Aircraft Factfile and Recognition Guide - OC-135B "Open Skies"

 

Background

The OC-135B Open Skies United States Air Force observation aircraft supports the Open Skies Treaty. The aircraft, a modified WC-135B, flies unarmed observation flights over participating parties of the treaty. The OC-135B modifications center around four cameras installed in the rear of the aircraft. Since its primary mission is to take pictures, most of the installed equipment and systems provide direct support to the cameras and the camera operator. Work on the aircraft also included installing an auxiliary power unit, crew luggage compartment, sensor operator console, flight following console and upgraded avionics.

The interior seats 35 people, including the cockpit crew, aircraft maintenance crew, foreign country representatives and crew members from the U.S. Department of Defense's Defense Threat Reduction Agency.  Cameras installed include one vertical and two oblique KS-87E framing cameras used for low-altitude photography (approximately 3,000 feet above the ground), and one KA-91C panoramic camera, which scans from side to side to provide a wide sweep for each picture (used for high altitude photography at approximately 35,000 feet).

The data annotation and recording system (DARMS) processes navigational, altitude, time and camera signals to annotate each picture with correct position, altitude, time, roll angle and other information. In addition, this system records every picture taken according to camera, frame and navigational position and downloads this data to a 3.5-inch floppy disk. A keyboard with trackball is the input device for operation of this system. Two Barco 12-inch VGA color monitors display camera annotation and other camera data on screen for the sensor operator and observer use.

Camera control, located in the sensor operator's console, operates and adjusts individual cameras for cloud cover, frame overlap and other functions. The sensor operator console seats four and has all the equipment listed above plus camera bay heating control, chronometers, emergency oxygen, interphone and individual lighting. The flight following console also seats four and includes most of the equipment listed above except for DARMS and camera controls.  Seven commercial Norcoid Tek II coolers with individual refrigeration units maintain temperature and humidity control to maintain peak film performance. The units can be removed, if necessary, from the aircraft in order to transport film. The coolers are capable of storing 40,000 feet of film.

The aircraft flies on its intended flight path throughout the entire mission with no reliance on ground-based navigation devices. A top-of-the-line commercial system, Litton 92 INS/GPS, which is an integrated inertial navigation system (INS) with a global positioning system (GPS), provides continuous updates. The GPS updates the INS several times per second to correct any deviations in the flight path. The INS also feeds precise latitude, longitude, time, roll angle and barometric altitude to the DARMS and camera systems. A true airspeed computer feeds true airspeed data to the INS.

A combined altitude radar altimeter provides precise height above ground information to the pilot for navigational purposes as well as a signal to DARMS for film annotation. It is accurate from 0 to 50,000 feet above the ground level. Plus, a metric altimeter is installed on the pilot's instrument panel for altitude reference when flying in countries that use meters for altitude reference.

The aircraft are being upgraded with the Block 30 Pacer Crag Navigational System upgrade, a first step in making them compliant with ICAO mandated Global Air Traffic Management and Global Air Navigation Standards guidelines.  Other modifications support the aircrew. A gaseous oxygen system replaced the liquid oxygen system to be more compatible with foreign airfields, and fluorescent lighting system was added throughout the cabin to provide adequate lighting for operation and inspections. Four upgraded seats with a conference table, interphone, lighting and oxygen comprise the mission commanders' station for both countries mission commanders. A four channel interphone system enables segregated communications between various elements onboard.

The auxiliary power unit enables the aircraft to start engines and provides electrical power and cabin heat independent of ground support equipment. It was manufactured by Allied Signal with the installation and design of the installation by E-Systems and World Auxiliary Power Company.

The aircraft are assigned to Air Combat Command at the 55 Wing, 45th Reconnaissance Squadron, Offutt Air Force Base, Neb., for operations, training and maintenance. When tasked, ACC's role is to transport a DTRA observation team to an Open Skies point of entry airport, and conduct the observation flight, then return the team to the continental United States.

Three OC-135B were modified by the Aeronautical Systems Center's 4950th Test Wing at Wright-Patterson AFB, Ohio. The first initial operational capability OC-135B was assigned to the 24th Reconnaissance Squadron, at Offutt AFB, Neb. in October 1993. It is now fitted with a basic set of navigational and sensor equipment, and placed in inviolate storage at Aircraft Maintenance and Regeneration Center at Davis Monthan AFB, Ariz. Two fully operational OC-135B aircraft were delivered in 1996 with the full complement of treaty allowed sensors, which includes an infrared line scanner, synthetic aperture radar and video scanning sensors.

Recognizing the KC-135 Series

The KC-135 series of aircraft are rather easy to identify. However, they can very easily be confused with any other aircraft that shares a similar silhouette. If you THINK you see a KC-135, but aren't sure if it really is one, keep in mind the following:

Wings: Low-mounted, swept-back, and tapered with a positive slant.
Engines: Four turbofans mounted on pylons under the wings. Engines extend well forward of the wings' leading edges.
Fuselage: Round, cigar-shaped, tapers to the rear. Rounded nose, stepped-up cockpit.
Tail: Swept-back, tapered fin with a square tip. Horizontal stabilizers are swept-back, tapered, and mid-mounted on the fuselage.
Boom: Aft of the fuselage is a little set of "ruddervators" that belong to the refueling boom. Found on all KC-135s and most EC-135s.

If there is NO BOOM on the aircraft and it shares the same characteristics, you're looking at the following:

NKC-135A: Air Force testbed for laser lab projects. The NKC-135A at the USAF Museum in Dayton, OH has a giant laser turret on the top of its forward fuselage.

(O)C-135: Basic KC-135 airframe WITHOUT the boom. Some C-135s may have some unusual bumps from the top and the bottom of the fuselage while the OC-135s are easily identified by the "Open Skies" stripe on the tail.

KC-135 "Vomit Comet": Operated by NASA, the aircraft is recognized by its NASA markings. It is used to train astronauts in weightless environments (like in space) by flying parabolas.

WC-135: Easily identified with the "Weather" stripe on the tail.

If the aircraft has an extended-length nose, it could be either of the following:

EC-135N/E ARIA/ALOTS: Monstrous "Snoopy" nose housing a seven-foot diameter parabolic radar. The ALOTS pod is located on the left-side of the fuselage and it is an external fairing. E-model ARIAs are identifiable with their TF-33 turbofans (similar to those on the KC-135E) while N-model ARIAs are powered by J57 turbojets (same powerplant as the KC-135A/Q).

RC-135S Cobra Ball: 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.

RC-135U Combat Sent: Cheek fairings and additional fairings in the chin, boomer, wingtip, tailcone and fin-top positions.

RC-135V/W Rivet Joint: 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.

If the aircraft does NOT have a boom or an extended-length nose, it is NOT a C-135 series aircraft. Examples below include:

E-3 Sentry: Slightly larger, but most notable feature is a giant rotating radome on the rear fuselage.

E-6B Mercury: Flown by the US Navy and is powered by CFM turbofan engines (similar to the KC-135R)

E-8 Joint STARS: Giant section of electronics hanging off the bottom right side of the forward fuselage.

The E-3, E-6, and E-8 are all based off the Boeing 707-320 airliner while the C-135 series is based off the 367-80 Prototype.

The Dash 80 is smaller than the Boeing 707s that were in commercial service.

Specifications

Primary Function: Support Open Skies Treaty
Contractor: Boeing Military Airplanes Div.
Power Plant: Four Pratt & Whitney TF33-P-5 Turbofans with thrust reversers
Thrust: 16,050 pounds each engine
Wingspan: 131 feet (39.9 meters) 
Length: 135 feet (41.1 meters)
Height: 42 feet (12.8 meters)
Weight: 126,400 (57,334 kilograms)
Maximum Takeoff Weight: 297,000 pounds (133,633 kilograms) 
Fuel Capacity: 130,000 pounds (58,967 kilograms)
Speed: 500+ miles per hour (Mach.66)
Range: 3,900 miles (6,500 kilometers)
Crew:  (flight crew), seven (augmented crew) - three pilots, two navigators, and two sensor maintenance technicians; (DTRA mission flight crew), one mission commander, one deputy mission commander, two sensor operators and one flight follower
Unit Cost: unavailable
Initial operating capability:  October 1993

Sources: USAF OC-135B factfile, Fact Index - OC-135 Open Skies

© 2010 Steven Holzinger