747-600X
Topic Author
Posts: 2503
Joined: Wed Jan 05, 2000 3:11 am

### Runway Numbering... Argh!

Well... runway numbers are, apparently, based on the direction (in degrees) that the runway faces. So... what's zero? Due North? Okay... is it True North or Magnetic North? At Kansai International, a huge plan of which is hanging in front of me at this moment, the runway is at a precise 51-degree angle to True North, so you'd think that it would be numbered 05, given that only the first 2 digits of the three-(possible)-digit number are used. But no, it's actually 06. I assume that this is because the runway is at a 57-degree, 46-minute, 42-second angle to Magnetic North, which makes one wonder why they aligned it perfectly at 51-degrees with True North. Anyway... can someone please explain how exactly runways are numbered?

Av8trxx
Posts: 632
Joined: Sun Nov 11, 2001 7:08 am

### RE: Runway Numbering... Argh!

Runway numbers are taken from a compass heading, so they are all in magnetic, not true. 057 degrees rounds to 060, so that's why its Rwy 6. All runway numbers are rounded to their nearest 10 degree interval (to keep things simple I bet). True, north is zero, but 360 or Runway 36 is used. If it were at 005 degrees, I guess they could go either way, 360-Rwy 36 or 010-Rwy 10.

747-600X
Topic Author
Posts: 2503
Joined: Wed Jan 05, 2000 3:11 am

### RE: Runway Numbering... Argh!

Okay, so my next question is - how do you find Magnetic North on a computer? Let's say you're designing an airport for France here in the USA... how do you know what angle to put it at without flying over there, pulling out the ol' compass, hoping you're standing at the right angle, and shooting?

Hamfist
Posts: 606
Joined: Wed Jan 30, 2002 9:40 am

### RE: Runway Numbering... Argh!

If memory serves me correct, from a brief intro to TERPS that I received, there may be a magnetic correction that is part of the determination.

Cessnapimp
Posts: 1245
Joined: Sun Oct 07, 2001 11:46 am

### RE: Runway Numbering... Argh!

In Canada,the airspace is divided in two as far as rwy orientation is concerned: We have the Southern Domestic airspace, and Northern domestic airspace. They split pretty much equally in the middle (longitudinally, of course) of the country. In the southern domestic airspace, the rwy numbers are in reference to the magnetic north: North would be rwy 36,181 degs would be rwy 18 etc...

Moving north of the country, magnetic variation lines (isogonic lines for you fancy shmancy people) behave errradically because you are getting close to the magnetic pole. This phenomena, known as "magnetic dip" causes the compass to behave erradically since you are beginning to overfly nature's big ass magnet. Therefore this zone up North requires all headings (including rwy orientation) to be in reference to the true north.

Hope this helps!

Grégoire

747-600X
Topic Author
Posts: 2503
Joined: Wed Jan 05, 2000 3:11 am

### RE: Runway Numbering... Argh!

Next question - are the degrees taken clockwise or counterclockwise? If a runway points due North, it's 36, so if its 60 degrees to the left, is that Runway 30 (300 deg.) or runway 06 (60 deg.)??? I was under the assumption that the degrees always went counterclockwise, such that it would be Runway 06. Anyone know for sure?

Staffan
Posts: 3879
Joined: Tue Mar 18, 2008 9:21 am

### RE: Runway Numbering... Argh!

The degrees go clockwise, north is 0/360, east is 90, south is 180, west is 270.

NZ767
Posts: 1553
Joined: Sun Nov 18, 2001 9:17 am

### RE: Runway Numbering... Argh!

Talk about complicating a simple matter here.
Runway numbers are assigned according to the direction that they lie in relation to magnetic north rounded to the nearest tenth with the last digit dropped.
This is generally worldwide with the Canadian exception above; there may be others, eg: Antarctica could possibly follow the Canadian example (the other way around obviously) as regards the South Magnetic Pole.

timz
Posts: 6318
Joined: Fri Sep 17, 1999 7:43 am

### RE: Runway Numbering... Argh!

http://www.worldaerodata.com gives the difference betw magnetic and true at its hundreds (thousands?) of world airports.

747-600X
Topic Author
Posts: 2503
Joined: Wed Jan 05, 2000 3:11 am

### RE: Runway Numbering... Argh!

Worldaerodata seems only to provide the True headings.

747-600X
Topic Author
Posts: 2503
Joined: Wed Jan 05, 2000 3:11 am

### RE: Runway Numbering... Argh!

Sorry, I was looking under the runway information. The basic airport info. does include a "magnetic variation".

jhooper
Posts: 5561
Joined: Thu Dec 13, 2001 8:27 pm

### RE: Runway Numbering... Argh!

It's interesting to note that sometimes airports renumber their runways. For example, RWY 14L/14R at Houston Intercontinental is now 15L/15R. The magnetic variation changes slowly over time.
Last year 1,944 New Yorkers saw something and said something.

Skymonster
Posts: 3428
Joined: Fri Oct 12, 2001 7:53 pm

### RE: Runway Numbering... Argh!

It would be crazy to number runways anything other than in respect of magnetic north (with the exceptions mentioned previously). One of the basic checks that should be made before take off is: is the compass heading the same as the runway - its one of the ways of confirming you're on the right runway. Use anything other than magnetic and this basic safety check isn't possible.

A
There are old pilots and there are bold pilots, but there are no old bold pilots

BWIrwy4
Posts: 877
Joined: Thu Nov 15, 2001 1:41 pm

### RE: Runway Numbering... Argh!

Kirstey
Posts: 102
Joined: Fri Nov 16, 2001 8:56 pm

### RE: Runway Numbering... Argh!

>Use anything other than magnetic and this basic safety check isn't possible

Of course Skymonster - you could use the great big white numbers on the Threshold!!!!

Alignment is based on Magnetic, because short of chucking it out of the window the compass is the only 100% reliable instrument on an aircraft. Everything else can go "Pete Tong" on a plane, the compass and the earths magnetic field will be fine!

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