Based on (or converted from) the airframe of the Il-76M military freighter, this
aerial refueling tanker aircraft entered service in 1987 to replace the elderly and incapable
Myasishchev M-4 "Bison".
Fitted with three Severin/UPAZ PAE external refueling units, one under each
wing (which are reportedly sometimes removed on missions involving only a single receiver
aircraft) and one mounted on the port side of the rear fuselage, the Il-78 is a three (or
sometimes two) point air-to-air probe and drogue tanker aircraft capable of delivering fuel at
a rate of 900 to 2,200 liters/min.
Internally the Il-78 has a pair of enormous cylindrical, pallet-mounted fuel
tanks in the cargo hold, together containing 35 tonnes of the aircraft's 100-tonne total
transferable fuel load. The refueling process is monitored by an observer occupying the former
tail gunner's position and controlled from the flight engineer's station in the cockpit.
Receiver/tanker rendezvous is facilitated by a simple homing radar housed behind a broad flat
aft-facing radome located forward of the standard rear loading ramp.