U.S. military aerial refueling: extending ‘the reach’

  • Published
  • By Mark Morgan
  • Air Mobility Command History Office
SCOTT AIR FORCE BASE, Ill. --  Editor's note: This is the third in a series of articles celebrating 80 years of aerial refueling and the important role aerial refueling has played in American military history. 

After the success of the Question Mark's Jan. 1929 aerial refueling flight, and the operational shortcomings of the spring 1929 Army war-game maneuver, the U.S. Army Air Corps spent little time thinking about aerial refueling. This was not to say that nothing was done with the air refueling concept through the 1930s, but most was accomplished thanks to civilian aviators. The Question Mark also rekindled Britain's interest in air refueling.

From 1930 until 1937, the Royal Air Establishment at Farnborough conducted a series of air refueling experiments. The Royal Air Force looked at air refueling not so much as a way to extend an aircraft's reach, but more to help lighten take-off weights to reduce wear and tear on the aircraft and grass airfields. They also looked at it as a way to supplement the narrow bomber size restrictions being considered by the League of Nations -- less fuel on take-off, meant more bombs could be loaded on the aircraft.

These experiments began with the Question Mark's techniques (improved by U.S. barnstorming efforts) of the dangle-and-grab method. To accomplish this, the tanker aircraft would feed out a hose that someone in the receiving aircraft reached out and grabbed.

In September 1934, Flight Lieutenant Richard Atcherly introduced his newly patented looped-hose aerial refueling system.

This new technique put most of the operational effort on the tanker crew. Both the tanker and receiver trailed cables with grapnels on the ends. The receiver flew a straight line, while the tanker crossed its path from behind allowing the grapnels to catch. The receiver then reeled in the cables, along with a hose from the tanker. Once the two aircraft were connected with about 300 feet of hose, the tanker pilot would then maneuver to a higher position and let gravity take care of rest.

These experiments continued until 1937, but by then, even the Royal Air Force had decided that air refueling offered a limited application at best. Aircraft technology had surpassed any perceived need for air refueling. Before this date, the standard aircraft were bi-planes (although monoplanes had started becoming more frequent) using "doped" linen fabric and fixed landing gear, with only a little consideration given to aerodynamics.

By 1933, two American corporations built the first all-metal, low-wing monoplanes -- the Douglas DC-1 and the Martin B-10 bomber. These aircraft, each about 17,000 pounds, had retractable landing gear, cowled engines, and high-lift devices to improve take-offs. They also used the new controllable pitch propeller. These advances didn't do much for payloads, but they doubled the DC-1's and B-10's airspeed and operating range over their contemporary aircraft.

British commercial interests, however, soon returned to the idea of air refueling. Companies began looking at "flying boats" to connect the widespread British Empire, and they hoped air refueling would improve their operation.

Sir Alan Cobham and Flight Refueling Limited, or FRL, further refined the looped-hose system. In 1939, from Aug. 5 to Sept. 30, Imperial Airways took advantage of the first commercial air refueling operations. The company flew Short S.30 flying boats for weekly mail service flights between Southampton, England, and New York City. FRL used two obsolete Handley Page HP.54 Harrow bombers as tankers -- one at Gander, Newfoundland, and the other at Rineana, Ireland. These air refueling operations were not intended to extend the flight times, but to allow the flying boats to take off with minimal fuel and more mail. Imperial Airways flew 15 of these transatlantic missions before the outbreak of World War II.

World War II offered many examples of how air refueling could be used. For example, Britain depended on shipping to stay alive, and aircraft technology provided only limited support. Bomber operational ranges early in the war meant they were not very useful in helping to suppress the German submarine threat. Still, in wartime, many innovations are examined and tested. During World War II, air refueling was among them.

Just after Pearl Harbor, the U.S. Army Air Forces began working on an air refueling solution. With the help of Hugh Johnson, the man who had been in charge of FRL's Gander operations, they studied three primary concepts. First, planners looked at launching B-17 Flying Fortresses from Midway Island against Japan, with the idea of using modified B-24 Liberators as tankers. Second, they considered using B-24s from Hawaii with tanker support from U.S. Navy seaplanes. The third concept called for B-17s to tow fuel-laden gliders to serve as tankers.

Testing -- using a variation of the looped-hose method -- began in the summer of 1943 at Eglin Field, Fla. A B-17E served as the receiver and a modified B-24D as the tanker. The successful tests extended the B-17's range (with three tons of bombs) from 1,000 to 1,500 miles.

The problem now was how would the country's taxed manufacturers build the equipment for squadrons of B-24 tankers and B-17 receivers? Added to this dilemma was the time required for the aircraft modifications and crew training. Additionally, by mid-1943, Boeing began rolling out the B-29 Superfortress. The B-29 had a combat radius of 1,500 miles and carried twice the bomb load of the B-17.

In 1944, the U.S. Army Air Forces began studying the feasibility of equipping B-29s with an air refueling capability. The engineers at Wright Field, Ohio, determined it was possible to modify the aircraft, but the 1,500-gallon capacity of a B-24 tanker only extended the B-29's range by 830 miles. At the same time, the British developed plans to convert 600 Lancaster bombers to serve as tankers in the Pacific, serving 600 Lincoln bombers. However, before any air refueling plans to support the bombing mission reached fruition, Allied forces began seizing islands within striking distance of Japan.

The U.S. Army Air Forces also looked at a possible refueling method for smaller fighter aircraft. A contractor, All American Aviation, equipped and tested a specially modified P-38 Lightning and a B-24 tanker. In the test, the B-24 suspended an external fuel tank on a cable. The P-38 was to catch that cable, securing it into a device mounted on the forward fuselage. The fighter would then descend to the tank which was to lodge into the securing device while the cable broke away. A nitrogen bottle fired to force the fuel into the fighter before ejector springs released the tank. The tests proved highly unsuccessful, and in March 1945, the Army Air Forces cancelled the method as unsound.

While air refueling was not used operationally, World War II led the U.S. Army Air Forces to examine its potential. These studies and the testing of new equipment showed what air refueling could offer to future contingency operations.

By 1947, when the Department of the Air Force became a separate service, these wartime studies and the continued post-war testing ensured air refueling would soon serve as a critical component of modern air power.