Review of GCA History Link.
Molemot (#4011 p.201 link)
Thank you for the graceful compliment, which I accept on behalf of all past and present "Talkdowns".
I have been going through the link you so kindly gave me with increasing wonder (the level of responsibility that the RAF and RCAF were happy to place on the shoulders of airmen in those early times !!) and admiration at their complete and well-written account of the genesis and first days of the AN-MPN-1 GCA. We still don't know whether it came into operational use in Europe before close of play in May '45. It certainly didn't get out to the Far East. No matter now.
It occurs to me that others (I sincerely hope) may be studying this jewel of a link, and may think that the description of the operation of the equipment also holds good for post-war RAF practice. There were considerable differences (the main ones which I list below, point by point).
But I am very glad that this has appeared, for it relieves me of having to tell the whole weary tale ab initio in a Post (already on the stocks, to appear soon) and will allow me to concentrate on minutiae which (I think) had a terrible consequence.
First, the technical detail they give is first-rate ( I've learned a lot that I didn't know, and I worked the gear for two years). You can take it as read.
(Quotes from Link in italic, RAF operating practice in plain text)
Prime Mover
========
The O-853 AEC Matador 8-ton was the prime mover used by the RAF. Ours carried a Lister diesel driving the generator (nice pic on Wiki).
Placement on the airfield
================
The truck was placed approximately 100 ft to the right of the runway in use and near the windward end.
IIRC, the RAF required a further 75yds from the edge of a runway to be kept free from all obstructions, so our truck would be at least at that distance.
Therefore the trailer was tilted two degrees below the level.
We tilted ours four degrees (the truck was then termed to be "on tilt").
radar reflectors placed a fixed distance from the end of the runway, and from the centreline of the runway.
These would be our "touchdown" and "offset" markers.
Operation of the Truck
==============
The standard crew was made up of four operators, one Controller, one Radar/Radio mechanic and one motor mechanic/driver for the prime mover and power units. I recall that, if available a second Controller would take over one of the PPI operating positions.
The RAF Crew comprised one Controller ("Talkdown") and one "Tracker" (each operated one of the two precision radars). The one Radar Director operated one PPI tube (the other was disused, as the CR/DF operator in Approach took over its function). There was never a second Controller.
"Talkdown" always drove the prime mover (then he had no one to blame but himself if the rig ended up out of position !) We always seemed to have two or three Radio and Radar Fitters/Mechs on site.
The operators normally manned the two PPI positions, the horizontal precision CRT and the Vertical Precision CRT.
(See above)
the selected aircraft was handed over to the second operator to vector into the landing pattern.
We needed only one PPI operator, the "Feed" Director, who did this.
By using cursors to intersect the radar blips, Height and Azimuth information was fed to the Controller who normally stood between and behind the two precision operators so that he could monitor the height and azimuth information with relationship to the pre-planned glide/approach.
This I would like to have seen. It must have been rather like the circus trick where a rider rides standing on two horses. Our "Talkdown" sat at the azimuth precision display, his "Tracker" at the elevation one beside him (how was that coordinated ? - wait and see).
At two miles from touchdown the precision operators would switch to a Two-mile range on their CRT which would enable them to get more accurate positional information.
This puzzles me. I do not remember any two-mile "zoom" facility. What we were able to do was to speed-up the precision scan rate (for the last mile of talkdown) from 1 to 4 sweeps per second. Do they mean this, perhaps ?
With the Link, and these Amendments, you really have a good introduction to the "Stephenson's Rocket" of GCAs, and it makes my task that much easier.....D.
Geriaviator,
Be my guest in mine ! Welcome back !......D.
Wander00,
Very tactful ! Yet his Dad (probably) was only doing his job to the best of his ability, same as we were. It was just his fate to be on the wrong side. Alles vorbei now, anyway ! Yes, good blokes all.....D.
Bit of a long story, I fear,
Cheers to all, Danny.
Last edited by Danny42C; 17th Jul 2013 at 23:13.
Reason: Spelling error.