A pilot in combat attempts to conserve his aircraft’s energy through carefully timed and executed manoeuvres. By using such manoeuvres, a pilot will often make trade offs between the fighter’s potential energy (altitude) and kinetic energy (airspeed), to maintain the energy-to-weight ratio of the aircraft, or the "specific energy". A manoeuvre such as the "low yo-yo" trades altitude for airspeed to close on an enemy and to decrease turn radius. The opposite manoeuvre, a "high yo-yo", trades speed for height, literally storing energy in "the altitude bank", which allows a fast moving attacker to slow his closing speed.