Flying from EGKR I often listen to Gatwick Traffic just out of curiosity. I often hear 170 knots to 5 DME. However sometimes when i listen i hear 160 knots to 4 DME.
You should mainly here 160 to 4 at Gatwick. Occasionally 170 to 5 is given mainly to the BA 737's as it's their approach speed preferred speed.
The reasons for it
- Tower are able to judge the time between the inbounds better when they are all at a standard speed so as to get a departure away
- maintains the gap between inbounds, usually 3 miles when no departure is needed or 5/6 when there's a departure to go
- speed for inbound aircraft is only restricted to 4 miles as each aircraft and each airline has different landing and final approach speeds
PM me if you have any further questions