Hi, I would be grateful to get clarification about one matter.

On 'descent' page there is speed restriction 250/10000.

There is also a place for another - pilot input restriction, so i put 200/5000.

Problem is that plane does not follow my restriction, even LNAV/VNAV were engaged all the time during descent.

Do i understand or do something wrong here ?

You may have to speed intervene. Heavy a/c don't always follow restrictions, you may need to take control from the automation and apply speedbrake also. Check out Kyle's videos they're excellent.

Problem is that plane does not follow my restriction, even LNAV/VNAV were engaged all the time during descent.

 

Hi,

 

Do you mean the aircraft doesn't attempt or doesn't succeed in following the restrictions?

For the 250/10000 - which I think is rather 240/10000 by the way - for instance, does the magenta speed bug change to 240kt before 10000? (Usually around 11000ft or so but it may change anywhere in the last thousands feet before that depending on the calculated descent path).

If the speed target changes, but the aircraft doesn't slow down enough by herself to match it, then yes you have to intervene (speed brakes, switch to V/S and reduce rate of descent, switch to FLCH, or even level off, whatever you seem better in the particular case).

If the speed bug doesn't change, then something prevents the FD from commanding the speed reduction and then you will have to investigate why.

I have never seen that later case in the sim, it may not be able to slow down to 240 on time by 10000ft depending on the wind mainly but it always commands the change of speed provided you leave the spd box blank and don't use speed intervene before.

Sure, if you use speed intervene earlier to set a higher speed, then the FD won't command the speed reduction automatically.

Plane descend and slow down to compulsory 250 nicely, then when I passed 5000 ft I expect that magenta pointer will move to 200 and plane will try ( with or without additional drag ) to slow down to 200, but that did not happen.

Ok, have you checked that you don't have some speed restrictions in the leg page higher than the 5000/200?

I'm not sure about how are prioritized the restrictions by the FMS and I'm not home to check that now but I will do later on.

Interesting, I've not used that feature and had to review the FCOM (see pg 11.43.5), which implies that the speed will become the magenta FMC speed.  Agree with Romain, check the restrictions on the LEGS pages which I'm sure will take higher priority.  Also, keep an eye on your FMA to see what pitch mode is active.