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Correcting Earth's Rotation For Very Long Hauls  
User currently offlinePanAm747 From United States of America, joined Feb 2004, 4242 posts, RR: 8
Posted (12 years 10 months 1 week 2 days 1 hour ago) and read 3407 times:

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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9 replies: All unread, jump to last
 
User currently offlineStaffan From , joined Dec 1969, posts, RR:
Reply 1, posted (12 years 10 months 1 week 2 days ago) and read 3328 times:

No, the atmosphere rotates along with the earth.

Staffan


User currently offlinePositive rate From Australia, joined Sep 2001, 2143 posts, RR: 1
Reply 2, posted (12 years 10 months 1 week 1 day 18 hours ago) and read 3269 times:

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

User currently offline777236ER From , joined Dec 1969, posts, RR:
Reply 3, posted (12 years 10 months 1 week 1 day 3 hours ago) and read 3204 times:

This is for those good at mechanics!!  Smile

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 Smile 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


User currently offlineRyu2 From Taiwan, joined Aug 2002, 494 posts, RR: 0
Reply 4, posted (12 years 10 months 1 week 1 day 2 hours ago) and read 3184 times:

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

User currently offline777236ER From , joined Dec 1969, posts, RR:
Reply 5, posted (12 years 10 months 1 week 1 day 2 hours ago) and read 3173 times:

 Big grin

Just pointing out how commercial a/c are affected too.


User currently offlineSkyguy11 From , joined Dec 1969, posts, RR:
Reply 6, posted (12 years 10 months 1 week 23 hours ago) and read 3147 times:

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.


User currently offlineD-AIGW From Hong Kong, joined Jul 2001, 261 posts, RR: 1
Reply 7, posted (12 years 10 months 4 days 15 hours ago) and read 3041 times:

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?


User currently offline777236ER From , joined Dec 1969, posts, RR:
Reply 8, posted (12 years 10 months 4 days 7 hours ago) and read 3010 times:

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.


User currently offlineSkyguy11 From , joined Dec 1969, posts, RR:
Reply 9, posted (12 years 10 months 3 days 16 hours ago) and read 2984 times:

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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