Page 901 - engelsk

Navigation

The SSR Radar system was invented, a further development of the primary radar,

where the aircraft is equipped with a transponder, which sends answers back to

the radar when it picks up the primary radar signal.

The ground station system is called an interrogator.

Together with the primary radar signal, an interrogation pulse is transmitted.

The thick white line in
the drawing here

symbolizes the radar
signal towards the

aircraft.

9.10.4.3 The transponder

The signal is processed in the aircraft's transponder, which sends a response

signal that can be the set code, the flight altitude and the aircraft's registration

letters.

The response from the
transponder in the aircraft consists

of 4 digits between 0 and 7.

There are 4096 different possible responses from the aircraft, depending on

which digits the pilot has set the transponder to.

If the selector switch is set to OFF, the transponder is switched off.

We set the selector switch to SBY (Stand By) when we reach the point in the

checklist during the start-up of the electrical equipment. In this position, the

transponder warms up so that it is ready when we set the transponder to ON on

the runway just before take-off.

Flyveteori PPL(A)(UL)/LAPL Henning Andersen, Midtjysk Flyveskole© 2025 901