Runway Number Changes
Someone wrote a question recently regarding runway number changes. I thought it an interesting topic and I know that not everyone is aware (though I suspect most people reading this will be), so I thought I'd elaborate on it here, as well.
The reason is simple, once you know about it: a shift in magnetic north. A look at any well done map of certain projections will have mention of magnetic variation in the area (usually the center of the map unless specified), and with that should be a date (or at least a year), along with a rate of change. It might be something like "1997 Variation 21.2°W Annual change 2.4' East". This means that variation will change from the 21.2°W moving eastward at 2.4 minutes (1 minute is 1/60 of a degree), so over 25 years, variation would change to 20.2°W. This rate will be different for different areas since it's all relative to magnetic north and true north. Right now (2005), the magnetic north pole is in the Canadian Archipelago, at 82N114W, and is moving northwestward slowly.
When I first started working at CYHZ in 1992, the runway headings were 056/146/236/326. A few years after I moved to Moncton, they changed in the pubs to show 055/145/235/325. Last fall, they changed again to 054/144/234/324, thus passing the point where they should be renumbered. Given the construction planned (I've raved about this a few times, haven't I?), they decided they'd give an extension to the current numbering, and renumber them after construction while painting the numbers on the new pavement. That said, they missed the next publication deadline, and are now forced to issue NOTAMs ammeding approach plates, CFS entries, et al, instead of having correct information out there off the top. Another example of poor execution on the HIAA's part.
The reason is simple, once you know about it: a shift in magnetic north. A look at any well done map of certain projections will have mention of magnetic variation in the area (usually the center of the map unless specified), and with that should be a date (or at least a year), along with a rate of change. It might be something like "1997 Variation 21.2°W Annual change 2.4' East". This means that variation will change from the 21.2°W moving eastward at 2.4 minutes (1 minute is 1/60 of a degree), so over 25 years, variation would change to 20.2°W. This rate will be different for different areas since it's all relative to magnetic north and true north. Right now (2005), the magnetic north pole is in the Canadian Archipelago, at 82N114W, and is moving northwestward slowly.
When I first started working at CYHZ in 1992, the runway headings were 056/146/236/326. A few years after I moved to Moncton, they changed in the pubs to show 055/145/235/325. Last fall, they changed again to 054/144/234/324, thus passing the point where they should be renumbered. Given the construction planned (I've raved about this a few times, haven't I?), they decided they'd give an extension to the current numbering, and renumber them after construction while painting the numbers on the new pavement. That said, they missed the next publication deadline, and are now forced to issue NOTAMs ammeding approach plates, CFS entries, et al, instead of having correct information out there off the top. Another example of poor execution on the HIAA's part.
posted by Michael at
06:39
