Single Engine Taxi FSL A320

[Boeing or not going 578]

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?

[Chock 17,769]

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 October 28, 2018 by Chock

[FDEdev 955]

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. 

[FDEdev 955]

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. 

[Chock 17,769]

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 October 28, 2018 by Chock

[FDEdev 955]

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 October 28, 2018 by J35OE

[Chock 17,769]

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:

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 October 28, 2018 by Chock

[Chock 17,769]

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 October 28, 2018 by Chock

[Jetset408 108]

Lol

[FDEdev 955]

deleted

 

Edited October 28, 2018 by J35OE

[LH340fan 54]

Some days ago I did a flight from DUS to bilbao in the AS A320. I had to wait 10 mins for a gate on a taxiway. Instead of letting the engines on, APU on, and master 2 off. I DID experience some yaw at some point but under short taxi low speeds (<15 GS) it's alright. I didn't have a long distance to do but for the parking it may be a bit challenging if you arrive a bit too fast. (single side pedal braking might help- it's a default feature in the AS one) 

Actually I wouldn't recommend SET for a long distance, but rather when waiting for takeoff and you're let's say number 10, or there's no stand available. Cuz I presume that the amount you save won't be a big deal if you're moving. Actually IRL I have NEVER seen a SET, so it's not a common thing.

[pegruder 65]

On 10/31/2018 at 10:04 AM, LH340fan said:

Some days ago I did a flight from DUS to bilbao in the AS A320. I had to wait 10 mins for a gate on a taxiway. Instead of letting the engines on, APU on, and master 2 off. I DID experience some yaw at some point but under short taxi low speeds (<15 GS) it's alright. I didn't have a long distance to do but for the parking it may be a bit challenging if you arrive a bit too fast. (single side pedal braking might help- it's a default feature in the AS one) 

Actually I wouldn't recommend SET for a long distance, but rather when waiting for takeoff and you're let's say number 10, or there's no stand available. Cuz I presume that the amount you save won't be a big deal if you're moving. Actually IRL I have NEVER seen a SET, so it's not a common thing.

Funny you mentioned never seeing one.  I was on a jet blue flight a year ago departing JFK and it was a SET from gate to just shy of RWY 4L.  I think I even have it on video on my gopro as number 2 was just free spinning all the way down until fired up.  Ill see if I can find it actually.

[skelsey 765]

On 10/31/2018 at 2:04 PM, LH340fan said:

Actually I wouldn't recommend SET for a long distance, but rather when waiting for takeoff and you're let's say number 10, or there's no stand available. Cuz I presume that the amount you save won't be a big deal if you're moving. Actually IRL I have NEVER seen a SET, so it's not a common thing.

Depends very much on the airline, the airport and the crew -- there are times when it would be inadvisable to taxi on one engine (e.g. airports where the taxi route to/from the runway involves significant upslopes, if crossing an active runway is required, or if the taxi-out time is very short (subjective, but probably not worth it if less than about 10-15 mins as you need a couple of minutes to start the engine and warm it up anyway). Also many A320 series aircraft require the APU to be running in order to taxi on one engine (although there are some recent updates that allow single-engine taxi with the APU shut down).

However, don't underestimate the potential savings: the idle fuel flow on an IAE is about 360kg/hr (i.e. about 6 kg/min) per engine. So if you can delay starting one of them up for 15 minutes (not actually that difficult if you consider that it could easily be at least five minutes from starting the first engine before you even start moving by the time the pushback is complete and the after start actions are completed) you could be looking at a ~90kg saving.

Doesn't sound much individually, but multiply that by, say, 500 flights per day and the numbers start getting very big very quickly...

[FDEdev 955]

Another often overlooked item is the increased nosewheel tire wear during single engine taxiing. This does increase cost as well. 

Concerning the NEVER; I've approximately used to taxi to the stand on one engine on 90% of my flights (with longer taxi times than the minimum cool down period). 

[ahsmatt7 1,199]

There's something funky that is going on with how the engines provide thrust within the fslabs software. 

I tried v1 cuts the other day and when an engine quits, it's like the thrust is simply on or off. It doesn't feel organic at all. More like an on/off switch. Its wierd. The ground handling on the thing seems to always be super finicky.

I wouldn't be surprised if both of these factors play a role in single engine taxi characteristics.