We have fielded a number of inquiries from our customers concerning the recent media reports about the condition of the runway at the Whitehorse airport. As the media discussion has raised questions from the traveling public, I thought that some additional information, from an operator's perspective, might help people to better understand the situation.
The first item in the media discussion related to slippery runways. Most Canadians will expect that airport runways are likely to become slippery from time to time during the winter. Airport operators use snowplows, runway sweepers, and sometimes even de-icing fluids in order to keep their runways as close to bare and dry as they can at all times. In my view, the airport operator is doing a great job of looking after the runways at the Whitehorse Airport.
A slippery runway can, in general, impact aircraft operations as follows:
- More runway length will be required for take-off in order to allow for increased stopping distance in the event that a take-off is rejected;
- More runway length will be required for landing in order to allow for increased stopping distance;
- Increased limitations will be imposed on allowable crosswinds for take-offs and landings.
Aircraft operators must account for slippery runway conditions on each take-off and landing and we rely on the airport to provide us with current runway surface condition information. In addition to information regarding any snow or ice covering, friction information is provided in the form of a friction index. Typically a friction index reading might be anywhere from .18 to .60 and this translates roughly into expected braking capabilities as follows:
|Runway Friction Index
The foregoing provides a rough rule of thumb. The actual calculation is done more precisely by relating the friction index to additional runway length required for take-off and landing. If the additional runway length is available, then there is no operational impact. If the runway is not long enough to account for the slippery conditions, then take-off weight or landing weight must be reduced. In some circumstances this could mean that one could not take-off or land until or unless the friction index is improved. Fortunately our runway in Whitehorse is long enough to ensure that slippery runway conditions almost never have an impact on our operations. The regulatory requirements ensure that safety margins are maintained even if the runway is slippery.
Again, with reference to Whitehorse, I feel that our airport operator works very hard to keep our runway in good shape. If we have experienced or are experiencing poor weather, the runway maintenance personnel are very diligent about getting right on snow clearing and sweeping operations such that, even if we start the day with a poor friction index, their efforts usually result in improved friction reports within a very short period of time.
The second item discussed in the media related to the location of the glide path at our airport. Whitehorse has one instrument landing system, or ILS, which provides horizontal and vertical flight guidance for runway 31L. In approximately 1999, our main runway (31L/13R) was lengthened from about 7250 feet to 9500 ft, mainly to accommodate take-off performance for international charter flights. Although lengthening the runway added almost 2300 ft to the take-off run available (TORA) for both runways, the landing distance available (LDA) was only increased to 8649 ft for runway 13R and 8099 ft for runway 31L due to the requirement for displaced thresholds at both runway ends. My understanding is that the requirement to displace the thresholds was driven by obstacles south and north of the airport and that the ability to relocate the glide path could also be impacted by obstacles south of the airport. I also understand that the ILS is due for replacement this year and the possibility of moving the glide path will be evaluated in conjunction with this scheduled work.
Hopefully the foregoing has provided some clarification to what has been reported in the media and has addressed any questions or concerns that our customers may have.
Joseph Sparling, President
Air North, Yukon's Airline