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Donstim

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Posts posted by Donstim

  2. Posted

    6 hours ago, Stearmandriver said:

    Unsure about Airbus, but the 737 does have 4 autobrake settings that can be used for landing and that target a decel rate: 1, 2, 3, and Max.  Max does not give you maximum brake pressure, it's just another decel rate (too much, on a dry runway.). Only RTO gives full available brake pressure, and cannot be used on landing.  If you want the full 3,000psi to all brakes on landing in a 737, you'll stand on the brakes yourself - max manual braking does yeild full brake pressure.

    Double oops for me. Realized that the A320 has only 2 after I had written the original post, then mistakenly subtracted one from the number of 737 autobrake settings as well. Thanks for noticing and correcting it. Good point about "no autobrake" effectively being a setting as well.

  3. Posted

    4 hours ago, Donstim said:

    Neither the Boeing autobrake RTO setting nor the Airbus autobrake Max setting target a deceleration rate. They both deliver max hydraulic pressure to the brakes. The Boeing autobrake system has 4 different landing settings, while the Airbus system has 3.

    Oops, I meant 3 and 2 for the number of autobrake settings that can be used for landing (and that target a specific deceleration rate). 

  5. Posted

    8 hours ago, lwt1971 said:


    And this is on MSFS 2020.. with 2024 it'll only get better as MS/Asobo revamps the flight dynamics/physics engine and also provides much requested capabilities/flexibility in the SDK for aircraft developers. Some of the 2024 rework such as addressing the one real problem area currently in the MSFS FDE, ground handling, is now partially backported to MSFS 2020 and will release with SU15. PMDG and other devs all plan on taking advantage of this new ground handling in their FMs soon after, so keep an eye out for that in future fix updates.
     

    Keep in mind that both CFD and the new ground handling parameters of SU 15 can still have issues that make them either unnecessary or unsuitable for at least some airplanes. The A32NX does just fine, in fact better, without CFD than with. In preliminary tests so far with SU 15, the new ground handing parameters do not appear to adequately replace or improve upon what can already be done pre-SU 15.

  6. Posted

    Not that it changes your conclusions, but the axes scales are not the same for your comparison. This makes the SU14 spikes twice as large what is used for the SU15 beta graph. (They will still be large compared to the SU15 beta spikes, but you should at least show them using the same scale.)

    • Like 1

  7. Posted · Edited by Donstim

    Some testing of the ground parameters using the default Asobo A320NEO...Starting at EHAM 36R with wind set to 18 m/s from 271 degrees in MSFS weather UI, so about 35 knots crosswind from the left with the airplane pointing straight down the runway.

    First, SU14 with flight model cfg altered to not cancel out crosswind at any speed: SU14 Asosbo A320NEO Ground Xwind.mp4

    Next, SU15 with same flight model cfg as for SU14 (new ground contact stuff not added): SU 15 Old ground contact parameters Gound Xwind 2.mp4

    Then, SU15 with the new ground contact tuning parameters copied over from the C172 (not suggesting the exact same values would be appropriate for the A320NEO): SU 15 New ground contact parameters Asobo A320NEO Gound Xwind 2.mp4

    New ground contact parameters from the C172 are as follows:

    ground_new_contact_model_rolling_stickyness = 0.5; default = 1.0
    ground_new_contact_model_up_to_speed_lateral = 1000.0 ; default = 0.1
    ground_new_contact_model_up_to_speed_longitudinal = 1000.0 ; default = 1.0
    ground_new_contact_model_gear_flex = 0.005 ; default = 0.0
    ground_new_contact_model_gear_flex_damping = 5 ; default = 0.0

    and finally, SU15 with the old ground contact parameters again, but this time with the default cancelling of crosswinds at low speed: SU 15 Old Ground Contact parameters but with Xwind cancelling Ground Xwind.mp4

    So, there does not appear to be anything new in this case between SU14 and SU15 without the new ground contact parameters included. (The default values for the new ground contact parameters are low enough that they don't really have any effect if they are indeed used when not included in the cfg file.) This airplane will weathervane into the wind, and the airplane will skid the nose wheel to go in that direction when you have the wheel turned all the way toward the other direction

    What is of some interest is that with the new ground contact parameters, you get a similar effect to cancelling out the crosswind at low speed for this case, but with some major differences. First, you need a lot more thrust to make the turn against the crosswind, and secondly, once you start turning, if you idle the engines the crosswind will cause this airplane to start turning in the opposite direction from which is started.  That, of course, does not happen with the old ground contact parameters with canceled out crosswind.

    (Caution about trying this yourself. For some reason, in SU 15 when I selected to start on the runway at EHAM 36R, it started me on 27. I had to taxi to 36R to do the test. I would have changed locations, but I had already done the SU14 test on that runway.)

    • Like 1
    • Upvote 1

  8. Posted

    7 hours ago, FOD said:

    Thanks folks. I had tried everything suggested except to delete the Community Folder - this results in MSFS doing a full 130gb reinstall!  With my internet speed this will take all night but at least tomorrow I will have a new clean MSFS to work with……….

    Read the linked posting I provided. There is no need to delete the community folder. 

  10. Posted

    Be aware that Vapp in the A320 is not the Vref (which he refers to as REF) that G550flyer is referring to. Vapp already includes a minimum 5 knot additive to Vref.

    FlyByWire recommended control settings can be found here: https://docs.flybywiresim.com/fbw-a32nx/settings/#controllers (though this is not meant to stop you from experimenting with your own controller to find the best settings for you)

    • Like 1

  14. Posted

    6 hours ago, Bob Scott said:

    Generally, I think that currently, the relative few MSFS airliner add-ons that have reasonably good systems modelling also tend to have reasonable flight physics modelling.  That would be the PMDG 737s, the Fenix and FBW Scarebusses, the Leonardo Maddog, the iniBuilds A310, and the WT 787/747.  Once upon a time in a sim far, far away, I used to do extensive flight testing of add-ons against r/w data--time-to-climb trials, unreliable airspeed power setting profiles, fuel burn profiles etc.  I even re-wrote the FDE for a few add-ons that I particularly liked to get the physics more in line with real-world data.  That's the most definitive means I know of to validate major aspects of the flight physics modelling, but I haven't seen anyone doing that sort of third-party testing in quite a while.  There are also other considerations that are more difficult to measure, e.g. moments of inertia and related stability, control effectiveness across the airspeed envelope (especially roll/yaw behavior at high AoA in swept-wing aircraft).  I don't think any of them demonstrate the fidelity that would qualify them as an FAA-certified ATD, but most of them are close enough to be a reasonable approximation for our purposes.

    I believe that "realism" at least as the term applies specifically to the flight model--which boils down to physics--is measurable, and evaluating it should be based on those metrics.  Any discussion that lacks data is just a comparison of subjective assessments, and will reflect the experience levels and the biases of the evaluators, and that's what makes a lot of these discussions devolve into something of a scatter plot, with opinions all over the map.  Hard data is hard to come by...

    We published such validation quite some time ago for the FBW A32NX flight model....https://flybywiresim.com/notams/a32nx-flight-model/

    • Like 7

  15. Posted

    10 hours ago, Hyper14 said:

    Hi, I recently flew the flybywire a320 and it was really good except for one thing. 
    When I started my descend, I selected my desired altitude and started a managed mode descend. Usually other aircraft descended at about 1800-2300 feet per minute but this aircraft straight up started to go 4500-5000 ft per minute. Obviously I reach my altitude too early and I had to hold my flight level for a few minutes, before starting the descent again.

    I was wondering, am I doing anything wrong, is there any solution to this?

    ps: in the fenix a320 I did the same thing and it worked perfectly.

    The stable version does not have full vertical descent management (VNAV). It will attempt to obey any altitude constraints, but will do so by flying an open descent to reach them. An open descent uses idle thrust and adjusts pitch to stay on the target airspeed. Thus, it will give you the highest descent rate for the configuration you're in that maintains the target airspeed and will generally reach the constraint altitude early. Depending on your weight, the descent rate can easily reach 4-5,000 fpm in the early part of the descent if you are light.  Similarly, in climb, the airplane can achieve 5,0000 fpm initial climb rates if you are light (for example, 60T or less) 

  17. Posted

    1 hour ago, ThomseN_inc said:

    Good evening,

    So today i decided to install and fly the FBW 320 again after being absent for some time. But i have great problems controlling it during taxi. It's all set up as per FBW's documentation (Thrustmaster A320 stick/ Rudder/tiller not separated) but it gets out of contoll immediately when trying to turn.

    Lets say i'd like to do a slight left turn, i gently turn the tiller left but the plane first starts veering to the right for about 10 degrees and then suddenly slams to the left ending in a constant overcorrection. Looking from the outside i can see the frontwheel following my steering commands exactly but the plane seems to slide anyway as described above. I usually end up in the grass.

    I am sure that i'm missing something here. Maybe some can point me in the right direction?

    Any tipps appreciated.

    -Latest Experimental Version

    -Thrustmaster 320 stick

    -Set up as per Manual

    -No issues with other planes

     

    Best regards,

    Tom

    From the FlyByWire documentation:

    FlyByWire A32NX | Assistance Options
    The A32NX is not compatible with the Microsoft Flight Simulator assistance feature "Auto-Rudder". It is required to deactivate this feature in MSFS.

    We recommend turning off all assistance features in MSFS as they interfere with the A32NX systems.
     

    • Like 1

  18. Posted · Edited by Donstim

    On 2/16/2023 at 9:41 PM, Hatch76 said:

    It’s been a few months since I flew it. So maybe it’s been updated since. 

    Hi, just wanted to follow up with you on this.  I see that there was an issue identified last year about this time citing an unrealistically high glide ratio (26:1) for the A32NX: https://github.com/flybywiresim/a32nx/issues/3322. Does this sound similar to what you were experiencing?

    There have been several flight model updates since then, the most recent being about a month ago.

    A Google search for A320 glide ratio shows several research studies (e.g., https://www.researchgate.net/publication/279217100_Is_Green_Dot_Always_the_Optimum_Engines-Out_Glide_Speed_on_the_Airbus_A320_Aircraft) based on a clean glide ratio of 17:1, and a full flap, gear down landing configuration glide ratio of 9:1. The Airbus FCOM gives a descent rate of 2.5 NM/1000 ft (glide ratio of 15:1) with all-engines-inoperative at green dot speed clean. The landing procedure for all-engines-inoperative is to use CONF 2. In this configuration with gear down, the FCOM provides a descent rate of 1.6 NM/1000 ft (glide ratio of 9.7:1).

    Tests at 60T with the FBW A32NX provided the following results:

    Clean at Green dot speed: 3.2 NM/1000 ft (glide ratio of 19.4:1)

    CONF 2/gear down at 163 KCAS: 1.5 NM/1000 ft (glide ratio of 9.1:1)

    CONF FULL/gear down at Vref+10: 1.4 NM/1000 ft (glide ratio of 8.5:1)

  19. Posted · Edited by Donstim

    33 minutes ago, Hatch76 said:

    I still have to respectfully disagree. It glides better than any aircraft I have ever flown in real life, GA or commercial. There’s no way it gently glides at a slow decent rate when fully dirty and fuel cutoff. 

    Yeah, that doesn't sound right. I assume your airplane is up-to-date? Just want to also note that spoiler deployment is inhibited in CONF FULL and only about 1/2 extended in other configs with autopilot on. Was the airplane fully configured before cutting fuel to to the engines? What speed were you trying to maintain? 

    If neither engine is producing thrust, then it isn't a matter of weight, only L/D. I will be glad to give this a check as it is well outside the normal envelope and not covered by the available data, but I'm out of town until Sunday. 

  20. Posted · Edited by Donstim

    2 hours ago, Hatch76 said:

    I’d normally agree with that (and still do) but when you drop the gear, flaps, spoilers, and kill the engines it descends way too gradually. It just lacks a feeling of weight to it. 

    Flight performance, including with flaps and spoilers extended, gear down, engines at idle match the real airplane very well. 

    https://flybywiresim.com/notams/a32nx-flight-model/

    Oh, and engine - out performance is modeled as well, so you can practice your V1 cuts. 

    • Like 1

  21. Posted

    Regarding the earlier discussion on setting pitch trim for takeoff, see https://docs.flybywiresim.com/pilots-corner/beginner-guide/preparing-mcdu/#perf and the "setting pitch trim advice" here: https://docs.flybywiresim.com/pilots-corner/beginner-guide/engine-start-taxi/#after-engine-start.

    For the vertical guidance symbols, see https://docs.flybywiresim.com/pilots-corner/advanced-guides/flight-guidance/vertical-guidance/nd-symbols/?h=sym

    There is a wealth of information in the Fly-By-Wire documentation. You may want to start here - https://docs.flybywiresim.com/pilots-corner/beginner-guide/overview/

    • Like 1
    • Upvote 1
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