# Should you wait to switch to the ground frequency until after crossing a runway?

I've never had the opportunity to fly into a controlled airport with parallel runways, so I've never actually faced the situation. But, in the interest of being ahead of it, when would it be prudent to switch to ground frequency with this clearance (assume I just landed)?

N12345, right on E, cross 27 R, contact ground .9

Should I call ground (or switch frequency, so I no longer hear the tower) before or after crossing 27 R? My by-the-book assumption would be immediately, as there's no "then" or "after crossing" or similar, but somehow that feels wrong. I suppose normally it doesn't really matter, but in the case of someone (which includes me, everyone makes mistakes) doing something wrong, where would they call me as I'm about to cross 27 R?

The reason I ask is that I saw exactly this case in a YouTube video quite a while ago (can't find it anymore though), where exactly this happened. The pilot was narrating for the video and stated he'd switch frequencies "now that he'd crossed the runway", at which point I started thinking about it.

Considering the situation, I would probably rather wait since there's an inherent delay when switching frequencies anyway, I might as well wait a bit longer, but knowing myself, if I hadn't thought about it ahead of time I'd probably switch right away. The only reason I can think of for saying it this way is if 27 R is not an active runway, but then again, reality does not always match what's in the book.

Remember that active runways are always the jurisdiction of the local (tower) controller. Even if a ground controller tells you to cross a runway, they have to clear it with the local controller next to them. So generally you switch frequencies when you have finished crossing the runway unless told otherwise.

I can tell you this is exactly how it works in Boise, Idaho where there are the parallels 10/28 L/R.

However, if you are unsure of any instructions a controller gives you, the basic rule is: ask. The tower controller won't mind, and will typically appreciate the clarification. Just read back the crossing instruction as normal, then ask.

Right on E, cross 27 R, contact ground .9, N12345, and should I contact ground on the other side of 27R or immediately?

• This is how I have always done it. In general, unless specifically told otherwise, I would keep talking to the guy who gave you the clearance to cross until you are actually on the other side just in case a situation develops and they need to contact you in a time critical manner. – Lnafziger Dec 25 '13 at 18:25
• and make sure your tail is completely clear of the hold short line! – rbp Feb 27 '15 at 22:55
N12345, right on E, cross 27 R, contact ground .9


Do it in exactly the order they tell you. Right turn on E, cross the next runway, then stop and contact ground.

Have an airport diagram handy if you can, it will make a world of difference.

ETA: If they want you to switch to ground before crossing 27R, they'll probably just say this:

N12345, right on E, contact ground .9


In which case, you turn right on E, cross the hold position lines, stop, and switch to ground. The ground controllers will direct you the rest of the way, coordinating with tower controllers where crossing runways is required. In fact, in this case, they'll probably give you very explicit instructions not to cross any more runways until told to do so.

• The thing is, if you'd for example gotten an enroute clearance, "climb and maintain 6000, contact duckburg center 123.4" you're not supposed to wait until you're at 6000, you're supposed to contact duckburg now, unless you actually get "climb and maintain 6000, reaching 6000 contact departure" or something similar. – falstro Dec 18 '13 at 19:09
• Hmmm; good point. Any controllers here? – Edward Falk Dec 18 '13 at 19:55
• I'm not a controller, but I just about guarantee the second option would be accompanied with a "hold short 27R." The FAA is doing everything they can think of to eliminate runway incursions. – Matt Young Jan 1 '14 at 4:42
• Very good point. – Edward Falk Jan 1 '14 at 5:06

Different airports will have different procedures. In some instances, exiting a runway and joining a taxiway upon landing means you should immediately contact GC. In others, ATL for example, you shouldn’t ever change frequencies until instructed to do so. Reason for that is that in ATL local control owns jurisdiction over certain taxiways - B, N and to a lesser extent R and points south. Jumping frequencies here without instruction will lead to lost comms, and is a common issue among pilots not familiar.

As to the you-should-never-cross-an-active-on-ground point made earlier - not accurate. We routinely coordinate among each other to cross runways if an advantage can be gained by doing so. I probably cross 30 aircraft a week on ground control frequency.

• Welcome to Av.SE - good to have more active ATC controllers on the forum! – Ralph J Mar 6 '19 at 3:01

You have been cleared by the tower to cross a runway so you should stay with the tower frequency until you've crossed it. The reason being that ground control is not authorized to issue clearances for runway crossings.

In theory, you should never cross a runway when on ground frequency because the tower is in charge of that.

• The ground controller is however authorized to order me to stop, effectively canceling the crossing clearance, isn't he? Also, I've had numerous runway crossing clearances delivered on ground frequency, probably issued by the local, but still, your last statement doesn't add up, I shouldn't switch to tower just because I'm about to cross a runway, should I? – falstro Dec 17 '13 at 23:08
• Crossing a runway while on ground frequency happens quite often. The ground controller simply authorizes it with the local controller first. You shouldn't switch frequencies while crossing unless told to do so. – Bret Copeland Dec 17 '13 at 23:51
• What if the tower clears you to cross and for some reason has to stop you. If you're already on the ground frequency that could cause a problem. Personally, I wouldn't switch to ground until after crossing the runway. – Philippe Leybaert Dec 18 '13 at 0:39
• The scenario I gave in the comment is when ground clears you to cross, not tower. – Bret Copeland Dec 18 '13 at 5:29
• @BretCopeland You're right. It seems I wasn't wearing my reading glasses :-) However, in the situation described by the OP I would never switch to ground until after crossing the runway. – Philippe Leybaert Dec 18 '13 at 20:04

When you're given a clearance related to a runway, you need to stay with whoever gave you that clearance until you're clear of that runway--and only then do you follow an instruction to change frequency.

Why? If Tower needs to cancel or amend your clearance, they will first try to reach you on the same frequency. If it's an emergency, the several seconds it takes to realize you're not there and then several more seconds to have someone else call you on another frequency could mean the difference between you living and dying.

Imagine, for instance, that tower told you to cross the right runway, and then they realized the aircraft behind you was (incorrectly) lined up on the right instead of the left. They're going to tell them to GO AROUND, of course, but they're also going to tell you to either STOP IMMEDIATELY or NO DELAY (i.e. full power), depending on exactly where you are. You really don't want to miss that instruction, especially since someone who's dumb enough to line up with the wrong runway is probably also dumb enough to miss (or mess up) the go-around.