Chapter 10 Secondary Survaillance Radar (SSR) Flashcards
What are the advantages of SSR?
- no reflected pulses thus no clutter
- greater range for lower power
- can attach data (e.g. callsigns)
- can give immediate notice of notification of emergencies
What is the interrogator pulse pair frequency?
1030MHz
What is the response frequency?
1090MHz
What frequency band does SSR operate in?
UHF
What is SSR limited by?
Line of sight
What is the pulse pair spacing on mode A and what does it transmit?
Pulse pair spacing = 8 microseconds
Only transmits squawk code
What is the pulse pair spacing of mode B?
17 microseconds
What is the pulse pair spacing of mode C and what does it transmit?
Pulse pair spacing = 21 microseconds
Transmits mode A and pressure altitude
What is pulse pair spacing of mode D?
25 microseconds
What is the pulse pair spacing of mode S and what does it transmit?
Pulse pair spacing = multiple
Transmits mode C and other flight data
What does each interrogation in mode A compromise of?
3 pulses: P1, P2 and P3
What is the purpose of P2 in mode A?
Prevents any false readings due to sidelobes
What has occurred if P2 is bigger than P1 and P3?
A side lobe has been found
What is accuracy of altitude on mode C?
Nearest 100ft
What does mode S improve?
Quality of integrity of detection, identification and altitude reporting
What must the crew be able set with mode S and why?
Flight ID to reduce garbling
What must all aircraft flying ILS have?
Mode S ELS compatibility?
What is fruiting?
When 2 or more ground stations are close together which may cause it to be detected by a different atc unit
Where is fruiting a problem?
In areas of high density traffic
What is garbling?
Occurs when 2 aircraft are within 1.7nm and in line with each other and the interrogator. The decoder can’t differentiate between replies.
What can garbling cause?
All or part of the returns may be cancelled or generate a false target on radar
What is the altitude accuracy of mode S ELS?
25ft
What aircraft require mode S EHS?
All aircraft over 5700kg or a max cruising TAS 250kts when operating in designated EHS airspace
