View Full Version : Your Cost Index and Mach SPD over the Atlantic

14th Apr 2010, 17:28
Good Day,

I am planning on writing a paper for college on the affect rising fuel costs have had on cruise speeds and cost indeces over the past decade for commercial aircraft.

So for those of you that don't mind giving me some info. i would appreciate:

Aircraft type:
Cost Index: (if not applicable then state you CRZ mach used)
CRZ Mach used over the Atlantic or when on a NAT: (if applicable)
Airline: (at your discression)

Feel free to add any extra info.

thanks in advance!

Willit Run
15th Apr 2010, 04:02
Mach speed over the atlantic in the NAT track system must be a constant mach! Cost index doesn't realy apply over the atlantic. When you get your NAT track clearance, you are given a specific mach speed to maintain. You can fly a cost index before and after the NAT track system, but over the atlantic, you must maintain a constant mach speed.
On the 744, we usually fly .85 +- .01

15th Apr 2010, 05:04
B777-300ER Normally plan and receive clearance @ M0.84...sometimes given M0.83..cleared level can be 3,000' below optimum...

15th Apr 2010, 11:00
Years ago it was .85 for B-747-400 and Cost Index 250.

Now reduced back to Cost Indexes around 40, so Mach .82-83. Fly at constant Mach on the Tracks as previously mentioned, but we are supposed to ask for a Mach re-clearance at various times, as fuel burns down or winds change.........but most are too lazy to do it.

Flying so close to Max Range is getting silly.

16th Apr 2010, 09:44
Few years ago we were flying 75s round at CI 55-65 generally. Flying round now at 21-23 usually, and Mach numbers .78-.79.

Flying the 76s round at the moment (recently fitted with winglets) at CI 6-10 and depressingly slow .76 - .77ish!!

16th Apr 2010, 11:33
A310, Cost Index 30 which gives ~.80 Mach. When on constant Mach .80 is used. Sometimes Mach .79 or .81 is used depending on winds, FL, etc.

16th Apr 2010, 11:42
Short haul 757 CI 30 .78 - .79 ish. Used to be CI 50 .79 - .80. Long haul 767 CI 30, but .80 overwritten for NAT.

16th Apr 2010, 17:22
A-330 Cost index 60 and M.82 in the NAT TRACK

16th Apr 2010, 19:04
Default for BA747 (as if 6 months ago when I took VR) was:

CI=0 for climb than CI=90 until NAT then typically fixed M0.85, then CI=90 to 10,000ft etc.

Variation from above if quick flight time, in which case CI for cruise and mach for fixed speed portions could be varied downwards to achieve schedule, eg CI=0 and Mach 0.82.

16th Apr 2010, 19:33
b777 flown at cost index 29 most places but in nat fixed speed .83. used to be .84 in the good old days:rolleyes:

17th Apr 2010, 12:09
B-HKD, concur with most of above posts. We fly A330's on CI's of 14-16 now, gives M.81 in cruise but in MNPS this must be pegged at your OCA CLX speed.
An interesting development of low Cost Indices is that the descent speed becomes very slow (A320/1=250kt, A330=260kt) and one just holds other traffic up, so ATC usually ask you to speed up anyway! Oh well, we did try...:)

max payload
20th Oct 2011, 16:01
Good to see that you all have slowed down :)

CI is of course (variable) Cost of Time divided by the Cost of Fuel (using different parameters depending on metric or non-metric numbers).

Now, Cost of Time doesn't change often (contract negotiations, change of MRO), however, the Cost of Fuel does.. compared to 12 months ago the average fuel price is 30% higher and so, consequently, your CI values should be about 30% lower than last year when you all posted to this thread.

In theory.

Once CI values approach the lowest 10s other factors start playing a role as well.. by now schedules are stretched upwards and additional crews are required to fill those higher block times, etc., creating additional cost; not to mention of course that aircraft are ECONning at very low speeds and high alphas, even close to stall. Not good.

And yes- ATC still doesn't get it after all these years, even though most everybody is cruising in sloooowly nowadays.

So what is wise here?

Cruising at fixed Mach speeds will always cost more in relation to CI-managed cruise, as ECON cruise takes into consideration the impact of winds and temperatures on specific range, resulting in optimized speeds for the given circumstances compared to the more coarse corrections used in fM flying.
Fuel efficiency-wise MRC (or 1% less, LRC) just won't do compared to CI=0

Maybe it's time for a CORRECTED Cost Index, a CI value which is looped back to scheduling and takes into consideration the overall network effect of slowing down or speeding up the fleet; city-pair specific fuel price deltas of course (sector-specific CI values) and additionally, specific aircraft operating limitations by only allowing a certain band of ECON speeds, a minimum and a maximum for example.

The one who has the correct answer can sell a very nice tool :)

Max :ok:

21st Oct 2011, 13:28
B777-300ER, CI 26 to 29, too slow. In the CFP the constant M is filed with around .84 to .85 it depends on the day and time.

Before reaching the NATS entry point the speed is re-checked at the FMC Legs Page and E/ is entered at the Exit point. The speed increases at the entry from ECON to the cleared track speed and at the Exit point it decreases again to ECON.

On the NOPAC it is not that busy as the NATS, you do not need a extra clearance to enter the tracks. That is automatically done with your ATC clearance on the Ground.

Another colour another name, the rest is the same, no big diffrences.

Fly safe and land happy


23rd Oct 2011, 00:04
B777 - 200ER and B777 - 300 ER

Normal CI used is CI 50 for both types.

This gives M.82 - M.83 for the 200ER and M.83 - M.84 for the 300 ER.

On the North Atlantic use M .83 ( NO CI used after the crossing the OEP until leaving Oceanic airspace, although westbound some of the Canadian airspace has separate rules) for both types.

23rd Oct 2011, 00:42
Boeing 747-400

Typical Cost Index 15-25

Usually Mach .83

Airline: Cargo