Properties:

A fixed number of components and/or items, that effects horizontal and vertical guidance for the automatic or manual approach and landing of an aircraft during zero visibility conditions. The set is self-contained in the aircraft, and is not dependent on external or ground based electronic navigation or guidance equipment, although the supplementary use of such facilities is optional at the discretion of the aircrew. The guidance is affected down to and including the landing roll, as contrasted with approach limitations associated with equipment, such as instrument landing systems and ground controlled approach.