# Why is a large flashing “X” placed on a closed runway at Reagan National Airport?

Runway 15 at DCA (Reagan National) is closed at night and other times. By "closed," I mean that airport management places a gigantic lit/flashing "X" in the landing zone of 15. I'd estimate the big "X" is 8 by 8 feet, at least. It's like one of those roadside trailer flashing signs, except it's a runway.

The flashing X is very evident to pedestrians, bikers, etc., on the Mount Vernon trail. It's not some bizarre national secret.

My question: Why, in the tightly controlled airspace of Washington, DC, would DCA need to roll out a giant lit "X" to keep planes from landing there?

As if the obstruction were not there, you could fly in? That doesn't calculate, given how tight the airspace is controlled.

Why does this airport in the center of the world's highest airspace security roll out a construction trailer with a big X to keep planes from landing there?

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All the answers were great. I chose the one with the links to external directives, and the photo of the X. I had no idea it was so big. – rwrwr2r23r Mar 14 '14 at 6:55

The standard way of marking a runway as "CLOSED" is to put a big giant X on it - for fields which operate at night that X needs to be lighted. The specifications for the runway closure marker are outlined in an FAA advisory circular (AC 150/5345-55A)

The purpose of the marker is to indicate that the runway is temporarily closed (either administratively, as is the case at DCA, or for construction/repair/maintenance). It is redundant with air traffic control measures (such as NOTAMs) indicating that the runway is out of service, in case some pilots didn't check NOTAMs or somehow managed to stumble into the airspace and happen upon the airport while it's closed. (Obviously in the case of DCA they would have other problems were they to wander blindly into the area without talking to anyone, but believe it or not it happens far more often than any of us would like.)

The big flashing X doesn't "stop" you from landing on the runway - it just tells you you really, really shouldn't be landing there. There is a United States Senator who has achieved some notoriety in the aviation community after landing on a closed runway.

The X is also quite a bit bigger than you think it is to ensure it's visible from the air (the arms are 14 feet long):

(I was looking for a good aerial photo of one at night, but unfortunately couldn't locate one. The intent is for the X to be about the same size as runway numbers so there's no good reason for a pilot to not see it.)

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I wonder if that sucker ever blows over from jet blast, or even just the wind? BTW, are these things set up far enough down the runway that someone turning off the taxiway in the wrong place (on to closed runway) would see it? Do they have lights on both sides? – Phil Perry Mar 13 '14 at 20:47
@PhilPerry The runway is closed to departures as well as arrivals, so jet blast shouldn't be an issue (I'd imagine they would get launched though). All the ones I've seen only have one "X" (facing the approach), but I've only ever seen them set up on the numbers (so someone taxiing in at the threshold would certainly see it in front of them). Xs can also be placed on taxiways/intersections to indicate that those are closed to prevent someone from taxiing onto/across a closed runway where necessary (e.g. for resurfacing). – voretaq7 Mar 13 '14 at 20:59
Regarding my question about turning onto a closed runway, I was thinking of the Comair 5191 crash in Kentucky a few years ago. Further reading of news shows the runway in question was apparently not actually closed at the time (was it?), and the crew simply turned wrong in poor visibility. However, my question stands as to whether a plane could enter a closed runway for takeoff, somehow missing the "X" marker, or are all taxiways set up that a plane taking off would have to literally run over the "X"? – Phil Perry Mar 14 '14 at 15:24
@PhilPerry Sometimes the X is just paint (or plastic stuck down on the taxiway/runway, like this one -- Normally a lighted taxiway barricade is also put up in such cases, which you can see behind the X in that photo. In the Comair 1591 case the runway was just "not active", so no X - Runway status lights & colored/switched lead-in lights would mitigate incidents like Comair1591, but they're not commonly installed (yet). – voretaq7 Mar 14 '14 at 16:12
Hmm. With a "flat" X like that, how is visibility while landing? I could see the whole runway being so foreshortened by the shallow angle of approach (and nose-up attitude) that it could be difficult to pick up an "X" like that, especially if you're not in a frame of mind to expect it. How about stretching the "X" vertically (along the length of the runway)? Does that work/is it done? – Phil Perry Mar 14 '14 at 17:24

Any time that a runway is closed, it is marked as such by an X on the runway so that pilots will know, visually from the air. At night it is lighted. This is an additional measure that is used to help protect people and equipment on the ground along with the aircraft if a pilot were to make a mistake and land on the wrong runway.

It is even more important than normal at this particular airport because the runway threshold for runway 19 is very close to that of 15 and they are on similar headings. The Jeppesen airport diagram even includes a note which says "Be advised some aircrews mistake runway 15 for runway 19" (although the one below doesn't include this note).

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This is particularly important at DCA because aircraft landing on runway 19 will either by flying the LDA 19 or River Visual 19 approaches if landing to the south.

Take a look at these approaches:

You'll notice that you approach the airport lined up with runway 15 until very close in when you follow the river and turn for runway 19. Having flown into this airport a number of times, it is easy to misidentify the runway if you are unfamiliar. Putting a big X on the runway when it is closed increases the situational awareness and helps identify the proper runway. You'll note in both procedures you must be flying visually to make the turn and identify runway 19, neither approach lines you up for that runway. There is no straight-in for runway 19.

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If you're in DC sometime, go to Gravelly Point Park for a great view of planes on this approach. maps.google.com/…) – rwrwr2r23r Mar 14 '14 at 7:00