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Virgin on a go slow?

Old 31st Jul 2011, 08:10
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Virgin on a go slow?

Overheard an interesting conversation this arvo between BN CEN and several Virgin flights. The controller seemed baffled by their slow speed. When asked, the pilots responded that they were cruising (.61 to .63 mach) at such a cost index because the company "beancounters" instructed them to and insisted that they not diverge from these speeds.

Doing some (rough) calculations that puts a TAS at FL370 at about 355kt... thats slower than a Q400 at FL230! Granted, this was a quick calculation using a website I found (old CR-2 evades me...), and may be slightly out.

Don't you guys usually get about at .74-.78 depending on cost index??? That seems like an enormous difference. What's the deal? Just interested, as was the bloke I was flying with.
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Old 31st Jul 2011, 09:13
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Smile

No Dash 8-400 in Australia is flying at 360kt TAS. "Something about engine longevity". They are more than likely operating around the 300-310kt TAS.
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Old 31st Jul 2011, 09:25
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At the moment we are actually being able to use our designed cruise power in the q400 so on average TAS around 360kts.... Untill the company tell us we cant, in which case after getting used to the extra speed I don't think anyone will stop anyway..
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Old 31st Jul 2011, 09:45
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I also heard that now "detent" is used in cruise the fuel bill is even less! I'm amazed Bombardier know more about the q400 than the Tamworth aeroclub.
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Old 31st Jul 2011, 10:12
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End of the month , the boys are into overtime !
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Old 31st Jul 2011, 10:17
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At FL 370 Mach .63 equals about 360 kts TAS and only around 200 KIAS.
A bit slow I would suggest for a 737, especially if you need to maneuver.

There wouldn't be a cost index that would give that slow a speed, CI 0 would be about Max Range Cruise and that would certainly be faster than .63, more like .75 perhaps?

I'm guessing but about Mach .68 to .70 giving 210 KIAS and 400 TAS would be about as slow as you would dare go up at 370 BUT that wouldn't burn the least fuel over a trip.

Last edited by nitpicker330; 31st Jul 2011 at 10:31.
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Old 31st Jul 2011, 10:27
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Maybe it was an EMB?
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Old 31st Jul 2011, 11:00
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Does it matter? The issued cost index giving 0.61-0.63 is obviously less than standard cruise. Aircraft type is irrelevant.
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Old 31st Jul 2011, 11:26
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Econ with a C.I of 4 or 5 which is what is being used at the moment would give a cruise Mach of .63 or .65 down at fl 250 or fl 280. Depending on the headwinds that might be the planned level, and so be it. You can't cruise at .63 or .65 in a 737 at fl 370. I will categorically say there is no go slow. We are almost to a man (and woman!) supportive of the changes to the company and our future under J.B.
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Old 31st Jul 2011, 11:31
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Dragun, Wrong..........."..................
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Old 31st Jul 2011, 11:33
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Nothing like a 76 up your date at those speeds. Are you fellas letting ATC know? Nothing like running 7 or 8 miles between a couple of planes on climb (you fellas tend to follow each other around) to have the first one cruise at those mach's. Sphincter tends to tighten a little when you haven't been told
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Old 31st Jul 2011, 11:37
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Sorry Jack, why would you have to notify anyone? It's already in the plan. It's not a decision the line drivers would make on their own, unless there is a mechanical reason for it.

Wrong on what count, auto brakes?
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Old 31st Jul 2011, 11:45
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Porch,

Those cost index mach numbers are not the numbers published in our books. We expect you to cruise at your published figures, if not, let us know We don't have the time to check every flight plan!
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Old 31st Jul 2011, 12:57
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The C.I dictates the Mach no. It simply varies with altitude. The plan will have the altitude, are you telling me that your flight plan notification doesn't have the tas/MN on it? If our plan says FL 260 at .63, that is what was submitted to you guys. Are you saying that isn't so?
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Old 31st Jul 2011, 13:01
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I certainly hear what you say DNS, but no, they don't usually think like that. The usual thing would be that we'd up the speed at the lower level, cause that's what jets were made for! But if we were originally planned low and slow, then that wouldn't necessarily occur.
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Old 31st Jul 2011, 13:03
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Jack, we don't have access to the range of numbers either. I always figured that's why we submitted flight plans........
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Old 31st Jul 2011, 13:10
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On a VB 737 tonight SYD-ADL. Took about 2 hrs 15 mins.

The seat back track showed a consistent g/s of less than 600 km p/h ( around 320 kts) at FL240. Forecast winds around those levels were only -45 kts, slow trip, blamed by crew during pa on strong headwinds, 45 kts I don't think so, go figure.
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Old 31st Jul 2011, 13:22
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business model for cost index.

So who is doing the CI calculation these days and what answer did they get?

Wonder if they recalculated the schedule blox times with the lower CI. Sounds like the AN days of low and fast in the 767 to beat the skippy jet.

Jack Ranga

Cruise scheduled flight planned should match the ATC flight plan. If the crew are telling you they are different write them up. Good trick that one bro!
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Old 31st Jul 2011, 13:29
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That's my point marauder. At that fl the 4 or 5 CI would produce only .63 or so, so slowish sector. The alternative however, up high, might be 150kts on the nose or more. Some bean counter has worked out that it will use less fuel at the lower slower profile. So that's the plan we get handed. Unless there is a real reason to do other, we fly the plan.
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Old 31st Jul 2011, 14:28
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We expect you to cruise at your published figures, if not, let us know
I know it's slightly different but I've been meaning to ask - when ATC says "Hold at XXX, expect to depart XXX at XXXX, speed reduction approved.", is there any limits to the speed reduction?
Heard some ATC cracking it the other day because a 737 slowed down to 215KIAS and "that if you are going to slow down that much you have to let us know." Huh? Since when?
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