Cold War Tankers

You can trace Cold War refueling through three tankers that handed the mission from one to the next. The KB-29 proved the flying boom, the KC-97 carried that boom around the world on a piston airframe, and the KC-135 took over as the jet tanker.

From Bombers to Tankers

If you look at the shapes, you see the family line. The KC-97 Stratofreighter was a four engined, piston powered strategic tanker based on the Boeing C-97 Stratofreighter, which was itself based on the B-29 Superfortress. It replaced the KB-29 and it was succeeded by the Boeing KC-135 Stratotanker. Boeing manufactured the KC-97 from 1951 to 1956, with introduction on 14 July 1951 and retirement in June 1978. The number built reached 811, with the United States Air Force as primary user and the Spanish Air Force as another user. The United States Air Force began operating the type in 1950. It received 811 KC-97 aircraft from Boeing and 74 of the C-97 cargo version, while ordering 816 KC-97 aircraft and 74 C-97 aircraft, the total of 890 given by the National Museum of the United States Air Force.

The step before that was also a bomber conversion. The KB-29 was a modified B-29 Superfortress for refueling needs of the United States Air Force, built as 282 total conversions. That total covered 92 KB-29M, 74 KB-29MR and 116 KB-29P aircraft, with introduction in 1948. Two squadrons show how new the job was. The 509th and 43d Air Refueling Squadrons at Walker Air Force Base in New Mexico and Davis-Monthan Air Force Base in Arizona were created in 1948 to operate the KB-29M tanker. From 1951 to 1953 the 303d Bombardment Wing at Davis-Monthan flew B-29 aircraft and KB-29 aircraft to train for bombardment and refueling to meet global commitments, including a deployment at Sidi Slimane in French Morocco from 5 October to 6 November 1952.

How Did the Looped Hose Actually Work?

Picture yourself behind a KB-29M before any boom existed. The first method was the looped hose, and it needed hands in the back. The tanker entered formation behind, above and to the left of the receiver, then unreeled a hauling cable fitted with a 55 pound weight so it hung near vertical. The receiver trailed its own cable ending in a drag cone and a grapnel so it streamed near horizontal. With both cables out, the tanker crossed to the right of the receiver so the cables snagged. The tanker then hauled both cables inside, joined the receiver cable to its hose, and passed the hose to the receiver for pumping from internal fuel compartments. When the receiver was full, you reversed the sequence so each airplane recovered its own gear. Clumsy is the right word, and the method stayed in use in the late 1940s until a better answer arrived. It was used to refuel Lucky Lady II during the 1949 flight around the world, a flight that helped the argument that the Air Force rather than the Navy should provide nuclear delivery, with expansion of Strategic Air Command and cancellation of Navy super carriers as the result. The loop worked only with large multi crew airplanes because crew members had to handle the haul.

Why Did the Flying Boom Win for SAC?

You get easier single seat refueling once the hose carries its own funnel. Several KB-29M aircraft were fitted with probe and drogue systems, where the hose ends in a torus shaped para drogue and the receiver uses a probe on the nose or wing that the pilot steers into the basket. To learn more about that contact, see probe and drogue coupling and how the pilot flies the connection. One KB-29M, redesignated YKB-29T, even carried two more hoses on the wingtips and served as the prototype for the KB-50D. The refueling systems were developed and installed by Flight Refuelling Ltd at Tarrant Rushton in the United Kingdom. Boeing then developed a rigid flying boom and first used it on the KB-29P. The boom sat at the aft end and used V tail like control surfaces for stabilization at the far end, so the operator could maneuver it in flight. That V tail style stayed on most Air Force tankers into the 21st century. Strategic Air Command selected the flying boom as its preferred method for bombers, and because that command grew so large the boom became the most common method in the Air Force. It was used on KC-97 aircraft and on later tankers such as the KC-135 Stratotanker, the KC-10 Extender and the KC-46 Pegasus. If you want to picture the operator job, read how the flying boom moves under operator control. The KB-29P was operated in the mid 1950s by the 420th Air Refueling Squadron at Royal Air Force Sculthorpe in Norfolk, while from 1954 to 1957 the 407th Air Refueling Squadron was based at Great Falls Air Force Base, later renamed Malmstrom Air Force Base.

What Made the KC-97 a Double Fuel Airplane?

Step inside the KC-97 and you find two fuel worlds that never meet. The tanker carried aviation gasoline for its own piston engines and jet fuel for its refueling mission, each with an independent system. In an emergency it could offload its aviation gasoline to a receiver in a procedure known as a save. The airframe was greatly modified from the C-97 with tanks, plumbing and a flying boom first developed for the KB-29. The upper deck was cavernous and could take oversize cargo through a very large right side door. Transferable jet fuel sat in tanks on the lower deck on G through L models. Both decks were heated and pressurized for high altitude work. The boom operator lay prone and viewed the operation through a window at the bottom of the tail, a layout later used on the KC-135. For airframe numbers and unit history, the detailed KC-97 history lists production blocks and assignments. Early test work used three C-97A aircraft converted as KC-97A tankers with the rear door removed and a boom added, then converted back to standard C-97A aircraft once the design was proven. Production then settled into KC-97E aircraft with rear doors permanently closed, 60 built, some later used as C-97E transports, and KC-97F aircraft with 3800 hp R-4360-59B engines and minor changes, 159 built, some later used as C-97F transports.

Why Did Jets Struggle Behind a Piston Tanker?

You feel the speed gap as soon as a jet closes on a KC-97. The tanker was effective, but its slow speed and low operating altitude complicated work with jet receivers. B-52 aircraft typically lowered flaps and rear landing gear to fly slow enough to take fuel from the KC-97. A typical B-52 engagement used a descent that let the pair hold a higher airspeed of 220 to 240 knots. The mission still mattered worldwide. These tankers were vital to Boeing B-47 Stratojet operations around the world, including support for Arctic reconnaissance flights from Thule Air Base. During Operation Creek Party, which started in 1967 and lasted for 10 years, Air National Guard and Air Force Reserve tankers supported active duty Air Force and NATO units in Europe, including a KC-97L from the 160th Air Refueling Group of the Ohio Air National Guard. The dual role KC-97G, company designation Model 367-76-66, became the main build with 592 aircraft and underwing fuel tanks, while 135 KC-97G aircraft were later converted to C-97G transports and 27 became C-97K troop transports. For search and rescue, 22 became HC-97G aircraft. Five became GKC-97G ground instruction airframes. One KC-97F became the KC-97H to test hose and drogue refueling.

How Did the KC-97L Try to Keep Up?

You add jets to a piston tanker when fighters cannot wait. In the early 1960s Tactical Air Command added two General Electric J47 twin jet pods taken from retired KB-50 tankers to produce the KC-97L. The pods gave more speed for short periods and made the tanker more compatible with fighters like the F-84, the F-100 and the F-101. The path ran through test work. One aircraft was modified to test underwing General Electric J47-GE-23 jet engines as the JKC-97G, later designated KC-97L. In the end 81 KC-97G aircraft were modified with two J47 turbojet engines on underwing pylons as KC-97L aircraft. Two other jet ideas did not survive. Two KC-97G aircraft were converted with four Pratt and Whitney YT34-P-5 turboprops of 4250 kW as the YC-97J, company designation Model 367-86-542, and the work was dropped in favor of the KC-135. The Wikipedia page does not publish KC-135 dimensions or performance figures.

Where Did the Cold War Tankers Go Next?

You can follow the handover in unit moves. In 1956 Strategic Air Command began phasing out its KC-97 aircraft in favor of the KC-135 Stratotanker. KC-97 aircraft kept flying with Tactical Air Command, the Air Force Reserve and the Air National Guard. The last aircraft retired in 1978, when the Texas Air National Guard and the Utah Air National Guard exchanged KC-97L aircraft for the C-130 Hercules and the KC-135 Stratotanker respectively. Spain operated 3 former Air Force aircraft from 1972 to 1976. Special missions show another side of the airframe. Three KC-97G aircraft became EC-97G conversions for ELINT work, with aircraft 53-106 operated by the Central Intelligence Agency for covert ELINT operations in the West Berlin Air Corridor. The codenames Eager Beaver and Rivet Box were used for Big Safari built photoreconnaissance modifications to the C-97G for the 7405th Support Squadron along the Berlin air corridors. One KC-97 airframe, Air Force serial 52-0828, was adapted into the Aero Spacelines Super Guppy to carry Apollo Program rocket stages from California to Florida. It carried the Saturn S-IVB stage, which served as the second stage of the Saturn IB, the third stage of the Saturn V and the fourth stage for the never built Nova rocket. That modified KC-97 was constructed in 1953 and purchased by NASA in 1997, and it remains in service supporting NASA, other Federal agencies and Federal contractors. It is one of two KC-97 aircraft left in flyable condition, the other being former KC-97G 52-2718, Angel of Deliverance, flown by the Berlin Airlift Historical Foundation as YC-97A 45-59595. To place the boom, the drogue and the jet tanker in your own study, open a tanker guide page and match each variant letter to its fuel system and pod fit before your next museum visit.