PanAm747
Topic Author
Posts: 4713
Joined: Mon Mar 01, 2004 4:46 am

### Correcting Earth's Rotation For Very Long Hauls

In the flight plan do they have to correct for the Earth's rotation?

Like when they plan HKG-EWR, do they have to "aim" for where New York City will be 14 hours later?
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Staffan
Posts: 3879
Joined: Tue Mar 18, 2008 9:21 am

### RE: Correcting Earth's Rotation For Very Long Hauls

No, the atmosphere rotates along with the earth.

Staffan

POSITIVE RATE
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Joined: Sun Sep 16, 2001 11:31 am

### RE: Correcting Earth's Rotation For Very Long Hauls

LOL imagine if the atmosphere didn't rotate with the Earth we would have a permanent 3,000 MPH gale blowing

777236ER
Posts: 12213
Joined: Sat Aug 18, 2001 7:10 am

### For All Ya Mechanics Buffs

This is for those good at mechanics!!

Did you realise that an aircraft flying WITH the rotation of the earth will require slightly less lift than an aircraft flying AGAINST the rotation of the earth?

If an aircraft were to fly with the rotation of the earth, a very small centripetal force is present. It's very small, but it's there nontheless. If an aircraft were to fly AGAINST the rotation of the earth this centripetal force wouldn't be required. Nifty, eh? This centripetal force doesn't come to much (about 400N when the mass of the a/c is 10 tonnes) but it's a significant and interesting principle.

Remember also, if a plane were to fly with a velocity (a pre-requisite. duh.) WITH the rotation of the earth, the centripetal force is dependant on the square of the velocity, so this 400N can quickly escalate.

This doesn't really affect commercial aircraft, but it's interesting to think that if you reach a fast enough speed, the centripetal force will equal the weight of the a/c  The a/c is now traveling at the circular velocity of the earth, and doesn't need any lift from the wings

Of course, you'd have to go about 30000 km/h for a 10 tonne a/c at ground level, which is slightly probelmatic, but it's an interesting principle, nevertheless.

Impress your mechanics teacher with THAT
Your bone's got a little machine

ryu2
Posts: 1549
Joined: Tue Aug 06, 2002 8:18 am

### RE: Correcting Earth's Rotation For Very Long Hauls

In other words -- it's orbiting the Earth!

777236ER
Posts: 12213
Joined: Sat Aug 18, 2001 7:10 am

### RE: Correcting Earth's Rotation For Very Long Hauls

Just pointing out how commercial a/c are affected too.
Your bone's got a little machine

SkyGuy11
Posts: 532
Joined: Fri Oct 26, 2001 7:09 am

### RE: Correcting Earth's Rotation For Very Long Hauls

77236ER:
Such a machine would not be a plane at all, but a satellite orbiting the Earth. They are in free fall (accelerating toward the earth's surface), but the centrifugal force created by the Earth is just enough to prevent the satellite from losing altitude.

It's not like gravity does not affect satellites, it's just that the gravity keeps them from leaving Earth orbit.
.

D-AIGW
Posts: 258
Joined: Thu Jul 05, 2001 4:57 pm

### RE: Correcting Earth's Rotation For Very Long Hauls

Skyguy11 - a centrifugal force is a virtual force. This means that it does not really exist, but you feel it due to your own inertia. Gravity DOES affect satellites by keeping them from flying off their orbits.

But is it true that at the higher layers of air, the atmosphere doesn't rotate as fast as it does near the ground? I don't know about the friction, inertia and gravity issues for that one... ah well, is that called headwinds and tailwinds, and are already taken into account in flight planning?

777236ER
Posts: 12213
Joined: Sat Aug 18, 2001 7:10 am

### RE: Correcting Earth's Rotation For Very Long Hauls

Skyguy -- read D-AIGW's post on centrifugal force.

If you read my post, i'm pointing out that principles that affect orbiting bodies also affect (to a lessor extent, due to the speed) commercial aircraft.
Your bone's got a little machine

SkyGuy11
Posts: 532
Joined: Fri Oct 26, 2001 7:09 am

### RE: Correcting Earth's Rotation For Very Long Hauls

Um.... you guys might want to reread my post a little more carefully, especially the last sentence (my wordings a bit off, sorry for the confusion). I'm basically agreeing with you!
.

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