dcaord
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Steering Plane On The Ground

Wed Jun 26, 2013 1:57 am

I know that planes have some sort of tiller to steer on taxiways, but i've always been amazed how planes are always so centered on the taxiway lines. I have to imagine its pretty difficult to see when steering a large aircraft. So how are they always so precise?
 
BoeingGuy
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RE: Steering Plane On The Ground

Wed Jun 26, 2013 2:40 am

Quoting dcaord (Thread starter):
I know that planes have some sort of tiller to steer on taxiways,

The 747, 757, 767 and 777 have tillers. The 707, 727, 737 and 787 have basically 1/4 of a steering wheel. It's like steering wheel but only 1/4 of it, so you hold the outside of it. Airbus has something similar to the 1/4 steering wheel, but with only one side and the top to hold on to. In other word, it's shaped like an upside down "L".

Boeing airplanes can steer up to about 7 degrees with the rudder pedals. That's for takeoff and landing roll and long straight taxis, but not nearly enough for sharp turns.

I didn't answer your original question, but it gives you a better idea of what the pilots use to steer.
 
PGNCS
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RE: Steering Plane On The Ground

Wed Jun 26, 2013 3:26 am

Quoting dcaord (Thread starter):
I have to imagine its pretty difficult to see when steering a large aircraft. So how are they always so precise?

Some aircraft are much easier than others. Examples of each: Easy = A-320 series (relatively short wheelbase, ultra effective and intuitive tiller; Hard = MD-80/90 series (very long wheelbase; high tiller forces). How do we stay on the lines? It's our craft; it's what we learn to do and practice a lot. It's all an experience issue.

N.B. I'm not arguing the semantics of the word "tiller" with BoeingGuy here at all; his descriptions are excellent.  
 
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Starlionblue
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RE: Steering Plane On The Ground

Wed Jun 26, 2013 4:02 am

Some planes only have tillers on the captain's side, like the MD-80. Other ones have a tiller on both sides.

Quoting dcaord (Thread starter):
i've always been amazed how planes are always so centered on the taxiway lines. I have to imagine its pretty difficult to see when steering a large aircraft. So how are they always so precise?

Practice practice practice. Taxiing a Cessna 172 or Pa-28 in a straight line takes a surprising amount of time to learn and beginner pilots have to learn to taxi before even their first take-off. Good instructors and examiners are anal retentive about centerline so you just learn or get yelled at. I also imagine that airliners are easier to taxi straight than GA planes since they have more inertia and longer wheelbases.

Quoting BoeingGuy (Reply 1):
The 707, 727, 737 and 787 have basically 1/4 of a steering wheel. It's like steering wheel but only 1/4 of it, so you hold the outside of it.

That's still a tiller actually. 

[Edited 2013-06-25 21:28:19]

[Edited 2013-06-25 21:29:44]
"There are no stupid questions, but there are a lot of inquisitive idiots." - John Ringo
 
rfields5421
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RE: Steering Plane On The Ground

Wed Jun 26, 2013 5:02 am

Quoting Starlionblue (Reply 3):
Taxiing a Cessna 172 or Pa-28 in a straight line takes a surprising amount of time to learn and beginner pilots have to learn to taxi before even their first take-off.

Tell me about it.

Quoting Starlionblue (Reply 3):
I also imagine that airliners are easier to taxi straight than GA planes since they have more inertia and longer wheelbases.

I've had several pilots tell me that over the years.

Quoting dcaord (Thread starter):
I have to imagine its pretty difficult to see when steering a large aircraft. So how are they always so precise?

I can't see the center line of the highway right beside my truck while heading down the road at 62 mph pulling my camping trailer, but the clues I learned 45 years ago about maintaining lane position still work to keep me centered.

Airplanes are just another ground vehicle when on taxi. We learn in our first ground movement phase how to use visual clues to maintain our positions.

In my experience, to taxi an airplane, we just have to adjust our visual focal point. It is actually easier than driving because we don't taxi at 65-75 mph.

I am somewhat amazed at how often people think an airplane take a whole additional level of precision control than an automobile. It really isn't that much more difficult to handle the controls than driving.

It is a whole additional level of learning, physics and theory than driving. Yes, and lots and lots of practice.

But the actual manual process isn't "harder" in my opinion - just different.
 
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Starlionblue
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RE: Steering Plane On The Ground

Wed Jun 26, 2013 5:20 am

Quoting rfields5421 (Reply 4):
I am somewhat amazed at how often people think an airplane take a whole additional level of precision control than an automobile. It really isn't that much more difficult to handle the controls than driving.

It is a whole additional level of learning, physics and theory than driving. Yes, and lots and lots of practice.

But the actual manual process isn't "harder" in my opinion - just different.

Indeed. The hand-eye (and hand-foot) coordination is no harder than driving a car. Certainly easier than driving a motorcycle. Steering with your feet is a bit weird for 30 seconds but after that it is no problem. As you say the fact that taxi is at 10-15 knots gives plenty of time to correct. Caveat: taxiing a taildragger takes a bit more skill, but even that is not too difficult.


Another thing that I always find is how non-pilots are so focused on the stick and rudder work, which actually is only one part of being a pilot. I can hold my own and stay well within practical test standards on things like steep turns and landings, but it is certainly not my strongest aspect as a pilot. On the other hand, I find flying an approach a pleasure, I'm good on comms, I understand radio navigation and I have quite good situational awareness. These skills are just as important. As you go towards bigger airplanes, hand flying is less of a focus as things like fuel management become much more important..

This focus on the pilot as primarily a stick and rudder guy inevitably leads to the common belief that the autopilot is somehow a cheat and that "all you guys do is sit there and push buttons." If they only knew the complexity of the button pushing aspect, even in a GA plane with a G1000, compared to the elegant simplicity of stick and rudder work!

But I digress.

[Edited 2013-06-25 22:21:27]
"There are no stupid questions, but there are a lot of inquisitive idiots." - John Ringo
 
wilco737
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RE: Steering Plane On The Ground

Wed Jun 26, 2013 5:30 am

Steering on the ground is something you have to be careful. I am flying 744 and 748 and the plane is long and you have to consider this when you actually turn.

You oversteer at times, so you are not all the time on the centerline with the nose gear. On the 748 we have a taxi camera where you can actually see how close you are to the center line. During tight turns you oversteer, means you overshoot the turn a bit and then make a tight turn. The main gear helps you out here as it can be steered as well (automatically).

You have visual cues to judge if you are on centerline or not. So when you sit in your seat properly you know which part of the cockpit should be aligned with the centerline and then you can be sure that the nose gear is on the centerline as well.

wilco737
  
 
BoeingGuy
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RE: Steering Plane On The Ground

Wed Jun 26, 2013 6:23 pm

Quoting Starlionblue (Reply 3):
Some planes only have tillers on the captain's side, like the MD-80. Other ones have a tiller on both sides.

First Officer's Tillers are baseline on the 747, 777 and 787, and optional on the 737, 757 and 767.

Quoting Starlionblue (Reply 3):
Quoting BoeingGuy (Reply 1):
The 707, 727, 737 and 787 have basically 1/4 of a steering wheel. It's like steering wheel but only 1/4 of it, so you hold the outside of it.

That's still a tiller actually.

Yes, by technical term, but the thingy on the 747, 757, 767 and 777 really looks like a Tiller so I was describing it as such. The other model ones do look like a 1/4 steering wheel so that's how I described it.

Quoting wilco737 (Reply 6):
Steering on the ground is something you have to be careful. I am flying 744 and 748 and the plane is long and you have to consider this when you actually turn.

The 777-300s actually have a Ground Maneuvering Camera system that the crew can pull up on the Multifunctional Display and monitor where their landing gears are on the taxiway. That gives the crew situational awareness if, say, they are about to cut a corner too short and put a main on the grass because of the length of the 777-300.
 
wilco737
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RE: Steering Plane On The Ground

Wed Jun 26, 2013 6:44 pm

Quoting BoeingGuy (Reply 7):
The 777-300s actually have a Ground Maneuvering Camera system that the crew can pull up on the Multifunctional Display and monitor where their landing gears are on the taxiway. That gives the crew situational awareness if, say, they are about to cut a corner too short and put a main on the grass because of the length of the 777-300.
Quoting wilco737 (Reply 6):
On the 748 we have a taxi camera where you can actually see how close you are to the center line.

We only have a camera for the nose gear, the left and right wingtip and a tail camera which looks down onto the whole airplane. So we have an idea where we are as well, but not with the maingear.

wilco737
  
 
fr8mech
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RE: Steering Plane On The Ground

Wed Jun 26, 2013 6:53 pm

Quoting Starlionblue (Reply 3):
Taxiing a Cessna 172 or Pa-28 in a straight line takes a surprising amount of time to learn and beginner pilots have to learn to taxi before even their first take-off.

I have an easier time keeping a 77 on the centerline than I had a C-152.

Good rule of thumb that worked for me was to line up with using my right thigh as a reference. B747 & B767 I would keep the centerline on the inside of my thigh. The other fleet types (B727, L1011, DC10, MD11, B757, DC8, A300) I've taxied would be lined up with my thigh or just outside.

Practice, practice, practice.
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jetstar
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RE: Steering Plane On The Ground

Wed Jun 26, 2013 8:19 pm

I have flown from the left seat both the Lockheed JetStar and the HS-125 corporate jets and also taxied a Gulfstream 2, Both the JetStar and the HS-125 had a small steering wheel on the left side of the pilots side panel and the G2 had a wheel on the top of the side panel. Corporate jets sit very low to the ground, are not that long and the cockpit is almost over the nose wheel so there was no need to extend out past the taxiway center line when lining up on the runway.

The G2’s came out from the factory with a tiller bar, a leftover design from the turboprop G1 days and it was very hard to steer the airplane with this tiller bar, so a third party vendor designed and had it certified via an STC a steering wheel to replace the tiller bar. A lot of the corporate operators purchased the kit and it became so popular that Gulfstream replaced the tiller bar with the steering wheel design in later production models.

In my ground maintenance days I taxied about every single engine airplane including tail draggers with heal brakes and small piston twin engine airplanes including Queen Airs and Cessna 310’s from the tie downs or out for engine run ups.

I remember one of the worst to taxi was a C-170 tail dragger with a crosswind gear, I couldn’t keep that airplane taxing in a straight line at all, it was all over the place. This is going back over 40 years ago but another difficult airplane was either a Piper Tri Pacer or a Piper Colt, it did not have any toe or heal brakes, just a Johnson bar that operated both brakes at once, I think toe brakes was an option later in production.

The fun ones to taxi were the ones that had one brake inop, usually due to the brake pads were worn down so far exposing the brake caliper piston enough that the O ring seal let go. Depending which airplane it was determined how bad it was to taxi. On most Pipers and Beechcrafts the nose wheel was linked directly to the rudder pedals so it was easy to over ride the tendency of the airplane to swing over to the good brake side when taxing by just using rudder pressure on the bad side.

Single engine Cessna’s were another story, the nose wheel is not connected directly to the rudder pedals, but through spring loaded steering tubes so when you applied opposite rudder when taxiing all you did was push the rudder pedal, it had very little effect on the nose wheel itself so I would taxi them very slowly to avoid going off of the taxiway.

Another feature of single engine Cessna’s was that the nose wheel would steer about 45 degrees each way by using the rudder pedals, but if you applied just one brake the nose wheel would caster over to about 80 degrees, you could literally pivot around a main wheel, but the only way to get the nose wheel back to center was to use the opposite brake to force the nose wheel back enough so you could steer with the rudder pedals again. It happened to me a few times where I got the nose wheel over to far while taxing a single Engine Cessna with one brake out and I would have to stop on the taxiway, shut the engine down, get out of the airplane and center the nose wheel by hand.

I own a Cessna 150 and it took some practice taxing with basically sloppy nose wheel steering, especially in tight places, but with that comes the ability to do very tight turns.

Then there was the American Aviation Yankee, the only nose wheel steering was by differential braking. One time I tried to taxi the airplane to the shop from its tie down with one brake out, I got about 50 feet and gave up, there was no way you could taxi this airplane on one brake, as soon as you applied the good brake it would make an immediate turn in that direction, so I had to go back to the shop and get a tug and tow the airplane in.

Memories of my maintenance good old days

JetStar
 
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7BOEING7
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RE: Steering Plane On The Ground

Wed Jun 26, 2013 9:25 pm

Quoting fr8mech (Reply 9):
Good rule of thumb that worked for me was to line up with using my right thigh as a reference. B747 & B767 I would keep the centerline on the inside of my thigh. The other fleet types (B727, L1011, DC10, MD11, B757, DC8, A300) I've taxied would be lined up with my thigh or just outside.

  


Always been taught whether you're driving from the left seat or right seat (dual tiller) on 727 thru 787 line it up with your inside leg. What's really amazing is, when you finally get to check it (777-300/300ER taxi cameras) it's really accurate.

Quoting BoeingGuy (Reply 7):
The 777-300s actually have a Ground Maneuvering Camera system that the crew can pull up on the Multifunctional Display and monitor where their landing gears are on the taxiway. That gives the crew situational awareness if, say, they are about to cut a corner too short and put a main on the grass because of the length of the 777-300.

  

At most airports the 777-300's can be taxied easily without using the camera and taxi procedures are taught without using the camera. On tight taxiways when turning the cameras do a real good job of helping you leave the taxi lights in one piece.

[Edited 2013-06-26 14:25:51]
 
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Starlionblue
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RE: Steering Plane On The Ground

Wed Jun 26, 2013 11:31 pm

Quoting BoeingGuy (Reply 7):
Quoting Starlionblue (Reply 3):
Quoting BoeingGuy (Reply 1):
The 707, 727, 737 and 787 have basically 1/4 of a steering wheel. It's like steering wheel but only 1/4 of it, so you hold the outside of it.

That's still a tiller actually.

Yes, by technical term, but the thingy on the 747, 757, 767 and 777 really looks like a Tiller so I was describing it as such. The other model ones do look like a 1/4 steering wheel so that's how I described it.

Ah I get it. Well, tillers can look quite different in different vehicles. 
"There are no stupid questions, but there are a lot of inquisitive idiots." - John Ringo
 
m1m2
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RE: Steering Plane On The Ground

Thu Jun 27, 2013 1:06 pm

I can't speak for large airplanes, but a good frame of reference for the Dash 8 is the Ground range lights. If you keep them on the center line, then you'll most likely be in the right place. As others have said, it comes with practise and different people have different ways of doing it to achieve the same result.

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