Lightning Reflexes


Enhancements to the F-35’s electronic warfare systems will focus on software, firmware and hardware should be completed by 2024.

The contract won in August by BAE Systems to take the Lockheed Martin F-35A/B/C Lightning-II combat aircraft’s AN/ASQ-239 self-protection system to the Block-IV configuration will see a host of improvements added to this apparatus. The AN/ASQ-239 has evolved through several incarnations since BAE Systems commenced its supply of the ensemble in 2005. A number of details regarding the AN/ASQ-239’s architecture exist in the public domain. It is known to contain a radar warning receiver, an electronic support measure to identify and locate hostile emitters, and high gain electronic countermeasures for jamming. The AN/ASQ-239 is said to be capable of both pre-emptive and reactive electronic attack, using both expendables such as chaff, and pre-loaded jamming algorithms to counter specific RF (Radio Frequency) threats. One useful feature is that the equipment can correlate the location of emitters with the aircraft’s Northrop Grumman AN/APG-81 X-band (8.5 gighaertz/GHz to 10.68GHz) fire control radar and Lockheed Martin AN/AAQ-30 optronics system enabling a positive identification of the emitter. Likewise, emitter threat information can be share between F-35s, and other aircraft, using the jet’s Northrop Grumman AN/ASQ-242 Communications, Navigation and Identification system. This carries the Tactical Datalinks (TDL) necessary for the aircraft to share such information, notably the North Atlantic Treaty Organisation’s Link-16 (960 megahertz to 1.215GHz) TDL protocol.

This diagram indicates the placement and capabilities of some of the F-35’s self-protection systems. These are now being enhanced by BAE Systems’ Block-IV upgrade.

The aircraft has radar warning receivers on the leading edge of its wings covering frequencies of bands 2, 3 and 4. Two band-3/4 RWRs are positioned close to the wingtips on the aft wing trailing edges and on the aft horizontal stabilisers, with additional RWRs covering band 2 either side of the aircraft’s exhaust. These provide the aircraft with full 360 degree coverage. Although the aircraft is presently configured to detect RF emissions in bands 2, 3 and 4, there is growth potential for this to encompass band-5 threats in the future. Although no details appear to have been publicly released it is thought that the AN/ASQ-239 can detect hostile radars transmitting in a two gigahertz to 20GHz waveband. Enhancements to the AN/ASQ-239 are being performed via a series of block enhancements which confer increasing levels of capability onto the self-protection system.

Todd Caruso, BAE Systems’ director of business development for F-35 solutions, told Armada Analysis that the Block-IV upgrades for the AN/ASQ-239 will mainly focus on “more complex algorithms” for the system’s software alongside improvements to computational speed and power, and reductions in equipment weight, known in the trade as software, firmware and hardware improvements. The block upgrades are being added as part of the F-35’s Continuous Capability, Development and Delivery (C2D2) cycle; a process by which enhancements are added to the aircraft as they mature.

Although BAE Systems commenced work on the Block-IV enhancements in 2016, this recent contract will see these improvements being conferred on the aircraft with the upgrades expected to conclude in 2024. Mr. Caruso added that Block-IV improvements for the AN/ASQ-239 will be retrofitted onto F-35s declared operational, with the capabilities being added to new jets as and when they are built. Block-4 will by no means be the final enhancement to the AN/ASQ-239. Mr. Caruso continues that “the F-35 will continue to modernize its mission systems throughout the lifecycle of the platform. As new capabilities are developed and additional requirements are added to the program, the C2D2 process will bring new capabilities to the jet.”

by Dr. Thomas Withington