ATC Instruction Requirements
 

Hello All, blip driver looking for some advice here...

After some conversation with my colleagues I've been looking for answers to these questions... UK AIP, ICAO 4444, ATPL notes etc and to no avail, so thought I'd delve into the wealth of knowledge here! If anyone has any references for these queries, all the better.

1. What are the tolerances permitted, specificially in terms of speed and heading, from ATC clearences? I seem to recall +-5kts/+-M0.01 in terms of speed?

2. What is the maximum time/distance to comply with an ATC instruction? Specifically thinking of a scenario where one is given a speed reduction whilst in a descent. And linked to that...

3. Minimum rate of descent - 500ft/min I seem to recall...?

4. If cleared onto a STAR with level and speed restrictions, and one is given a direct to a fix on that STAR, do the restrictions still apply abeam those fixes?

Thanks :ok:
FFR

Wish I could help you but I'm just an aerodrome controller, I could hazard guesses but probably best left to the approach/area guys&gals. Great to see your enthusiasm though :)
If you've any aerodrome questions I'm happy to add my perspective, pm me if so

1. I wouldn't challenge a pilot for being 5 kts out, especially in a descent as the wind changes. Most modern airliners can fly a heading exactly to the degree, and should be able to

2. Speed reductions in the descent aren't the easiest thing to do especially if you've given the aircraft a level by point - in that respect I'd usually want the aircraft to make the level first and then reduce the speed. If it's the other way round, you would definitely expect to be told. For climb/descent instructions, I think there's something about 30 seconds somewhere. In the UK en-route, we get alerts if a climb hasn't started within 20 seconds.

3. Yes unless stated, although you often don't get told by A340 pilots struggling up the last couple of thousand feet using curvature of the Earth (other makes of plane are also guilty)

4. If you want someone level at a point and route them to somewhere else then the level restriction is no longer valid unless restated in the clearance. IE: be level at Point A, if you then route the aircraft direct to Point B the clearance to be level at A no longer applies unless specifically mentioned

Thanks for contributions guys, all one big team out there I guess! Had an ATCO jumpseat a few days ago and general consensus seems to be whats been posted so far :)

500ft/min was indeed an AIP thing IIRC..

FFR