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L4645 ‘Fire Alarms’ by Chen

Posted by Encota on 28 Feb 2021

LWO co-blogger Chalicea (Shirley Curran) and I had been musing over creating a joint Listener for several years.  So we were delighted to see ‘Fire Alarms’ finally in print!

As is often the case with thematic crosswords, at least for me, much of the total time is spent choosing a theme.  In my view the ideal themes are those where what has to be adjusted in the puzzle or its endgame has significant thematic relevance.  I had been thinking about some possibilities – perhaps just after a visit to a nearby decommissioned Suffolk airbase, just inland from Bawdsey Manor where much of the WW2 work was done on radar, where friends are working on restoring some interesting aircraft (but that’s another story) – and the idea of deploying CHAFF as part of an endgame to protect military aircraft from detection by enemy radar was born.

So what, in this context, is CHAFF?  In more recent times much use is made of the term ’stealth aircraft’.  In the design of these, much is done to reduce the amount of radar waves reflected from the aircraft back to enemy radar receivers, so making them less detectable.  Surfaces at ‘odd’ angles, energy absorbing layers and more are used to minimise the amount of wave energy returned to the radar.  Now imagine trying to do the opposite – to maximise the power reflected back.  Ignoring why for a moment, what might you do?  Some answers include using a substance that conducts electricity well and making items of a length that maximises reflections – typically half of the wavelength of the signal used by the radar.  In its simplest form CHAFF is huge numbers of such strips deployed from a moving aircraft, so that any radar trying to detect those aircraft gets many more reflections from those strips than from the aircraft themselves, so making the aircraft far harder to spot – i.e. the difficulty of separating the wheat (the aircraft) from the CHAFF (the… umm … chaff).  Of course those reflections are from places in the sky where there aren’t aircraft, so giving the aircraft themselves significant protection.

Now who might I approach to co-author a puzzle about CHAFF, invented by a certain Joan Curran?  Let me think for a moment …

… so, one moment later, I proposed the idea to her daughter-in-law and off we flew.

Representing short metal Aluminium strips as AL (fully capitalised here to avoid confusion with Is) gave us much scope to design clues with words with and without ALs in them.  It seemed fun to design clues where the definition gave the answer and the wordplay the letters without those ALs, such as in 14d’s Stale beer (7, two words). Here the wordplay ‘Stale’ encouraged the solver to PEE (oh dear.  BRB2), whereas the beer was P[AL]E [AL]E (which had much the same effect).

Our logic for the thematic part went as follows: 1) Initially the four famous WW2 bombers, the Handley Page HALIFAX, the Avro LANCASTER, the Short STIRLING and the Vickers WELLINGTON are made clearly visible by the reflected radar waves, highlighting them in the sky. 2) Then they deploy CHAFF and suddenly lots of small AL(uminium) strips are floating about in the air.  These are then equally highlighted by the radar’s waves, resulting in a very confused final image for the radar operator.

In summary, four loaded bombers traversed the grid and, using ECHO of RADAR WAVES were highly visible. Solvers were informed that CHAFF was DEPLOYED (the Al – aluminium – strips that confused enemy radar) and were instructed to SHADE ADDED AL GREY. With the four aircraft and the 14 examples of AL in the grid, this required the shading of 55 letters (grey, for the convenience of solvers, though silver in reality).

At one stage we considered asking solvers to highlight every AL in the grid, whether reversed or diagonally placed, or…  However, this ended up a bit too confused even for us.  I did also quietly propose that we use ICANN, the Internet naming and numbering corporation in place of ICENI in the endgame to allow CURRAN to appear in the final grid but I was overruled by the modesty of (Joan’s son) Charles and Shirley. 

We worked as a real team on this and it was a delight – co-developing and refining the grid, with Shirley demonstrating, as ever, her superb skills in this area, plus jointly working on the clues.  We used a shared online spreadsheet (if you are thinking of co-creation of a puzzle and haven’t tried it then I can’t recommend this highly enough) for the clue development, keeping track of changes etc.  An excellent setter helped us with a test-solve and we were ready to submit.

A fabulous feat of engineering which can’t get enough ‘airplay’, in my mind.  If you are interested in reading more then you may find this link interesting: https://www.smithsonianmag.com/innovation/woman-whose-invention-helped-win-warand-still-baffles-weathermen-180970900/

Cheers,
Tim / Encota

One Response to “L4645 ‘Fire Alarms’ by Chen”

  1. Alan B said

    Naturally, I didn’t know Chen’s identity – I just thought a new setter had turned up. Congratulations to both for a very well-constructed puzzle with a substantial theme that revealed itself bit by bit. It made for a rewarding finish. I was familiar with the name of the aircraft, but I knew virtually nothing about the parts of the theme to do with radar waves and aluminium strips. I read more about that than i needed for the crossword – it was an education.

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