The main approach proceduresFebruary 28, 2020
Every day, countless aircraft take off and land around the world every second. The schedule is very tight and therefore fog, storms or cold weather should ideally not be a problem.
To ensure that every approach runs smoothly, there are different procedures for the approach.
The so-called “visual approach” is the simplest and takes place in very good weather conditions and daylight. In this case, the runway is located without any assistance and the flight path is determined by the pilot himself.
In former times, in the early days of aviation, in bad visibility conditions, one used to use a turning light or beacon to find the target. For small airfields this principle is still used today.
The radio beacon NDB (Non-Directional Beacon) with radio waves was developed according to exactly the same principle. The beacon emits radio waves which enable position finding on board. To find the correct course for the approach, only the correct frequency of the NDB was set. In order to be at the right distance and altitude, exact approach charts were created. Nowadays NDB approaches are becoming less and less important. This technique is increasingly disappearing and is being replaced by low-cost RNAV approach procedures. In case of emergency or at remote airports NDB approaches are still practiced today.
The VOR approach is an advanced version of the NDB approach. The VOR rotating beacon not only emits circular signals, but also has a timer that sends signals when the rotating beacon exceeds a certain point. The instrument on board only has to measure the time between the reception of the main signal and the point. So you know exactly what course you are on. This is also called “radial”.
A VOR-DME (Distance Measuring Equipment) is when the VOR is equipped with a distance measuring device. Through an exact determination of distance and the defined radial, very precise approaches take place.
In bad weather conditions, such as dense fog, the VOR-DME is of limited use. The procedure is not 100% secure against measurement inaccuracies and the pilot himself has to compare the distance and the altitude.
The ILS (Instrument Landing System) was initially developed for military requirements. With this instrument several signals are transmitted. For the lateral part the “Localizer” is used and for the vertical path, the “Glideslope”. The radio transmitters are located directly at the runway and show the pilot an exact approach angle.
If you want to get a higher accuracy, you also need a DME (Distance Measuring Equipment) to check the distance exactly. The ILS has technical aids available. It monitors itself and gives an alarm in case of deviations.
ILS has been around since the 1950s. The categories of accuracy that have been established CAT I to CAT III, where the least accurate version of ILS is CAT I.
An instrument approach system consists not only of ground-based assistance but also of numerous requirements from the cockpit. When controlling an aircraft, at least three autopilots monitor each other.
At Panamedia, flight students are trained for exactly these situations. Do you have any questions about our courses? We will be pleased to advise you.
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