NAVIGATION SYSTEMS
Commercial airliners navigate with pinpoint accuracy using a number of references such as GPS, Radio Aids and an onboard Inertial Reference Systems. The systems are of varying accuracy levels, with GPS being the most accurate method but there are a number of other systems such as an internal navigation system which doesn’t use any external reference as well as some radio beacon receivers which are used for particular phases of flight such as the departure or arrival and approach segments.
These navigation systems consist of: Global Positioning System (GPS)
Inertial Reference Systems (IRS)
Radio Aids (VORs, DMEs, ADFs, ILSs)
At the start of the flight, the pilots load a predetermined route into the Flight Management System or Computer (FMS / FMC). This imposes the route of the flight onto a moving map which the pilots can monitor on their screens throughout the flight. The pilots can see other things around their flight path on their screens, like other airports, other aircraft, high terrain and bad weather.
GPS – Global Positioning System
This is one of the primary navigation sources and it's also the most accurate navigation system on most modern commercial aircraft, in some circumstances allowing the aircraft to perform maneuvers down to an accuracy of 0.1 Nautical Miles.
IRS – Inertial Reference System (IRS)
The IRS (older versions are referred to as Inertial Navigation Systems) is a self contained system that is able to track the aircraft position with no external reference. It uses a combination of accelerometers and gyroscopes to calculate any movement and acceleration of the aircraft across any of its three axis.
At the start of the flight, the crew inserts the aircraft’s exact location into the IRS. It then detects any acceleration across any axis and then calculates the aircraft position based on this movement.
Radio Aids
Radio beacons, normally located on land, send out radio beams which tell us the aircraft’s range and direction from that radio aid. This allows the aircraft’s computer systems to calculate the aircraft’s location. The more radio signals it receives, the more accurate the estimated position is.
These radio aids are typically referred to as VOR with (DME). Others include an NDB which purely
provides a pointer towards the beacon rather than any direct radial or distance information.
The navigation systems are extremely useful during the flight whit high pinpoint and accuracy. The most famous and used is the GPS global position system but there are other used from others countries such as Galileo, Beidu, Glonass, Qzss and Navic.
The IRS inertial reference system can be used without external interference it is self contained with a good margin from the real aircraft position.
Radios as VOR NDB are still used although its use is less each day.
So the automation mainly on navigation system certainly reduces the pilots workload, however the pilots always have to remember and to be trained to raw data procedure which means to handle the aircraft in the even of an automated system failure. The pros of good navigation system is the reduce of workload and precision and the cons it could let the pilots without airman ship proficiency, what could cause loss of control, lack of fuel, disorientation, loss of situational awareness and an accident.