KC-135 Stratotanker (Unusual Aircraft Collection)

The KC-135 Stratotanker is a dedicated aerial refuelling plane.   It allows fighters and other military aircraft to fly more missions by transferring fuel to them near where they're operating, rather than having to go to a distant air base to refuel.

United States Air Force tankers like the KC-135 use a "flying boom" to transfer fuel.   This consists of a long metal pipe which expands like a telescope, the small "wings" near the end allowing a boom operator or "boomer" lying in front of a window at the back of the plane to maneuver it into the receiving plane's fuel receptacle.   TheUnited States Navy and Marine Corps, as well as foreign air forces, prefer the "probe and drogue" method, with a metal tube or "probe" on the receiving plane, and a basket or "drogue" attached to a flexible hose on the tanker.   The receiving plane's pilot flies towards the tanker and inserts the probe into the drogue, and fuel transfer then begins.   This method allows several planes to refuel at once from the same tanker, since it's possible to have a hose extending from the fuselage, and others extending from the wings.   However, the boom allows fuel to be transferred to large aircraft more quickly.   Another advantage of the boom is that a fighter or other small plane with engine trouble or a large fuel leak can hook up to the boom and then shut down the engine and be towed back to base, where it can glide down.   This technique was used on many occasions during the Vietnam War.

The Stratotanker was developed at the same time as the Boeing 707 airliner.   It was supposed to be nearly identical, but airlines decided they wanted the plane to be larger, so the two planes ended up with much less in common.   For many yearsBoeing had been building only military aircraft like the B-47 Stratojet and B-52 Stratofortress, but the 707 allowed them to break back into the airliner business.