The AN/ALQ-136 is an electronic countermeasures (ECM) system designed for military helicopters, specifically created to protect against radar-guided threats. Developed by ITT Industries (now part of ITT Exelis), the AN/ALQ-136 was introduced in 1982 and became an essential component of the U.S. Army’s electronic warfare capabilities for rotary-wing aircraft, including the AH-1F Cobra attack helicopter. This system detects and jams radar signals to protect helicopters from radar-guided weaponry.

Development and Purpose

The AN/ALQ-136 system was developed in response to the increasing threat posed by radar-guided anti-aircraft weapons. As rotary-wing aircraft are frequently deployed close to hostile environments, they require robust countermeasures systems to survive in areas heavily defended by radar-guided systems. The AN/ALQ-136 was specifically designed to automatically detect and analyze radar signals, jamming them as necessary to prevent effective targeting.

The system integrates a hybrid processor designed by ITT, which uses AMD AM2901B bit-slice processors for customized, mission-specific processing. In the early 1980s, Digital Signal Processors (DSPs) were in their infancy, so the system relied on a custom-built processor using bit-slice elements to meet the necessary processing speeds and reliability requirements. Two of these hybrid processors are used per AN/ALQ-136 unit, with one assigned to the Modulation (MOD) Recovery board and the other to the Side Lobe Opposition (SLO) processor board.

Key Features and Operation

The AN/ALQ-136 radar jammer functions by detecting hostile radar emissions, classifying the threat, and then jamming the radar. It employs both noise and deception jamming techniques depending on the type of radar detected. The system can operate automatically, requiring no direct pilot input once active, which allows for rapid response to incoming radar signals.

Key features include:

• Broad Frequency Range: The system can operate across multiple radar frequency bands, enhancing versatility against various radar types.
• Custom Hybrid Processor: Integrating four AM2901B processors running at 16 MHz each, the hybrid provides real-time 16-bit processing for radar signal analysis.
• Durable Packaging: The processor unit is built on a ceramic substrate with gold traces and sealed in a metal package to shield against interference from both external sources and the helicopter’s own systems.

Applications and Legacy

The AN/ALQ-136 was deployed on several U.S. Army helicopters, including the AH-1F Cobra and AH-64 Apache. The system allowed these helicopters to operate in high-threat environments with enhanced protection against radar-guided missiles.

The AN/ALQ-136 and similar early electronic warfare systems paved the way for modern ECM technology, although they have since been replaced by more advanced systems like the AN/ALQ-211, which offers greater flexibility and upgradeability.

International Usage and Current Status

Although retired by the United States and Israel, the AH-1F Cobra equipped with the AN/ALQ-136 is still in service with several other nations, including Pakistan, Jordan, and Turkey. In the United States, the U.S. Forest Service operates several demilitarized AH-1F Cobras for firefighting purposes, though these lack operational countermeasures.

References

1. U.S. Army Intelligence and Security Command, “Electronic Warfare: Concepts and Technologies for Air Defense,” Army Research Library, 1986.
2. “Advanced Rotorcraft Protection Systems: Historical Overview,” Aerospace & Defense Journal, 2002.
3. ITT Exelis Systems Engineering Division, “AN/ALQ-136 Electronic Warfare System Manual,” Internal Engineering Report, 1984.
4. Duncan, N. (2015). Electronic Warfare and Rotary-Wing Aircraft. Naval Institute Press.
5. National Air and Space Intelligence Center, “An Assessment of U.S. and Soviet Helicopter Countermeasures,” NASIC Technical Paper, 1991.
6. Adams, C., & Bailey, T. (2023). “The Evolution of DSP Technology in Military Applications,” Journal of Military Electronics and Computing, Vol. 31, pp. 45-59.
7. “Foreign Military Sales Database,” U.S. Defense Security Cooperation Agency, 2019.

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