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Boeing KC-135 Stratotanker
COMMON VARIANTS

C-135 Stratolifter

Primary Role: Strategic Airlift/Staff Transport

Derived from Boeing's prototype 707 jet airliner in the early 1950s, the versatile C-135 has been a visible fixture of the U.S. Air Force since the first one was acquired in August 1956. Although most of the 820 units were developed as KC-135A Stratotankers for the air refueling mission, they have also performed numerous transport and special-duty functions. Forty-five base-model aircraft were built as C-135A or C-135B transports, with tanking equipment excluded.

Fifteen C-135As, powered by J57 turbojets, were built. In later years, almost all were upgraded with TF33 turbofan engines and wide-span tailplanes then redesignated C-135E. Thirty C-135Bs were built with TF33 turbofans and wide-span tailplanes from the outset, and a small number remain in service in their original form. The C-135C designation applies to three WC-135B weather reconnaissance aircraft which reverted to transport status. Most of the other C-135Bs were converted to various special mission variants following their service with the Military Airlift Command (MAC).

C-135C "Speckled Trout"

Although most of the remaining C-135 aircraft are used as transports for senior military leaders and other high-ranking dignitaries, the C-135C communications aircraft serves as an aerial testbed for emerging technologies. Developmental tests using the "Speckled Trout" aircraft have demonstrated the capability to fly precision approaches using a local area differential GPS system. This modified C-135 has been fitted with a millimeter-wave camera and a new radome to test the camera's generation of video images of the forward scene in low-visibility conditions. The aircraft, which in the VIP transport role seats 14 passengers, gives the Joint Forces Air Component commander a limited ability to plan and control the simulated battle while in the air en route to the crisis area.

EC-135 'Looking Glass'

Primary Role: Airborne Command Post (ABCP)

In the early days of KC-135A production, the Strategic Air Command (SAC) identified the requirement for an Airborne Command Post (ABCP). The idea was for specially-equipped aircraft to be airborne at all times, 24 hours a day, 7 days a week, 365 days a year, in the event that SAC's underground command center was destroyed or became disabled.

The first aircraft adapted for the ABCP role were 17 TF33-engined KC-135B tankers. Dubbed the "Looking Glass", because the mission mirrored ground-based command, control, and communications, operations began on 3 February 1961. By 1964, the aircraft were considered dedicated to the role of ABCP and received the revised designation of EC-135.

The EC-135 fleet was equipped with comprehensive, high-tech communications equipment, which allows the airborne commander to link with national command authorities, theatre forces, other airborne command posts and with his assets on the ground. Its highly-trained crew and staff ensure there is always an aircraft ready to direct bombers and missiles from the air should ground-based command centers become inoperable. The crew consists of two pilots, a navigator, an airborne refueling systems operator, and several communications systems operators.

For 29 years, the EC-135s conducted continuous airborne operations, accumulating more than 281,000 accident-free flying hours — an aviation phenomenon. On 24 July 1990, "Looking Glass" aircraft ceased continuous airborne alert, but remained on ground or airborne alert 24 hours a day.

Although the Cold War is over, a radically changing world environment, proliferation of weapons of mass destruction, and political uncertainty in countries possessing nuclear weapons are just a few reasons why the "Looking Glass" mission remains as vital today as when it began in 1961. That mission however, has undergone a change of "platform."

On 25 September 1998, the Air Force officially handed over its "Looking Glass" mission of command, control, and communications of the nation's strategic nuclear forces to the Navy's E-6B "Take Charge and Move Out" (TACAMO) aircraft. The impetus for the change was the cost-savings generated by using one aircraft to do the job that had formerly been done by two.

The EC-135 performed the flying command post mission for a total of 37 years, serving as a survivable, nuclear response airborne platform. All EC-135s have been retired to the Aerospace Maintenance and Regeneration Center (AMARC) at Davis-Monthan Air Force Base, in Arizona.

NKC-135 Aerial Testbeds

Primary Role: NASA Testbed

Under various designations, including NC-135A, NKC-135A and NKC-135E, NASA and the U.S. Air Force operate a fleet of heavily-modified C-135 airframes as aerial testbeds. The type of work performed by these aircraft is greatly varied, but includes refueling tests with new aircraft types, airborne laser trials, weightlessness training for astronauts, and numerous programs involving the testing of airborne equipment and space technology.

Zero Gravity Trainer (Vomit Comet)

The NKC-135A Zero Gravity Trainer is used to fly parabolas to investigate the effects of "zero" gravity. This aircraft, designated NASA 930, is operated by the Johnson Space Center's Reduced Gravity Office in Houston, Texas.

To her crew, she's the "Weightless Wonder", to her passengers, she's the "Vomit Comet". Regardless of the name, this unusual aircraft helped the Planetary Missions and Materials Branch at the Johnson Space Center take another step closer to renewed human exploration of the moon, and beyond.

To fly on the "Comet" you must hold an Air Force Flying Class III Medical Examination card and complete an Aerospace Physiological Training course. The objective of the physiological training is to familiarize personnel who are exposed to a lowered barometric pressure with the physiological stresses encountered and how to successfully overcome these stresses.

By flying a series of "roller-coaster" parabolic maneuvers, short periods of reduced gravity are experienced onboard. Most flights are dedicated to zero-g astronaut training and equipment tests. During a "typical" mission, which lasts about two hours, the aircraft usually flies 40 parabolas. Longer flights are possible, depending on fuel and gross weight limitations. Consequently, more parabolas mean more flexing of the airframe and more stress.

Note: The NKC-135A "Vomit Comet" was used to film the zero-gravity scenes for the movie Apollo 13. Ron Howard, his crew, and the cast spent over six months on the plane to produce the movie.

Wingtip Research Aircraft

In 1979 and 1980, the Dryden Flight Research Center at Edwards AFB, California conducted a special wingtip "winglet" test program with the NKC-135. Winglets are small, nearly vertical fins installed on an airplane's wingtips to help produce a forward thrust in the vortices that typically swirl off the end of the wing, thereby reducing drag. This winglet idea was tested at Dryden on a modified KC-135A tanker loaned to NASA by the Air Force. The research showed that the winglets could increase an aircraft's range by as much as 7% at cruise speeds. The first application of NASA's winglet technology in industry was in general aviation business jets, but winglets are now being incorporated into most new commercial and military transport jets, including the C-17 Globemaster III military transport.

RC-135 Family

Primary Role: Strategic Reconnaissance

From an early date, the Boeing C-135 was recognized as an excellent airframe for various special missions. One of these was strategic reconnaissance, using the aircraft's capacious cabin to house large amounts of electronic equipment. Designated RC-135, these aircraft can be detached on a global basis to cover areas of the world where intelligence-gathering is required.

Several RC-135 versions are currently in service. Among these are three dedicated to general Signals Intelligence (Sigint) gathering. All feature large amounts of electronic recording and analyzing equipment on board, and have many aerials on the airframe, including slab-sided cheek fairings where many of the side-facing antennas are grouped. These serve the Automatic Elint Emitter Locator System (AEELS), which gathers signals from across the frequency spectrum, sifts out those of particular interest and relays data to operator stations in the cabin.

RC-135U "Combat Sent"

Two aircraft are designated RC-135U and are characterized by cheek fairings and additional fairings in the chin, boomer, wingtip, tailcone and fin-top positions. Until 1991 they were fitted with "towel rail" antennas above the cheek fairings, but these have been removed. The RC-135Us are believed to have special purposes within the Sigint fleet, and may also be used to trial new equipment.

RC-135V/W "Rivet Joint"

Eight aircraft are designated RC-135V, while six are the essentially similar RC-135W variant. These are the workhorses of the Sigint fleet and are distinguished by having extended "thimble" noses and large plate aerials under the center-section. External differences between the two variants are restricted to a lengthened cheek fairing on the W-model, which also lacks auxiliary air intakes on its engine pods.

Both aircraft are equipped with an extensive array of sophisticated intelligence gathering equipment enabling military specialists to monitor the electronic activity of adversaries. Also known as "RJ", the aircraft are sometimes called "hogs" due to the extended "hog nose" and "hog cheeks". "Rivet Joint" is an air refuelable theater asset with a nationally tasked priority. It collects, analyzes, reports, and exploits enemy BM/C4I. During most contingencies, it deploys to the theater of operations with the airborne elements of TACS (AWACS, ABCCC, Joint STARS, etc.) and is connected to the aircraft via datalinks and voice as required. The aircraft has secure UHF, VHF, HF, and SATCOM communications. Refined intelligence data can be transferred from "Rivet Joint" to AWACS through the Tactical Digital Information Link (TADIL/A) or into intelligence channels via satellite and the Tactical Information Broadcast Service (TIBS), which is a nearly real-time theater information broadcast.

RC-135s have been widely used in the 1990's — during Desert Storm, the occupation of Haiti, and more recently over Bosnia. Using automated and manual equipment, electronic and intelligence specialists can precisely locate, record and analyze much of what is being done in the electromagnetic spectrum. The fleet of 14 "Rivet Joint" aircraft increased to 15 in late-1999 with the addition of a converted C-135B.

RC-135S "Cobra Ball"

An altogether more specialized role is undertaken by three RC-135S aircraft which normally operate from Shemya Island, Alaska. In addition to "thimble" noses, electronic receivers mounted in cheek fairings and a teardrop-shaped fairing on the aft fuselage, these also have large circular windows in the fuselage for the photography of foreign ballistic-missile tests at long range. The intelligence equipment includes multiple infrared telescopes and is known as the Real Time Optical System (RTOS). These aircraft allow the U.S. to monitor every reentry vehicle flown from Russian test ranges, to determine the capabilities of each Russian missile, new or old.

Telemetry Intelligence (Telint) is the role of the "Cobra Ball". With the decrease in foreign ICBM tests following the end of the Cold War, the RC-135Ss may adopt a theatre role spotting battlefield missiles. This is in response to the difficulties caused by the Iraqi "Scud" missiles during the Gulf War.

The RC-135 fleet has consistently proved of great value, both as a strategic reconnaissance tool during peacetime and as a more tactical asset during times of tension.


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