Tag Archives: Boeing C-135 Stratolifter

30 December 1964

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A Boeing KC-135A Stratotanker refuels a Boeing B-52E Stratofortress. (U.S. Air Force)

30 December 1964: The United States Air Force accepted the last of 732 Boeing KC-135 Stratotankers: KC-135A serial number 64-14840. The new tanker was assigned to the 380th Air Refueling Squadron at Plattsburgh Air Force Base, New York, 12 January 1965.

As of 14 May 2018, 396 KC-135s were still in service with the United States Air Force: 153 active duty, 72 Air Force Reserve, and 171 Air National Guard. It is estimated that the fleet is 33% through their design lifetime limits.

Built as an aerial refueling tanker to support the U.S. Air Force fleet of B-52 Stratofortress strategic bombers, an initial order for 24 tankers was soon increased to 250. Eventually 732 KC-135As were built by Boeing, and an additional 81 of other versions.

With the company internal designation of Model 717, the KC-135 was developed from the Model 367-80 proof-of-concept prototype, the “Dash Eighty.” The Stratotanker is very similar in appearance to the Model 707 and 720 airliners but is structurally a different aircraft. It is also shorter than the 707 and has a smaller diameter fuselage.

Boeing KC-135R Stratotankers of the 40th Air Expeditionary Group, forward deployed to support B-52 operations. (SMSGT John Rohrer, U.S. Air Force)
Boeing KC-135R Stratotankers of the 40th Air Expeditionary Group, forward deployed to support B-52 operations. (SMSGT John Rohrer, U.S. Air Force)

The Stratotanker was originally operated by a flight crew of four: pilot, co-pilot, navigator and refueling boom operator. Upgrades over the decades have simplified operation and the crew has been reduced to two pilots and the boom operator.

The KC-135R is 136 feet, 3 inches (41.529 meters) long (156 feet/47.549 meters with fueling boom extended), with a wingspan of 130 feet, 10 inches (39.878 meters), and overall height of 41 feet, 8 inches (12.700 meters). Its maximum takeoff weight is 322,500 pounds (146,284 kilograms).

The Stratotanker can carry up to 200,000 pounds (90,718 kilograms) of fuel for inflight refueling. It can also be configured to carry 83,000 pounds (37,648 kilograms) of cargo, or 80 passengers.

Boeing KC-135R Stratotanker 64-14840 at Rickenbacker Air National Guard Base, Columbus, Ohio, 2018. (Ohio Air National Guard)

The KC-135A was originally powered by four Pratt & Whitney J57-P-59W turbojet engines producing 13,750 pounds of thrust (61.163 kilonewtons) for takeoff, using water injection. The fleet has been re-engined with more efficient CFM International CFM56-2B1 (F108-CF-100) engines. Modified airplanes are designated KC-135R. The CFM56-2 is a two-spool, axial-flow, high-bypass turbofan with a single fan stage, 12-stage compressor section (3 low pressure and 9 high pressure stages), annular combustor, and a 5-stage turbine (1 high pressure and 4 low pressure stages). The engine is rated at 21,634 pounds of thrust (96.233 kilonewtons).

The tanker has a maximum speed of 350 knots (402 miles per hour/648 kilometers per hour) below 26,500 feet (8,077 meters), and 0.90 Mach when above that altitude. It has a range of 1,500 miles (2,424 kilometers) when carrying 150,000 pounds (68,039 kilograms) of transfer fuel. The service ceiling is 50,000 feet (15,200 meters).

The newest Stratotanker in service with the United States Air Force, KC-135R 64-14840 is 59 years old. It is presently assigned to the 121st Air Refueling Wing, Ohio Air National Guard.

The final Boeing Stratotanker, KC-135R 64-14840, remains in service with the 121st Air Refueling Wing, Ohio Air National Guard, based at Rickenbacker Air National Guard Base, Columbus Ohio. (Ohio Air National Guard)

© 2018, Bryan R. Swopes

14 May 1954

Aviation, , , , , , , , , , ,
Boeing 367-80 N70700 is rolled out of teh final assembly building at Boeing's facility at Renton Field, 14 may 1954. (Boeing)
Boeing 367-80 N70700 is rolled out of the final assembly building at Boeing’s facility at Renton Field, 14 May 1954. (Boeing)

14 May 1954: The Boeing Model 367-80 prototype, N70700, was rolled out at the Boeing plant at Renton Field, south of Seattle, Washington. Boeing’s founder, William Edward Boeing (1881–1956) was present. The prototype made its first flight 15 July 1954 with Boeing test pilots Alvin M. “Tex” Johnston and Richard L. “Dix” Loesch. It is painted yellow and brown.

Originally planned as a turbojet-powered development of the Boeing KC-97 Stratotanker, the Model 367, the 367-80 was the 80th major design revision. It is called the “Dash 80.”

Boeing had risked $16,000,000 in a private venture to build the Dash 80 in order to demonstrate its capabilities to potential civilian and military customers, while rivals Douglas and Lockheed were marketing their own un-built jet airliners. Put into production as the U.S. Air Force KC-135A Stratotanker air refueling tanker and C-135 Stratolifter transport, a civil variant was also produced as the Boeing 707 Stratoliner, the first successful jet airliner. Though they look very similar, the 707 is structurally different than the KC-135 and has a wider fuselage.

Cutaway scale model of the Boeing 367-80 showing interior arrangement. The woman on the right is Gloria Durnell, a secretary at Boeing. (Boeing)

The prototype Boeing Model 367-80 was operated by a pilot, co-pilot and flight engineer. The airplane’s wing was mounted low on the fuselage and the engine nacelles were mounted on pylons under the wing, as they were on Boeing’s B-47 Stratojet and B-52 Stratofortress. The wings and tail surfaces were swept to 35° at 25% chord, and had 7° dihedral. The Dash 80 was 127 feet 10 inches (38.964 meters) long with a wingspan of 129 feet, 8 inches (39.522 meters) and overall height of 38 feet (11.582 meters). The tail span is 39 feet, 8 inches (12.090 meters). The empty weight of the 367-80 was 75,630 pounds (34,505 kilograms) and the gross weight, 190,000 pounds (86,183 kilograms).

Boeing 367-80 N70700. (San Diego Air & Space Museum Archives)

N70700 was powered by four Pratt & Whitney Turbo Wasp JT3C engines. This engine is a civil variant of the military J57 series. It is a two-spool, axial-flow turbojet engine with a 16-stage compressor and 2-stage turbine. The JT3C-6 (used in the first production 707s) was rated at 11,200 pounds of thrust (49.82 kilonewtons), and 13,500 pounds (60.05 kilonewtons) with water/methanol injection). The JT3C is 11 feet, 6.6 inches (3.520 meters) long, 3 feet, 2.9 inches (0.988 meters) in diameter, and weighs 4,235 pounds (1,921 kilograms).

These gave the 367-80 a cruise speed of 550 miles per hour (885 kilometers per hour) and a maximum speed of 0.84 Mach (582 miles per hour, 937 kilometers per hour) at 25,000 feet (7,620 meters). The service ceiling was 43,000 feet (13,106 meters). Its range was 3,530 miles (5,681 kilometers).

Boeing continued to use the 367–80 for testing, finally retiring it 22 January 1970. At that time, its logbook showed 2,346 hours, 46 minutes of flight time (TTAF). It was flown to Davis-Monthan Air Force Base, Tucson, Arizona, and placed in storage. In 1990, Boeing returned it to flyable condition and flew it back it to Renton where a total restoration was completed. Many of those who had worked on the Dash 80, including Tex Johnston, were aboard.

Boeing 367-80, N70700, in storage. (San Diego Air & Space Museum)

The pioneering airplane was presented to the Smithsonian Institution and is on display at the National Air and Space Museum, Steven V. Udvar-Hazy Center. The Boeing 367-80 was designated an International Historic Mechanical Engineering Landmark by the American Society of Mechanical Engineers.

820 of the C-135 series and 1,010 Model 707 aircraft were built from 1957–1979.

(The Boeing Model 367-80 is on display at the Steven F. Udvar-Hazy center, Smithsonian Institution National Air and Space Museum. (Photo by Dane Penland, National Air and Space Museum, Smithsonian Institution)
The Boeing Model 367-80 is on display at the Steven F. Udvar-Hazy center, Smithsonian Institution National Air and Space Museum. (Photo by Dane Penland, National Air and Space Museum, Smithsonian Institution)

Highly recommended: Tex Johnston, Jet-Age Test Pilot, by A.M. “Tex” Johnston with Charles Barton, Smithsonian Books, Washington, D.C., 1991

© 2019, Bryan R. Swopes