Focke Wulf Fw200-A Condor

[smilo]

"The inconvenience of typing instead of speaking is made quite a lot worse when preparing a post here on the thread. Not because it times-out quite soon - one already expects that, but because there is some obnoxious, unnerving accidental key-stroke combination that throws you out of the text editor into some other page, and of course you lose whatever you have been typing.

This trap involves some mistaken keystroke in the lower left keyboard corner.
I have the feeling it is the left CTRL key accidentally hit by the little finger plus some other key.
After losing a longish text twice running one tends to give up.
Does anyone know how to switch the stupid combination of left CTRL + other key off ???
It doesn´t happen on the Notepad..."

well. this is interesting.
first, i was unable to use the reply with quote feature.
which confirms Ivan's complaint.
so, i've copy/pasted Stephan's quote,
wrapped it in quotes and made it blue.

second, i have experienced aleatorylamp's issue
on more occasions than i care to mention.
it is particularly annoying, after writing
one of my typically long winded posts.

i would very much like to know the cause,
so i can avoid it in the future.

don't quote me on this, but, as i recall,
after one such occurrence,
i clicked the back arrow,
which took me to a blank comment window.
aggravated, i sat there looking at the blank slate
when, all of a sudden, the yellow auto save
popped up in the lower right corner.
on a whim, i clicked it and low and behold,
there was my unfinished post.
of course, it hasn't happened again,
so, i can't verify.
BUT, the question arises,
how does one retrieve an auto saved post?

 

[Ivan]

well. this is interesting.
first, i was unable to use the reply with quote feature.
which confirms Ivan's complaint.

Hello Smilo,

I know how to edit the codes to display a quoted message, but I do find it interesting that the feature works intermittently here but seems to work pretty well on the other SOH forums.


Hello Aleatorylamp,

I have read through your post about 5 times (maybe more) now and I really have no idea what you are trying to tell me except for your last line.
The only message I am getting is that you don't know how to get rid of the Perpetual Motion Roller Coaster that I thought you liked so much.
Please go back and read Post #70 again.
If you search for Propeller Efficiency Graph on the Internet, it will give you an idea of what the proper shape of such a graph should be.
From my calculations using pretty simple geometry:
For 25 degrees the efficiency should be zero at J=1.1 and above.
Assuming Aerodynamic twist on the propeller blade of 5 degrees, efficiency should be zero at J=1.4 and above.
That just reduces the window because your Power Coefficient Table for 25 degrees does not really match those results because it becomes zero at J=0.8.
Basic rule is that Propeller Efficiency should be always be zero (or less) whenever the Power Coefficient is zero or negative.

- Ivan.

 

[aleatorylamp]

Hello Smilo,
Thanks for your comment! So it´s not only me! Or my computer itself...
Sometimes when a post gets longish and I remember to safeguard myself just in case, I save it to the notepad, and if it disappears, I can retrieve it with the paste option.
Cheers,
Aleatorylamp

 

[aleatorylamp]

Hello Ivan,
I ´m very sorry I wasn´t able to express myself clearly - I was just trying to explain what I understood as the correct effects of negative pitch on a real plane.

Never mind, with what you have explained now, I know what to look for and how to correct the faults.
Not that I don´t like the Roller Coaster / Perpetumobile effect... It´s just that I thought it wouldn´t be good on the plane...
Here´s me trying to be diplomatic!

As I was only testing Max Speeds and Cruise,I hadn´t actually experienced the effect yet, but from your description it definitely sounded like a lot of fun. I was actually about to try and make it happen - at the ceiling like you mentioned at the beginning - when I saw your post.

Thanks for the information on when exactly things should be zero (or less).
I had no idea, so it´s going to be very useful. Thanks very much indeed!

So that´s how one can tell! Good, good! - both things should be zero or less at the same point on both tables.
Very good!
Cheers,
Aleatorylamp

 

[Ivan]

Hello Aleatorylamp,

I don't believe the system is capable of actually handling negative pitch on a propeller at all.
Be VERY VERY careful though. I am explain things as I understand them. I may not be correct all the time or for that matter even most of the time.
Correct it if you wish. It obviously doesn't have much of an effect anyway if no one noticed it on any of the stock AIR files.
Just be careful, There were other side effects I noticed when I tried it out.
I believe the other effects are from the interpolation because there are not graphs for EVERY angle and values in between are interpolated from graphs that may be pretty far off.
You are almost certainly going to get some performance differences.
I had a few the last time I tried to work on the Ki 61 Propeller Tables which is why I decided I needed to build my own versions.
....so, in theory, what I told you is correct (at least I believe that it is).

- Ivan.

 

[aleatorylamp]

Hello Ivan,
Hmmmm, interesting! From your posts about the two Condor graph tables, I had interpreted that they were fixable, but OK, one thing is the theory and another, what happens in practice with the sim.

I have stopped interfering with the graphs on table 512 other than just turning the 11 graphs into 2. Any other changes upwards or downwards caused losses in performance. Maybe one pixel on the graph meant too large a change in the numbers, I don´t know, but as AAM does offer mousable manipulation of graph points, I suppose this is not too wild a manouever!

Adjustments done this way to the Efficiency Table 511, on the other hand, proved to be very beneficial! Of course, I well remember and take into account your recommendation of using this table for adjustments, rather than the other.

I haven´t had time for a couple of days to do any specific testing to try and make the zero values coincide between the two tables, which I wanted to try, just for curiosity´s sake.

Of course, as you say, there will be changes in performance, which will probably be quite confusing. To use only the Efficiency table for this exercise is bound to cause changes, and then trying to compensate these with adjustments to the Coefficient table, will probably just make things even worse. The more I think about it, the less I want to try it out...

What I did notice during a cruise the ceiling (sounds like what flies do sometimes...) is that a small reduction in power brought on a slight increase in speed and also in thrust - this could be caused by the interpolations and/or small inconsistencies between my present graph tables.

Well, so now I can decide again what I want to do about it! "Wer hat die Wahl, hat die Qual" - the agony of choice!

If I try, I´ll post the result!!
Cheers,
Aleatorylamp

 

[Ivan]

Hahahahaha!

Hello Aleatorylamp,

I was about to do more explaining of my rather quick post last night but you seem to have found everything that I was about to cover.

Thanks for the information on when exactly things should be zero (or less).
I had no idea, so it´s going to be very useful. Thanks very much indeed!

So that´s how one can tell! Good, good! - both things should be zero or less at the same point on both tables.
Very good!

Not necessarily True. One Relationship must be True from a Physics standpoint, but the other does not.
Imaging a Propeller that has ZERO propulsion no matter what the angle and you will see what I mean.

What I did notice during a cruise the ceiling (sounds like what flies do sometimes...) is that a small reduction in power brought on a slight increase in speed and also in thrust - this could be caused by the interpolations and/or small inconsistencies between my present graph tables.

Maybe and maybe not. You did not give enough information to come to any conclusion as to why this is happening.
WHAT ELSE changed when you reduced power????
What I noticed about the interpolation effects was the lack of linearity, but although it wasn't linear, it was at least monotonic and your description does not sound like that is the case here.

There are a lot of relationships that are the combined interaction of several parameters that I can't easily imagine which is why I believe I need to build a few more tools to be able to understand what is really going on. I also assume that things will be nice smooth curves and the reality may not be that way, especially with discrete points as represented in the simulator rather than a continuous curve.

-------

Last night I did a lot more programming.
The result does not behave properly yet but at least all the pieces are created.
What I also realised when I was done coding was that for the time being, AirEd will pretty much do what my neat nifty program was intended to do but just in a slightly less graceful manner.

The problem here is that I am impatient and want to see how my other ideas work in adjusting the Propeller of the Ki 61, so perhaps I will be taking a break from programming and just using what I already have for a little while.

- Ivan.

 

[aleatorylamp]

Hello Ivan,
OK, thanks - I´ll check and see what else changes when I reduce power.

Re. negative pitch values and the tables:
OK on the horizontal zero line and where the different J factors reach it on a conventional prop efficiency graph.

I hadn´t related our recent exchange on the shapes of real propeller efficiency graph and the sim´s graph shapes, to the negative pitch issue and its connection to the perpetumobile roaler coaster.

Incidentally, newer sims don´t seem to be doing any better as regards negative pitch, and opinions in other forums relate it to possibly unfinished work by Microsoft on the Tables, saying that even the low speed theory would have been unnecessary had it been done properly from the beginning.

Anyway, as we had commented, the downward slope on the left of the efficiency graphs is different, and I would agree with you that the sim is most probably unable to handle the more realistic shape, so I will not experiment with this for the moment - it´s too complicated to do properly.

The shapes of the sim´s thrust coefficient graphs seem to be a bit more realistic though, but as I said before, altering them usefully is outside the scope of my abilities.

You mention a 25 deg pitch graph which would cross the zero line at 1.1 J, but, a supposed 2-position manual propeller wouldn´t have one. Also, a 20 deg. pitch graph would be above zero at 1 J, but this position wouldn´t be there either.

There is only a first take-off (and beginning of initial climb) position, which I found worked as best at 18 deg, and a second high-speed position of 35 deg, as efficient as possible for cruising, which would also allow for a more or less good climbing capacity. (On current tests, I find RoC is only about 1/2 as good as it should be, so I may have to lower high pitch from 35 to 32 or even 30).

After take-off on the real aircraft, there would be a moment when the low pitch would become very inefficient, invading negative pitch for sure, and the high pitch position would be set in, which for a short time would expectedly be rather under-efficient until the aircraft got faster.

Now, limiting the sim to 18-35 min-max pitch does not stop it from using the intermediate pitch position graphs 20, 25 and 30 deg, so I scrapped them and made the equivalent of an 18 deg graph and copied it over the 15, 20 and 25 deg ones, and then, copied the 35 deg. one over the 30 deg one.

So now there are only 2 graphs to be used, 18 and 35 deg, which however, still doesn´t stop the sim from interpolating between the 18 and the 35 graph, using values that don´t exist on a 2-position propeller. Obviously, when it wants to use the 25 deg pitch graph, it finds the 18 deg one, and will encounter negative values - just like in real life, but the question is, what does the sim do with negative values? Opinions in forums about newer sims also express doubt.

Thus, this whole 2-position experiment is of limited use, but perhaps not totally useless, and I still think it works better than using the CV propeller.

Anyway, let´s have a good Sunday!
Cheers,
Aleatorylamp

 

[Ivan]

Hello Aleatorylamp,

We just got back from Dinner after a day out shopping.

As I stated last time, I am having a lot of trouble understanding you because I believe you are not being consistent in terminology.
First of all, there are two tables that are of concern here:
Table 511, Propeller Efficiency
Table 512, Propeller Power Coefficient which I sometimes shorten to just "Power Coefficient".

Each table has Advance Ratio (J) as its X coordinate and Propeller Pitch (15, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65 Degrees) as its Y coordinate.
Note that Propeller PITCH ranges from minimum of 15 Degrees to maximum 65 Degrees. There is NO NEGATIVE Propeller Pitch represented.

Incidentally, newer sims don´t seem to be doing any better as regards negative pitch, and opinions in other forums relate it to possibly unfinished work by Microsoft on the Tables, saying that even the low speed theory would have been unnecessary had it been done properly from the beginning.

As stated before, there is no NEGATIVE PITCH. If you mean the Negative Power Coefficients in Table 512, They may be off in dimensions, but the general shape is correct. Regarding Low Speed Theory, There is no way that this method works all the way down to Zero Forward Speed. Dividing by Zero simply does not work. You can bring the Low Speed Limit down arbitrarily low, but you still need it at some point and if that point is very very low, the Efficiency Graphs (Table 511) need to be adjusted accordingly.
They ALREADY ARE adjusted to some extent because there is in reality NEVER a Non-Zero Efficiency at Zero Forward Speed and that is the case for the several lower pitch graphs (Table 511).

In any case, it really doesn't matter for the most part because if I remember right, Low Speed Theory limit is actually specified in the AIR file and is really pretty low at around 45 MPH or so. (No, I don't remember the actual number right this moment.)

Anyway, as we had commented, the downward slope on the left of the efficiency graphs is different, and I would agree with you that the sim is most probably unable to handle the more realistic shape, so I will not experiment with this for the moment - it´s too complicated to do properly.

For the most part, the Downward Slope on the LEFT side of the Efficiency Graphs (Table 511) are correctly shaped though they may not fit your particular Propeller's characteristics.
The RIGHT side of each Efficiency Graph is the incorrect part.
Correcting it isn't that difficult but it isn't quite as simple as matching what geometry would tell you because if you do, there will be some not so nice interpolation effects because there are only graphs for 11 Pitch Angles from 15 Degrees to 65 Degrees and not 51 which would make it a much closer approximation to continuous curves.

There is only a first take-off (and beginning of initial climb) position, which I found worked as best at 18 deg, and a second high-speed position of 35 deg, as efficient as possible for cruising, which would also allow for a more or less good climbing capacity. (On current tests, I find RoC is only about 1/2 as good as it should be, so I may have to lower high pitch from 35 to 32 or even 30).

I find it highly unlikely that a Cruise Pitch setting would make for any kind of reasonable Climb Performance. I believe it is much more likely that the Take-Off / Low Pitch setting would be the one used for Climb.
If your research can't find any information on the FW 200, you might want to try to find another aeroplane with a two pitch propeller and see how they were set.
If you can't find any of this information at all, you might want to work backwards from what you know must be true.
Find the Engine Power and RPM at Cruising Speed and observe what the Propeller Pitch, Efficiency and Thrust are and set your High Pitch values to that.....

So now there are only 2 graphs to be used, 18 and 35 deg, which however, still doesn´t stop the sim from interpolating between the 18 and the 35 graph, using values that don´t exist on a 2-position propeller. Obviously, when it wants to use the 25 deg pitch graph, it finds the 18 deg one, and will encounter negative values - just like in real life, but the question is, what does the sim do with negative values? Opinions in forums about newer sims also express doubt.

IF you are describing what you did to Table 511 - Propeller Efficiency, you are MUCH MUCH worse now than if you had not done this.
I don't know enough yet to figure out how to go about doing it to Table 512 - Propeller Power Coefficient but have a few ideas of which none really look all that good.
In the Efficiency Graphs (Table 511), if you only have the graphs for 18 Degrees and 35 Degrees and the simulator wants to use 25 Degrees, it will still do so.
The problem is that it will INTERPOLATE what the numbers should be from what it has in Graph 18 and Graph 35 and because they are now 17 degrees between the two graphs instead of 5 degrees, the interpolated values will be much worse of an approximation.
Even with graphs only 5 degrees apart, the interpolation gets pretty bad at times as I mentioned before.

Also as I implied, the interpolation gets bad enough that at times one probably should stray a bit from physical reality as to not have really bad places in the graph where the interpolation produces even more silly results.

Have a Pleasant Sunday also.

- Ivan.

 

[aleatorylamp]

Hello Ivan,
I´m terribly sorry, this is getting too bad to continue, and is unfair on your patience. It´s getting ridiculous.

Yes, you are right, I confused terminology. Again, I´m sorry about the confusion, which only makes everything worse.
I know there are two tables... and yes, I meant the negative values on the graphs, that the sim appears not to be able to handle, not negative pitch values, which don´t exist there.

Then also, even worse, I confused left and right: I meant the right side of the Efficiency Graph slope, not the left one.
Maybe it´s because I´m left handed that I confuse the terminology of left and right.

It isn´t possible to have a 2-position, manual propeller because the sim won´t allow it.
It looks like the CV prop works better, and for that matter, even a fixed one works better, because I´ve tried it! But, the plane had neither of these.

Even FS98 would be better with its generic propeller Records 503 and 504, but as it has no supercharger, keeping the .air file from FS98 will be no good either.

To avoid any more of this absurdity, I will not pursue this matter any further.

So much for this agonical experiment. At least I´ve learnt what not to do, and with that I don´t only mean making a 2-position manual propeller, but rather delving too far into something I am by far not sufficiently familiar with, and where I am completely out of my depth.

Thanks again for your patience, and again, I do apologize for all the confusion.
Cheers,
Aleatorylamp

 

[Ivan]

Hello Aleatorylamp,

Yes, this discussion is getting a bit repetitive and a lot of it is because you are relying on me as the authority on the subject and I am definitely not qualified. The utilities I am programming are not smart; they are just intended to allow me to experiment faster to try to understand how things work.

Another part of the problem is that we all tend to rely on M$ stock files as a guide for how to do things and many times their methods are not the best. That is not to say that there is anything wrong with the basic framework of the simulator and AIR files, but I am still trying

... and yes, I meant the negative values on the graphs, that the sim appears not to be able to handle, not negative pitch values, which don´t exist there.

Not sure what you mean here.
Negative Efficiency does not appear to work, but Negative Power Coefficients work the way they should.

It isn´t possible to have a 2-position, manual propeller because the sim won´t allow it.
It looks like the CV prop works better, and for that matter, even a fixed one works better, because I´ve tried it! But, the plane had neither of these.

Even FS98 would be better with its generic propeller Records 503 and 504, but as it has no supercharger, keeping the .air file from FS98 will be no good either.

I am not sure if it is possible to have a two pitch manual propeller in CFS. I haven't tried to work on one yet.
A lot of times, things are possible but not in the manner that one would expect. There MIGHT be a less intuitive approach.

Regarding no Superchargers in Flight Simulator 98, I know I have said that, but I also know that is not really a correct statement.
A better statement would be that FS98 does not properly handle Superchargers.
Note that the Manifold Pressure limit in Token Variables for FS98 Gauges allow up to 65 inches Hg.
If there were no Superchargers at all, the limit should be around 30 inches Hg.
The big problem is that with or without a Supercharger, the Critical Altitude is ALWAYS Sea Level.

It also helps to read about aerodynamic theory because many times, the equations you see there will be recognizable in various places in the simulator.
Maybe things will make more sense as you understand more about how the pieces of the AIR File fit together.
I know I am learning more as I experiment more.

- Ivan.

 

[aleatorylamp]

Hello Ivan,
Thanks for your comments!
Well... all this isn´t exactly easy to understand in detail, and a general understanding of how it works is not enough. There is also a saturation point that facilitates making mistakes when posting messages about it.

I downloaded a little programme called "MS Aximer Aerospace Engineering and Design Software" (it´s for Windows XP), made by an aerospace engineering student, that covers a number of related aspects. Perhaps it will help, but I have my doubts.

I don´t fancy using the FS98 .air file, because it is too limited. Even if it appeared to work, it would be worse than an "as-good-as-possible CFS approximation", which is what looks like the best idea to go for in the case for my wished 2-pitch-position prop.

All it needs is minimum and maximum pitch, and to let the sim do the rest. As it interpolates anyway, a division point between low and high seems irrelevant, as it seems to decide by itself what it wants at all times.

My mistake was to interfere with the 2 graph tables, so I´ll simplify my life and leave those completely alone, as of the point where we adjusted the imported Hurricane efficiency graph.

I still haven´t found any pitch data specs for this aircraft or any similar engine/prop, but 18 seems fine for low, and before throwing in the towel, it would probably only need a little further experimentation to find the best value for high.

As you suggested: >>Find the Engine Power and RPM at Cruising Speed and observe what the Propeller Pitch, Efficiency and Thrust are and set your High Pitch values to that.....<<

So, I won´t throw in the towel quite yet.
Thanks a lot, and Cheers,
Aleatorylamp

 

[Ivan]

Hello Aleatorylamp,

I just got back from a walk with my Son around the neighbourhood and thought of an idea that might prove interesting but need some time to get familiar with the values in the Power Coefficient Table before I even think of tackling a Two Pitch Propeller, but in theory it MIGHT work.

.....

That was a couple hours ago.
We had some dinner guests and I did not have a chance to finish up the post before they left and the cleanup after dinner.

There is no mistake in "Interfering" with the two Propeller Tables; That is how things are done.
In my opinion, the mistake was in not really understanding what the Tables were doing before altering them.

I should have also qualified my recommendation to: Make sure you do this with Propeller Tables that you believe are behaving fairly well.
The "Behaves Fairly Well" is a difficult thing to describe. I can give you numbers but that would be an uneducated guess because I still don't have a feel for how the FW 200 should behave.
Perhaps I will give this aeroplane a try when I have finally gotten some results with my Ki 61.
For the Ki 61, I am actually going back to results I have from my own testing from 2008 and much of the details need to be confirmed.

- Ivan.

 

[aleatorylamp]

Hello Ivan,
We had some friends over for lunch after our trip to the farmer´s market, and my wife tried out a new recipe for pieces of turkey fried in batter with a curry-based oriental mix of spices. Very nice! ...and a salad with lettuce of different types and colours!

Re. the propeller: I realize it´s of course no mistake to change graphs if one knows what one´s doing... my mistake was to do it without knowing enough.

So, backtracking to a previous OK point, I´ll try to get the Condor .air file to "Behave Fairly Well". With the in-between graphs intact, climb should now not suffer as it did with them cut out. Climb is now in the low pitch region, as you commented - at around 19, not 25 as I was getting. Also, I´ll keep to the CV setting, as manual seems not to work as expected.

Later, I´ll see what else can be done - there´s no hurry anyway!

Thanks for your support!
Cheers,
Aleatorylamp

 

[aleatorylamp]

Hello Ivan,
The .air file is at the "Behaves fairly Well" point. In fact, I´d say it "Behaves Very Well"!
It is the .air file that had the Hurricane´s slightly corrected Efficiency Table 511, and the 15-65 Pitch CV Propeller, now adjusted to 18-35 Pitch.

> Take-off behaviour is correct, as before, and any low-pitch-limit increase will be less convenient.
> High pitch limit is fine, as the maximum needed at the tested heights was 34.9, and performance is the same as it was before.
> All Maximum Speeds and Criuse Speeds are correct, as is the rate of climb, which I hadn´t tested before, managing very well with the specified 1260 fpm initial climb, which is first at pitch 19, and later goes up to 24-25.

The results look fine and I am very pleased with the performance at present.
The aircraft could even by uploaded with this .air file!

Nevertheles, there is no hurry at all - I still have to finish the Virtual Cockpit. So, should there be an opportunity in the future for wiser experimentation with Efficiency and Power Coefficient Tables than what I was doing last week (Eeek!!), we can do so whenever it is convenient.

Cheers,
Aleatorylamp

 

[Ivan]

Hello Aleatorylamp,

I have been taking a closer look at the Ki 61-I-Tei AIR File and I appear to have left quite a lot of broken things from a couple years ago.
When I started with it last night, it was on Version 0.58 which according to my notes is specifically for tuning Tables 511, and 512.
It also would not accelerate past 45 MPH..... Thus No Take-Off and no confirmation of Engine Power at 500 Feet Altitude.
I replaced my earlier work with the original stock P51D Tables and the behaviour is not bad but hits full 2500 RPM at 160 MPH instead of 120 MPH so basically it is a matter of starting all over again.

Are you SURE you want my help on this subject???

- Ivan.

 

[aleatorylamp]

Hello Ivan,
A good question! Perhaps it won´t really be necessary or worth the trouble to do any more work on the propellers tables of the Fw200-A. After your initial help suggesting the use of Hurricane Table 511, and tuning that slightly, the performance problems I was getting with the new 9.7 ft propellers disappeared.

Then, fitting manual Hamilton Standard type propellers can for the moment only be done by limiting Pitch Range to an educated guess as to what angles may have been used, and of course making sure that aircraft performance fits the specified flight envelope. It does so very well, and I am inclined towards leaving it as is. The manual propeller option available in the sim, simply seems not to work for 2 manually adjusted, low and high, pitch positions.

Now, there is still the minor maximum RPM issue, which is still 34 RPM low, but given the difficulty in tuning Table 512 for this, I´d prefer to leave it alone.

Table 512 is indeed a difficult kettle of fish, isn´t it? Good luck with the Tables on your Ki-61-I-Tei !
The advantage of going back to square one after such a long time, and using a clean slate, is that knowledge acquired in the meantime may be easier to apply than fitting into something that´s already half done.
I hope it goes well!

Cheers,
Aleatorylamp

 

[Ivan]

Hello Aleatorylamp,

I'll make a pretty safe bet that the Propeller issues with the FW 200 really haven't disappeared yet.
I believe that with your current testing protocol (and mine as well) that we just don't see them under those particular conditions.
Even the stock aeroplanes have a few problems like this.
Minuteman and Hubbabubba documented the conditions a few years back with their testing though I don't believe they went into the details as to why it was happening. Then again, some REAL aeroplanes are not all that well behaved either.

Then, fitting manual Hamilton Standard type propellers can for the moment only be done by limiting Pitch Range to an educated guess as to what angles may have been used, and of course making sure that aircraft performance fits the specified flight envelope. It does so very well, and I am inclined towards leaving it as is. The manual propeller option available in the sim, simply seems not to work for 2 manually adjusted, low and high, pitch positions.

In reality, these are not very educated guesses as I have pointed out repeatedly. They are just what works experimentally with the Propeller Tables we have easily available. The reason why I keep emphasizing this point is that we have to remember what data is REAL and what is a conclusion from questionable methodology. That is also why I keep reminding you that I do not actually know what I am doing with AIR Files either. I just know how to adjust them to get the results I want.

Now, there is still the minor maximum RPM issue, which is still 34 RPM low, but given the difficulty in tuning Table 512 for this, I´d prefer to leave it alone.

As you have probably noticed, I don't seem to run into the same problem as you do and I do not believe it is a difference in computers.
Try hitting <Control>F4 to select Maximum RPM and see if it works for you. You might have to do it periodically at low altitudes where the air is dense.

As I might have mentioned in its thread, the model for the Ki 61-I was pretty much completed back in 2005 with only a minor edit for wing gun muzzles a few years later. I should also post a little bit of history about the real aeroplane at some point but not in this thread.

- Ivan.

 

[aleatorylamp]

Hello Ivan,
Hmmmm... The flight envelope that I am using as a reference, relies on some data coming from the original documentation of the second Fw200-A prototype, which is not very extense, so I have extrapolated other necessary data from later early variants, for which more extense data is available: The Fw200-A0 (reduced production run with very slightly more powerful engines), and the Fw200-B1/B2 (early military transport versions, slightly heavier and with further slightly more powerful engines).

The resulting total information on the performance of the Fw200A coincides very well with that of the model.

Also to be taken into account is that there is a lot of generalized, contradictory and inaccurate information attributed to the Fw200A that really comes from the Fw200-C1/2/3/4 models, much more powerful and heavily loaded military variants.
All this misleading information must be filtered out!

If you were to be interested in the details of the different variants, I will be happy to post them.
I haven´t done so yet for fear of being even more boring!

My educated guess as regards the two propeller pitches is rather more like a logical deduction that works with the sim, the details of which I know are:
1) Low pitch was used for take-off,
2) the take-off run was 420 meters, and lift-off was at 87 mph,
3) flaps had to be set in take-off position (there were only 3 positions: retracted, take-off and landing),
4) very soon high pitch was set in when the plane had gained some speed and a little height.
5) The Hamilton Standard type propeller´s low pitch was used to maximize take-off power
6) Initial RoC was 1260 fpm

From this information and from the Beckwith gauge stack, low pitch can´t have been very far off 18 degrees, and the high setting of 35 seems to work quite well. Of course, the sim is interpolating all the other graphs in-between as well and performance is very good. All specified maximum and cruise speeds coincide with the model, and the estimated cruise speeds also do.

Without more precise data as to what the real propeller pitches were, there is not much to correct. I don´t see what can be done to improve things, and I also don´t know where improvements would be needed for the moment.

If there is a less questionable methodology available, from which useful conclusions can be obtained, I would be happy to use it.

I always check Maximum Engine Power to be at 100% with the Beckwith Gauge, and my joystick is regulated so that a right button opens full throttle and a left button shuts it. The difference in maximum RPM happens on my AMD tower, on the new AMD laptop and on an old Pentium 4 Tower, but apparently not on your machines, but it doesn´t really worry me.

If you have any suggestions as to how I could do things better, I´d be glad to hear them.
Cheers,
Aleatorylamp

 

[Ivan]

Hello Aleatorylamp,

Glad you are happy with the current AIR File for your FW 200.
There has been more work and thought put into this one than most others out there.
Just be careful about declaring something as impossible when all we can really state is that WE don't know how to do the thing in question.

From this information and from the Beckwith gauge stack, low pitch can´t have been very far off 18 degrees, and the high setting of 35 seems to work quite well. Of course, the sim is interpolating all the other graphs in-between as well and performance is very good. All specified maximum and cruise speeds coincide with the model, and the estimated cruise speeds also do.

This is all based on Propeller Tables which are a questionable match. That is why I do not have much faith in the conclusion.
I chose the Hurricane Mk.I Power Coefficient Table because it was the closest match based one ONE number.......
It is like choosing the most qualified accountant based on her shoe size. Who knows? This selection method can't ALWAYS be wrong.
You are probably correct in saying that without any more information, there is nothing else that can be done.

If I come up with something regarding the Two-Pitch Propeller, I will let you know.
I have an idea brewing but it will need a fair amount of testing with your existing AIR file to see how to do things and I don't want to go there until I finish with the Ki 61 Propeller.
I am finding that there are not enough columns for Advance Ratio to do what I believe should be done and that there are plenty of quirks in the stock P51D Propeller Tables.
My goal at the moment is to put this AIR File into a releasable state and go back at some later date to experiment more and do some more fine tuning.

I always check Maximum Engine Power to be at 100% with the Beckwith Gauge, and my joystick is regulated so that a right button opens full throttle and a left button shuts it. The difference in maximum RPM happens on my AMD tower, on the new AMD laptop and on an old Pentium 4 Tower, but apparently not on your machines, but it doesn´t really worry me.

It happens on my machines too. That is why I use the <Control>F4 sequence to select maximum RPM.
Often this has to be done repeatedly to keep the engine speed at it maximum.
I have done a considerable amount of reading this evening on wind turbines to try to understand what happens when the airstream is driving the propeller. It does make for some very interesting reading and puts a lot of other bits of "commonly accepted wisdom" into perspective.

- Ivan.