Text: Serge Van Heertum - Pictures: Joe Fischer - Christian De Brabanter & others as mentionned - Translation: David Niemegeerts © sbap 2015

An amazing airplane was visiting Melsbroek airbase in February under the “Open Skies” treaty. This 54-year old US aircraft was a Boeing OC-135B AF61-2970 (c/n 717-158).
The OC-135B Open Skies United States Air Force observation aircraft supports the Treaty on Open Skies. The aircraft, a modified WC-135B, flies unarmed observation flights over participating countries of the treaty. Three OC-135B aircraft were modified by the Aeronautical Systems Center's 4950th Test Wing at Wright-Patterson Air Force Base in Ohio. The first operationally capable OC-135B was assigned to the 24th Reconnaissance Squadron at Offutt AFB in October 1993. It is now fitted with a basic kit of navigational and sensory equipment, and placed in high-security storage at the Aerospace Maintenance and Regeneration Center at Davis-Monthan Air Force Base near Tucson, Arizona. Two fully operational OC-135B aircraft were delivered in 1996 with the full complement of treaty-allowed sensors, which includes an infrared line scanner, a synthetic aperture radar and video scanning sensors.

The AF61-2670 as WC-135B (Coll SBAP)
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 Threat Reduction Agency (DTRA). Cameras installed include one vertical and two oblique KS-87E framing cameras used for low-altitude photography approximately 3,000 feet (900 m) 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 (11,000 m).
The OC-135B modifications center around the 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. Other modifications to the aircraft also included installing an auxiliary power unit, crew luggage compartment, sensor operator console, flight following console and upgraded avionics. 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 on board.
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 55th Wing, 45th Reconnaissance Squadron, Offutt Air Force Base (Nebraska).
Open Skies

The Treaty on Open Skies came into play on January 1, 2002, and currently has 34 States involved. It establishes a program of unarmed aerial surveillance flights over the entire territory of its participants. The treaty is designed to enhance mutual understanding and confidence by giving all participants, regardless of size, a direct role in gathering information about military forces and activities of concern to them. Open Skies is one of the most wide-ranging international efforts to date promoting openness and transparency of military forces and activities. The concept of "mutual aerial observation" was initially proposed to Soviet Premier Nikolai Bulganin at the Geneva Conference of 1955 by President Dwight D. Eisenhower; however, the Soviets promptly rejected the concept and it lay dormant for several years. The treaty was eventually signed as an initiative of US president (and former Director of Central Intelligence) George H. W. Bush in 1989. Negotiated by the then-members of NATO and the Warsaw Pact, the agreement was signed in Helsinki, Finland, on March 24, 1992.
Looking at Brussels Military Airport (Joe Fischer)
(Joe Fischer) (Joe Fischer)
Early the morning with some fog around...(Joe Fischer)
A 54 years old flying machine (Christian De Brabanter) Close up on the nose section (Christian De Brabanter)
Some informations...(Christian De Brabanter) Nice high visibility US roundel (Christian De Brabanter)
Specific structural reinforcements (Christian De Brabanter)
Pratt & Withney TF-33-P-5 powerplant (Joe Fischer) Clear informations on the engine cover (Christian De Brabanter)
If it's not Boeing, I'm not flying... (Christian De Brabanter) Clean nose wheel (Joe Fischer)
Waiting for next flight (Christian De Brabanter) The pilot office (USA Open Skies)
Control screens in the cargo section (USA Open Skies) Sample of picture made by the OC-135B (USA Open Skies)
View of the both side... (Joe Fischer) ...for our modelling readers (Christian De Brabanter)

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