Hi there, I made a patch to FGPiston and FGPropeller for: - Using power table (RPM and Altitude) for accurate power if you have an engine power chart. - Using MAP table (defines relationship between throttle and Manifold Air Pressure) - Emulating Constant speed propellers with manual pitch lever (that limits the max pitch angle)
The patch and A6M2 test files are available at: http://macflightgear.sourceforge.net/wp-content/uploads/jsbsim/JSBSim_CSProp_PowerTable.tar.gz # use A6M2-jsbsim for test. This is in very early testing phase but is very interesting, so give it a try and send me some comments. Since macflightgear web site seems having a problem in accessing the database, I write the note here. [About Constant Speed Propeller for warbirds] With this patch, Prop Advance key (n/N) works as a pitch lever. When you press n, the maximum prop pitch increases. RPM goes down a bit but boosts up a bit to keep RPM. Then the prop works as a constant speed prop so throttle changes the pitch to some extend. With too excess / less torque, engine RPM increases/decreases. When you press N to bring the pitch back to the lowest, the prop works as fixed pitch prop. I'm trying to emulate the prop governor for more stable engine RPM, but currently not that good. To use this patch for your aircraft, you need to write the following tags to propeller config file. <minrpm> 1254 </minrpm> <maxrpm> 1777 </maxrpm> <pitchlimitter>1</pitchlimitter> <!-- This makes your airplane emulate warbirds' constant speed prop. --> and you also should write the following to the engine config file: <maxgovernorpressure>39.8</maxgovernorpressure> <!-- in inHg --> This describes how much maximum pressure the prop governor has to actuate engine for keeping engine RPM when the pitch is changed. it's still experimental so I use larger number. You can also change /fdm/jsbsim/propulsion/engine/governor-rate (from 0.0 to 10.0?). This variable is a multiplier for counteracting to the engine rpm change when pitch lever is moved. larger number increases much boost when pitch is being increased. The maximum pressure for this counteract is limited to <maxgovernorpressure> value described in the engine file. This is very early experiment so RPM and boost sometimes doesn't get stabilized well. [About Power table and MAP table] here is the power table for a6m2. columns are altitude in ft, first row is engine RPM. and the content is the power at a altitude with an RPM. you can also monitor the power at /engines/engine/power_hp <table name="C_POWER" type="internal"> <tableData> <!-- 0 1000 2000 3000 4000 4200 5000 6000 7000 8000 9000 10000 --> 0 3281 6562 9843 13123 13780 16404 19685 22966 26247 29528 32808 0 0 0 0 0 0 0 0 0 0 0 0 0 1800 628 647 629 565 505 496 450 395 345 305 268 225 1900 665 678 700 635 572 555 508 451 399 350 302 261 2000 688 713 733 704 646 624 574 512 450 397 346 299 2100 725 750 775 780 702 687 632 572 509 449 388 343 2200 749 775 802 829 772 752 698 630 570 498 437 379 2300 777 805 830 861 840 823 762 680 618 550 480 425 2400 804 830 862 893 910 890 825 748 673 597 526 464 2500 825 853 880 920 945 950 890 803 725 643 571 497 2550 833 870 898 938 964 969 908 819 740 656 582 507 </tableData> </table> Throttle / MAP table is very simple. it just describes the MAP value at given throttle value. it works good but can be more accurate when speed is considered. <!-- Throttle \ MAP --> <table name="C_MAP" type="internal"> <tableData> 0.00 0 0.30 22.44 0.80 35.43 1.00 39.37 </tableData> </table> Best, Tat p.s. Email address has changed. On Feb 15, 2008, at 8:53 PM, Tatsuhiro Nishioka wrote: > Oops, I didn't actually committed the JSBSim version of A6M2. > Now it's done. :-p > > Please give it a try! > > BTW, I have two minor problems on this: > - small vibration of tail gear. > - rotating right instead of left when start taxing. > > If you have any idea to solve these, please let me know. > > Best, > > Tat > > p.s. > On Feb 14, 2008, at 12:22 AM, Tatsuhiro Nishioka wrote: > >> Hi there, >> >> I'm making a JSBSim version of A6M2, and want to share with you guys about a >> constant speed propellers for WWII aircraft. >> >> First I tried a default prop configuration generated by Aeromatic, but the >> propeller pitch was adjusted automatically. >> So I removed <minrpm> and <maxrpm> tags from prop configuration file and the >> manual pitch control seemed working fine (Thanks to Ron for advice). >> Technically it's not a constant speed propeller anymore, but the behavior of >> both propeller and engine is getting closer to the descriptions in some >> books that I have. >> >> However, there came another big problem - too much engine rpm in cruising >> with lower pitch. >> I tried to adjust the power table to avoid this happening but no clue. >> The engine still exceeded way higher than the maximum rpm (more than 2000 >> above maximum) in the lowest pitch when cruising. >> Maybe I need to find the proper power / thrust correlations, but it doesn't >> seem possible to me. >> >> As a workaround for this issue, I modified the power table to have higher >> value in lowest pitch where advance ratio > 1.0 even >> thrust value is zero. This way, it seems working fine - the rpm of the >> engine stays a bit higher than maximum rpm. >> But I'm not sure if this is a proper behavior of the constant speed props >> for warbirds. >> If you have any better idea, please let me know. >> >> If you get interested, please check out A6M2 from CVS and give it a try. >> The pitch is set to the lowest for climbing. You need to adjust the pitch to >> maximum in cruising. >> Though the thrust/power table looks very weird, it's getting closer to >> zero's behavior I guess. >> >> Constructive comments are very welcome. >> >> Best, >> >> Tat >> >> p.s. >> >> I'm also willing to simulate zero's manual boost controller in JSBSim. (not >> sure if it is possible though) >> >> >> ------------------------------------------------------------------------- >> This SF.net email is sponsored by: Microsoft >> Defy all challenges. Microsoft(R) Visual Studio 2008. >> http://clk.atdmt.com/MRT/go/vse0120000070mrt/direct/01/ >> _______________________________________________ >> Flightgear-devel mailing list >> [email protected] >> https://lists.sourceforge.net/lists/listinfo/flightgear-devel > > > ------------------------------------------------------------------------- > This SF.net email is sponsored by: Microsoft > Defy all challenges. Microsoft(R) Visual Studio 2008. > http://clk.atdmt.com/MRT/go/vse0120000070mrt/direct/01/ > _______________________________________________ > Flightgear-devel mailing list > [email protected] > https://lists.sourceforge.net/lists/listinfo/flightgear-devel ------------------------------------------------------------------------- This SF.net email is sponsored by: Microsoft Defy all challenges. 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