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AN/ALQ-161 ECM System for the B-1B

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Post subject: AN/ALQ-161 ECM System for the B-1B Reply with quote

Date Posted: 14-Mar-2005

Jane's Avionics


AN/ALQ-161 ECM system for the B-1B


Airborne Electronic Counter Measures ( ECM), integrated suite.


AIL Systems (now a business unit of the EDO Corporation) is the prime contractor for the AN/ALQ-161 defensive countermeasures suite for the US Air Force Rockwell B-1B Lancer. This was launched in 1972 under AIL Systems leadership for the Rockwell B-1A bomber, but the effort came to a halt when the aircraft was cancelled in June 1977. The programme was, however, reinstated in October 1981. AIL Systems accordingly resumed its task as ALQ-161 project leader, having participated in limited flight trials with one aircraft since 1979. The current equipment was developed under restart and initial production contracts, worth more than US$1,700 million, which were awarded to AIL Systems and its subcontractors. Each aircraft set is understood to have cost around US$20 million, approximately one-tenth the cost of a complete B-1B, and comprises no fewer than 108 LRUs, with a total weight of over 2,300 kg exclusive of cabling, displays and controls.
The operating frequency range is approximately 0.5 to 10 GHz, to cover early warning, ground-controlled interception, surface-to-air missile and interceptor radar frequencies. Jamming signals in the higher regions of the ECM spectrum are emitted from three electronically steerable, phased-array antennas: one in each wing-glove leading-edge and the third in the fuselage tailcone. Each antenna provides 120º azimuth and 90º elevation coverage. Lower frequency signals are emitted from quadrantal horn antennas mounted alongside the high-frequency equipment.
Major subcontractors in the AN/ALQ-161 programme were Northrop Grumman, Litton Industries and Sedco Systems. All companies served as subsystem managers with responsibilities for receivers, data processing and jamming techniques. Northrop Grumman provided the low-frequency jamming antennas and Sedco supplied the phased-array antennas.
AIL Systems was responsible for system integration and for the LRUs, including 51 unique designs. Most of the LRUs are about 0.03 to 0.06 m3 in volume and weigh between 18 and 36 kg. The majority are readily accessible and can be removed easily or installed by one or two people. Total power required is about 120 kW.
Improvements introduced during the programme included a frequency extension into the K-band to increase the warning and jamming performance, extension into the low-frequency domain below 200 MHz to improve the response of the warning system, introduction of a digital radio frequency memory to permit the deception jamming of more advanced radars, notably those employing pulse Doppler techniques, and introduction of a new Tail Warning Function (TWF).
An IBM 101D computer functions as the central processor. The computer, employing Jovial-based software, identifies the function of every hostile radar, assesses its potential threat and assigns a jamming priority. Three sets of phased-array antennas mounted in the wing leading-edges and tail provide full 360º coverage in Bands 6, 7 and 8, antennas for lower frequencies being located fore and aft in the airframe.
Two complete systems were delivered for continuing trials with a modified Rockwell B-1A in the Summer of 1984 and for the first production B-1B; the latter made its initial flight in October 1984. Production rate was built up to four systems a month by May 1986. In August 1985, AIL Systems was awarded a US$1,800 million contract for the final 92 ALQ-161 shipsets.
Problems in development were reported in mid-1986, leading to the first 22 B-1Bs not being equipped with the TWF which had been scheduled to enter service in mid-1987. Problems with the TWF and with repeatability of results from the system as a whole were part of a list of deficiencies in the B-1B's performance made public at the end of 1986. Of a US$600 million request made by the US Department of Defense at that time to extend the capabilities of the B-1B, almost US$100 million was allocated to bring the ALQ-161 up to its original specification and solve other problems (according to the DoD), while the bulk of a US$131 million element within the US$600 million total requested for expenditure in 1988/89 was to upgrade the defensive avionics suite to meet capabilities which have emerged since the original baseline was set in 1982.

System operation

Operation of the AN/ALQ-161A is primarily in an automatic mode, where the system receives, identifies, and jams threat radars instantaneously. However, the Weapons Systems Operator (WSO) can manually intervene if desired. Complete Situational Awareness (SA) is provided on two threat display formats to the WSO to include constant information of threat type, mode, location jamming status, frequency and relative amplitude. Other additional system and/or threat information is available on call to the operator through a correlated joystick that allows him to designate specific threats and request data from either display format. Additional manual functions such as jamming modifications, receiver attenuation changes and threat characteristic changes are available to the WSO.
The system is highly reprogrammable, on the ground and in the air, which allows it to adapt to any scenario in minimum time. The receiver continually observes the entire environment to detect most conventional threats at a moderate sensitivity. For those emitters that require higher sensitivity for detection, the receiver employs a directed, high sensitivity search routine that is programmed by the user for maximum effectiveness.
The TWF provides a Pulsed Doppler (PD) radar function to detect any missile threatening the bomber from the aft sector. If a missile is detected, the system provides immediate warning to the crew for evasive action, and can automatically dispense RF and IR decoys to counter the threat.

Operational status

Production of 100 systems is complete and the system is installed in the B-1B. In February 1991, AIL was awarded a US$16.5 million contract for AN/ALQ-161A systems for the Northrop B-2 and an additional US$5.491 million to upgrade systems for the B-1B.
The B-1B Defensive Systems Upgrade Program (DSUP), reportedly being applied to the whole B-1B fleet, includes Block B, C, D and E enhancements to the core ALQ-161A system. The details of Block B upgrades are unknown. Upgrades designated Block C to E are understood to involve: Block C improved direction finding and sector blanking (initiated in 1996); Block D improved jamming capability (to begin in 1999); Block E improved emitter detection (later). During the second quarter of 2002, AIL Systems, through its parent company EDO, was awarded contracts totalling US$11.4 million from Warner Robins Air Logistics Centre, to provide continuing support and performance improvement for the AN/ALQ-161A for the B-1B fleet, which included integration work for the AN/ALE-50 Towed Radar Decoy (TRD) system.
The AN/ALQ-161A was reported to have been `reliable and effective' during operations in Afghanistan and the most recent Gulf War over Iraq.
Perhaps as a result of this performance, on the 22 May 2003 EDO announced it had received two further B-1B programme awards in support of the AN/ALQ-161, totalling some US$11.2 million, enabling the US Air Force to maintain and upgrade the bomber's defensive suite. The first award was for 12 months of engineering support under a new 10-year ID/IQ (Indefinite Delivery/Indefinite Quantity) contract. The task covers sustaining engineering services, which include software-test facility support, mission-data optimisation analysis, technical studies and analyses, software testing and diminishing manufacturing sources studies. The second award covers continued support for subassembly repairs for 6 to 24 months.


AIL Systems Inc.


The AIL AN/ALQ-161 system for the B-1B

The AN/ALQ-161 system has undergone continuous upgrade to maintain the combat effectiveness of the B-1B, including work to integrate the AN/ALE-50 Towed Radar Decoy (TRD) system (US Air Force)

AN/ALQ-161 functional schematic

© 2005 Jane's Information Group Edward Downs

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