[BUG] New thrust levels make proper descent impossible

[flytester]

Mod Version

Latest master

Describe the bug

Thrust settings are much higher than before. The aircraft can taxi on idle thrust, which is good&realistic. Big problem is the incapability to descent at a normal rate. I suspect the thrust-setting on idle is too high. The aircraft can't descent more than around 1000 feet per minute during approach probably cause this would lead to a airspeed higher than managed or selected. The low descent rate is far from realistic, the A320 should at least be capable to descent 2500 ft per minute in this phase of flight. Since performing a realistic approach is not possible anymore, the mod has become of little use, wich I regret A LOT. Hope you guys fix this!!

To Reproduce

1. 2. 3.

Expected behavior

Actual behavior

References

Additional context

Was this working before/when did the issue start occurring? Seems to be a problem with the latest master.

Is this a problem in the vanilla unmodded game? No.

Discord username (if different from GitHub):

[flytester]

Addition: even full speedbrakes or flaps don't solve this issue.

[vlbreda]

Ran into exactly the same problem. Shame the stable version isn't working since the update, didn't have the problem with descending.

[TheoBearman]

Can also report this. Seems to be a particular issue during descent.

[Benjozork]

We are continuously working on an improved flight and engine model on the master branch - therefore we do not guarantee realistic conditions at all times on master, as it's a development version where we do risky changes to gather feedback.

A patched stable version is coming today that will work for MSFS 1.10.7.

[vlbreda]

@Benjozork: I think it is in no way meant as critisiscm, by no one. Just reporting the issues we encounter.

[Benjozork]

Of course, just explaining what our philosophy is when it comes to master. Stable patch is coming today.

Your criticism is very welcome and appreciated - we need it to improve.

[korundar]

I find it harder to slow in approach than in previous versions. It seems more like a 777.

[donstim]

Can you provide more specifics, like what altitude, configuration, weight, and autopilot/autothrust modes?

All modern airliners are pretty slippery. As you get lower and slower, you have less capability to go down and slow down.

[vlbreda]

I can provide the following: plane's weight is 130.000 LB, speed is around 210 kn, ap/at engaged, approach phase, all in managed mode. Problem occurs with flaps retracted and extended, there's little difference. For example: flying the ILS 25 approach into Luton (EGGW) the STAR requires you to descent from 5000 ft to 2000 ft over a distance from 7 nautical miles. This is not possible, even with full flaps, gear down and speed brakes in use.

My best guess: the plane is tuned for realistic taxi performance (at idle thrust). This same tuning of idle thrust makes that the plane can't descent rapid enough without exceeding the managed or selected speed. Idle thrust still gives far too much thrust.

As you mentioned, slower means less capability to go down. But the performance as it is now in the dev-version of the mod is a far cry from reality.

[vlbreda]

This short youtube-video shows exactly what the problem is. Plane is at 8000 ft, approach phase is activated, plane slows down (very slowly). After that, a (magaged) descent to 5000 feet is flown (at 1 min 09 in the video). Descent-rate is barely 1000 feet/minute. In real life, this is about 2500 feet/minute (to quote a real A320-pilot: 'The A320 can descent like a flying piano).

Hope this makes the problem clear to you and you can fix it!

[]https://www.youtube.com/watch?v=5q2d1JFO7wU&feature=youtu.be

[lve0200]

Just to confirm, that the issue is still there even in 1.10.7.0 & master as of 31/10. APP 8000->1700 at -1700ft/min, 210 Kts, with IDLE, FULL Speedbrakes, Flaps 1 and Gear DOWN!

[vlbreda]

Found out a workaround for the problem: -download and install the latest dev-version -replace engines.cfg file with file from your latest working mod-version (the file to be replaced is located in ..Community/A32NX/SimObjects/Airplanes/Asobo_A320_NEO -Descent rate is no around 1700 ft/minute during approach, 2000 ft/minute with gear down/flaps 3 -If you haven't got the old engines.cfg file anymore, send me your email-adress and I'll send it to you.

[krieke58]

@vlbreda : please send. 👍

[lve0200]

OK, here now my 5 cts worth. I did a file compare of the 2 questionable engine.cfg files. The latest from Asobo and FBW. The only relevant difference is the "n1_and_mach_on_thrust_table" line. To make things visible, I transferred everything into an Excel sheet. A picture tell more than 1000 words or numbers. The Excel is attached. For those w/out Excel, here the picture. I think they talk for itself. Left FBW, right Asobo.

xx.zip

[MultiMediaWIll]

I too can confirm this is a problem. I have been struggling to slow down the plane for the last week. In fact a few days ago I was completely unable to descend and follow VATSIM ATC's instructions since the plane would not slow down even with speed brakes (this was a few days ago so not sure if the speed brakes have since been fixed). I have the latest dev version.

[vlbreda]

This is the engine.cfg file that fixes the problem. engines.zip

[Benjozork]

I want to remind everyone that the stable 0.4.1 version functions with the latest MSFS patch and does not contain the experimental flight model changes.

[vlbreda]

@Benjozork : the stable version that is installed using the downloader was not properly working the night of sat oct 31th. Maybe it is working by now.

[Benjozork]

Try to install it manually.

[derl30n]

@vlbreda

This short youtube-video shows exactly what the problem is. Plane is at 8000 ft, approach phase is activated, plane slows down (very slowly). After that, a (magaged) descent to 5000 feet is flown (at 1 min 09 in the video). Descent-rate is barely 1000 feet/minute. In real life, this is about 2500 feet/minute (to quote a real A320-pilot: 'The A320 can descent like a flying piano).

Hope this makes the problem clear to you and you can fix it!

[]https://www.youtube.com/watch?v=5q2d1JFO7wU&feature=youtu.be

can't watch the video, it's on private

[lve0200]

My little bit of nightly. 1st at all, if I'm violating any kind of rules here, I apologise and promise not to do it again. The admins here may feel free to delete my file! Looking at the 2 engine.cfg graphs from above, I could not refrain from creating my own personal 3rd one. Hence I took the original Asobo file and modified the lower end 20%-30% to something in the middle of FBW and Asobo. The new graph is attached. Above 30% everything is original Asobo. I am personally quite happy with the mod, altough in the absence of any reliable performance tables, everything remains personal gusto. The plane does not start rolling on idle, which I find reasonable, but it takes only a little thrust to overcome the initial inertia and then it keeps rolling (very slightly decelerating) on idle. Decent looks better to me, w/ -1600ft/min @ 210Kt w/out any brakes. Those who want to give it a shot, the file is attached, as well as the excel and the graphs. Desktop.zip

[derl30n]

Yes the current engine model in the master/dev version is not realistic, it solves a couple of issues with the engines and flight model to improve the flying performance of the aircraft. Work on a proper long term solution is being done right now, which will be as realistic as possible. #1580 Note: We are also developing a new engine model from scratch which will deliver real life performances in every situation. Because this is quite a task, it takes a lot of time.

@lve0200 I find that quite offensive to publish a solution and not talking to us on discord to give proper feedback, just my personal opinion.

[derl30n]

@flytester Following the chart below and properly configuring the aircraft during approach will help massively. This clip shows how to: https://www.youtube.com/watch?v=uOhrr1irBLg

[derl30n]

@vlbreda Descent performance varies from situation from situation. There is no fixed value. Peak descent performance is at 29314ft with 36868kg at M0.780 CAS300.0 TAS 461.0 IAS 250

[lve0200]

I find that quite offensive to publish a solution and not talking to us on discord

Sorry, I don't know what/where "discord" is, and how it works. I also apologised for eventually violating rules, if any. Just wanted to help...

[derl30n]

To respond to the descent rate problem, I am able to apply a small formula to calculate my required distance for descend to a given altitude.

It is altitude divided by 1000 times 3 altitude / 1000 * 3

Additional to make a more precise calculation for e.g. TOD

speed component: for every 10kts higher then 200kts add 1 nm. wind component: for every 10knt headwind component sub 1nm. For tailwind do the opposite.

[derl30n]

@lve0200

Sorry, I don't know what/where "discord" is, and how it works. I also apologised for eventually violating rules, if any. Just wanted to help...

Discord is a free communication platform with lots of features. With this link you can join our discord server.

[donstim]

I can provide the following: plane's weight is 130.000 LB, speed is around 210 kn, ap/at engaged, approach phase, all in managed mode. Problem occurs with flaps retracted and extended, there's little difference. For example: flying the ILS 25 approach into Luton (EGGW) the STAR requires you to descent from 5000 ft to 2000 ft over a distance from 7 nautical miles. This is not possible, even with full flaps, gear down and speed brakes in use.

My best guess: the plane is tuned for realistic taxi performance (at idle thrust). This same tuning of idle thrust makes that the plane can't descent rapid enough without exceeding the managed or selected speed. Idle thrust still gives far too much thrust.

As you mentioned, slower means less capability to go down. But the performance as it is now in the dev-version of the mod is a far cry from reality.

Tried flying that approach using an EHAM-EGGW flight using the current developer version. Being U.S.-based I'm not that familiar with flying in Europe. I could not find the approach procedure you are referring to that requires you to descend from 5000 ft to 2000 ft over a distance of 7 nm. I found and used the procedures shown below, which have you descend from 8000 feet at Casey (or Abbot) to 6000 feet, thence to the ILS capture altitude of 3000 feet just past Brookway. There was at least 10-12 nm to do that, and it was no problem in managed speed transitioning to CONF 1. Used a bit of speedbrake to reduce the speed from green do to S, but probably didn't need to. At S speed with CONF 1, I had 700-1000 fpm ROD or 2000 fpm with speedbrakes extended. Once at 3000 feet, it is a normal 3 degree glideslope, which is not an issue with this mod.

For your example of needing to descent from 5000 to 2000 feet in 7 nm, at a VAPP of 129 with full flaps, you would need a 1000 fpm descent rate. I'll have to go fly it again to check that, but I don't think I would have any problem maintaining that as there seemed to be plenty of downpath ability on the normal 3-degree glide at 7-800 fpm that I flew (i.e., thrust was not at idle as it should not be).

Maybe you could point out where I went wrong?

[vlbreda]

@MisterChocker

About the youtube-video: it's public now, sorry for the inconvenience. This is the link

I searched the internet and asked a few A320-pilots what to take for a 'normal' descent-rate on the A320. Got one answer so far:

''3000 fpm is considered normal at one company that I worked for. Obviously, we can deviate within reason. I have routinely descended at more than 3000fpm in non-emergency situations. Aggressive stepdowns on a STAR, controller requests expedited descent for traffic, slam dunk from 10,000ft+ (cleared for visual, hand off to tower, immediately cleared to land), etc.''

About hte STAR: keep in mind that these are published to be used by all aircraft types, not just the A320. ATC knows you're in an A320 and will tell you to descent at a rate suitable for your aircraft, both in MSFS as in real life.

Found a star (EHAM 36R via Artip transition) in MSFS to show you fast descents are required. Of course MSFS might differ here from the real world, but fast descents are required in densely populated areas to reduce noise. In this example you have to descent from 8500 to 2000 ft in just a few NM's!

[vlbreda]

@Benjozork : Hi Benjamin, you suggest to do a manual install. I have to confess I am a total nitwit in the world of Github, Discord, etc. Where do I find the files to do a manual install? On the FlyByWire website? Thought by using the A32 Downloader I would be safe all the time :)

[derl30n]

@vlbreda

First, I wouldn't trust the ingame flight planner. I am not sure if the distance is scaled properly but thats looking not right to me. About the noise thing, using speed brakes actually increases the noise, using IDLE thrust and continuous descends are proper economical ways of descending. Also take a look at comment the above.

[joniatus]

@vlbreda that's not a star. You put in a direct arrival to ils. The in game planner is not going to descend you properly. Pull up an actual arrival chart (not in game) and fly it. There are no issues managing decent and approach. It's not realistic to deploy speed brakes and descend 5000fpm while slowing from .80 to vapp in 30 seconds

[vlbreda]

@Jonatius: it's a rather extreme exemple, you're right. This topic however is not about the realism of the MSFS flightplanner, but the capabilities of the A320. Plane should be able to reach 2500 ft/minute descent in all phases of flight, without use of speedbrakes.

[derl30n]

@vlbreda

it's a rather extreme exemple, you're right. This topic however is not about the realism of the MSFS flightplanner, but the capabilities of the A320. Plane should be able to reach 2500 ft/minute descent in all phases of flight, without use of speedbrakes.

where do you get those numbers from?

[joniatus]

@vlbreda it's literally what you're basing your claims on. Yeah provide a reference that you can descend at 2500fpm in landing config without gaining speed. All I'm saying is go fly an actual arrival and approach procedure and you'll find you can meet restrictions just fine.

[joniatus]

I'm pretty sure the people having trouble with their descents are using in game planner restrictions which are often incorrect and are not actually looking at and following charts

[derl30n]

I'm pretty sure the people having trouble with their descents are using in game planner restrictions which are often incorrect and are not actually looking at and following charts

they probably adopted to the space shuttle physics of asobos 320 LMAO

[vlbreda]

@joniatus, misterchoker : there is a difference between the figures on the chart and what a plane can actual fly. As I mentioned earlier, these charts are fit for ALL types of aircraft, not just the A320. So charts are not a good reference to judge whether the A320 mod meets reality.

Some sources I can recommend to you: youtube channels Captain Joe and 320 sim pilot. These channels are run by real A320 pilots. Watching this footage is very informative!

[derl30n]

@vlbreda Well I was hoping for proper documents of the A320-251 not YouTube channels. Btw Captain Joe never flew an A320-251. How do I know? Cause AB never had 251s

[lve0200]

Here's probavbly a reliable reference: https://contentzone.eurocontrol.int/aircraftperformance/details.aspx?ICAO=A320 and here, how to fly possible APPs: https://www.researchgate.net/figure/Low-Drag-Low-Power-Flight-Procedures-4_fig1_225006763

[lve0200]

Adding comments to the above charts, I would say that the current N1 settings do not allow for the indicated RODs w/out applying massiv brakes (gear, flaps, speed brakes) and that there should be probably a "reserve" of 500ft/min.

[ischmal]

Perhaps we're not all on the same page here...

I also found this to be a huge problem after the mod was updated to support the latest game patch. Having said that, the latest dev release also seems to have resolved this for now, so hopefully we can just disregard this altogether at this point.

[Benjozork]

@ischmal, the 0.4.1 release contains no flight model changes.

[MultiMediaWIll]

@vlbreda that's not a star. You put in a direct arrival to ils. The in game planner is not going to descend you properly. Pull up an actual arrival chart (not in game) and fly it. There are no issues managing decent and approach. It's not realistic to deploy speed brakes and descend 5000fpm while slowing from .80 to vapp in 30 seconds

The plane does have issues managing decent and approach. I was flying an actual STAR into Portland, Maine the other day on a VATSIM event. I was completely unable to follow both the speed restrictions and altitude assignments when getting vectored to the ILS due to the fact that the plane would not slow down no matter what. I ended up being way too high to intercept the ILS and had to manually override the AP and blow 240kts on short final in order to make the landing. Something is definitely off.

[ischmal]

@Benjozork you know, I couldn't find any commits to explain this, but I figured I was just missing something. Perhaps this is actually far more bizarre than I thought... is anyone able to confirm that they're still experiencing this then? Maybe Asobo snuck it in with their CTD fix somehow. Very strange.

[vlbreda]

@lve200: That's a splendid chart you provide! Thanks! No it's all clear. 3500 ft/min to FL100 and 1500 ft during approach are not met by the dev-version of the mod this topic is about. Hope Misterchoker and Joniatus studie your chart, so they can become even wiser than they are yet.

[lve0200]

GUYS, stop the powerplay!!! The dev is not ready, yet! This was clearly stated! Until now we got an AB320 about magnitudes better than the Asobo! I would appreciate discussing possible solutions rathern than trampling on the problem!

[joniatus]

Oh but I thought it was 2500fpm for all phases?? I have no issues meeting those decent rates and getting fully configured for landing. If you give me the specific star I'd be happy to test it. If the vatsim controller had you deviate from the altitude constraints that caused you to be 240 on short final then ask for a go around.

Show a little respect, @MisterChocker put in a ton of work making the plane actually enjoyable to fly until they rework the fbw. Is it perfect? Of course not, but throwing out speed brakes and diving and slowing down simultaneously is stupidly unrealistic so if that's what you want go fly the default. Otherwise just follow the charts and you'll be fine

[vlbreda]

Come on, please don't confuse humor with disrespect! I think everyone appriciates the work which is put into this project, there's no doubt about that.

[derl30n]

@joniatus

Show a little respect, @MisterChocker put in a ton of work making the plane actually enjoyable to fly until they rework the fbw. Is it perfect? Of course not, but throwing out speed brakes and diving and slowing down simultaneously is stupidly unrealistic so if that's what you want go fly the default. Otherwise just follow the charts and you'll be fine

Thanks for the appreciation of my work! Please go ahead and try to reproduce this issue. I have tried to reproduce quite a few issues regarding this "problem". All turned out the pilots were not flying the plane correctly. I should also state, that during the development our QA department as well as our IRL A320 Pilots have worked and tested the changes. We have a good quality control to ensure the changes we make do what they are designed to do. Please feel free to join our discord to contribute to this mod.