Slashdot Mirror
Why Airports Rename Runways When the Magnetic Poles Move (wired.com)
An anonymous reader shares a report: For decades, pilots heading into or out of Wichita Eisenhower National Airport in southeast Kansas have had three runways to choose from: 1L/19R, 1R/19L, and 14/32. Now, at the orders of the FAA, the airport will spend hundreds of thousands of dollars to give itself a makeover. Workers will repaint those huge numbers at the ends of each runway and replace copious signage. Pilots and air traffic controllers will study new reference manuals and approach plates, all updated to reflect an airport whose three runways have been renamed. World, meet 2L/20R, 2R/20L, and 15/33 -- which happen to be the same runways that have been welcoming planes since 1954.
This is not a "What's in a name?" situation. The runways may be the same sweet-smelling stretches of tarmac they've always been, but the world around them has changed. Well, the magnetic fields around the world have changed. The planet's magnetic poles -- the points that compasses recognize as north and south -- are always wandering about. That's a problem, because most runways are named for their magnetic headings. Take Wichita's 14/32. First off, because planes can land or take off from either direction, you can think of it as two runways: 14 and 32. (Pro tip: Pilots say "one-four" and "three-two," not 14 and 32.) If you're looking at a compass, one end is about 140 degrees off of north, counting clockwise. For simplicity's sake, the headings are rounded to the nearest five, and dropped to two digits. So if you're looking down at Wichita Eisenhower, runway 14/32 is the one running from the northwest to the southeast.
This is not a "What's in a name?" situation. The runways may be the same sweet-smelling stretches of tarmac they've always been, but the world around them has changed. Well, the magnetic fields around the world have changed. The planet's magnetic poles -- the points that compasses recognize as north and south -- are always wandering about. That's a problem, because most runways are named for their magnetic headings. Take Wichita's 14/32. First off, because planes can land or take off from either direction, you can think of it as two runways: 14 and 32. (Pro tip: Pilots say "one-four" and "three-two," not 14 and 32.) If you're looking at a compass, one end is about 140 degrees off of north, counting clockwise. For simplicity's sake, the headings are rounded to the nearest five, and dropped to two digits. So if you're looking down at Wichita Eisenhower, runway 14/32 is the one running from the northwest to the southeast.
its says they round to nearest 5 then truncate to two digits. Perhaps it was 197-->198.
From TFA: "Things only change when the compass reading shifts a certain amount. Say the pole shifts such that the heading of 258 degrees is actually 259 degrees. That still rounds to 260, and the runway would still be called 26. But if the compass reading goes from 258 to 254, you’re now looking at runway 25."
They should just use the geographical headings instead of magnetic headings.
Except, the compass on board the airplane that needs to use the runway ... is magnetic. By definition.
Don't disappoint your bird dog. Go to the range.
Pilots already know how convert between magnetic and geographical headings, I would think. I think the small inconvenience is better than having outdated runway markings or having to renew them every now and then (not only on the runways themselves, but also on all charts).
Um, no. First of all, the conversion isn't consistent from place to place. For example, as you move across degrees of longitude, the angular difference between the magnetic and geographic north changes. So, your conversion changes. The last thing you want to do to a pilot is to add more shit on his plate, trying to do calculations when he could simply compare his compass and the giant number printed on the runway.
FWIW, I was a private pilot in the 80s & 90s, but gave it up when my kid was born...just didn't have time.
Just another day in Paradise
magnetic shifts aren't universal. Well, they are, but the measurement of how much they shifted isn't universal. If one is inline with the direction it moved, there is virtually zero change in magnetic compass heading, but if one is perpendicular to its movement, then there is a very large change. This rate of change gets larger the closer one is to the magnetic pole.
Z
The numbers get updated (God knows why) when the poles move.
Pilots also know why.
When on final approach, the number you see on the end of the runway should match what is on your compass. The compass is the "navigational aid of last resort", as it does not require any mechanical, vacuum or electrical assistance to work. How you set up for that runway...even how you approach the airport...depends on that number. Flying into an unfamiliar airport with screwed up runway numbers will add an extra layer of unnecessary complication.
Aah, change is good. -- Rafiki
Yeah, but it ain't easy. -- Simba
As someone that has had the engine go silent at 7,000 feet, I can state with authority that you have no clue of what you're talking about. The stress of an emergency, "do it right the first time or die" situation has so much adrenalin pumping through your veins that basic math is near impossible. I was making radio calls that I was north east of the airport, when I was south of it (north east was where I was headed when the engine quit). Reading minuscule numbers off a sectional in order to calculate a deviation while trying to maintain best glide speed and keep calm. You simply have no clue what a ridiculous request that is.
Aah, change is good. -- Rafiki
Yeah, but it ain't easy. -- Simba