pegruder

Single Engine Taxi FSL A320

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So quick question.  Has anyone tried single engine taxi in the FSL bus?  There seems to be a ridiculous amount of yaw when trying to do so that I can't keep it straight without a fairly significant amount of tiller input.  (Maybe 30-50% of my total range)  Is that what goes on in the real thing?  I feel like if I had an engine failure on takeoff the whole thing might swap ends.

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I tried it, does not work very well. I find it hard to believe that the real thing would be that hard to taxi. The taxi physics in P3D have always sucked. 

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A buddy of mine that is an A320 pilot says it will yaw on single engine and that the FSL simulates it pretty well.  He said you will need to use rudder pedals when in single taxi. 

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6 minutes ago, Zimmerbz said:

A buddy of mine that is an A320 pilot says it will yaw on single engine and that the FSL simulates it pretty well.  He said you will need to use rudder pedals when in single taxi. 

Wow interesting to hear.  I figured it was P3D's awful ground physics.

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Yeah... I would guess it is slightly exaggerated in the sim but he said you will need to have rudder input.  Also remember to shut down engine 1 not 2 and to turn on yellow electric pumps.  

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I single engine taxi a lot with it. Start #1 first, yellow elec pump on, APU bleed off. Then when starting #2, APU bleed on, yellow elec pump off, then start #2 per my buddy who flies IRL.

I'm sure FSL simulated single-engine taxi as well as they could have given the constraints of P3D...you could forget about ever single engine taxiing in the NGX...nevertheless, I'm fairly certain there is still too much yaw in the FSL bus when the operable engine is providing breakaway thrust. Try turning out to the left from a complete stop with the #1 engine only...very difficult. I wonder if that's something that could be improved upon with some of the new FDE modeling they are doing or not.

Ben 

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3 hours ago, pegruder said:

 

So quick question.  Has anyone tried single engine taxi in the FSL bus?  There seems to be a ridiculous amount of yaw when trying to do so that I can't keep it straight without a fairly significant amount of tiller input.  (Maybe 30-50% of my total range)  Is that what goes on in the real thing? 

30-50% is way too much.  You have to use the pedals to keep the real one straight during taxiing. Note that at taxi speeds the pedals provide only 6° steering angle while the tiller provides 75°.

There should be only very little steering tiller input necessary...if it's correctly simulated.  

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If you're unhappy with how it simulates single engine taxy (actually, within what is possible in FSX/P3D, I think FSL have not done a bad job of it), it's worth being aware that not all airlines single engine taxi the thing anyway, and even those that recommend it as an SOP don't always do it, especially for example, if there is an APU shutdown or the taxyway conditions are a bit iffy - for example icy -  where asymmetric thrust would certainly not help matters, so the decision on whether to do so remains at the crew's discretion, and so it is your decision too with your FSL A320. But, having said that, if you do want to do a single engine taxy and want it realistic, note that it is almost always the port engine you will be doing it with on an A320. It's different on an A330, because the hydraulic system is not the same, which is also why you crank the engines in the opposite order to an A320 when it's an A330, which is worth knowing if you have the BBS 330 or are waiting for the Aerosoft one.

You'll see many A320s taxying with both engines regardless of SOPs and probably even moreso this time of year when there's ice, snow and deicing fluid all over the place since with two engines at idle it'll help it go straighter and they can be at lower settings too since there's two of them running, so there's less chance of ingesting some FOD. That's when it can get fun (i.e. potentially risky) on the stands if one comes on stand with both engines cranking because of an APU shutdown for example, since in that case you have to put the chocks and GPU/FEP on when the anti-collision beacons are still flashing and the engine(s) are still turning, and in doing that, you are getting fairly close to the live starboard engine intake, which is even more fun when the stand is slippery. 

Most of the time you'll only see a single engine taxy on the way into the stands. It saves fuel amongst other things and when the thing is light from being at landing weight (unless it is tankering fuel) it will roll with pretty much no additional thrust applied. But for outbound aeroplanes, as much as the idea of a single engine taxy to the runway would be good in terms of saving a bit of fuel, when we push out, we start both engines; they are cleared to crank once the tug is over the road at the back of the stand although (theoretically at least) some airports will recommend you wait until you are at the TRP, but that's not always practical if it's a non standard long push, since you want to know both engines will start okay ASAP, because finding out one of them won't crank when the thing is on a taxyway 500 yards away from the stand it just left would be a pain in the @ss, as the aeroplane might have to get towed back onto the stand via a circuitous route. Not only that, the crew cannot see the engines, so it's the start master's responsibility to watch for a hot start of any other issues as these won't always show on the cockpit displays, and he/she can't do that when you're on your way to the holding point.

As J35OE says, you don't need a lot of correction to keep the thing straight on the real thing with only one rubber band going, but you do need some, obviously, since it is thrusting from one side only when one engine is shut down and even at idle there is quite a lot of thrust coming out of the back of the thing, i.e. at take off power, as you'd expect, the clearway distance at the rear of the thing is 365 metres, at typical taxy thrust it's 200 metres, but even at idle thrust it is still 100 metres, which gives you an idea of how much thrust it is kicking out even when the throttles are essentially closed. I was actually looking at this a couple of nights ago at EGCC when the ramp was very wet on stand 71 and you could see water being kicked back well past the other side of the road and onto the taxiway even when the thing had been chocked and had a GPU connected with the throttles at pretty much idle (this was an APU shutdown arrival, which is why both engines were still running after it had been chocked).

Strictly speaking, the APU exhaust outlet of the A320, and many other airliners, does add a very tiny bit of thrust too, which whilst not really able to get it moving, or even sustain it moving once it has overcome the initial inertia of being stationary, does still have an (admittedly very small) effect on how straight it will go once the thing is moving, but whether FSL bothered to factor this extremely small effect on thrust is another matter. I'm guessing probably not.

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5 hours ago, Zimmerbz said:

A buddy of mine that is an A320 pilot says it will yaw on single engine and that the FSL simulates it pretty well.  He said you will need to use rudder pedals when in single taxi. 

With all due respect to you and your friend, but I have been flying the A32F family for more than 10 years and the FSL does NOT simulate single engine pretty well. I don´t know if it's the P3D engine's fault or FSL problem, but now it's NOT correct.

And you never have to use the pedals to keep the real one straight during taxiing.

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26 minutes ago, hmuller said:

With all due respect to you and your friend, but I have been flying the A32F family for more than 10 years and the FSL does NOT simulate single engine pretty well. I don´t know if it's the P3D engine's fault or FSL problem, but now it's NOT correct.

And you never have to use the pedals to keep the real one straight during taxiing.

Exactly 

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5 hours ago, Chock said:

If you're unhappy with how it simulates single engine taxy (actually, within what is possible in FSX/P3D, I think FSL have not done a bad job of it), it's worth being aware that not all airlines single engine taxi the thing anyway, and even those that recommend it as an SOP don't always do it, especially for example, if there is an APU shutdown or the taxyway conditions are a bit iffy - for example icy -  where asymmetric thrust would certainly not help matters, so the decision on whether to do so remains at the crew's discretion, and so it is your decision too with your FSL A320. But, having said that, if you do want to do a single engine taxy and want it realistic, note that it is almost always the port engine you will be doing it with on an A320. It's different on an A330, because the hydraulic system is not the same, which is also why you crank the engines in the opposite order to an A320 when it's an A330, which is worth knowing if you have the BBS 330 or are waiting for the Aerosoft one.

You'll see many A320s taxying with both engines regardless of SOPs and probably even moreso this time of year when there's ice, snow and deicing fluid all over the place since with two engines at idle it'll help it go straighter and they can be at lower settings too since there's two of them running, so there's less chance of ingesting some FOD. That's when it can get fun (i.e. potentially risky) on the stands if one comes on stand with both engines cranking because of an APU shutdown for example, since in that case you have to put the chocks and GPU/FEP on when the anti-collision beacons are still flashing and the engine(s) are still turning, and in doing that, you are getting fairly close to the live starboard engine intake, which is even more fun when the stand is slippery. 

Most of the time you'll only see a single engine taxy on the way into the stands. It saves fuel amongst other things and when the thing is light from being at landing weight (unless it is tankering fuel) it will roll with pretty much no additional thrust applied. But for outbound aeroplanes, as much as the idea of a single engine taxy to the runway would be good in terms of saving a bit of fuel, when we push out, we start both engines; they are cleared to crank once the tug is over the road at the back of the stand although (theoretically at least) some airports will recommend you wait until you are at the TRP, but that's not always practical if it's a non standard long push, since you want to know both engines will start okay ASAP, because finding out one of them won't crank when the thing is on a taxyway 500 yards away from the stand it just left would be a pain in the @ss, as the aeroplane might have to get towed back onto the stand via a circuitous route. Not only that, the crew cannot see the engines, so it's the start master's responsibility to watch for a hot start of any other issues as these won't always show on the cockpit displays, and he/she can't do that when you're on your way to the holding point.

As J35OE says, you don't need a lot of correction to keep the thing straight on the real thing with only one rubber band going, but you do need some, obviously, since it is thrusting from one side only when one engine is shut down and even at idle there is quite a lot of thrust coming out of the back of the thing, i.e. at take off power, as you'd expect, the clearway distance at the rear of the thing is 365 metres, at typical taxy thrust it's 200 metres, but even at idle thrust it is still 100 metres, which gives you an idea of how much thrust it is kicking out even when the throttles are essentially closed. I was actually looking at this a couple of nights ago at EGCC when the ramp was very wet on stand 71 and you could see water being kicked back well past the other side of the road and onto the taxiway even when the thing had been chocked and had a GPU connected with the throttles at pretty much idle (this was an APU shutdown arrival, which is why both engines were still running after it had been chocked).

Strictly speaking, the APU exhaust outlet of the A320, and many other airliners, does add a very tiny bit of thrust too, which whilst not really able to get it moving, or even sustain it moving once it has overcome the initial inertia of being stationary, does still have an (admittedly very small) effect on how straight it will go once the thing is moving, but whether FSL bothered to factor this extremely small effect on thrust is another matter. I'm guessing probably not.

This wasnt so much as an "Unhappy with" but more of a "curious on what the real bus is like" sorta question.  Although it seems divided on feedback from real world pilots?

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My guess is that I misunderstood my friend or I didn’t ask him correctly. I’ll see if I can clarify. 

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11 hours ago, pegruder said:

I feel like if I had an engine failure on takeoff the whole thing might swap ends.

At low speed, that is absolutely a very real risk - a sudden engine failure early in the takeoff roll in any (multi-engine) aircraft type is always one of the most tricky things to handle as with takeoff thrust set on the other engine and little if any rudder authority things can go very pear shaped very quickly unless you immediately close the thrust levers. Even then regaining directional control may be very difficult if 70 odd tonnes of aeroplane is now heading toward the edge of the runway.

At higher speeds of course you will have the rudder authority to keep straight (Vmcg, the minimum control speed on the ground, is one of the lower limiting factors for V1 as clearly you cannot continue the takeoff if you cannot keep the thing on the runway!).

Regarding the yaw - there are a number of real Airbus pilots on the beta team and I know this is something they have been consulted on. I can ask again, however!

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I am not a developer but ground handling and ground effects not being simulated correct is a bug as old as the flight sim engine

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1 minute ago, Boeing or not going said:

I am not a developer but ground handling and ground effects not being simulated correct is a bug as old as the flight sim engine

Which is kind of why I made this post also.  Im not sure if FSL did something outside the sim to compensate.  I know theres a number of tricks devs have been using lately.

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Just now, pegruder said:

Which is kind of why I made this post also.  Im not sure if FSL did something outside the sim to compensate.  I know theres a number of tricks devs have been using lately.

Do not own the FSL and the tricks you can use is more like hacking it to get normal operations right. Going off memory the issue is you have to add thrust but only when on the ground to taxi and that makes fuel burn and in the air performance not realistic. PMDG 747's have better ground handling than their other releases so devs are getting there. Do you use a Tiller instead of rudder pedals?

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1 hour ago, pegruder said:

This wasnt so much as an "Unhappy with" but more of a "curious on what the real bus is like" sorta question.  Although it seems divided on feedback from real world pilots?

Well, the division is easy to explain; they're probably all correct... in the context of their own experience.

When we fly our FSL Airbus A320, we can do whatever we like, load as much fuel as we like, load as many passengers as we like, have as much or as little baggage and cargo as we like, use whatever cockpit options we like, fit whatever engines we like, use the expedite button whenever we like (some pilots are not allowed to do this), use whatever cost index we like, fly in whatever weather we like, from wherever we like, to wherever we like etc, etc. This changes the experience, so what we experience is not necessarily 'wrong' and the same is true when two A320 pilots disagree about how an A320 behaves. Unless they are sat side by side in the exact same A320, working for the same airline, following the same SOPs, flying the same routes with the same fuel loads, baggage and cargo loads and number of passengers and so on, there are going to be differences between the aeroplanes they personally are flying and how they behave, even though they are 'both flying A320s'.

To elaborate on this... Although I do work on the A318, A319 and A320 and very occasionally the A340, the main Airbuses I tend to work on are A321s and A330s, and of these, it's mostly A321s, and of those, it's almost always ones with CFM56-5B series engines, which is the variant that was designed specifically for the A321, but which later found its way into other Airbuses too.

The CFM56-5B series engine can range in power from 21,300lbs of thrust, right up to 33,000lbs of thrust, depending on which model of CFM56-5B we're talking about. The most powerful CFM engine you'll find in an A320 (unless we're talking about a NEO variant) will likely be the CFM56-5B4 version, rated at 27,000lbs of thrust, but even this isn't the only factor to consider, because that engine has a bypass ratio of 5.7, and when we consider that you could also find that an A320 might be fitted with CFM56-5B6 engines, which not only have a lower thrust rating of 23.500lbs, but also a higher bypass ratio of 5.9, you can see that even two pilots at the same airline, both flying A321s could differ in their opinion about how an aeroplane handles. For example, at Thomas Cook Airlines which I work for when servicing aeroplanes, they fly A321-200 G-TCDC, which is about five years old, but they also leased ex-Aeroflot A321-200 LY-VED for the summer, which is about ten years old. These aeroplanes are not specced up the same, they differ in many ways (I could be blindfolded and touch certain parts of these two aeroplanes, and I would be able to tell you which one was which), yet they are both A321-200s with CFM56-5 engines.

This means those two pilots who both fly the A320 and say 'it does this or that', could well be flying aeroplanes which 'are the same model' and have what appears to be the 'same engines', but there could be as much as 7,000lbs of available thrust difference between the two aeroplanes, and this isn't even taking into account all the other configurations which might be different as well, for example, the size of the fuselage fuel tank (it's not the same on all Airbuses of the same model designation), the configuration of the hold (some of them use containers, some of them load loose baggage), so some of them are heavier than others because the floor is different in some of them to what it is in others.

This doesn't even get into the fact that an Airbus A320 can have a completely different engine from the CFM56 too, because it can have the IAE V2500 which again can have vastly different thrust ratings depending on which model we're talking about, and have different bypass ratios, and it even has a different engine cowling because its fan blades have a diameter which is five inches less than that of the CFM56. If we start talking about the entire 320 family as well, you can throw in another engine type too, because the A318 can have a third option - the Pratt & Whitney PW6000 - and even that can have a range of different thrust options from 18,000lbs to 24,000lbs,

So when people talk about how much an Airbus will yaw or whatever when taxying on one engine, or whether it will do so on idle or not, and so on, the answer is dependent on which exact individual aeroplane you're talking about, and what it is loaded up with in terms of fuel and payload. That's why you're going to get different answers from different pilots at different airlines.

It's very often the same with two pilots who've flown any sort of aeroplane which is the same model but not the same aeroplane, i.e. I really love flying the SZD 50-3 in real life. I think it's a great aerobatic aeroplane and I like nothing better than to throw a few spins in the things, yet when I say that to some pilots, they look at me like I've lost the plot, because as a type, it got an - undeserved in my opinion - reputation for being a death trap which was hard to get out of a spin. This following a number of spin-related accidents. But I've spun them more times than I've had hot dinners and never had any problems recovering from one, it's like any aeroplane, if you know what you're doing with it, it will do what you tell it to, but if you don't, it will bite you, but either way, you do get to know an aeroplane which you fly a lot, and your own experience informs your opinion of it.

Edited by Chock
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5 minutes ago, Boeing or not going said:

Do not own the FSL and the tricks you can use is more like hacking it to get normal operations right. Going off memory the issue is you have to add thrust but only when on the ground to taxi and that makes fuel burn and in the air performance not realistic. 

It's not about the general friction problem, it's about the definitely exaggerated asymmetric thrust effect. Increasing idle thrust on ground without affecting thrust/fuel flow/performance in flight is easy and doesn't require any trick or hack. 

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7 minutes ago, Chock said:

So when people talk about how much an Airbus will yaw or whatever when taxying on one engine, or whether it will do so on idle or not, and so on, the answer is dependent on which exact individual aeroplane you're talking about, and what it is loaded up with in terms of fuel and payload. That's why you're going to get different answers from different pilots.

That's definitely not the case. We are talking about idle thrust values of ~3000lbs which isn't exactly a lot.

If you are taxiing an A320 with one engine at idle, there is no significant difference in handling, regardless of the different A320 versions/loading.

It's been almost 4 years since I've last flown an A320 and AFAIR it has a slight tendency to turn into the dead engine which you needed to correct every now and then.

It's about no turning tendency at all, or a slight tendency, but in any case it's far from what the 'holy' FSL A320 seems to do. 

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18 minutes ago, J35OE said:

We are talking about idle thrust values of ~3000lbs which isn't exactly a lot.

Nope, we're talking about the leverage which a difference of 3,000 lbs of thrust will make when it is located five and three quarter metres out from the centreline of the aircraft and exiting the tailpipe of the engine and the rear of the fan casing almost exactly on the longitudinal pivot point of the aircraft, since it is approximately 11 metres behind the nosewheel and right in line with the main gear but is almost two and a quarter metres outboard of that gear and considerably further out from the centre pivot point. This is something which imbues a very much larger potential for leverage than the 3,000lbs thrust difference would make if that thrust was merely acting down the centre line of the aircraft, which it of course isn't.

Edited by Chock

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Nice amount of numbers. Here's a simple question: Have you ever taxied an A320 with one (or even with both) engine(s) running?

Btw, you were initially not talking about the 3000lbs total difference, but about the difference between the various A320 versions.

Edited by J35OE

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1 hour ago, J35OE said:

Nice amount of numbers. Here's a simple question: Have you ever taxied an A320 with one (or even with both) engine(s) running?

I see what you did there, nice sidestep of those numbers to switch to an appeal to authority argument lol.

But to your question, the answer is nope, not really since I am not an airline pilot, but also yes, sort of, and by that I mean; in relation to the point, if you're referring to actually driving the thing, no, if you mean being in the cockpit of one when that is being done, yes very often, if you mean driving one in the full motion A320 simulator at Toulouse for when I was doing some work for Airbus years ago, yes, since it was me who produced the SOPs for the A320 and whilst I was working on that project, they invited me to fly in their simulator a few times to assist in understanding what things I was putting in the manuals I was producing so we could get the wording correct in the SOP and as clear as it could be. Now I know that's not a real A320, but it was the real actual EADS full motion simulator of the A320 at their own facility, so it was about as real a simulator for an A320 as you can get and not only that, all that work meant I'm very familiar with the real aeroplane.

But back to the point I was making which you sidestepped, if you mean am I familiar with the weight of the things and how they steer, yes I am, I tow them about and push them out as well as supervising the engine starts, in fact, here's a really rubbish phone pic I took out of the back of the tug over my shoulder last Monday night at EGCC when I was towing one in the rain (actually it is an A321 to be fair not an A320, but that's even trickier because they are longer) from Stand 32 to Stand 66, when you really need to be aware of how the things steer. Sorry it's a bit blurred but I was really concentrating on keeping the thing on the centreline and listening out for an x-ray alert and what not, because Thomas Cook tend to get annoyed if you crash their 70 million Dollar aeroplanes into other aeroplanes and hangars and stuff lol. I suspect  'I was trying to get a cool picture' wouldn't quite work as an acceptable excuse:

KGpzypI.jpg

Now here's a question for you, well actually more of a fun thing to try which will serve to explain how much a bit of leverage with even a very small force will do to move an airliner around...

Next time you're on the ramp near an A320 and it is about to be  loaded up, before it gets too full, ask if you can go up into its rear hold. If it is shut up, you can open it by first lifting the cargo door lever up, then flipping a panel on the underside of the fuselage located about two feet back from the hold door and pushing the lever in there to starboard, but remember to keep one hand on the door when you initially flip the main lever up because it will drop under gravity and smash you in the head if you don't lol, and that bloody hurts, I know, I've done it a few times. You'll need FEP or a GPU on to do that incidentally otherwise you'll have to use the manual hydraulic pump which is on the right hand side of the belly fairing under a big cover panel. When the hold is open, you'll need to either pull yourself up into the hold or get some engineer's steps to get up there because the sill is about six feet or so off the ground. If you can't do that, then try it in a 737-800, since they are a lot lower to the ground and more or less the same size as an A320.

When you're up there in the hold, stand up - well, unless you're a midget you'll need crouch actually, since it's not that roomy in there lol - then face the front of the hold and grab the cargo net with both hands; now rock your weight from side to side. You will feel the aeroplane move from side to side. A lot, in fact it will surprise you by how much it rocks about. You weigh let's say the average for a bloke, so that'd be around 200lbs, yet all you had to do, thanks to a bit of leverage imbued by being a few meters back from the aeroplane's fulcrum point, was to shift 200lbs about a bit and that big @ss end of the aeroplane started swinging didn't it? So guess what an additional 3,000lbs of thrust is going to do when it has some leverage assisting it.

Edited by Chock
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What might help you with taxying the FSL 'Bus, is to use a X-Box style controller for the nosewheel steering. Although this isn't the same as a tiller obviously, it's a cheap way to approximate a roughly similar control for the tiller, or, if you want something which is even more like the real thing, with a bit of searching, you will find that there are one or two PC gamepads which have been made that actually have a small steering wheel on them, which would be a very close approximation of a tiller in a cockpit. You could even rip the innards from one and make a more authentic tiller handle for one if you were feeling creative. Another alternative is to get a full sized racing wheel for a PC and then cut the wheel down to the shape of a tiller.

In any case, here's a video of me steering the FSL A320 with a USB gamepad controller with only one engine running and you can see it does the job okay. I'm not even holding down the comma key to activate full steering, the small amount of movement you get without doing that is enough to keep it going along the taxiway. Don't be too obsessed with keeping the nose wheel on the centreline either, we don't worry about that too much in the real world, so long as you're pretty much on or very near to it, it's good enough, and in reality, the tiller is quite sensitive anyway, so it'd be a very good pilot who'd keep it on the line all of the time because it's more important to keep the main wheels on the taxiway where the surface is designed for that load bearing support. Having said that, in snowy conditions or poor visibility, the bumps you feel when you go over the taxiway centreline lights are kind of useful to know you're on the right track lol:

 

Edited by Chock

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Edited by J35OE

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