flame_bringer

the question might seem vague and silly but i'll try to clear it.
so in the lateral modes you push the ( HDG/TRK ) knob to choose NAV mode which if chosen guids the aircraft along the flight plane and hence we switch from selected ( when the knob is pulled ) to managed lateral modes and the track and heading screen on the FCU shows dashs .
however .. i dont get it how do you switch to managed vertical modes ( which guide the airplane along the vertical profile automatically )and all the other managed modes such eg RWY,RWY TRK...etc .
all i know that there is a knob on the FCU called ALT knob which if pulled engages open climb or open descend and if pushed engages climb or descend mode and they're all selected modes .
and the FPA,V/S knob which if pushed would level off the aircraft immedietly and when turned and pulled would choose a certain V/S or FPA.( depending on the selection of the FPA,TRK,HDG,V/S push button )
there isnt really a managed vertical control ( automatic control along the vertical profile ) for the aircraft considering this they're all selected :S
so how do you engage the managed vertical modes ?
thanks in advance

jb5000

Very quick reply:

If you push the altitude knob you get Climb (CLB) or Descent (DES) modes. These are the managed modes (Open Climb/Descent being the selected modes), and will follow any altitude constraints programmed into the FMC. For this to work, of course, you need to be in 'NAV'.

The RWY mode comes up on takeoff, when you set takeoff power, if there is an associated localiser emitting for that runway. It gives you lateral steering guidance which can be helpful in LVPs.

If you have to fly a heading after departure, you preset this on the FCU on the ground. This gets rid of the 'NAV' in blue on the FMA. Once airborne instead of 'NAV' engaging 'RWY TRK' engages, guiding you along the extended centerline until you decide to pull heading.

Hope that is of help.

flame_bringer

hey thanks for the response
but whats confusing me is :
it says in the maintanence manual if you turn alt knob when pushed climb mode or descent mode engage and it will follow the selected altitude while taking into account the altitude constraints untill it synchronizes with the actual altitude then the aircraft levels off while
if you turn it when pulled the same happens except that it disregards the altitude constraints
so basically climb mode and descend mode are selected because u turn the knob while pushed and it follows the selected altitude and the only difference between it and the open climb or open descend is that the latter one ignores the altitude constraints
its really confusing
arent u supposed to have dashes displayed on the FCU if its managed ?

jb5000

I believe you've got the general understanding...

Turn the altitude knob and 'Pull' will give you either climb / idle thrust as appropriate and the aircraft will ignore all constraints.

Turn the altitude knob and 'Push' will give you a climb / descent along the profile calculated in the FMC, which includes any constraints you have programmed.

The 'dashes' on the FCU will never appear in the altitude window, because despite following the profile you still have to give it a hard height to climb or descend to. There is a circle that appears next to the number on the FCU which indicates whether the active mode is managed or selected.

flame_bringer

that means the aircraft is not controlled automaticly in the vertical profile by the FMC you still have to turn the knob to control it , which contradicts with the term ( managed ) because as far as i know in the managed mode the pilot doesnt touch anything everything is done by the FMC .
thats so confusing

jb5000

It's quite straightforward, really, I guess it's my dodgy explanation.

E.g.

You want to fly a SID with various 'at or below' constraints along various waypoints. Your initial clearance is to climb to FL120, whilst respecting the constraints.

You set FL120 in the FCU window, and CLB mode will engage automatically at acceleration altitude.

In Climb mode, the aircraft will level off at all of the preprogrammed constraints in the SID. It will then climb again to the next constraint, and the next, all the way up to FL120 which is what is set in the FCU window.

If at any point you are recleared 'unrestricted' up to FL200, you turn the FCU knob to FL200 and pull it. Open Climb will ignore all constraints in the FMGC and climb you up to FL200.

Exactly the same principle applies in the descent!

flame_bringer

thanks for trying to help and im kinda understanding it now ,one more question though:
what do you mean by being recleared or unrestricted ?you mean the SID does not obligate the pilot to take the contsraints into account ?

AirwayBlocker

Also while in the managed descent mode the aircraft has a 20 knot margin either side of the planned descent speed. The descent is planned at thrust idle. If it gets high on the profile it will increase the speed (and descent rate) to regain the profile. If it reaches the upper margin and is still too high you will get a message asking you to extend the speed brake. If it gets low on the profile it reduces the speed (and descent rate) to maintain the profile. If the speed reduces to the lower margin and the aircraft is still too low on the profile it will add thrust automatically.

Descent in the open descent mode will reduce the thrust to idle and the planned speed will be maintained with no margins either side. The aircraft could then end up either high or low on the profile. While you are still able to determine whether you are high or low, the aircraft will not automatically fix it.

tangodownNZ

flyboyike

What's confusing you is that the 320 will not START it's own managed descent, but it will CONTINUE it on its own. That is to say, you do have to push the ALT knob for things to start happening. This is different from Boeing, EMBRAER (and others) that will actually start their own VNAV descent without pilot intervention, provided said descent is programmed properly.