Is Plane lighter going west than going east?

[sansbury]

Is Plane lighter going west than going east?
I would expect a plane to be lighter after subtracting out wind velocity and centrifugal force effects, when going westward than when it is going eastward. It may be that the centrifugal and centripetal effect in the opposite direction conceals this but perhaps the computer collection of data on an airplane might reveal it??
I assume measurements of wind velocity can be constantly recorded by a computer on the plane so that it would be easy to tell what part of the also recorded lift is due to the wind velocity and what is due to some other factors including the centrifugal force etc..
By centrifugal force etc I mean that when the plane takes off in the direction the earth is spinning its total velocity would be this roughly (.465)cos(lat)km per second plus the velocity of the plane etc and in so far as this exceeds v where v^2/r=(6.6)(10^-11)mM/mr^2 about there should be a tendency to follow an elliptical orbit than a purely circular orbit etc which would in effect add to the lift. The reverse effect also precisely calculable, would occur in going in the westward direction.
Are such calculations made and such measurements stored and if so what do they show?

[Redback]

Pull back, go up. Push forward, go down.

Interesting question but.... yikes! :eek:

[Mr McGoo]

It's the other way round! An aircraft's apparent weight (mass always remain's the same) is less when travelling east. The effect is maximum when heading 090°T at the equator. (That's why space vehicle launch sites are close to the equator and they launch heading in an easterly direction!) Anyway for an aircraft travelling east at the equator at 500 KTAS the apparent weight reduction is about 0.9% At a speed of 1200 KTAS (Concorde) the weight reduction is 1.9%.

If you want a longer technical answer (High School Physics type equations) then e-mail me.

[Squawk 8888]

Right you are about the weight thingy McGoo, but that's not why tropical locations are used for launches. The big advantage is not the weight reduction, it's the fact that the earth's rotation gives the ship a running start on its way to orbital velocity. At the equator you're already moving at roughly .25 miles per second, which can reduce the acceleration needed by as much as 5% depending on the desired orbit. Conversely, for a polar-orbit spy or weather satellite that covers a different longitude on each pass the best spaceports are the ones closer to the poles (such as Churchill, Manitoba) because there's less need to push against the earth's rotation.

[Mr McGoo]

Squawk 8888, I certainly do not want to get in a pissing contest with you, but we are in fact both right about launch pads on the equator. It's a circular argument (chicken and egg stuff). You've looked at from an egg's perspective, I'm from the chicken's.

Weight reduction is caused by centripetal acceleration wrt inertial space opposing earth's gravitational pull. When centripetal acceleration equals earth's gravitational acceleration then weight equals zero and an object is in orbit around the earth. So from a 'chickens' point of view to put an object in orbit we need to reduce its apparent weight to zero.

However from an 'eggs' point of view to put an object in orbit you have to increase its velocity to the escape velocity. This turns out to be the velocity where centripetal acceleration wrt inertial space equals gravitional acceleration.

So both things go hand in hand. Weight reduction occurs as orbital velocity wrt inertial space increases. And launching near the equator in an easterly direction gives both a head start due to the rotation of the earth.

[go with the flow]

There's another reason too. Remember that the earth isn't round, rather flattened at the pole and wider at the middle, presumably from when it was soggier.

Thus at the equator one's already in a slightly reuced gravitational field irrespective of the extra decrease in apparent weight due to the increase in the centrifugal force travelling east.

Any other factors anybody know about?
:)

[sansbury]

Appreciate the answers you are giving but they were given at least mathematically as part of my question: The latitude effect and the moving with the spin or against the spin of the earth.
Yes, the plane given these effects only would appear lighter going eastward but the question is, after these effects are subtracted would the plane be lighter going westward? Has this ever been calculated?
Are computers on some planes measuring wind velocity and the tendency of the plane to go in a wider(eastward) or lesser(westward) elliptical orbit instead of the circular orbit parallel to the surface of the earth etc..?

[SOPS]

why?

[faq]

I often wondered, if 300 plus charter pax got on a transatlantic flight, had snacks, lunch, then afternoon tea and regularly went to the toilet (including a visit for 'solids'), would the aircraft's zero fuel weight be more at the end of the flight than at the beginning?

[Open Climb]

Thank you faq, I was starting to feel like a complete idiot.. :D :D Solids should definitely be taken into consideration.

[Squawk 8888]

Actually, faq, the zero fuel weight on landing will be the difference between (a) the total weight of pax + food at takeoff; and (b) the matter that was converted to energy by the pax from the effort of getting up to use the toilet, reading and flirting with the hosties. The old standby E=MCwhatever thingy that Einstein fella came up with will help you with the sums on that.

[Vmu]

Another effect that gets way too little attention during ground school is the momentum of photons from the sun; I would expect total drag to be slightly higher when flying into sun, than away from it. When I think about it the drag would also be higher with the sun above the A/C, as the wings would have to produce more lift and hence operate at a (slightly) higher AoA.

:D :D :D

[sansbury]

The questions of light pressure and other effects and their magnitudes and ways of measuring them might have no practical value in flying a plane but maybe there is some test plane out there that could make such information available to confirm the basic physics assumed.???
One effect of the spin of the earth on the velocity of a plane moving eastward or westward is that the velocity of the plane in the two cases differs from that required by the assumed gravitational effect of the earth if the plane is move in a circular path parallel to the surface of the earth.
That is basic physics says that this velocity of the plane squared divided by its distance from the center of the earth must equal the gravitational force between the earth mass and plane mass divided by the product of this distance squared times the plane mass.
If the the velocity is greater than this required velocity the plane will start to move higher than the required circular path (parallel to the curvature of the earth)and if less;lower than the required circular path requiring an adjusment of the flaps etc to decrease or increase the lift.
Is it possible to measure such adjustments and compare them to what adjusments are predicted given this requirement and given other influences like the wind velocities, light pressure maybe etc?

[ShyTorque]

Is this why air tickets are cheaper in some countries than others?

As a follow on from Vmu's post - Do dark coloured aircraft have less drag then light coloured ones because they absorb photons and do they get heavier in bright sunlight?

And do some pilots wear odd socks if there is an R in the month?

Strewth chaps! This is getting too technical to be practical, if you get my drift. It certainly doesn't affect the price of fish!

:eek: We've been invaded by mathematicians!

[ 25 August 2001: Message edited by: ShyTorque ]

[Mr McGoo]

Hey ShyTorque,
Just remember that it was a member of a family of famous mathematicians that developed the laws of fluid dynamics, that enable engineers to build machines, that enable mere pilots to perform gravity defying acts such as fly in the air. That mathematician was of course Daniel Bernoulli.
:)

[jtr]

A while ago a similar topic was discussed, so one day I punched the info into the sec flt pln on the 340. Did a super long sector, at the equator, identical conditions for both. Fuel required came up at 100 kg more going from W to E than vv. Tried it in a few different ways. Always 100 kg more.

See how much fun long haul can be! :rolleyes:

[ShyTorque]

Mr McGoo,

So nothing flew before this mathematician called Bernoulli did his stuff? Are you sure that the birds hadn't already got it sorted a few million years previously?

I think you will find Mr. B got in on the act quite late on, all things considered :rolleyes:

ShyT

[Mr McGoo]

Ah but as far as humans go having a mathematician involved has put us in the air a lot lot quicker than waiting a few million years for evolution to give us hollow bones and feathers. ;)

[Lurk R]

ShyTorque - I was always told that red cars go faster!!! :D

[sansbury]

jtr
This is very interesting- that the plane traveling the same distance W to E used 100kg more fuel than E to W and that the this was confirmed on two or more occassions.(what was the distance, speed and altitude?)
As has been mentioned, the plane taking off going from west to east would have more apparent lift and lightness than vice versa because of the speed imparted by the spin of theuu earth.
I am told that atmospheric conditions winds etc are usually the dominant factor but if your test had the same general atmospheric conditions, then there is apparently some other factor here than atmospheric conditions or the effect of the spin of the earth on the initial velocity of the plane.
What would you say to the argument that your result was due to atmospheric conditions?

[LAN]

...and don't forget the increase in mass due to aircrafts velocity in the Earths gravitational field. However, the E=W+Mc2 sh*t first really kicks in at speeds appraocing 60% of lightspeed, so no great operational concern :D

Concerning the particle / photon thread : would this mean that the aircraft would need to produce more lift during high altitude / high lattitude flight due to increased cosmic radiation level :confused:

And finally : Raising the cabin temperature would tend to expand the airframe, thus increasing form drag (and possibly friction drag due to expanding gaps in the airframe). So should complaints about low cabin temperature be answered by a curt: "You want to arrive on time, don't you, Sir"? :D

Now I cannot dream up any more variables affecting aircraft performance for the fly-f***ing department to consider - might as well go to sleep :D

[White Knight]

Does this all mean that we need to recalculate and rebug landing weights when turning from downwind to final on an east/west runway ???
Strewth, it's getting very technical... :D :D :D

[Back Seat Driver]

Travelling east does reduce your effective weight, and after a long sequence of confusing mathematics it seems to cause a loaded 747 to effectivly weigh 99.7% of its actual weight. On the flights we do across the Pacific pond easterly from ozland to usland that equates to very roughly 1.2 tonnes of fuel, and that IS a lot of fish.

edited for typos.

[ 08 September 2001: Message edited by: Back Seat Driver ]

[ShyTorque]

Ivan,

The expansion drag increase of the airframe is somewhat nullified by the fact that warmer air is lighter, reducing the all up mass and therefore allowing a reduction in angle of attack. Additionally, passengers travelling from further west are generally warmer when they board the aircraft so the fuel used to heat the cabin is also reduced, so this needs to be allowed for.

This thread has made me realise after 25 years of professional flying that I was never cut out to be a pilot.

How on earth are we supposed to calculate our fuel load these days? What we actually need are some mathematicians to sit up front..

"Captain to F/O, you have control - of the calulator. Quick, work out how much nose up I need to stop this rate of descent - what do you mean the batteries are flat? :eek:"

Excuse me while I nip out to fill up my car with petrol. Anyone give me guidance on how much to put in for the coming week? :D

[sansbury]

Let me repeat again, if it is not the wind then this would be a very very interesting result.
Have the wind effects been subtracted out? Is this what was meant by the same conditions?
And how does one do this? Does one have accurate enough readings of doppler radar reflections from flying dust showing wind velocity relative to the ground at various altitudes where the plane is flying etc..?
Is it possible to say that repeated trips indicating more fuel used going west to east the same distance could not be accounted for by some systematic wind effects given the 200kg difference in fuel for the same specific distance?

[blueball]

Depends on which planet you are on!