Climbing with V/S is generally against real-life airline SOPs because it doesn't protect airspeed

Ryan, you probably know this, but I just learned it a few weeks ago - V/S reverts to LVL CHG if if gets too slow.

When you are cleared to climb to an altitude, you are cleared, and that altitude and your speed are your only ATC restrictions, unless otherwise instructed. Why should you limit the climb rate that your N1 limit /speed can grant you for setting a climb rate higher or lower than needed? What will define your climb rate will be your speed. The only case I have seen a vertical speed climb being used was on a departure at which the captain wanted to see the beautiful marina below us at dusk. For 3 minutes or so, he set vertical speed to about 300fps (so that ATC didn't think we had leveled off) and once we had left the coast behind, he went back to VNAV. For descents, V/S is much more common. Sometimes v/s is used for steady descents, and some other times it's used for passenger confort to make the transition from level flight to open descents much smoother.

The only real use of V/S for a climb is small step climbs. For instance, a number of carriers have an SOP of using V/S of 700FPM for step climbs in cruise on the 744. It makes the climb smoother for the passengers than VNAV or Level CHG for those small steps. However, it has to be carefully monitored against airspeed. JR

Did you know that flight level change should be used for the takeoff phase, not vertical speed. Martin Wilby

to be really pedantic, where it is possible, VNAV is the preferred mode rather than Level CHG these days.

if you have realistic A/P engagement on then to engage the A/P you need to have the aircraft trimmed (or close to trimmed) and have less than a certain amount of force being applied to the yoke. If you push the yoke too far with A/P on the A/P will diengage I believe.

Thanks everybody's help! If I engage the ALT HOLD, and If I engage the V/S AFTER THAT climbing with V/S is working.Another thing: after I took off, sometimes I can engage the A/P, sometimes I cannot... Why? It depends of the altitude..? please help.

You have to sign your full name to every post use this forum, those are forum rules. That said, you have to learn to fly the plane it was meant to be flown. A/P can be engaged above 400 feet but... only if the aircraft is correctly configured and correctly trimmed. You will need to read the manuals (or at least follow the tutorial) to work out how it should be configured.

to be really pedantic, where it is possible, VNAV is the preferred mode rather than Level CHG these days

. I may be wrong, but I recall Ryan saying in the 737 800, it's level change only, armed before take off, VNAV after. Sorry if I misread. Martin Wilby

PMDG! Here are the screenshots: Here I am taking off: http://imageshack.us...s/827/ngx1.png/I've just taken off. I enabled the A/T and the speed and the flight director: http://imageshack.us...es/69/ngx2.png/Here you can see I activated the V/S: http://imageshack.us.../828/ngx3a.png/Here it is same (zoomed out): http://imageshack.us.../832/ngx3b.png/Now I selected the CMD A autopilot: http://imageshack.us.../812/ngx4a.png/Here it is again, zoomed out for easier to see: http://imageshack.us.../835/ngx4b.png/ Please help me, I hope I could give you enough information by the photos to find that I did wrong.

Well I can see for a start CWS is indicated on the PFD, I'm sure this is preventing the AP from working as you hope. The aircraft mustn't be correctly trimmed Chris Ibbotson