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787 Cruise Mach at Cost Index 300

Posted: Sat Nov 27, 2021 6:58 am
by Pellegrine
I found this article interesting:

https://simpleflying.com/kenya-airways- ... d-dispute/

Cutting the block time on NBO-CAN from 11:30 to 10:15 is pretty significant. I've read elsewhere that at CI300 a 787 cruises around M0.86 and at a low CI it will be below M0.85, even though the plane is designed around a cruise mach of M0.85.

The fastest flight time I see for NBO-CAN is 9:29: https://www.flightradar24.com/data/flig ... 2#29d70003. A lot of the other flights are an hour or so longer. According to my flight planning software the route for this flight (the 9:29 flight and the average route) is around 4,793nm.

So how fast is this airplane going at CI300 vs. say CI50?

Re: 787 Cruise Mach at Cost Index 300

Posted: Sat Nov 27, 2021 8:35 am
by Aaron747
Wow, that's a pretty brazen ops approach - how did they think the union wouldn't notice what was up? (or plain didn't care...)

Also...the young feller who wrote that article should work on his punctuation.

Re: 787 Cruise Mach at Cost Index 300

Posted: Sat Nov 27, 2021 9:01 am
by T54A
About 496kts at FL350

Re: 787 Cruise Mach at Cost Index 300

Posted: Sat Nov 27, 2021 9:03 am
by gloom
Pellegrine wrote:
So how fast is this airplane going at CI300 vs. say CI50?


CI is not about speed, it's all about cost (fuel consumption) as the name says.

Depending on wind (tail/head, speed), it will be different. Typically, 300 is asking for high speed standard cruise (.86, as you say), low CI (say 30s) will give values around .83-.84.

See the Boeing article on CI (pre 787, so it does not give a numbers for 787, but explains idea behind CI unit, and how it affects flight parameters):
https://www.boeing.com/commercial/aerom ... Series.pdf

Cheers,
Adam

PS. Many airlines prefer to fly Ma number rather than CI. FP and operational procedures will then indicate constant Ma cruise, say at .85, or .84, whatever an airline considers a good balance between time and fuel consumption. I know both LH and LO do (or did) that sort of cruise speed calculation. Go on 280/.74/300 profile, and it's done. Would you care to guess the plane by numbers? ;)

Re: 787 Cruise Mach at Cost Index 300

Posted: Sat Nov 27, 2021 9:29 am
by zeke
Pellegrine wrote:
Cutting the block time on NBO-CAN from 11:30 to 10:15 is pretty significant. I've read elsewhere that at CI300 a 787 cruises around M0.86 and at a low CI it will be below M0.85, even though the plane is designed around a cruise mach of M0.85.


This really has nothing to do with how fast the aircraft is flying, it is what the airline schedules the flight time as. Under EU ops, the PLANNED number of crew is based upon the SCHEDULED block time, if on the day the actual block time on the flight plan is greater than schedule (or 10:30) no crewing numbers change.

There is zero penalty for the airline if the schedule is 10:30 and the actual is 11:00, they only need to schedule 2 pilots.

The eastbound flight should always be faster than the westbound flight due to the prevailing winds.

gloom wrote:
PS. Many airlines prefer to fly Ma number rather than CI. FP and operational procedures will then indicate constant Ma cruise, say at .85, or .84, whatever an airline considers a good balance between time and fuel consumption. I know both LH and LO do (or did) that sort of cruise speed calculation. Go on 280/.74/300 profile, and it's done. Would you care to guess the plane by numbers? ;)


I don’t know any airline that flies around at a seated Mach number in a modern aircraft unless it’s an ATC speed constraint. Everyone I talk to fly ECON speeds which are a function of CI, weight, altitude, and environmental conditions.

Re: 787 Cruise Mach at Cost Index 300

Posted: Sat Nov 27, 2021 9:33 am
by jman
Pellegrine wrote:
I found this article interesting:

https://simpleflying.com/kenya-airways- ... d-dispute/

Cutting the block time on NBO-CAN from 11:30 to 10:15 is pretty significant. I've read elsewhere that at CI300 a 787 cruises around M0.86 and at a low CI it will be below M0.85, even though the plane is designed around a cruise mach of M0.85.

The fastest flight time I see for NBO-CAN is 9:29: https://www.flightradar24.com/data/flig ... 2#29d70003. A lot of the other flights are an hour or so longer. According to my flight planning software the route for this flight (the 9:29 flight and the average route) is around 4,793nm.

So how fast is this airplane going at CI300 vs. say CI50?


What software are you using that tells you this?

Re: 787 Cruise Mach at Cost Index 300

Posted: Sat Nov 27, 2021 11:25 am
by hitower3
gloom wrote:
I know both LH and LO do (or did) that sort of cruise speed calculation. Go on 280/.74/300 profile, and it's done. Would you care to guess the plane by numbers? ;)


My guess would be a 737 classic.
Hendric

Re: 787 Cruise Mach at Cost Index 300

Posted: Sat Nov 27, 2021 8:05 pm
by Pellegrine
zeke wrote:
This really has nothing to do with how fast the aircraft is flying, it is what the airline schedules the flight time as. Under EU ops, the PLANNED number of crew is based upon the SCHEDULED block time, if on the day the actual block time on the flight plan is greater than schedule (or 10:30) no crewing numbers change.

There is zero penalty for the airline if the schedule is 10:30 and the actual is 11:00, they only need to schedule 2 pilots.

The eastbound flight should always be faster than the westbound flight due to the prevailing winds.


Looking back over months, I guess you're right. The airline has just chosen to shorten the block time for their crew scheduling purposes. However, with a block time of 10:15 there are many flights that end up 10:40, 10:55, 11:15...that'd be unacceptable to me.

Re: 787 Cruise Mach at Cost Index 300

Posted: Sat Nov 27, 2021 8:11 pm
by Pellegrine
jman wrote:
Pellegrine wrote:
I found this article interesting:

https://simpleflying.com/kenya-airways- ... d-dispute/

Cutting the block time on NBO-CAN from 11:30 to 10:15 is pretty significant. I've read elsewhere that at CI300 a 787 cruises around M0.86 and at a low CI it will be below M0.85, even though the plane is designed around a cruise mach of M0.85.

The fastest flight time I see for NBO-CAN is 9:29: https://www.flightradar24.com/data/flig ... 2#29d70003. A lot of the other flights are an hour or so longer. According to my flight planning software the route for this flight (the 9:29 flight and the average route) is around 4,793nm.

So how fast is this airplane going at CI300 vs. say CI50?


What software are you using that tells you this?


The length of the route? ForeFlight with worldwide charts. And some other goodies. I don't have the exact route. I'll be back with what I approximated it as later.

Re: 787 Cruise Mach at Cost Index 300

Posted: Sat Nov 27, 2021 9:16 pm
by gloom
zeke wrote:
I don’t know any airline that flies around at a seated Mach number in a modern aircraft unless it’s an ATC speed constraint. Everyone I talk to fly ECON speeds which are a function of CI, weight, altitude, and environmental conditions.


I know LH was using fixed Ma at least a few years ago on their 330/340. LO used fixed Ma (.76) on their EJets when I last talked to a friend last year.
Both cases, I've got numbers (in terms of climb/cruise/descend speed profile). Unless someone flying cheated me, it seems to be the case at least a few years ago.

Cheers,
Adam

Re: 787 Cruise Mach at Cost Index 300

Posted: Sun Nov 28, 2021 9:51 am
by thepinkmachine
Fixed Ma is used for Atlantic crossing on transatlantic flights - but even then it is planned only between the oceanic entry and exit points Other than that it ECON speed (which for the 787 at low CI is almost always .84)