Boeing RC-135

At least four KC-135A tankers were converted into makeshift reconnaissance platforms with no change of Mission Design Series (MDS) designation. KC-135As 55–3121, 55–3127, 59–1465, and 59-1514 were modified beginning in 1961. That year the Soviet Union announced its intention to detonate a 100 megaton thermonuclear device on Novaya Zemlya, the so-called Tsar Bomba. A testbed KC-135A (55-3127) was modified under the Big Safari program to the SPEED LIGHT BRAVO configuration in order to obtain intelligence information on the test. The success of the mission prompted conversion of additional aircraft for intelligence gathering duties.

Not to be confused with the CFM F108-powered KC-135R tanker, the KC-135R MDS was applied in 1963 to the three KC-135A reconnaissance aircraft under the Rivet Stand program. The three aircraft were 55–3121, 59–1465, and 59–1514; a fourth, serial no. 58–0126, was converted in 1969 to replace 1465 which had crashed in 1967. Externally the aircraft had varied configurations throughout their careers, but generally they were distinguished by five "towel bar" antennas along the spine of the upper fuselage and a radome below the forward fuselage. The first three aircraft retained the standard tanker nose radome, while 58-0126 was fitted with the 'hog nose' radome commonly associated with an RC-135. A trapeze-like structure in place of the refueling boom which was used to trail an aerodynamic shape housing a specialized receiver array (colloquially known as a "blivet") on a wire was installed. This was reported to be used for "Briar Patch" and "Combat Lion" missions. There were four small optically flat windows on each side of the forward fuselage. On some missions a small wing-like structure housing sensors was fitted to each side of the forward fuselage, with a diagonal brace below it. With the loss of 59–1465, KC-135A 58-0126 was modified to this standard under the Rivet Quick operational name. All four aircraft have now been lost or converted to KC-135R tanker configuration. They are among the few KC-135 tankers equipped with an aerial refueling receptacle above the cockpit, a remnant of their service as intelligence gathering platforms.

KC-135R 55-3121 was modified in 1969 by Lockheed Air Services to the unique KC-135T configuration under the Cobra Jaw program name. Externally distinguished by the 'hog nose' radome, the aircraft also featured spinning "fang" receiver antennas below the nose radome, a large blade antenna above the forward fuselage, a single 'towel bar' antenna on the spine, teardrop antennas forward of the horizontal stabilizers on each side, and the trapeze-like structure in place of the refueling boom. The aircraft briefly carried nose art consisting of the Ford Cobra Jet cartoon cobra. It was later modified into an RC-135T Rivet Dandy.

Four RC-135As (63-8058 through 8061) were photo mapping platforms used briefly by the Air Photographic & Charting Service, based at Turner Air Force Base, Georgia and later at Forbes Air Force Base, Kansas as part of the 1370th Photographic Mapping Wing. The mission was soon assumed by satellites, and the RC-135As were de-modified and used in various other roles, such as staff transport and crew training. In the early 1980s they were further converted to tankers with the designation KC-135D (of the same basic configuration as the KC-135A and later E, plus some remaining special mission equipment). Due to delays in reinstalling their original equipment, the RC-135As were the last of the entire C-135 series delivered to the USAF. The Boeing model number for the RC-135A is 739–700.[3]

The as-delivered version of the RC-135. The RC-135B was never used operationally, as it had no mission equipment installed by Boeing. The entire RC-135B production run of ten aircraft was delivered directly to Martin Aircraft in Baltimore, Maryland for modification and installation of mission equipment under the Big Safari program. Upon completion, the RC-135Bs were re-designated RC-135C. The Boeing model number for the RC-135B is 739-445B.[3]

Modified and re-designated RC-135B aircraft used for strategic reconnaissance duties, equipped with the AN/ASD-1 electronic intelligence (ELINT) system. This system was characterized by the large 'cheek' pods on the forward fuselage containing the Automated ELINT Emitter Locating System (AEELS – not Side Looking Airborne Radar – SLAR, as often quoted), as well as numerous other antennae and a camera position in the refuelling pod area of the aft fuselage. The aircraft was manned by two pilots, two navigators, numerous intelligence gathering specialists, inflight maintenance technicians and airborne linguists. When the RC-135C was fully deployed, SAC was able to retire its fleet of RB-47H Stratojets from active reconnaissance duties. All ten continue in active service as either RC-135V Rivet Joint or RC-135U Combat Sent platforms.

The RC-135Ds, originally designated KC-135A-II, were the first reconnaissance configured C-135s given the "R" MDS designation, although they were not the first reconnaissance-tasked members of the C-135 family. They were delivered to Eielson Air Force Base, Alaska in 1962 as part of the Office Boy Project. Serial numbers were 60–0356, 60–0357, and 60–0362. The aircraft began operational missions in 1963. These three aircraft were ordered as KC-135A tankers, but delivered without refueling booms, and known as "falsie C-135As" pending the delivery of the first actual C-135A cargo aircraft in 1961. The primary Rivet Brass mission flew along the northern border of the Soviet Union, often as a shuttle mission between Eielson and RAF Upper Heyford, Oxfordshire, and later RAF Mildenhall, Suffolk, UK. The RC-135D was also used in Southeast Asia during periods when the RC-135M (see below) was unavailable. In the late 1970s, with the expansion of the RC-135 fleet powered by TF33 turbofan engines, the RC-135Ds were converted into tankers, and remain in service as receiver-capable KC-135Rs.[14]

Originally designated C-135B-II, project name Lisa Ann, the RC-135E Rivet Amber was a one-of-a-kind aircraft equipped with a large 7 MW Hughes Aircraft phased-array radar system.[15] Originally delivered as a C-135B, 62-4137 operated from Shemya Air Force Station, Alaska from 1966 to 1969. Its operations were performed in concert with the RC-135S Rivet Ball aircraft (see below). The radar system alone weighed over 35,000 pounds and cost over US$35 million (1960 dollars), making Rivet Amber both the heaviest C-135-derivative aircraft flying and the most expensive Air Force aircraft for its time. This prevented the forward and aft crew areas from having direct contact after boarding the aircraft. The system could track an object the size of a soccer ball from a distance of 300 miles (480 km), and its mission was to monitor Soviet ballistic missile testing in the reentry phase. The power requirement for the phased array radar was enormous, necessitating an additional power supply. This took the form of a podded Lycoming T55-L5 turboshaft engine in a pod under the left inboard wing section, driving a 350 kVA generator dedicated to powering mission equipment.[16] On the opposite wing in the same location was a podded heat exchanger to permit cooling of the massive electronic components on board the aircraft. This configuration has led to the mistaken impression that the aircraft had six engines. On June 5, 1969, Rivet Amber was lost at sea on a ferry flight from Shemya to Eielson AFB for maintenance, and no trace of the aircraft or its crew was ever found.[17]

The RC-135M was an interim type with more limited ELINT capability than the RC-135C but with extensive additional COMINT capability. They were converted from Military Airlift Command C-135B transports, and operated by the 82d Reconnaissance Squadron during the Vietnam War from Kadena AB, gathering signals intelligence over the Gulf of Tonkin and Laos with the program name Combat Apple (originally Burning Candy).[18] There were six RC-135M aircraft, 62–4131, 62–4132, 62–4134, 62–4135, 62-4138 and 62–4139, all of which were later modified to and continue in active service as RC-135W Rivet Joints by the early 1980s.[19]

Rivet Ball was the predecessor program to Cobra Ball and was initiated with a single RC-135S (serial 59–1491, formerly a JKC-135A) on December 31, 1961. The aircraft first operated under the Nancy Rae project as an asset of Air Force Systems Command and later as an RC-135S reconnaissance platform with Strategic Air Command under project Wanda Belle. The name Rivet Ball was assigned in January 1967. The aircraft operated from Shemya AFB, Alaska. Along with most other RC-135 variants, the RC-135S had an elongated nose radome housing an S band receiving antenna. The aircraft was characterized by ten large optically flat quartz windows on the right side of the fuselage used for tracking cameras. Unlike any other RC-135S, Rivet Ball also had a plexiglass dome mounted top center on its fuselage for the Manual Tracker position. It holds the distinction of obtaining the very first photographic documentation of Soviet Multiple Reentry vehicle (MRV) testing on October 4, 1968. On January 13, 1969 Rivet Ball was destroyed in a landing accident at Shemya when it overran the runway with no fatalities.[15][20]

Two Cobra Ball aircraft on the flightline at Offutt Air Force Base, Nebraska in 2001.

The RC-135S Cobra Ball is a measurement and signature intelligence MASINT collector equipped with special electro-optical instruments designed to observe ballistic missile flights at long range. The Cobra Ball monitors missile-associated signals and tracks missiles during boost and re-entry phases to provide reconnaissance for treaty verification and theater ballistic missile proliferation. The aircraft are extensively modified C-135Bs.[4] The right wing and engines are traditionally painted black to reduce sun glare for tracking cameras.[21]

There are three aircraft in service and they are part of the 55th Wing, 45th Reconnaissance Squadron based at Offutt Air Force Base, Nebraska. Cobra Ball aircraft were originally assigned to Shemya and used to observe ballistic missile tests on the Kamchatka peninsula in conjunction with Cobra Dane and Cobra Judy. Two aircraft were converted for Cobra Ball in 1969 and following the loss of an aircraft in 1981 another aircraft was converted in 1983. The sole RC-135X was also converted into an RC-135S in 1995 to supplement the other aircraft.

KC-135T 55-3121 was modified to RC-135T Rivet Dandy configuration in 1971. It was used to supplement the RC-135C/D/M fleet, then in short supply due to ongoing upgrades requiring airframes to be out of service. It operated under the Burning Candy operational order. In 1973 the aircraft's SIGINT gear was removed and transferred to KC-135R 58–0126, resulting in 55-3121 assuming the role of trainer, a role which it fulfilled for the remainder of its operational existence. Externally the aircraft retained the 'hog nose' radome and some other external modifications, but the aerial refueling boom and trapeze below the tail were removed, and it had no operational reconnaissance role. In this configuration it operated variously with the 376th Strategic Wing at Kadena AB, Okinawa, the 305th AREFW at Grissom AFB, Indiana, and the 6th Strategic Wing at Eielson AFB, Alaska. In 1982 the aircraft was modified with Pratt & Whitney TF33-PW102 engines and other modifications common to the KC-135E tanker program, and returned to Eielson AFB. It crashed while on approach to Valdez Airport, Alaska on 25 February 1985 with the loss of three crew members. The wreckage was not found until August 1985, six months after the accident.[22]

Combat Sent aircraft in flight with its unique nose cone, wingtips, and tail

The RC-135U Combat Sent is designed to collect technical intelligence on adversary radar emitter systems. Combat Sent data is collected to develop new or upgraded radar warning receivers, radar jammers, decoys, anti-radiation missiles, and training simulators.[4]

Distinctly identified by the antenna arrays on the fuselage chin, tailcone, and wing tips, three RC-135C aircraft were converted to RC-135U (63-9792, 64–14847, & 64-14849) in the early 1970s. 63-9792 was later converted into a Rivet Joint in 1978, and all aircraft remain in service based at Offutt Air Force Base, Nebraska. Minimum crew requirements are 2 pilots, 2 navigators, 3 systems engineers, 10 electronic warfare officers, and 6 area specialists.[23]

RC-135 Rivet Joint

The RC-135V/W is the USAF's standard airborne SIGINT platform. Missions flown by the RC-135s are designated either Burning Wind or Misty Wind.[24] Its sensor suite allows the mission crew to detect, identify and geolocate signals throughout the electromagnetic spectrum.[25] The mission crew can then forward gathered information in a variety of formats to a wide range of consumers via Rivet Joint's extensive communications suite. The crew consists of the cockpit crew, electronic warfare officers, intelligence operators, and airborne systems maintenance personnel. All Rivet Joint airframe and mission systems modifications are performed by L-3 Communications in Greenville, Texas, under the oversight of the Air Force Materiel Command.[4][25]

All RC-135s are assigned to Air Combat Command. The RC-135 is permanently based at Offutt Air Force Base, Nebraska, and operated by the 55th Wing, using various forward deployment locations worldwide.[25]

Under the "BIG SAFARI" program name, RC-135Vs were upgraded from the RC-135C "Big Team" configuration. RC-135Ws were originally delivered as C-135B transports, and most were modified from RC-135Ms. This is the only difference between the V and W variants; both carry the same mission equipment. For many years, the RC-135V/W could be identified by the four large disc-capped MUCELS antennas forward, four somewhat smaller blade antennae aft and myriad of smaller underside antennas. Baseline 8 Rivet Joints (in the 2000s) introduced the first major change to the external RC-135V/W configuration replacing the MUCELS antennas with plain blade antennas. The configuration of smaller underside antennas was also changed significantly.

British RC-135W lands at RAF Waddington in May 2014

The United Kingdom bought three KC-135R aircraft for conversion to RC-135W Rivet Joint standard[1] under the Airseeker project.[26] Acquisition of the three aircraft was budgeted at £634m, with entry into service in October 2014.[27] The aircraft formed No. 51 Squadron RAF, based at RAF Waddington along with the RAF's other ISTAR assets. They are expected to remain in service until 2045.

Previously, the Royal Air Force had gathered signals intelligence with three Nimrod R1 aircraft,.[7] When the time came to upgrade the maritime Nimrods to MRA4 standard, Project Helix was launched in August 2003 to study options for extending the life of the R1 out to 2025.[28] The option of switching to Rivet Joint was added to Helix in 2008,[28] and the retirement of the R1 became inevitable when the MRA4 was cancelled under the UK's 2010 defence review. The R1's involvement over Libya in Operation Ellamy delayed its retirement until June 2011.

Helix became Project Airseeker, under which three KC-135R airframes were converted to RC-135W standard by L-3 Communications. L-3 also provides ongoing maintenance and upgrades under a long-term agreement. The three airframes are former United States Air Force KC-135Rs, all of which first flew in 1964 but were modified to the latest RC-135W standard before delivery. The three airframes on offer to the UK are the youngest KC-135s in the USAF fleet.[29] As of September 2010 the aircraft had approximately 23,200 flying hours, 22,200 hours and 23,200 hours.[30]

51 Sqn personnel began training at Offutt in January 2011 for conversion to the RC-135.[31] The first RC-135W (ZZ664) was delivered ahead of schedule to the Royal Air Force on 12 November 2013, for final approval and testing by the Defence Support and Equipment team prior to its release to service from the UK MAA. The second (ZZ665) was delivered on 4 September 2015 and the third (ZZ666) in June 2017; the latter entered operational service in December 2017.[32][33]

The sole RC-135X Cobra Eye was converted during the mid-to-late-1980s from a C-135B Telemetry/Range Instrumented Aircraft, serial number 62–4128, with the mission of tracking ICBM reentry vehicles.[34][35] In 1993, it was converted into an additional RC-135S Cobra Ball.[18][36]

Three aircraft are in service for crew training, and lack fully functional mission equipment. One TC-135S (62-4133) provides training capability for the Cobra Ball mission, and is distinguishable from combat-ready aircraft by the lack of cheeks on the forward fuselage. It was converted from an EC-135B in 1985 following the crash of the former RC-135T 55–3121, which had been used as a trainer up to that point. In addition, two TC-135Ws (62-4127 and 4129) serve as training aircraft primarily for the Rivet Joint mission, but can also provide some training capability for RC-135U Combat Sent crews. They carry considerably fewer antennas than the fully equipped aircraft, but are otherwise similar in appearance to other Rivet Joint aircraft.