Conspicuous by Their Absence

[hubbabubba]

Hello Hubbabubba,

I was thinking that a quick lesson in how to set up a V Cockpit using SCASM like what you sent to me back in 2006 would do Aleatorylamp quite a lot of good.

- Ivan.

I would have had to know the question before answering it. That's why I said that I would read the thread, the e-mails, and the PM to understand what you meant by "Virtual Cockpit". Was it the "no jittering" in virtual mode or the gauges in virtual mode, or something else, anyway...

Aleatorylamp; SCASM is an assembly language and need a GUI to work with, like Airport, EOD, etc... And the latest version available HERE is 2.96. To build (or rebuild) a/c, you will need Trevor de Stigter MDLDisAs that you can find HERE and a good TXT editor, this is the GUI I was talking about, but oriented toward aircraft (hence the MDL) than scenery.

You have to realize that pretty much all of my tools, and my e-mails, were lost when my W90SE machine went cold. And my own memory is barely better than that of my old rig.

BTW- You Riesenflugzeug look great, and would certainly benefit TG2 (Tail Gunner 2) for self-defense.

[aleatorylamp]

Hi Hubbabubba!

The thing is to prevent the Virtual Cockpit from disappearing in Padlocked Chase View in Quick Combat mode.
Yes, I have found SCASM 2.96 and also the correct Disassembler (Ivan told me which to get), and put both it in C:\SCASM.
I know the WinXP console window is rather a pain, but I managed to start SCASM and Moldenhauer´s comments came up, but it didn´t find the Zep-R6m.mdl model file (that´s the new Riesenflugzeig with the triple tail. fin), although it was in the same directory as SCASM. I must have been typing in sth. wrong all the time.

I didn´t know about the GUI, but tried Emerald Editor (Ex Crimson so-and-so) but that crashed the computer, so I put it in C:\, but it was no good anyway.
I´ll see if I can find a better GUI.
Edited update: I just found the editor on Trevor de Stigter´s site and got his disassempler too - maybe it´s better than one I found.

I´m glad you like the Riesenflugzeug!
I´ll look for TG2 - I suppose it´s a plug-in for CFS1.
Better than firing in all directions almost at random!
Edited Update: I´m afraid I´m on Windows XP and TG2 is only for Windows 98. Pity!

Incidentally, I found the Scenery Editor inside CFS1 - Very neat!

Thanks for your support!
Cheers,
Aleatorylamp

[aleatorylamp]

Hi Hubbabubba, Hi Ivan,

Update: OK, the Disassembler I got from Trevor´s site works fine and I´ve just made an .scx file, so it appears that something has started to work. Let´s see what happens now!

Ivan: In the disassembled Text file of the Giant that you SCASMed, I´ve identified the Virtual Cabin text portion that you sent separately. Supposedly this text has to be inserted into the new Giant´s disassembled file (in a convenient place, possibly the same place?) and re-assembled again.
If I should need to colour the green parts of the V-Cockpit in blue, I could disassemble the new .mdl file of the V-Cockpit and insert that portion.

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

[Ivan]

Hello Hubbabubba,

You're right. Your instructions were really to cure a "Jittery Cockpit". I expanded them to add in the Virtual Cockpit pieces and Canopy Frame, etc. Also added since then are adjusted animations though they are definitely not in my notes.

One funny thing is that the Jittery Cockpit doesn't appear in FS98 while the "Corrected" version wobbles all over the place.


Hello Aleatorylamp,

You can disassemble the models I sent you and see what kind of code I started with. The changes to your model were not terribly extensive, so they would not be hard to find.

- Ivan.

[aleatorylamp]

Hi Ivan, Hi Hubbabubba,

Once I get the set-up of SCASM and Disassembler running, which it doesn´t do yet, I´ll be able to start SCASMing. I may have to get the 12-year-old laptop I have here running on Windows 98 again for that.

Meanwhile, though, something perhaps equally important, if not more:
Ivan, I remember reading in one of your posts related to precision-building component parts (the P38 thread?), that even slight mal-adjustment of vertices (happens when working with low Zoom), increases the number of vertices in the component and causes excessive calculations which increase AF99 degree of complication.

The Giant is an upgrade on one of my earlier models (2003), when I still had trouble making wings. I never got round to cleaning up the vertices until I changed the wing-tips for the horn-balanced ailerons of the new Maybach-engined Giant a few days ago, so I took the opportunity to clean up both wings. This then coincided with your comment on the wheels, whose parts were also not perfectly aligned, so I cleaned those up too.

... and sure enough! Lo and behold! Instead of failing to compile at 142.8%, I was able to keep on adding parts, and now it´s still compiling at 148%! So then I got on to the first Giant as well, and cleaned that one too, and this allowed me to add the second dorsal machine gun (apart from the ventral one). The pair now faces outward at angles, so the structures are more part-consuming, but AF99 still happily compiles at 149.5%! ...I´m sure I´ll find something to put in the last 0.5%!

So, there´s much to be said in favour of cleaning up the construction!
Cheers,
Aleatorylamp

[Ivan]

Hello Aleatorylamp,

I have no idea where I may have mentioned the idea of mismatched vertices or polygons.

Here is why I made the comment that mismatches in the faces of a Component cause greater resource usage:
Take the example of a simple regular closed / solid cube.
We are all familiar with what that looks like.
It has 8 Vertices and 6 Sides. If this were a AF99 Component, it would use 6 "Parts".
Now lets take the SAME cube but take one face and move it outward very very slightly, say 0.01 foot.
We still have the 8 Vertices of the original cube but those now only account for 5 of the Sides.
The Sixth Side that was moved outward needs 4 more Vertices..... So....
The new misaligned cube needs 12 Vertices and 6 Sides.
AF99 still thinks the Component has 6 Parts.
The problem is that the actual code being generated now has to first define 12 Vertices instead of 8 even though it is still only drawing 6 Polygons.

This makes sense to do when you REALLY want a slight separation line, but is a waste of resources and unsightly if it is just a plain mistake. If the misaligned face were moved INward rather than outward, it would hardly be visible but would still would use more resources.

Hope that makes sense.
- Ivan.

[aleatorylamp]

Hi all!

After cleaning up the vertices it´s looking nice, and there weren´t any problems to add the central fin/rudder and horn-balanced ailerons for the Albatros built Staaken R.6 with Maybach engines. The colour scheme is a darker splinter lozenge, slightly different from the Schütte-Lanz built version with Mercedes engines. The analysis of the black and white photos of the time offers different interpretations, so there´s room for speculation.

The engine tuning is going very well, and the difference to the Mercedes Engines is noticeable. These had a slightly greater cylinder capacity 233.83 cu. in) and slightly higher compression (4.94/1) and were rated at 245 Hp at 8200 ft at 1400 RPM - a bit slower than the Mercedes engines lower down, but 20 Hp more powerful higher up, with an almost 2000 ft higher ceiling, and the speed difference was only about 3 knots (3.5 mph). The Maybach engines were the preferred ones, but were scarcer and more expensive...

So now there´s two planes, almost ready for upload...
Cheers,
Aleatorylamp

[Ivan]

Hello All,

I am still learning about these Tables myself, so I am presenting what is hopefully a thought provoking topic as I experiment with it. I am sure that some folks already know more than what I am just touching on here.

My original goal with the propeller tables was to cure a bit of a problem with the Japanese A6M Type Zero Carrier Fighter.
My original flight model had fairly decent behaviour but as I found more information, my corrections to incorporate the new Propeller Pitch limits caused a bit of problem.
Without knowing any better, the original low pitch angle was 20 degrees.
A very nice gentleman sent a manual to me that showed that the pitch range was really 29 degrees to 49 degrees.

As soon as I adjusted the minimum pitch to 29 degrees, the propeller started lugging badly.
The engine would not achieve maximum RPM until 185 MPH.
I was pretty sure this was incorrect because in numerous flight test reports, a lugging propeller was never mentioned in any of them.
As a contrast, a lugging propeller IS mentioned in flight tests of the Ki-61 Hien.

After all these discussions on propeller power coefficients, I decided to make an attempt at adjusting the minimum airspeed for maximum RPM.

In a way, I was successful. The propeller now comes off 29 degrees minimum pitch at 110-120 mph now and although I can adjust it a bit more, I will do some testing here to see how the performance and handling has changed.

*****

[Ivan]

As can be seen in my prior post, the Red Circle shows the area of greatest concern in affecting the low pitch power required.

One other thing worthy of note is the Advance Ratio range that is typical of the stock aeroplanes and the shapes of the graphs.

Now HERE is where things get really interesting.
One of the things I have often wondered about is why although propeller overspeed was often mentioned in the manuals, it never occurred in the simulator even at dive speeds exceeding Mach 1 (!) (Yeah, we can't get to Mach 1, but curing that is a different topic.)

It becomes obvious as you look at the shape of the graphs.
The propeller begins to drive the engine when the advance ratio exceeds where the blades are edge on to the air flow.
For a pitch of 45 degrees, Advance Ratio (J) needs to be 2.36 or higher.
For a pitch of 50 degrees, Advance Ratio (J) needs to be 2.8 or higher, but the graph only goes to J = 2.4.
The Type Zero Mark II fighter has a maximum pitch of 49 degrees which means that the graph does not cover the area in which the airflow would be driving the propeller and possibly causing an overspeed.

When I got here, it occurred to me to do a little more poking around.
The sample Record 512 I typically start with is from the stock P-51D.
Relevant Details about this Aeroplane are:
11 feet 2 inch Propeller Diameter
0.479:1 Reduction Gear Ratio
3000 RPM Maximum RPM

Typical Maximum speed is 437 MPH for the pokey D model and 441 MPH for the B/C models. They became even faster with later models such as the H.

Now, taking all these numbers together, we get a speed of 439 MPH at J=2.4!
What this means is that the propeller tables don't even cover the speed range of this aeroplane in LEVEL flight, much less in a dive.

Now if we look a bit further, we can see that the first row of Table 512 is specifying the Advance Ratios.
Perhaps it is worthwhile to adjust the ranges here. Since each column is specified, it would imply that the spacing does not need to remain linear either.
I suspect that the reason for such a low range of advance ratios is because all of the stock aircraft are just hot-rodded Cessna 172s which don't really go very fast.....

Thoughts?

- Ivan.

[Ivan]

Hello Aleatorylamp,

Your Giant project is the best test of what I was describing.
At the moment, you are stuck with 3 or 4 table entries to try to make a smooth curve for Table 512.
Perhaps it will be worth a test to reduce the range of Advance Ratios so that you have better control of the curve?

I know *I* will be trying something pretty similar shortly.

- Ivan.

[aleatorylamp]

Hi Ivan,
With the current problem of the Giant not slowing down for landing but gliding on in idle ad-infinitum at 150 ft and 50 Kt, I´m game for trying whatever will help! I´ve increased Zero Lift drag, Induced Drag and comensated Prop Efficiency, and slowly it´s getting a little better, although RoC is a bit high now.
Do you mean reducing the number of columns and perhaps trying out the 30 degree pitch column?
Cheers,
Aleatorylamp

[Ivan]

Hello Aleatorylamp,

Actually the total number of columns would remain the same, but the intervals might be closer.
As an example if the Advance Ratio were incremented by 0.1 between columns instead of 0.2, you would only go from
J=0.0
to
J=1.2

This seems to be quite sufficient for the Giant and similar machines: J=1.2 would mean a forward speed of around 275 MPH which the Giant and its brethren are not likely to reach, at least not in one piece.

I have just the opposite problem with WW2 Aircraft. The range of Advance Ratios needs to be increased, but the question is how much would be reasonable without losing the ability to fine tune the low end where it is more important. Also, in theory, a non-linear graph SHOULD work, but I am wondering how I would go about testing whether something is working or not.

At the moment, I am going back to basic Geometry and Trigonometry to figure out if I can generate a reasonable approximation of Table 512 using a spreadsheet.

One thing worth noting is the entry for 45 Degrees pitch at J=2.4. Simple Geometry states that the power coefficient should be Zero or slightly negative since the blade section would have zero angle of attack to the airstream at J=2.36.
Notice though that the P-51D graph does not do this. Then again, perhaps I do not understand this problem well enough because I have drastically simplified things.

- Ivan.

[Ivan]

Last night I did a bit of tuning to Table 512 for my Kawasaki Ki-61-Id.

The results are a bit interesting to say the least and I will need to do some more changes before this graph is useable.
First, I was able to adjust the propeller so that it now reaches full 2500 RPM below 150 MPH.
It is only 145 MPH which isn't much but then again, I only changed the values by 3-5% just for testing.
Idle speed is a bit higher 465 RPM instead of 450 RPM. I have no doubt I can drop a bit more with no great issues.

Unfortunately I could not resist "fixing" the curves that were so strange looking so now the general propeller pitch is quite a bit more coarse in normal flight.

The worst result though was to change the value for 45 degrees pitch at J=2.4.
The propeller now DEFINITELY overspeeds in a dive.
The problem is that it doesn't slow down much after pulling out of the dive.
The extra thrust from the overspeeding propeller keeps the aeroplane going quite fast for a LONG time.

Time to step back and review the results from the quick experiment. I was pretty sure that tuning by eyeball wasn't going to work well, but now that I have a smooth curve, I can adjust it very easily in Excel without any great effort.

There is quite a bit more in the plans, but they not worth mentioning here because they are quite indefinite at this point.
It is amazing the kinds of silly things we can make happen with these graphs.

- Ivan.

[aleatorylamp]

Hi Ivan,
Whoever would have thought that J settings could be altered in the first column of the 512 and 511 propeller tables!
So, sticking to the 25% Pitch column for the Giant´s 14 ft wooden prop, as far as I understand from your investigation results, instead of having the J settings going up by 0.2, one can regulate them more precisely within a desired operating range, having them go up by only 0.1 or even 0.5.
I inserted an extra line for J=0.35 becuase it seems to coincide with the top level speed at rated 4300 ft altitude: 80.5 mph (70 kt). Then, with the Vne being 93 mph, the J=0.04 (92 mph) value could perhaps be set at 0.0405.

Now the J setting distribution for the Giant´s speed range looks like this:
J=0.00... 0 mph
J=0.10... 23 mph
J=0.20... 46 mph
J=0.30... 69 mph
J=0.35... 80.5 mph
J=0.405.. 93 mph

Previously, both Zero Lift and Induced Drag were far too low, so I duplicated them and compensated the lower speeds by increasing the J=2.0 prop-efficiency setting from 0.45 to 0.75, obtaining better descent results and more or less maintaining preformance: Level flight stayed the same but RoC went up too much.
............Eff......Thrust
J=0.0.. 0.050.. 0.0135
J=0.2.. 0.750.. 0.0100
J=0.4.. 0.010.. 0.0086

Now, with the compensated prop efficiency for the increased Drag, I´m trying out the new propeller with more settings, efficiency and thrust values initially distributed as follows, and it generally seems to be working.
...... .......Eff.....Thrust
J=0.00.. 0.050... 0.0135
J=0.10.. 0.450... 0.0110
J=0.20.. 0.650... 0.0100
J=0.30.. 0.700... 0.0095
J=0.35.. 0.750... 0.0090
J=0.405. 0.010... 0.0086

This distribution will hopefully let me fine-tune things a bit more! Now I have to test it more meticulously. I´ll keep you posted.

OK, then,
Cheers,
Aleatorylamp

[Ivan]

Hello Aleatorylamp,

I am certain that other folks have figured this out long before now, but to me this is new.
Hopefully no one minds my posts and probable missteps as I explore this area for the first time.
The numbers you are posting for your Giant imply that nothing significant is being changed in the flight model other than giving the ability to fine tune the Propeller parameters. Obviously you figured out that the varying interval works as well.

I did one more test yesterday that also results in the same conclusion.

- Ivan.

[Ivan]

The results from looking at Tables 511 and 512 didn't seem logical.
I was wondering if perhaps the numbers we interpret to be Advance Ratio were actually 1/2 Advance Ratio or something else that would mean that these Tables were specifying settings at a much higher speed than it appeared.

The next step was how to set up a test that would "prove" that the value we interpret as advance ratio really was that AND to confirm that I had not calculated Advance Ratio incorrectly. (It is a very simple formula but who knows?)

As a test, I took a copy of my Kawasaki Ki-61-Id (the original version without the latest propeller modifications) and used AirEd to change all of the propeller efficiencies above J=1.0 to be Zero. The column for J=1.2 was also reset to be J=1.05.
So.... This fancy new propeller produces normal thrust at or below J=1.0. Its thrust drops rapidly to nothing as it hits J=1.05.

Ki-61-Id Relevant Information:
Propeller Diameter 9.84 feet
Reduction Gear 0.646:1 <----Inverse in the AIR File.
Maximum RPM 2500

From this, Advance Ratio J=1.0 corresponds to 180.64 MPH and J=1.05 would be very close to 190 MPH.
The test showed pretty much normal behaviour until a maximum speed of 187 MPH was reached at which point the aeroplane would go no faster. Increasing the drag by lowering the landing gear reduced speed to 186 MPH.

I also found that my interpretation of zero thrust when the blades were at AoA = 0 to the relative air flow was incorrect.
I did my calculation based on 0.75 Radius because that is typically where the blade angle is determined. We know it can be no more than 100% of the Radius though, so the limit is certainly no more than 33% higher than my earlier calculation.... Unless we take into account about 1-3 degrees difference to the angle of zero lift because of a cambered blade.... I am making a lot of assumptions and guesses here, so perhaps someone knowledgeable should step in?

*****

[Ivan]

Here again are the Tables 511 and 512 for the stock P-51D Mustang.
Also attached is a Propeller Efficiency Graph calculated using Vortex Theory.

For this exploration, I will use a Propeller Pitch Angle of 25 degrees because it is within the operating range of the P-51D.
Note that the Vortex Theory Graph shows that Efficiency drops to Zero at just below J=1.3.
This is happening because the relative air flow to the Propeller means that at any forward speed above J=1.3, the AoA of the blade is negative.

Next, note that Table 512 shows that the power absorbed by the propeller drops to zero at slightly above J=1.2.
So far, so good. Things here are more or less consistent.

Now HERE is the fun part: Note that in Table 511, the Propeller Efficiency at 25 degrees is still over 0.7 at J=1.2....
BUT, Above J=1.2 or J=1.3, the power being absorbed by the propeller is NEGATIVE. I interpret this to mean that the airflow is making the propeller spin faster which makes sense from a geometry standpoint.

So if I am interpreting things correctly, what we have here is an odd little perpetual motion machine. The airflow drives the propeller. The propeller gives thrust which increases the forward speed and advance ratio which drives the propeller even more. The only thing preventing the world from melting down at this point is that typically the maximum pitch is much higher than 25 degrees and the constant speed governor keeps raising the pitch. That would explain the serious overspeeding I was getting in the Ki-61 flight test.

Next step to check whether my interpretations are correct is to either setup a propeller with a very low maximum pitch or manually reduce the pitch if it is possible in CFS.
Does anyone know what happens if we specify a propeller as Adjustable Pitch rather than Constant Speed?

- Ivan.

Next

[aleatorylamp]

Hi Ivan,
Very interesting indeed, your findings!
If I understand correctly then, on a constant velocity propeller, in a dive, the governor reaches the maximum high-speed setting after which prop-overspeed occurs. On an adjustable pitch propeller, I wonder if by manually changing the angle to a less feathered position, one could actually use the engine as a brake in a dive, or would this over-rev the engine?

In the case of the Giant, with the new Drag values that have improved descent, the new J distribution has indeed allowed for finer control over different speeds, and similarly to the "zero" value in one of your trials, a very low value at the aircraft´s top speed also helps curb power there.
Cheers,
Aleatorylamp

[Ivan]

Hello Aleatorylamp,

What you are describing is what is actually SUPPOSED to happen.
The Constant Speed Unit regulates the Engine RPM and adjusts it to the RPM set by the pilot.
It does this by making the pitch more coarse (higher degrees pitch) if the RPMs are too high and makes the pitch more fine (lower degrees pitch) if the RPMs are too low.

At some point, you hit the mechanical limits that limit the range of pitch settings on the propeller.
The P-51D has quite a wide pitch range at 23 degrees Minimum to 65 degrees Maximum.

The reason for this exploration to begin with was that I was finding that the propellers on a couple of my aeroplane projects were unable to maintain RPM at lower airspeeds (Advance Ratios). I already knew I needed to adjust the Propeller Power Coefficient (Table 512) which fortuitously coincided with your development of the Giant with is very slow 14 foot propeller.
After that diversion, I thought it reasonable to experiment a bit with the A6M3 and Ki-61.
A6M3 Propeller Pitch is 29-49 degrees.
Ki-61 Propeller Pitch is 27-47 degrees.

After that first pass, I was finding some strange results which got me to looking at Propeller Efficiency in Table 511.
This was definitely NOT what I expected to find.

So, back to your original comment:
Yes, what is supposed to happen is that the propeller either hits mechanical limits or manual control that prevents the pitch from becoming coarse enough to match the speed at which point the airflow DRIVES the propeller faster and causes an overspeed condition which acts very much like an air brake.
What REALLY happens in the simulator is that the propeller is driven by the airflow, but instead of acting like an air brake, it converts that driving force into extra horsepower and thrust which accelerates the aircraft even more.

From a conceptual standpoint what we are seeing is something like a perpetual motion machine:
Imagine a child who sees a pinwheel standing up with its handle propped in a soda bottle.
She wants to see it spin, so she goes up, takes a deep breath and blows on it.......
Imagine her surprise when the pinwheel starts to spin and then pulls itself and the bottle off the table toward her.
After narrowly missing her, it rotates even faster, gains speed and accelerates across the room, out the window and achieves orbital velocity....

- Ivan.

[Ivan]

Last night I decided to test whether I was correct in my understanding of how the numbers in Table 511 and Table 512 interacted by conducting a simple speed run at 500 feet.

The first test was with a stock P-51D AIR file:
Without WEP
Pitch - 39 degrees
Power - 1376 HP
RPM - 3000
Speed - 334 MPH

With WEP
Pitch - 41 degrees
Power - 1557 HP
RPM - 3000
Speed - 352 MPH

That seems a touch slow (I was expecting about 365 MPH) but still quite reasonable.

This test was then repeated with the Propeller Maximum Pitch angle set to 26 degrees in Record 500 and Record 510.
Nothing else was changed.

Without WEP
Pitch - 26 degrees
Power - 2458 HP
RPM - 5360
Speed - 388 MPH

With WEP
Pitch - 26 degrees
Power - 2935 HP
RPM - 5654
Speed - 408 MPH

The engine output and speed were highly unstable and depending on HOW the equilibrium condition was reached.
These results were from accelerating to these speeds in level flight. If a higher speed was reached as in a dive, the speed and power were noticeably higher though the exact numbers were not easily repeatable:

Without WEP
Pitch - 26 degrees
Power - 2500 HP
RPM - 5500
Speed - 394 MPH

Hmmm.... Now what?

- Ivan.

[aleatorylamp]

Hi Ivan,

Some things work all the time,
All things work sometimes,
But it seem impossible to get
All things to work all the time!!

Possibly the programmers discovered the virtual perpetumobile in the simulator and had to put the brakes on the numbers somehow to stop the stampede!

At the moment I´ve discovered that although the climbing behaviour is coherent with the critical altitude setting and the propeller and torque settings on the Giant, level flight peak horsepower is a bit off - it happens 400 ft below, i.e., although level flight is correct at 267 hp for the specified altitude of 4300 ft, and drops off normally thereafter, 400 ft below that (3850 ft), it is surprisingly at 273 hp! - it should be a little below 267.

I´d never noticed it, as I´d never tested level flight there, only rate of climb. RPM´s are of course at maximum 1450 in both cases. I´ve tried regulating Boost Gain, but that affects performance higher up, and the ugly-too-soon-peak stays! I´ve tried all sorts of things in different places, but to no avail. Any ideas? I wonder...

There is always something that won´t always work as expected.
Cheers,
Aleatorylamp

[aleatorylamp]

Hi Ivan,
Given that we are working with a 16-year-old simulator, I suppose one really can´t complain about some things needing work-arounds.

Your question " Hmmm.... Now what?" I suppose was merely rhetoric.
In any case I´d say the over-revving propeller in a dive is quite a feat, and a neat reality effect!
It´s also quite interesting to see how the simulator actually treats the issue - it seems like a simplification that has been patched up.
Anyway, in order to curb the child´s pinwheel achieving orbital velocity.. ha ha! ... could RPM then not be limited with the friction curve - not too unreal either - or by a zero thrust in the table position above a certain speed? But I´m sure you are already trying that out... Good luck!

In the case of the small quirk sets in full power in the Giant´s engines 400 ft below rated altitude, only noticeable in level flight and not in a climb anyway, I would wager it´s nothing to worry about. It may be another simplification, like a "step" that occurs at 3850 ft, similar to another "inverse" one just after 500 ft where power drops a bit and then rises again. Perhaps the "steps" are altitude divisions with which the simulator manages the effect of altitude on power. I might investigate a bit to see if there´s more of these.

OK, the fun must go on!
Cheers,
Aleatorylamp

[Ivan]

First of all, Regarding the Giant....
You already know enough to tune this beast because it is now pretty much where we originally started.
If your maximum power is achieved at too low an altitude (even 400 feet too low), just increase the boost a tiny bit.
I would strongly suggest you try out the original boost setting I used on the first 14 foot propeller I sent to you.

After you get your peak power at the right altitude, you can tune it down a bit with the Friction / Engine Efficiency.
Once you get that, then if necessary, you adjust the Propeller Power Coefficient to get it to lug a bit to reduce power lower and higher than the 4300 feet critical altitude.
To reset your speed, Use Propeller Efficiency....

Same cycle one more time....

- Ivan.

[aleatorylamp]

Hi Ivan,
Thanks for the summary of instructions, especially the order in which to undertake the steps.
It will also help to correct the Maybach-engined Giant with the new boost setting for 8200 ft after I´m done with the original one I´m correcting now - Incidentally, I´m still using the original 1.18 Boost setting from the first 14ft prop for the 4300 ft rated altitude.
OK, thanks a lot!
Cheers,
Aleatorylamp

[Ivan]

Actually, as we were discussing in email, the Simulator is pretty good for the time.
The stock AIR files however are not so good and this is just one more example to prove my point.
Notice though that I have been tuning AIR files literally for years and have not found this issue until now.
Then again, I didn't really understand the tables or examine them in detail until now either.

So.... As goofy as these Propeller Tables are, they are part of the AIR file for every aeroplane project I have ever released.
THAT fact is the "Now What?"

I am still trying to figure out how to go about building my own tables. Doing them by hand isn't hard, but tuning them afterward is annoying. I want a spreadsheet that will let me do most of the calculations I need for the fine tuning.
I believe that instead of a 0.2 step in Advance Ratio which gets to J=2.2 in the Efficiency Graph and J=2.4 in the Power Coefficient Graph, I should use a 0.25 step. That would put the limits at J=2.75 for Efficiency and J=3.0 for Power Coefficient. That would put the TAS at 500 MPH and 546 MPH which still doesn't cover the entire possible speed range but should be good enough to handle most dives.....

I don't have a definite plan yet and won't until I do a bit more experimenting. Perhaps I will even end up with a non linear graph.

- Ivan.