View Full Version : East to West versus West to East influences?

12th Aug 2001, 22:34
Are there any differences in the steering of a plane eg a Concorde, when you are going from Europe to America versus America to Europe, particularly when you are going due west versus due east?
If there are any such differences, what are they attributable to? eg the winds and lift, the spin of the earth as you are taking off etc?

16th Aug 2001, 07:37
coriolis effect means that a free moving body will always apparently turn to the right in the northern hemisphere. The effect is caused by the earth turning beneath it. Amazingly the apparent turn is always rightwards, whichever direction the aircraft or other body is flying. It is also negligible

16th Aug 2001, 18:26
I was looking for some other effect that again might be negligibly different from the effect of average wind speed and direction on the lift of the airplane, but which could be determined from automated recording of these values by the computers on the plane.
That is, I would expect the plane moving eastward against the prevailing winds would be lifted on average more than a plane moving westward but that there is some other influence that has the opposite effect.
Is this observed or measured?

16th Aug 2001, 20:16
Once an aircraft is established in an airmass, the lift provided by the wings is relative to its speed in that airmass. That means that it doesn't matter which way the air is moving (ground talk = which way the wind is blowing) when you are thinking about the amount of lift is provided by the wings.

For Example: an aircraft flying into the wind at an indicated speed of 100 knots reacts in the same way as an aircraft flying with the wind at 100 knots, so aircraft travelling East or West have the same lift.

One minor change is that aircraft travelling East are travelling with the Earth's rotation, while aircraft travelling West are travelling against the Earth's rotation. Aircraft travelling East therefore have a greater centrifical effect, and thus the wings support a tiny fraction less weight.

17th Aug 2001, 22:33
Understood. From other considerations having nothing to do with wind velocity or centrifugal or centripetal force, I would expect the plane to be lighter after subtracting out these 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 gather measurements of wind velocity might 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..
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 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 what do they show?