AN/ALQ-172

AN/ALQ-172
Electronic countermeasures
Electronic warfare officer operating the ALQ-172 auxiliary control
StatusIn service
Manufacturing Info
Designer(s)ITT Avionics
Manufacturer(s)
Introduced1984 (1984)
Production period1984–present
No. produced>940 systems
>6,000 LRUs
Developed fromAN/ALQ-117(V)[1]
Specifications
Frequency Range0.1–18 GHz
(299.8–1.7 cm)[3]
Weight1,631 lb (740 kg)[1]
Input voltage
Usage
Used by country United States
Used by militaryUS Air Force
Platform(s)
Variants
  • AN/ALQ-172(V)
  • AN/ALQ-172(V)1
  • AN/ALQ-172(V)2
  • AN/ALQ-172(V)3

AN/ALQ-172 is an integrated airborne defensive electronic countermeasure internally-mounted system for the B-52 Stratofortress, MC-130E Combat Talon, MC-130H Combat Talon II, AC-130H Spectre and AC-130U Spooky.[1][5] Originally produced by ITT Avionics in the early 1980s, and later L3Harris Technologies,[2][3] it was designed to improve low-level penetration survivability of the B-52.[1]

History

First delivered by ITT in 1984, a 1996 study by analysts from Battelle Memorial Institute determined problems with repair of the ALQ-172 resulted in the highest cost per flying hour (CPFH) of any system on the B-52.[5][6] The United States Air Force instituted Engineering Change Proposal (ECP) 93 modifying the system's memory and processing capability. The ECP 93 modifications upgraded ALQ-172(V)1 line-replaceable units (LRUs) 1, 3, 4, and 10 and replaced LRU 2 resulting in the enhanced ALQ-172(V)3.

Also in FY96, Air Staff directed the enhanced ALQ-172(V)3 be installed on AC-130H gunships replacing the earlier (V)1 version of the ALQ-172, and non-supportable AN/ALQ-131 jamming pods.[5] Also on special operations forces (SOF) AC-130U, MC-130H and MC-130E aircraft, an additional ALQ-172 subsystem was installed, bringing the number to 2 sub-systems; one forward and one aft, with a single common display and control unit. Other engineering differences on these aircraft involved adding low-band countermeasures transmitters, antennae and antenna control units.[5]

By fiscal year 1997 (FY97), the same group reported a second system was needed on the aircraft for full threat protection.[5]

Further upgrades have incorporated geolocation capabilities, advanced countermeasures and new technologies.[7][8] The upgrades are part of the 2021 maintainability and reliability system (MARS) upgrade;[3] a 10-year, $947 million project enhancing the performance of the B-52's electronic countermeasures systems.[8][6] Nine line-replaceable units (LRUs) have been upgraded, with five of those tested by mid-2024.[8] As part of the MARS contract, LRUs 1, 3, 4, and 10 have been upgraded with LRU-2 being replaced with a new high-voltage power supply. With continuing support and upgrades, the ALQ-172 is expected to be in service well into the 2040s.[7]

Technical description

Features

Integrated with aircraft controls and displays, the system provides countermeasures capabilities for multiple sophisticated pulse, continuous wave, doppler and monopulse threats simultaneously.[1][7] Using digital frequency discrimination (DFD) technology, the system is capable of determining pulse width, angle of arrival (AOA), and pulse-repetition frequency (PRF) of threat signals, deinterleaving and processing them.[5] Countermeasure techniques available to the ALQ-172(V)3 include spot noise, barrage noise, swept noise, range/angle deception, cross-eye, and false target generation.

In accordance with the Joint Electronics Type Designation System (JETDS), the AN/ALQ-172 designation represents the 172nd design of an Army-Navy electronic device for an electronic countermeasures system. The JETDS system also now is used to name all Department of Defense and some NATO electronic systems.

Characteristics

AN/ALQ-172(V)2
  • Weight per aircraft: 1,631 pounds (740 kg)[1]
  • Operating frequency range:[3]
    • Low-band: 0.1–2 GHz (300–15 cm)
    • Mid-band: 2–6 GHz (15.0–5.0 cm)
    • High-band: 6–18 GHz (5.0–1.7 cm)
  • LRUs per system: 7
  • Systems per aircraft: 2
  • Antennas per aircraft: 7
  • Systems produced: 943 (over 6,000 LRUs)

Components

Based on the MARS upgrades, the below list contains information regarding components of the AN/ALQ-171(V)3 version of the jammer.

  • LRU-1: Countermeasures Receiver / Receiver-Processor[7][9] – Detects and digitizes threat radar emissions; pulse characterization (pulse width, PRF), AOA estimation, de-interleaving and threat signal processing. Part number: R-2247/ALQ-172
  • LRU-2: High-Voltage Power Supply (HVPS) / Power & Cooling Distribution[10] – Supplies high-voltage power required by transmitter/modulator stages; provides power conditioning and supports cooling/air distribution interfaces. Noted in field support/repair solicitations. Part number: A301402-1
  • LRU-3: Modulator / Antenna Control / Timing Processor[7][10] – Handles waveform modulation/timing for transmitters and/or controls antenna switching and low-level RF routing; subject of wiring/TCTO changes in field engineering records. Part number: A301405-1
  • LRU-4: Countermeasures Transmitter / Power Amplifier[7][8] – High-power ECM transmit functions: amplification of PR, PD and CW ECM waveforms, deception waveform generation and often part of antenna T/R group. Part number: A301408-1
  • LRU-5: Chassis / Equipment Mounting / Interface[11] – Structural/electrical equipment assembly containing non-RF electronics, mounting, aircraft interface and I/O connections; naming varies across variants. Part number: A301410-1
  • LRU-6: Antenna Amplifier / Receiver Converter[7][3] – Quadrant amplifier / blade amp assemblies for receive/transmit conversion; mid/high-band amplifier converters used in the antenna group. Part number: A301414-1
  • LRU-7: Auxiliary Receiver / Processor / Packaging Module[10][11] – Auxiliary receiver/processor or module appearing paired with other LRUs in packaging/field support documentation; role varies by installation. Part number: A301416-1
  • LRU-8: Control / Display / Human-Machine Interface (HMI) Unit[7] – Crew interface and control electronics (display, control panel, I/O); sometimes split into separate LRUs depending on installation. Part number: A301420-1
  • LRU-9: Support / Conditioning / RF Filter / RF Switch Assembly[12] – RF switching, filtering, bias supplies and small support modules that route signals between receivers, processors, and transmitters; listed in upgrade/field-support summaries. Part number: A301425-1
  • LRU-10: Processing / Upgrade Module (subject of MARS upgrades)[10][12] – Identified in SRD/upgrade documents as a significant module targeted for upgrade alongside LRUs 1,3,4; likely contains processing, digital logic or waveform generation elements. Part number: A301430-1

Variants

  • AN/ALQ-172(V)
  • AN/ALQ-172(V)1 – on MC-130H Spectre and AC-130U Spooky aircraft[1][5]
  • AN/ALQ-172(V)2 – on B-52H Stratofortress[1]
  • AN/ALQ-172(V)3 – on AC-130H Spectre,[1][5] potentially extending frequency coverage to 40 GHz (7.5 mm)[3]

See also

References

  1. ^ a b c d e f g h i j "ALQ-172(V) - Archived 03/2003" (PDF), Forecast International, March 2002, retrieved 20 December 2024
  2. ^ a b "Airborne Radar Jammers" (PDF). The Journal of Electronic Defense. Alexandria, Virginia: Association of Old Crows. July 2018. Retrieved 4 September 2025.
  3. ^ a b c d e f g Withington, Dr Thomas (30 July 2024). "MARS Attacks". Armada International. Retrieved 7 October 2025.
  4. ^ "System Requirements Document (SRD) for Integration of the Enhanced ALQ-172 & Low Band Jammer on to the AC-130U and MC-130H Aircraft". Wright-Patterson AFB, Ohio: ASC/LUN (SOF INTEGRATION IPT). 7 April 1998. Retrieved 6 October 2025.
  5. ^ a b c d e f g h Pike, John (22 April 2000), "AN/ALQ-172 Countermeasures System (CMS)", FAS Military Analysis Network, retrieved 23 December 2024
  6. ^ a b Wolfe, Frank (1 September 2021), "L3Harris Receives U.S. Air Force Contract Worth Up to $947 Million for AN/ALQ-172", DefenseDaily, retrieved 23 December 2024
  7. ^ a b c d e f g h "AN / ALQ-172 B-52 Self Protection System", L3Harris, retrieved 23 December 2024
  8. ^ a b c d Cenciotti, David (12 July 2024), "B-52's Upgraded AN/ALQ-172 Self-Protection System Tested During Recent Flight", The Aviationist, retrieved 23 December 2024
  9. ^ Peck, Michael (31 October 2016). "Harris awarded B-52 electronic warfare contract". C4ISRNet. Retrieved 7 October 2025.
  10. ^ a b c d "B-52H Field Engineering Support (AN/ALQ-172(V)2)". HigherGov. 8 May 2024. Retrieved 7 October 2025.
  11. ^ a b "Future-Proofing the B-52". L3Harris. 28 March 2025. Retrieved 7 October 2025.
  12. ^ a b "L3Harris Tests Upgraded Line Replaceable Units in B-52 Electronic Warfare System". Defense Mirror.com. 10 July 2024. Retrieved 7 October 2025.
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