[aaronspink]

Originally Posted by tongue_of_colicab

Would be interresting to see how that turns out if you take in to consideration the extra stress on the airplane and aircrew along with the fact that flying for 2 hours longer means you lose 2 hours in which you could have an additional 300+ paying passengers going someplace else with your aircraft.

99% of airframe stress is takeoffs and landings. The average longhaul airplane will fly close to 10x the hours and miles of your average 320/737 over its lifetime. Inflight stress is pretty minimal on both airframes and engines. Engines run a little higher than idle during most of the flight envelope but are at max/near max thrust at takeoff.

[aaronspink]

Originally Posted by RudeCurve

Are you sure about that? About 2/3 of every flight that I've taken there was at some point during the flight some scary turbulence that shakes the whole plane as if you were experiencing an earthquake.

Yes. That turbulence is doing almost nothing to the airframe. The only way turbulence does real damage to an airframe is from either massive updrafts or downdrafts. Almost all turbulence affects the fuselage equally and it does move the plane but the WHOLE plane. The massive updrafts and downdrafts are what puts undo stress on the wings do to the loading/unloading of the force on the wings.

[Sxotty]

Originally Posted by aaronspink

Yes. That turbulence is doing almost nothing to the airframe. The only way turbulence does real damage to an airframe is from either massive updrafts or downdrafts. Almost all turbulence affects the fuselage equally and it does move the plane but the WHOLE plane. The massive updrafts and downdrafts are what puts undo stress on the wings do to the loading/unloading of the force on the wings.

That doesn't really make sense. If you fly out of the air flow then it is going to put stress on the airframe and they won't know precisely when they are exiting the up/down draft.

[Mize]

Most turbulence puts negligible areas on the airframe. Yes, extreme turbulence can, but remember things like a 747 wing being able to withstand a 30 foot defection.

Scary turbulence isn't the earthquake shaking tat is common. Massive drops (>100 ft in a second or two) that toss people into the ceiling is significant and scary. experienced that a couple times...

[aaronspink]

Originally Posted by Sxotty

That doesn't really make sense. If you fly out of the air flow then it is going to put stress on the airframe and they won't know precisely when they are exiting the up/down draft.

hence they generally try to avoid large up and down draft areas, but outside of large up and down drafts, turbulence isn't really a factor in fatigue. Simple cabin pressurization and depressurization has a much much larger effect. pressurization effects are the main limiter to aircraft cycles.

[zed]

Originally Posted by Mize

zed, 20% = 2 hours means a flight of 10 hrs - it wasn't Sydney mate. Hell Los Angeles to Sydney is like 18 hrs, right?

not that long Ive flow it a few times (I try not to normally I fly over asia) its about ~10-12 hours LSAX is crap the only place in the world (well perhaps not ) where u have to get your passport checked without leaving the airport (& when youre on a +24 hr flight thats the last thing u want is some dude yelling in your ear, halfway through when you just want to sleep.)

Anyway, as I said, the airlines aim for the most fuel efficient route. Always.

no I dont believe they do, Like I mentioned before, now that was the most efficient flight, the thing is the flight is longer which ppl are not happy about I'll dig up info later on when Im not so tired

(edit)
OK from a little googling this I think is what I remember (from 2008 amazing how the mind still gleens details from years ago, maybe not 100% accurate but the broad strokes)
http://www.aspire-green.com/mediapub/docs/0801.pdf
IIRC the thing was the flightpath they followed was not the shortest distance at all (it was the most fuel efficient) but added a couple of hours to the flight , someone can google their flightpath perhaps?

from googling heres a NZ perspective
http://www.worldculturepictorial.com...perfect-flight

[Mize]

Just googled it...13.3 Sydney to LAX 14.5 LAX to Sydney.
Anyway, can you please explain - other than closed airspace - why an airline flies this less-fuel-efficient route intentionally? I'm talking motive. Please.

[zed]

from googling heres a NZ perspective
http://www.worldculturepictorial.com...perfect-flight[/QUOTE] (no XXX intention)

ha - I see also 2008, must of been in vogue then,
now heres a rant

http://en.wikipedia.org/wiki/Overwhe...arge_Telescope

The OWL could be expected to regularly see astronomical objects with an apparent magnitude of 38; or 1,500 times fainter than the faintest object which has been detected by the Hubble Space Telescope.

1.5 billion euro's!, ready this decade!!!
too much cash, yet we'll spend our money on other 'important' crap
1.5k times the light gathering of hubble!!!! (which has given us some amazing images so far)
yet the US has paid out over 1,000 billion euros on a new jet (which aint ready sofar) i.e. some wankery military endeavor is > 1000x what science is worth. I dispair, I do

[aaronspink]

Originally Posted by zed

no I dont believe they do, Like I mentioned before, now that was the most efficient flight, the thing is the flight is longer which ppl are not happy about I'll dig up info later on when Im not so tired

Yes they do try to do the most efficient route possible. There are always various reason why one wouldn't do the GC route. In the case of deep southern pacific routes, this is generally either do to jetstream, weather, or general navigational issues(ie you tend to fly to beacon point headings and there are very few of them in the southern pacific and there are also off ATC separation rules that need to be followed).

[aaronspink]

Originally Posted by Mize

Just googled it...13.3 Sydney to LAX 14.5 LAX to Sydney.
Anyway, can you please explain - other than closed airspace - why an airline flies this less-fuel-efficient route intentionally? I'm talking motive. Please.

They don't. The only reasons they don't always take GC is weather, jet stream, and navigational. The articles that zed is pointing out are just pilot projects for GPS based navigational technologies and realtime/near realtime weather based course correction updates.

One factor is that the vast majority of flights are still using beacon based navigation and pre-computed weather information. There are ongoing pilot projects to switch those over to realtime satellite based weather updates and GPS navigation for greater efficiency. It is generally easier to do the early stages of those pilots using low congestion routes which the AUS/NZ<>US routes are. They also benefit the most of GPS based routing vs beacon based routing due to the low number of radio beacons within the southern pacific and the issue that the flights operate almost entirely outside of an ATC domain.

[Chalnoth]

Originally Posted by UniversalTruth

Thanks for the nice opinion.



Yes, but it's you who pays the bill in the end, not the airlines.



Please, for God's sake, don't tell me that Minneapolis, Saint Paul (MSP) is in that direction.

I think it's time you invest in a globe and a piece of string. Take the globe and the piece of string, stretch the string between two places, and the line the string makes when fully-stretched will be the great-circle path between those two points. Compare to flight plans.

[Mize]

copycat.

[Simon F]

Originally Posted by Mize

copycat.

Of whom? Me ( 23-Jul-2012, 12:09 ) or you (24-Jul-2012, 15:32) ?

[Mize]

doh!
flattery Simon, all just flattery for you

[Simon F]

Originally Posted by Mize

doh!
flattery Simon, all just flattery for you

I must confess, not too long ago, I tried to explain something similar to my 8yo.

[zed]

sorry forgot about this, after a bit more digging
http://www.aspire-green.com/mediapub..._plan_2011.pdf
see section 3.3.1 etc

Yes they do try to do the most efficient route possible.

actually they dont, up until this initiative ~2008 aircraft would fly between weighpoints(sp) along flightpaths, eg that image above looks like they are, i.e. the plane hits the hebrides (I think) and does a turn

http://www.greenaironline.com/news.php?viewStory=292

The first demonstration occurred last month in which an Air New Zealand Boeing 777 flight from Auckland to Los Angeles managed to save an estimated 4,500 litres of fuel

4500 liters, how many passangers is that worth? a couple prolly at least.

when u think about it, It seems batshit crazy it took them until the fuel crisis in 2008 before they started actually implmenting this

[Chalnoth]

Originally Posted by zed

when u think about it, It seems batshit crazy it took them until the fuel crisis in 2008 before they started actually implmenting this

Well, my guess is that for a long time, they simply followed the shortest distance path. It's only been in relatively recent years that computer power and our measurements of weather patterns have been up to the point where we could actually perform more fine-grained optimization, and it is entirely understandable to me that airlines would be a bit slow to adopt newer flight planning strategies.

[zed]

Well, my guess is that for a long time, they simply followed the shortest distance path.

they never did, what they did was fly from waypoint to waypoint, flightpath corridoor (see the map above over the UK) now the shortest path between 2 points on a globe is a curve right? but u will see there after it takes off, it flys ~1000km straight ahead then does a ~5 degree turn to the left (just above the hebridis) and then flys straight ahead. Speaking as someone who's flow many (at least 30) ~12 hour flights I know this is how it goes every 1/2 or hour you can feel them doing a slight turn (& can see it on the onboard radar)

why its crazy is, all air companys make bugger all profits (if any) thus this wastage is pretty unbelievable

[aaronspink]

Originally Posted by zed

they never did, what they did was fly from waypoint to waypoint, flightpath corridoor (see the map above over the UK) now the shortest path between 2 points on a globe is a curve right? but u will see there after it takes off, it flys ~1000km straight ahead then does a ~5 degree turn to the left (just above the hebridis) and then flys straight ahead. Speaking as someone who's flow many (at least 30) ~12 hour flights I know this is how it goes every 1/2 or hour you can feel them doing a slight turn (& can see it on the onboard radar)

why its crazy is, all air companys make bugger all profits (if any) thus this wastage is pretty unbelievable

For pretty much any location except deep southern pacific routes, located beacon flying is within noise margin of great circle or best route (aka modulo winds). It is only the deep south pacific routes that have a lack of beacons.

[Chalnoth]

Originally Posted by zed

they never did, what they did was fly from waypoint to waypoint, flightpath corridoor (see the map above over the UK) now the shortest path between 2 points on a globe is a curve right? but u will see there after it takes off, it flys ~1000km straight ahead then does a ~5 degree turn to the left (just above the hebridis) and then flys straight ahead. Speaking as someone who's flow many (at least 30) ~12 hour flights I know this is how it goes every 1/2 or hour you can feel them doing a slight turn (& can see it on the onboard radar)

why its crazy is, all air companys make bugger all profits (if any) thus this wastage is pretty unbelievable

Following a great circle involves only flying straight ahead. There are no turns involved with an aircraft that follows a great circle path. The waypoints are generally used to make sure they stay on course, and the turns are likely course corrections to either avoid storms, to get back on path after drifting off the flight plan, or because the aircraft hasn't followed a great circle path for some reason or other.