When flying online and given for example an instruction to descent to FL120 and Speed of 220, what is more important? If I can see that I will not be able to make the FL at the assigned speed, which is more important, that I make the speed or FL? I always ask for high speed clearance, but sometimes don't get it, what is done in the real world?Another question. What is the real world procedure for receivingan instruction and carrying it out. I mean if ATC tells you to turn to heading 250, should I wait to turn until I read back the instructions or turn immediately? What I'm thinking is that if I heard it wrong and started to turn left instead of right, that could be a bad thing.

As for your first question, the best thing to do is just tell the ATC that what they're asking you to do won't be possible, and they'll tell you what they want you to do from there. Typically, though, at least in the US, ATC will give you descent insturctions way in advance and say something like "descend pilot's discretion to cross xxx at 12,000 and 220 knots", leaving you and the FMC to decide how to achieve that altitude and speed.In response to your second question, I always do them about simultaneously. That is, as soon as ATC gives me the heading I dial it into the AP/FD and begin the turn, and pretty much immediately read it back. The only time I'll hold off on a turn is if I don't think I heard the heading correctly--then I'll wait until I can verify with ATC before taking a chance on turning to a wrong heading. Generally, though, the expectation among ATC is that you'll follow their vectors as soon as practical.Best Regards,Marc

Thanks Marc.

In addition to Marcs answer there is a golden rule that says "Aviate, navigate, communicate". This pretty much establishes the priorities. The most important thing is to fly the plane, i.e. don

The above has pretty much sorted it all out for you Mikkel, will just add a bit.Whenever advised by ATC to follow an instruction, do it first. Even if you cannot readback the instruction at that time due to a busy channel, the instruction is more important but also don't forget to readback that instruction, the most important thing for a controller is to know that he and the dots on his screen are on the same wavelength.

Right...thanks a lot guy's, appreciate it. :-wave

>The above has pretty much sorted it all out for you Mikkel,>will just add a bit.>>>Whenever advised by ATC to follow an instruction, do it first.>Even if you cannot readback the instruction at that time due>to a busy channel, the instruction is more important but also>don't forget to readback that instruction, the most important>thing for a controller is to know that he and the dots on his>screen are on the same wavelength.Actually, ATC can immediately see on their display equipment, if you got the meassage as in turn to a heading, since they can see your plane change direction. So as you say, fly the plane first , then tell them when you can.