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Surveillance Radar Approach - is this still available at any civil UK airfield ?

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Surveillance Radar Approach - is this still available at any civil UK airfield ?

Old 3rd May 2021, 08:18
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Surveillance Radar Approach - is this still available at any civil UK airfield ?

I haven't heard one of these in action for at least fifteen, maybe twenty, years. Leeds Bradford used to routinely offer them to runways 15 and 28 as they were decades ago. At first, half-milers with the Plessey 430 then one mile with the Watchman. The latter radar is still there but the old PPI monochrome screens are long gone. I guess any airfield which had ILS at only one end of the runway years back would have been in the same position, e.g. Bristol, Luton.
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Old 3rd May 2021, 08:41
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The AIP lists many airfields with this facility although if the airfield hasn't got a radar 'on site' it will almost certainly be a 2nm termination range so basically a cloudbreak procedure.
Controllers have to do a minimum number of SRAs per month to keep the C of C in their license valid.
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Old 3rd May 2021, 09:24
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Quite misleading to refer to it as a "cloudbreak", a term that must be at least half a century out of date. It is what is is, an instrument approach procedure with an appropriate OCA/H and is as accurate as the controller and the pilot performing it!

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Old 3rd May 2021, 09:26
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Most civilian airports no longer have them. Although in the north east Teesside and Humberside still do.
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Old 3rd May 2021, 09:52
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If I recall correctly we used to use Coventry for a SRA when I trained for my IMC rating in about 2010. I don't know if Coventry is open any more though. I seem to recall some drama or other about finances.
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Old 3rd May 2021, 09:57
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Did a very nice one, on a very windy day, into Aldergrove before the pandemic.....
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Old 3rd May 2021, 10:11
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Does availability of the SRA depend on the make and model of the radar, to any degree ? I believe the old Decca 424 and the Plessey 430 were geared as both general airfield radars as well as the SRA facility whereas the likes of the Marconi 264 weren't suitable for the job; something to do with the big blips, probably. I've never worked in ATC so please indulge any misunderstandings.

I don't know if the latest Raytheon, Thales etc. radars are approved for SRAs.
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Old 3rd May 2021, 10:13
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Most civilian airports no longer have them. Although in the north east Teesside and Humberside still do.
It would be more accurate to say that quite a few civil aerodromes still do have them!

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Old 3rd May 2021, 10:17
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I think Cambridge still does them.
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Old 3rd May 2021, 10:41
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As Stated controllers have to perform SRA’s regularly to stay current. Unfortunately a lot of airlines don’t want to do them, preferring an RNAV approach if the ILS isn’t available. If you want an SRA just ask would be my advice.

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Old 3rd May 2021, 10:42
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Originally Posted by Mooncrest View Post
Does availability of the SRA depend on the make and model of the radar, to any degree ? I believe the old Decca 424 and the Plessey 430 were geared as both general airfield radars as well as the SRA facility whereas the likes of the Marconi 264 weren't suitable for the job; something to do with the big blips, probably. I've never worked in ATC so please indulge any misunderstandings.

I don't know if the latest Raytheon, Thales etc. radars are approved for SRAs.
To a degree, in that only certain radars were sufficiently accurate to use for half mile SRAs: not so much the size, iirc, more to do with the ability to accurately plot the position. The flight check regime for SRAs of less than two miles was quite onerous, from memory, which increased costs. With the improvements in approach aids over the years, the need for radar with that degree of accuracy diminished to almost zero, there are better/cheaper ways of achieving the same result, now - the equipment may be able to do it, but the odds of having the right ATCO in the seat if the need arises is pretty slim. The currency & recency requirements make it difficult to manage at the bigger units - passenger jets don't really want to compromise their approach for the sake of ATCO training/currency. These days, most ATCOs will do more simulated SRAs whilst initial training, than they'll ever do in the real world.
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Old 3rd May 2021, 10:54
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Does availability of the SRA depend on the make and model of the radar, to any degree ?
Absolutely - as does the processing of the radar data and the display system used.

The principal characteristic of any radar is its wavelength; the shorter the wavelength, the more accurate the picture can be. But with radar, everything is a trade-off. A short wavelength radar will be limited in range and the return is likely to be relatively weak, on the other hand, it will turn quickly and give a rapid refresh to the picture. The Plessey 424 and 430 are both 3 cm radars. At the other end of the scale the classic, or traditional area radar, something like a Marconi 264, is a 50 cm radar - long-range, relatively long time between updates and, at range, blips the size of sausages. In the middle, at 10 cm wavelength, are radars which commonly have been used for aerodrome surveillance. These days, 23 cm radars are quite common because they provide a good compromise between the old really long-range radars and those which are good for terminal areas and aerodromes.

Radars which are used for very accurate surveillance radar approaches need to provide an accurate picture to the controller which is updated frequently. This is traditionally was done using 'raw' data on a classical glowing phosphor tube. In a modern radar the raw radar data is processed and commonly what the controller sees is a position symbol which is where the radar thinks the aircraft is (or is most likely to be). There are a number of approximations that can affect the position of the symbol relative to the actual location of the aircraft - this is why, where SRAs are still available, they are only used for approaches to 2 miles from touchdown or thereabouts. Although I agree the term 'cloudbreak' is rather outmoded, the reality is that at this range and aircraft will be at about 650 feet above the runway and so can be useful to enable aircraft to become visual beneath a layer of cloud in moderately poor conditions.

Now that you've got me thinking about them again it brings back how much fun they were to do and it was very satisfying to do a half mile SRA in poor conditions!
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Old 3rd May 2021, 11:14
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The ability to provide SRAs and the termination range were/are determined primarily by the equipment. 'Talkdowns' require precise information and therefore the shorter the wavelegth of the equipment and rotation rate of the scanner are crucial. So a Marconi 264 with a 50cm wavelength and scanner rotation of 4RPM useless......big 'blips' and very slow renewal of position. The Decca/Plessy 424, wavelength 3cm and scanner rotation of 20 odd RPM [forgotten the exact RPM...... long time ago!], excellent renewal of information enabled accurate presentation of aircraft position. The Plessey 430 with a capable scan rate of 44 RPM...... even better! The problem with the short wavelengths being the susceptibility to weather interference. So even with all the anti-clutter devices SRAs could be a problem, until the aircraft was within the last few miles of the approach.

However the technical ability of the radar was only part of the story. The real accuracy was determined by the ability of the radar operator and the guy flying the approach. So airfields such as Bristol, Luton and Leeds Bradford probably offered most success by virtue of the bad weather experienced and the frequent experience of based pilots.
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Old 3rd May 2021, 11:39
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Some very detailed posts here - most interesting reading. I expect providing several successive SRAs to inbound aircraft was a real feat of concentration for the controller and probably quite tiring. Not much good for them if they're supposed to be on a statutory break! I hope that didn't happen.

I often used to hear the Approach Controller offer the SRA for controller training purposes and, in my listening experience, it was rare for a pilot to refuse. Useful for aircrew as well in order to stay current - the ILS or NDB/VOR approach may not always be available.
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Old 3rd May 2021, 11:53
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Originally Posted by Mooncrest View Post
Some very detailed posts here - most interesting reading. I expect providing several successive SRAs to inbound aircraft was a real feat of concentration for the controller and probably quite tiring. Not much good for them if they're supposed to be on a statutory break! I hope that didn't happen.
In the days before statutory breaks, and the word "stress" hadn't been invented, my record was giving 42 x 1/2 mile SRAs in a 11.5 hour duty day, less a 45 break at the local pub for a pint and a ploughmans!
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Old 3rd May 2021, 12:17
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The Decca/Plessy 424, wavelength 3cm and scanner rotation of 20 odd RPM [forgotten the exact RPM...... long time ago!], excellent renewal of information enabled accurate presentation of aircraft position. The Plessey 430 with a capable scan rate of 44 RPM...... even better! The problem with the short wavelengths being the susceptibility to weather interference.
A minor correction, Helen - probably a typo - the higher rotation rate of the 430 was 40 rpm, in theory to cater for high speed aircraft on final, but in practice a useless facility as it tended to shake the console and the aerial apart. It was also self defeating as it limited the number of strikes on each rotation which was not good as it was a poor enough piece of kit anyway! Other factors not mentioned that contributed to its approval for 0.5 nm RTR were the short pulse length and narrow beam width which ensured accuracy - even if it did require considerable imagination to maintain the identification!

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Old 3rd May 2021, 14:23
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We stopped providing SRAs at EMA prior to my retiring in 2019, the reason being few airlines would do one at short notice for continuation training, Ryanair could accommodate only if ‘booked’ prior to the aircraft getting airborne inbound…..the club cessnas were willing but not overly representative! If the ILS was on maintenance most crew plumped for the NDB
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Old 3rd May 2021, 15:12
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Shame you never asked us in our helicopter, we’d have done it....
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Old 3rd May 2021, 16:14
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Conducted the last SRA in anger at yeovil westland in 2016, spent most of the time only doing them for currency.
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Old 3rd May 2021, 16:16
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I think I've posted this before, but for anyone who cares, here's the manual that came with a Plessy ACR 430 in the 1970s - hope I'm to infringing the copyright too much!

The 430 was a development of the 424 - essentially it was a 424 with the addition of the high beam. Both, I believe, were originally designed for use on ships. Despite some peoples' reservations, I always thought it was a fun bit of kit although you had to keep it (both channels) tuned to get the best performance, and sometimes to tilt the antenna during an SRA to keep the aircraft in the pencil beam so that you got a solid blip. Hard to imagine a controller being allowed to do that sort of thing these days but it sorted the men from the boys and the women from the girls (sorry if I'm not allowed to say that any more)! Did many 1/2 milers in my time, mostly in anger (which meant there wasn't any need to do practices in nice weather).
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