I'm old enough to remember when the runways were 28L and 28R but can't remember when they changed to 27L and 27R (presumably because of mag var and I presume they are designated to the nearest whole degree). Here's my questions:-1. Who can remember when they changed please ? - think it must have been about 1980.2. By how much does the magnetic variation have to change in order to trigger the need to change the designation.3. Do many airports in the world have to make this change or does it only affect those nearer the poles.4. Will Heathrow ever change back again - if so - how long / when will this be.

Hi Dave,

I'm old enough to remember when the runways were 28L and 28Rbut can't remember when they changed to 27L and 27R (presumably because of mag var and I presume they are designated to the nearest whole degree). Here's my questions:-

I'm away on a business trip right now but back on Saturday 7th so I'll try to have the answers for you shortly.cheers,Lee

2nd July 1987 was the date in question.

Lee,thanks - thought it was roundabout then, any thoughts on my other questions.

"2. By how much does the magnetic variation have to change in order to trigger the need to change the designation."In theory, the numbers should reflect the nearest 10 degree increment.E.g. runway 28 headings could be 275(rounded up, I believe), 276, 277, 278, 279, 280, 281, 281, 283 and 284.However, some airports don't even bother changing the designation. For example, runway 07/25 at YSSY has a magnetic heading of 062/242. No doubt $$$'s influence the decision to change the designation."3. Do many airports in the world have to make this change or does it only affect those nearer the poles."Magnetic variation is not necessarily greatest nearest the poles. If you can find a pic of the world showing variation contours, you will see this to be the case."4. Will Heathrow ever change back again - if so - how long / when will this be."Changes can take thousands of years in some cases. Scientists say that the poles could completely flip (North could become south and south could become north).Hope this helps.Cheers.Q>

Very good thanks !

>>>However, some airports don't even bother changing the designation. For example, runway 07/25 at YSSY has a magnetic heading of 062/242. No doubt $$$'s influence the decision to change the designation.:(

I started flying in 1963, and since then quite a few runway designations changed. The rate of change of magnetic variation is published on aeronautical charts. As example the current rate in Israel is 3 minutes east per annum, so the old runways 02 in Eilat and Tel Aviv Sde Dov Municipal are now 03's.

>2nd July 1987 was the date in question.2nd july 87 --> 2/7/ 87 runway 2 7HAHA!Alex

You didn't happen to be flying an A320 where you?;)

On this occasion I was in a 744, my good man! ;-)