When does an airliner switch from using the tiller to steer to the rudder on takeoff? Same for landing- when does the pilot switch from using the rudder to the tiller? What is this process? Once a pilot switches to the rudder on takeoff, is there a lock for the tiller? I'd imagine that it would be necessary to have some sort of system to lock the tiller so the pilot cannot accidentally hit it at high speed on the ground. If there is a locking mechanism, does it actually lock the tiller or does it simply disconnect the tiller from the nose wheel leaving the wheel free spinning so it can move as the rudder makes slight corrections while taking off/landing? Please expand as much as possible! Thanks.
I flew for two 747 carriers that never bought new aircraft, and thus this answer applies to 747-100/200 aircraft as originally manufactured for a number of different airlines.
The tiller is active when the aircraft is on the ground and the nose gear is compressed regardless of groundspeed as I remember.
I've never heard of a pilot accidentally hitting it at high speed on the ground, but if they did it would scrub the front tires. It wouldn't appreciably turn the airplane.
Pilots did have to be wary of having their hand within the travel range of the tiller when a tug is being hooked up. Ground handlers would sometimes work the nose gear back and forth a bit, and that action is reflected in tiller movement. If they do it quickly, the tiller will snap quickly and a hand in the way will get hurt.
The nose gear is relatively weak compared to the rudder, the brakes, or the engines insofar as its ability to turn the aircraft. To make turns off a runway onto a taxiway that is 90° to the runway, you usually aim for a 10 knots or less groundspeed. You can do a little more depending on the runway surface and what your center of gravity is, but sometimes 10 knots can be too much. I once skidded the nose gear badly at Jeddah, Saudi Arabia at midday in the summer when I failed to account for the fact that hot asphalt is slippery.
To illustrate how poor tires are in preventing sideways scrubbing, consider the 747 body gear. 747s have body gear steering for tight turns, but you can dispatch the aircraft with inoperative body gear steering. You can still make tight turns, but not quite as tight, but you do it with engine power and just scrub the body gear around, all 8 tires with a lot of weight on them. You might have difficult doing that, though, if you c.g. is greater than 26.6% mac. That's where the wing gear is, and if you're aft of that (limit is 33% to 37% typically) you're got a lot more weight on the body gear. Body gear steering is disarmed for takeoff and landing though.
Barring a strong crosswind, the usual takeoff procedure was to not use the tiller unless you were doing a rolling takeoff, starting the power up before being aligned with the runway. Once aligned and moving the rudder will do it. Even in a strong crosswind, you can forget the tiller very soon in the takeoff roll.
On landing, no use of the tiller until down to taxi speed except maybe a little use for a strong crosswind just before reaching taxi speed.
Boeing offered a rudder pedal-nose gear steering link, but almost all 747s I flew did not have that. I flew a couple of airplanes that had it. It helped in a crosswind.
Depending on the manufacture of the aircraft (Boeing or Douglas) the use of the tiller or nose wheel steering is different. Douglas aircraft, like the DC-8 and DC-9, had limited nose wheel steering (15 deg) through the rudder peddles. These aircraft could be taxied to a limited turn radius with the rudder peddles as they were linked into the nose wheel steering mechanism. However, turns of more than 15 degrees needed the tiller (nose steering wheel) to accomplish the greater degree turn. On take-off the nose wheel steering was not normally used once the aircraft was aligned with the runway as the 15 deg. limit was enough to control the aircraft until positive rudder control was attained during acceleration. If the take-off was being made by the F/O, he had control of the aircraft from runway alignment through the entire take-off procedure. The Captain would only place his hand lightly on the nose wheel steering until positive rudder control was attained and the "80K call" had been made. This was done in the event of an engine failure below V1 and an abort was necessary. Boeing, like a B-707, had no such linkage. Moving the rudder did absolutely nothing until positive rudder authority was gained on the take-off roll; usually somewhere around 60K. Using the nose steering was necessary until the rudder became effective and, failure to do so, would most like put the aircraft off the runway unless the wind was calm. If the co-pilot was making the take-off in the B-707, he would call "I have control" once he felt the rudder could steer the aircraft and the Captain would then rest his hand on the tiller until the 80K call was made. When taxing a Douglas aircraft, the Captain could take his hands off the tiller (nose wheel steering) if needed, to accomplish a task that required both hands. Not so, in the Boeing. If left unattended even for a short while, the Boeing would invariably head off the taxiway until the Captain made a fast grab for the tiller to correct the wayward aircraft. One last note: Three engine ferries on the DC-8 were relative easy to accomplish because of the nose wheel steering through the rudder. However, the B-707 required a well coordinated crew effort and many B-707s were lost on a three engine ferry attempt due to poor control transfer.
SOPs in my company prevent the use of tiller above 20kts.(it’s a limitation)
Note that on our fleet rudder pedals can deflect the nosewheel up to 6deg (compared to 75deg on tiler), reducing linearly to 0deg at 130kts (Airbus 320), so there is still some limited turning authority until the rudder takes over.