Flying Forever - Pre-WW2 In-Flight Refuelling

The limited range of early aircraft may have prompted thoughts about ways to augment their limited fuel supplies before World War 1; certainly, the problem began to receive serious, if isolated, attention during the War by a number of aviatiors.

Imperial Russian Navy Alexander Seversky proposed a refuelling scheme in 1917 to increase the range of pursuit aircraft. If any experiments were conducted, they may be lost to history. Seversky moved to the United States in 1918, and three years later applied for a patent on an air-to-air refuelling system.

In 1918, mostly at his own expense, U.S. Navy Reserve officer Godfrey Cabot tested, with Naval assistance, a scheme to enable long-distance delivery of multi-engined aircraft across the Atlantic. He used an elastic rope and V-shaped guide to pick up fuel containers. By then the war was over and interest waned. The common answer to any need to increase an aircraft's range was to strip away non-essential weight and replace it with fuel.

The first serious attempt to refuel an aircraft in flight (barnstorming demonstrations aside) came in 1923, when U.S. Army Air Services pilots at Rockwell Field conducted experiments with the aim of establishing an endurance record. Two modified DH-4C aircraft were used. The tanker lowered a hose on a cable, which was caught by an observer in the receiving aircraft and inserted into the tank. A quick-acting valve opened and the tank filled by gravity and air pressure.

After beginning in April 1923, a number of attempts were thwarted by weather and problems with the aircraft. On 27/28 August, Lts. L.H. Smith & J.P. Richter used the system to establish an endurance record of 37 hrs. 15 min. Other successful flights, including one from the Canadian to the Mexican border, followed. The project ended when the pilots were posted to other duties.

Across the Atlantic, the French Aviation Militare were encouraged by the American experiments. In 1923 they, too, were able to demonstrate aerial refuelling a number of times without incident. In the same year, Britain's Royal Aircraft Establishment (R.A.E.) was directed to undertake similar experiments.

In 1924 successful tests were conducted, transferring water rather than fuel, between a pair of Bristol Fighters, but nothing further eventuated until the 1930s. In the interim, attempts to set new aerial long distance records involving air refuelling proceeded in the U.S.A., and in the British Commonwealth to assist civilian aviators. Germany, Japan and Russia also conducted trials.

The R.A.E. was asked to conduct trials in 1930 to examine the possibility of refuelling large aircraft in flight. Trials began the same year, firstly using a DH-9A trailing a weighted cable for a Vickers Virginia, and later using two Virginias. The method was simple, if risky; an observer in the tail of the receiving aircraft attempted to catch the tanker hose with a hooked stick and connect it to the aircraft's tank.

A number of successful transfers were achieved, and the technique was demonstrated to the public at the 1931 Hendon R.A.F. display, using a Virginia tanker and a Wapiti. By 1934, the system had become more sophisticated, with a hose being lowered from the tanker's fuselage to the rear cockpit of the second aircraft.

Refuelling tests for transatlantic civilian flying boats proceeded in the late 1930s, and a comparison between these methods and those of the R.A.E. at Farnborough in August 1937. The trials were inconclusive, both methods seen as being in need of further development, but the civil project was awarded an Air Ministry contract and R.A.E. work ceased.

The Air Ministry became more interested in aerial refuelling for bombers and other operational aircraft as the 1930s progressed. A 1939 study using a Stirling bomber showed promise, but no trials were carried out. Both Britain and the U.S.A. revived their interest in in-flight military refuelling during WW2.