Mach Number?

[ajpongress 467]

CI values change constantly with airlines as fuel prices fluctuate.

Who knows how old that list is. The data is outdated.

[Tabs 2,790]

Anything above 40 seems pretty high to me for an NG. Remember that CIs aren't calibrated to the same scale across different airplanes. 100 on a 777 or a 757 isn't the same thing as 100 on an NG. The scale is logarithmic and 0-60 or so is where most of the difference is in the NG. Above 60 there's very little change.

 

With regard to changing Mach number in flight - if ATC asks you to do this, you're just going to speed intervene on the MCP or just enter it on the CRZ page, you're not going to hunt around for it by changing your CI...

[steve inwood 67]

Yeah just been looking.. I have found something quite interesting on the net but for obvious reason i won't be putting it on here as it has boeing all over it. But is say that CI'S =20 for the NG in sept 2009

[scandinavian13 5,192]

With regard to changing Mach number in flight - if ATC asks you to do this, you're just going to speed intervene on the MCP or just enter it on the CRZ page, you're not going to hunt around for it by changing your CI...

 

Definitely. And, chances are, when it's requested, it's generally an imminent need (not immediate, but not something to take your time with), so time is of the essence.

[NM5K 1]

The distance and altitude flown will also effect the cruise speed, even using the same CI.

For instance, if I fly from KHOU to KDAL, I plan for the usual FL 300, and the cruise speed

will end up around mach .74 or so using a CI of 36-40.. The mach cruise speed is fairly low

because you are near the "IAS/mach merge" altitude. To bump up to mach .78-.79 would

have the IAS too high. The general maximum IAS the FMC will use on the NG is around 320

or so.. But a CI of 40 will have my IAS at just below 300..

 

But say I fly from KHOU to KOKC, I'll run up to usually FL380, and my cruise speed with the

same 36-40 CI will be around mach .79 or so. But my IAS will be lower than the trip to

Dallas. I'm higher up, and farther from the "merge" altitude, so the FMC will let it run at

a higher mach speed because as one climbs, the IAS keeps dropping on down.

On the majority of my longer flghts, mach .78-.79 is the usual speed I see.

Running a higher CI will not effect the mach cruise speed near as much as the IAS

when climbing and descending. IE: if I ran a CI of 60, I'd still probably cruise around

mach .79, but will climb and descend using a higher IAS than the 36-40 CI range I usually run.

[Fabo 213]

The standard Cost index for the likes of Ryanair is 80

 

No way, these days with this fuel... and RYR cheap labor... (Can you imagine being hired by, say, a police force, and said "Hey this here is your uniform. Wear it always or you are fired. It will be 50 pounds btw."?)

 

That table contains a lot of garbage data.

 

Not garbage per se.... just old.

[Avi8tor1 1]

Wow. I would've never guessed the CI would have gone as low as 10-20. But it's not surprising, considering how much I complain about the cost of a $40 fill up in a Civic...yet alone an airliner!

[rgamurot 1]

Another thing to note similar to the ATC requested speed, when you're outside of radar contact for an extended period of time (i.e. ETOPS), you will actually enter the filed Mach number in the CRZ page of the FMS. This is because ATC uses position estimates based on this number. Mind you, you can always let ATC know you're going to use a different speed and enter that if they allow it.

 

As far as actually calling ATC on ETOPS routes, they expect you to check back in with them when you told them you would unless you call back and amend the time. Believe it or not but you have up to three minutes after your due time before the controller starts trying to call you to see if you're still alive. Search and rescue is called after just 15 minutes.

 

Ryanair will usually fly to about 37000 ft to places like spain and corfu .. of course places like Germany are about 24000 ft below and ireland is about 15000 depends on weather and traffic.

 

Slightly off topic but are you absoutly sure Ryanair flies that low? Germany is about the same distance as Spain from Ireland (depending on the destination of course). Here for Hawaiian (yes, I know we use B712's interisland but work with me here), Hilo to Honolulu they're up at FL280 and the route is less than 200nm. From Lihue to Honolulu they go up to 16,000' and thats less than 100nm.

[CONTAG 2]

Hi guys,

 

Cost Index for Ryanair ops is set to 30 for the last 3 years or so (It was 35 previously).

 

It doesn't make any sense at all to fly as low as it was said before in this post... Ryanair SOPs state to fly as close to the optimum level as possible. That Mach number is going to change depending on the actual flight conditions such as flying below the opt level, head/tail winds, cost index etc.

 

And on top of this, you can be asked by air traffic control to increase or reduce speed to mantain separation with other aircrafts.

 

So, for Ryanair: CI = 30 and CRZ as close to the OPT LVL from FMC.

 

Regards!