Aerial refueling is a process of transferring fuel from one aircraft (the tanker airplane or the refueling airplane) to another airplane (the receiving airplane) during flight. The procedure allows the receiving aircraft to remain airborne longer, extending its range or loiter time on station.
Refueling airplanes can either be originally manufactured as refueling planes (i.e. the original purpose of the airplane is to serve as a refueling airplane), or alternatively, be converted from an existing airplane originally intended to serve a different purpose, e.g. a passenger airplane.
An example of a refueling airplane that is originally manufactured as a refueling airplane is the military aerial refueling and strategic transport aircraft Boeing KC-767 developed by Boeing from its B767-200 jet airliner.
An example of a refueling airplane converted from a passenger airplane is the B767 Multi-Mission Tanker Transport (MMTT) that was converted by Israel Aerospace Industries from secondhand B767-200ER airplane.
A known parameter related to the take-off and the landing attitudes of airplanes is a tail-strike pitch attitude that is defined as a critical attitude between a longitudinal axis of the airplane and the ground line, at which the tail section of the airplane contacts and strikes the ground. Such a strike can happen if the attitude of the airplane is equal to or above the tail-strike pitch attitude during take-off or landing of the airplane. Therefore, when operating the airplane during take-off or landing, the pilot has to pay attention that the attitude of the airplane is below the tail-strike pitch attitude, so as to prevent a tail-strike event.
Tail strike is an aviation term that describes an event in which the rear end of an aircraft strikes the runway. This can happen during takeoff of an affixed-wing aircraft if the pilot pulls up too rapidly, leading to the tail of the airplane's body touching the runway. It can also occur during landing if the pilot raises the nose too aggressively.
FIG. 1A illustrates a typical take-off procedure of an airplane, and FIG. 1B illustrates a table including data taken from flight manuals of different airplane models such as: B767-200, B767-300 and B767-400, and their corresponding flight parameters, such as: Liftoff Attitude, Minimum tail clearance and Tail Strike Pitch Attitude (discussed above). The Liftoff Attitude is the preferred attitude of the airplane at which the airplane should take-off, and the Minimal Tail Clearance, which is shown in FIG. 2B, is the minimal distance between the lowermost point of the airplane's tail section and the ground during take-off. A tail clearance below the minimum tail clearance can result in tail-strike.
In order to prevent tail-strikes during take-off of the airplane, the pilot has to follow flight performance and operation procedures related to parameters such as: a pitch rate, a decision speed (V1), rotation speed (VR) and a take-off speed (VLOF). The pitch rate is the rate at which the yoke of the airplane is pulled. The decision speed (V1) is a calibrated airspeed on the ground at which, as a result of engine failure or other reasons, the pilot assumed to have made a decision to continue or discontinue the takeoff. The rotation speed (VR) is the speed at which the aircraft's nosewheel leaves the ground. The take-off speed (VLOF) is the speed of the airplane at which it leaves the ground. By following the flight performance and operation instructions, the values of the Liftoff Attitude, the Minimal Tail Clearance, and Tail Strike Pitch Attitude can be controlled, and a tail-strike can be prevented accordingly.