View Full Version : A320 Cost Index
Hi,
Does anyone have any further information regarding the cost index on the A320 family?
I have read the FCOM and the Airbus getting to grips with cost index...
But specifically, a table of a given cost index vs the target mach number, and how much % wise the aircraft can "drift" from this target due to wind?
Just to further my own knowledge!
Thanks in advance!
Microburst2002
11th Feb 2013, 04:51
There are tables, "somewhere" in the fcoms, for various CIs and winds and weights.
Slasher
11th Feb 2013, 11:40
Question for you Micro while we're at it (if you don't mind) -
Changing CI from 18 to 0 in CRZ results in a slightly higher REC MAX but
can you tell me if the margin is reduced or not? I get the impression it is.
On the Prog page with 18 - 350 350 363 / with 0 - 350 355 369
Looked up the speeds in FCOM and I calculate from 363 to 369 the margin
reduces by 2 knots.
Assuming I'm correct - why would the buffer reduce for the same GW?
Canuckbirdstrike
11th Feb 2013, 16:12
The buffer is G related. It is 1.3g and it does not change with CI choices. To put perspective on this a 30 degree bank turn is 1.15G and light turbulence is 1.05 to 1.1G.
Slasher
11th Feb 2013, 18:31
It is 1.3g and it does not change with CI choices.
Well that's what I've always thought. Look up the speeds for 1G stalls clean.
Got the data! I forgot the PEP had it in the enroute planning tab
john_tullamarine
12th Feb 2013, 00:19
Prefer not to close threads unless you have a specific reason to do so. Others may find the commentary useful.
Microburst2002
12th Feb 2013, 04:20
buffet limit is not CI related
The REC MAX gives a .2 g margin, I think.
I can't see why it changes with CI
Slasher
12th Feb 2013, 04:47
.2G buffer translated into a speed margin in the 1.0G case Micro.
I can't see why it would change with a reduction of CI either.
Never mind. I'm hardly ever up that high anyway.
capt. solipsist
12th Feb 2013, 08:54
REC MAX gives you .3G buffet margin, but you can choose a FL higher than that limited by .2G margin
Stuck_in_an_ATR
12th Feb 2013, 11:55
From the FCOM:
RECOMMENDED MAXIMUM ALTITUDE (REC (javascript:extendABB('ABB_00011142.0001001_N1000D','Recomme nded')) MAX (javascript:extendABB('ABB_00011142.0001001_N10010','Maximum ')))
The recommended maximum altitude is the lowest of the maximum altitude that:
-The aircraft can reach with a 0.3 g buffet margin
-The aircraft can fly in level flight at MAX (javascript:extendABB('ABB_00011142.0001001_N10032','Maximum ')) CRZ (javascript:extendABB('ABB_00011142.0001001_N10035','Cruise' )) rating
-The aircraft can maintain a V/S (javascript:extendABB('ABB_00011142.0001001_N1003E','Vertica l Speed')) of 300 ft/min at MAX (javascript:extendABB('ABB_00011142.0001001_N10048','Maximum ')) CLB (javascript:extendABB('ABB_00011142.0001001_N1004B','Climb') ) thrust
-The aircraft can fly at a speed higher than Green Dot and lower than VMO (javascript:extendABB('ABB_00011142.0001001_N10054','Maximum Operating Speed'))/MMO (javascript:extendABB('ABB_00011142.0001001_N10057','Maximum Operating Mach'))
-The aircraft is certified at.
So, it's not only about buffet margin, but also performance-related. My guess is that with lower CI the a/c flies at lower speed, thus is able to maintain it (or climb) using less thrust - hence higher REC MAX FL...
Do you want me to run some tables from the PEP for you guys? It shows everything in far more detail than the FCOM