The double centreline for 05/23 could be due to a shadow caused by using a 'map overlay' rather than an electronic video map, an overlay being a permanently etched transparent plate attached temporarily or permanently to the face of the display and used for SRAs. Judging by the nuts and bolts visible, this one was meant to be permanent. The airspace structure south west of Heathrow dates it as 1982 or later.
This looks like a 16" tube; we had clip-on ones at Farnborough on our old AR1 displays with 12" tubes with SRA lines for Farnborough, Odiham, Blackbushe and Dunsfold.
One pitfall you had to watch out for was making sure you had the correct range selected when using the overlay; I can remember one senior controller at Farnborough (Ken Spratt) trying to do an SRA one day. You needed to select a 7.5nm range. He sat there, looked at the tube and said 'there's no f....ing primary' until someone reached over and pointed out he had selected 75nm!
Last edited by chevvron; 13th February 2012 at 09:57.