A320/321 Max Rate of Climb Speeds

[An Paddy Eile]

Hello!

Can anyone tell me how to calculate the best rate of climb speeds for the 320/321?? I am aware that entering a cost idex of "0" will give you a managed target climb speed which will privde maximum rate, but is there any rule of thumb (such as VLS + X, or Green Dot + Y) to work it out in advance??

Cheers!!

APE

[An Paddy Eile]

I think what you are referring to is the best angle of climb speed. Green Dot is the minimum drag speed and will therefore give you the best angle. What I am after is the best rate. For an average 320/321 at mid altitudes and average weights it should be in the region of 275 Knots or so.

If you were only at Green Dot at FL 300, you would be using quite a bit less than maximum thrust. In the event of an RA you would have to apply TOGA and maintain VLS as a minimum. But, yes, you would be unlikely to achieve 1500 FPM for any decent length of time.

[TE RANGI]

Green Dot would give you the best Lift/Drag ratio, hence the best angle of climb (or holding speed).

For want of anything better and for practical purposes I use Econ Climb Speed at Cost Index 0. This was Boeing logic (I know, Boeing) but laws of physics are universal and the FMC/FMGC are the same make.

I have read somewhere in one of the Airbus FCTM versions that you can use Turbulence penetration speed to get the best rate.

And another consideration would be whether you refer to a static (constant speed) vs a dynamic maneouver (such as on an RA) where you'd get the best rate by trading speed energy for climb rate.

My two cents.

[An Paddy Eile]

Thanks TE RANGI!

I agree that the speed/altitude trade is obviously the best for short term situations. It's the long term one that I'm interested in.

Very interesting about the FCTM mentioning the use of turbulence speeds for best rate. I'll start diggin throught the version I have to see if I can find anything.

Thanks!

[mcdhu]

From Airbus ''Getting to grips with Aircraft Performance'' 2.2.4:

'To minimize overall fuel consumption during flight, a low CI must be used. As the climb phase is fuel consuming, it is advantageous to minmize climb duration. This is achieved at the maximum rate climb speed. CI 0 gives IASecon which is Max Rate Climb Speed.'

It seems to work out most times about 270KIAS in the A319.

For the above publication, Google 'Wing Files'

Cheers all,
mcdhu

[An Paddy Eile]

Thanks mcdhu!

Anyone have any rules of thumb out there???

[mcdhu]

Yup, found it. FCTM 2.060 P3 of 5: ''The speed to achieve max rate ...........lies between ECON climb speed and green dot. As there is no indication of this speed on the PFD, a good rule of thumb is to use turb speed to achieve max rate.'

Cheers,
mcdhu

[An Paddy Eile]

Excellent! Thanks mcdhu!

[kuwait340]

i have this info written on a document that i have collected from the internet...and it says (max r.o.c speed for the A320 is 250kts/0.65mn)..

this is not official info.