European network’s comprehensive CNS Knowledge and Analytics Centre

Sherlock is EUROCONTROL’s comprehensive CNS Knowledge and Analytics Centre, built on a cloud‑based big data architecture. It delivers high‑quality performance information, real‑time monitoring, historical trends and detailed insights into the behaviour of Communication, Navigation and Surveillance systems across the European network. 

The importance of Sherlock has grown due to several escalating challenges in the European CNS environment:

• GNSS Radio Frequency Interference (RFI): GNSS jamming and spoofing events — formerly rare and localised — are now frequently detected across Europe and neighbouring regions. These disruptions degrade multiple CNS functions, including ADS‑B, CPDLC, EGPWS/TAWS and other aircraft systems.
• Transponder Over‑Interrogation: High sensor and aircraft density in European airspace can lead to excessive interrogation rates, causing degraded transponder performance and unreliable surveillance data.
• 1030/1090 MHz Band Congestion: Growing traffic levels and reliance on this limited band are intensifying pressure on surveillance and collision‑avoidance systems.

These challenges highlight the need for coordinated monitoring, shared situational awareness and proactive CNS management—roles Sherlock is designed to fulfil.

While Sherlock is designed to support the modernisation and resilience of CNS services, its role has become increasingly important due to several pressing challenges affecting the European CNS landscape.

The most prominent and fast-growing issue is GNSS Radio Frequency Interference (RFI), including both jamming and spoofing. Once occasional and geographically limited, such disruptions are now observed frequently across various parts of Europe and neighbouring regions. This poses significant risks because GNSS degradation affects multiple CNS systems simultaneously:

• ADS-B position reporting becomes unreliable or unavailable when aircraft lose GNSS input, compromising surveillance continuity.
• CPDLC datalink operations can degrade when navigation inconsistencies cause aircraft to deviate from expected routes or require additional controller intervention.
• Cockpit safety systems can be triggered erroneously, including false EGPWS/TAWS alerts, which significantly increase pilot workload and undermine the “trust your instruments” principle.

As these effects accumulate, GNSS disruptions reduce predictability in the network and complicate both pilot and controller actions.

Beyond GNSS vulnerabilities, the CNS environment is also impacted by transponder over interrogation, a phenomenon driven by the dense concentration of surveillance sensors and airborne transponders in busy European airspace. Excessive interrogation rates can lead to:

• degraded transponder performance,
• reduced reliability of surveillance data,
• increased technical load on aircraft systems.

In addition, the 1030/1090 MHz frequency band is experiencing growing congestion.

As traffic levels rise and more surveillance technologies rely on this narrow band, the risk of frequency saturation increases, reducing the robustness of surveillance and collision avoidance systems. These issues create systemic pressures on CNS infrastructure and reinforce the need for coordinated monitoring, early detection and shared situational awareness across all operational stakeholders.

Sherlock integrates multiple advanced applications and inspector tools within a single environment, including:

Applications:

• GRID – GNSS Radio Frequency Interference Detector: Real‑time detection, visualisation and impact assessment of GNSS jamming and spoofing events.
• RMA-HMU – Regional Monitoring Agency / Height Monitoring Unit: Supports RVSM compliance through detailed height‑keeping performance analysis.
• CNS-CAP – CNS Capabilities: Provides a structured, modern overview of aircraft CNS capabilities declared in flight plans.
• SSI – Surveillance System Infrastructure: A centralised database of surveillance assets to support coverage analysis and optimisation.
• ACAS – Airborne Collision Avoidance System Analytics: Analysis of ACAS behaviour, RA events and contributing operational conditions.

Inspector Tools:

• Flight Inspector: High‑fidelity reconstruction and analysis of individual flight trajectories and CNS anomalies.
• Traffic Inspector: Regional or local performance analysis across groups of flights, identifying patterns and localised issues that may affect capacity or controller workload.
• Network Inspector: Pan‑European CNS performance overview to detect systemic issues and supporting strategic planning, performance monitoring and coordinated mitigation at network level. 

Sherlock provides operational stakeholders with a unified, data‑driven environment to understand and manage CNS performance at flight, regional and network levels. Its benefits include:

• Early detection of CNS issues through real‑time alerts and automated monitoring.
• Enhanced operational resilience by highlighting emerging risks and enabling rapid, coordinated response.
• Improved situational awareness with pan‑European visibility of CNS behaviour and interference hotspots.
• Support for safe and efficient operations via tools that reduce controller and pilot workload impacts caused by CNS anomalies.
• Data‑driven planning and evolution of CNS infrastructure through rich analytics and historical performance datasets.