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Guardrail Common Sensor (GRCS) is a legacy Special Electronic Mission Aircraft that has been providing critical Aerial Intelligence, Surveillance and Reconnaissance (AISR) capability for over 45 years. Guardrail was originally built as a Cold War system to provide indications and warnings against adversaries in both the European and Pacific Theaters of Operation. The Guardrail system has been modernized since inception to maintain relevancy and to enable continued prosecution of emerging threats within the changing battlespace.

GRCS is the Army’s current integrated Signals Intelligence (SIGINT) platform that provides near real-time targeting information to tactical commanders and supports full-spectrum operations. GRCS is hosted on a fixed-wing aircraft (King Air B200), designated RC-12X, and is the Army’s premiere airborne SIGINT-collection and precision targeting location system. The GRCS fleet is comprised of 14 mission aircraft supporting multiple combatant commands and five training platforms. In Fiscal Year 2018, the GRCS mission aircraft’s economic useful life was extended until 2034.

GRCS sensor capability produces high-accuracy Communications Intelligence (COMINT) and Electronics Intelligence (ELINT) for battlefield mapping of common and modern signals of interest for detection, identification and geolocation of known threats. The Distributed Common Ground System–Army (DCGS-A) Operational Ground Station (OGS) processing, exploitation and dissemination capabilities allow for real-time signal exploitation and reporting, ensuring information dominance to commanders. GRCS data and payload tasking and mission operations support are provided by the 116th Military Intelligence Brigade at Fort Gordon, Georgia. The standard concept of operations supports both single-ship, multiship and cooperative operations utilizing Tactical Common Data Links (TCDL) and network based infrastructure back to Continental United States (CONUS) based garrison locations where it is correlated, exploited and disseminated to supported commands.


The GRCS SIGINT capabilities enable the exploitation of common and modern signals spanning a large frequency band with precision accuracy. Ground processing software and hardware are part of the Army Tactical SIGINT Baseline and are interoperable with DCGS-A OGS and CONUS garrison locations, which reduces the forward deployed footprint significantly. The warfighter will benefit from planned improvements through Guardrail modernization efforts, including near term technical refresh efforts for the ELINT and COMINT subsystems utilizing software defined open architecture as well as cockpit avionics upgrades. GRCS is the only AISR platform in the Army’s inventory that is currently certified for precision long-range fires support.


  • Integrated COMINT and ELINT collection and reporting
  • Enhanced signal classification and recognition and precision emitter geolocation
  • Advanced integrated aircraft cockpit
  • TCDL


FY16: Began Pilot Situational Awareness Monitor Mod with first article induction

FY17: Began aircraft avionics upgrade to meet military and civilian requirements for communication, navigation and surveillance to meet Global Air Traffic Management (GATM) requirements and enhanced MODE-5 Identification Friend or Foe (IFF) capability


  • Completed High-Frequency ARC-220 Radio modification allowing for Beyond Line-of-Sight communications during ferry operations
  • Awarded contract for COMINT and ELINT subsystem upgrades to improve performance and address obsolescence issues
  • Upgraded COMINT system software to meet urgent Operation Needs Statement
  • Increased GRCS cooperative SIGINT capability by migrating all subsystems to Joint Interface Control Document compliance
  • FY16-FY18: Continued support to worldwide contingency operations



  • Complete aircraft avionics upgrade to meet military and civilian requirements for communication, navigation and surveillance to meet GATM requirements and enhanced MODE-5 IFF capability
  • Complete Pilot Situational Awareness Modification – provides pilots with moving map capability


  • Upgrade ARC-201 Ultra High-Frequency Radio to address obsolescence issues
  • Upgrade Global Positioning System (GPS) antennae to address Assured Positioning, Navigation and Timing (A-PNT) requirements

FY20-FY24: Upgrade COMINT and ELINT subsystem for mission aircraft to maintain tactical relevancy within the AISR layer and address multiple obsolescence and diminishing manufacturing source issues

FY22-FY24: Upgrade embedded GPS/Inertial Navigation System to improve capability and meet A-PNT requirements


  • Adams Communications & Engineering Technology (Waldorf, MD)
  • Systems Engineering Solutions, Inc. (Huntsville, AL)
  • Lockheed Martin (Owego, NY)
  • Zeta Associates (Fairfax, VA)
  • Argon ST (Mountain View, CA)
  • L3 Communication Systems – West (Salt Lake City, UT)
  • Northrop Grumman Mission Systems (Sacramento, CA)
  • Northrop Grumman Information Technology (Carson, CA)
  • Northrop Grumman (Herndon, VA)
  • Textron Aviation (Wichita, KS)