Navigation
Because IFR flights often take place without visual reference to the ground, a means of navigation other than looking outside the window is required. A number of navigation systems are available to pilots, including ground-based systems such as DME/VORs and NDBs as well as the satellite-based GPS system. In addition, air traffic control may assist in navigation by assigning pilots specific headings to fly, known as "radar vectors". The majority of IFR navigation is given by ground- and satellite-based systems, while radar vectors are usually reserved by ATC for sequencing aircraft for a busy approach or transitioning aircraft from takeoff to cruise, amongst other things.
Modern flight management systems have evolved sufficiently to allow a crew to plan a flight not only as to route and altitude, but to specific time of arrival at specific locations. This capability is used in several trial projects experimenting with four dimensional approach clearances for commercial aircraft, with time as the fourth dimension. These clearances allow ATC to optimize the arrival of aircraft at major airports, which increases airport capacity, and uses less fuel providing monetary and environmental benefits to airlines and the public at large respectively.
- Required navigation performance (RNP)
- ADS-B
Read more about this topic: Instrument Flight Rules