Holy Shit, that Incoming Plane is Getting Big!

October 15, 2009 10:24 AM

Are air traffic controllers "pushing" it more?

On a recent flight out of San Francisco, on Columbus Day, as day of severe rainstorms in the Bay Area, the regional jet I was on was taxiing into position. Out the right side of the aircraft, I saw the lights of a larger airliner approaching, seemingly seconds away from landing on the same runway we were queued up for.

I commented to my wife that, surely, this plane would touch down and then we would get on the runway and take off. Instead, our plane made a quick left turn, and, without stopping, accelerated, gained speed and took off. When we banked, I looked down and saw that the other place had already slowed down to a taxi on the runway we had just left. It seems like, if our plane had had any delay, then the other plan would have had to pull up, drastically, to avoid us.

Does anyone have any knowlege of protocols and procedures dealing with this? It really seemed like an "iffy" move, and I was going to ask the flight crew, who usually line up and say goodbye, but they were not there when I deplaned.

posted by Danf to travel & transportation (14 comments total)

SFO has two sets of parallel runways. The plane was probably landing on the runway next to the one you took off from. Are you sure that wasn't the case?
posted by zsazsa at 10:31 AM on October 15

Are you sure it was the same runway? SFO has two parallel runways going N/S... which is how you can get tableaus like this seemingly dramatic moment.
posted by Cold Lurkey at 10:35 AM on October 15

It was our runway. They only had one set of runways in operation for both arrivals and departures (due to the weather), and I am quite certain that it was the one we were on, the west runway on the only pair they were using.
posted by Danf at 10:38 AM on October 15

That sounds pretty common. ATC has a pretty good idea of how long it'll a) take you to leave and b) take the other aircraft to arrive. The one risk to this maneuver is if your departing airplane needed to abort the takeoff or otherwise had some mishap on the runway; in that case, the arriving aircraft would likely be instructed to go around and hold somewhere. In good weather, large airports like SFO can handle traffic on the order of one arrival or departure every 30 seconds to a minute.

Once you're off the ground, there's not any risk in letting someone else land. Engine failure is the only thing that would prevent the aircraft from continuing its outbound climb, and in that case the most deadly thing the pilot could do is try to turn around and land again.

There was a comment awhile ago from someone describing an "expedited" departure, but I can't find it right now. Basically, a waiting aircraft was given a sort of "immediate go" to takeoff, but if they took too much time on the runway were instructed by ATC to abort, get off at the first taxiway, and try again. That's a maneuver for very high congestion, though.
posted by backseatpilot at 11:10 AM on October 15 [2 favorites]

Oh, and as far as I'm aware, the only restriction that I've ever personally encountered with ATC is basically that two aircraft may not both have wheels on the same runway at the same time. As soon as you're not on the ground anymore, that runway is free for the next plane.
posted by backseatpilot at 11:12 AM on October 15

AND! (And I really need to think more before hitting post...) And, the economic downturn has meant fewer flights anyway, so compared to, say, five years ago there is no reason to be running things tighter. Chalk it up to confirmation bias, I think.
posted by backseatpilot at 11:14 AM on October 15

Your Google search should be "Cleared for immediate takeoff". That's the ATC command given to pilots with another aircraft on short final.
posted by hwyengr at 11:21 AM on October 15 [1 favorite]

From the ATC manual (PDF), section 3-10-3.

Separate an arriving aircraft from another aircraft using the same runway by ensuring that the arriving aircraft does not cross the landing threshold until one of the following conditions exists: ... 2. The other aircraft has departed and crossed the runway end.

And further, that the separation only needs to be 6000 feet, as long as the taking off airplane is airborne. 6000 feet is significantly shorter than SFO's longer runways which are 10,000+ ft.
posted by smackfu at 11:36 AM on October 15 [1 favorite]

It's a bit out of date, but I recommend reading this James Fallows article from 1997 on Air Traffic Controllers, which discusses the idea of whether or not the skies are becoming more or less dangerous.
posted by ecab at 11:45 AM on October 15 [3 favorites]

There is a commom misconception that aborting a landing, or what is more commonly known as a "go-around", requires an aircraft to "pull up, drastically". Going around in a modern jet transport is less problematic than a normal takeoff, mainly because the aircraft already has a reserve of both potential and kinetic energy, and the engines are "spooled up", requiring less time to reach TOGA (takoff/go-around) thrust than they do on takeoff. This is what makes the go-around seem so much more dramatic to passengers. The thrust is available in a few seconds, and there's no long takeoff roll involved; rotation to go-around attitude is possible almost immediately.

What can be a little interesting in the scenario you describe occurs when the landing aircraft has to go around for insufficient spacing but the departure aircraft still gets airborne. Unless somebody does something, its going to be a little crowded on the takeoff corridor. It's a simple matter, however, for the tower to sort things out by giving one or the other, usually the go-around, a slight turn. Also, remember that the go-around is climbing only to traffic pattern altitude, while the depature is climbing out of the airport airspace.
posted by dinger at 12:15 PM on October 15 [1 favorite]

This may be the previous post backseatpilot was referring to.
posted by dinger at 12:24 PM on October 15 [1 favorite]

It seems like, if our plane had had any delay, then the other plan would have had to pull up, drastically, to avoid us.

The other plane would have been instructed to "go around" which is a standard maneuver that pilots are taught from the very first days of their primary training. It might feel sudden or unusual to the passengers, but it's not an inherently dangerous maneuver, and in a situation like the one you describe, the incoming pilots would have been especially alert to the possibility of a go-around since they could easily see your plane on the runway while they were on short final.
posted by Nothlit at 1:55 PM on October 15

You've gotten some good answers already, but I thought you might be interested in this NTSB reconstruction of a near miss at LAX. It shows just how late in the approach even a large aircraft like a 747 can initiate a go-around.

While it's not the same situation as yours (in this video somebody did make a mistake), the point is that even if your aircraft is cleared for immediate departure and then has some problem where it ends up stuck on the runway, it's still safe as long as the crew of the approaching aircraft can see what's going on. If visibility isn't good, they're more conservative about this kind of this kind of procedure.
posted by FishBike at 3:08 PM on October 15

Are air traffic controllers "pushing" it more?

Probably not in the sense you mean -- trying to squeeze in more planes than they should. There are actually protocols and standards for this sort of thing and ATCs are normally very regimented and precise people who have much less discretion than you might think.

Sometimes they do screw up. In their lingo, this is a "deal" and it can hamper or end a career. Usually these are problems during a hand-off, either as a plane moves from one sector of control to another, or when a controller hands his duties to another so he can go off shift or take a bathroom break. Sometimes they're communication errors, like talking to the wrong plane or failing to get confirmation. In any case, when something happens that falls into the "near-miss" category at a major airport, it frequently gets in the papers. It's impossible to tell whether what you saw was a deal or not -- we can't even be sure you're describing it correctly (no offense). But planes at major airports are scheduled fairly tightly. At O'Hare you can see them lined up in one-minute intervals all along I-90 out into cornfield territory. They seem close, but other than turbulence issues (when a plane follows a "heavy" -- large jet -- as in the Flight 587 crash).

That said, there are issues to be concerned about. The FAA is experiencing a wave of retirements. This is directly related to the hiring of 8000 ATCs following the firing of the existing controllers by President Reagan because they were on strike. These new controllers are now vesting their federal pensions and retiring. It's estimated that the FAA will have to hire around 15,000 new controllers through 2017 to make up for this attrition, which actually started around ten years ago.

Here's a report this year on staffing levels at key California airports. And according to a public database (dated 2007), while SFO was authorized for up to 35 controllers, it only had 26 plus two trainees. That situation has probably not changed a lot.

So there's an outside chance that you had a trainee, or a seasoned controller who was just working too many hours, and there was a slight maybe almost deal. I wouldn't leap to that conclusion, though; I think it's more likely that as a civilian you just aren't familiar with the appropriate clearances and timings.
posted by dhartung at 7:27 PM on October 15