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TOPIC: CRDF

CRDF 13 Mar 2018 11:19 #1

  • ColinJackson
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VHF Fixer Station - or not ?

F.G.R.I. 18015 maybe or CRDF something
(Fixed Ground Radio Instillation)

I have been reading about your VHF Fixer Stations. These were not what I was
looking for but similar.

A small square brick built unit at the end of the runway with aerial on the top.
(like the type 61a but fixed and hermetically sealed - It had acorn valve amplifiers
inside - receive only)

Inside the building was a unit with two R1392 receivers and a CRT readout. These
were all underground wired to the control tower. The unit did not transmit but
talkback would have been via a T1132 in the tower.
The system would have given a readout on the CRT to give the heading to the
runway. There were two tones involved some thing like 4.5 + 6.5 Kc/s

There was one at RAF Westonzoyland (Somerset) in the mid 1950s - It was
still intact long after the RAF had gone.

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CRDF 13 Mar 2018 17:48 #2

  • Carnaby
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The 1955 record for Weston Zoyland confirms CRDF as for many similar sites at the time (Oakington, Waterbeach, Waddington etc). 'Lesser' airfields only had VHF/DF.

A little surprised it was '...at the end of the runway'. I would have thought it would have been a hazard.

In 1968 Leeming's CRDF was HERE . (At the time this was grass, the current taxiway came much later)

The later CADF is HERE .

I note that I inspected AIR10/8867 in TNA a few years ago. UHF CADF System Theory, (AP2531P, 1963) I did not photograph any of the manual and my comment was 'Useless!' which being a techy person now surprises me.

Unsure what this is: atchistory.files.wordpress.com/2015/07/df-aerial-and-site.jpg (CADF possibly)

I also see that Leeming had GCA, PAR and ARI. What is the latter?

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Plan A is always more effective when the problem you are working on understands that Plan B will involve the use of dynamite :twisted:.
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CRDF 14 Mar 2018 06:59 #3

  • PETERTHEEATER
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Leeming was my last posting with the RAF from 1968 to 1970.

As I recall from bar talk with my fellow tradesmen ARI was Altitude Reference Indicator

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CRDF 14 Mar 2018 08:58 #4

  • ChrisTheAncient
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Was it ARI (as in alpha, romeo, india) or AR1 (as in alpha, romeo, one) the Plessey search radar that was used in conjunction with PAR to get the aircraft home?

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CRDF 14 Mar 2018 10:12 #5

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Yes - it was AR1. I've just discovered a reference in the forum:

By the late 1960s most airfields had been provided with a high powered surveillance radar known as AR1. It was located in a brick building with the revolving aerial on top of its 40ft lattice tower, which was a common sight at most airfields. This radar had a range of 70 miles and could have as many display units as one liked to install in the approach room. Because of its excellent range and 'off set' facility, this radar would often be shared by more than one station. The Approach Controller was provided with a display and was now able to see his aircraft in their controlled descents and this almost rendered the radio D/F obsolete

from: www.airfieldresearchgroup.org.uk/forum/a...raffic-control#17943

Leeming's was HERE

The reference I have also has an entry 'ACR 7C'. Leeming apparently didn't have one. The GCA was sited HERE with the PAR on the opposite side of the runway.
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Plan A is always more effective when the problem you are working on understands that Plan B will involve the use of dynamite :twisted:.

CRDF 15 Mar 2018 09:41 #6

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Interesting - that write up on AR1. But, obviously written by Plessey the way there are all those praises! But, on a more serious note, the AR1 was quite a good radar in its day. But, nearly as interesting, IIRC, there was a facility to feed a DF strobe (from CADF I presume) into an AR-1 display - though I never saw it used!

Not having been to Leeming, the layouts shown are not something I could comment on. But with a lot of the operational stations, the 'search radar' would be close to the line of the runway.

ACR-7D was just a small local rotational, and unsophisticated, radar that was sometimes used to aid landing approaches - but for slower moving aircraft at less busy airfields.

It's intriguing looking back at earlier GCA site. Just one. More usually with the old CPN-4/MPN-11 GCA convoys, there were two of those positions one for each runway and, usually nearer the end. Fun times doing a runway change to get to the other site and all up and running again!

Interesting reading that link as well. So many memories flooding back.

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CRDF 15 Mar 2018 10:26 #7

  • Sparky67
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My copy of the 1948 ‘Index to Air Publications’ lists A, FG, MG and TGRIs in the 5000 series, the last being ARI.5777, which might help date this installation? There is no Aerial Type 61A listed, the closest being Type 61, described as ‘For VHF Position Finding’ (details in AP2555G).

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CRDF 15 Mar 2018 10:33 #8

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Just found THIS thread on PPRuNe which had some more detail, possibly relevant?
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Last Edit: by Sparky67.

CRDF 15 Mar 2018 14:01 #9

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ChrisTheAncient wrote: It's intriguing looking back at earlier GCA site. Just one. More usually with the old CPN-4/MPN-11 GCA convoys, there were two of those positions one for each runway

Yes - a second GCA position is mentioned - but no data re position

For completeness the old VHF stations were:
Transmitter
Receiver

The old Middle(?) Marker has now lost its Yagi aerial goo.gl/maps/jh44smCjKdH2

Note the approach lights in front and behind. goo.gl/maps/7mSJWTJLZq72

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Plan A is always more effective when the problem you are working on understands that Plan B will involve the use of dynamite :twisted:.

CRDF 18 Mar 2018 18:08 #10

  • ColinJackson
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I apologise. It was not at the runway end at all. Going from the village of Westonzoyland
the building was over to the far right of the now main road. Not far from the old perimeter
track.

It was odd as the RAF were long gone. The site was unguarded but the equipment
in this building was still intact and the door not locked. I think the control tower was empty
at this time. Could have been 1961'ish or indeed 1957.

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