Danny gets back to work again.
The Course ended; we were now deemed fit to take up our (Subsidiary) duties as Fire Officers on our various Stations (no extra pay, though). However SATCO, justifiably aggrieved by losing me for two weeks before I'd even started, demanded that I put Fire Officer on the back burner for a while, reasonably pointing out that that Section seemed to run well enough in the hands of our very capable Sergeant. It had managed quite well without me so far and could do so a bit longer. In fact, he mused, it didn't seem to matter much whether there was an officer there or not (this is uncomfortably near the truth, as in many other Sections).
Examining my F 5994 closely with a magnifying glass, it appears that on 22.12.62., a S/Ldr Anderson, (LEO) turned me loose in Tower, Approach and Radar, so he would certainly have been SATCO (but I haven't the faintest recollection of the man). I think two of the Controllers were Lieutenants RN; chatting to one, I was surprised to hear that he was, effectively, only on a "ground tour" from the Seaman Branch and would be going back to sea duties at the end of it.
"So", I said, "when we hear of 'Ark Royal' going aground ?" .... "Again ?", he said (alluding to an unfortunate incident in Plymouth Sound the previous January).
IIRC, there was nothing out of the ordinary in Tower or Approach (usual CR or CA/DF), or in the local procedures, to frighten the horses. But the Radar was a weird beast of a kind that I'd never seen before, and only vaguely heard about. This was the ACR7C, which I believe I've written about before some time ago, but no matter as the tale is worth retelling.
This came to us in two guises: the 7C (Cossor), which was the mobile version, and the 7D (Decca), which was a fixed installation with the console in the Tower (like the later AR1). Ours was the mobile one, IIRC it was sited somewhere in the "cocked hat" in the middle of the three wartime runways. (I think we only used two of these, Wiki gives 03/21 (2,000 yd) and 10/28 (1400 yd). Placed where it was, it could cover all approaches. (p.262 #5234 has a full description and pictures).
Obviously it had to be mounted in some sort of vehicle. Wiki shows a Commer "Cob" with a 7C on the back, but somehow I can't remember a prime mover at all. I think the console (one 12-in PPI tube) was with its operator in something about the size of a rest caravan. [See Posts #5233 #5234 p.262]
There were no other vehicles, just an external diesel generator to power the radar, and a 40-gallon drum of derv - and I'm quite sure about that as it figures later in my tale.
Of course the ACR7 had no Glide Path, it wasn't a Precision Radar, just a PPI runway approach aid. But these are not to be sneezed at. Both MPN-11/CPN-4 and MPN-1 can be used in this mode, although a PPI approach in the MPN-1 would have to be done from one of the Director positions, as talkdown has no search radar console, only a precision centreline and the "Errormeter", which was operated by the Tracker. I never did one on the MPN-1 (not necessary as it could move round to cover both approaches to the [Strubby] main runway), nor on CPN-4, but at least one on AR-1 (and that was under strange circumstances indeed).
ACR7 had originally been designed for the entirely different purpose of marine estuary control. And as all vessels afloat within 20 miles are more or less on the same plane (pace Union Jack, but even 100 ft between wave crest and trough does not subtend much at 10 miles), they were quite content with a very shallow radar lobe. The PPI only had a range of 20 miles, IIRC, but we never had to do any searching as all our customers were handed to us on a plate by Approach.
Aircraft, on the other hand, have the awkward property of going up and down, so as to square this circle and modify the kit for RAF use, they mounted their aerial so that the mid point of the lobe could be raised from ground level to something like 10º above horizontal, IIRC in about seven stages. So when someone was coming in on a QGH, you were monitoring Approach, knew the height and had a rough idea of his range in the turn. In the hut you had a graph from which you could read off the best elevation "stud" to use - but after the first dozen runs you could guess with fair accuracy on which one of these your man would show best.
In my next Post, I do not need to describe our PPI "Talkdowns" (for those who fancy they have heard the tale before are quite right - below is an edited copy of my Post to ACW418 last July (p.198 #3954 - or it was that serial number yesterday).
"You are of course right - you were in the hot seat, and you know ! IIRC, we used two methods, the "Continous Descent" (with a height check every mile), and the "Step Down". This involved only two (?) steps down, from 1500 ft at 5 miles, to 900 ft; he would hold you at that height till you reached 3 miles, then tell you to descend to whatever MAA was in force. Or something like that, but memory fades. I can well imagine that the first method would be just as hard work for the pilot as hugging a glidepath in GCA, but would have thought the second needed much less brainwork (and was just as safe).
The PPI was impressive. Of course it was a very narrow lobe radar, so you could be really accurate. It was the only gear wth which I've been able to see the runway lights ! And I still recall the sharp-cut little square blip. The story was that it was first designed as an estuary radar, and of course all ships are (for practical purposes) in the same plane. The same thing went into towers as the ACR7D (Teesside Airport had one), but the 7C was a truck".
As I can recall no particular triumphs or disasters directly attributable to my tenure in the ACR7C, I will next time launch out instead onto my Subsidiary career as a Fire Officer.
Goodnight, all.
Danny42C.
The bad workman always blames his tools
Last edited by Danny42C; 4th Mar 2014 at 23:26.
Reason: Spacing.