SRA's question
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In what sense? An accurate SRA relies on using data which is as unadulterated as possible. Take out plot extraction and other processing and the target is more likely to be where it appears on the display.
This speaking as someone who learned how to do SRAs on a 3cm pencil-beam primary radar with the barest minimum of processing of the picture. SRAs terminated at 1/2 mile from touchdown - and on a good day you could see runway edge lights.
This speaking as someone who learned how to do SRAs on a 3cm pencil-beam primary radar with the barest minimum of processing of the picture. SRAs terminated at 1/2 mile from touchdown - and on a good day you could see runway edge lights.
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We used a 264 primary only for SRAs many moons ago.It was offset to the east of the field,but because the blip was quite big,the best results meant running the edge of the blip nearest the radar down the centreline.Otherwise they would be lined up on Asda car park.None of your processed radar then.
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Not sure what 'issues' you mean. The radar head would certainly need to be on the airport. But as far as I know SRA's can only be done using primary. We're certainly only allowed to do them on primary. I think there would be too many accuracy issues trying to use secondary.
IIRC an SRA radar needs a higher probability of detection (PD) than one used solely for surveillance. The radar update rate is also critical. That is why at old airfields that had 264 radars, the SRAs were conducted with a different radar...cannot remember the name of it now.
IIRC an SRA radar needs a higher probability of detection (PD) than one used solely for surveillance. The radar update rate is also critical. That is why at old airfields that had 264 radars, the SRAs were conducted with a different radar...cannot remember the name of it now.
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More to the point, are there any issues with using SSR to do SRAs? As radarman says, SRAs can only be done with primary present. But modern SSRs are probably as/more accurate than primary. So any good reason for the rule other than history?
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SRA's
radarman - I can think of a few NATS off airfield radars that are used for 2nm SRA - Pease Pottage for Gatwick, Debden for Luton/Stansted and Allanshill/Perwinnes for Aberdeen. But as has been mentioned a 2nm SRA is only in reality a cloud break so accuracy isn't outside the normal requirements of radar optimisation.
Interestingly SRA being a primary only function is a slight misdiscription since if the Primary radar is co-located with an SSR in most cases the primary position is set to that of the SSR. - certinly smooths the track!!
Interestingly SRA being a primary only function is a slight misdiscription since if the Primary radar is co-located with an SSR in most cases the primary position is set to that of the SSR. - certinly smooths the track!!
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Yes. SSR only outside CAS not a good idea...
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The regulations regarding radars used for SRAs are contained in CAP 670. In general;
11.5
11.1.1 When used for surveillance radar approach (SRA) purpose (i.e. primary only), the
accuracy shall be better than 1 degree of bearing and 55 Metres, + 5% of target range
(365).accuracy shall be better than 1 degree of bearing and 55 Metres, + 5% of target range
11.5
Rotation Rate
Here is the address of the CAP 670 document on the CAA website;
www.caa.co.uk/docs/33/cap670.pdf
Hope this answers your question
11.5.1 The effect of rotation rate on system performance shall be defined and justified (451).
11.5.2 A primary radar providing the positional data for the following services shall rotate at
the following effective minimum turning rates:
a) General TMA Zone and approach work, a rotation rate of 5 RPM (452).
b) SRA to 2 NM, a rotation rate of 10 RPM (453).
c) SRA to 1 NM, a rotation rate of 15 RPM (454).
d) SRA to 0.5 NM, a rotation rate of 20 RPM (455).11.5.2 A primary radar providing the positional data for the following services shall rotate at
the following effective minimum turning rates:
a) General TMA Zone and approach work, a rotation rate of 5 RPM (452).
b) SRA to 2 NM, a rotation rate of 10 RPM (453).
c) SRA to 1 NM, a rotation rate of 15 RPM (454).
Here is the address of the CAP 670 document on the CAA website;
www.caa.co.uk/docs/33/cap670.pdf
Hope this answers your question