ATC speed reduction rate
 

Dear all ,

When ATC ask issue you to reduce speed , what is the compliance time ?
Is there any regulation in Europe or ICAO ?
I mean is it worthing to extract speed brakes to reduce speed from 250 to 220 in level flight ( even worse , on descent ) or just let the airplane normally deccelerate should be fine ?

Judge it yourself.

If some speed control is applied 80nm from touchdown, then it's probably ok to deccelerate normally. There are so many factors to your ground speed, that it's impossible for the controller to judge your arrival time precisely at this stage anyway. But please - comply to the restriction. Many units can see your IAS with mod S downlink, so we are usually perfectly aware of your actual speed. ;)

If you are vectored for final approach in a busy airspace and told to reduce/keep the speed, then act immediately, because a prompt reaction is usually required to achieve proper spacing on final, to make a gap for a departure or to maintain separation. You will complicate controller's work if you do not slow down quickly or, which is sometimes even more disturbing - unexpectedly slow down on your own. This is usually a chain reaction - some other aircraft will have to slow down more than it was planned, or fly some extra miles because of you.

And - if you are unable to comply with any speed control, say it loud! ATC will implement an alternative solution to the situation, but we must be aware, that you will not act as you were instructed!

It seems equally true that you will complicate a pilot's work if you do not give a speed restriction in good time such that it can be met without the use of additional drag/noise required to slow down quickly. You'd not advocate driving up the tail of a traffic queue and applying the brakes sharply I suspect, just lift in good time.
Exceptions such as other traffic not behaving as instructed etc I understand, just offering the other side of the coin for that statement.

To create a reasonably predictable enviromnent, everybody must be slowed down early enough. It's OK for large airports, but at a smaller one I'm sure you would complain being reduced 250->220->etc for the only reason not to create a situation, where a tactical speed reduction later on might become necessary... :)

Well thanks for both answers. Personally I would thing that the controllers are planning ahead also , and unless there is an urgency , in wich case they will inform you ,e.g. reduce now , they would give you enough time for a decent decceleration rate , so you don't have to " ride the brakes " just to spool up the engines minutes later.

It's probably in your best interest to do it as quickly as you reasonably can, the controller will have another plan should you not slow down as quickly as he would like so don't be surprised when you are knocked left or right by 20 degrees to increase your track miles.

Reduce at the same speed as everyone else - the last thing ATC needs is everyone reducing at different rates.

(And don't slow from 180kts unilaterally, even if you are about to intercept the glide at 10dme)

Depending what you are flying will result in different speed reduction rates, where interia will be a critical factor.
So the answer in level flight will not necessarily be the same during the descent.

Part of being an ATCO is to appreciate the characteristics of the various types, and with experience know what is possible.
Dare I say "empathy" with the scenario, and presentation of the traffic.

For the pilots, comply with the instruction without delay

How fast should you slow down? Well it depends, now doesn't it? A sleepy airport at midnight- probably doesn't matter. Going into JFK at rush hour- promptly, using spoilers and flaps as necessary.