The sky’s great gas station

BY MIKE LOMBARDI

Whether carrying relief to tsunami victims in Southeast Asia or conducting operations in the war against terrorism, the U.S. Air Force is justifiably proud of its ability to respond quickly to any situation anywhere around the globe. This global reach capability has been made possible by a fleet of Boeing- and McDonnell Douglas-built tanker aircraft that have the unique ability to refuel aircraft quickly while in flight, using innovative technology pioneered by Boeing.

In the 1920s most planes had limited range. That prompted numerous experiments in aerial refueling. The first serious attempt was made in 1923 by a pair of U.S. Army DH-4Bs and was nothing more than dangling a hose from one plane to the other, as the receiving aircraft’s crew grabbed the hose and placed it into the fuel tank. It was not long before Boeing began to help with these refueling experiments and offered up a modified Boeing model 95, called the “Hornet Shuttle,” to be used in proving the viability of in-flight refueling.

In the early 1930s, longer-range commercial planes such as the Boeing 247 and the Douglas DC-2 and DC-3 eliminated the necessity for in-flight refueling. Some notable developments continued in Great Britain during the 1930s—in particular, the work of Richard L.R. Atcherly and Sir Alan Clobham—that led to the development of a system of looped hoses and fittings for routine aerial refueling.

During World War II, long-range planes with large internal fuel capacities, such as the Boeing B-29 Superfortress, eliminated any need for aerial refueling. But with the advent of the Cold War, it became apparent that U.S. bombers would need the capability to fly to targets deep inside the Soviet Union from bases in the United States—something that even the B-29 could not do.

To remedy the situation, the Boeing Wichita (Kan.) Division converted 92 existing B-29s into KB-29M tanker aircraft that used the looped hose system developed by Clobham’s company, Flight Refueling Ltd. In 1949, the KB-29 tankers made possible the world’s first nonstop around-the-world flight when the B-50A, made the flight in 94 hours, refueled in flight four times by KB-29Ms.

The Air Force now had the global reach it needed to assure deterrence during the early days of the Cold War, although the system of looped hoses proved to be inefficient and exposed crew members to the elements. To remedy the situation, Gen. Curtis LeMay, commander of the Strategic Air Command, asked Boeing to develop a more efficient system that could transfer fuel at a much higher rate and at higher altitudes.

Boeing engineers came up with the innovative concept of the “Flying Boom,” a rigid, telescoping tube that extended out the back of the tanker aircraft. The flyable boom had small wings, or “ruddevators,” that allowed an operator in the tail of the tanker to steer the refueling nozzle toward the aircraft requiring fuel.

The B-29 was also the first to employ the flying boom system, and between 1950 and 1951, 116 B-29s, designated KB-29Ps, were converted on the assembly line at Renton, Wash.

Boeing went on to develop the world’s first production aerial tanker, the KC-97 Stratofreighter. After proving the feasibility of jet bombers with the B-47 and B-52, Boeing went forward to develop, with its own money, a jet transport that could serve as both an aerial tanker and a commercial transport. That plane, the Dash 80 prototype, proved the feasibility of a jet tanker to the Air Force, leading to Boeing receiving contracts to build 732 KC-135 Jet Stratotanker. After nearly 50 years, the KC-135 continues to serve, along with McDonnell Douglas KC-10 Extenders, as the backbone of the Air Force’s refueling fleet. And last month, Boeing rolled out the world’s most advanced tanker, the KC-767A.

From the early testing of the concept of aerial refueling to inventing the technology of the flying boom and the world’s only production tanker aircraft, Boeing has been a pioneer and a lead innovator in in-flight refueling.

michael.j.lombardi@boeing.com