Boeing NC-135

Boeing NC-135. The NC-135 designation refers to a small number of highly modified Boeing C-135 Stratolifter airframes operated by the United States Air Force for specialized test and research missions. These aircraft were extensively reconfigured to support advanced scientific programs, including astronomical observation, atmospheric research, and the calibration of critical Department of Defense sensor systems. Their unique modifications made them invaluable assets for Air Force Materiel Command and collaborating agencies like NASA.

Development and Variants

The NC-135 series originated from the conversion of existing C-135 airframes, primarily the KC-135 Stratotanker variant, under contracts managed by the Air Force Systems Command. The first conversion created the **NC-135A**, a unique aircraft modified for the **Airborne Visible Observatory** program, which involved installing a large astronomical telescope in its fuselage. Another significant variant was the **NC-135E**, known as **"Big Crow"**, which was heavily modified with numerous radomes and antennae to simulate Soviet Union radar signatures for electronic warfare training. A further aircraft, the **NC-135W**, was configured as an airborne calibration platform for Air Combat Command, tasked with verifying the performance of ground-based radar sites across the North American Aerospace Defense Command network. These conversions were carried out at facilities like Tinker Air Force Base and involved major contractors such as LTV Aerospace.

Operational History

Entering service in the late 1960s, these aircraft supported a wide array of research and development efforts throughout the Cold War and beyond. The NC-135A played a crucial role in several solar eclipse expeditions, allowing scientists to conduct prolonged coronal observations above weather interference. The NC-135E "Big Crow" was a frequent participant in major exercises like Red Flag at Nellis Air Force Base, where it trained F-15 Eagle and F-16 Fighting Falcon crews in electronic countermeasures. The NC-135W spent decades traveling to Alaska, Canada, and various Continental United States locations to calibrate the Distantly Piloted Aircraft tracking systems and early-warning radars. Their operations were often conducted under the auspices of the 4950th Test Wing and later the 452nd Flight Test Squadron.

Design and Systems

Structurally, the airframes retained the basic C-135 layout but featured drastic external and internal modifications. The NC-135A was distinguished by a large upward-opening door on its upper fuselage for the telescope, while the NC-135E was covered with protruding radomes, blade antennae, and specialized pallet-mounted electronic systems to emit complex signals. Internally, workstations replaced cargo areas, accommodating mission specialists from organizations like the Air Force Research Laboratory and MIT Lincoln Laboratory. Avionics were consistently upgraded, incorporating advanced inertial navigation system units and secure UHF communications compatible with NORAD networks. Power systems were heavily augmented to support the high electrical demands of the onboard laboratories and sensor suites.

Notable Missions and Deployments

One of the NC-135A's most notable deployments was to Kenya for the 1973 solar eclipse, a mission coordinated with Harvard College Observatory. The NC-135E was famously deployed to RAF Mildenhall in the United Kingdom to support NATO exercises, emulating Warsaw Pact threat systems for allied air forces. Another significant mission involved the NC-135W's repeated deployments to Clear Air Force Station in Alaska to calibrate the Ballistic Missile Early Warning System. This aircraft also played a role in testing for the Strategic Defense Initiative during the Reagan Administration, evaluating sensor performance against simulated missile launches.

Operators

The exclusive operator of all NC-135 aircraft was the United States Air Force. Primary units included the **4950th Test Wing** at Wright-Patterson Air Force Base, which managed the NC-135A, and the **452nd Flight Test Squadron** under **Air Force Materiel Command**, which operated the NC-135W. The NC-135E "Big Crow" was assigned to the **6512th Test Squadron** at Edwards Air Force Base. These aircraft were often tasked to support projects for the **Defense Nuclear Agency**, the **United States Strategic Command**, and in joint ventures with **NASA's Ames Research Center**. Category:United States military reconnaissance aircraft Category:Boeing aircraft Category:Four-engined jet aircraft