SSR Flashcards
SSR ground station can ask questions by sending out trios of pulses on UHF …MHz with one of three spacings that will be recognised by the aircraft
Aircraft will respond to the interrogation with a longer train of pulses on … MHz according to cockpit selections
1030
1090
What does ground SSR transmitter do to suppress sidelobes?
Pulse 2 is a standard 2 microseconds behind pulse 1
The time interval between pulses 1 and 3 of the SSR ground interrogation dictates the sort of question that is asked (the mode) and pulse spacings for mode A and C respectively are…
8 microseconds
21 microseconds
Aircraft’s SSR response to interrogator is a stream of pulses … microseconds long framed by … between which, there is space for … additional pulses pairs in which …. possible number combinations can be sent (effectively binary code)
20.3
two frame pulses
12
4096
An additional ident pulse can be sent …. microseconds after the pulse train which causes the return on the radar screen to bloom for … seconds. Known as ident or special position identification (SPI) – not transmitted in 12 bit code
4.25
25
What SSR Mode A code indicates a system malfunction?
0000
If altitude readout is more than … ft out controller may ask to select Mode A.
Some European states have filed a variation to the ICAO standard and reduced it to … ft
300
200
What is fruiting with regards to SSR?
If aircraft are in range of two ground interrogators the may reply to both. The received replies may be for the wrong station
What is garbling with regards to SSR?
If two aircraft are on the same bearing from a station and closer together than 1.7NM they may produce overlapping replies to the ground interrogator
If the P2 pulse is stronger than the P1 and P3 pulses, the aircraft is in what area?
the side lobe area
accuracy of mode s alt reporting?
25 ft
