An overhead irrigation system and a method of controlling it whereby a main irrigation pipe, supported on towers, is moved laterally across a field. The towers at the extremities of the pipe are independently driven while the remaining towers move in response to misalignment between pipe segments caused by the motion of the outside towers. Proper overall direction of the system is maintained by a path sensor which detects deviation from the designated path and corrects it by slowing down the tower at the end toward which the correction is required, thereby causing the entire unit to pivot about a point on or beyond and in line with the end of the unit. Two-way misalignment sensors are capable of propagating a path correction signal along the entire length of the unit and in either direction. An engine, generator and pump are mounted in a sling support hung from the pipe.