NAT Separation

[Flamin_Squirrel]

Was on a flight over the Atlantic yesterday, and was surprised when I looked out the window to see we were overtaking another aircraft at the same level. From my understanding, either 1,000ft or 60Nm separation is required when on a NAT which we didn't seem to have?!

Have the rules changed?

Thanks.

[BOAC]

and was surprised when I looked out the windowWas your TCAS u/s? T'other a/c might be telling porkies to Oceanic, of course, or just screwed up.

[Flamin_Squirrel]

I'm just lowly SLF so no idea if TCAS was functional. Maybe someone's new years resolution will be to find a new line of work!

[Hartington]

Documents (http://www.paris.icao.int/documents_open/show_file.php?id=243)

Appears to be the latest specification issued by ICAO.

[Tarq57]

You will be even more surprised the first time you see one from the flight deck on an exact reciprocal track pass 1000' above.
(So I'm reliably informed.)

[Flamin_Squirrel]

You will be surprised at what looks like an aircraft at the same level as you but in reality is actually 1000' above or below.

Yeah I was wondering if that was the case. I took a pic , but can't post it until I get back to the UK.

That leads me to another question though, the other aircraft was offset a mile or two - why would it have been if it was on the same track?

[ab33t]

It is a scary sight from the cockpit , I even find myself wanting to duck

[Liobian]

FS - Given the track-keeping accuracy of current nav systems, it is now accepted practice for NAT tfc to fly offset by a mile or two, if they so choose. This allows them to avoid the wake turbulence generated by an a/c flying a few thousand feet above, on the same track, and introduces a degree of lateral separation should another a/c happen to be (erroneously) at the same level - possibly opposite direction. Allied to TCAS, it's a belt-and -braces approach.