Focke Wulf Fw200-A Condor

[Ivan]

By the way, go back and look at the definitions I posted earlier.
I was trying to tell you that the numbers you were listing were not actually the Advance Ratio.
You were actually listing Propeller Pitch Angles.

- Ivan.

[aleatorylamp]

Hello Ivan,
OK, fine! Propeller pitch angles then refer to each of the graph lines ranging from 15 to 65. Of course... Thank you!
For the moment, my Qbasic program is giving me the advance ratios from which I can read the prop efficiency then...

Before that, however, I´ll see about the Hurricane propeller tables though.
You do have quite an eye for things, don´t you? That´s included in the "empirical intuition"!

I ´ll let you know how it develops!
I was actually quite looking forward to some real butchering, but maybe it´s a better idea to try something not so gory first, just in case we can save ourselves all the hassle.

OK! I´ve put in the Hurricane´s table 512, and I´m completely speechless, flabbergasted, amazed...
A quick test reveals the following maximum speeds:
>at 300 ft, 226.6 mph, just 0.2 mph lower, and Hp is exactly 720!
>at 9800 ft, 241.3 mph, only 0.5 mph slower, and Hp is the same as it was - 654 Hp!
I´ll do the rest of the tests tomorrow, but it looks like we´ve got a winner here!

How on earth could you identify this just like that?
The Hurricane engine is 1030 Hp in CFS, and higher in reality on some versions...
How would that propeller so quickly appear to be so useful?

I´ll gladly do without the butchery! Here we´ll apply the law of minimum effort...
I´ll just adjust the Oswald factor ever so slightly to get S.L. speed up by 0.2 mph!

I still can´t believe it...
I ´ll celebrate with some Sweet Sherry for desert. To your health!!

Cheers,
Aleatorylamp

[Ivan]

Hello Aleatorylamp,

Just got back from Dinner and Grocery Shopping

Regarding how I picked the Hurricane Power Coefficient Table:
You are looking at the horsepower of the engines.
I suggest that you look at the formula for Power Coefficient instead.
Power Coefficient is basically a measure of how hard the propeller is to spin.
The Hurricane runs about 50% more power but also is swinging a larger propeller and is geared which makes the propeller easier to spin.
Another interesting note is that the actual Propeller rotational speed is nearly the same between the FW 200 and the Hurricane Mk.I.
(The propeller reduction gear ratio is 1.484)
When you are doing the calculations, don't worry about the Units of Measure too much because although it changes the number you get as output, you are just comparing numbers between different aeroplanes and the UOM cancel out.

I recommend that you adjust speed by a different method than Oswald Efficency.
That value is a modifier to the induced drag and at cruise and maximum speeds, induced drag is a VERY small component of total drag.
You will probably never see this in the FW 200, but increasing Oswald Efficiency numbers will increase the speed bleed in maneuvering and also have a much greater effect at low speeds.

Instead, I would suggest the following:
Drop the Airframe Drag slightly.
This number is very granular, so the effect will be probably more than you really wanted.
THEN, note the propeller pitch angle at maximum speed at Sea Level (328 feet).
226 MPH happens to be exactly 1.0 Advance Ratio, so if you adjust the Table 511 Efficiency down at that location, you should be quite close.

The reason I would do things this way is because in general, the Propeller Efficiency in the stock CFS Tables tends to be overly optimistic in my opinion and should be adjusted downward a bit if you have a reason. The efficiency also is a very finely adjustable value.

Let me know how things work and of course, please send me an updated version.

By the way, I will have a Soda, Tea or Coffee instead of Beer.
I was just commenting that typing is a terribly slow way to communicate compared to just having a conversation, especially if we had a simulator and a couple laptop computers and the Internet to find formulas and references.

With the Ki-61-Id, I already have some pretty good performance, but need to adjust how fast the propeller gains speed on take-off.
Right now, it conflicts with a flight test report.
There are a couple other aeroplanes that are affected (such as the Type Zero Mk.II fighters, so it makes sense for me to figure out a consistent method of generating propeller tables instead of hand editing them.

- Ivan.

[aleatorylamp]

Hello Ivan,
OK, how about some green tea then?
So, the set of numbers in the bigger Hurricane engine plus prop with gearbox, serve for the Condor. A nice surprise.

Ok, I ´ll have a look and see if I can follow your instructions to get that tiny edge of an performance increase out. Sounds like a piece of cake! An interesting way to finely adjust the speed.

I´ll let you know how it goes. Thanks very much!

Update:
OK! It´s almost perfect.
I lowered Zero lift Drag by 1 AirEd unit, and then went for Prop Efficiency Table 511.
At the first try I raised Pitch angle 35 graph to 1, smoothening out the surrounding ones, but performance rose by 4 or 5 mph, which was too much. Possibly I could have increased Zero Lift Drag by another unit, but I didn´t try.

Then I cancelled the first changes and this time raised the graph only very slightly, from 0.89 to 0.91, smoothening out the surrounding ones again, and the result is almost perfect. I just have to make some even smaller adjustments to get S.L. max speed down by only 0.3 or 0.4 mph now, and then check at higher altitudes. I´ll post the .air file when I´m done.
Thank you very much again!

Update 2:
It´s very interesting to see how this propeller efficiency issue works.
So, if I´m right, for a Maximum Speed adjustments, once you know the pitch angle from the Beckwith gauge, you go to the corresponding pitch angle graph and adjust the crest. Then, for Cruise Speed adjustments, after getting pitch angle, you use the formula to calculate the advance ratio, and obtain the point on the corresponding pitch angle graph to adjust that one.

Now I´ll see how it works out with the cruise speeds.

Cheers,
Aleatorylamp

[Ivan]

Hello Aleatorylamp,

Green Tea will work, but if I drink a lot of it, it should be decaf.

The big EEEEEEK is because of how you interpreted my instructions.

Hopefully the reasoning described below makes sense.
With the new Hurricane Mk.I Power Coefficient Table, you are close.
VERY close.
Performance is slightly under and with the really great mechanics we have, should be slightly Higher, not Lower than specifications (unless there is a reason why it should not be).

So, the first step is to Drop the Zero Lift Drag.
That should raise the speed by a couple MPH and if this were my project, I would leave it there.

Since you are trying to be more exact, the next step would be slow the aeroplane back down.
Reducing Thrust would do that,
so you want to slightly REDUCE efficiency where it matters in Table 511.
So going from 0.89 to 0.91 makes no sense.
It should go DOWN, not UP!
These are Double Precision floating point, so the adjustments can be VERY fine.

Where should the adjustments be made?
From what you posted earlier, the Sea Level speed was closer or less below the target than speed at altitude.
That means when you change the Coefficient of Drag, you would probably need to bring the SL speed down more than altitude speed.

Here you got lucky.
With this Engine / Propeller, your SL speed is at 226 MPH which is exactly Advance Ratio 1.00.
This would affect altitude speed also but less.
If you are trying to adjust altitude speed more, go for Advance Ratio 1.20 instead.

- Ivan.

[aleatorylamp]

Hello Ivan,
Thanks for your helpful comments. So I can improve it even more now!

Following your instructions, I had put the larger Propeller diameter back in. This needed a reduction in Zero Lift Drag, so I reduced it by one point, from 58 to 57. It was not completely enough to compensate for the larger propeller, and required a very slight increase in Prop efficiency.

Had I made a greater Drag reduction, I would have noticed that Prop Efficiency had to be corrected in the opposite direction!

S.L. Performance is now only 0.3 mph fast, and higher up it´s about 0.5 mph faster, all quite OK.
Cruise speed manifold pressure settings have also improved slightly compared to the ones from the pilot´s manual. The differences are a little smaller, so that has also improved.

But: It seems that it can be improved further, by reducing Zero Lift Drag a little more... perhaps by two or three points, so then of course, propeller efficiency will need to be reduced instead of increased, and the Manifold Pressure settings for Cruise speeds will fall into place!

Which is what I will do after another cup of tea!

As always, thank you very much... This is all very interesting.
Cheers,
Aleatorylamp

[Ivan]

Hello Aleatorylamp,

I get the misunderstanding now. I was figuring that you would keep reducing the Zero Lift Drag until you got a speed increase over the amount you needed.

The reason I choose this method is that from a realism standpoint, 0.89 is a pretty high Propeller Efficiency.
I would hope to see something in the 0.80 to 0.85 at Maximum Speed.
Now keep in mind that this is just from a bit of reading and a bit of experimenting with AIR files so if you want to do things differently, you own the project.

The problems I am trying to address with my own projects are that the Propeller Pitch Range is limited to around 23-53 Degrees.
The high speed range of cruise to maximum level speed are more or less correct, but the propeller is lugging at the low "maneuvering" speeds and not getting off the low pitch value and not generating the amount of thrust (efficiency) that I would want.
This is with the A6M3 Model 22 and A6M5 Model 52 Type Zero Carrier Fighters.
That is also why I never continued the path and released a A6M3 Model 32 version.
The flight model just didn't quite do what I wanted and I didn't have a means of correcting it.
It is also a problem with the A6M2 Model 21b, but is less noticeable because the propeller pitch range was different with the engines on the "Mark I" fighters.
The Zeros were known for having quite excellent low speed acceleration which meant that they could restore energy lost to maneuvering very quickly. Since I cannot do that, I compensate a bit by reducing the energy lost in maneuvering by having an Oswald Efficiency number that is a bit lower than it should be.

With the Ki-61-Id, the flight test mentioned that the propeller came off the low speed stop at a bit over 100 MPH just after take-off. Mine is about 20-30 MPH too high which bothers me, but makes no real difference from a performance standpoint other than making the acceleration a little too low at the end of the take-off run.
The reason I chose the Ki-61 to do the experiments on is that it is a simpler problem overall with much less in the way of cascading effects.
This is not to say that the flight model is correct; It just happen to be about where I want it to be.

Thus I need to be able to tune just a part of the Power Coefficient Table and as long as I am doing that, I might as well be able to generate the whole curve instead of just knowing specifically where to poke to get the effects I am looking for. Smoother curves are better.

- Ivan.

[aleatorylamp]

Hello Ivan,
From what you are describing about the models you are working on, some behaviour details seem to be more difficult to reproduce on the sim model than others. Then it is all the more gratifying when something specific does work! The details you are working on seem to be very specific and quite complicated. Good luck!

Usually I don´t find so many details available for the older models I work with, and something similar is happening with the Fw200. The maximum speeds are falling in place very well, but strangely enough, they were better with my slightly increased Prop Efficiency and less reduced Airframe Drag, than with the last tests after reducing Airframe Drag further, and also reducing Prop Efficiency a little.

Sea-Level speeds ended up a few mph on the high side, and at altitude there were only very marginal increases of 0.5 or 0.2 mph, but I think I have discovered why.

Strangely enough, the specific Manifold Pressure details for the three or four cruise speeds mentioned in the pilot´s manual just wouldn´t fit in correctly, but I deduced why - it´s a really stupid thing: They come from the documentation referring to one of the units of the Fw200-A0 limited production run, which were built while the first 3 initial prototypes were still being tested, and some of these fitted the 800 hp BMW 132-H or -L engines!

So obviously the 720 Hp engines on the prototype machine that flew the Berlin-New York record flight need different manifold pressure settings for said cruising speeds! That took a while to sink in... so I can discard that information. The lower Hp would also account for why it´s not working to increase altitude performance.

So it seems that the air file with the first modification of Table 511 after incorporating the Hurricane´s table 512 is more correct.
Anyway, it´s very pleasing how this is all turning out thanks to your indefatigable counselling!

I´m just preparing the new spec sheet for the performance of the new ungeared, 9.7 ft propeller engine, and I´ll post the new .air file. BTW, you are right about the 0.89 efficiency being too high for advance-ratio 1. It´s at 0.8585 - the 0.89 come from a higher pitch angle graph peak to the right! When I was adjusting the peaks at first, it wasn´t all that clear to me where I was. Sorry!

Cheers,
Aleatorylamp

[aleatorylamp]

Hello Ivan,
As requested and promised, attached below are the updated FD and Performance document for the Fw200A (V2) Condor I am working on, (2nd and 3rd prototypes). Incidentally, V1 was the presentation prototype and had 760 Hp Hornet engines and slightly different wings.
The propeller is now ungeared, 9.7 ft in diameter, Table 512 comes from the Hurricane, and Table 511 is slightly tweaked to correct S.L. max. speed. Cruise speeds coincide with general specs described for the Fw200A, i.e. 0.7 ATA for Eco-Cruise and 0.8 ATA for Cruise.
I forgot to mention: RPM is a bit low at 2025 all round, instead of 2050. This coincides with what happened of other models, e.g. Zeppelin Staaken RVI and AT-9 Fledgling, and could be something to do with my computer. I remember you were getting correct RPM readings on your machine.
Cheers,
Aleatorylamp

[Ivan]

Hello Aleatorylamp,

I will take a look when I get a chance.
I will be out of town for a couple days.
Internet and Email access will be via cell phone, so although I can get messages periodically, I won't try to type anything significant.

- Ivan.

[aleatorylamp]

Hello Ivan,
Not to worry, I hope you have fun. I´m also taking my Easter Week off classes. A well earned holiday is good for anyone and everyone. No hurry with looking into the .air file, so that is at your leisure when you get back.

I´ve started on the Virtual Cockpit. It´s hopefully going to have a textured instrument dashboard and if possible, textured sides too, which I plan to add via SCASM. I should be able to do it because we did one for the AT-9 Fledgling and the Zeppelin Staaken R.VI.

Then, with a decent .air file, a reasonable custom panel and the new custom gauges, together with the Virtual Cockpit, it should be a worthy CFS1 upload. We´ll see if it can be done well enough.
Cheers,
Aleatorylamp

[Ivan]

Hello Aleatorylamp, I actually had a chance to take a quick look at your FW 200 before I left. The exterior model looks pretty good The flight model seems to behave well enough in the air. It is way slow for acceleration on take-off as one might expect from so little engine power on such a large machine. (It barely reaches take-off speed on the short runway I have on the Pooh Island Test Airfield, but that seems right.) It is nicely ponderous as one would expect from such a large beast. One very noticeable issue is that the aeroplane is dropped into the simulator in a way that puts the tailwheel underground. That is why it has such a huge jump right after loading. From what I can tell it has only one main panel without any other sub panels. Are there any other engine controls such as throttle, magnetos or starter controls? Are there any fuel gauges? This is being posted from a Hotel Guest computer. - Ivan.

[aleatorylamp]

Hello Ivan,
Thanks for the reply from you hotel, and thanks for trying out the model before you left.

I thought I had already aligned the three wheels with their shadows on the ground on the new .air file with the engine corrections, but I´ve just checked, and when re-loading the plane into the sim, you´re right, the tail jumps! I´ll see to it, thanks!

With respect to the accelleration, I´ll try and find out what the take off run was in reality.
I wonder if it´s improvable without affecting behaviour during flight.
The specs quote the speed for raising the tail as 56 mph and take-off between 97 and 87 mph.

As regards the panel, it´s provisional and the only good thing about it is the new engine gauges, basically.
For the moment there are no sub-panels and as always, fitting other adequate 4-engined gauges is a problem, and that is still pending. For the moment fuel-related gauges are from the Fw190, the throttle ones from the Default Cessna FSFS Conv, and as the 4 ignition switches from the FS98 Condor are only replicas of the Default Cessna one I haven´t put them in.
So, I´m not really very sure about what to do.
Another thing is the pilot´s position or view point, which will have to be shifted sideways for the virtual cockpit, but then it won´t be coherent with the Cockpit Panel, so perhaps I will have to revert to the 2/3 Panel view.

Cheers,
Aleatorylamp

[aleatorylamp]

Hello Ivan,
I remembered that I´d altered the bitmaps on the Lear45 dual-thrust levers for the Baltimore and the Dornier. The FSFS Conv gauges for the 4-engined light jet are very similar, so I put rounded ivory-coloured handles on those, and duplicated the base. The result looks similar to the 4 levers in the Condor cockpit, although there are quite a lot more levers in there. I´d say it looks a bit better than the Cessna182 Throttles. Here´s a screenshot of the gauge to see what you think!
Searching for info on the take-off run, all I found was a comment about it not being good on short runways, but I´m still looking.
Cheers,
Aleatorylamp

[Ivan]

Hello Aleatorylamp,

We got back home this evening.
I wasn't commenting that the slow acceleration was wrong. I was just noting that it was slow as expected.
I found that one notch of flaps seemed about right to get off the short runway at Pooh Field.
Another thing worth looking for is the Propeller Pitch Range. If the low stop is too low, the acceleration tends to be higher than it should be.

I see from your earlier screenshot that there were actual throttles and a fuel gauge and they are not appearing on my version, so perhaps I need to see why that is the case.

During the trip, I came up with an idea for generating the Propeller Efficiency Tables but need to figure out whether or not I can do what I want within a spreadsheet. That would only be about 1/4 of the entire problem though.

- Ivan.

[aleatorylamp]

Hello Ivan,
I´m afraid it´s my fault about the throttle levers. I seem to get very confused with Cfg.Editor and Panel.cfg files it saves.

There was a 4-engined throttle quadrant I had completely forgotten about, with rounded-cubic ivory handles called "German.throttle.4.gau" in the FS98 Panel for the FW200A.

This gauge was still written into the panel.cfg I sent you with the aircraft .zip, but of course the gauge wasn´t included. It actualy looks better than the one I made yesterday, but I wanted to avoid using it because of copyright reasons.

The gauge itself is in the FW200A Panel .zip I´d e-mailed to you a while back to have a look at, related to the conversation we were having at the time with Smilo about German Gauges and Autopilots.

I have attached the gauge I made yesterday -"German.thrust_levers.4.gau" herewith, in case of interest.

With respect to the accelleration, the minimum prop pitch I have in the .air file of the Condor is 15, but as you said as well, with 1 notch of flaps it´s OK for take-off, and that also seems to be in the instructions for take-off. Probably it would be correct to leave it like it is then.

Cheers,
Aleatorylamp

[Ivan]

Hello Aleatorylamp.

Do you happen to know what the propeller pitch range really is on the FW 200?
It might vary with the engine installation.
I will download and add the new Throttles.
I will also need to create a set for my own twins.
The problem there is that the levers are different between the Mitchell and Lightning.
So far, it appears that the gauges for the Lightning will be easier to complete than those of the Mitchell,
but neither will be progressing at least for the time being as I chase down some things with the propeller tables.

- Ivan.

[aleatorylamp]

Hello Ivan,
I know it was a 1930 Hamilton Standard 2-position, 2-blade propeller, like on the Lockheed Vega, but I can´t find the two pitch-angle values. There was one for take-off to make the prop spin faster to take advantage of the revs, and then at a certain altitude, the second pitch was engaged to make the prop bite more air. This explanation seems to come from some advertisement for the prop.

Here´s a new screenshot of a proposed funtional, somewhat simplified distribution of gauges on the simplified Condor Panel I made based on a b/w photo. The Condor Panel.cfg file is also attached, and uses your new RPM and ATA instruments, my adapted Oil temp/press and EGT/CHT and 4-throttle gauges, and also the Autopilot Smilo sent, as it is very practical, and then all the rest is default and stock stuff.

It is just an idea, as the original 2-seat cockpit of the plane has duplicated instruments is quite complicated, and I don´t know what simmers would really prefer. Then, I still have a problem with the ignition switches. The stock one included is only for engine 1, and is really only for decoration, as pressing the "e" key is more effective.

I could have a try at helping you with the bitmaps for the throttle gauges for your Mitchell and Lightning gauges. I can´t guarantee anything, but if you like, you can send some pictures!

Cheers,
Aleatorylamp

[Ivan]

Hello Aleatorylamp,

I believe the Magneto Switches ARE necessary to have full control over the Engines.
Notice that in my gauge testing, I just about always do something with Engine #1 but not any of the others?
That is because I don't have the ability to control the others.

Another problem with using the 'E' key to start all the engines is that it automatically switches your fuel source to ALL tanks.
I believe Hubbabubba was running a test that had this effect when he was testing fuel switching a while back.
A set of Magneto Switches is on my list of things to do but I need to learn how to do a couple other gauges before I get there.

So, I take it that you do not have a reference for what the propeller pitch settings should be?
I still don't know how to use an adjustable pitch propeller, so I can't help you there.

- Ivan.

[aleatorylamp]

Hello Ivan,
Not to worry, Ivan, but thanks anyway for your concern about the prop! That´s why I wasn´t very worried about manually adjusted propellers and am very happy with CV ones. They work fine on the model with 15-65 degress, and it´s good enough for me, and, I don´t need prop pitch levers! In any case, just 2 manually adjusted prop pitch positions are not possible to put in, unless I´m completely mistaken... something which happens as often as not.

Re. Ignition switches. Interesting, your comments on how the "e" key does things. No hurry - one can´t have everything at once. A panel update later on can be done, so I wouldn´t be too concerned about that either.

What I am more worried about, is whether I should use 1) a full panel with the right side as radio/navigator´s position, or 2) a full panel with duplicated instruments for the co-pilot, or 3), a 2/3, off-centre view panel, as would correspond to the Virtual Cockpit that I´m working on at the moment to add using SCASM. Here´s a couple of screenshots of that too. The VC panel bitmap is not yet the definitive one.

Cheers,
Aleatorylamp

[Ivan]

Hello Aleatorylamp,

The Virtual Cockpit screenshots look good.
This is the kind of thing I was thinking about when I said that the Virtual Cockpit pieces do not need to appear anywhere else in the model and that other pieces of the model need not appear in the Virtual Cockpit.

Regarding Propeller Pitch:
Almost anything can be made to work with a pitch range of 15 - 65 degrees.
The question is whether or not you feel obligated to model the actual pitch range of the FW 200 propeller.
This is the same argument as with the 7 foot versus 9.7 foot propeller.
If you are just looking for performance and response, you use 7 feet as the diameter; If you are trying to use the actual numbers, you put in 9.7 feet and try to tune out all the resulting bad behaviour.

I can tell you that my Fokker E.III Eindecker has a "Whatever Works" kind of propeller.
I didn't know how to tune propellers at all back when it was released and didn't have the propeller pitch numbers anyway, so it got whatever propeller pitch worked.
By the way, that is not to say that I know what I am doing with propellers now. I just know a little more.

I am going to have to try out the two pitch and the controllable pitch propellers at some point.
Of course this will have to wait until I can figure out a few more things about constant speed propellers.

- Ivan.

[aleatorylamp]

Hello Ivan,
That´s what it´s like, isn´t it? One can do as much as one knows, and slowly one knows more...
We know what we know, and what we don´t, we try to imagine...

OK, I see your point on propeller pitch - it´s as good as the argument on the size.

I had kept on looking for some indication on the two pitch angles, finding quite a few pages on the Hamilton propellers, together with Harzell ones and others. Although in theory their engineers knew about constant velocity propellers, which they were striving for, it appears that technically it wasn´t possible to make one at first, so they came out with a simplified 2-position manually controlled one, with which they seem to have started revolutionizing the aircraft industry in 1930. Later they came out with a hidraulically, automatically controlled one, and then the CV one.

Strangely enough, I found not one single reference to the amplitude of neither the low take-off and climb angle, nor the high pitch angle for altitude, and there is no quote as to for what altitude either. This is rather logical though, as both would depend on the type of aircraft (speed) and engine horsepower, and all kinds of engine and aircraft sizes were catered for.

So I got an idea...
The logical conclusion was looking into what Mr. Beckwith (truthfully, what would we do without him?) would say about this in his test panel.

There, I had the feeling that a good take-off pitch would be between 17 and 19 degrees, as my Condor´s automatic futuristic CV prop has 15 set as minimum. Towards the end of the take-off run it´s at 18 and then it goes up to 25 for climb and higher speed low altitude flight.

Then with greater altitude, at speed, pitch progressively changes up to 28.7 at about 6000 ft and then goes down a bit to about 27.5 at the ceiling (19000 ft), and this gave me the feeling of a convenient setting of perhaps 27 degrees.

So, my two suggested settings would be 18 and 27 degrees.
This could perhaps be implemented using the manually controlled propeller option, and in the sim, using the manual pitch settings only at minimum and maximum, without the in-between positions. Low pitch would be valid upto 2000 or 3000 ft, and high pitch higher up, unless of course suddenly the pilot decided to slow down at altitude up to about 100 mph and then decide to do a power climb... there he would need low pitch for a while...

I also decided to snoop around in some Condors very nicely made for other simulators:
The FS2002 Condor, in the .air file, has min-pitch=18.5, and max-pitch=65. Then, in the Aircraft.cfg, beta min=9 and beta max=62. The FS2004 Condor has beta-min=1 and beta-max=60 in the Aircraft.cfg file. Not much help, except perhaps for the 18.5 degrees.

So I may not be very far out on my two 18 and 27 settings. I think I could try this out for a bit.

Thanks for your comments on the virtual cockpit - so I think it will work the way you say, adding the calls in the usual place for the VC, and putting the subroutines at the end of the listing.

Cheers,
Aleatorylamp

[aleatorylamp]

Hello Ivan,
I am trying out my 18-27 two-position "manual" propeller.
Record 500 Engine Piston Engine (FS98/CFS AI) is now:
Propeller Pitch Max Flat=27
Propeller Pitch Min Full=18

I don´t know what kind of effect these two have, but previously, there was 40 and 5 in here, and RPM was 25 RPM too low.
Now it´s at the correct 2050, but Hp is over by 7, at 727. However, getting Torque down to correct this has lowered RPM again, and now it´s at 2030, 5 more than my previous 2025 - a bit better. Nothing is perfect in this life!

In section 510 Propeller Parameters, I put in:
Prop Pitch Max=27
Prop Pitch Min=18
I then selected Option 3 (manual adjusment) for Propeller Type, and into the panel, I put the generic FSFS Conv 4-engine quadrant gauge, which includes propeller pitch adjustment.

I found that although the sim was now limited to 18 as minimum for take-off, it continues automatically selecting the best pitch availavble upto the maximum defined, unless the pitch lever is manually pulled down, which forces pitch to 27, reducing performance at low altitude, of course.
The question is, does Option 3 for manually adjusted propellers really work as would be expected?

In general, I suppose one could say that it is a bit more similar to the two-position manual propeller than it was before...
Now, S.L. performance is identical to what it was before, but at 6000 ft it´s 5 mph faster. I´ll see if I can adjust that.

Another strange effect is that RPM goes up with altitude. at 10000 ft it´s about 50 RPM over the desired 2050, and further up it goes down again, and it´s quite close to the correct 2050 again. Obviously, as it´s no longer a CV propeller, with Pitch being limited at 27, it makes the prop spin faster higher up, where previously pitch was 28.1.

All in all, I´d say it´s not too bad - it´s quite plausible.

Cheers,
Aleatorylamp

[Ivan]

Hello Aleatorylamp,

It sounds to me like you just did pretty much what I did for the Eindecker:
You examined what the CFS flight model was doing when allowed a wide propeller pitch range and then set your pitch limits to what you had found from observation.
Who knows? Your guess MIGHT be correct. I certainly don't know that it isn't.
How does it do with Throttle and RPM set for Cruising?

By the way, I think I commented on this last time you had issues reaching full RPM with a project:
Use <Control>F4 to set engine for maximum RPM. That is what I was doing and I had no problems getting to 2050 RPM even with your older propeller.
I did not test it with the new propeller tables because I didn't want to reconfigure your panel and you had already removed the test gauges.

Regarding increase in power with the extra 25 RPM, I do remember telling you that you should use whatever gearing it takes to get full RPM for engine tuning.
Consider it a Bench Test of the Engine before it is installed. You should not be getting surprised by extra power.
Besides, 7 HP is pretty much nothing. It is well within normal production variation, and of course our mechanics are experts and always manage to get a few extra HP.

Your RPM variation sounds like your Record 512 Power Coefficient Table is still not quite as good a match as it could be for this propeller / engine combination.
It MAY be realistic though. Perhaps the real aeroplane behaved this way. The rather narrow pitch range is another indication that the Power Coefficients are not matching up all that well.
To do the comparison between your aeroplane's and the stock Record 512s, I did a check at ONE altitude:
Engine power was determined for 500 Feet altitude at full power and maximum RPM.
I also have run into similar problems in the past but have no solution which is why I am trying to generate my own propeller tables.
Lots of programming to do there!

- Ivan.

[aleatorylamp]

Hello Ivan,
I hope you are enjoying the Easter week!

Thank you for your interesting post, and your indications. I´ll go by them to continue - they are very useful, as always!
In general it seems to to be working, and as you say, the irregularities it could possibly also account for possible real irregularities coming from the simple 2-position manual propeller at the time.

I haven´t had time to do more than just test maximum power and performance at a few altitudes, and have to do the complete set of tests first, including behaviour during cruise, to see what the picture is, and take it from there.

I´ll do the bench test again, as you suggest, and also perhaps with the Beckwith gauge try to pin-point the pitch angle/s at which I get inconsistencies, do the angle-formula calculation and see if I can adjust the corresponding point/s on the pitch-angle graph to improve the power coefficient. Using AAM, the visual graphs are visible and have a little more meaning.

Good luck with your programming! That makes me think... A little QBasic programme to generate a text file containing the list of angles for this might even be possible for me to try out, and then import the .txt file into the AAM graphs. Matching all the spaces and decimals in the lines... That could be fun, but success with this is quite different from fun!

Thanks a lot again, and I´ll keep you posted!
Cheers,
Aleatorylamp