For Skyboat: Improved supercharging for the DC-5's P&W 1830

[LesterBoffo]

So Skyboat mentioned on our last outing that the Douglas DC5 had no supercharging, and my assessment of this aircraft was that Helijah's Nasal assisted engine coding was gimping this aircraft.

So I'm going to post the new improved engine and propeller section coding with some caveats:

The "convert" Nasal file that supports the engine start-up and supposedly also provides more realistic engine instrument gauge inputs was a bugger to adjust after making these changes. You could leave the "convert" nasal as stock, but it will continue to make the engines kinda weak. I also changed the RPM gauges to actually read the engines' crankshaft RPM, not the geared down propellers' RPM.

Depending on if Skyboat can use an XML editor like NotePad++ I can provide the relevant entries in the convert Nasal.

Or I could just a link to the entire model in my Mediafire account. Mediafire has been a bastidge lately about cleanly uploading big size files, kinda why I want to do this piecemeal. At any rate here's the engines' coding snippet, the usual warnings here do apply. Make a back up of your YASim .xml before embarking on changes, yada, yada..

Code: Select all

  <!-- Engine left -->
  <propeller x="6.052" y="3.523" z="-0.369"
             mass="1184"
             moment="45"
             radius="1.82"
        blades="3"
             gear-ratio="0.479"
        min-rpm="650"
        max-rpm="1293"
             course-stop="2.0"
             fine-stop="0.5"
             cruise-rpm="1101"
             cruise-power="900"
             cruise-speed="178"
             cruise-alt="12700">
             <actionpt x="6.552" y="3.523" z="-0.369"/>
             <control-input control="ADVANCE" axis="/controls/engines/engine[0]/propeller-pitch"/>
             <piston-engine eng-power="1200"
                            eng-rpm="2700"
                            displacement="1829"
                            bore="5.5"
                            stroke="5.5"
                            compression="6.7"
             min-throttle="0.068"
                            supercharger="1"
                            turbo-mul="1.5"
                            wastegate-mp="42">
                            <control-input control="THROTTLE" axis="/controls/engines/engine[0]/throttle"/>
                            <control-input control="STARTER"  axis="/controls/engines/engine[0]/starter"/>
                            <control-input control="MAGNETOS" axis="/controls/engines/engine[0]/magnetos"/>
                            <control-input control="MIXTURE"  axis="/controls/engines/engine[0]/mixture"/>
             </piston-engine>
  </propeller>

  <!-- Engine right -->
  <propeller x="6.052" y="-3.523" z="-0.369"
             mass="1184"
             moment="45"
             radius="1.82"
        blades="3"
             gear-ratio="0.479"
        min-rpm="650"
        max-rpm="1293"
             course-stop="2.0"
             fine-stop="0.5"
             cruise-rpm="1101"
             cruise-power="900"
             cruise-speed="178"
             cruise-alt="12700">
             <actionpt x="6.552" y="-3.523" z="-0.369"/>
             <control-input control="ADVANCE" axis="/controls/engines/engine[1]/propeller-pitch"/>
             <piston-engine eng-power="1200"
                            eng-rpm="2700"
                            displacement="1829"
                            bore="5.5"
                            stroke="5.5"
                            compression="6.7"
             min-throttle="0.068"
                            supercharger="1"
                            turbo-mul="1.5"
                            wastegate-mp="42">
                            <control-input control="THROTTLE" axis="/controls/engines/engine[1]/throttle"/>
                            <control-input control="STARTER"  axis="/controls/engines/engine[1]/starter"/>
                            <control-input control="MAGNETOS" axis="/controls/engines/engine[1]/magnetos"/>
                            <control-input control="MIXTURE"  axis="/controls/engines/engine[1]/mixture"/>
             </piston-engine>
  </propeller>

So, thoughts, feedback...?

[SkyBoat]

Lester-- Thanks very much for sending me the supercharging code for the DC-5 engines. I had wondered why their performance was so anemic.

I can use notepad ++. I have had it for many years. However, I am far from fluent in nasal. So please send a set of instructions on how to correctly modify the DC-5's nasal file.

Since you indicate that adding the nasal after installing the yasim code can be problematic, I will wait until I get the nasal from you and do the conversion all at once.

Thanks again for your generosity!

Skyboat

[LesterBoffo]

Well Skyboat starting at line 386 in the "convert" nasal is this code snippet

Code: Select all

var torqpourcent = mb0  * 0.244259892526;

You want to change the decimal after the star-astrix to the decimal fraction ( 0.244249892526 ) I've posted above. do all 6 entries if you want, do at least two for both engines, mb0 and mb1.

hope this helps.

[SkyBoat]

[Lester-- Much appreciated! I'll let you know as soon as I get it installed or if I need to ask any questions.

[SkyBoat]

Hi Lester:

The DC-5 engines started the first fime. That's usually a very good sign.

I'm test flying right now. I'm at 7500 ft, KIAS set to 200, but the best speed I can make is 194 lkias. At max throttle Engine 0, is showing 1866.21 torque-ft-lb and 741.6 thrust-lbs at 2699 rpm . The yasim code puts the max rpm at 1293. Is that the crankshaft RPM? Also the manifold pressure is maxed at 32 inhg

The reading is the same for engine 1.

You mentioned in your first text:

I also changed the RPM gauges to actually read the engines' crankshaft RPM, not the geared down propellers' RPM,

My instrument panel still has the stock RPM gauge (two needles). With this lower engine performance I'd like to install your modified gauges.

Many thanks,

SkyBoat

After thought: Performance at 13120 ft per specs, throttle 100%. Autothrottle OFF
KIAS: 177
GS: 225
BRG: 087
Location: 7.177436N; 157.012010E (Western Pacific Ocean)

From "Browse Internal Properties" /engines/engine (0); Engine (1) gives identical reading.

RPM: 2699
Prop-thrust: 596.6
Thrist-lbs: 596.7
Torque-ft-lb: 1500.54
Man Press inHg: 26.0

[LesterBoffo]

Yeah this is why it's best to have feedback on the flying and handling of the aircraft.

The engines/engine[*]property tree generally reads the engine crankshaft RPM, at least for YASim flight models.

So there's a couple small tweaks you can try:

Adjust both engines and the "cruise" section of the YASim .xml from 178 knots to 198 knots cruise speed.

And in the same rows at the cruise section add an additional 0.5 to the cruise "pitch" section so it reads "2.5"

Also add the same amount to the "course-pitch" in the engines' sections and while your at, it change the name to "coarse". I think this is something Helijah misspelled, I'm not sure if it is all that important, but just in case. Syd Adams is responsible for the YASim property tree infrastructure for reciprocating, (piston) engines, and these entries are spelling sensitive.

You should be able to now throttle back to about 0.8~0.75 throttle @ about 12K altitude and elevator trim level the aircraft so it stabilizes into a level flight condition and have at least an average 220 knot surface cruise.. the indicated airspeed is important, but the ground speed is where you get the drag reduction that shows the true airspeed, which will vary with the wind direction and the strength of the winds aloft.

You should also remember that these are recip engines and will need their mixture leaned back at altitude. Open the property browser briefly to check that you maintain the best torque for the throttle and the mixture settings as you reduce throttle, you will need to trim back the mixture as you reduce throttle to cruise flight conditions. These engines should consume roughly about 61 to 69 gallons per hour per engine @ cruise, it will vary some.

When in doubt check the property browser.

[SkyBoat]

Hi Lester,

I flew the DC-5 this afternoon and was very pleased with the great improvement in power. I had a KIAS of 191 at 13500 ft, which produced a ground speed of 223 kts!

Not bad. Not bad at all.

Thanks again for the supercharger code and the other "tweaks" to get the optimum performance from the P&W R-1830 Twin Wasp 14 cylinder engines.

SkyBoat