The RC-135W Rivet Joint is the USAF’s main SIGINT platform. Now the RAF will be operating them too.
The Royal Air Force’s Nimrod aircraft have been a familiar sight for decades, and anyone with even a slight interest in UK defence knew that their role was maritime reconnaissance and anti-submarine warfare. Equipped with sonobuoy launchers and a Magnetic Anomaly Detector boom behind the tail they were capable of finding submerged submarines and attacking them with torpedoes and depth charges. A powerful surface search radar could find ships across a huge swathe of ocean, and Harpoon missiles could attack them if required. Nimrods could even drop life rafts and other survival equipment to survivors in the water, and one was always on standby for search and rescue operations. The UK’s air sea rescue helicopters operate to about 300 miles offshore, but if required the Nimrods could reach out thousands of miles and drop their Lindholme Gear rescue packs to survivors far out in the Atlantic.
In total 49 Nimrods were built, mostly in the MR1 and MR2 variants. Three of them looked slightly different, though. In most respects they looked like an MR2, but they lacked the long MAD boom at the tail. They started operating in 1974 and flew out of RAF Waddington in Lincolnshire. When asked the RAF said they were radar calibration aircraft. They kept saying that until after the end of the Cold War, but then the truth came out.
These three aircraft, officially known as the Nimrod R1, were signals intelligence platforms. The weapons bay was filled with rotating dish antennas, and more antennas were concealed in the tail cone and the tips of the wing-mounted fuel tanks. A flight crew of four ran the aircraft while up to 25 systems operators collected and analysed information from the sensors. During the Cold War the R1s collected information on Warsaw Pact radio and radar transmissions throughout Europe, and one of them was watching Argentina during the Falklands War in 1982. They continued to operate until 2011, when they joined the rest of the Nimrod fleet in retirement.
The Nimrod was an old design, and couldn’t be kept in the air forever. Signals intelligence is a key capability, though, and has to be maintained. The RAF has now chosen a replacement for this role. The R1’s equivalent in the US Air Force is the Boeing RC-135W Rivet Joint, and three of these have been ordered with delivery starting in 2014. In RAF service they will be called the Airseeker and are likely to be designated R2.
Like the Nimrod the RC-135W is based on a converted airliner, in this case the Boeing 707. The USAF has been operating a series of 707 variants since 1965, starting with the C-135 transport then buying a large number of KC-135 tankers. RC-135 reconnaissance versions started appearing in 1971 and a range of sub-variants was quickly developed for different functions. The Rivet Joint is a signals intelligence platform. There are two models; the RC-135Vs were modified from RC-135Cs while the RC-135Ws started life as C-135B transports, becoming RC-135M Rivet Card ELINT gatherers during the Vietnam War then finally being converted to Rivet Joints. Both models have basically the same electronics fit, which was updated in the early 2000s.
The USAF doesn’t plan to sell any of its Rivet Joints – in fact it’s expanding the fleet – so the RAF’s aircraft will be converted from KC-135 tankers. The aircraft selected are the three newest in the tanker fleet and they will be converted to the latest RC-135W standard for full compatibility with USAF Rivet Joints. The rebuild will include a complete cabling replacement and new glass cockpits. The sensor package will allow them to intercept, locate and record signals across a wide range of the electromagnetic spectrum, and a crew of up to 27 is likely to include Intelligence Corps operators for real-time analysis of intercepts.
Although there are no plans right now to fit the Airseekers with RAF refuelling equipment they will be able to carry out missions of over 12 hours, and of course they can use USAF tankers when available. They will be able to slot effortlessly into USAF SIGINT operations, which will mean a big increase in coverage during coalition operations. A significant point here is that the Rivet Joint’s technology has never been exported and the RAF will be the first non-US operator. The list of countries who would be trusted with the system is very short – Australia, Canada and maybe Japan – so the RAF’s position as a major partner looks secure for a while longer.