OT Don't quite see how this'll work???

[whisky-dave]

Yes I know.

Yep.

[bert]

In article , "Dave Plowman (News)" writes

Well gravity certainly always seem to work downhill around here. What a thicko.

Do try not to make yourself look so stupid. It's painful to see in a grown man/woman. (Musn't make gender assumptions).

[Dave Plowman (News)]

Can you then explain how it works to make moving something uphill the same as on the level, then? I'm sorry there are words with more than four letters.

Is that a 'don't do as I do' type of thing?

[Vir Campestris]

The bottle neck is the runways at the airport. That's why Heathrow wants to build a new one.

Allowing free choice of routes is for fuel savings. The economical cruise altitude rises as the plane gets lighter, so they want to climb gently all the way across the ocean.

Andy

[whisky-dave]

Not all planes fly to heathrow.

No it isn't.

But they don't do that. They don't take the shortest route from A-B they take a route where they can be tracked. Friend flew from gatwick to cacun on tuesday explan why they didn't just fly directly across the ocean

[The Natural Philosopher]

Great circle

Largely it takes you over greenland labrador and down the E coast of the USA

[Bob Eager]

You don't really understand map projections, do you?

[Tim Streater]

Am I missing something here? Is the inebriated one referring to Cancun (Yucatan peninsular, Mexico)? If so, a great circle route would appear to take one across the Atlantic and down the East US coast, across the tip of Florida to Cancun.

[whisky-dave]

Why doesn't it just go across directly then that would be a shorter distance less fuel quicker flight ?

It could go across cornwall but it doesn't it heads North to greenland.

[whisky-dave]

So explain it if you understand it better.

[Roger Hayter]

theere can be more routes.

The direct route looks remarkably curved on a Mercator (or similar) projection. Most planes flying a long way fly on a great circle route, perhaps slightly altered to be near enough to alternative airports should an engine fail. Especially since they often only have two.

[charles]

Find a globe of the world and find the shortest route using bits of string. Mercator's projection of the world onto a rectangular map doesn't do shortest routes.

[Bob Eager]

He is. It's useless explaining to him, though.

[whisky-dave]

why not take the What's your drinking nationality...

Take the which If so, a great circle route would appear

you mean you can't explain why the aircraft 'hugs' the cost and has to stay in a particular corridors . Can you explain why it's important for an aircraft to be on radar so that other planes know where you are at a point in time and space ?

[Tim Streater]

Righto, ta :-)

[Roger Hayter]

Because it isn't true. Nowadays commercial planes have transponders which talk to each other (hence the name), anyway.

[whisky-dave]

Did you get that from the TV a week or so ago, most airports still rely on radar NOT GPS.

Air traffic control ATC uses radar NOT GPS.

All commercial aircraft are equipped with transponders (an abbreviation of "transmitter responder"), which automatically transmit a unique four-digit code when they receive a radio signal sent by radar.

These transponders use RADAR NOT GPS.

google it. do airlines use GPS or radar

Yes, but while GPS (Global Positioning System) is a staple of modern life, the world's air traffic control network is still almost entirely radar-base d. Aircraft use GPS to show pilots their position on a map, but this data i s not usually shared with air traffic control.

of course things are improving but it's the airports that have to upgrade t here;s only 3 that currently have full GPS in use, the most recent being lo ndon city airport another I think is Brussels.

In Europe GPS approach aids are still limited to a very limited number of a irports and have not yet been widely adapted, despite pilots much preferrin g them over traditional and inaccurate ground based approach procedures.

[The Natural Philosopher]

That is the shortest distance. That is going across directly.

Buy yourself a globe and a bit of string and measure it

[Tim Streater]

The great circle route I described is the shortest one.

[Terry Casey]

Because, as you've already been told, it flies the Great Circle route. You are used to flat maps that are centred at a point on the equator but the earth isn't flat.

A Geat Circle map shows the earth as viewed fom a apecific poin on the globe. If you draw a straight line - ie: the shortest route - on a Great Circle map you will find that is doesn't follow what appears to be (but isn'!) the most direct route on a 'normal' map.

This is a Great Circle map:

It is actually centred on a point in County Leitrim, Ulster but is close enough to Gatwick, at this scale, to illustrate the point. Draw a straight line on the map from Gatwick to Cacun and see where it goes ...