CASTLE

General Dynamics European Land Systems has successfully demonstrated an acoustic drone detection system on the ASCOD infantry fighting vehicle. This is a passive, vehicle-integrated sensor that locates FPV attack drones in real time without emitting any signal that an enemy could detect. The system, called CASTLE, was developed in cooperation with Microflown AVISA and demonstrated in a proof-of-concept exercise that tested acoustic drone detection across manned and unmanned platforms under realistic flight conditions. The threats came from non-commercial FPV drones operated by Red Team Shield pilots — professional adversarial testers whose job is to challenge a system's limits rather than confirm its best-case performance. CASTLE proved robust performance across many demanding scenarios, according to GDELS, confirming its effectiveness for early warning of FPV attack drones on next-generation armored vehicles. The acoustic detection approach that CASTLE represents addresses a gap in the counter-UAS sensor toolkit that has become increasingly apparent as FPV drone warfare has matured. Radar-based detection systems are effective but active — they emit signals that adversaries equipped with radar warning receivers can detect, potentially revealing the position and capabilities of the platform they're protecting. RF detection finds drones communicating with their operators but misses autonomous or pre-programmed attack runs where no control signal is present. Optical and thermal sensors provide detection capability but are constrained by line of sight, weather, and the visual clutter of complex operational environments. Acoustic sensors that passively listen for the sound signatures of drone motors and propellers bypass all of those limitations simultaneously — they detect the physical presence of the drone regardless of its electronic configuration, emit nothing that could be detected by the adversary, and work in degraded visual conditions where optical systems struggle. The passive characteristic is operationally significant in ways that go beyond simple emissions control. An armored vehicle that activates an active radar or RF detection system to search for threats announces to any adversary monitoring the electromagnetic spectrum that it is searching, where it is searching, and what its sensor capabilities look like. A passive acoustic system provides the same detection function without any of that disclosure. The vehicle knows a drone is approaching. The drone operator does not know the vehicle has detected it. That asymmetry of awareness is precisely what early warning systems are supposed to create, and CASTLE achieves it without the electromagnetic signature cost that active sensors impose. Microflown AVISA's contribution to the CASTLE system brings specialized expertise in acoustic vector sensing — a technology that goes beyond simple sound detection to provide precise spatial localization of the sound source. Knowing that a drone is present is useful. Knowing exactly where it is in three-dimensional space, updated in real time as it maneuvers, is what allows a countermeasure system to actually engage it. CASTLE provides real-time, precise spatial threat localization, meaning the system outputs not just a detection alert but a targeting-quality spatial position that can cue whatever countermeasure the platform or the crew chooses to employ. Combined with the sensing-on-the-move capability that GDELS confirmed — the system works while the vehicle is driving, not only when stationary — CASTLE integrates into the operational tempo of a maneuvering armored formation rather than requiring the vehicle to stop and listen. The ASCOD platform on which CASTLE was demonstrated is one of Europe's most widely operated infantry fighting vehicles, in service with Austria, Spain, and other customers. Its selection as the demonstration platform is not incidental — ASCOD represents the class of armored vehicle that faces the highest FPV drone threat exposure in the current operational environment. Infantry fighting vehicles move with dismounted troops, enter contested urban areas, and operate at the forward edge of ground formations where FPV threats are most frequently employed. A detection system that integrates onto ASCOD without modifying the vehicle's operational profile or adding an emissions signature has a straightforward path to the customers who operate the platform. The integration on both manned and unmanned platforms is a detail worth noting for what it suggests about the system's broader applicability. Unmanned ground vehicles face the same FPV drone threat as their manned counterparts but cannot rely on a crew's situational awareness to supplement sensor coverage. An acoustic detection system that provides spatial threat localization to an unmanned platform's onboard systems gives the UGV the same early warning capability as a manned vehicle, enabling autonomous or remote-operator countermeasure responses without requiring a human in the loop for initial detection. As manned-unmanned teaming becomes more central to how European armies plan to operate armored formations, the ability to extend consistent counter-UAS awareness across both manned and unmanned elements of the team becomes increasingly valuable. The Red Team Shield adversarial testing methodology deserves credit for the rigor it brings to the demonstration results. Proof-of-concept demonstrations conducted against cooperative targets under favorable conditions produce results that tell operators very little about how a system will perform when someone is actively trying to defeat it. Non-commercial FPV drones operated by professional red team pilots who are flying challenging profiles specifically designed to stress the detection system's limits produce results that are actually meaningful for operational planning. CASTLE's robust performance under those conditions is a more credible validation than a demonstration against slow, predictable targets in ideal conditions.

CASTLE

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CASTLE

GDELS tests passive drone detection system on ASCOD vehicle

Microflown AVISA tests new gunfire locator

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About The Defence Blog