Does the plane REALLY take off? It depends.

[igor_kavinski]

I have an equally confusing question.

Suppose a helicopter is hovering over a certain spot, several hundred feet above it. We also know that the Earth is spinning. If the pilot locks the helicopter to a fixed set of xyz coordinates, will the spot marked a huge X below move away from under the helicopter? Or does the Earth's gravity take the helicopter along for the ride as it spins so 24 hours later, the helicopter is still above the X spot?

 

[IronWing]

Those coordinates are relative to a reference frame. If the reference frame is the earth's surface then the helicopter will move with the earth's rotation. If the reference frame is something else, then the helicopter will move relative to the earth's surface. Make the reference frame relative to the sun, for example, and the helicopter flys off into space or smashes into the ground as the earth moves.

 

[igor_kavinski]

That reference frame thingy is confusing. What do you mean, make the reference frame relative to the sun? How would one do that? Also, the helicopter moving with the Earth seems kinda counter intuitive, unless the atmosphere it's in is moving with the Earth too so the atmosphere is propelling the helicopter forward? If that helicopter were to go all the way up to space with no air molecules (100 KM high), does that mean the helicopter would no longer be in the Earth's frame of reference?

This is what I don't get: if the coordinates are locked relative to the Earth's surface and the pilot closes his eyes for a few hours and just makes sure that the helicopter hovers without moving forward or backward and then opens his eyes, will he find the helicopter drifted away from those locked coordinates?

 

[[DHT]Osiris]

I have an equally confusing question.

Suppose a helicopter is hovering over a certain spot, several hundred feet above it. We also know that the Earth is spinning. If the pilot locks the helicopter to a fixed set of xyz coordinates, will the spot marked a huge X below move away from under the helicopter? Or does the Earth's gravity take the helicopter along for the ride as it spins so 24 hours later, the helicopter is still above the X spot?

A helicopter has to work to stay in a spot, given things like wind. If it's going to stay at an xyz spot, it's going to do so intentionally so yes, it'll always be in that spot as long as it's trying to.

 

[igor_kavinski]

OK, let's replace the helicopter with a helium filled balloon on a non-windy day. It goes straight up. Is its upward motion going to be an exact straight line or is it gonna drift a bit coz the Earth moves away from below it?

 

[sandorski]

The Helicopter becomes Space Junk.

 

[sdifox]

Yeah I included a caveat for VTOL up above.

If a plane can takeoff vertically, ie without depending on the lift from the wings, it can take off horizontally with the wings.

 

[igor_kavinski]

The Helicopter becomes Space Junk.

Damn, if only Carmack's idea of a universal world simulation engine had not been vetoed by his peers at ID software. We could run this simulation in that engine NOW to find the answer for ourselves.

 

[[DHT]Osiris]

OK, let's replace the helicopter with a helium filled balloon on a non-windy day. It goes straight up. Is its upward motion going to be an exact straight line or is it gonna drift a bit coz the Earth moves away from below it?

In a vacuum? It'll go up, with the angular velocity of the rotation of the body, plus the orbital velocity of the body. In an atmosphere? Include drag, plus wind. 'direction' and 'location' become kinda fuzzy when you get into orbital mechanics.

If a plane can takeoff vertically, ie without depending on the lift from the wings, it can take off horizontally with the wings.

Not without lift it can't. If you provide your own lift at zero velocity you're either a rocket or a helicopter. Or mimicking one of the two.