plane question

[decayer]

I was wondering...

 

I'm currently living in Cyprus and study in the UK. When I take the plane from England to Cyprus the flight takes more or less 4 hours. When from Cyprus to England it takes approximately 45 minutes more. Same plane, same speed, same distance.

 

Thanks

[ydoaPs]

Different time zones?

[insane_alien]

or prevailing winds. possibly the jetstream. while the indicated airspeed would be the same the ground speed would be slower.

[Cap'n Refsmmat]

You may be fighting prevailing winds when you're flying to the UK.

 

edit: blast you, insane_alien.

[decayer]

Does it have any relevance to the rotation of the earth? If you are going with it you go faster, if you are going against it you go slower? Or it doesn't matter because the atmosphere of the earth also rotates?

[Cap'n Refsmmat]

The atmosphere does indeed rotate with the Earth. Otherwise there'd be a nasty 1,000MPH wind at the equator.

[decayer]

Yeah, but it rotates to one direction. Let's say the plane is going the opposite direction?

[Klaynos]

nearly definitely winds.

 

decayer, the atmosphere and planet can be considered at rest with each other, and therefore the plane would travel the same distance through the same effect due to rotation both times....

[decayer]

So, are these winds always the same? Blowing towards the same direction? Because it always take 45 minutes longer to go therefore 45 minutes less to come.

[Klaynos]

There will be prevailing winds in the altitude bands in which you always fly. You may well be able to find maps online. As they're prevailing in the majority of cases you will have a roughly the same time difference.

 

Often flights fly in different directions at different altitudes to allow for this.

[decayer]

Because at different altitudes the friction factor can be bigger or smaller in relevance to how thick the air is?

[Klaynos]

I think it's more tehre are different currents at different altitudes, as to why this is I dunno, it's probably a chaotic system that is stupidly complicated

[swansont]

So, are these winds always the same? Blowing towards the same direction? Because it always take 45 minutes longer to go therefore 45 minutes less to come.

 

Once you account for this, then you have to add in the artificial impact of schedule. If it's assumed that the winds will aid/delay you by 45 minutes, and the actual delay is less, the plane will slow down as it approaches the destination, to fit into the scheduled landing slot.

 

(I recall a trip from London to Wash DC, where were 30+ minutes ahead of schedule as we reached North America, and we "burned" it all doing a slalom track across the northeast US and circling Dulles airport. Landed "on time")

[thedarkshade]

Probably winds, or altitude.

[insane_alien]

darkshade, why is it that you always just restate what everyone else has been saying without really adding anything?

[Blue Fire]

I would submit that often routing and air traffic control would have a big impact. Flights in the U.S. often do not fly the exact same route to and from destinations in order to avoid airspace conflicts according to air traffic control. Thus, one direction may indeed take longer because the airplane is traveling a slightly different and longer route that you may not notice as a passenger.

[thedarkshade]

darkshade, why is it that you always just restate what everyone else has been saying without really adding anything?

I express my opinion, what I think and what I believe.

 

Take it this way, if you open a thread that has a question like "Is taking drugs harmful?". Everyone would reply yes. But if only one replied yes, and other didn't because there was just one yes on the thread you would get an impression that taking drugs isn't harmful since for 300 views you got one yes.

 

Everyone should express their own opinions, and if you have a problem with that, then suck it up and deal with it!

[insane_alien]

yeah, but you could at least try and put in something that takes other explanations a bit further and actually add something to the discussion. maybe you have a question or have spotted something another person left out.. it makes for very boring discussion when everybody is just repeating everybody else.

[John Cuthber]

Is it just me or is this

"nearly definitely winds.

decayer, the atmosphere and planet can be considered at rest with each other"

a contradiction?

The wind is what you get when the air isn't at rest wrt the earth. Also I'm sure the earth's rotation is part of the explanation of things like the trade winds, doldrums and jetsrteam.

[Klaynos]

Order of magnitude difference between the rotation speed and the wind speeds.

 

If trade winds where related to the earths rotation, how do you explain this map:

 

http://en.wikipedia.org/wiki/Image:Earth_Global_Circulation.jpg

 

They go in both directions...

[zeig]

Does it have any relevance to the rotation of the earth? If you are going with it you go faster, if you are going against it you go slower? Or it doesn't matter because the atmosphere of the earth also rotates?

 

yea wouldn't that mean theres wind pushing against you more when you fly oppisite of the earths rotation?

[John Cuthber]

"If trade winds where related to the earths rotation, how do you explain this map:"

I don't. I just point out that they all seem to go perpendicular to the axis of the rotation. Quite a coincidence if there's no relation.

However, a quick look on wiki and I find "The surface air that flows from these subtropical high-pressure belts toward the Equator is deflected toward the west in both hemispheres by the Coriolis effect. "

Now, I'm pretty sure the coriolis effect has a lot to do with the earth's rotation.

(Nice map BTW, it's on the same page I quoted)

http://en.wikipedia.org/wiki/Trade_wind

[Klaynos]

The Coriolis effect is indeed due to the rotational reference frame of the earth. But only changes their direction not magnitude.

[John Cuthber]

The difference between an inbound and an outbound flight is a change in direction not magnitude. I think the earth's rotation has an effect, albeit an indirect one.