You’re feeling pretty good as you descend towards your destination airport. Under Center’s watch, you’ve just checked the latest ATIS, briefed the advertised approach to Runway 27, and you’ve got your avionics all set accordingly. Center switches you to Approach. Your check in with Approach ends with, “…and I’ve got information Charlie.”
Approach responds, “Expect a visual approach to Runway 18 now. Advise when you have ATIS Delta.”
Sigh. You literally just checked the ATIS a few minutes ago. Do controllers just swap active runways around on a whim? What’s the thought process that goes into a runway change?
Blowin’ in the Wind
“Determination of the active runway(s) requires consideration of all known factors that may in any way affect the safety of takeoff/landing operations including the initial departure and the instrument approach phases of flight within terminal area airspace.” That’s straight from the Selecting Active Runways section (10-1-6 (b)) in FAA Order 7210.3BB, the Facility Operation and Administration regulations.
The most obvious of those “known factors” is, of course, the weather. Like a dog sticking its head out a car’s window, aircraft like the wind in their face. Also, like many of our furry friends, they aren’t fans of thunder and lightning. Consider the winds at your destination airport. ATIS Charlie had the winds at 260 at 14 knots. ATIS Delta now lists the winds at 19015KT. So, now Runway 18 makes perfect sense.
Ceilings play a role too. Imagine, as you’re inbound to the airport, an overcast layer rolls in at 300 feet. Runway 18 has an RNAV approach, but its decision altitude is 350. However, the ILS to Runway 27 has a decision height of only 200 feet.
Which has higher priority: avoiding a 15-knot crosswind component, or actually getting under the clouds and seeing the runway? I’d say the latter. One condition makes it more difficult to land, but the other makes it impossible. This might be a situation where Tower can get creative and opt to depart aircraft on Runway 18 into the wind, but use 27 for arrivals due to the ceiling.
Dangerous convective weather systems also force runway changes. Is there an intense thunderstorm plopping itself on a runway’s approach path? Time to use a different runway. Fronts or squall lines sweeping across an area also impact wind direction, often leaving controllers “chasing the wind” to keep their active runway lined up appropriately.
What are non-weather considerations? Perhaps airport maintenance needs to do some repair work or replace lights. I’ve even seen runway closures for edge grass mowing. Then there are unusual circumstances or incidents. If an aircraft suffers a gear collapse on a runway, that runway’s closed, of course. Alternate runways must be used to keep traffic moving.
Taking the Helm
Once conditions necessitate a runway change, who actually initiates it? The personnel in the air traffic control tower (ATCT) at the airport in question. Our 7210.3BB spells it out in 10-1-6 (a): “ATCT supervisor/CIC [Controller-incharge acting as a supervisor] has primary responsibility for determining which runways are to be designated as ‘active’ runways.”
Of course, no airport is an island. What affects one facility affects others around it. A departing aircraft is first handled by Clearance Delivery, then Ground, then onto Tower, who in turn feeds them to Departure. Departure will eventually hand them to Center. Arrivals reverse the process: Center > Approach > Tower > Ground. A runway change impacts each of those personnel, and naturally the aircraft being handled by them.
Like many tightly-knit workplaces, air traffic control facilities use internal slang that may sound odd to an outsider. To us controllers, when we hear, “We’re swinging the boat around,” a runway change is afoot. And this boat’s no 13-foot Boston Whaler runabout; depending on the airport, it’s more like a 100,000-ton Gerald Ford-class nuclear aircraft carrier and its entire multi-ship task force. A lot of mass, people, and moving parts need to shift direction all at once.
The potential for chaos is great. Personnel in the tower, the approach controllers working its arrivals and departures, and—depending on the size and configuration of the airport—the center overlying them must all be notified.
How does ATC get that message across? We use accurate coordination, and, yes, an official checklist. Section 10-1-6.a. adds: “A facility directive must be issued to define specific coordination requirements.” The runway change procedures are spelled out in a facility’s internal standard operating procedures (SOP) and letters of agreements (LOAs) between facilities.
Choose Your Moment
How does that coordination go down, and how do we take into account the status of each aircraft under our watch? Let’s walk through the process. We’ll start by rolling the clock back a few minutes from when you checked in with ATIS Charlie.
I’m working Ground, Clearance Delivery, and CIC combined at your destination airport. We’ve been on Runway 27 but the winds have swung south and airplanes on final are crabbing pretty hard. I’ve got two aircraft already taxiing to Runway 27 for departure and an airliner just starting push off his gate.
I examine Tower’s radar display. No one’s on final, but Approach has a couple arrivals on a left downwind for 27. The last one is doing 180 knots and has about 15 flying miles to the runway.
Much of what we do is based on time. For sequencing and speed control, we use miles per minute, not miles per hour: 180 knots ÷ 60 minutes = 3 miles per minute (mpm); 15 flying miles ÷ 3 mpm = 5 minutes before that second aircraft lands on Runway 27. It’ll probably be a bit more since aircraft slow on final, so call it seven minutes.
The next closest arrival is, well, you. You’re forty miles out, about to enter Approach’s airspace. Radar shows you at 150 knots, or 2.5 mpm. So, you’re (40 miles ÷ 2.5 mpm) 16 minutes away. That gives us a nine-minute window during which we can easily switch the active runway. So, let’s get cracking.
Talk Amongst Yourselves
I turn to my friend on Tower. “Looks like those winds are staying out of the south.” I point to the two aircraft already taxiing. “Are you good with changing over to Runway 18 after these two go, and the two on the downwind land?” I ask in case there’s some detail I’m missing that would preclude changing runways right now. That’s part of our crew resource management.
“Yeah, I was watching that too,” he says. “Let’s do it.” Cool. We’ve got a unanimous decision in the tower. However, we are not alone in this. I need to follow our checklist and coordinate, beginning with notifying our approach control.
I key up a recorded landline to Approach’s supervisor. “We’re looking to go Runway 18. I’ve got two departures taxiing to Runway 27. What do you guys have?” Again, for CRM, I’m looking for a reason not to go to Runway 18.
He puts me on hold to check with his radar controllers. A minute later, he’s back: “Okay, we’re good. Last arrival to Runway 27 will be N123AB, the second guy on the downwind. First arrival to Runway 18 will be [He gives me your callsign]. Who’s your last Runway 27 departure and first one off 18?” I give him the callsign of the second aircraft taxiing out to 27, and inform him my initial departure off 18 is the airliner pushing back. Now we have a defined start and stop point for each runway.
“Okay,” the supervisor says, “call for release off Runway 18.” Normally our airport has automatic departure releases, i.e. we can just launch aircraft as long as they’re on agreed-upon headings and altitudes, and approach is notified they’re coming via a landline call or their callsign flashing on their radar scope. However, a runway change is a sensitive time. Therefore, “automatics” go away. Before departing someone off Runway 18, Tower must call for a verbal release.
The supervisor then calls our overlying center. Center’s staff reconfigures their computer automation so our departures off the new runway will automatically hand off to the appropriate radar sector. They’ll also notify the center controllers themselves, who have their own procedures to follow.
Roping Everyone In
Until now, it’s all just been talk—pure internal coordination. No aircraft are aware a runway change is in progress.
My CD duties include recording the ATIS. However, that takes a couple of minutes and I’m looking at the airliner pushing back. Its crew needs to know as soon as possible, so they can run their performance numbers and configure for the new runway. I tell them, “Expect Runway 18 for departure. ATIS Delta will be up momentarily. Airport winds 19015KT. Altimeter 3001. Advise ready for taxi.” They acknowledge and tell me they’ll get Delta.
Speaking of which … I grab the ATIS handset and record ATIS Delta. Then, I update the info screens in our tower with the new runway and ATIS letter, then tell my Tower comrade, “Delta’s up.” We both make a general broadcast on our frequencies. “Attention all aircraft. ATIS information Delta current. Altimeter 3001.” I’ll often add, “Runway 18 is now the active.” Anything to minimize surprises, right?
Approach must also be told we’ve officially changed. Via landline, I advise them, “ATIS Delta’s current. Visual approaches to Runway 18.” If their information displays aren’t linked to Tower’s, they must update their own screens to reflect our new ATIS letter and runway. Radar scopes are configured to display appropriate airspace maps. Each radar controller makes their own general broadcast, “Information Delta now current at [airport]. Altimeter 3001.”
Right after they make that broadcast, you check in on Approach with Charlie. The radar controller has a responsibility to ensure all aircraft have the latest landing and weather information for destinations in their facility’s airspace. That’s when he informs you Runway 18 is now active, and advises you to get information Delta. He’ll, of course, vector you and subsequent arrivals for the new runway.
Over at Center, their controllers are also adapting. For instance, when we were on 27, jet arrivals from the east were slowed to 250 knots, so they’d be able to descend out of 10,000 immediately upon crossing Approach’s airspace boundary. Runway 18’s final is further away from that eastern boundary, so eastern arrivals are no longer restricted. However, jets from the north—dumping straight in to Runway 18—must now be issued that 250 knot speed restriction by Center.
Meanwhile, our last two departures have just taken off from Runway 27, and the last arrival to 27 is rolling out. The airliner is holding short of Runway 18, but Tower can’t just launch him immediately. We’re still under a “call for release” order. Tower calls Approach. “Request automatic releases off Runway 18.” His request is approved, and he clears the airliner for takeoff.
A few minutes later, you check in on Tower’s freq. They say, “Cleared to land Runway 18.” Every element of the runway change is now complete!
All airports—large or small—have their own challenges when it comes to runway changes. Atlanta’s Hartsfield- Jackson is a beast to turn to around with its five parallel runways and inbound jet traffic lined up across multiple states. A small Class D may have to herd a pattern of inexperienced student pilots onto a new runway.
Adapting to new conditions is just part of the aviation experience. It takes attention to detail, decisive action, and good situational awareness to ensure a change goes smoothly for those in the control rooms and the cockpit.