Navigation Procedures

Chapter 18.3

What is AIR NAVIGATION?

AIR NAVIGATION has a common relationship with MARINE NAVIGATION but it is also an independent method: with AIR NAVIGATION procedures you can easily navigate over land and mountains. The National Aeronautics and Space Agency, NASA, has defined it as an independent form of navigation:

AIR NAVIGATION:
The art of determining the geographic position, and maintaining the desired direction, of an aircraft relative to the earth's surface.

PILOTAGE, the piloting of an airplane using landmarks

PILOTAGE is not really a method of navigation, it consists in constantly comparing the indications of the visual flight chart with the visual landmarks (topography), headings and the comparison between the calculated journey time and the actual time for a journey.

Dedicated visual flight charts are required for PILOTAGE, which emphasize the nature and structure of the terrain.

PILOTAGE is very important for:

• visual approaches and take-offs
  

• visual mountain flights
  

• training flights in the vicinity of an aerodrome
  

PILOTAGE is limited to visual flights over well-structured terrain. Other flights such as flights over water must be carried out using the AIR NAVIGATION method.

DEAD RECKONING (DR) NAVIGATION

DR NAVIGATION is the fundamentals of all true navigation procedures and is the prerequisite for understanding methods using technical support such as radionavigation and satellite navigation.

Procedures based on estimation-based navigation are less dependent on weather conditions than PILOTAGE, if the aircraft is equipped properly.

The procedure of DR NAVIGATION

Knowledge of the triangle of velocities is essential and is used to calculate the corrections for the following legs:

Above CHECKPOINT 1 you set HEADING to checkpoint 2. This contains the WCA, VAR, and DEV corrections.

The calculated time between CHECKPOINT 1 and 2 taking all corrections into account is the ESTIMATED ELAPSED TIME / EET.

After the EET has elapsed you determine your position by comparing the actual position with the predicted position, and you see if you had calculated the WCA correctly. This comparison is the basis for calculating the heading from the current position to the next checkpoint.

The procedure of DR NAVIGATION

Example:

Flying over checkpoint 1, you take the planned route. After the expected time (EET) has elapsed you determine your true position:

You were moved by the wind by a distance equal to the drift.

The drift value provides direction and wind strength and is the basis for calculating WCA and subsequent headings.

Visual Navigation

This is usually a combination of the PILOTAGE and DR-NAVIGATION procedures. We also refer to it as «terrestrial navigation».

To determine the position and orientation, the ICAO visual flight map is compared with the landmarks and terrain reliefs.

The route segments are connected to the calculated positions.

Navigation Procedures Based on Estimated Navigation

Radionavigation

In radionavigation, the position and course to be maintained shall be determined by means of ground transmitters and appropriate instruments on board the aircraft.

Instruments are used to determine the LINE OF POSITION, LOP. LOPS are lines between the airplane and ground stations. Intersection points of multiple LOP’s allow to determine the exact position.

Navigation Procedures Based on Estimated Navigation

Astronavigation

Determining position using stars is the oldest form of navigation and requires a good knowledge of celestial mechanics and a wide range of accessories in the form of maps, ephemerides, sextants and drawing instruments.

The positions (FIX) are determined using the angles with the stars. To define the route from one FIX to the next one uses estimated navigation. Since the introduction of the satellite navigation and the less dependable inertial navigation, guidance from celestial bodies has lost its importance in aviation. Many of the terms of navigation used today, however, originate in astronavigation.

Navigation Procedures Based on Estimated Navigation

Inertial Navigation, INS

Inertial navigation works independently from any infrastructure on the ground or in space, based on the principle of acceleration measurement. On a platform stabilized by gyroscopes, weights are arranged according to the axis of flight. By measuring their movement in an electromagnetic field, the data for the calculations of the route and the position are obtained.

Inertial navigation was originally invented for spatial navigation, the reason being the spatial stability of the system, and for the purposes of land navigation the system had to be modified for the Earth’s surface and to the magnetic and geographical North Pole. Inertial navigation for aviation is therefore «earthbound».

For reasons of cost, the INS is used mainly in large aircraft, and the fact that the INS is independent of any infrastructure makes it equally suitable for military aviation.

Navigation Procedures Based on Estimated Navigation

Satellite Navigation, GLOBAL POSITIONING SYSTEM, GPS

Satellite navigation makes it possible to determine the position and directions in a very precise manner in a minimum amount of time.

Relying solely on satellite navigation means that it depends on a single source of information. In the event of a device failure or reception difficulties, there will no longer be any indictions, and the determination of the position and the orientation shall be taken up by conventional means.

The determination of position using satellites is widely used on the ground as well as in space, in maritime navigation, traffic control, agriculture etc.