| COMMON VARIANTS
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.
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.
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.
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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