Facts that shocked you

[98elise]

vaud said:

98elise said:

Runways are numbered according to magnetic north (degrees then drop the last digit so 90 degrees becomes runway 9).

Sometimes it moves enough that some runways have to be renumbered.

And it s a massive pain when it happens (so many charts, etc to be updated)

It happened at Stansted in 2009.

It makes you wonder why they do it. Surely once the runway number is established just stick with that.

In fact the whole numbering system seems odd anyway. If you have parallel runways then they have the same number (with Left/Right) and of course if the runway is used in both directions then the number changes depending on which way its being used.

Probably makes sense to pilots though.

[Purosangue]

If you have two wires
and take one away
you are left with a......................... Wireless

[WH16]

98elise said:

vaud said:

98elise said:

Runways are numbered according to magnetic north (degrees then drop the last digit so 90 degrees becomes runway 9).

Sometimes it moves enough that some runways have to be renumbered.

And it s a massive pain when it happens (so many charts, etc to be updated)

It happened at Stansted in 2009.

It makes you wonder why they do it. Surely once the runway number is established just stick with that.

In fact the whole numbering system seems odd anyway. If you have parallel runways then they have the same number (with Left/Right) and of course if the runway is used in both directions then the number changes depending on which way its being used.

Probably makes sense to pilots though.

It is good for a gross error check on line up (DI Aligned, am I on the right runway, etc.) It helps with the mental math in the circuit and for re-joins (if joining on downwind, base, or overhead for example), and of course wind is reported (via ATIS) with a magnetic direction too (though true on METARs & TAFs), so you get an immediate indication of any crosswind component when building a mental picture for your approach and landing.

None of that would apply to an arbitrarily numbered runway.

[Shaoxter]

vaud said:

98elise said:

Runways are numbered according to magnetic north (degrees then drop the last digit so 90 degrees becomes runway 9).

Sometimes it moves enough that some runways have to be renumbered.

And it s a massive pain when it happens (so many charts, etc to be updated)

It happened at Stansted in 2009.

What exactly is the point of renumbering if there is already a possible rounding error of 10 degrees?

[98elise]

WH16 said:

98elise said:

vaud said:

98elise said:

Runways are numbered according to magnetic north (degrees then drop the last digit so 90 degrees becomes runway 9).

Sometimes it moves enough that some runways have to be renumbered.

And it s a massive pain when it happens (so many charts, etc to be updated)

It happened at Stansted in 2009.

It makes you wonder why they do it. Surely once the runway number is established just stick with that.

In fact the whole numbering system seems odd anyway. If you have parallel runways then they have the same number (with Left/Right) and of course if the runway is used in both directions then the number changes depending on which way its being used.

Probably makes sense to pilots though.

It is good for a gross error check on line up (DI Aligned, am I on the right runway, etc.) It helps with the mental math in the circuit and for re-joins (if joining on downwind, base, or overhead for example), and of course wind is reported (via ATIS) with a magnetic direction too (though true on METARs & TAFs), so you get an immediate indication of any crosswind component when building a mental picture for your approach and landing.

None of that would apply to an arbitrarily numbered runway.

I did assume there would be a good reason for it.

[WrekinCrew]

98elise said:

Runways are numbered according to magnetic north (degrees then drop the last digit so 90 degrees becomes runway 9).

Sometimes it moves enough that some runways have to be renumbered.

(Googles ...) north facing runways are 36 rather than 0. Could be interesting at the south pole base if they have more than one.

[48k]

98elise said:

Runways are numbered according to magnetic north (degrees then drop the last digit so 90 degrees becomes runway 9).

It would actually be runway 09

[TwigtheWonderkid]

Penny Whistle said:

Strangely Brown said:

Put them in a list in a text editor and sort the list. The 'space' is alphabetically before the 'e' and the 'y' so the statement is correct.

What do you mean? The space is not an alphabetic character; its position in any character encoding sequence is somewhat arbitrary. Your text editor sorting algorithm probably happens to use the ASCII convention, but that's not to say that no other system uses some other sequence.

Any recognised alphabetical sorting system would put the b of billion before the e of eightheen and the y of eighty. Whether you could the space as a character before any letter or you ignore it. Smith Bennett would come before Smithers or Smithy in the phone book.

[WH16]

48k said:

98elise said:

Runways are numbered according to magnetic north (degrees then drop the last digit so 90 degrees becomes runway 9).

It would actually be runway 09

Not necessarily, there are plenty of single digit runway numbers.

[Error_404_Username_not_found]

StuntmanMike said:

fooman said:

Super Sonic said:

thegreenhell said:

Which is currently opposite to normal naming convention for magnetic poles. Perhaps I should have said it's a magnetic south pole, rather than the magnetic south pole.

The Earth's polarity has flipped several times in its history, and it's currently 'upside down' by our normal convention.

The last polarity flip was 42,000 years ago when it flipped briefly, then flipped back again. The polarity is the same now as it was when naming conventions were established.

I'm surprised it moves 10 to 55 km each year as it is!

This is why you have annual change and then the degrees at the top of an ordinance survey map. You add/subtract as applicable according to the date the map was printed.

Then use when converting Grid bearing to Magnetic bearing and vica verca.

Remember, grid to mag add, mag to grid get rid.

See also: sea charts.
Compass variation noted, together with the annual change.

CDMVT "Cambridge Dons Make Virgins Tremble".

C: Compass.
D: Apply Deviation. (Ships are required to have deviation card for each compass).
M: Result - Magnetic heading/course.
V:Apply Variation (from the chart info).
T: Result - True heading/course.

(I have very little experience of OS maps, so I defer to m'learned friend above. But I am competent with navigation at sea).

[vaud]

Some of the sea charts in the Med date back a long way (not the port or coastal ones) with base data 100+ years old, IIRC

[Error_404_Username_not_found]

vaud said:

Some of the sea charts in the Med date back a long way (not the port or coastal ones) with base data 100+ years old, IIRC

You're right. It's worth checking the geodetic datum used. Most are now WGS84. (Also noted on the chart). I have some old charts dating from 1936, but correlation with GPS positions is a bit patchy to say the least.
That said I successfully navigated the Hardangerfjord under sail with a 100 year old chart in 1975. Most rocks don't move much

Maybe I was just lucky.

[WH16]

Error_404_Username_not_found said:

vaud said:

Some of the sea charts in the Med date back a long way (not the port or coastal ones) with base data 100+ years old, IIRC

You're right. It's worth checking the geodetic datum used. Most are now WGS84. (Also noted on the chart). I have some old charts dating from 1936, but correlation with GPS positions is a bit patchy to say the least.
That said I successfully navigated the Hardangerfjord under sail with a 100 year old chart in 1975. Most rocks don't move much

Maybe I was just lucky.

I've had to resort to Google Earth imagery to spot coral heads on some Pacific atolls, the Admiralty charts there are equally ancient and unreliable.

[Johnspex]

Purosangue said:

If you have two wires
and take one away
you are left with a......................... Wireless

Actually it's "a wire fewer" but that's not funny.

[miniman]

Roofless Toothless said:

I m just watching the snooker. Mark Williams is playing.

The brown ball has gone on an unexpected trip right down to the other end of the table and was sitting amongst a group of reds. The referee pointed a white gloved finger at the ball and declared brown .

Why is he doing that? I wondered. Apparently, Williams is colour blind and can t tell the difference between the brown and red balls, so the referee helps him out.

For a particularly challenging shot where it’s not totally obvious which colour the player is aiming for, they have to nominate it so there’s no doubt. The ref calls out which ball was nominated.

[Cabbage Patch]

Roofless Toothless said:

I m just watching the snooker. Mark Williams is playing.

The brown ball has gone on an unexpected trip right down to the other end of the table and was sitting amongst a group of reds. The referee pointed a white gloved finger at the ball and declared brown .

Why is he doing that? I wondered. Apparently, Williams is colour blind and can t tell the difference between the brown and red balls, so the referee helps him out.

I’m colour blind and can’t tell the difference between red and brown when watching the snooker. Watching the Williams / Allen match on tv I thought it was nice of the referee to point it out for me. That’s usually my wife’s job!

[Rusty Old-Banger]

Cabbage Patch said:

Roofless Toothless said:

I m just watching the snooker. Mark Williams is playing.

The brown ball has gone on an unexpected trip right down to the other end of the table and was sitting amongst a group of reds. The referee pointed a white gloved finger at the ball and declared brown .

Why is he doing that? I wondered. Apparently, Williams is colour blind and can t tell the difference between the brown and red balls, so the referee helps him out.

I m colour blind and can t tell the difference between red and brown when watching the snooker. Watching the Williams / Allen match on tv I thought it was nice of the referee to point it out for me. That s usually my wife s job!

"For those watching in black and white, the pink is next to the green."

[Roofless Toothless]

It comes awfully close to outside assistance, though, doesn't it?

I wonder if opponents ever object to it?

[Pit Pony]

Doofus said:

The Muppet Show is British, not American.

Despite the government of the UK showing much muppetry going back decades, the USA looks like k e it's looking to take ownership permanently.

[48k]

WH16 said:

48k said:

98elise said:

Runways are numbered according to magnetic north (degrees then drop the last digit so 90 degrees becomes runway 9).

It would actually be runway 09

Not necessarily, there are plenty of single digit runway numbers.

Fair cop. The ICAO Standard (global standard except the USA) is for two digit runway numbers. The FAA regulations allow for single digit runway numbers.

Edited by 48k on Tuesday 13th January 12:41