How does Aircraft Navigation system work?

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Aircraft Navigation System


Aircraft Navigation System

What is Navigation?

Finding the way from one place to another is called navigation. During the early period of flight, a specialized member of the crew, called navigator, used to mark a course from start to destination either on paper or a map. Such a task was complicated as it involved geometrical instruments and calculations. Today, aerial navigation has become a near-perfect art. Both external navigation aids and onboard systems help navigate any aircraft over thousands of km with high accuracy.

Main navigation methods are:

  1. Pilotage
  2. Dead Reckoning
  3. Radio
  4. Celestial navigation


Aircraft cockpit


NAVIGATION METHODS

(I) Pilotage or Piloting (based on visual landmarks)

In this most common method of navigation, the pilot keeps on course by following a series of landmarks on the ground.
Before takeoff, the pilot prepares a plan and draws a line on an aeronautical map to indicate the desired flight course and note various landmarks such as buildings, roads, rivers, bridges etc.
As the aircraft flies over each of the landmarks, the pilot checks it off on the chart or map.
If the aircraft does not fly directly over the landmark, the pilot will know that he has to correct the course.

(II) Dead Reckoning

Dead reckoning is navigating the aircraft completely by means of computations based on time, airspeed, distance, and direction.
The products derived from these variables, when adjusted by wind speed and velocity provide direction and ground speed.
The direction which is being predicted tends to take the aircraft along the intended path and the ground speed establishes or produces the time to arrive at each checkpoint and the destination with respect to each other.
Dead reckoning is not always a successful method of navigation due to changing wind direction. It was used in the early days of aviation.

(III) Radio navigation

Radio navigation is used in almost all aircraft by the pilots. These pilots have the potential to find out from an aeronautical chart what and which radio station they should tune to in a particular area or region.
They can then tune their radio navigation to a signal from this station. A needle on the navigation equipment tells the pilot where they are flying and whether they are on course or not.

(IV) Celestial navigation

Based on navigational reference to heavenly bodies like Sun, Moon, planets, stars etc.

Aircraft Celestial Navigation

(V) Satellite navigation

Navigation through use of data broadcast by a satellite-based transmitter.

(VI) There are special methods for navigating aircraft across oceans. Three commonly used methods are

Inertial Navigation System (INS)
INS is a navigation system which utilizes the incorporation of motion sensors i.e, accelerometers and also rotation sensors, that is gyroscopes along with an embedded computer system to constantly determine (via dead reckoning) the various parameters of aircraft's flight like the position, orientation, and velocity of the aircraft. These parameters are determined with reference to a starting point and there is no need for any external references.

Long Range Navigation (LORAN) 
This system employs a terrestrial radio navigation system which enables aircraft to determine their position and speed from low frequency (90 – 110 kHz) radio signals transmitted by fixed, land-based radio beacons, using an onboard receiving unit. LORAN is being phased out in preference to GPS.

Global Positioning System (GPS)
The GPS, as we all know, is a space-based satellite navigation system that provides location and time information in all weather and climatic conditions, anywhere on or near the Earth where there is an unobstructed line of sight to four or more GPS satellites.


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