Flybywire A320 landing bug?

[RaptyrOne 1,398]

4 hours ago, sd_flyer said:

This is interesting because behavior in the video is similar  to approaching critical angle of attack - controls become sluggish and not responsive as in normal flight

Yes, and this is why I suggested early on here that keeping your speed up does seem to help. I know some say it does not. I have repeatedly flow it to reasonable landings by keeping airspeed up at around 145-147 knots on the final approach and also making sure I do not sink below the glideslope. Dropping speed or sinking below the glideslope and then adding throttle to try and regain the GS on short final (three or more reds) can give it a mind of it's own. The other thing that seems to help me is to disconnect AP at around 1000 ft so you have some time in control, well before flare. You can leave AT on or disconnect, but keep your speed up and your approach on the GS.

I don't think Asobo have crossed axis' as has been suggested (flare vs bank) as then it would be happening on every flight. Because it is not happening on every flight means that it can be managed b y doing something. Software does not decide to do stuff because it feels like it. It's either 1 or 0 based in the conditions it is given at that moment.   

[daztheman70 22]

Everything works ok until I put flaps 1 and then it just goes crazy not sure why.

 

Daz

[2reds2whites 827]

8 hours ago, WestAir said:

This is a known bug with the default A320. The FBW mod has made no attempt to fix it.

There is currently no fix. For those wondering what it looks like, see this:

https://youtu.be/Q6Zz5zQthcc?t=5653

 

2 hours ago, RaptyrOne said:

Yes, and this is why I suggested early on here that keeping your speed up does seem to help.  

 

Whilst 'keeping your speed up' might help, it just changes the problem, as now you're far too fast for a conventional roundout and flare, and you'll have to land very flat. 

The claim that people are getting too slow during the flare is entirely debunked by the video provided by WestAir. The pilot is 36 knots above Alpha Max (solid red bar) and even if you were at Alpha Max you're not at the stall, just getting close to it. You wouldn't get wing drop on an Airbus with that Alpha Max until perhaps 108 knots. 

It is appallingly wrong. 

RaptyrOne - I realise that you are not saying it is right, and that your post is just a way to mitigate it, so my post isn't arguing or contrary to yours.

Edited October 5, 2020 by 2reds2whites

[RaptyrOne 1,398]

5 minutes ago, 2reds2whites said:

It is appallingly wrong.

Full agree, it is wrong. Coming back to that video, he is on the final approach at around 145-147 knots but also notice how he loses the GS quite early. That means early/sustained flare. I have found that these actions encourage the bus to behave badly.

It does make you not want to fly it though... nothing worse than finishing off a good 2-3 hour flight with a disaster on landing.

[Andreas Stangenes 1,628]

I will try this out and make sure to be at or above the GS into the flare and see if I can prevent the left banking. 

[2reds2whites 827]

30 minutes ago, RaptyrOne said:

Full agree, it is wrong. Coming back to that video, he is on the final approach at around 145-147 knots but also notice how he loses the GS quite early. That means early/sustained flare. I have found that these actions encourage the bus to behave badly.

It does make you not want to fly it though... nothing worse than finishing off a good 2-3 hour flight with a disaster on landing.

Well after he takes out the autopilot he gets THR CLIMB l CLIMB with ALT blue, which is insanity.

Whoever coded/approved it is incompetent, word not allowed, or just didn't care.

Edit: Whilst I understand the need for some censorship on the site, I'm not sure that censoring the word 'ig nor ant' is sensible.

Edited October 5, 2020 by 2reds2whites

[Andreas Stangenes 1,628]

Ok my findings so far (only did two flights in this experiment):

Equal for both flights is the focus is on the flare/short final. I tried to fly the vref speed which is well above protection range. The experiment is that I tried to stay above the glide slope at all times, ie, landing a bit further down the field because of this.

1. First test went ok. One of my smoother landings, but that isn't saying much. Before I could grease all my landings, but after A320 in MSF my best ones are around 180 ft/min. This one was around that. Wings didnt dip.

2. Second test was my worst flight so far. The wing dip actually happened more than a 100 feet AGL, and counter controls were very slow, and started an oscillating motion. Would consider a go-around but was interested to see how it would handle closer to the runway. Kept speed up until 20 ft agl. I stayed about half a diamond above the gs indicator at all times, but it didnt seem to help any. Speed was on AT and for my eye was the same as landing #1. I'm none the wiser other than the tip about being above GS doesn't seem to be valid.

However, he also mentioned a vref speed about 147 or so but the vref is weight dependant, so I will add about 7 knots to my speeds and test how that goes. 

 

Will report back. 

Edited October 5, 2020 by Andreas Stangenes

[nyfirefly11 55]

I’ve been practicing landings with the Sydney landing challenge the last few days, and at least once the plane rolled to the left at around 100ft agl.

I’ve also found that, at least in that challenge, if I use the a/p & a/thr to go below about 150kts (well above the stall), the plane loses all lift and sinks into the ground rapidly.

[Donstim 109]

11 hours ago, daztheman70 said:

Everything works ok until I put flaps 1 and then it just goes crazy not sure why.

 

Daz

Do you have the A320 mod installed?  The stable version of that mod can cause issues with flaps down because they reduced the lift coefficient in flaps down configurations. If this is your issue, delete the mod and install the latest master (not stable) version.

If this isn't your issue,make sure you don't have something else bound to whatever input you are making to extend flaps, make sure your controller is calibrated and has appropriate dead zones, if necessary, and cross your fingers!

[Donstim 109]

9 hours ago, RaptyrOne said:

Full agree, it is wrong. Coming back to that video, he is on the final approach at around 145-147 knots but also notice how he loses the GS quite early. That means early/sustained flare. I have found that these actions encourage the bus to behave badly.

It does make you not want to fly it though... nothing worse than finishing off a good 2-3 hour flight with a disaster on landing.

Note that he said he'd heard of the issue, but had never experienced it before. I'm kind of in the same boat- have maybe experienced it once or twice out of many landings. Most of those landing have been ulta stable with only slight control inputs needed to maintain path.

He also said that he had a bit of crosswind. I wonder if that is one of the factors involved?  MSFS seems to accentuate the small perturbations due to wind.

[Andreas Stangenes 1,628]

12 hours ago, Donstim said:

Note that he said he'd heard of the issue, but had never experienced it before. I'm kind of in the same boat- have maybe experienced it once or twice out of many landings. Most of those landing have been ulta stable with only slight control inputs needed to maintain path.

He also said that he had a bit of crosswind. I wonder if that is one of the factors involved?  MSFS seems to accentuate the small perturbations due to wind.

Are you perhaps flying mostly in calm wind?

[Andreas Stangenes 1,628]

12 hours ago, Donstim said:

Do you have the A320 mod installed?  The stable version of that mod can cause issues with flaps down because they reduced the lift coefficient in flaps down configurations. If this is your issue, delete the mod and install the latest master (not stable) version.

If this isn't your issue,make sure you don't have something else bound to whatever input you are making to extend flaps, make sure your controller is calibrated and has appropriate dead zones, if necessary, and cross your fingers!

Where have you read that the nx mod tweaks the lift coefficient? As far as I know, the flying of the aircraft itself is EXACTLY the same as default because the mods have done nothing to that aspect of the plane. 

 

Furthermore, I can debunk that it has anything to do with the mod itself, because I get this issue both with default and whatever is the latest master build (I download it almost daily). 

Edited October 6, 2020 by Andreas Stangenes

[Ixoye 1,812]

It seems I have to wait a while longer before I start flying airliners.

[Donstim 109]

6 hours ago, Andreas Stangenes said:

Are you perhaps flying mostly in calm wind?

Live weather. Based on the stability of the approaches, I would have to say that I don't think there was much crosswind in any of those approaches. I should have paid more attention, but since I wasn't having to correct for it, I really didn't even look at the wind direction.

6 hours ago, Andreas Stangenes said:

Where have you read that the nx mod tweaks the lift coefficient? As far as I know, the flying of the aircraft itself is EXACTLY the same as default because the mods have done nothing to that aspect of the plane. 

 

Furthermore, I can debunk that it has anything to do with the mod itself, because I get this issue both with default and whatever is the latest master build (I download it almost daily). 

I spend a lot of time on the team's Discord server, staying current with what they are doing and contributing where I can.  See https://github.com/flybywiresim/a32nx/pull/1029, and if you want more background, https://github.com/flybywiresim/a32nx/issues/1034#issuecomment-702604116 and https://github.com/flybywiresim/a32nx/issues/1014.

The post I was responding to regarding it potentially being due to the mod was one that said they had unexpected behavior as soon as they started putting flaps down (and other posts about unrealistic pitch attitude in the flare, not the specific wing drop issue you are talking about. Nowhere did I claim your issue may be caused by the mod, so there is nothing to debunk.

Edited October 6, 2020 by Donstim

[daztheman70 22]

On 10/5/2020 at 11:55 PM, Donstim said:

Do you have the A320 mod installed?  The stable version of that mod can cause issues with flaps down because they reduced the lift coefficient in flaps down configurations. If this is your issue, delete the mod and install the latest master (not stable) version.

If this isn't your issue,make sure you don't have something else bound to whatever input you are making to extend flaps, make sure your controller is calibrated and has appropriate dead zones, if necessary, and cross your fingers!

How do I find the different versions can only see one download on the site.

 

Thanks

Daz