"I guess he's just headin' in," said the tower controller. I visited my home base airport's control tower a couple weeks ago. The tower controller, or local controller in ATC terms, and I watched as a Cessna 172 landed, exited the runway, and taxied to his parking location without saying a word. The controller, not wanting to fill out a bunch of paperwork near the end of his shift, quickly keyed up and issued the aircraft taxi clearance. The pilot acknowledged, his voice sounding a bit caught off guard by the taxi clearance, perhaps because he didn't understand that he had unwittingly just committed a violation.
This happens all the time. Go park yourself near the sidelines at a busy GA airport with a control tower and count how many airplanes taxi off the runway after landing and continue to their parking location without clearance. Controllers get used to this, and in the interest of maintaining a healthy blood pressure level, they usually don't chastise the unknowing pilots and simply issue a taxi clearance. Sometimes they ignore the violation altogether. But taxiing from a runway to a parking location requires clearance from ATC, just like taxiing from a parking location to a runway for takeoff. Certainly, most pilots wouldn't start-up and taxi out to a departure runway for takeoff without contacting ground control for taxi clearance. Why, then, do they taxi along the same active taxiways in the opposite direction without clearance after landing?
When a controller clears you to land, the runway is yours. Not the entire airport movement area (including the taxiways you plan to use to transition from the landing runway to parking). A taxi clearance must be received after landing, even if the taxi is short and simple. That same taxi required a clearance before takeoff, and it requires a clearance after landing. Other aircraft may be moving about the surface communicating with ground control. Taxiing off the runway after landing and continuing straight onto another taxiway may put you head-to-head with another aircraft. That can create a headache because aircraft can't go backwards, and on narrow taxiways there may be insufficient room to accommodate a 180 degree turn. A shutdown and tow may be required to remedy the situation.
Remember, you must be cleared to taxi before you move anywhere on a designated movement area. That's true whether you're taxiing out for takeoff, taxiing from point to point on the airport surface, or taxiing to parking after landing. Sometimes taxi clearances are extremely short. "Skyhawk 123, taxi to parking." That's a taxi clearance. Three words. The term "taxi to" means you choose your taxi route. You can use any taxiways or inactive runways you desire, just not an active runway. The FAA has recently mandated the issuance of explicit taxi instructions at many airports, meaning controllers are no longer permitted to use "taxi to" clearances. An explicit taxi instruction contains a specific taxi route, but it can still be short. At my home base, I often get the taxi clearance, "Taxi to parking via Alpha." That's still short but explicit because it contains a specific taxi route. No matter what the case, you've got to have a clearance in one form another before taxiing after landing.
The proper procedure is to land and exit the runway as soon as practicable. Always exit onto a taxiway, never an intersecting runway unless specifically instructed by ATC. Pull your entire aircraft clear of the hold short lines and stop, then await further instructions from ATC. Never change to the ground frequency unless instructed by the tower. That's another common mistake I've seen. Some pilots switch from tower to ground automatically after exiting the runway. Don't do that. Stay on tower, give the controller a second to issue you further instructions, and if he doesn't, query him. At that point he'll either issue you a taxi clearance or hand you off to the ground controller. The ground controller will then issue a taxi clearance. If the tower controller issues the taxi clearance, stay on his frequency for the entire taxi unless he specifically instructs you to contact ground. When requesting taxi-in clearance, use the same format you'd use if calling for a taxi clearance for takeoff. It should sound like this, "Denver Ground, Skyhawk 123, clear of 35 Left at Mike 6, taxi to GA parking."
Taxiing off a landing runway and onto an active taxiway is taxiing without clearance. It's a violation and can get you into trouble. So, remember, pull across the hold lines, stop, and await further instructions.
