WOK
I am the project manager for the system being put in at Heathrow that is causing this change.
We may need to check the wording of the instruction to make sure it is clear.
Just some background information in case anyone is interested. The new system uses multilateration
to calculate the position of aircraft from their Mode S transmissions. It consists of 15 receivers
around the airport feeding data back to the control tower. The positional information will be displayed as
part of the ASMGCS (SMR to you and me) displays in the VCR.
One of the features of Mode S transponders is that they transmit a squitter message once per second,
containing the Mode S address (which is fixed and unique to each aircraft). This happens even when the
aircraft is on the ground, as long as the txpdr is not switched off or to standby, and it is this signal that we
use to calculate positions. Note that for all aircraft with weight-on-wheels switches, the Mode A/C txpdr is
disabled when on the ground (assuming it has been set up correctly). Therefore, leaving your transponder
on should not cause clutter on radar displays.
As for your Mode A code, you should squawk your allocated code when taxiing. We only want you to use 0000
(or 2000) when you reach the stand. By the way, 0000 is a general use code for local allocation. As I say, we
need to check our wording , because if you squawk 0000 whilst taxiing we can't display your callsign.
Finally, this type of system is currectly being installed at at least 5 European airports (Frankfurt, Zurich, Schiphol,
Brussels, Paris CDG), and eventually up to 60 US airports. Therefore the procedures for Heathrow will become
widespread.
Graeme Henderson
Last edited by GTH; 1st May 2002 at 21:48.