Runway numbering at YSSY

[Philip Argy]

This may be a very dumb question, but why is YSSY runway 07-25 not designated 06-24 given its orientation of 62/242 degrees? Is it because when it was first named the measurements were less accurate or is it just magnetic variation over time, or some other explanation?

I did look first at clause 7.10 of Chapter 11 of CASA's Rules & Practices for Aerodromes:

7.10 The runway designation marking is to consist of a two-digit number. The number is to be derived from the magnetic bearing of the runway centreline, when viewed from the direction of approach, rounded to the nearest ten degrees. If a bearing becomes a single digit number, an `0' is to be placed before it. If a bearing becomes a three-digit number, the last `0' digit is to be omitted. For parallel runways appropriate letters L(left), C(centre) or R(right) are to be added to the two-digit number.

It doesn't say rounded "up" to the nearest 10 degrees, but is that the conventional interpretation? Runway 16-34 has a true orientation of 155/335 degrees so it complies with both interpretations and therefore doesn't assist in resolving any ambiguity.

[Phil M]

I'm not sure about Sydney specifically, but I believe the numbers don't have to be accurate for runway designators.

For example, the old 36/18 at Bankstown was about 342 degrees, but there were too many 34's in the Sydney basin, and then with 35/17, it would have looked too much like 11, so they went with 36/18.

Maybe something like that for Sydney too?

[David Ramsay]

Consider LAX with four parallel runways, all 249 magnetic, 263 true.

25L, 25R, 24L, 24R.

[Adrian B]

Ithink I have seen the reason before on ye olde board. Nigel can probably advise.

[Nigel C]

If they were using both Rwy "06" and "16" simultaneously, or indeed Rwy "24" and "34" together then there's a great potential for confusion, hence Rwy 07/25 was used.

Furthermore, the Airfield Operations team at Sydney don't use the callsign "Car 7", and don't use "Car 16" for works related vehicles for the same reason.

[Adam P.]

And here's me thinking you lot just couldn't count, Nigel.

[Nigel C]

We can't...we're just told what to say!