Use this forum to flag up examples of red tape and gold plate
By chevvron
smokescreen wrote:The Dunsfold ILS did have an associated DME zeroed to the threshold.

Maybe the DME wasn't calibrated then, but I do know that ATC had to pass range checks because when they were re-equipping with a new radar, I suggested Farnborough vector traffic onto their ILS and thay said no it wasn't feasible and that's the reason they gave.
We actually could have done the range checks using Pease Pottage radar on which you could see aircraft on the ground at Dunsfold on secondary radar.
By highfive
The DME at Farnborough is positioned midway between the two thresholds and is 'zeroed' at the thresholds, so if you're using it for the noise abatement departure procedures, you MUST take the reading from the second 'zero' point not the first.

My understanding is that the offset is just a slight reduction to the 'standard' reply delay, thereby making an aircraft's transceiver think it's closer than it really is.

So, the zero 'point' is in fact a circle whose radius is the distance from the active threshold to the DME antenna (or whatever it has been set up for).

By the way, Cranfield can use their ILS without DME and without radar, all done by the good old stopwatch :D Maybe it is a grandfather rights thing, but I think GPS backed up by stopwatch (or vice versa) should be reasonable enough in some other cases.
By chevvron
smokescreen wrote:The CAA wouldn't allow the use of Pease Pottage (SSR only even though Pease primary was also fed in)) unless a safety case was written!

Farnborough still could have passed range checks using their own primary radar; this had good coverage to the south; one of the setting up PEs was a house on a hill in Midhurst town.
When we still had an AR1, we had a 'clip on' map overlay to do SRAs into Dunsfold and even when we switched to a Watchman, we had a calibrated centreline on our video map for 07 at Dunsfold(not for 25 though)