Questions for Fighter Controllers

[c-bert]

Gents,

A couple of Q's that I hope someone on here can help me with:

What is the difference between an SSR and an IFF with regard to controlling aircraft out over the North Sea? If your IFF is providing height data is it any different from a Mode 3 SSR?

What are the controllers (thinking about the ASACS boys) limitations on providing a service if their SSR/IFF is U/S? Basically, can you give a full RIS/RAS/RC without an SSR?

What class of airspace is it out over the North Sea?

Don't think there is any scope for restricted stuff in there so I apppreciate any sensible responses (and banter of course) that I get.

Many thanks in advance :ok:

[Wader2]

What is the difference between an SSR

SSR is Secondary Surveillance Radar. It depends on a transponder in the aircraft.

and an IFF with regard to controlling aircraft out over the North Sea?

IFF is Identification Friend or Foe and is an SSR.

If your IFF is providing height data is it any different from a Mode 3 SSR?[

Confusion.

IFF on its own does not provide height. Mode 3 SSR is simply One IFF Mode. The Mark 10 (12?) IFF has 4 (5?) modes. Mode 1 is a military specific mode. Mode 2 is a military unique identifier. It may identify a single platform or a single unit (multiple platforms). Mode 3 is a general ATC code and identical in effect to civilian SSR Mode A.

SSR Mode A does not provide height either.

Height is provided by Mode C and may be ordered by at ATC unit as Squawk Mode C or Squawk Altimeter.

What are the controllers (thinking about the ASACS boys) limitations on providing a service if their SSR/IFF is U/S? Basically, can you give a full RIS/RAS/RC without an SSR?

No.

What class of airspace is it out over the North Sea?

The North Sea is divided into various classifications of airspace from danger areas, airways lower and upper airspace. In otherwords almost all the classes of airspace exist over the North Sea including HPZs.

[c-bert]

Thanks Wader2. A bit more detail. On a job I'm doing, a certain British company is calling its SSR an IFF. I can't work out why and their answers haven't been compelling. However, it is capable of decoding Modes 1-5 (4, as I understand, it being a unique identifier and hence an IFF).
Anyway, that aside, can a controller provide any radar service without the SSR or is the height data essential to provide deconfliction?

Following on from that, if the SSR fails mid-games will the controller have to hand off all the guys he is working?

[Wader2]

If the controller is using a primary radar and tracking an air vehicle using skin paints then information may be given in relation to any other air vehicle that is transponding or not. In the case of non-transponding targets that may not provide a good skin paint there may be late warning of traffic.

Information based on skin paints may also be limited when the air vehicle is flying near heavy clouds. Warnings or information may be given in the absence of known height information. If the subject aircraft has no Mode C but a declared flight level then warning may be restricted to Mode C equipped aircraft that present a confliction.

If the conflicting aircraft does not have Mode C then avoidance or information may be given even when there is a large height separation. Pain in the butt springs to mind.

When you talk of SSR failure and mid-games this implies loss of SSR with the subject and not with a stranger. Depending on the type of airspace I would imagine that the game could continue. If the airspace was closed to not participating aircraft and the height of the subject aircraft was known to the controller then there should be no problem. If the airspace was open, and a third party controller needed height information on the subject aircraft, then depending on inter-unit coordination th game might continue or not.

In some airspace the carriage of a serviceable IFF and/or Mode C is essential. In that case it is game, set and match.

As for SSR being sold as IFF, it is a generic term and Mode 4 certainly means IFF capability. Certainly they would not sell IFF to BA.

Health warnings apply as I haven't checked the Mil AIP.

[Sentry Agitator]

C-Bert

Secondary Surveillance Radar is the generic term used to describe most civilian systems which allow for Mode 3 and Mode 'C' to be displayed to our ATC brethren. I believe that ATC don't generally use Primary Radar data anymore but display SSR plots only?

As Wader quite rightly points out the Ident Friend or Foe gives more information to military users in an operational environment.

Therefore you will normally find SSR/IFF quoted together when talking about military Search Radar sytems as we Mil types have to see our civvie mates in a routine training environment.

The Mil AIP and JSP552 are 'right rivetting reads'and will give you all the information you require about ICAO classification of airspace plus the rules and regulations we have to abide by. However, if we lose SSR/IFF during mid-vul and depending upon what type of airspace we are operating in, then we can simply limit, downgrade or change the radar service we have applied or reduce the altitude blocks allocated to the assets as necessary.....it really is that easy!

SA

[Monkey Madness]

I believe that ATC don't generally use Primary Radar data anymore but display SSR plots only?

Not correct (wish it was though!!!):}

Operational uses of SSR Mode 3A & 3C:

a) Establish & maintain ident of an a/c
b) Establish the posn of an a/c
c) Facilitate transfer of a/c between ATC units
d) To supplement primary radar information (i.e when a/c are in Wx clutter/radar shaddow etc)
e) To provide navigational assistance when requested by the pilot
f) To provide a radar service in the absence of primary radar, but only under specified conditions
g) to detect aircraft subject to distress/rad fails/unlawful interference

In practice, SSR is almost always used in conjunction with primary radar. SSR is only used on it's own as a temp measure. The use of SSR on its own must be authorised and the pilot must be informed.

Wader 2 is correct though....

Mode 1 - Military Parentage Code.
Mode 2 - Military Individual Code.
Mode 3a - The 4 figure squawk.
Mode 3b - Not used in Europe (its a civil thing)
Mode 3c - Coded Height Information
Mode 3d - Not used as yet world wide (I believe)
Mode 4 - Have not got a clue, but know its important to the Scopies

Clear as mud - all the above is from a blurred memory, but if i have made a mistake please let me know

MM:ok:

[ORAC]

Slide 6 has a list (http://www.raytheon.co.uk/news_room/files/tech_innovation_speech.PDF)of the new NATS radars and Mode-S sites. Raytheon got the contract to build and install them in 2003. 12 sites with Primary Search Radars (PSR).

[c-bert]

Many thanks guys. Most helpful.
MonkeyMadness, please could you let me know which doc you got that list (SSR uses) from?

Editted to say I've found it in JSP 552. Thanks anyway.

[SpotterFC]

http://www.jcs.mil/j6/cceb/acps/ACP160C.pdf

Mode 1 doesn't necessarily provide anything more than an 'I'm here' response - coding is optional.

[trap one]

To clarify Sentry Agitator
If any Mil site looses IFF ie Mode 3/3c from its aircraft or the ability to decode then they would have to apply the full service along with its limitations. So If the Controller couldn't see any IFF and was in Controlled airspace then 5/10 miles or co-ordination based on pilots reported height (if they could see other Mode3/3c). If the aircraft looses its Mode 3/3c then as long as all other units are aware and co-ordination if required is done then he could in accordance with the rules stay in controlled airspace. Civil controllers would expect Mil to call them for co-ordination, so any Mil controller would with no IFF displayed to them (would if able) get into airspace that would allow them to give RIS/RAS/FIS ASAP.

[buoy15]

Mode 4 is encrypted and is specifically for military use
In the CONUS, IFF/SSR is a no-go item - they will not let you get airborne if it's down
We always carried a spare box on exercises. However, if we had problems prior to T/O, we wangled it by explaining it had to remain off to avoid interference to other on-board sensors and would do a confirmation check when airborne
When it still didn't work, they let us continue because we had come a long way to take part - well done VACAPS

[c-bert]

One more for you.
Can SSR/IFF resolves plots in azimuth? That is to say, can a controller get bearing information on a contact purely by reference to SSR?

[MightyGem]

Yes, because the SSR transponder only replies when interrogated by the radar. So, as the radar knows where it was looking when the transponder replied, it knows the bearing to the target.