# Why Airport Runways Have Two Numbers, One Always 18 Less Than The Other

Submitted by: squrlz4ever 2 months ago in
13

This may be the most interesting bit of trivia you learn today.
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Male 1,975
Thanks for this, Squrlz. I fly a bit with my job (passenger, not pilot...), and I've always wondered what the runway designations meant. Especially the part where I would see a runway marked "36R/18L". I always assumed that the "R" and "L" were "right" and "left", but didn't know for sure, and never made the 36 as 360 and 18 as 180 connection. Good to know!
Male 433
For those who don't like watching videos, they are "talking" about compass directions and one is offset by 180 degrees. The last digit is not painted. This whole text is smaller than the video screen ...
Male 8,777
The numbers at the end of the runways represent the compass heading you are flying in order to line up with the runway. The numbers on opposite ends are the reciprocal of each other.  Numbers change over time due to fluctuations in magnetic north.

There, explained in 10 seconds what the video took two minute to.
Male 5,413
megrendel Hmm. I don't think two minutes was too long to explain this. If it was 10 minutes, sure, but two?
Male 765
Nice squrlz4ever! I learned something

Now scheckydamon, clearly video maker is a millenial tool trying to show off! Can you explain this:

"The first number uses the actual compass bearing" - The thing about that is, there are always two "actual" bearings! Is it just closest to North (0) first?

What happens if it is perfectly E-W ?

Thirdly: Left, Center, Right? O.o That is the oddest thing!. I just assumed that there would be no subjective references in this type of application.

Male 1,512
stifler North runways are 36 East/West are 09/27 Charlotte recently added a new runway and it has gone to the L,C,R designator. There aren’t many like this and it generally will be a huge airpor with parrallel runways. 4 I know of are O’Hare in Chicago, Charlotte, Orlando and Atlanta. Keep in mind the when airports are designed that they try to put thr runways along the path of prevailing winds to assist with takeoffs. That why traffic patterns change throughout the day. It’s the wind.
Male 765
scheckydamon Interesting to know!.
So N/S are always 36/18 ? There is never a 00/18?

I guess doesn't really matter what you identify 3 runways in parallel. If you know the rule and you have a visual on one of them, then you know where the other two are. (I was {over}thinking it with the "describe left and right over a radio" theory, since they are mearly arbitary names for relative locations - but its unlikely air traffic will be 'talking in' an aircraft with an alien at the helm because both pilots ate the chicken!)

Male 1,512
stifler Yes. N/S are always 36/18. It also has to do with the way you are approaching the runway. If your going North your compass heading is 360. Same on ships to an extent. You'll hear on movies them saying " Set heading to 0 degrees." but they would say "set heading to three six zero.".  It would make navigation math not work because if you multiply by zero the answer is always zero and you'll run into the North Pole eventually if all you ever do is go North.
It does matter as to the parallel runways because as with 36/18 it's based on the direction of travel. So the runway 18 R is when you are moving south and that same runway would be 36 L going North.
Mid air collisions being messy thing we do try and avoid them. Also all radio communications between aircraft and ground are conducted in English. The only time the carrier's native language is used is when talking to their offices from the aircraft.
Male 765
scheckydamon Very interesting, cheers.
I have done a heck of a lot of travel in my time (but not a pilots worth!) and I have picked up a few things, like ACAS systems (my uncle had something to do with them in the commercial airlines here) and the Air/Tower comms is in English, takeoff into the wind etc.

But I think it has always been the pushing tin side of things that was a bit of a mystery to me, and therefore interesting.

Other related craziness - like Heathrow; 4 active terminals but only has TWO runways! (3.5 Km long each though!!) intrigues me too.
Male 4,111
Great post, thank you.
Male 5,413
daegog My pleasure. Glad you liked it!
Female 9,601
I didn't even know they did this. However, I don't travel that much by plane.
Male 1,512
Well DUH! But then again I've been a pilot since I was 17.
Male 5,413
scheckydamon About the only people I'd expect to know this would be pilots. How did you start flying so early?
Male 1,512
squrlz4ever When I was but a wee lad, and it might still be this way, you got your glider license at 16 and moved on to you basic personal pilots license at 17. I joined the Coast Guard at 17 and by 19 was flying search and rescue helicopters. 3 years later they came along and said we need C-130 pilots so it was back to flight school. This was all pre GPS, computers, cell phones etc. We earned it the old fashioned way. Flew for 11.5 years and then lost my ticket due to inner ear problems. Hence started my slide to IAB.
Male 5,413
scheckydamon That's an amazing background you have there, Schecky. I had no idea you were a pilot, let alone flew helos and C-130s.
Male 1,512
squrlz4ever Hey, it was a living. No, actually a choice. When I showed up to my 10 year high, and I went through high school very high, school reunion, every one about shit when I came in dress blues and had AC wings and 2 bars of medals. I was voted most likely to die of an overdose. I love my country and I choose to serve man. My time in the service was the high point in my life. Until I had kids that is. Just goes to show, we old hippies never die, we just trip away.
Male 5,413
scheckydamon Good for you. That's an awesome life story there.

Postscript: Is it true that U.S. aircraft carriers now have LED runway displays that automatically change the runway numbers as the ship sails around and changes its compass orientation? That's a story that's making the rounds within the squirrel community.
Male 1,512
squrlz4ever Wouldn’t know. I was in the oldest navy, the Coast Guard. I had balls. I landed a huge helicopter on the back of a 378’ ship. I don need no stinkin’ Runway!
Male 5,413
scheckydamon LOL! You definitely have bigger balls than anyone else I know on here. Credit where credit is due. (You know I'm kidding about carriers changing the numbers on their flight deck, right? Duh... of course you do. That was my attempt at squirrelly humor.)
Male 1,024
umm that's obvious ?
Male 5,413
punko Apparently gargoyles are way smarter than small, furry rodents. At least I'm fluffy.

Male 1,832
punko Obvious? To whom? Wasn't to me.
Male 5,413
oobaka I'm with you. Wasn't obvious to me and (A) I fly a lot and (B) I live near a small airport. I don't see how anyone would know this without it being explained to him at some point.
Male 1,553
squrlz4ever I was in an army aviation unit so I learned this decades ago but I still remember when I first heard it.  While it’s common sense to use compass headings for the runway numbers, It is ingenious that they decided to truncate the heading to two digits - it really simplifies things (and saves paint!).
Male 5,413
woodyville06 It's very smart. I wish all things humans designed were this sensible.
Male 1,024
squrlz4ever Sorry, I guess.  I kinda thought everyone knew how runways were numbered.
Male 5,413
punko No, no worries. It's just irksome and embarrassing when you learn something new, share it, and hear back, "No duh." LOL!
Male 719
As an aspiring mathematician I find this very interesting.
Male 40,490
fuad119 Wouldn't it be simpler to just find out who's complicating equations and ask them to stop?
Male 715
Actually was pretty interesting, kudos!
Male 5,413
jayme21 Thanks! Glad you liked it, Jayme.