A turn executed by the aircraft during the initial approach between the end of the outbound track and the beginning of the intermediate or final approach track. The tracks are not reciprocal (ICAO). A base turn may be designated as made either in level flight or while descending, according to the circumstances of each individual procedure. It is one of the reversal procedures in which a specified outbound track and timing or DME (distance-measuring equipment) distance from a facility are followed by a turn to intercept the inbound track. The outbound track and the timing may be different for the various categories of aircraft. Where this is done, separate procedures are published.