Sorry, I was having difficulty locating the report I wrote at the time. It was 15th February 1989. I erred slightly, above.
When ARW closed in 1983 the RAF were advised this removed their only 2nd line / Depth B/C facility and alternative arrangements would be necessary. (This closure was the single worst act of vandalism ever perpetrated on avionic support by the RN and ultimately cost tens of millions!!). It was wrong of me to suggest Finningley were meant to carry out 2nd line to any depth - no such capability was initiated, and the MP remained, as I said, 2nd Line at ARW despite it being closed down. Hence, the tendency to hook out the entire radar, at all front line detachments, regardless of "fault".
The report states there were 14 operational Mk3s on that day, none with radar fitted and all role limited. That sounds about right for a fleet of about 20. As it was no longer policy to know what assets any Service had, the report simply estimates "at least" 150 Light Weight Radars in service, to support 14 a/c. My 180 (above) would include those retained by the RN for apprentice training etc, plus those modified to Weather Mode variant (which the RAF paid for and modified, but then never fitted).
The main maintainer issue was how they adjusted Receiver Gain after installing a new Control Radar Set. (An internal adjustment of a pot, and a separate adjustment to the Swept Gain I mention, which was an Operator issue). Essentially, they looked for noise paint, then reduced gain until it disappeared; reducing system gain to nothing. This reflected a lack of experience on raw radars. As they had no pubs, instructions or training the procedure was passed down by word of mouth. It was completely different from that used by Fleetlands and the Design Authority, so any LRU received at 1st Line was perceived to be "wrong", when in fact it was correct. About 95% of rejections were recorded at MACE, Swanton Morley as "Low Gain" or "Poor Video"; with 99% of those determined as No Fault Found at 3rd Line. The report characterises this as a "gross waste of money".
Actions included Fleetlands delivering a properly calibrated complete radar, as opposed to individual LRUs, to be flown in a trial. This system was the subject of two Concessions by the DA as it deviated from the RRE spec to "better" meet RAF expectations and allow for the fact they had no 2nd Line capability. And the aforementioned Training/Hot Rig, to be used for both when Air Eng 22 (in Empress State) updated the Maintenance Policy. A form of Direct Exchange (common in the RAF, less so in the RN or at Fleetlands) was offered. I know the rig and the calibrated set were delivered inside 2 days, but not if the MPS was amended. Long time ago. Old age and all that.