The air navigation is concerned with the systematic movement of aircraft in space, including theoretical foundations, flight planning and implementation.
For air navigation the same techniques as commonly used in navigation, but with a different weighting. Each aircraft, whether balloon, glider, aircraft engine or jet aircraft ( "Jet" ) moves with a its own speed in three-dimensional space. Therefore a pilot to safely navigate, can perform the following five rules:
The order of these five sub-tasks corresponding to their average priority in manually controlled aircraft - among other things to ensure correct aerodynamic and airspeed as well as a sufficient altitude above ground. The priority may however (eg when using autopilot or in large or very low altitude ) to move. For example, under glider for the most important targets altitude and speed of each student pilot common mnemonic " speed is half the battle ".
Monitoring the attitude
The determination and periodic monitoring of attitude is not a problem in the daytime and normal weather conditions.
VFR (Visual Flight Rules VFR ) must the pilot to control the flight attitude using the horizon and the ground be possible. In wet weather or heavy haze, it can be impossible to substantially more difficult. Even experienced civil or test pilots can without sight of the surface Vertigo subject ie the spatial orientation of losing, without noticing this in the organ of balance or buttocks. The instrument flight rules ( Instrument Flight Rules IFR ) allow clouds or night flight. Here, the artificial horizon shows the attitude relative to the earth's surface to ( " direct system "); this most important navigation instrument can also be replaced by a combination of turn indicator and spirit level ( " indirect system "). The indirect determination of the spatial position of course requires a good imagination and some experience tested under stress.
As altitude increases, air pressure decreases. A barometric altimeter on board an aircraft can therefore be used to determine the altitude (Altitude ). Prior to takeoff for the current air pressure reduced the airport at sea level (QNH ) on the calibration scale of the altimeter can be set. This one standing on the ground plane, the height of the airfield above sea level (elevation) displayed normally. For flights in traffic patterns or in place close to the prevailing at the aerodrome air pressure ( QFE) is set on the altimeter, since only the relative height above ground is crucial here generally. With this setting, one standing on the ground plane, the height of zero is displayed. From an altitude regionally agreed ( often 5000 ft or 10,000 ft) is the altimeter on the so-called standard atmosphere ( 1013.25 mb) adjusted so that the same amount is displayed to avoid collisions in all aircraft. This setting is then flown on so-called flight levels.
A radio altimeter may additionally determine the altitude of the aircraft above the ground ( height). Here, a radio signal is transmitted from the aircraft to the ground, reflected by and received from the aircraft. From the time delay of the radio signal, the height can be determined. A usable display is obtained but only on flat terrain (eg the sea), because unevenness of the ground affect the display.
To determine the climb and descent of the aircraft the variometer is used. Here, the pressure difference of the air in the climb or descent is the measure of the vertical velocity.
The artificial horizon shows the pilot whether and how strong its engine is inclined along the longitudinal and transverse axis. The position of the horizon line to the alignment mark corresponding to the actual horizon. The price determination is carried out by means of magnetic compass or compass led indicator.
In the early days of aviation was flown on sight. Spiers, mountains and other Peilpunkte were used to determine the position. This was known in the flyer language under Franzen. In aircraft with electrical power the radio location is used today. By pointing by multiple stations using a directional antenna, the exact course of the aircraft can be determined.
Totally independent of external signals is the inertial navigation. Before starting the exact location of the aircraft ( altitude, direction, longitude and latitude ) is input to the onboard computer. Three accelerometers measure any acceleration and thus the course or speed change. A computer calculates from the data display on the screen.
One way of determining the position is in addition to the various methods of radio navigation satellite navigation (GPS, GLONASS, or Galileo). About pointing by several satellites, the own position can be established to within a few meters, the height determination is, however, less accurate. This inaccuracy is due to atmospheric changes in signal duration and occurs especially over the equator. Cleverly distributed control stations ( in Europe the EGNOS system ) recognize the inaccuracy and send a correction signal. This will be sent free of charge and further processed by a so-called DGPS receiver in an adjusted signal for the navigation application.
This correction signal is too rare for the needs of civil aviation sent. In order for a GNSS can get an approval for instrument flight, it must be a coded because paid signal that is sent much more frequently can process. For Galileo, such a ( paid ) service reliability is already planned.
It is necessary to distinguish between
- The wind velocity magnitude and direction,
- The speed relative to the surrounding air and
- Ground speed.
The size of the wind speed (knots ) and the wind direction is provided by the meteorological service. This must be considered in flight planning.
The determination of the rate of aircraft relative to the surrounding air is done by dynamic pressure measurement with the airspeed indicator. The difference between the total pressure ( atmospheric pressure pressure due to the motion of the aircraft relative to the air ) and static pressure (air pressure) is measured and displayed ( IAS Indicated Air Speed). If this speedometer corrected for the air pressure / altitude is called the TAS (True Airspeed ). This then also serves to determine the velocity as a percentage of the speed of sound ( Mach).
The ground speed (GS, ground speed ) can be calculated from the speed and the wind speed and wind direction thus obtained.
Aeronautical radionavigation service
The term aeronautical radionavigation service different radio services for air navigation are summarized.