Woodpecker -
I am sure 120.4 will come up with a definitive answer (I am just a TMA area controller). It depends what you call affecting safety. As an Area controller, I am allowed to use 3 miles separation in the LTMA instead of the usual 5 miles, because of congestion. The heathrow directors are allowed to take that down to 2.5 miles within certain criteria.
That 2.5 miles is an absolute minimum. If 120.4 breaks that because someone is not flying as they have been instructed,
he will be suspended.
This will cause more delays as we are tightly manned as it is. When busy and all positions are open, we cannot afford to lose one ATCO, otherwise we start running out of the legal time we can work between breaks.
The 2.5 miles is because Heathrow is such a busy airport. If airlines want it pushed up to 3 mile spacing so that they can have a plus or minus 25kt leeway on speeds, then this will mean that AC will always hold for more than 10 minutes in all but the queitest or times. I do not think the airline bosses will be happy with that.
Parallel landings are used, first thing in the morning, to ensure that delays are not allowed to build (if we start off with holding at 0630, it can take several
hours to catch up - the airport is running at such a high capacity)
Using parallel runways during the day as a standard way of operating, would not work with ground movements and departures thrown into the mix. I am sure 120.4 would be able to elaborate a little more on that one.
What I am getting from this thread, more than anything else, is that 120.4 would like to be told if you cannot comply with the speed instruction, for whatever reason (slippery A/C, company SOPs). If he does not get told, then how can he adjust the guy behind or ahead to maintain the separation?? Heathrow controllers are not Gods (though some like to think it
), they cannot know what you are going to do by reading your mind.
If their is a specific company policy regarding certain A/C, then let ATC know at OPs level. Once known it is fairly easily adjusted for, in the same way that heavys/mediums/lights need different spacing.