When the fog rolls in - how we keep flights moving
Auckland Air Traffic Controller Geoff Feisst explains how controllers keep flights moving at Auckland Airport during foggy weather.
Fog is a challenge for aviation operators worldwide and this year in Auckland we’ve been experiencing fog more often than usual. Fog season generally runs between April and November and in Auckland we typically experience about eight to nine fog days in a season. This year we’ve already had seven.
When visibility reduces to less than 2000 metres, or the cloud base is below 300ft, special low visibility procedures come into effect at the airport.
Fog is most challenging for aircraft taxiing, taking off, or landing.
The job of our tower controllers managing aircraft is very visual and relies on them being able to see the aircraft on the ground at the airport and in the air. During low visibility operations we depend on our equipment and some clever technology to help us keep aircraft moving safely.
At Auckland Airport we have a Category III Instrument Landing System (ILS). The ILS sends out a signal which guides aircraft down onto the runway. It is always in operation at the airport but becomes even more important when pilots haven’t got a clear view for landing. For a pilot, they may not see the runway until they actually touchdown.
The ILS is a pretty sophisticated piece of technology and was installed along with an enhanced airfield lighting system to ensure long haul flights could land here, which greatly reduced the likelihood of them having to divert to other airports and disrupting the airline schedules.
Auckland Airport is one of only three airports in the southern hemisphere that we're aware of to have a system of this standard in place.
When visibility is low, we need to have fewer aircraft moving around the airport to ensure nothing interferes with the ILS signal. This means spreading out the spacing between landings and take-offs, which slows things down.
The navigation equipment on most domestic jets and international aircraft, along with the certification of their crews, means most aircraft can operate in these conditions using the ILS. Most turboprop aircraft do not have this equipment, and this is why fog mostly affects regional flights.
On the ground aircraft are guided by an advanced lighting system. It’s essentially a set of traffic lights embedded in the ground to divide up the taxi ways. Aircraft sit at these hold points and once cleared by the controllers, pilots move forward when the red lights go out.
While fog slows things down, with these systems and others we’re able to handle about 22 to 25 arrivals and departures every hour. Before having this equipment, if we could not see the aircraft, we could only safely move one at a time, around six aircraft movements per hour.
This year is turning out to be one of the foggiest in a while and I’m sure we’ll be seeing fog in the headlines again soon. For us the focus continues to be on getting you from A to B as safely and as quickly as possible.