Tanker 101
- The process of transferring fuel in flight between aircraft is commonly known as air refueling. It normally involves two aircraft flying 35 feet apart at altitudes ranging from 14,000 to 30,000 feet and speeds ranging from 190 to 320 knots indicated airspeed (KIAS).
- Air refueling is used to extend the range of aircraft, allowing fighters and bombers to fly deeper into enemy territory to drop their bombs; increase the loiter time of intelligence and surveillance aircraft; speed the delivery of cargo by airlift aircraft by allowing them to bypass ground refueling stops; and allow receivers to carry heavier loads of weapons and cargo.
- Fuel is transferred via two methods: an air refueling boom or a hose and drogue system. The air refueling boom is a rigid structure attached to the rear of the tanker aircraft. The hose and drogue system is mounted in a pod on the end of the tanker wing or in the rear of the aircraft.
- The air refueling boom was developed and perfected by The Boeing Company starting with the boom on the KB-29P tanker that entered service in 1950. Over the next half century, Boeing engineers continued to improve and enhance the air refueling boom. The fifth generation air refueling boom is currently in use on Boeing’s international KC-767 air refueling tankers.
- The air refueling boom is designed to allow for large quantities of fuel to be transferred as quickly as possible. In the current tanker competition, the Air Force is requesting a fuel transfer rate of 1200 gallons per minute. At this transfer rate, it would take 18 minutes to fill a 16 ft by 32 ft swimming pool (22,021 gallons).
- The hose and drogue system consists of a 70-90 foot hose that is trailed behind the aircraft. At the end of the hose is a basket that is aerodynamically designed to remain stable behind the tanker. Fuel is transferred at a much lower rate, typically between 400 and 600 gallons per minute.
- The receiver pilot is responsible for connecting a probe on their aircraft to the refueling coupling located in the center of the basket. In the U.S. military, the hose and drogue system is used to refuel Navy and Marine fighter aircraft, the V-22 Osprey tilt-rotor and helicopters.
- The air refueling boom is controlled by an inflight aerial refueling specialist or boom operator specially trained for this mission. The boom operator flies the boom with controls located inside the tanker that operate two small wings or ruddervators. Once the boom is flown to the proper location in front of the receiver aircraft, a smaller pipe is extended to make contact with the aircraft taking on fuel.
- The air refueling or AR mission follows a well-defined process to ensure the safety of both the tanker and receiver aircraft. ARs are accomplished on published air refueling tracks or in air refueling anchors (see below).
- The air refueling track consists of an air refueling orbit point where the tanker flies in a holding pattern, and an air refueling initial point (ARIP) where the receiver aircraft enters the air refueling track. The tanker departs the orbit and flies toward the receiver aircraft in order to arrive at the air refueling control point (ARCP) at a specific time. While the two aircraft are approaching each other at more than 800 mph, they are separated by 1,000 feet of altitude.
- At a predetermined range, the tanker executes a 180-degree turn to roll out one mile ahead of the receiver aircraft. Once the tanker is identified by the receiver, the receiver is cleared to increase speed and climb to join up with the tanker.
- The air refueling anchor is a predefined box of airspace where the tanker arrives and orbits. Receiver aircraft enter the anchor at specific points and maneuver behind the tanker for refueling.
- In the early days of the U.S. Air Force, only a limited number of aircraft were capable of being air refueled. Today, the majority of aircraft in the Air Force can be air refueled.
