Hi! I’ve always been wondering this case, for example, during approach at a busy airspace. When the controller instructs you ‘do not exceed 220 knots’ and you are currently doing 260 knots, how much time do you have to comply before you are given a violation and/or report? Similarly, what about when you are instructed to descend to a certain altitude (normal and expedite).
If you are flying a larger aircraft ie. A380, descending quickly would be impossible to lower the speed to the request… I always panic by lowering the landing gear lol, which should not be done at 10000 ft 😂.
Hello! For speed, you can start to slow down early if it’s an issue, should really only take a minute or two but if you need more time you can reply with unable I believe. As for the altitude change, us controllers take into account aircraft type. Proper vertical speed for decent I do is usually between -1000 and -3000 vertical speed. It gets the job done quick, and is what’s done irl. Hope this helped!
Most speed commands are mostly proactively used-you should start to decelerate immediately but there’s no need to deploy the gear or flaps full, unless your speed is not slowing at all.
For altitude, unless there is a please expedite, you are mostly free to descend at a rate you can work with-about 1000-1600 f/pm should work just fine.
While there isn’t a strict “time limit” outlined for every command, pilots are generally expected to follow instructions as soon as possible, typically within 10-15 seconds of receiving a command.
Note: If a pilot doesn’t comply within a reasonable time frame or seems to be ignoring ATC instructions, a warning or ghosting may be issued, depending on the severity of the infraction.
As others have said, begin reducing speed, descent, etc. within a reasonable amount of time.
When flying aircraft that are heavy & slippery, you may want to slow a bit earlier by gradually reducing airspeed in 10 kt increments as you near 10,000.
Do not panic - don’t drop your gear or do anything unnecessary. If you’re in a descent, you may need to temporarily decrease your descent rate and deploy spoilers to slow. Once you slow, you can adjust descent rate based on time/distance.
It’s good practice to be aware of your surroundings and sequence, or aircraft you are following. If the aircraft you’re following slows, you may want to slow if your lateral separation is 5nm (or less). If there is plenty of distance, maintain your speed until ATC slows you, or until you close the gap.
If you’re unsure about your sequence, use your best judgment and follow all ATC instruction.