All runways are equal

Captain

Captain

Final Approach
Joined
Mar 12, 2012
Messages
8,006
Location
NOYB
Display Name
Display name:
First Officer
Has anyone ever noticed that all runways are equal?

What do I mean by that? Well, obviously some are shorter than others and some are wider. That's not what I'm talking about. When I say all runways are equal I mean literally.

The runway numbers, when added up always equal the opposite runway numbers sum. Take runway 9. What's the other direction? That's right, 27. What's 2 + 7? ....yup, 9!

It works for all of 'em. 15 and 33. Add them up and you get 6 for both. 4 and 22? Obvious. 30 and 12? Get the idea?

What's more is it works for the perpendicular course as well. Take 4 and 22. The sum is 4. But the perpendicular courses equal 4 as well! If you are landing on runway 4 then a straight crosswind from the right would be from 130 and a straight crosswind from the left would be from 310. All of them equal 4. That works for any runway.

Landing on 35 the tail wind comes from 170 and the right crosswind from 080 and the left from 260. All added equal 8. Crazy I know!

What's more is if you look at the compass rose and divide it into quadrants then the NE quadrant typically starts with a zero, the SE quad starts more or less with a one, the SW usually starts with a two and the NW mostly start with threes.

You can use that information to quickly figure out all of the cardinal headings for whatever runway you are landing on. If you are landing on runway 26 (SW quad) then you know a straight left cross wind would come from a heading that starts with a one and equals 8. So it must be 170. And a straight right crosswind would come from a heading that starts with a three (NW) and also equal 8. So that has to be 350.

That's handy when you're landing on 07 and the winds are 330 at 20 kits. Is that a head wind or tail wind. Well now you know the straight crosswind has to start with a 3 and equal 7, so 340 is the perpendicular crosswind, therefore 330 is a slight tail wind. Maybe land the other way....

There are a few exceptions to this rule like 28 and 10. Notice 2 + 8 = 10 and 1 + 0 equal 1. But if you add again the results it still works. 2 + 8 = 10, 1 + 0 = 1 which matches the results of runway 10.

Anyway. Thought I'd share an easy way to find the cardinal headings for any runway assignment.
 
Captain said:
Has anyone ever noticed that all runways are equal?

What do I mean by that? Well, obviously some are shorter than others and some are wider. That's not what I'm talking about. When I say all runways are equal I mean literally.

The runway numbers, when added up always equal the opposite runway numbers sum. Take runway 9. What's the other direction? That's right, 27. What's 2 + 7? ....yup, 9!

It works for all of 'em. 15 and 33. Add them up and you get 6 for both. 4 and 22? Obvious. 30 and 12? Get the idea?

What's more is it works for the perpendicular course as well. Take 4 and 22. The sum is 4. But the perpendicular courses equal 4 as well! If you are landing on runway 4 then a straight crosswind from the right would be from 130 and a straight crosswind from the left would be from 310. All of them equal 4. That works for any runway.

Landing on 35 the tail wind comes from 170 and the right crosswind from 080 and the left from 260. All added equal 8. Crazy I know!

What's more is if you look at the compass rose and divide it into quadrants then the NE quadrant typically starts with a zero, the SE quad starts more or less with a one, the SW usually starts with a two and the NW mostly start with threes.

You can use that information to quickly figure out all of the cardinal headings for whatever runway you are landing on. If you are landing on runway 26 (SW quad) then you know a straight left cross wind would come from a heading that starts with a one and equals 8. So it must be 170. And a straight right crosswind would come from a heading that starts with a three (NW) and also equal 8. So that has to be 350.

That's handy when you're landing on 07 and the winds are 330 at 20 kits. Is that a head wind or tail wind. Well now you know the straight crosswind has to start with a 3 and equal 7, so 340 is the perpendicular crosswind, therefore 330 is a slight tail wind. Maybe land the other way....

There are a few exceptions to this rule like 28 and 10. Notice 2 + 8 = 10 and 1 + 0 equal 1. But if you add again the results it still works. 2 + 8 = 10, 1 + 0 = 1 which matches the results of runway 10.

Anyway. Thought I'd share an easy way to find the cardinal headings for any runway assignment.
Click to expand...

I sense a contradiction.
 
Well, it still works...you just have to keep adding the result if it doesn't right away. After a little practice your mind starts to find the correct answer very quickly.
 
Captain said:
Well, it still works...you just have to keep adding the result if it doesn't right away. After a little practice your mind starts to find the correct answer very quickly.
Click to expand...

Right, they all work the same if you treat some of them differently, got it.

Have a nice day.
 
meh, I was just posting cause it works for me. YMMV
 
Wonderful analysis. Another tool for the kit. Thanks.
 
Add or subtract 18 and you're there without separating the ones and tens digit.

Runway 32 is 18 carry the, wait, subtraction, 8 from 2, um, 3-1 um, 2-1 and 12 from 8, no 8 from 12, then add something. oh wait. 3+2=5 and what other numbers add up to 5 now 2+3 does so it's 23, wait, that can't be right.

Ugh. More tedious math when you need to be looking out the window. Just learn the compass. The mountain hiding in the cloud is trying to run into you so up and left on the compass is down and right so, 32 is 14.
 
Yep, you'll spend most of the day figuring out 1 and 19. Dunno how long it takes, but after a while you just know based on places you've flown.
If worse comes to worse, just read the big letters painted on the end. If you can't remember, listen to ATIS. Or just announce on unicom that you're landing south.

fgcason said:
Add or subtract 18 and you're there without separating the ones and tens digit.

Runway 32 is 18 carry the, wait, subtraction, 8 from 2, um, 3-1 um, 2-1 and 12 from 8, no 8 from 12, then add something. oh wait. 3+2=5 and what other numbers add up to 5 now 2+3 does so it's 23, wait, that can't be right.

Ugh. More tedious math when you need to be looking out the window. Just learn the compass. The mountain hiding in the cloud is trying to run into you so up and left on the compass is down and right so, 32 is 14.
Click to expand...
 
Runway: 01 / 19

Math: 0 + 1 = 1 || 1 + 9 = 10 cont...1 + 0 = 1

Point: It works. Are there some that are more work that others? yup. But it does work and a benefit is now I know the cardinals too: 100 and 280.


Conclusion: If if works for you then GREAT!! Glad it helped. If not then at least it's a sorta neat numbers exercise that many may not have known about.
 
During which phase of flight or flight planning do you find this to be the most helpful?

Captain said:
Runway: 01 / 19

Math: 0 + 1 = 1 || 1 + 9 = 10 cont...1 + 0 = 1

Point: It works. Are there some that are more work that others? yup. But it does work and a benefit is now I know the cardinals too: 100 and 280.


Conclusion: If if works for you then GREAT!! Glad it helped. If not then at least it's a sorta neat numbers exercise that many may not have known about.
Click to expand...
 
Usually about 100 out or so when I get the landing runway and winds. I use this to determine if it's a slight head wind or tail wind.

Example: runway 4 is in use. Winds are 300 at 15 gust 22. Using my 'technique' I know the direct cross wind starts with a 3 and adds up to 4. 310 is the direct. 300 would, therefore, be a slight tail wind.

As with most things in aviation, it's harder to explain than do.
 
Captain said:
Usually about 100 out or so when I get the landing runway and winds. I use this to determine if it's a slight head wind or tail wind.

Example: runway 4 is in use. Winds are 300 at 15 gust 22. Using my 'technique' I know the direct cross wind starts with a 3 and adds up to 4. 310 is the direct. 300 would, therefore, be a slight tail wind.

As with most things in aviation, it's harder to explain than do.
Click to expand...
I think it's easier to look at the HSI or DG. No math involved.

But then I once flew an airplane which had one of those vertical card DGs which looked like the compass. That made it difficult, however I don't think there are many DGs out there like that any more.
 
If you have an HSI or DG it sure would. I do not, at least not on my primary display. I could dial it in if I wanted but that would be more work for me.

I'll be the first to admit it's sort of an academic discussion...but it's sort of neat (I think) and worth at least a thread to talk about.
 
captain said:
The runway numbers, when added up always equal the opposite runway numbers sum. Take runway 9. What's the other direction? That's right, 27. What's 2 + 7? ....yup, 9!
Click to expand...
Sorry Captain - but your claim is totally wrong. If you actually taught this as a way for someone to find the opposite runway they'd be wrong quite often.

So first off, I'll check to see if your formula is even CORRECT for all the runways.
Code: 
def runway_recip(runway) 
   recip = runway + 18
   recip > 36 ? recip - 36 : recip
end

def captain_formula(runway)
   first, last = runway.divmod(10)
   first + last
end

#Check Captain's formula
runways = 1..36

runways.each { |runway|

   if captain_formula(runway) == captain_formula(runway_recip(runway))
      puts "TRUE Runway #{runway}"
   else
      puts "FALSE RUNWAY #{runway}"
   end
   
}
..and the answer:
FALSE RUNWAY 1
TRUE Runway 2
TRUE Runway 3
TRUE Runway 4
TRUE Runway 5
TRUE Runway 6
TRUE Runway 7
TRUE Runway 8
TRUE Runway 9
FALSE RUNWAY 10
FALSE RUNWAY 11
TRUE Runway 12
TRUE Runway 13
TRUE Runway 14
TRUE Runway 15
TRUE Runway 16
TRUE Runway 17
TRUE Runway 18
FALSE RUNWAY 19
TRUE Runway 20
TRUE Runway 21
TRUE Runway 22
TRUE Runway 23
TRUE Runway 24
TRUE Runway 25
TRUE Runway 26
TRUE Runway 27
FALSE RUNWAY 28
FALSE RUNWAY 29
TRUE Runway 30
TRUE Runway 31
TRUE Runway 32
TRUE Runway 33
TRUE Runway 34
TRUE Runway 35
TRUE Runway 36
Click to expand...

So it's wrong 6 of the 36 times. That's not so perfect.

But there is another problem. There are other runways that will add up to teh same value basically leaving you with multiple choices or just leading one to think they have the right answer but in reality it's totally wrong.

Example of that: RWY 12, the real reciprocal of that is 30. 1 + 2 = 3. 3 + 0 = 3. Great. But there are other runways that also add up to 3: RWY 3 and RWY 21.
Code testing for that issue:
Code: 
def runway_recip(runway)
   recip = runway + 18
   recip > 36 ? recip - 36 : recip
end

def captain_formula(runway)
   first, last = runway.divmod(10)
   first + last
end

runways = 1..36

sums = []
runways.each { |runway|
   sums << {:runway => runway, :sum => captain_formula(runway)}
}


runways.each { |runway|
   potential_runways = []

   sums.each { |sum|
      if sum[:sum] == captain_formula(runway)
         potential_runways << sum[:runway]
      end
   }
   result = '';
   potential_runways.each { |potential|
         result = "#{result} RWY #{potential}"
   }

   puts "RWY #{runway} POTENTIAL MATCHES: #{result}"
}
Results of that code:
RWY 1 POTENTIAL MATCHES: RWY 1 RWY 10
RWY 2 POTENTIAL MATCHES: RWY 2 RWY 11 RWY 20
RWY 3 POTENTIAL MATCHES: RWY 3 RWY 12 RWY 21 RWY 30
RWY 4 POTENTIAL MATCHES: RWY 4 RWY 13 RWY 22 RWY 31
RWY 5 POTENTIAL MATCHES: RWY 5 RWY 14 RWY 23 RWY 32
RWY 6 POTENTIAL MATCHES: RWY 6 RWY 15 RWY 24 RWY 33
RWY 7 POTENTIAL MATCHES: RWY 7 RWY 16 RWY 25 RWY 34
RWY 8 POTENTIAL MATCHES: RWY 8 RWY 17 RWY 26 RWY 35
RWY 9 POTENTIAL MATCHES: RWY 9 RWY 18 RWY 27 RWY 36
RWY 10 POTENTIAL MATCHES: RWY 1 RWY 10
RWY 11 POTENTIAL MATCHES: RWY 2 RWY 11 RWY 20
RWY 12 POTENTIAL MATCHES: RWY 3 RWY 12 RWY 21 RWY 30
RWY 13 POTENTIAL MATCHES: RWY 4 RWY 13 RWY 22 RWY 31
RWY 14 POTENTIAL MATCHES: RWY 5 RWY 14 RWY 23 RWY 32
RWY 15 POTENTIAL MATCHES: RWY 6 RWY 15 RWY 24 RWY 33
RWY 16 POTENTIAL MATCHES: RWY 7 RWY 16 RWY 25 RWY 34
RWY 17 POTENTIAL MATCHES: RWY 8 RWY 17 RWY 26 RWY 35
RWY 18 POTENTIAL MATCHES: RWY 9 RWY 18 RWY 27 RWY 36
RWY 19 POTENTIAL MATCHES: RWY 19 RWY 28
RWY 20 POTENTIAL MATCHES: RWY 2 RWY 11 RWY 20
RWY 21 POTENTIAL MATCHES: RWY 3 RWY 12 RWY 21 RWY 30
RWY 22 POTENTIAL MATCHES: RWY 4 RWY 13 RWY 22 RWY 31
RWY 23 POTENTIAL MATCHES: RWY 5 RWY 14 RWY 23 RWY 32
RWY 24 POTENTIAL MATCHES: RWY 6 RWY 15 RWY 24 RWY 33
RWY 25 POTENTIAL MATCHES: RWY 7 RWY 16 RWY 25 RWY 34
RWY 26 POTENTIAL MATCHES: RWY 8 RWY 17 RWY 26 RWY 35
RWY 27 POTENTIAL MATCHES: RWY 9 RWY 18 RWY 27 RWY 36
RWY 28 POTENTIAL MATCHES: RWY 19 RWY 28
RWY 29 POTENTIAL MATCHES: RWY 29
RWY 30 POTENTIAL MATCHES: RWY 3 RWY 12 RWY 21 RWY 30
RWY 31 POTENTIAL MATCHES: RWY 4 RWY 13 RWY 22 RWY 31
RWY 32 POTENTIAL MATCHES: RWY 5 RWY 14 RWY 23 RWY 32
RWY 33 POTENTIAL MATCHES: RWY 6 RWY 15 RWY 24 RWY 33
RWY 34 POTENTIAL MATCHES: RWY 7 RWY 16 RWY 25 RWY 34
RWY 35 POTENTIAL MATCHES: RWY 8 RWY 17 RWY 26 RWY 35
RWY 36 POTENTIAL MATCHES: RWY 9 RWY 18 RWY 27 RWY 36
Click to expand...
There are so many problems with your formula that it's really not even worth telling someone. They'd need a flow chart to handle the exceptions.

An accurate way, that actually works correctly is:
def runway_recip(runway)
recip = runway + 18
recip > 36 ? recip - 36 : recip
end
 
Captain said:
If you have an HSI or DG it sure would. I do not, at least not on my primary display. I could dial it in if I wanted but that would be more work for me.
Click to expand...
OK, but how many pilots here are in that situation? I'll admit that I wasn't sure what some of the small aircraft glass panels so I looked them up. Here is a G1000

sc-03-lg.jpg


And here is an Aspen

EFD1000Pro.gif


Together they probably make up a large number of glass displays on small airplanes. You might be able to select ARC mode on some units so that the reciprocal is not displayed but it seems like most of the information I have seen on the internet shows the HSI mode.
 
Very simple way to find reciprocal runway (in your head)... for 180 or less, add 200 and subtract 20. Over 180, add 20 and subtract 200.
 
Wow Jesse, I thought I was 'nerding out' when I posted. I see now I was nowhere near the red part of the nerd-meter! : )

1) the op discussed times it doesn't work perfect. You algarythm failed to look at those and 100% of 'those' my step two fixed. Re-add. 1/19 (1+0 is 1, 1+9 is 10...1+0 is 1. Success.

2) Those 'multiple' positives that you brought up are not a failure, they are a feature. Those are the cardinal headings. The straight perpendicular headings. Those can be useful. I mentioned the quadrants and how they start with a 0,1,2, or 3 to make it easy.

Runway 5. Recip is a number that equals 5 and starts with a 2. Easy..23. The cross winds equal 5 and start with a 3 (left) and 1 (right). So it's 32 to the left and 14 to the right.

I'm in a car right now sitting in a parking lot waiting for a break in the rain. No DG or HSI but I know these to be true. Why? Because it works.
 
??? The only time I have heard the term 'Cardinal' used in connection with a compass is in Cardinal Points N,S,E,W with Sub Cardinal Points of NE, SE, SW, NW., I've never heard/seen numeric headings referred to as Cardinal; could you show me where that is?
 
Certainly.

Cardinal headings refer to the 360, 090, 180 and 270. They can refer to the compass referenced to magnetic North as on a DG. They can also be relative to your own ship. Traffic at 12 O'Clock is a prime example. ATC doesn't usually call traffic using the clock referenced to true or magnetic North. They reference it to your aircraft (more specifically your aircraft track.)

The only time the earth's magnetic or true cardinal bearings line up with the airplanes cardinal bearings is when you fly due North (either magnetic or True).

Many times in maritime sailing ships use relative heading as a useful tool. 090 relative bearing is off the starboard side.
 
Last edited:
Somewhat related to the OP, yet not aviation related...

The 'magic' of 9's.

9 x 2 = 18; 1 + 8 = 9
9 x 5 = 45; 4 + 5 = 9
9 x 9 = 81; 8 + 1 = 9
4572389 x 9 = 41151501; 4 + 1 + 1 + 5 + 1 + 5 + 0 + 1 = 18; 1 + 8 = 9

It's about as useful in the real world as the OP.
 
Captain said:
Certainly.

Many times in maritime sailing ships use relative heading as a useful tool. 090 relative bearing is off the starboard side.
Click to expand...

25 years as a captain in the maritime industry I have never heard of a relative heading; relative bearings however are continuously measured for navigation and collision avoidance.
 
This is about my using the term relative headings in lieu of relative bearings? The nautical forums would be aghast, I'm sure.


Oh, wait...I did use the term 'relative bearing'.

Captain said:
...Many times in maritime sailing ships use relative heading as a useful tool. 090 relative bearing is off the starboard side.
Click to expand...
 
Last edited:
FlySince9 said:
Very simple way to find reciprocal runway (in your head)... for 180 or less, add 200 and subtract 20. Over 180, add 20 and subtract 200.
Click to expand...
I like that! Thanks for posting it!
 
Yeah, I'm not trying to tell anyone how to do anything here. I just thought it was sort of neat. It does work for me...but as I've said, I do not have an HSI or DG in front of me readily available.

If anybody has an easier way to do it then please use that. If you don't think the OP was interesting then please disregard.
 
Measure it with a micrometer

Mark it with a grease pencil

Chop it with an axe



For christ's sake people.....
 
I love that saying! Words to live by...
 
Captain said:
If anybody has an easier way to do it then please use that. If you don't think the OP was interesting then please disregard.
Click to expand...

Interesting yes.

Easier maybe is this :
  • + 2 -2 example heading 147 = 1 + 2 = 3, 4 - 2 = 2 = reciprocal 327
  • -2 + 2 example heading 347 = 3 - 2 = 1, 4 + 2 = 6 = reciprocal 167

works as far as I know for any heading :wink2:

the simplicity of it would probably make a whole lot more sense if I formatted the math vertically.... but I'm too lazy to rewrite all of that....
 
jaybee said:
Interesting yes.

Easier maybe is this :
  • + 2 -2 example heading 147 = 1 + 2 = 3, 4 - 2 = 2 = reciprocal 327
  • -2 + 2 example heading 347 = 3 - 2 = 1, 4 + 2 = 6 = reciprocal 167

works as far as I know for any heading :wink2:

the simplicity of it would probably make a whole lot more sense if I formatted the math vertically.... but I'm too lazy to rewrite all of that....
Click to expand...


I like it.
 
I've got this acronym that works great for memorizing the entire checklist for ANY plane, and it works for all of them except Pipers, most Cessnas, half the Mooneys, all multiengine planes, 3 years of Beechcrafts....
 
EdFred said:
I've got this acronym that works great for memorizing the entire checklist for ANY plane, and it works for all of them except Pipers, most Cessnas, half the Mooneys, all multiengine planes, 3 years of Beechcrafts....
Click to expand...

Is the acronym IMANIDIOT?
 
So just out of curiosity - How do you find the time to fly to 12+ states in a month between being an enlisted navy man and student?
 
Captain said:
Yeah, I'm not trying to tell anyone how to do anything here. I just thought it was sort of neat. It does work for me...but as I've said, I do not have an HSI or DG in front of me readily available.

If anybody has an easier way to do it then please use that. If you don't think the OP was interesting then please disregard.
Click to expand...

Hey I found it interesting, and I'm glad you posted. I had never heard that before and I think it's pretty cool.
 
jaybee said:
Interesting yes.

Easier maybe is this :
  • + 2 -2 example heading 147 = 1 + 2 = 3, 4 - 2 = 2 = reciprocal 327
  • -2 + 2 example heading 347 = 3 - 2 = 1, 4 + 2 = 6 = reciprocal 167

works as far as I know for any heading :wink2:

the simplicity of it would probably make a whole lot more sense if I formatted the math vertically.... but I'm too lazy to rewrite all of that....
Click to expand...

This is what my instructor taught me. I never remember it though- I am not the quickest when it comes to numbers. I usually just add or subtract 180. Somehow that's easier for me.
 
You must log in or register to reply here.
Back
Top