Runway ID

On Sun, 16 Oct 2005 15:56:35 -0600, Newps wrote:

Another example is MSP

and another one is PHX, IIRC.

#m

--
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four times and it becomes a fact. Repeat an assertion four times and it
becomes a fact. Repeat an assertion four times and it becomes a fact.

"nrp" wrote in message
oups.com...

Crystal airport (MIC) in Minneapolis area went from runways 4/22 to
6/24 a few years ago. I don't know why so much change though.......


I have a MIC airport diagram dated 97310. The present runway 6L/24R was
then 5L/23R. The present runway 6R/24L was then 5R/23L. There has been no
change in the magnetic azimuth of these runways. The magnetic azimuth of
runway 6L/24R is 050.6/230.6, as it was eight years ago. The magnetic
azimuth of runway 6R/24L is 050.7/230.7, as it was eight years ago. The
local variation on these charts is 2.6E, a January 1995 value. Why were
these runways redesignated?

"Morgans" wrote in message
...

"Steven P. McNicoll" wrote

"On a single runway, dual parallel runways and triple parallel runways,
the
designation number is the whole number nearest one-tenth of the magnetic
azimuth when viewed from the direction of approach."

Roger that.

What was being discussed, was -renaming- a runway, due to the -changing-
magnetic variation.


Yes, that's what I addressed. It says, "the designation number is the whole
number nearest one-tenth of the magnetic azimuth". It offers no exceptions.

"Morgans" wrote in message
...

Are there other runways in the area with a 5/23 designation?


Not at MIC.

"Steven P. McNicoll" wrote

"On a single runway, dual parallel runways and triple parallel runways,
the
designation number is the whole number nearest one-tenth of the magnetic
azimuth when viewed from the direction of approach."

Roger that.

What was being discussed, was -renaming- a runway, due to the -changing-
magnetic variation.
--
Jim in NC

"Steven P. McNicoll" wrote

The magnetic
azimuth of runway 6R/24L is 050.7/230.7, as it was eight years ago. The
local variation on these charts is 2.6E, a January 1995 value. Why were
these runways redesignated?

Are there other runways in the area with a 5/23 designation?
--
Jim in NC

"Newps" wrote

You most certainly do. Our parallel runways here at BIL were renumbered
from 27 R+L to 28 R+L several years ago. They did this at the same time
they rotated the VOR for the same reason. Another example is MSP. The
parallel runways there were 11/29 until a few years ago when they were
renumbered to 12/30

I have never heard of that, before now. I'm sure they must do that to make
people keep buying new, up to date charts. g
--
Jim in NC

"Jose" wrote in message
. ..
Ah, because the REAL rounding rule, designed so that averages will not
become distorted high from rounding 1/2 up, is to round 1/2 to the
EVEN number.

I know of almost no teacher nor textbook that remembers this, much
less why it is so.

That's because it's not so.

The standard rounding rule is 5 goes up.

If you have 0.245, it is 0.24 rounded to hundreths. How is that '5 goes up?'

The rounding rules I am talking about are for preventing rounding bias in
data. If you took a big pile of numbers, rounded them all up, added them,
you would have a value that was way off of the true value of the sum.

0.247 0.25 0.2550.26 is that what you mean? That's exactly what I
stated.

The catch is that you ONLY round from the digit after the one you're
rounding to. For example, .2447 rounds to .245 or to .24 or to .2
although a common error is to round (to the hundredths) as .25, because
the "rounded to the thousanths" version would end in a five. When
rounding, always round from the source, not an already adulterated
version.

Jose

Yes, you don't round a number, then round it again.


"GeorgeB" wrote in message
...

If these runways were at the same field, your method would have runway
designators that differ by twenty degrees for runways that have a difference
in azimuth of only ten degrees. I think I'd round both in the direction
that local magnetic variation was moving.

Yes, that would be logical.

The thing that causes runways to get renumbered is the fact that the
magnetic variation itself, shifts. It may shift six minutes ( a tenth of a
degree ) per year. So after ten years, the local mag. variation may change
from 6° W to 7° W . So every few years, runways get assigned new numbers.
This gradual shift varies by locality on the globe. Areas that are
volcanically active can have huge shifts of 30 minutes or more per year.

"Newps" wrote in message
news
You would choose the number to which the magnetic variation is taking
the runway. For example around the western US you would choose the
higher number as if you don't you'll have to renumber the runway that
much sooner.

If you have 0.245, it is 0.24 rounded to hundreths. How is that '5 goes up?'

If you actually have 0.245, it is 0.25 rounded to hundredths. However,
if you actually have 0.2445, you do NOT have .0245 but a hair less than
that. In that case, you don't =have= a five to "go up".

If you took a big pile of numbers, rounded them all up, added them,
you would have a value that was way off of the true value of the sum.

True. But you don't round them all =up=. You round them all (to the
nearest). Only the ones that are ...5 and up get rounded up. The
others get truncated. Including ...0 which gets its zero truncated
(leaving the number unchanged).

0.247 - 0.25 0.255 - 0.26 is that what you mean? That's exactly what I
stated.

This is correct rounding, but it is it what George stated. He stated
"round 1/2 to the EVEN number.", which would imply .245 - .26 which is
not true. What =is= true is
..245 - .25
..255 - .26
..265 - .27

This is not "rounding 1/2 to the even number".

Jose
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