Wasting Time on Runway Direction Variation Changes

A news story on Twitter (via @Speedbird_NCL) caught my eye the other day. The gist of it was that due to fluctuations in the Earth's magnetic field, the numbers assigned to runways in the US were being re-designated due to changes in the runway's magnetic direction.

runway number

And I thought, what a load of rubbish!

But let's take a quick step back just to put everyone on the same page. I don't want to assume anything, so let's go through the scenario one step at a time.

1. Runways are designated by numbers which correspond to their magnetic direction (rounded to the nearest ten with the last digit dropped off). For example a runway aligned east-west will be designated runways 09 & 27 or runway 09/27 denoting that operating in one direction aligns with 090 degrees and 270 in the other direction.

2. The Earth's magnetic poles do not align with its geographic poles. The magnetic north pole (where your compass points) is not in the same place as where you find the red & white pole about which the Earth spins or anywhere near where Santa lives.

3. The Earth's magnetic field changes over time in complex ways. Meaning that north on your compass today won't necessarily equal where your compass will point in the future (it should be fine tomorrow but give is 50 years and it will change).

Okay, from that it seems quite reasonable that we would change the runway designation as the magnetic variation changes. But we are missing something here, I think.

While the method by which we designate runway is based on magnetic variation and the method does provide a quick check that you are on the right runway, is that really why we give runways numbers?

I don't think so.

We did need a way of distinguishing runways from each other and using their general direction is a great way of doing this but I think the method has overtaken the objective in importance.

My first concern is with the change process. I have found pilots to be creatures of habit. The idea that one day a pilot would fly into a regular airport of theirs and find the runway number different, I think, introduces more risk than it addresses.

Plus, there are also some good reasons for not following this method of runway designation to the nth degree. Here are three:

  1. Generally, runways are aligned to prevailing wind conditions. This means that runways in an area are likely to be aligned in a similar, if not the same, direction. It would be a good idea then to designate the runways at airport A according to the "rule" and the runways at airport B. I am pretty sure this is the reason why the east-west runway at Essendon airport (in Melbourne, Australia) is "correctly" designated as 08/26 but the east-west runway at nearby Tullamarine is designated as 09/27 despite the fact that both runways are 3 degrees off 080-260.

  2. At some airports, the cross-runway design might be 100 degrees off the main runway. This could lead to a runway 03 and a runway 13 or a runway 07 and a runway 17. This, of course, could lead to confusion. Sydney International has this very problem and it has chosen to designate its cross runway as 07/25 instead of 06/24 to avoid confusion with its runways aligned to 16/34.

  3. Parallel runways are distinguished by either an L/C/R for the left, centre or right runway. If an airport has more than three runways then they will deliberately depart from the “rule” and designate one or more runways using a number higher/lower. You can see two different approaches to this at Dallas/Fort Worth and Phoenix Sky Harbor International Airports.

The problem of blindly following the method and not the objective is, in my opinion, rather common. When doing something, it obviously helps to ask why you are doing it and that answer should not be because the method requires it. It should be to address a risk.

Elmer Fudd