Does the rotation of the earth have any impact on flight times of an aircraft?

[walianboy]

Hi, I asked this question on Yahoo answers but didn't really receive an answer that convinced me.
I am not a Pilot but have an interest in planes and was just curious as to the above question.
Anyone who could shed some light will be sent some good karma.
Thanks
Rich
from the UK, living in Mexico.

[BOAC]

Remember the atmosphere rotates with the earth? Therefore the answer is no.

Karma shields down:)

Edit:
Actually the CORRECT answer is yes, since the rotation of the earth causes rotating weather systems which in turn affect the winds which then affect the flight time, but that is, I guess, not what you asked.

Just had to get that in before XXXXXXX posted a correction:)

May have to go without Karma after all:{

[BigEndBob]

Tomorrows World some time ago flew aboard Concorde to New York with an atomic clock, think it slowed down abit when compared to clock back at UK.

[FakePilot]

If we didn't have rotation, we wouldn't have time zones. Without time zones, you couldn't leave New York at noon at get to LA at 3:00 pm!

[mocoman]

flew aboard Concorde to New York with an atomic clock

But now you are talking about whether such effects are due to either general or special relativity.......:8

Could be argued both ways...but more likely you are referring to the 'slowing' of time due to gravitational influences so let's plump for general...;)

[Desert Diner]

yes :8

[DrKev]

But now you are talking about whether such effects are due to either general or special relativity.......:8
Could be argued both ways...but more likely you are referring to the 'slowing' of time due to gravitational influences so let's plump for general...;)
If we have two choices, the answer is special relativity. Then again, special relativity is of course a special case of general relativity where we don't have to worry about any sort of acceleration, just constant velocity. (Hence the names, though general was devised after special, hence, 'general relativity' and 'special relativity' rather than just 'relativity'. Clear as mud eh?)

So we'll say special just to keep things as "simple" as we can, but really it's all just relativity. :}

[Kolibear]

Only if its on a conveyor belt.

[Newforest]

At a tangent to the original asked question and theoretical of course, what if all the GPS satellites stopped for a second or five, would all planes land at the wrong airport?

[Cool_Hand]

Yes, rotation of the earth affects flight times.

Look at the flight times quoted for a trip from LA to London,

Outbound: c.10 hrs 20 mins
Return: c.11 hrs 20 mins

The distance is the same but the travel time is about an hour shorter. Aircraft cruise at very similar speeds (i.e. they don't fly any faster to get to the US) the world is rotating London to LA direction and hence it is rotating under the aircraft bringing the destination nearer to get to the UK while moving it away on the trip to the US.

With regards to GPS it's not specifically the time that the satellite has (i.e. 12 noon) but the accuracy that it maintains it, +/- 1 second every so many thousands of years. GPS relies on speed distance time calcs to give you the position relative to ground stations that keep the GPS satellites updated with their own position relative to the globe.

I hope that is as clear as mud.

The tomorrows world experiement was to see whether time slowed down the faster you travelled, so if you travelled at the speed of light it was hypothesied that time would stand still. I don't know how far that research has gone though.

[barit1]

The answer is: Indirectly.

The airplane flies in an air mass. If the air mass is moving in the same direction as the plane, that is called a tailwind - and the speed of the plane is added to the speed the air mass travels. Ergo, higher ground speed.

If the air mass is moving opposite the plane, it's a headwind, and the difference between the two speeds is the effective (lower) ground speed.

And the speed of the air mass is caused in part by the rotation of the earth, among several other factors.

OK?

[Kalium Chloride]

Look at the flight times quoted for a trip from LA to London,

Outbound: c.10 hrs 20 mins
Return: c.11 hrs 20 mins

The distance is the same but the travel time is about an hour shorter. Aircraft cruise at very similar speeds (i.e. they don't fly any faster to get to the US) the world is rotating London to LA direction and hence it is rotating under the aircraft bringing the destination nearer to get to the UK while moving it away on the trip to the US.


Sounds like cobblers to me. Transatlantic time difference is more to do with head/tailwinds. The Earth imparts rotational inertia to an aircraft while it's on the ground, and that inertia doesn't suddenly vanish when it becomes airborne. The Earth doesn't "rotate under" a transatlantic flight any more than it rotates under a hovering Harrier.

I think. :ugh:

[Kahalaan]

"Yes, rotation of the earth affects flight times.

Look at the flight times quoted for a trip from LA to London,

Outbound: c.10 hrs 20 mins
Return: c.11 hrs 20 mins

The distance is the same but the travel time is about an hour shorter. Aircraft cruise at very similar speeds (i.e. they don't fly any faster to get to the US) the world is rotating London to LA direction and hence it is rotating under the aircraft bringing the destination nearer to get to the UK while moving it away on the trip to the US."

As 'Kalium Chloride' suggested correctly ....the above is 'cobblers'.

The Earth gyroscopic activity is all 'relative' my dear Watson...it has nothing to do with the speed to/from your local supermarket in your car let alone flying from London to Los Angeles and v.v.

'Winds Aloft' is another matter. Once an airplane becomes airborne, then it is at the vagaries of those molecules flying around the planet as 'wind'. Generally speaking, in the northern hemisphere, those 'winds' fly from West to East, making a trip from LHR to LA a good hour or so longer than the return journey. This is largely due to the 'coreolis affect' for upper atmoshere winds in the N. Hemisphere. At the Earths polar equators, this affect is minimal (negligible).

i.e. 95% likely to have headwinds from LHR to LAX and 95% likely to have tail winds from LAX to LHR....greatly affecting flight times. For a given power-setting, an airplane flies at the same speed through the air molecules, if that airplane (with the same power setting) flies into a headwind, then the groundspeed will be lower in direct proportion to the headwind coefficient. Same goes the other way round with a tailwind. I mean that's why airplanes (where possible) land 'into' the wind, so as to minimise their actual groundspeed/touchdown speed.

K

[AlphaWhiskyRomeo]

The distance is the same but the travel time is about an hour shorter. Aircraft cruise at very similar speeds (i.e. they don't fly any faster to get to the US) the world is rotating London to LA direction and hence it is rotating under the aircraft bringing the destination nearer to get to the UK while moving it away on the trip to the US.


Nothing to do with this. All to do with the prevailing west to east winds over the Atlantic.

You can't say "the distance is the same" and then say "bringing the destination nearer". That does not make sense.

Me thinks you are winding us up a little bit.

[Kahalaan]

"the world is rotating London to LA direction and hence it is rotating under the aircraft bringing the destination nearer to get to the UK while moving it away on the trip to the US."

I say this gently, as I don't want to cause any mortal wounds.....but have you tried jumping up and down recently and wondered why you land on pretty much exactly the same spot on planet Earth? i.e. according to your theory...oh.....you look it up......hehe!

Edited for one typo.....K.

[grimmrad]

[QUOTE=Cool_Hand]Yes, rotation of the earth affects flight times.
Look at the flight times quoted for a trip from LA to London,[...]
The distance is the same but the travel time is [...] shorter. [...] it is rotating under the aircraft bringing the destination nearer to get to the UK while moving it away on the trip to the US.

Is that not rather due to the direction of the jet stream, going from west to east?
But, of course, I guess the jet stream is related to athmospheric phenomena related to the earth's rotation...

Best

[Gargleblaster]

We must not forget the Coriolis effect !

Any object moving on or around the earth is affected by this, and turned slightly to the right (on the northern hemisphere). This is why we have the air rotating in low and high pressure areas. I've read that railroad tracks get worn differently due to the Coriolis effect !

Imagine there is no wind anywhere, and you start off from the North Pole and aim directly for Singapore and then maintain that (true) heading.

When you pass equator, you'll NOT be over Singapore, but somewhere further west, because the Earth has moved Singapore further east.

So any aircraft flying a long distance will have to counter the Coriolis effect by steering very slightly off the otherwise intended heading.

I wonder how much fuel is actually spent on this on e.g. a LHR to NY flight ?

(I have to admit that I've never completely understood the Coriolis effect. I understand it for north-south moving objects (rotational inertia), but not east-west.)

[chornedsnorkack]

We must not forget the Coriolis effect !

Any object moving on or around the earth is affected by this, and turned slightly to the right (on the northern hemisphere). This is why we have the air rotating in low and high pressure areas. I've read that railroad tracks get worn differently due to the Coriolis effect !

Imagine there is no wind anywhere, and you start off from the North Pole and aim directly for Singapore and then maintain that (true) heading.

When you pass equator, you'll NOT be over Singapore, but somewhere further west, because the Earth has moved Singapore further east.

So any aircraft flying a long distance will have to counter the Coriolis effect by steering very slightly off the otherwise intended heading.

I wonder how much fuel is actually spent on this on e.g. a LHR to NY flight ?

(I have to admit that I've never completely understood the Coriolis effect. I understand it for north-south moving objects (rotational inertia), but not east-west.)

Well, look at it this way:

If you fly due North at something like 27 Mach or so, you experience exactly 0g and need no aerodynamic lift, because you are in orbit.
It follows that if you fly due North at 2,0 Mach, you will still experience some centrifugal force from the curvature of Earth. A small one, which covers just around 0,5 % of your weight. But it is there. Your wing only has to support 99,5 % of your weight, not 100,0 %.

Now, if you are at the equator, the force of gravity is about 0,5 % weaker than at a pole. This is partly because of centrifugal force due to the rotation of Earth, and partly because you are further away from the centre of Earth. Is that 0,5 % difference something you have to take into account for performance?

If you then fly along the Equator passing the Sun, thus flying slightly faster than the Earth rotates under you, how much lift do you need?

Chasing the Sun takes more lift than flying North, because your groundspeed cancels out the centrifugal acceleration from the rotation of Earth. And to the contrary, if you fly to meet the Sun, the rotation and your groundspeed combine to give a lot of centrifugal force...

So, you can have a Coriolis force working up or down. And if you fly east-west on higher latitudes, which are small circles, the Coriolis force will work both vertically and sidewards...

[VNAVSPD]

The distance is the same but the travel time is about an hour shorter. Aircraft cruise at very similar speeds (i.e. they don't fly any faster to get to the US) the world is rotating London to LA direction and hence it is rotating under the aircraft bringing the destination nearer to get to the UK while moving it away on the trip to the US.

What an absolute load of c£$p !!!!

Flying times can vary dramatically due to winds aloft and routing.

Jetstream winds can be in excess of 100kts. A trip that normally takes 8hrs would be much longer with a 100kt headwind.

Does it take you any longer to drive east-west than to driver west-east, assuming it's the same distance? I think you'll find the answer is NO. And please lets not go back to the aircraft on a conveyor belt saga!

[barit1]

Yes, rotation of the earth affects flight times.
Look at the flight times quoted for a trip from LA to London,
Outbound: c.10 hrs 20 mins
Return: c.11 hrs 20 mins
The distance is the same but the travel time is about an hour shorter. Aircraft cruise at very similar speeds (i.e. they don't fly any faster to get to the US) the world is rotating London to LA direction and hence it is rotating under the aircraft bringing the destination nearer to get to the UK while moving it away on the trip to the US.
...

Ummm... Errr...

Did you happen to notice the Earth turns the wrong direction for your theory to pass muster? :eek:

[DrKev]

Well spotted!! The sun appears to move east to west so the earth is in fact turning the opposite direction, i.e. west to east. According to Cool_Hand's theory, the trip from LA to London (outbound) should be longer as London keeps moving away from you!

Besides, LA to London flights don't actually travel west to east, they go closer to north-south, over the arctic.

[Cool_Hand]

Quite a few hot heads and pocket genii in here aren't there!

I know I should probably just let this die but as everyone seems to take delight in pointing out errors and jumping on band wagons I feel compelled to respond with a question.

The prevailing winds on this planet can be found here...http://en.wikipedia.org/wiki/Image:Global_Wind_Systems.jpg

(When I say great circle route in the following paragraphs I am refering to the general routes in use, not many airline routes are true great circles but they try to be close given airspace retrictions and usage)

All of the above explanations debunk my answer due to my example. Agreed for that particular route using the great circle route you would pass across the bottom of Greenland and would pretty much stay in the region of Easterlies on that picture.

Now on a flight from LA to Sydney, using the great circle route, you would pretty much stay in the region of the westerlies around the equator, Why is the flight time from Sydney to LA c.13:20 and the return trip 14:35?

According to the consistant prevailing wind crowd this timing should be reversed.

As minor points of my own defence, I never said the aircraft loses it's inertia as soon as it lifts off, as has been suggested, if I implied that the flight time to LA would be much less than 10 hours. I assume that boundary layers and inertia are heard of and understood here, the example of jumping up and down is ridiculous beyond the extreme, it is as stupid as thinking that jumping out of a moving car no matter what the speed would end up with no injury because as soon as I left it I would be stationary. Give me a break.
Jet streams on a global scale are quite narrow events, the two I can recall from the ATPL's run from Newfoundland to Scotland, and Japan to Alsaka.

Barit1, you're right about that, completely backwards in my thinking that the planet is dragging the atmosphere around it.

I'll probably not post on this thread anymore as I could well be digging a hole for myself, but the hostility isn't worth it when trying to answer a question.

[barit1]

Cool_Hand, I confirmed your ET's for the SYD-LAX route on a couple of QF flights, and I don't have a positive answer.

However, since these are BLOCK times, the long conga line for TO at LAX must be factored onto the westbound flight time, and I think that may eat up most of the difference.

I'm open to other ideas.

[BOAC]

Cool Hand - I'm sorry you have taken umbrage over the replies to your posts.

You have to expect that when people on an internet forum see that in your world the sun rises in the west and sets in the east they will respond with a 'flaming' - it is, I'm afraid, life.

You would still apppear to have east and west confused in your mind?Now on a flight from LA to Sydney, using the great circle route, you would pretty much stay in the region of the westerlies around the equator, Why is the flight time from Sydney to LA c.13:20 and the return trip 14:35?
- since the track from Sydney to LA has an easterly component, it would appear logical that that leg would be quicker with the prevailing winds you describe.

There are many other reasons why an airline would post specific block times. Barit alludes to one. Routing, cruise speeds due to fuel costs are just 2 others.

I have a feeling that this thread may be nearing its 'best before' date (in whichever time zone:) )