Boeing RC-135As soon as the original KC-135A Stratotanker entered service it was identified as an ideal airframe that could be adapted to replace the ageing fleet of RB-47 Stratojet aircraft. The first modifications to four KC-135A tankers were CIA sponsored under the codenames ‘Iron Lung’ and ‘Briar Patch’. Known as KC-135R these aircraft were equipped for SIGINT duties, in particular for gathering data from Soviet rocket tests. The aircraft could be easily identified by a prominent antenna fence installed along the top fuselage centreline and camera windows on both sides of the fuselage. Some aircraft equipped with a capsule packed with listening gear, which was then towed behind the aircraft on a 12,000ft cable.
Among the last C-135 aircraft built were 4 aircraft modified for photographic reconnaissance duties. The aircraft were ordered to replace sixteen RB-50 Superfortresses which were engaged in aerial mapping duties. Known as the RC-135A Pacer Swan the aircraft were equipped with a camera compartment in the forward body fuel tank. After operating for over 10 years from Turner AFB, Georgia and Forbes AFB, Kansas the aircraft were converted to tanker configuration in the late 1970’s.
The RC-135B/C was the first C-135 built specifically by Boeing as a reconnaissance platform. The ten aircraft delivered were the last of the C-135 series and were known initially as the RC-135B. However, all the aircraft were delivered direct from Boeing to Glenn Martin where they were stored. Under the Big Team conversion plan the aircraft were modified, re-designated as the RB-135C and delivered to the 55th SRW at Offutt AFB to replace the units RB-47Hs. A camera was installed in the boom operators compartment, a large cheek-mounted SLAR fairing on the forward fuselage and a highly capable SIGINT suite at the heart of which lay the AN/ASD-1 automatic reconnaissance unit and the QRC-259 superheterodyne receiver. Two aircraft were later converted to RC-135Us and the remaining 8 became RC-135Vs. In July 1961, under Project ‘Speed Light’, a KC-135 was specially modified to observe a Soviet nuclear test. The aircraft subsequently flew close enough to a projected 100 megaton bomb test at Nafiazimi in the Barents Sea for the paint to be scorched. Subsequent analysis proved that the bomb was ‘only’ 58 megatons – the long-term effect on the crew of this sortie is unknown.
The next adaptation to the KC-135 resulted in the RC-135D RIVET BRASS, these aircraft were allocated to the 6th Strategic Wing based at Eielson AFB in Alaska where they operated on the eastern fringes of the Soviet Union. As well as carrying an extensive array of SIGINT equipment, the RC-135D was equipped with a variety of ‘Side Looking Airborne Radar’ (SLAR) housed in fairings along the side of the forward fuselage.
The 6th Strategic Wing at Eielson also received the next variant the RC-135E RIVET AMBER. One C-135B aircraft, 62-4137 nicknamed 'Lisa Ann', was converted to this configuration in 1963 to fly reconnaissance missions from Shemya AFB, targeted against the Soviet re-entry range off the Kamchatka Peninsula. The right forward door and fuselage were replaced by a 12 x 20 foot fibreglass panel built by Goodyear. Inside the forward fuselage Hughes installed the largest and most powerful airborne radar ever built with a 7.5 megawatts peak power. Each pulse of energy was pointed by a computer generated word which determined the frequency shift and phase of the signal. The system gathered trajectory information prior to and during re-entry of ballistic warheads, as well as radar cross-section data; a camera port also allowed photography of missile re-entry vehicles. The aircraft was only operated from Eielson, had a tragically short service life and crashed in the Bering Strait on 5th June 1969 with the loss of all 19 crew. Click here to read a detailed report into the circumstances surrounding the loss of Rivet Amber - submitted by Ron Strong.
During the Vietnam War six RC-135M RIVET CARD aircraft of the 82nd SRS were tasked for SIGINT missions against the Chinese mainland as Soviet targets in the Petropavlovsk region. Carrying a large crew of ‘Ravens’, these ‘Combat Apple’ sorties were flown in the Gulf of Tonkin and often lasted 19 hours with 12 hours spent ‘on-station’. The ELINT and COMINT gathered by these aircraft were vital, allowing other US aircraft to be warned of MiG and SAM activity – on occasions these aircraft also controlled and co-ordinated aircrew rescue activity. The 6 aircraft were extensively re-built under the BIG SAFARI programme during early 1980s and re-designated RC-135W RIVET JOINT.
Five C-135B aircraft were converted to the RC-135S RIVET BALL / COBRA BALL configuration with a wide variety of receivers and antennas all designed to collect ‘TELINT’ – telemetry from Soviet rocket launches. In the original configuration the aircraft also had a series of camera portholes along the starboard side of the front fuselage. To ensure reflections did not affect photography, the upper surface of the starboard wing was painted black. The aircraft were operated by the 24th SRS from Eielson AFB, Alaska with a detachment to Shemya AB in the Aleutian Islands. Note: The ‘Cobra’ codename was used to identify various systems used since 1961 to monitor Soviet missile tests; the phased array radar on Shemya Island was Cobra Dane, a ship, the ‘Observation Island’, equipped with a variety of long-range radar’s was Cobra Judy and an Over The Horizon (OTH) radar at Orford Ness in Suffolk, England Cobra Mist. One Cobra Ball aircraft crashed at Shemya AB, Alaska in 1981 killing 6 crewmen. The latest version of the Cobra Ball, delivered in 1999, can take observations from both sides of the aircraft. These 3 aircraft operate with the 55th SRS Wg based at Offut AB Nebraska.
Three RC-135C aircraft were converted into the RC-135U COMBAT SENT+ configuration. These aircraft were fitted with highly classified ELINT equipment along with a huge SLAR and were particularly active during the Vietnam War. One aircraft was later re-configured and re-designated as an RC-135V. Two Combat Sent equipped aircraft are still in service with the 55th SRW at Offut AFB, Nebraska and take very precise measurements of emissions of foreign electronic equipment.
Seven RC-135C airframes and one RC-135U were converted into the RC-135V RIVIT JOINT configuration. This variant was the first to incorporate both cheek antenna fairings and a hog nose radome. A variety of antennas also protrude out the top and bottom of the fuselage.
All 6 RC-135M aircraft were converted to RC-135W RIVIT JOINT configuration and 3 other aircraft were also converted. Like the RC-135V, this aircraft has large cheek antennas and a hog nose. Fours large MUCELS antennas are also mounted on the bottom of the fuselage. Sixteen Rivet Joint aircraft, specialising in signals and communications intelligence, operate with the 55th SRW at Offut AFB Nebraska.
One EC135B was rebuilt and designated RC-135X COBRA EYE. The equipment installed was intended to gather imagery of Soviet missile tests as part of the SDI programme. The equipment was designed to optically identify and discriminate Soviet ballistic missile re-entry vehicles in mid-course. After a 6 year development programme the aircraft was delivered to the 24th SRS at Eielson AFB on 16 July 1989 and it generally operated from Shemya AB observing Soviet ballistic missile tests. On 22 Feb 93 the aircraft was withdrawn from use and placed in long-term storage. In 1999 this aircraft was re-configured and entered service as a RC-135S Cobra Ball.
Although the 16 RC-135V/W Rivet Joint aircraft still in service are old airframes, the electronic interior is state of the art for intelligence gathering and the equipment is upgraded every 3 or 4 years. Originally the aircraft’s role was entirely passive – simply listening in to radio traffic. Now the role encompasses the interception, altering and reinsertion of every kind of electronic messages and continues to grow as C3 systems become ever more complex.
Israel uses 3 converted B-707 aircraft as dual ELINT/tankers. These aircraft are designated EC/RC-707 and are operated by the 134th Squadron from Tel Aviv’s International Airport. As part of the Middle East Peace Accord, Israel hopes to procure between 3 and 6 aircraft of Rivet Joint capability from the USA.
The USAF RC-135s continue to operate and perhaps surprisingly there is even more demand for their operations than during the last years of the Cold War.. The fleet of RC-135 RIVET JOINT aircraft is logging so many hours that congressional committees authorised funds to expand and upgrade the fleet in 1995.
RIVET JOINTS remain amongst the most secret of all American covert operations. They are intercepting communications from Bosnia to the Middle East. With their state-of-the -art electronics they conduct a wide range of intelligence gathering from identifying hostile Bosnian Serb radar’s and surface-to-air missile sites through to monitoring Indian missile tests. The aircraft are part of the United States comprehensive intelligence gathering operating also involving spy satellites, AWACS and U-2 aircraft . Their intelligence is carefully sifted to provide the one the ground commanders with an overview. It is worth noting that here were no RIVET JOINTS operating on 2nd June 1995 when the F-16 piloted by Air Force Capt. Scott O'Grady was downed by a Serb SA-6. A RIVET JOINT in the area would have provided immediate warning of that the SA-6's radar was tracking F-16. The limited number of RC-135s available for Bosnia missions meant that no plane was in orbit when the F-16 was patrolling . In an attempt to prevent a repetition RC-135 missions were lengthened from eight to ten hours.
According to an Air Combat Command spokesman, RIVET JOINT are among the Air Force's most heavily deployed aircraft, and the fleet have 153 days overseas in 1995 up eight days from 1994. During the Gulf War in 1990, RIVET JOINT aircraft were on a 24 hour operation along the Saudi-Iraqi border ". At least two RC-135s remain station. In February the 1000th RC-135 mission was flown, supporting United States, British and French forces, enforcing the UN sanctions against Iraq. RC-135s flying from RAF Mildenhall, England, have been used to collect intelligence on Bosnian targets and pick up the rescue beacons from U.S. and NATO fliers - as they did in April 1993, when they detected the signal from a downed French pilot. An example of its quick deployment capability, in early January 1994, a COBRA BALL aircraft deployed off the Bay of Bengal within 48 hours from its base in Diego Garcia. The plane monitored any Indian test of its medium range Agni missile that took place over the bay - such as the one launched in February 1994. Aircraft have been stationed on Souda Bay, Greece. When deployed, they can monitor tests of Israeli and Iranian missiles.
In August 1995 a COBRA BALL was sent to monitor Chinese missile tests near Taiwan. While refusing to discuss specifics of COBRA BALL deployments, Siniscalchi noted the planes "had emerged to be more of a world-wide type of platform". In contrast to the RIVET JOINT and COMBAT SENT planes, COBRA BALL sorties have decreased significantly from 200 in 1988 to less than 100 per year under present circumstances. The Senate Select Committee on Intelligence, in its 1996 authorisation report, expressed its concern with the RIVET JOINT's "extraordinary number of annual flight hours" and recommended an authorisation of $79.5 million to begin re-engining the fleet. It also instructed the Defence Airborne Reconnaissance Office to budget the funds required to continue re-engining in "fiscal year 1997 and beyond".
The comment reflects the Select Committee's concern, shared by the Senate Armed Services Committee, that DARO is interested in new development programmes, instead of upgrading current reconnaissance platforms. The armed services panel in its fiscal 1996 authorisation bill, earmarked $79.5 million to transform two EC-135 aircraft into RIVET JOINT aircraft - noting the aircraft's "critical role". The House Appropriations Committee agreed, while the House Permanent Select Committee on Intelligence authorised funding for converting only one plane.
The Senate Armed Services Committee also recommended an additional expenditure of $28 million to "initiate the migration of COBRA BALL medium wave infrared acquisition technology "to the RIVET JOINT fleet. The committee viewed this as cost-effective means of improving theatre-missile defence long-range surveillance, warning and rapid cueing for attack operations as well as impact prediction for both active and passive defence measures. Re-engining was first proposed in a 1989 classified General Accounting Office report and again in a 1992-unclassified version. The latter report noted that 100 RC-135 missions were flown each month, with about 18,000 hours of flying time being logged annually. Re-engining would involve replacing the four TF-33 engines on each plane with CFM-56 engines.
According to the GAO's 1992 report, "New RC-135 Aircraft Engines Can Reduce Cost and Improve Performance." Re-engining the entire 21 aircraft fleet would cost $602 million more than minimum upgrade of the TF-33 engines required to keep the RC135s flying until 2020. However, there would be a projected cost savings of almost $1.5 billion, when factoring in the money saved on fuel, maintenance and tanker support. Installation of the CFM-56 engines would increase aircraft reliability and unrefuelled flight time by as much as four hours, while decreasing pollution. There would also be several operational advantages to re-engining, according to GAO. Overseas basing options, presently restricted to airfields with 10,000 foot runways, would be expanded to include those aiefields with 8,000 foot runways. In its 1992 report, GAO noted that there was only one military airfield in the Mediterranean ( Souda Bay, Greece) with a 10,000 foot runway.
The new engines would also allow the aircraft to fly at 40,000 feet rather than its present 35,000 feet. The additional 5,000 feet would enhance performance of the aircraft’s intelligence collection sensors by expanding their field of view and area coverage. The expanding field of view also would allow the planes to conduct surveillance operations at greater stand-off ranges, beyond the reach of surface-to-air weapons.