Navigation Lights

[I_know_nothing]

This just occurred to me as I saw a jet airliner pass overhead in the dark. The Green and Red Nav lights were clearly visible as it approached, but not after it passed over - then all I could see were the anti collision strobes and a single white tail light.

I've always taken the nav lights for granted - I know they help distinguish port from starboard on a plane in the air - but what practical use are they? What real purpose (if any) do they serve - or are they really just an anachronism?

[Rainboe]

The red and green lights are seen from dead ahead to 110 degrees either side. The white rear lights through the rear 140 degree arc. They are absolutely vital! You can tell at a glance which way a plane is facing, whether it is coming towards you and whether it is left to right or right to left. The colour of the light also guides you on who has right of way. If you see a red, give way, a green- you have right of way. Just like ships. The rules of the air are just the same as the rules of the sea. We have trouble with 'I am conducting diving operations- keep clear' though.

[lurkio]

If you can see all three where is he in relation to you?

[T6NL]

Directly above or below you!

[BOAC]

are they really just an anachronism

in modern controlled airspace, with TCAS and radar control, yes. They do, however, provide a safe and reliable backup there and are essential outside.

[I_know_nothing]

Thanks all for the speedy and helpful replies.