Not a self appointed expert but I would assume if your airline was that worried about it, each flight segment will have an assigned cost index to follow, playing with selected speed and V/S is changing the CI, having said that, pilots seem to enjoy manipulating the climb and descent to suit their needs, for instance, our base is close to an FIR boundary, we try to help the controllers by reaching our cruise level prior to that boundary, relieving the need for coordination with the next region. Another way to answer your question is by simply inputing your CFP data for that length of flight, now, whatever CI you used, now change it to "0", now compare the burn on the INIT page for your answer. Remember, operating cost is much more complicated than saving fuel.

Dream Land. For a given set of parameters CI, weight, temp............etc. Open climb will give you best ROC







What do I know. I only work here:ok:

Maybe your definition for Vy is different from mine, please explain what CI has to do with best rate of climb.: :eek:

Only with putting CI of zero during climb, this will give you the best rate of climb speed Vy.

loc 22550 is right. Let's simplify it all:
Open Clb: Give me climb thrust and maintain the speed (selected or managed) with the elevators.
Clb: As above but please obey any constraints.
Exp Clb: As for 'Open Clb' but fly Grn Dot speed. (ie max gradient).
CI 0 gives max rate of climb
Cheers
mcdhu

Thank you mcdu and loc 22550. :D

I think you lot need to go back into the books!...

you don't give me much confidence!...

are you really A320 drivers?

well put mcdhu.

dream land three posts back you asked what CI 0 has to do with Vy. what's with all the applause. Make up your mind.

Hiya sharpshooter.

"Pulling" speed may be the quickest way to get to a cleared FL but it is not neccesarily the most efficient. The 'bus (specially the 321) has a tendency to lag a little at the higher FL. Ie ROC = <400fpm, if one is particularly heavy. One course of action is to go selected speed and reduce speed by 5 kts or so, Causing a kind of mini zoom climb, this is quite useful if you only have maybe 2000ft to go.
My company sops explicitly forbid use of VS at all above a certain flight level as the Aircraft will disregard speed to get its desired ROC, possibly leading to alpha prot etc.....
With regards to your post, leaving the aircraft in managed speed for the entire duration of flight is more efficient, however it is very rare that one will be able to do this as ATC constraints, etc exist on nearly every route I have ever flown!:)
Tacho

Tacho

Shouldn't get to Alpha Prot. If a too high V/S is selected, the speed reduces, but when it gets to VLS the Autopilot ignores the V/S command and will maintain VLS. The FMA will still show the demanded V/S.


This though does mean that you are climbing to altitude with the speed way back on the drag curve. Not a good place to be - see the Pinnacle Airlines CRJ stall, double engine failure crash as a perfect example

Be careful out there!

T'bug :ok:

taperlok, your original partially incorrect statement that indicated that when OPEN CLB was selected, you get Vy, I challenged that statement since I knew that every time you change CI, managed speed will change, do you get it now?
mcdu and loc22550 corrected your statement, not sure if you understand that though. :hmm:

Yes, this is called a reversion, no chance of a tail slide either. :}

oops, wrong term, doh! right sentiment. thanks! :ok: Basic point I was trying to make was that it will neglect the speed for the sake of ROC.

cheers.
Tacho

in reply to the original post
 

situation: normal flt/no wx/no atc input/no reason really, to select v/s or lower speed.
except the pilots perception that by doing so one would reach CRZ level faster and thereby enjoy the tail wind for a longer period of time.
lets assume that you are able to select a higher v/s or lower speed at the earliest,say 5000'. assume CRZ LVL 390. normal climb time average (without touching FCU) ~ 20min.
In flying selected speed or v/s, say we get there in 18 min.(IMHO Pffsss)
you end up flying at least 1 extra min of CRZ and have in net total managed to completely muck up the airspace that you climbed through.and spend another minute longer in CLB thrust to attain CRZ speed
If your CRZ LVL is lower and if you only do it from FL100 then, we are dealing in seconds.
these are entirely my take on the situation.
your call

Thank you gentlemen, your inputs have been most helpful. Cheers

Seen the tail slide 2x, once when I new on the aircraft and the othe pilot was showing his technique to go up quickly, and once while in the jump seat giving a line check...both were on a heavy aircraft ..definitly not in the video arcarde. Also, departure out of Gatwick...knows what altitude you have set in the FCU

Mate, a tail slide is what you do in your car, this is a pilot forum. :}

The aircraft stopped climbing, (did not stall), and was losing altitude with the nose high. Sorry that I referred to an improper term...probably the difference between bonnet and hood. :)

Roger, understood! :ok:

Iceman,

I've never heard of the FCU selections being transmitted to ATC (presumably by the transponder). Where did you get this information? Indeed perhaps it IS transmitted but I cannot find any reference to it in the manuals.

Anyone from the engineering side care to comment? Could this be another of Airbus' "little foible" that they choose not to tell us mere drivers about?