Originally Posted by
Wensleydale
Nimrod AEW did just evolve - it was not meant to be built. .....decision to split from the NATO AEW Component was taken in the early seventies (24 E-3A at Brize or Fairford) and we decided to go it alone, everybody in the know accepted that the UK would buy 6 x E-3A as our contribution to the NAEWF.
Pretty much correct, but it did evolve and wasn't really designed as a system would be now under 'Systems Engineering' principles, driven by Requirements Engineering - which is how, to all intents and purposes the MRA4 has been designed. Actually that's also how the E-3 was designed, too.
The Nimrod decision was driven by indecision at NATO over what they wanted to do. UK decided we couldn't wait any longer because of the time it takes to develop new systems - then 10 years, now about the same or longer. When NATO did finally make its mind up, we'd gone for Nimrod so it was too late to do anything about it without massive embarrassment and cash penalties. Oh dear!
Originally Posted by
Wensleydale
.... rolled out a Comet fitted with a bulbous nose radar used to test the "Blue Circle" FMICW radar which was being developed for the (then) F2, and stated that this was the best AEW platform in the world.
Not as I understand it. The P model had little capability and was a proof of concept for the new transmitter system. The F3 radar was and is nothing like the old AEWs in power, waveform or any other reasonable characteristic.
Originally Posted by
Wensleydale
.... hence the AEW radar with absolutely no performance. Any Sqn Sh*g on day 2 of a radar course would realise that the parameters chosen for the radar would not be suitable (Low PRF, inappropriate clutter notch etc).
It wasn't a low PRF radar; it was a Medium PRF system, with range and velocity ambiguities with multiple PRFs that were used to resolve them.
High clutter levels were driven by the poor decision to use the twist cassegrain antennas - brilliant idea on paper, less so in practical use - that gave a massive height line coupled with typical N Sea ops being within LOS of land, where vehicles - valid targets to a radar - swamped the system. These were not helped, however, by the decision to go for a very low design value for the minimum velocity notch - which in fact was and would remain today extremely important, to prevent loss of valid targets as their radial velocity (R Dot) towards the AEW reduces. Remember radial vel isn't a linear relationship - it's a Sine curve. After that it comes down to computing power, and there were some issues there too.
Tracking was in fact excellent for the periods before a range/velocity hole was encountered. At least it was wholly truthful by not misleading operators into believing it was tracking something when it wasn't: when it said TQ=0, it meant it and dropped the track straight away.
After the offset parabolic antennas were fitted the height line fell massively, so range and vel ambiguities improved accordingly; but of course by then so little development had been achieved and so many tempers had frayed, the end result was all but inevitable.
I wonder if, had we spent as much on the radar development as we did on the airframes, the result would have been different. Moot point now, no point worrying about it.
What is important however is we learnt a lot of lessons that got fed into the MRA4 procurement, difficult though it has been....and with more lessons learnt I suspect.
Without a clear and unambiguous set of User and System Requirements for the AEW, the PE didn't know what to buy and the contractor didn't know what to deliver - and everyone on all sides got a bad deal. This is why it's so absolutely important to get the Requirements right at the beginning, and not leave them to chance and evolution. Hopefuilly the MRA4 will come through in the end.