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A/T speed problem


Mik75

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Hi!

First of all, I have to say that I really like your new Airbus!

The graphics are fantastic and the sounds are very realistic, the whole thing gives you a really immersive experience!!!

I also like the idea of a "lite" product which gives you the abilty to load a flight, get in the Airbus an take off within minutes.

Still it is complex enough to create the right atmosphere, well done!

But the autothrottle is really struggling to hold the dialed in speed. During a few touch and goes, I chose 200 (flaps 1 deployed) as the speed for my patterns, but most of the time the A/T tended to overspeed and reacts to slow.

Plus, the typical "beep beep" while disengaging A/T is missing.

Otherwise, it´s almost perfect, a real joy to fly, even by hand!

Keep up that great work!

Greets,

Michael

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Is this happening in level flight or when you're descending, if so, what is your descent rate?

I believe the A/T 'beep...' has been noted and will hopefully be added in SP1.

Chris

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Hi Chris!

Thanks for the fast answer.

It also happens in level flight. After T/O, I pull the thrust levers back until SPEED is anounced in green on the PFD, 200 is dialed in at the MCP, and shortly after that, I level off at 2500 ft for my pattern. And almost every time, the speed overshoot at min. 220 (critical speed with flpas 1 deployed)

On the other hand, when on short final, the speed is set to 147, gear is down, flaps are full and I am descending with a normal rate of descend, the A/T doesn´t seem to have any problems to acquire and maintain that speed...

So the problem is more present at level flight I´d say...

Greets,

Michael

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Hi Michael. First thing is that you shouldn't be pulling the throttle back til you see speed (I need to check but this is most likely disengaging the autothrottle at that point).

On takeoff ensure you see FLX or TOGA on the top right of the PFD and ensure the A/T green light is illuminated. After takeoff wait for the Airbus to tell you to reduce thrust to THR CLB. You should stay in this for the duration of your flight!

You can now pull (right click) the speed knob and dial in 200kts. It should keep this within +/- 10kts most of the time.

Pulling back til you see speed in the PFD is putting the thrust under your control and not the autothrottles.

Chris

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Hi Chris!

Surely I waited for the PFD to tell me to pull the throttles back to SPEED (LVR CLB) after T/O.

The green light on the A/T is illuminated and I right clicked the speed knob (pull it to me) on MCP to dial in 200 afterwards.

The marker on the PFD is on the 200, but somehow the A/T reacts to slow and doesn´t take away enough thrust, so the overspeed occurs...

Greets,

Michael

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Hi Chris!

Surely I waited for the PFD to tell me to pull the throttles back to SPEED (LVR CLB) after T/O.

The green light on the A/T is illuminated and I right clicked the speed knob (pull it to me) on MCP to dial in 200 afterwards.

The marker on the PFD is on the 200, but somehow the A/T reacts to slow and doesn´t take away enough thrust, so the overspeed occurs...

Greets,

Michael

Michael,

When the PFD indicates LVR CLB, pull the throttle back to THR CLB and not SPEED. :)

Chris

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Sorry Chris, you´re right.

But when LVR CLB is indicated, and I move the levers back, SPEED in green will appear on the PFD, right?

Greets,

Michael

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Sorry Chris, you´re right.

But when LVR CLB is indicated, and I move the levers back, SPEED in green will appear on the PFD, right?

Greets,

Michael

Yes Michael, you are correct. My Bad! I was getting myself confused between Select Mode and Managed Mode.

From takeoff you should be in Managed Mode, then THR LVR and move into THR CLB. Going to Select Mode will indeed indicate SPEED in green on the PFD.

I've just tried it and can't say I saw a problem.

Which aircraft are you using?

Chris

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Hmmm, you said that the A/T should keep the speed within +/- 10 kts.

That´s definitely not true for me, at least maybe within +/- 20 kts...

During the tests I used the A 321 with Air Berlin paint.

Greets,

Michael

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Good point...

I used cold fronts, so winds up to 20 kts were present.

To be honest, I don´t remember which direction the wind came from when the overspeed occured.

Greets,

Michael

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  • Aerosoft

Yes Michael, you are correct. My Bad! I was getting myself confused between Select Mode and Managed Mode.

From takeoff you should be in Managed Mode, then THR LVR and move into THR CLB. Going to Select Mode will indeed indicate SPEED in green on the PFD.

I've just tried it and can't say I saw a problem.

Which aircraft are you using?

Chris

Just to enforce this, after take-off pull the throttle back to the CLIMB setting (it will be shown in the FMA) and then just leave it there until you hear "retard". Sounds strange, but that's how the Bus wants it. In an airbus it should not be called a throttle but a trust setting selector.

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Nice to hear that the beep will be added!

Correct, I didn't touch the thrust mode selectors at all after selecting climb thrust (SPEED)! ;-)

Maybe a possible work around would be to dial in a slower speed in the MCP.

But it would be nice if the Airbus would be able to hold a selected speed a little better.

Somehow it seems as if I was the only one with that problem...

Greets,

Michael

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  • Aerosoft

Nice to hear that the beep will be added!

Correct, I didn't touch the thrust mode selectors at all after selecting climb thrust (SPEED)! ;-)

Maybe a possible work around would be to dial in a slower speed in the MCP.

But it would be nice if the Airbus would be able to hold a selected speed a little better.

Somehow it seems as if I was the only one with that problem...

Greets,

Michael

Ahh no, you are not the only one. It was a long debate in development, the engines as they are now run at the right N1's, provide the correct thrust etc, but for some reason that does not propel the aircraft fast enough. It's a rather well documented issue. Today we have found out that it seems to affect some systems more then others and that a vital bit of information we need to decide what's the best way to solve this. In the end we'll most likely end up with a mixed solution where everything is a bit different then it should be.

MS sorted out the issue by giving the default Airbus 263% the thrust it should have, let's not go that way!

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Good point...

I used cold fronts, so winds up to 20 kts were present.

To be honest, I don´t remember which direction the wind came from when the overspeed occured.

Greets,

Michael

Hi Michael. I gave it a try with that weather preset, I did get upto around 215kts instead of the set 210kts but it slowly reduced and became stable.

As Mathijs said, it is looking like it can vary system to system.

Chris

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  • Aerosoft

As Mathijs said, it is looking like it can vary system to system.

You got no idea how developers react when I tell them that. "You mean to say the air is more slippery on one system compared to another? Are you out o......"

Could I get some ideas on the fps when things like this happen?

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The issue is solely with the amount of thrust being commanded by the auto-throttle. For example, if the CLB N1 limit is 96.2%, the engines still will only be at about 80% N1 no matter what. That is what is causing the issues with thrust, not some crazy misunderstanding of the Airbus's thrust ability due to over-usage of the default A321 (who in their right mind flew that anyway?).

Drew

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Just to enforce this, after take-off pull the throttle back to the CLIMB setting (it will be shown in the FMA) and then just leave it there until you hear "retard". Sounds strange, but that's how the Bus wants it. In an airbus it should not be called a throttle but a trust setting selector.

Lol, well I never disengaged A/T during beta testing :P Should have tried ;)

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Ralf, we are aware this is an issue at the moment. In the meantime I would suggest that you leave the speed in managed mode but take the Altitude into select mode and use V/S instead.

You should then find that you can maintain 280-300kts with a v/s of +2000ft. Of course as you get to higher altitudes you will have to reduce this to maintaing speed/mach.

Chris

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Ralf. I'm not aware of an updated installer, however I don't think a reinstall will help.

Keep in mind your Takeoff Weight and make sure you're not too heavy. I would switch to V/S passing 10000ft and set it between 1800-2200ft/min depending on the aircraft weight, don't wait til +20k ft as you will find it difficult to regain the lost airspeed.

Above 20k ft you will have to reduce the rate of climb ~1000ft. During testing I made many flights following this procedure and didn't have any problems.

Also bear in mind that between 20000ft - 30000ft the transition is made from airspeed to mach, so even if all is well don't expect to be at 300kts when reaching 30000ft. The airspeed will decrease as the air gets thinner the higher you get. Mach 0.65 or greater is what you should be looking for above 20000ft.

Chris

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So.. what you're saying is that this is as intended?

Drew

I don't think that it is as intended, it's just how it is at the moment and it's being looked into. My understanding is that managed mode was simplified, so it is basically doing a trade off between airspeed and vertical speed (it's a very basic VNAV).

I have found select mode quite successful and would recommend this as the option to use most of the time. With most payware addons I stick with V/S as I'm never happy with how there VNAV works.

Hopefully the managed mode on Airbus X will be improved in time.

Chris

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