[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):

[lve0200]

@MisterChocker

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.<

Could you elaborate or provide links, which issues you wanted to solve w/ your mod. Lifting the lower end for taxi is clear, but IMHO everything else modifying the curves will be counteracted by the AP/ATH. I attach an excellent document telling about the interaction between AP, FD and ATH. in Brief the AP tells what he wants and the ATH sets the thrust. So if the AP says up 500ft/min, ATH sets some thrust. If you go now and mod the power curves so that for this thrust setting, more (or less) power is provided, the ATH will just set another thrust to that the request from the AP will be fullfilled. Only if the ATH comes to its limits say 100% and this gives not enough power, then modifying the upper points of the power curves would give some extra performance.

Airbus_Descent_Monitoring_1.pdf

[derl30n]

@lve0200 Engine performance has been reworked to match real life performances through various flight stages. Taxi, Takeoff, Climb, Cruise and Approach. Also work on the fuel flow has been done. Please do go ahead and look at the documents used for the changes, they can be found in the pr. https://github.com/flybywiresim/a32nx/pull/1295

I should also state that your excel table does not represent engine performance good. It only shows performance at M.1.

[lve0200]

I have tried to reproduce quite a few issues regarding this "problem". All turned out the pilots were not flying the plane correctly.

Hold on! Decending @ 210Kts during APP gives me at best -1000Ft/min. (w/out brakes) According to the a.m. performance chart, this is less than the -1500Ft/min and w/out reserve. So what am I doing wrong? It can be perfectly possible to fly vanilla APPs w/ only -1000Ft/min, but what do you do w/ strong tail winds, or when ATC wants you to stay up until the last possible moment??

[lve0200]

I should also state that your excel table does not represent engine performance good. It only shows performance at M.1.

Appart from fuel flow and other non performance relevant changes, the file compare showed clearly that only N1 values were the relevant power concerning changes. My excel sheet compares these changes to the original data of Asobo.

[MultiMediaWIll]

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

You're missing the point. The A320 should be able to follow the reasonable requests from ATC. I was following the altitude restrictions of the STAR no problem. The problem occurs when you have a busy airspace and the ATC assigns you speed restrictions. The current A320 can't follow the speed restrictions and then slow down fast enough when the restrictions are lifted to descend at approach speeds. There's no way this is similar to real life.

[derl30n]

@lve0200

@ 210Kts during APP gives me at best -1000Ft/min

Do you use managed descent or open descent? Managed descent seems to be broken.

only N1 values were the relevant power concerning changes. My excel sheet compares these changes to the original data of Asobo

yes but still you are only comparing for M.1. M.1 sould be ~70kt CAS at SL.

[lve0200]

Do you use managed descent or open descent?

Open decent;

yes but still you are only comparing for M.1.<

there are no other N1 values in the engines.cfg file! In my excel the X-Axis is the thrust, Y-Axis is the N1 value and each color of the curves represents settings from 0.1 to 0.9 (I guess weight)

[derl30n]

@lve0200 Using VS 1200ftm and still having ~35%N1 to maintain speed. With quite a bit of tailwind.

[lve0200]

Hhm, could you try w/out setting a manual V/S? Just set speed to 210 and make an open decent say from 5000 Ft down to 2000Ft and see what you get in terms of throttle and ROD. May be there's something w/ the AP or ATH Thank you Just realised on the Copilot PFD that you were at 250 Kts, YES OK, that's all fine. So please repeat as I said @ 210 w/out V/S. Around busy APTs, ATC asks you 9/10 already long b4 decent to fly "minimum clean speed" due to traffic, and then you have to decent at that speed, rapidly in narrow slots!

[derl30n]

@lve0200 will do, GD? or 210? I am asking because GD is the most effective glide speed.

[lve0200]

GD? Chose minimum clean speed, AFAIK, the little green circle. (may be wrong, sorry) What you can barely fly w/out having to set flaps

[lve0200]

Use minimum clean speed, AFAIK, the little green circle (may be wrong). Just what you can barely fly w/out having to apply flaps

[derl30n]

@lve0200

Use minimum clean speed, AFAIK, the little green circle (may be wrong). Just what you can barely fly w/out having to apply flaps

GD means Green Dot, also known as minimum clean speed. And GD is a safe speed to fly, not a speed you can barely fly.

[derl30n]

@lve0200 Are you flying with a custom livery?

[lve0200]

NO

[derl30n]

Hard to tell, I get 800 to 1300ft/m at 7500ft in Open Descent at GD and in clean config. With speed brakes 1500 to 1800 ft/m at 6000ft in Open Descent at GD and in clean config.

[donstim]

The 0.1 to 0.9 are Mach numbers. Changes to the n1-fn table will change the airplane's climb and descent capability in open climb and open descent modes because these modes are are at a set N1 level (max climb N1 or idle). Airplane pitch is used to control speed, and the rate of climb /descent falls out from that. It can be changed by changing configuration (flaps/slats/gear/speedbrakes) or speed. The rate of climb will naturally reduce as you get higher as climb thrust reduces, and the rate of descent will decrease as you get lower as idle thrust increases. With approach/landing configurations, idle thrust is raised even higher to allow TOGA thrust to be achieved more quickly in the event of a go-around.

[lve0200]

With approach/landing configurations, idle thrust is raised even higher to allow TOGA thrust to be achieved more quickly in the event of a go-around.

This is another point of concern 4me. On short final, I see thrust levels on or almost on Idle to achieve the 3° G/S (-900Ft/min) @MisterChocker I observed the lower you get the lesser the sink rate. 800-1330 @ 7500 but check again around 2000. And pickung up this point, make a landing and check your thrust level on short final.

[derl30n]

@lve0200 yes at 2500ft I got 700ft/m right now. Thrust on approach is ~41% N1 at SL. (depends on your weight)

[lve0200]

SL?

[derl30n]

Sea Level

[donstim]

Airbus' recommended procedure for a higher rod during initial approach is to deploy Conf 1 early and use speedbrakes as needed. As I stated previously, I was able to maintain ~2000 fpm rid at Conf 1 with speedbrakes, which provides 500 fpm "reserve" over the 1500 fpm approach rod in the chart you provided.

[lve0200]

Airbus' recommended procedure for a higher rod during initial approach

Yeah, but ATC might have other priorities

[lve0200]

Hey guys, I looked a bit into the Issues, which lead to the mod of idle thrust. It was about surface friction, which cannot be changed due to the SDK. So the decision was to mimik this by increased idle thrust. Lets face it, the effect we got from this is a flaky decent performance in lower altitudes. I propose as a compromise to reduce the idle thrust (as I did in my file) to something in the middle of the mod and the original. Then we have better decent and better (although not perfect) taxi behaviour and when eventually a new SDK is out, things can be modded again. my 5 cts worth

[donstim]

First thing of piloting to understand, atc is a very poor term. Atc does not control the airplane. The pilot does. The 2nd thing to understand, airplane performance has limits, and the pilot must work within those limits. Informing the controller when what they are requesting is beyond other the pilot's, the operator's, or the airplane's limits is expected.

[lve0200]

Hey man, I'm not a CPL, but a PPL and I spent much time in Airliner's cockpits b4 9/11. I can tell you, if in Heathrow, Singapore, Hongkong or Charles de Gaulle, the Controller tells you "maintain FL xxx", " Expedite decent to yyyy", etc. you'll not going to argue that YOU are the pilot.

[donstim]

I understand there have been comments/statements that ground friction is too high. What is the basis for this belief - how does one separate out ground friction from thrust? Is it friction, thrust, or both? The same comment applies to in-air drag vs thrust.

[donstim]

If you can't do it, you sure better argue that. This is rapidly going nowhere.

Edit: Sorry, argue is the wrong term. The response is simple "unable," followed by what it is that you are unable to do.

[lve0200]

we're getting side tracked. In the a.m. reference perf chart, a ROD of 1500Ft/m 4 APP is indicated. This reference has to be fullfilled (by the plane or AB) or respected (by ATC). Recommendations of AB are OK, but not mandatory. And as we just learned from MisterChockers check flight we've got 700Ft/m, at 2500Ft, which is not enough, or do you want to apply speed brakes on final?

[derl30n]

we're getting side tracked. In the a.m. reference perf chart, a ROD of 1500Ft/m 4 APP is indicated. This reference has to be fullfilled (by the plane or AB) or respected (by ATC). Recommendations of AB are OK, but not mandatory. And as we just learned from MisterChockers check flight we've got 700Ft/m, at 2500Ft, which is not enough, or do you want to apply speed brakes on final?

your "a.m." reference is not for A320-251, its for classic A320 without sharklets.

[Benjozork]

Alright people, I'm going to lock this as discussion/debate about what proper behaviour is should not happen on GitHub issues, which are strictly for tracking confirmed and understood problems. We simply cannot manage this if there is so much noise.

Please debate this on discord and open an issue when there is a confirmed, verified by pilots problem with the flight model.