Posted on November 09, 2021

The Evolution of Aerial Refueling Solutions

John Joyce
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John Joyce

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Air refueling (AR) is the use of inflight refueling aircraft to keep strike and surveillance aircraft in the air for long periods to observe adversaries, refuel airlifters (delivery of supplies or personnel), and support sustained airstrike operations.

It started in April 1923, when the U.S. Army began tests at Rockwell Field in San Diego, California, to establish a practical way to lower a hose from one airplane to refuel another in flight. The concept involved having a DH-4B biplane outfitted as a tanker and equipped with a 50 foot (15 meter) length of hose and a quick-acting shutoff valve to fly above the receiver aircraft and lower the hose. The person in the rear seat of the receiver aircraft would grab the hose and connect it to the aircraft’s fuel tank. If the hose became detached, the valve would immediately shut off the flow, preventing it from spraying fuel over the receiving aircraft and its pilot. It took multiple attempts, yet by using this technique, in August of that year one of the DH-4Bs was able to maintain a flight lasting over 37 hours while refueling more than a dozen times.

Years of experimentation and hit and misses took place to advance technologies. Though inflight refueling techniques were used during World War II, it wasn’t until the Korean War that the U.S. flew jet fighters requiring bombers the capacity to make non-stop round trips from Korea to the Soviet Union. By then, advancements in technology had driven the progress of aerial refueling. Then late 1950 saw a turning point, when two devices had been developed to give the tanker’s feed line stability in the airstream: a drogue (or basket) shaped like a shuttlecock at the end of the fuel hose, and a telescoping boom to carry the line. The use of these devices could feed fuel six times faster and do so at higher speeds and in bad weather.

Today, the Boeing KC-135 Stratotanker is the premier refueling airtanker for the U.S. Air Force, along with the Navy, Marine Corps, and aircraft of allied nations. The KC-135 is also capable of simultaneously refueling two aircraft. Mid-air refueling is commonly used in military aircraft as well as Air Force One’s Boeing 747-200.

The connection between the KC-135 and it’s receiving aircraft include nozzles, in-flight refueling couplers, hose, other receptacles, and drogues. A drogue is a netted type of expandable basket in the aerial refueling system which stabilizes the hose, providing a funnel guide insertion into the receiver aircraft’s intake probe.

In performing aerial refueling, the tanker plane and receiver aircraft fly in formation. The receiver moves to a position below and behind the tanker, allowing a safe distance for the boom which is guided by director lights or directions radioed by the boom operator on the tanker. Once in position, the operator extends the boom to connect its nozzle with the receiver aircraft’s fuel receptacle system. The fuel is then pumped through the boom into the receiver aircraft with the capability of transferring fuel at a rate of 1,200 gallons per minute.

Airspace for Refueling

The United States Air Force has numerous air refueling tracks and anchor areas specifically designated for air refueling (AR). These refueling tracks and anchor areas are boundaries, altitudes, and regions of communication which are subject to change, yet are updated and published in daily and weekly airspace control plans. Essentially, they serve as designated airspace for refueling aircraft and are subject to change for defense and logistical purposes.

For example, during Operation Desert Shield in 2006 the US Air Force had two side by side refueling track zones over central Saudi Arabia featuring two KC-135 tankers, each for use by Navy aircraft. Large Navy strike groups from the Red Sea would send air tankers to these tracks ahead of the strike aircraft. Once the strike aircraft were topped off, the tankers took up station to the right of the track thereby providing a secondary tanking point. An additional track was also maintained close to the northwest border for E-3 AWACS aircraft and any additional Navy aircraft needing emergency fuel. These 24-hour air-refueling zones enabled the intense air campaign during Desert Storm.

The Evolution Continues

In September 2019, the first flight of the Boeing MQ-25 Stingray took place. The MQ-25 is an aerial refueling drone which grew out of the earlier Unmanned Carrier-Launched Airborne Surveillance and Strike (UCLASS) program. In September 2021 Defense News reported the once the MQ-25 is fully operational it will refuel every receiver-capable platform including the E-2 Hawkeye Airborne Command and Control Aircraft.

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