Single Engine Taxi FSL A320

[pegruder 65]

 

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.

[fakeflyer737 990]

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. 

[Zimmerbz 153]

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. 

[pegruder 65]

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.

[Zimmerbz 153]

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.  

[bbain1187 118]

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 

[FDEdev 955]

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.  

[Chock 17,769]

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.

[Hamilton_ 45]

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.

[fakeflyer737 990]

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 

[pegruder 65]

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?

[Zimmerbz 153]

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

[skelsey 765]

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!

[Boeing or not going 578]

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

[pegruder 65]

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.