01-02-2013, 11:58 AM
APPLICATION IN AVIATION (Automation approach and landing using GPS)
1APPLICATION IN AVIATION.ppt (Size: 3.68 MB / Downloads: 56)
AIR TRAFFIC CONTROL
Air traffic control is “a service provided by the appropriate authority to promote the safe, orderly, and expeditious flow of air traffic”.
In India the authority for ATC is the Airports Authority of India.
In the United States, the authority for ATC is the Federal Aviation Administration(FAA), Which operates and regulates the National Airspace System(NAS). The NAS encompasses “the common network of airspace ,airports, navigation aids and air traffic control equipment across the United States.
FUNCTIONS OF AIR TRAFFIC CONTROL
Procedures and regulations by which ATC Systems operates and the organization of air space in the form of routes for departures, en route airways, and arrivals.
Human air traffic controllers who are responsible for providing the ATC service;
Automation Systems (eg., Computers and displays) providing information to the controllers on the status, location and separation of aircraft in the system.
VHF OMNI-DIRECTIONAL RANGE(VOR)
This facility operates in the range 108-136MHz in the VHF band. The range transmitter radiates two patterns, distinguishable by different modulations, one of which is Omni-directional and carries the modulation of a reference 30 Hz sinusoid, while the second pattern is a figure-of-eight rotating at 30rps. The radio frequency phases of the two are locked. The Omni-directional radiation has a much stronger field than the figure-of-eight one and therefore, the combination gives rise to a rotating cardioid.
INSTRUMENT LANDING SYSTEM
The Instrument Landing System (ILS) comprises the units localizer, glide path and marker beacons. The localizer defines a vertical equi-signal plane which passes over the centre line of the runway and the glide-slope, and equi-signal plane inclined to the horizontal at the desired angle of descent(3º).
The localizer operates in the VHF band (108-110 MHz) and consist of a transmitter with an antenna system, the radiation of which has two lobes, one with a predominant modulation of 90Hz and the other with a predominant modulation of 150Hz. The two signals are equal and this equi-signal course is aligned with the centre line of the runway.
GBAS PRINCIPLE
GBAS is a Ground Based Augmentation System (GBAS).
GBAS comprises - surveyed ground station with multiple GPS receivers, a VHF link and one or more pseudolites.
Ground station makes the differential corrections and broadcast on VHF frequencies along with an integrity message to aircrafts within a radius of 20 to 30 miles from the airport.
Pseudolites are ground based transmitters.
Pseudolites transmit PRN codes similar to the C/A codes thereby providing additional ranging signals to the user aircraft, which increases the availability.