of the OATTS concept agreed back then is still valid – to connect national structures and arrangements via defined entry and exit parameters under the framework of the EUROAT to form a flexible system facilitating OAT-IFR flights across Europe.

It was intended to develop as much as possible the coordination between OATTS and the civil trajectory management system, since this approach seemed to provide viable benefits in terms of military and civil operational flexibility through increased civilmilitary information sharing.

Talking about the development of operational flights across Europe, it is important to underline that OATTS was joint NATO/ EUROCONTROL work, presented to the NATO Aviation Committee and to the MAB (Military ATM Board) in 2016. The role of the European Defence Agency (EDA) in an EU context was also important to include the potential agreement on common high-level operational requirements into the Military Aviation Strategy (MAS). Other benefits included raising the visibility of NATO movements, so that States can assign due priority to such traffic when required, including improved processes for expeditious handling of diplomatic clearances.

Eventually, the OATTS proposal was absorbed into SESAR, feeding the development and validation of the key concept of “mission trajectory” enabling the integration of military ATM demand into the future trajectory-based ecosystem.

The overarching concept of mission trajectory relies on technical solutions, a new flight plan format for OAT, as well as solutions enabling the safe and dynamic management of airspace and military crossborder flights in Europe.

The main drivers for OAT transit for the effective use of the European airspace in medium and long term could be identified as, but not limited to: EUROAT, the OAT Flight Plan and improved OAT Flight Plan (iOAT-FPL), EU cross-border diplomatic requirements for transit operations and military training areas in accordance with the new military training requirements.

Optimising integration of military training areas into European airspace operations

EUROCONTROL CMC has proposed ideas and initiated cooperation with relevant civil-military stakeholders to develop the evolution of military training areas in Europe to cater for the future needs.

The CMC proposal addresses the usage of the cross- border/FIR/UIR cooperation and application of modular airspace design principles which could be supported by the following enablers:

  • Interoperable ASM systems, minimum CNS infrastructure;
  • Specific studies on impact on GAT, CNS capabilities and access to RF spectrum;
  • Interoperable cross-border air traffic control and air defence organisations;
  • Involvement of national stakeholders including ANSPs;
  • Incremental approach for deployment;
  • ICAO SARPS and (EC) Reg No 2150/2005 as regulatory framework.

Main steps for consideration to design new training areas include, inter alia:

  • Identification and outline of a geographic region with low density of civil commercial air traffic;
  • Airspace resource optimisation to enable application of new military training principles;
  • Solutions for the shared use of training areas by Member States of the same geographic area over sea and land;
  • Joint use of ground infrastructure facilitating military live trials in new training areas for 4th and 5th generation fighter aircraft.

EUROAT

EUROAT, first released in 2013, was intended to be a harmonised OATTS enabler, developed as the EUROCONTROL specifications for harmonised rules for OAT-IFR inside controlled airspace of the ECAC area. The aim was to enable the EUROCONTROL Member States to achieve the intended harmonisation based on their individual national implementation. National implementation of the rules and procedures specified in this document targets the OAT-IFR harmonisation/standardisation within the controlled airspace of all States that have chosen to implement EUROAT. Along with the national rules, States file differences and amendments to the document which makes it clear that rules are far from harmonised within the ECAC area.

As of today, EUROAT has been implemented by 22 States and six more expressed intent to implement. Twenty-two States have formally implemented EUROAT and provided their country chapters and six other States have officially notified about their plan to formally implement; MUAC, for example, uses EUROAT in its daily work.

IOAT FPL

With a new look at OATTS, the harmonisation focus is put on operational and technical enablers for State aircraft transiting Europe. The operational concept behind it is the military mission trajectory and one of its technical enablers is the improved OAT Flight Plan (iOAT-FPL).

The main goal is to streamline national processes and procedures for the filing and processing of military IFR flight plans. This will allow cross-border provision of specific ATM services to military missions and full awareness of OAT-IFR flights through dissemination of respective iOAT FPL data to all parties concerned, which will also enhance ATM and flight safety. The iOAT FPL should be seen as an important real step towards harmonisation of the military mission-related information, and integration of military demand in the ATM network operations. The consolidated data related to specific military en-route activities will be integrated into the ATM network and provide detailed information elements through the transparent and centralised management of iOAT FPL. In the new free route environment, this information is important to assess the impact on capacity and network complexity.

The iOAT FPL itself is a structured, formalised flight plan based on the ICAO 2012 model flight plan form that aggregates information regarding military IFR specifics and is shared through the Network Manager (NM) centralised flight plan processing system (IFPS) with all pertinent ATM and relevant non-ATM actors.

EUROCONTROL developed two documents as technical enablers for a harmonised and improved OAT Flight Plan (iOAT FPL) implementation – Guidelines and Concept of Operations (CONOPS).

The iOAT FPL implementation by the States is ongoing and may require software adaptations to create a seamless interface between OAT/GAT flight planning systems. Local services and procedures available for cross-border operations also need to be put in place.

As of now, NM included the iOAT FPL in the present NM system and is available for all States to use both operationally and technically for the implementation.

Diplomatic clearance

Diplomatic clearances and cross-border movement permissions (CSDP) are also crucial enablers and facilitators of military cross-border deployments in Europe.

In 2012, under the EDA umbrella, the first Diplomatic Clearances Technical Arrangements (DIC TA) was developed allowing the Member States’ Armed Forces to swiftly and smoothly cross European territories and airspaces with transport aircraft. The DIC TA has been signed by majority of the EU States.

In 2021, additional technical arrangements have been developed and signed by the Member States to optimise surface and air cross-border movement permission (CBMP) procedures, complementing the DIC TA to cover all other fixed and rotary wing platforms’ movements. Individual and in combination, these arrangements also contribute to moving European NATO forces (LoAs could be considered in addition).

A new approach to military training areas

Future fifth generation fighter aircraft will require a different quality of military training areas to exploit the full range of their capabilities. Larger volumes of airspace will be needed, which in Europe is difficult to achieve by one State alone.

Therefore, it will be necessary to develop more flexible and dynamic allocation mechanisms and future airspace use requirements across multiple States as the basis for future European wide-use of cross-border training areas over land and sea.

The way ahead

The OAT harmonised rules and procedures specify the services needed for the military. However, new demand for air mobility and cross-border areas requires the transformation of national arrangements towards harmonised procedures for all military users across Europe.

To reach fully workable civil-military arrangements for military air mobility and future military training areas, a common understanding among the States and support from the national political civil and military authorities is vital.

Additionally, national regulators and service providers must allocate the resources to create or to share cross-border procedures and to upgrade their flight planning and flight data processing systems, including the development and implementation of respective diplomatic clearance agreements.

Behind this new focus on military mobility and cross-border training while ensuring effective use of the airspace is the need to foster both the security and defence and the effectiveness of ATM system in Europe. The civil-military enablers for harmonised GAT-OAT interface exist or are being developed, they just need to be understood and enforced by all relevant aviation and ATM actors in Europe.

Where there is a will, there is a way. Let’s explore together the proposed ways and tackle the challenges for the benefit of all.

Mariana Anguelova
Mariana Anguelova
Stakeholder Relations Manager and Senior Civil-Military ATM Cooperation Expert
EUROCONTROL

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