All runways are equal

DavidWhite said:
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?
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Were you asking me?

If you were then it's easy, it's my job. In fact, I'm on vacation right now. I'm on a 7 on 7 off schedule so when I take a week off its really 3 weeks off. (the normal week befor and after the vacation work week)

So the map would be more filled in if I were actually working. I'm not sure what the Doritoes guys problem is. I don't think he likes me. Don't tell him I said that...






Edit to add: I'm no longer Navy or Student. Sorry if I projected otherwise.
 
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Meliss said:
Hey I found it interesting, and I'm glad you posted. I had never heard that before and I think it's pretty cool.
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My pleasure. And you are the reason I posted it. Thank you!
 
This is interesting. Never really thought about this before.

To find reciprocal headings though, i find it easier to add or subtract 180. (add 200 subtract 20, or subract 200 and add 20, depending on the heading). Nice easy numbers to work with.
 
Captain said:
Were you asking me?

If you were then it's easy, it's my job. In fact, I'm on vacation right now. I'm on a 7 on 7 off schedule so when I take a week off its really 3 weeks off. (the normal week befor and after the vacation work week)

So the map would be more filled in if I were actually working. I'm not sure what the Doritoes guys problem is. I don't think he likes me. Don't tell him I said that...
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So.....you're an enlisted navy pilot?
 
DavidWhite said:
So.....you're an enlisted navy pilot?
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I edited my post just as you posted this.

No, I was enlisted Navy (EW2(SW)) and then a student and then a CFI and then a commercial pilot. I am now on my 3rd 121 / 135 airline after 13 years of flying for hire.
 
Captain said:
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'.
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Initially it was the use of Cardinal with Heading instead of Point and then Relative with Heading instead of Bearing.

I'm just trying to get all the non standard phraseology you keep making up clear.
 
Everskyward said:
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.
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When I first got my Travelair it had one of those. :nonod:
 
Code testing for that issue:
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Woah Camel. All stop.

Stop and look at what you're doing. You're writing a big annoying computer program to essentially verify that you can add or subtract 18 or 180 from another number.

You don't even need software or a calculator or even manual math with a pencil and paper. All you need to do is use a compass for a short bit and the numbers you need come to mind without any math being involved. You just know the information.

You're all overthinking a problem that really isn't a problem to start with.
 
Henning said:
Initially it was the use of Cardinal with Heading instead of Point and then Relative with Heading instead of Bearing.

I'm just trying to get all the non standard phraseology you keep making up clear.
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Does someone pay you to be mean or do you just do it for free?
 
fgcason said:
Woah Camel. All stop.

Stop and look at what you're doing. You're writing a big annoying computer program to essentially verify that you can add or subtract 18 or 180 from another number.

You don't even need software or a calculator or even manual math with a pencil and paper. All you need to do is use a compass for a short bit and the numbers you need come to mind without any math being involved. You just know the information.

You're all overthinking a problem that really isn't a problem to start with.
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Settle down. The program was to test and see if Captain's claim was accurate without me sitting here brute-forcing my way through 36 runways by hand. Way faster for me to write the code. I spit out that in a matter of two or three minutes which is why it's not really that efficient.

I wasn't about to sit here and go through 36 runways and try to write down and keep track of all the possibilites and things that could go wrong with his formula.
 
jesse said:
Settle down. The program was to test and see if Captain's claim was accurate without me sitting here brute-forcing my way through 36 runways by hand. Way faster for me to write the code. I spit out that in a matter of two or three minutes which is why it's not really that efficient.

I wasn't about to sit here and go through 36 runways and try to write down and keep track of all the possibilites and things that could go wrong with his formula.
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Those brute-force approaches are so inelegant compared to a mathematical proof! :) :) :)


(thinking of some professors I've had in the math department)
 
Cap'n Jack said:
Those brute-force approaches are so inelegant compared to a mathematical proof! :) :) :)


(thinking of some professors I've had in the math department)
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It's all relative. My CPU executed the code in milliseconds. By far more time spent firing up the ruby interpreter then executing the ruby code.
 
jesse said:
It's all relative. My CPU executed the code in milliseconds. By far more time spent firing up the ruby interpreter then executing the ruby code.
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And you spent less time writing the code than formulating a formal proof too. I've meat some PhD's in math who might not accept your proof (I'm not saying they are right either!!!). As your code handled all of the possibilities, it would be acceptable to most of them. Some mathematicians are.....interesting!
 
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....
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This is what I do as well. :D
 
Most everyone figures out some method of "2s" system pretty quickly. I always used 200 & 20
 
I clicked on the thread thinking it was meaning equal as in, no matter how wide or narrow, pilots tend to use the runway. Such as when I landed at Roswell yesterday, I used proportionately the same amount of runway to each side as i do when i land at Muleshoe which is teeny and narrow.

Just an observation on my part.
 
jesse said:
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:


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:

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
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You brought up two issues;

A. Doesn't work for all runways.

B. Multiple False positives


I covered both issues in the OP.

A:
There are, according to your data, three runways that require extra effort. (1/19, 10/28, and 11/29)

But the numbers still work if you just keep adding double digits until left with a single digit. That's makes the overall premise correct and a unique property of runway numbers that's worth a conversation.


B:
That's not a bug, it's a feature. The false positives are ACTUALLY the perpendicular bearings and that informs the pilot of the direst crosswind. That can be useful in runway selection to achieve the crosswind with the most headwind component.

The point is all four Cardinal bearings for any given runway can be found by adding the number until a single digit is reached. Upper right starts with a 0, Lower right with a 1, Lower left with a 2, and Upper left with a 3.
 
I did not see that coming...
 
The captain noticed that if you add 9 to a natural number, any number of times, you don't change the sum of digits (done recursively). It's true, Ruby programs notwithstanding. There are quite a few of those bar bet style factoids in number theory.

However, there are only 18 different runway pairs, and that's phenomenally easy to memorize. Or use a DG or CDI if you must. Both are much faster than the add the digits game.

And of course adding or subtracting 18 works very well.
 
MAKG1 said:
However, there are only 18 different runway pairs, and that's phenomenally easy to memorize...
And of course adding or subtracting 18 works very well.
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1) I made up flash cards for each cardinal pair, 1/19, 2/20, 3/21, etc. Does not take long to do what we all did originally with multiplication tables, just memorize them.

2) One hint: rather than adding or subtracting 18, which can be hard to do in your head, especially when tired, either add 200 and subtract 20 or subtract 200 and add 20. Two steps instead of one, but many find it much easier to do.

Apologies if either of these came up before this thread was brought back from the dead.
 
BTW, the 200 / 20 thing has been suggested since forever and people still have troubles with reciprocal runways. This is just another tool in the belt with an added benefit of giving the perpendicular too. Who's not for more tools? Besides, what works for some may not work for others. I had a slew of ways to teach NDB tracking.
 
This is what the Metal Landing Calculator is for...:D (or just look at the bloody DG/HSI)
 
I carry a raspberry Pi with a number pad for entering the runway and a digital lcd that outputs the result. It's the only safe way to figure out the opposite runway number.

It's enclosed in a metal box and is definitely the finest metal landing calculator available in the world. If anyone is interested I can sell you one, with your N number engraved into the case, for $399.

(you will need a cigarette power output that can support the 20 amp draw from the landing calculator, my Ruby routine is rather inefficient)
 
This resurrection reminds me of a Seinfeld episode...

"The Jerk Store called..."

Keep up the good work Cantstandya.
 
jesse said:
I carry a raspberry Pi with a number pad for entering the runway and a digital lcd that outputs the result. It's the only safe way to figure out the opposite runway number.

It's enclosed in a metal box and is definitely the finest metal landing calculator available in the world. If anyone is interested I can sell you one, with your N number engraved into the case, for $399.

(you will need a cigarette power output that can support the 20 amp draw from the landing calculator, my Ruby routine is rather inefficient)
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Two questions,

Is that $399 just for the engraving or does that cover the whole thing?, and

Can I get 10?
 
jesse said:
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 captain_formula(runway)
   first, last = runway.divmod(10)
   first + last
end

So it's wrong 6 of the 36 times. That's not so perfect.
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FWIW, your code is wrong. You need to make your captain_formula function recursive based on result>=10 to make it right. Or at least use a while loop.
Unit testing would have given the bug away easily.
 
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