MARITIMES SCANNING SITE
RUNWAY DESIGNATIONS and USAGE
Last revised March 17, 2010
Every airport for fixed wing aircraft has runways, even those for floatplanes!
Each physical runway is considered to be two runways, depending on the direction of movement. Thus 05 and 23 are physically the same runway but there are two designations depending on the direction.
Runways are designated by the magnetic bearing rounded to the nearest ten degrees and then divided by ten. A runway aligned 122 degrees magnetic is rounded to 120 and divided by 10 to yield the designation 12, stated properly as "one-two", not "twelve". Some are in the range 010 to 090 degrees rounded, and here in Canada, when divided by ten are properly designated as 01 to 09, not 1 to 9 which is the normal in the USA. It is very common to hear American pilots refer to runway 05 at Halifax as runway 5, even when the controller is calling it 05. Speaking of controllers you will now increasingly hear the controller also referring to "5" which is perhaps just another example of creeping Americanism.
Runway designations change over time. This is due to the slow movement of the magnetic poles. The magnetic bearing of a fixed object will therefore change over time. The runways at Halifax were until the early 2000's all one digit higher. For example runway 32 was runway 33! The change of designation is infrequent because as you know the designation covers ten degrees of bearing. For example the designation "Runway 14" covers all bearings from 135 to 144 degrees. In our area the magnetic bearings are slowly lowering due the north magnetic pole moving. A Runway 27 with a bearing now of , for example, 272 degrees will not be changing to "Runway 26" until the magnetic bearing lowers by 8 degrees to 264 degrees, which will take a long time. One that is already near the boundary may be about to change in the upcoming months. This is why they changed at Halifax at that time but they did not change at all airports.
The actual headings of the runways at Halifax are currently 144 degrees for Runway 14 and 054 degrees for Runway 05. You will note that this pair of runways are exactly perpendicular. Keep in mind that the opposite direction on these runways will be the reciprocal bearings. You will see from this that the two headings are just under the threshold' i.e. they just moved under the 145 and 055 bearings that formerly made them Runways 15 and 06, and it will be a long time before they get down to 134 and 044 necessitating the next revision.
At some airports outside the Maritimes there are parallel runways and these are suffixed by L and R. Thus at Anytown Airport there might be a Runway 14L and a Runway 14R, with the reciprocals being of course 32R and 32L respectively. Notice that the Left in one direction is the Right in the reciprocal. In a very few airports there may be a third parallel runway with the suffix C.
There is another suffix possible, for helicopter usage. Some heliports have actual runways, albeit short in length, rather than pads. Shearwater has Runways 16H and 34H, which of course is physically just one runway. The designation may seem to be superfluous if it is already known that the particular airport is just for helicopters, but it is perhaps more useful at Shearwater as there is also a full-length Runway 16/Runway 34 parallel, though currently closed.
Runways are aligned as they are for two reasons. In theory they match the prevailing winds. If the predominant wind is from a direction of 210 magnetic then it would be good to have a runway lined up with that as it is best to takeoff and land into the wind. The result would be Runway 21 with a less used reciprocal of 03. Of course there are other factors such as the shape of the land parcel the airport sits on, and as well considerations for terrain and for residential areas. There are many airports with just the one runway, but just as many with a second one that might be termed the cross wind runway. Often it will be shorter and less often used. Frequently it will be perpendicular to the main runway, but not necessarily. In earlier days and mostly at military bases there was a triangle pattern where there were three runways at 60 degrees of angle. It is almost a certainty when you encounter a triangle of runways on an aerial photo that you are looking at a current or former military base; though in many cases one or more of the three runways might be now abandoned. This is the case at Shearwater, Greenwood, Summerside, Chatham (Miramichi), and the former airfield at Pennfield Ridge.
At Halifax the usage of the two physical runways (four designated runways) varies. Naturally this depends on the wind direction at the time, but also there will be some tolerance for cross winds in order to reduce travel in taxiing or in flight. The flying part is the most important due to fuel consumption and time. For example a pilot heading to Charlottetown might prefer to take off on Runway 05 so that the aircraft is heading straight to destination on takeoff, and when coming back from Charlottetown will prefer the reciprocal which is Runway 23. Less turns ... much more straightforward. You might hear that the active runway is 14 but a pilot asks for 23. The controller will decide if that is reasonable or not and give an answer based on wind, runway condition and traffic.