Lining up with the centreline
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Lining up with the centreline
I appreciate that this scenario most likely never happens in professional aviation. But on my last take-off, I did wonder...
if you were to fudge the turn and end up not correctly aligned, for whatever reason, what do you do? Can you correct the alignment on the take-off roll in the way that adjustments are made anyway? Or would you ever have to taxi the aircraft to the first exit, come back and try again (presumably losing some face!)? Or does that simply never happen?
Apologies for the naivety, but I'm going to draw that shameful comparison and say that it must be easier to do than in a certain piece of Microsoft software?
if you were to fudge the turn and end up not correctly aligned, for whatever reason, what do you do? Can you correct the alignment on the take-off roll in the way that adjustments are made anyway? Or would you ever have to taxi the aircraft to the first exit, come back and try again (presumably losing some face!)? Or does that simply never happen?
Apologies for the naivety, but I'm going to draw that shameful comparison and say that it must be easier to do than in a certain piece of Microsoft software?
Last edited by Nicholas49; 23rd Nov 2010 at 09:15.
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Just SLF but would be interested in the answer too, though to be honest I hope it is something like ... 'it never happens unless there's some sort of real failure' on account of the fact that if you can't line up on the centre line I wouldn't be too happy about you even trying to get it from parking or the gate to the runway! 
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Nicholas,
Being aligned with the centerline is only important if one has a very narrow runway. Some operators, and indeed some avaition authorities, encourage aligning off-center in order to make the airplane more visible (particularly at night). An airplane on the centerline can blend in with the centerline lights, and may be more difficult to see for an aircraft approaching to land.
Some pilots prefer to offset a few feet either side of the centerline in order to keep from listening to the bumping sound of ruway centerline lights under the nosewheels.
Aligning with the centerline isn't a problem. One can simply drift back onto it during the takeoff roll, if desired.
Being aligned with the centerline is only important if one has a very narrow runway. Some operators, and indeed some avaition authorities, encourage aligning off-center in order to make the airplane more visible (particularly at night). An airplane on the centerline can blend in with the centerline lights, and may be more difficult to see for an aircraft approaching to land.
Some pilots prefer to offset a few feet either side of the centerline in order to keep from listening to the bumping sound of ruway centerline lights under the nosewheels.
Aligning with the centerline isn't a problem. One can simply drift back onto it during the takeoff roll, if desired.
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Thanks for the replies. I understand your points.
I suspect this is a classic example of the many, many difference between performing a take-off using a certain simulator software and the real heavy metal. In the former, it is extremely difficult to remain aligned, not least because of the restricted view and lack of a rudder!
I suspect this is a classic example of the many, many difference between performing a take-off using a certain simulator software and the real heavy metal. In the former, it is extremely difficult to remain aligned, not least because of the restricted view and lack of a rudder!
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Nicholas,
I don't play the simulation games, but I recall that some of the simulations could be steered on the ground using a joystick that rotated side to side for yaw. Not really realistic, but it may be one option.
Rudders are useful in the takeoff after about 60 to 80 knots or so. Rudder pedal steering is minimal, but the use of a steering tiller in the airplane makes corrections easy early in the takeoff roll, and during taxiing.
If you're simulating a big airplane, remember that when entering the runway, one must taxi past the centerline before turning. How far depends on the nosewheel placement relative to the cockpit, as well as the main gear. One generally goes past the turning point by some distance, in the cockpit, before swinging the nose back around to line up on the new centerline for a taxiway or runway. Trying to keep the nosewheel on the centerline all the time, especially in turns, can mean the mains go off the taxiway or crush the taxiway lights. If you start your turn to the runway centerline as soon as it's directly off to your right or left when you enter the runway, you'll nearly always be misaligned, because you haven't gone far enough onto the runway before making the turn.
A good way to visualize it is to use a model airplane...or do what one check airman whom I know, recommends. He suggests that people go play with a model semi-truck before taxiing the airplane (a 747, in our case). Get an idea of visualizing the turns before actually making them. It's easier when it comes time to actually go taxi the beast.
The other things is watching speed in the taxi. We limit our taxi speed to 20 knots straight, and a maximum of 10 knots in a turn (usually considerably less). This prevents a heat build-up during taxi from tire flex (some places have nearly three miles of taxiing, which can really heat up tires on a heavy airplane, just from the taxiing), and it prevents unwanted excursions during taxi from becoming big excursions. We taxi slowly, and we must, because we're large and heavy. We often see smaller airplanes blowing by at fast speeds. They can get away with it, but it's a poor practice.
I don't play the simulation games, but I recall that some of the simulations could be steered on the ground using a joystick that rotated side to side for yaw. Not really realistic, but it may be one option.
Rudders are useful in the takeoff after about 60 to 80 knots or so. Rudder pedal steering is minimal, but the use of a steering tiller in the airplane makes corrections easy early in the takeoff roll, and during taxiing.
If you're simulating a big airplane, remember that when entering the runway, one must taxi past the centerline before turning. How far depends on the nosewheel placement relative to the cockpit, as well as the main gear. One generally goes past the turning point by some distance, in the cockpit, before swinging the nose back around to line up on the new centerline for a taxiway or runway. Trying to keep the nosewheel on the centerline all the time, especially in turns, can mean the mains go off the taxiway or crush the taxiway lights. If you start your turn to the runway centerline as soon as it's directly off to your right or left when you enter the runway, you'll nearly always be misaligned, because you haven't gone far enough onto the runway before making the turn.
A good way to visualize it is to use a model airplane...or do what one check airman whom I know, recommends. He suggests that people go play with a model semi-truck before taxiing the airplane (a 747, in our case). Get an idea of visualizing the turns before actually making them. It's easier when it comes time to actually go taxi the beast.
The other things is watching speed in the taxi. We limit our taxi speed to 20 knots straight, and a maximum of 10 knots in a turn (usually considerably less). This prevents a heat build-up during taxi from tire flex (some places have nearly three miles of taxiing, which can really heat up tires on a heavy airplane, just from the taxiing), and it prevents unwanted excursions during taxi from becoming big excursions. We taxi slowly, and we must, because we're large and heavy. We often see smaller airplanes blowing by at fast speeds. They can get away with it, but it's a poor practice.
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Nicholas
Sorry if I sounded flippant earlier ....
As SNS3Guppy has said, a joystick or other device to help with steering is the best way to steer in 'that' simulation, but couple that with the Virtual Cockpit view where you can turn and look right or left out of the windows to give you your visual reference points. That is as near to the real world situation as you can get and you'll get it right with practice 19 times out of 20. Definitely not 2D view. I hate Virtual Cockpit views usually but it is as close to 'real' as you can get and the only way to get turning manouevres on the ground or in the air (e.g. Funchal!) right.
Sorry if I sounded flippant earlier ....
As SNS3Guppy has said, a joystick or other device to help with steering is the best way to steer in 'that' simulation, but couple that with the Virtual Cockpit view where you can turn and look right or left out of the windows to give you your visual reference points. That is as near to the real world situation as you can get and you'll get it right with practice 19 times out of 20. Definitely not 2D view. I hate Virtual Cockpit views usually but it is as close to 'real' as you can get and the only way to get turning manouevres on the ground or in the air (e.g. Funchal!) right.
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Some pilots prefer to offset a few feet either side of the centerline in order to keep from listening to the bumping sound of ruway centerline lights under the nosewheels.
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Nicholas
Taking off neatly with a crosswind in "that simulator" is well nigh impossible.Some tipsters suggest turning the wind off by using FSUIPC.Even twitchy little light aircraft are easier in real life as long as you are within limits
Taking off neatly with a crosswind in "that simulator" is well nigh impossible.Some tipsters suggest turning the wind off by using FSUIPC.Even twitchy little light aircraft are easier in real life as long as you are within limits
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SNS3Guppy, thanks for the detailed reply.
Following your comments, I can see that the 'turn technique' (for want of a better phrase) used by an Airbus A320 pilot to line up will be different from the technique used by a Boeing 747 given the difference in size, shape, position of landing gear on their respective aircraft.
But I wondered how you know when to make the turn? Do you have a visual reference point on the runway? For example, you start the turn when you reach the second stripe after the centreline? Slightly crass analogy, but when you learn to drive and to do a reverse parallel park, you learn to turn when the car passes a certain point. Is it similar?
Is it any more difficult in reduced visibility, for example at night or in fog? From a previous thread, I remember that some types (e.g. B777) have external cameras with monitors on the flight deck, which must help.
Following your comments, I can see that the 'turn technique' (for want of a better phrase) used by an Airbus A320 pilot to line up will be different from the technique used by a Boeing 747 given the difference in size, shape, position of landing gear on their respective aircraft.
But I wondered how you know when to make the turn? Do you have a visual reference point on the runway? For example, you start the turn when you reach the second stripe after the centreline? Slightly crass analogy, but when you learn to drive and to do a reverse parallel park, you learn to turn when the car passes a certain point. Is it similar?
Is it any more difficult in reduced visibility, for example at night or in fog? From a previous thread, I remember that some types (e.g. B777) have external cameras with monitors on the flight deck, which must help.
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having spent the last 4 years flying a large turbo prop from a performance limited runway (1100m) with a turning circle at both ends I can tell you i would much rather start every take off with the mains up against the grass than loose another 20 m of runway by getting the nose wheel hitting some lights!
as mentioned above, the ac can easily be controlled on the take of run getting it back onto the centre line.
as mentioned above, the ac can easily be controlled on the take of run getting it back onto the centre line.
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But I wondered how you know when to make the turn? Do you have a visual reference point on the runway? For example, you start the turn when you reach the second stripe after the centreline? Slightly crass analogy, but when you learn to drive and to do a reverse parallel park, you learn to turn when the car passes a certain point. Is it similar?
At a previous airfield that I was based at I knew that if I got to the displaced threshold line and turned 25 degrees to the right until it my arse was over one of the lines of (can't remember what it's called but it's the black rubbery stuff that they fill cracks up with) and then went to full 'opposite lock' I would be lined up perfectly on the centreline at the end of the turn, only worked at one end though the other end I would wait until the runway side lights intersected with the F/O's map clip. Strangely I turn opposite directions at opposite ends of the runway too. How did I discover that it worked that way? Trial and error!
On other runways with a 90 degree line up I wait until the centreline intersects the third air vent on the rear pillar of my side window - behind my left shoulder - then use a full lock turn which puts me pretty much bang on the centreline line. However, if I'm turning right to line up it's more guess work 'cos there'a fatty F/O in the way! If it's dark or low vis I stick to the yellow lines.
Not crass at all mate.
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<<But I wondered how you know when to make the turn? >>
When you are driving a car, how do you know when to turn the steering wheel at a road junction?? It's exactly the same except an aeroplane is bigger. It's just training end experience.
When you are driving a car, how do you know when to turn the steering wheel at a road junction?? It's exactly the same except an aeroplane is bigger. It's just training end experience.
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But I wondered how you know when to make the turn? Do you have a visual reference point on the runway? For example, you start the turn when you reach the second stripe after the centreline? Slightly crass analogy, but when you learn to drive and to do a reverse parallel park, you learn to turn when the car passes a certain point. Is it similar?
If one is entering the runway at a right angle to the runway direction, how far one goes relative to the far side of the runway really depends on how wide the runway is. Instead, if one goes a known distance past the centerline, swinging right or left to line up is a simple affair.
The process is more like driving a truck than taxiing a light airplane, particularly if one is sitting in the cockpit ahead of the nosewheel, instead of behind it. One goes past the turn point, then swings around to line up.
When I did my first day flight as a brand-new 747 First Officer, the training captain went outside, and set his flight case directly in line with the left main gear. He had me sit normally in my seat, and get an idea of just where the wheel would track in relation to my field of view. As it turned out, it's close enough that if one can see the edge of the runway out the window, then one isn't going to run off the runway. By doing this, the instructor was giving me a frame of reference for knowing where the gear was trailing along behind me.
When I first flew the PZL Dromader, I found that to swing onto a parking spot, putting the intended turning point just past the crook in the wing's leading edge would be ideal. In a J-3 cub, I could simply look out the window and put the tire on the spot and do the same thing. Swinging the tail became a matter of feel then, for how far the wings and tail would swing when parking.
Some of it can be done using a reference mark, and some of it is simply feel. How far one goes beyond the centerline of a runway or taxiway is also affected by the angle one enters the runway or taxiway. The larger the angle, the farther one must go past the centerline before tur ning...and of course it very much varies with the aircraft. For example, in the 747, the body gear trucks turn opposite the nosewheel, so that the turn radius is reduced, and the way in which the airplane turns differs from say, a C-130 or B737. Obviously taxiing a Cessna 172 is different from a Pitts Special or an Airbus A320. In some airplanes, one can follow the centerline stripe, whereas in others one can't, when turning a corner. One needs to understand what the airplane will do when taxiing, and this comes fundamentally from experience in the airplane and the training behind it.
