DR 400 update

  • I guess we are just lucky to have any version of the Robin.


    Ray

  • Is it normal for the DR400 to respond different to power input than for instance the C172? When I let go of the elevator in the C172 and add power, the plane goes up, when I lower power the plane goes down. The DR400 goes either way: if it is going up a bit and I lower power it goes up even more, when it is going down and I add power it's going down harder. No matter what power I use it tends to keep on going where it was going. Also the elevator up is very sensitive: just a slight pull on my joystick and the plane jumps up.


    I am just curious if this is realistic behaviour...? I know the plane is mainly meant as an example on how to create a plane but I was wondering in how far the simulation of the plane is accurate.

  • I am just curious if this is realistic behaviour...? I know the plane is mainly meant as an example on how to create a plane but I was wondering in how far the simulation of the plane is accurate.


    I've not flown the latest update yet.

    As it was previously, the flight behaviour of the DR400 was pretty much realsitic, but the engine model was really not.

    Just by taking off at full power, RPM would rise to some 2'500 and, as the aircraft heaves into motion, prop speed would drop to some 2'300 rpm (???) before to very gently rise back to 2'400 rpm as the DR400 gains speed.

    Then when flying, the engine had a strong tendency to overrev.

    As for all aircraft in AFS2, power is totally independent from altitude, thus you need to exaggeratedly reduce cruise power to get realistic flight parameters.


    Comparing to the C172, I noticed the DR400 was modelled as a fixed pitch prop (which is correct), while IPACS cheated somewhat on the C172 parameters setting a slightly variable pitch prop.


    Applying the same cheat to the DR400 greatly improves engine behaviour. At takeoff @full power engine provides some 2'300 rpm, which is realistic, then RPM gently rise to 2'400 as the aircraft gains speed (correct), and 2'500 when levelling off.

    The engine still has a tendency to overrev, but far less than with original settings, and I can easily get a cruise power giving 2'400 rpm and 110-115kt, that's pretty much accurate for the 160hp aircraft.


    The power is still independant from altitude, that's a general flaw in AFS2 engine model, all aircraft are affected.


    Regarding flight behaviour, like all certified aircraft, the DR400 is a stable aircraft, meaning if you gain speed it tends to climb, if you reduce speed it tends to descend.

    As far as I flew the DR400 in AFS2, that's the way it behaved, but I haven't flown the latest update.


    There's no horizontal stab but a monobloc elevator, thus the real aircraft is very responsive in pitch.


    I can't exactly recount how many different DR00 models I've flown IRL, but for sure more than half a dozen, maybe ten.

    I never found 2 of them with the same panel outfit and exactly the same feel : each was unique, but still they all globally feel like a DR400. This one needs more right foot than the other one, I can move the seat further aft in this aircraft than in this other, making me sit more comfortable. Control surfaces feel lighter, more precise and responsive in newer aircraft than in older aircraft, which is normal...

    Anyway, flying the DR400 in AFS2 I really feel home, except of course engine behaviour as already stated. It's just like another member of the DR400 family.


    Cheers

    Antoine

    Config : i7 6900K - 20MB currently set at 4.00GHz, Cooling Noctua NH-U14S, Motherboard ASUS Rampage V Extreme U3.1, RAM HyperX Savage Black Edition 16GB DDR4 3000 MHz, Graphic Card Gigabyte GeForce GTX 1080 8GB, Power supply Corsair RM Series 850W, Windows 10 64 bit.

    Edited 4 times, last by Trespassers ().

  • if you gain speed it tends to climb, if you reduce speed it tends to descend.

    Thanks for the detailed reply. What I quoted is what doesn't seem to happen on my PC. Wonder if I am the only one or not. It still is a nice plane to have and fly but it just feels kinda odd to me.

  • ... while IPACS cheated somewhat on the C172 parameters setting a slightly variable pitch prop....


    ...The power is still independant from altitude, that's a general flaw in AFS2 engine model, all aircraft are affected....

    Wow wow wow... we are not cheating! Please don't try to spread false accusations :) The propeller in the C172 and DR400 are simulated as fixed pitch propellers, there is no input function assigned to the pitch control, just one static value. That constant value means constant pitch.


    And as mentioned before, the power does change with altitude. Marc has a Phd in physics, I doubt he would leave something this important away. The effect may be more pronounced on some real world engines than in others and our engine model might be one of the better performing kind, but the engine still flies in a low pressure, low temperature and low density environment and both the engine and prop therefor behave different at higher altitudes.

  • Hm, I've got some strange loading error.


    88.42-tmmodelmanager: loading dynamics begin 'aircraft/dr400///dr400.tmd'...

    88.42-tmfile_properties: WARNING: property 'Type' is not a member of type 'control_cylinder' hash=8879486950980732439.

    88.42-tmfile_properties: WARNING: property 'Direction' is not a member of type 'control_cylinder' hash=4116484178463478014.

    88.43-tmfile_properties: WARNING: property 'StepAngle' is not a member of type 'control_cylinder' hash=3630830562818136434.

    88.43-tmfile_properties: WARNING: property 'Type' is not a member of type 'control_cylinder' hash=8879486950980732439.

    88.43-tmfile_properties: WARNING: property 'Direction' is not a member of type 'control_cylinder' hash=4116484178463478014.

    88.43-tmfile_properties: WARNING: property 'StepAngle' is not a member of type 'control_cylinder' hash=3630830562818136434.

    88.43-tmfile_properties: WARNING: property 'Type' is not a member of type 'control_cylinder' hash=8879486950980732439.

    88.43-tmfile_properties: WARNING: property 'Direction' is not a member of type 'control_cylinder' hash=4116484178463478014.

    88.43-tmfile_properties: WARNING: property 'StepAngle' is not a member of type 'control_cylinder' hash=3630830562818136434.

    88.43-tmfile_properties: WARNING: property 'Type' is not a member of type 'control_cylinder' hash=8879486950980732439.

    88.43-tmfile_properties: WARNING: property 'Direction' is not a member of type 'control_cylinder' hash=4116484178463478014.

    88.43-tmfile_properties: WARNING: property 'StepAngle' is not a member of type 'control_cylinder' hash=3630830562818136434.

    88.43-tmfile_properties: WARNING: property 'Type' is not a member of type 'control_cylinder' hash=8879486950980732439.

    .....

    88.48-tmfile_properties: WARNING: property 'InputTransform' is not a member of type 'control_cylinder' hash=3962206370786267255

    ....etc.

  • Are you using the latest Steam version of Aerofly or are you using the DVD version?

  • Wow wow wow... we are not cheating! Please don't try to spread false accusations :) The propeller in the C172 and DR400 are simulated as fixed pitch propellers, there is no input function assigned to the pitch control, just one static value. That constant value means constant pitch.


    Sorry if that's misinterpreting from my side, we try to figure out by trial and error the secrets of definition files. ;)


    Compared to the fixed pitch DR400 propeller I noticed the C172 has and additional "pitch control" parameter where the governor is defined for the constant speed prop of the Baron, for instance :


    Code
    1. <[string8][PitchControl][0.323]>


    Adding this tweak and taking over the C172 propeller characteristics help a lot in my case making the DR400 engine behaviour less crazy, despite the original setting values pretty much match the manual.


    And as mentioned before, the power does change with altitude. Marc has a Phd in physics, I doubt he would leave something this important away. The effect may be more pronounced on some real world engines than in others and our engine model might be one of the better performing kind, but the engine still flies in a low pressure, low temperature and low density environment and both the engine and prop therefor behave different at higher altitudes.


    Well, there was obviously some improvement recently but I'm afraid the piston engine model is still far from the truth.


    At 2'000ft I have to reduce throttle down to less than 40% to set 2'400 rpm and cruise level at TAS 115-120kt which are common eco cruise parameters with the DR400, except you would need approximately 60% throttle IRL.




    Before this summer's upgrade, I could start the DR400 at 22'000ft and fly level still with some 50% throttle and would overrev the engine when increasing to full throttle, without even leaning mixture (mixture was not modelled, or just on/off).

    IRL, even by leaning mixture the engine would have immediately stopped.


    With latest upgrade I can only set the DR400 to some 15'000 ft, which is nearly (if not yet above) the highest altitude the aircraft can reach, so that's more realistic, but still you hardly need 50% of throttle to set 2'400 rpm and cruise level at TAS 100-105 kt, still without mixturing (full rich).

    Reaching such an altitude IRL request full throttle and careful mixture leaning or the engine stops.



    More common altitudes (for me, at least) when flying in the Alps, at 12'000 ft you hardly need 40% of throttle to set 2'400 rpm and cruise level at TAS 110 kt, still without mixturing (full rich).

    IRL you would have to lean almost all the way down and apply approximately 90% throttle to fly level (you still can gently climb).



    So, yes there are a lot of nice improvements in AFS2 and the latest DR400 - I'm still discovering new ones.

    The flight models are pretty good.


    But I would definitely not say the engine model is among the best performing, at least not for piston engines.


    A leaning command was added, it however linearly reduces power instead of increasing it as fuel mixture is not yet taken in account. Whatever the altitude, you will get the best power by setting full rich, which doesn't make much sense, but we know it's WIP.


    Other sims simulate engine leaning properly, though somewhat too responsive. IRL you need to lean very gently and wait for the result, because there are pipes between the carburetor and the cylinders.


    Cheers

    Antoine

    Config : i7 6900K - 20MB currently set at 4.00GHz, Cooling Noctua NH-U14S, Motherboard ASUS Rampage V Extreme U3.1, RAM HyperX Savage Black Edition 16GB DDR4 3000 MHz, Graphic Card Gigabyte GeForce GTX 1080 8GB, Power supply Corsair RM Series 850W, Windows 10 64 bit.

  • Thanks for the reminder about Trespasser's alt. ASI option. I just switched to it. It's great.


    The tmd download from here doesn't work now, but you can swap the relevant lines from the // airspeed indicator section


    For anyone doing this you can't just replace the code in the converted dr400, you have to replace the BMP file in the files used for conversion and tweak the TMD file and then reconvert.

  • Thank you Spit40 for the reminder, I’ll make a patch and upload it on the exchange platform.

    An archive with the converted texture and the tmd replacement file and there you go, no need to relaunch the converter...


    Cheers

    Antoine

    Config : i7 6900K - 20MB currently set at 4.00GHz, Cooling Noctua NH-U14S, Motherboard ASUS Rampage V Extreme U3.1, RAM HyperX Savage Black Edition 16GB DDR4 3000 MHz, Graphic Card Gigabyte GeForce GTX 1080 8GB, Power supply Corsair RM Series 850W, Windows 10 64 bit.

  • (...)I’ll make a patch and upload it on the exchange platform.

    Done. You'll find my DR400 Mod by Trespassers patch on https://flight-sim.org/


    Easy to install and remove.


    Each change is documented, original settings are commented for easy individual recovery.

    You may for instance easily revert to ASI in kph if you like.


    Current modifications are :

    - ASI gauge in kt instead of kph, with home-made texture.

    - Made pilot Thomas visible, easy swap with Edward and Robert (no girl, sorry)

    - Adjusted pilot POV ahead of pilot eyes

    - Tweaked prop parameters picked from C172 for improved engine behaviour

    - Improved ground steering and differential braking

    - Reduced CHT gauge needle speed for more realism

    - Reduced Oil Temp gauge needle speed for more realism

    - Reduced GyroSuction gauge needle speed for more realism

    - Reduced OBS1 deviation needle speed and damping for more realism

    - Increased Panel and instrument lights setting ranges

    - adjusted throttle, trim and flaps settings for inflight "clean" and "landing" start

    - switch default lights settings for typical beacon on, nav off, landing on, taxi off


    See readme file for details.


    Hope you like it.

    Cheers

    Antoine

    Config : i7 6900K - 20MB currently set at 4.00GHz, Cooling Noctua NH-U14S, Motherboard ASUS Rampage V Extreme U3.1, RAM HyperX Savage Black Edition 16GB DDR4 3000 MHz, Graphic Card Gigabyte GeForce GTX 1080 8GB, Power supply Corsair RM Series 850W, Windows 10 64 bit.