777236ER From , joined Dec 1969, posts, RR:
Reply 3, posted (14 years 4 months 1 week 2 days 14 hours ago) and read 4129 times:
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.
Skyguy11 From , joined Dec 1969, posts, RR:
Reply 6, posted (14 years 4 months 1 week 2 days 11 hours ago) and read 4072 times:
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 From Hong Kong, joined Jul 2001, 261 posts, RR: 1
Reply 7, posted (14 years 4 months 6 days 3 hours ago) and read 3966 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?