Focke Wulf Fw200-A Condor - Page 7
Page 7 of 9 FirstFirst 123456789 LastLast
Results 151 to 175 of 202

Thread: Focke Wulf Fw200-A Condor

  1. #151
    Hello Ivan,
    Thanks for your post - Iīve been following your Ki-61 thread, but havenīt posted much because I donīt know enough to be able to comment anything.

    You had called the aircraft you set your Ki-61 up against, "the stock Griffon-powered Spitfire". I presume this was because the 1800+ Hp at altitude would be far in excess for a Merlin-powered version, as it claims to be.

    Thanks for your offer for looking at the Condor .air file. Iīll send it to you right away!

    I still havenīt finished the Virtual Cockpit. Iīm actually having a bit of trouble with a front tooth, antibiotics, painkillers and resulting migraines, until the dentist can kill hopefully the nerve next Monday. Itīs all fleas for an old dog, like they say in Spanish.

    I would still have to SCASM the separately built and textured VCockpit with co-pilot, and put in all the corresponding lines in the Condor .scx file.

    A simple alternative which worked on the P-3 Orion would be a simplified AF99 internal view. The Condor parts count is only at 143.4%, so it might be allowed if it still compiles, and would only involve the view-point correction with SCASM. Of course it wouldnīt be as nice as the otherway!

    I will send you the aircraft in a moment, with some explanatory comments as regards your performance question.

    Cheers,
    Aleatorylamp
    "Why make it simple if you can also make it complicated?"

  2. #152

    Rate Of Climb specs

    Hello Ivan,
    The specification lists I sent with the model for testing a possible 2-position manual propeller, were mainly maximum speeds, as Cruise speeds are given without Boost pressure reference, so they will pose no problem, and are stated as generally being between 0.7 and 0.8 ATA.

    However, there WAS a important piece of information lacking:
    Initial Rate of Climb, which is specified for this aircraft at 7 m/sec, i.e. 1378 fpm.

    Other possible useful reference data I also have are the climbing times:
    0 to 1000 meters - 2.6 min.
    0 to 2000 meters, - 5.9 min.
    0 to 3000 meters, - 10.1 min
    0 to 4000 meters, - 15.5 min.
    This does not mean I expect you to test all this, because I can do that as soon as you tell me!

    Restly Performance specs (Fw200-A Condor, with 4 x 720 Hp BMW 132-G1 engines:

    Ceiling: 19028 ft (because of the non-pressurized passenger cabin).
    Max. Speeds:
    226.8 mph at S.L. (Full 1.2 ATA Boost pressure maintained up to 1800 m, i.e. 5900 ft)
    240-245 mph at 5900-9800 ft
    243 mph at 8500 ft
    Cruise:
    208 mph at 3280 ft.
    217 mph at 12467 ft.
    Eco cruise:
    197 mph, n.a. altitude.

    The information should be more complete now!

    P.S. On a general note, the airfile using the 9.7 ft diameter, 18-35 degree pitch, CV propeller is working very well along the whole performance curve, I think, including RoC. This is probably because our beloved CFS1 single-speed supercharger is doing its job!
    As regards performance, I wouldnīt know where to change anything. Basically it is just a matter of converting the propeller into a manual 2-pitch position one and getting the same performance. I hope this will not make things more difficult!

    Thanks again, and cheers,
    Aleatorylamp
    "Why make it simple if you can also make it complicated?"

  3. #153
    Hello Aleatorylamp,

    I can guarantee you that the performance will be not as good with a two-pitch propeller.
    I just did some more thinking about the first idea for a two-pitch propeller and while I am sure I can get the pitch to switch in a manner that resembles a real two-pitch propeller, it will tend to lug at low speeds at low pitch.
    To some extent that can be addressed a bit by messing around with the torque curve as I did for the Ki 61, but it will be much more radical and the RPM will be inappropriately low for a while before the switch.

    By the way, the data in your notes is good enough I actually can do quite a lot of calculation without actually doing any testing on the game computer.

    Tonight I will work on the second idea I had because the first one is obviously not looking as promising right now.
    This stuff really belongs in a separate Propeller thread, but just as obvious is the fact that I am really just experimenting rather than trying out known techniques so there will be no real theme or message to such a thread yet (at least not for two pitch propellers).

    - Ivan.

    P.S.
    "Why make it simple if you can also make it complicated?"

    Because when it gets too complicated, even the author gets confused.

  4. #154
    Hello Ivan,

    Model performance is a bit too good as regards RoC, I must admit, certainly due to the CFS1 CV propeller the Fw200-A Condor Prototypes didnīt have.

    The short production run of 6 units after the Prototypes, didnīt have CV props either, although they did have slightly more powerful 800 or 830 Hp engines. But then, they were heavier, so overall performance was very similar. It was with the military versions that the 3-bladed, geared CV props were implemented, and that improved performance considerably.

    The model at the moment has the speeds specified for the 720 Hp prototypes, but with the accelleration and RoC of the better propellers!

    The lower performance that you are describing with the lugging on take-off and the initially low RPM at the pitch-switch-point shortly after take-off, is exactly what I was expecting. If you can manage that, it would certainly be wonderful!

    Another piece of information I found, and that I mentioned a while back, is that this plane had a 420-meter take-off run on asphalt, with flaps at take-off position. Flaps only had 3 positions - retracted, take-off and landing positions.

    As this 2-pitch propeller sub-subject pertains to the Condor, it is not totally out of place here, and is probably not substantial enough for an own thread.

    I was thinking I could later follow Smiloīs suggestion of building the Lockheed A10 Electra - come Ventura - come Harpoon, for which this propeller will also come in handy!

    So, I hope you enjoy the experiment! Let me know if I can cooperate in any way meanwhile.
    Cheers,
    Aleatorylamp
    "Why make it simple if you can also make it complicated?"

  5. #155
    Hello Aleatorylamp,

    Enjoy the experiment? Maybe. Maybe not. We shall see.
    It is basically testing whether my ideas will actually work as I expect without unanticipated issues as I ran into for the first idea.

    I have been plugging in data from your notes and ran into a small issue:
    You seem to give several different cruise settings; Are they at 1930 RPM?

    What was the typical cruising parameters on a long flight?
    Back in those days, I would expect them to cruise at pretty low altitude to avoid needing cabin pressure equipment.
    I am guessing that it would be 8,000 to 10,000 feet.

    You gave the best rate of climb, but what True Air Speed and Altitude was that achieved at?

    - Ivan.

  6. #156
    Hello Ivan,
    Specifications for the 720 hp powered Condor states continuous cruise at 550 Hp and 1930 RPM,
    but I havenīt been able to achieve that with the sim. If you can do so, that would be fantastic!

    Continuous cruising speed is given by one source at 335 kph at 1000 meters, (not at S.L.), and Eco-Cruise at 320 kph.
    High speed cruise is stated at 365 kph at 3000 meters - which is also maximum speed at S.L.

    Update: This I think is a bit high, because other sources state that 335 kph is high speed cruise, normal cruise is at 320 kph and Eco-Cruise is at 300 kph. (208, 199 and 186 mph).
    In conclusion, I think that the faster scale mentioned above, refers to the units in the Fw200-A0 pre-production run, that had slightly more powerful engines with 800 or 830 Hp. Propellers were of the same type though - it was only with later militarized versions that 3-bladed CV props were used.

    As regards RoC, best rate of climb given was initial RoC.
    Steepest angle is at 165-175 kph, and best Speed and RoC is at 220-230 kph. The record-breaking Prototype versions had the best rate of climb of all Fw200 versions, because they were lighter, despite their slightly weaker engines. Cruise speeds were also the best.
    Maximum speeds with the more powerful engined versions went up to about 405 kph. Mitary versions of this type came to be the Fw200-B1 and B2 versions.

    Typical long-range flights were done at about 9000 ft.

    Update: Later, with the Fw200-C militarized versions, despite another huge power increase with 1000 Hp and 1200 Bramo Fafnir 323 and 323P engines, max. speeds, and all performances, because weight was increased tremendously, started going down again. This was an example of a stop-gap wartime measure, and it is said that the Condor filled more than one gap. What is clear though, is that as an airliner, the Condor had an impeccable design, that would have developed into a production run perfectly if it hadnīt been interfered with by the war.

    Anyway, Iīm still searching to see if I can find anything else that is useful. It is very confusing because of the two or three different engines used on two or three different initial versions, which leads to generalizatioins and contradictions by different sources.

    For the moment, I hope this helps!
    Cheers,
    Aleatorylamp
    Last edited by aleatorylamp; May 20th, 2017 at 07:52.
    "Why make it simple if you can also make it complicated?"

  7. #157
    Hello Aleatorylamp,

    For the moment, I don't think I actually need any more data.
    I was looking for HP - RPM data. The speeds are not useful for the method I am trying to implement.
    It will be one goofy looking graph if it works.
    Actually it will be goofy looking whether it work or not!

    Hopefully I will have a chance to start working on edits to the propeller records soon.
    Helping my Daughter with her Physics Project takes first priority.

    - Ivan.

  8. #158
    Hello Ivan,
    Yes indeed, I agree with what takes first priority! Thereīs no hurry for the propellers. Good luck for your daughterīs project!

    Iīm glad you have enough data to work on for the Condor Propeller. I was still looking around for extra details, but itīs just more of the same. Enough is enough!

    Iīm still working on the Virtual Cockpit. Itīs impossible to add more than 2 individual parts before Af99 stops compiling, so my plan of a simplified interior view like on the P3 Orion with just the SCASMed viewpoint correction is not possible.
    So, Iīll continue with my first plan and try to add the VCockpit completely via SCASM.

    Cheers,
    Aleatorylamp
    "Why make it simple if you can also make it complicated?"

  9. #159

    Condor Virtual Cockpit

    Hello Ivan,
    I added a Virtual Cockpit for the Condor with SCASM. It was much less complicated than I had feared.
    I just looked at the ones you had shown me how to do, and then jumped in at the deep end. After one or two tries with a few error reports I got it right!

    Itīs complete with canopy spars, floor, textured cabin walls, dashboard, and cabin-back with curtain, and then thereīs also the co-pilot in his seat who turns his head when you move the rudder.

    Hereīs a screenshot!
    Cheers,
    Aleatorylamp
    Attached Thumbnails Attached Thumbnails vc.jpg  
    "Why make it simple if you can also make it complicated?"

  10. #160
    Hello Folks,
    The next step in logical thought now, is trying to achieve a transparent cockpit for this aircraft. However, it is rather difficult or even impossible without sacrificing all the moving surfaces, which here, do seem to have come out quite cleanly, only habing a minimum of bleeds.

    The nose and the forward cabin at the moment are two components which include forward and aft canopy spars, with insignia-tagged grey-textured windows added.

    Making the windows transparent was no problem, but in order to get a stepped surface under the spars and transparent canopy, without bleeding through different parts of the cabin walls, modifications in the cabin/nose build were needed.

    More components were not readily unavailable, so I took the 4 propeller components, leaving blades now separately included in the build. The price was that the Aircraft Animator Prop-Disks now bleed through different parts of the engine cowl sides... This in itself is of debatable acceptability.

    The cabin now got an extra cabin-component under the pilotīs place, and a middle canopy component above. The transparency itself looked quite cool, and 2 textured crew heads could be added via SCASM (the Virtual cockpit is resolved with SCASM, comprising 129 extra textured parts), but there is a problem: Despite bleedless under-cabin walls, the canopy bleeds through the aft cabin wall under ther antenna, so this is the second case of debatable acceptability.

    In conclusion, it was not very good, so the airplane is best with textured cabin windows and SCASMed interior cockpit view, as it is now.

    Cheers,
    Aleatorylamp
    "Why make it simple if you can also make it complicated?"

  11. #161

    Propellers and Such

    Hello Aleatorylamp,

    I am surprised that converting the Propeller Components to single blade caused those kinds of problems.
    I do that all the time on my own projects.
    The animation gets more difficult, The shading becomes different, and a few more Parts get used, but otherwise there has not been a difference.

    A set of Two Pitch Propellers installed in the Condor is being shipped to you.
    Note that there are a few side effects from the changes.
    Some can be addressed via changes in the Torque Curve of your Engines.
    I had to do something very similar for my Ki 61 for 2400 RPM versus 2500 RPM operation.
    RPM is obviously much harder to control now.
    Let me know if you like the changes as a whole.

    When you look at the graphs, you will see that the concept is very simple, but to get there took a lot of calculations.

    - Ivan.

  12. #162
    Hello Ivan,
    Thank you very much for the shipment! My mechanics have been mounting the propellers and taken the machine for a preliminary test flight.
    It is very, very interesting indeed, what you have achieved, and
    everyone is completely amazed!

    The Efficiency Table looks more realistic, by the way, and the Thrust Coefficient table is totally mind boggling, and I suppose that that is precisely where the secret lies.


    Anyway, the first trials: At first I was waiting to discover where or when 18 deg. low pitch would change to 35 deg. high pitch, as I had expected this to happen automatically, but it stayed there even at almost 197 mph, and also, the plane didnīt get any faster, although I was already at 1000 ft.

    So, I slewed up to 5000 ft and there it was at 35! I went down to 300 ft again and it was still at 35, and it was then I discovered the manual change would do it.
    I repeated the test with 18 deg. upto 197 mph and then gave 35 degrees, and it continued speeding up, this time to 215 mph. Of course, minor adjustments in Drag will put speed up to 226.8 mph. Hp is at 718, so a very small adjustment will get it to 720 Hp.

    Although here I have some misgivings, because I saw on hand-pencilled graph for the performance of the BMW 132 engines, the real power curve for 1.2 ATA for 720 Hp went from about 685 Hp at S.L. to 760 Hp at 3280 ft... so I might even leave the torque graph as it is now, if it turns out to be more exact!

    At 6000 ft speed went up to 235 mph, and I saw that pitch would stay stay at 35 deg. even though I changed the setting. So, obviously there must be a point where it changes by itself. Then I noticed it changes with RPM, and pulling back the throttle to slow down the engine, pitch drops to 18.

    Anyway, I am still trying to decypher how exactly it works, but it does seem to be completely realistic. I still have to discover where if it changes automatically from 18 to 35, or if this is to be done manually only.

    Itīs absolutely great!
    Cheers,
    Aleatorylamp
    "Why make it simple if you can also make it complicated?"

  13. #163
    Hello Aleatorylamp,

    I am glad your mechanics are having fun. My mechanics had lots of fun also but really don't know much about the Condor or even Propellers for that matter. One fellow had an idea how this could work and convinced the others to follow along for a while. If nothing else, it would have been a learning experience.

    My suggestion regarding under speeding and over speeding is to use the torque graph to adjust things until they look right.
    The under speed is about 100-150 RPM too slow, but with the right torque graph adjustments, the power loss will be minimal though it should still be higher at 2050 RPM.
    The over speed seems to be around 100 RPM at worst and that can be adjusted by using the torque graph as a rev limiter. Imagine if the torque is 100% at 2050 RPM but drops to 50% at 2075 RPM....
    There are of course other ways, but I suggest you do not mess with the Friction graph.

    Note that in places where the aeroplane is now going faster, it is mostly because RPM and Engine Power are higher.
    Also, if the speed gets stuck at 197 MPH at low level, you can probably adjust the efficiency on the 15 Degree graph to push it past the hump. If you tell me where this is happening:
    Altitude,
    Speed,
    Power,
    RPM,
    then I can do it for you. My guess is that this is happening very low at Sea Level to 500 feet.

    By the way, how do you manually adjust propeller pitch??? I actually never tried that.

    Working on your propeller got my technicians thinking about what was wrong with the propeller on the Ki 61 and that aeroplane will get another edit soon.

    - Ivan.

  14. #164
    Hello Ivan,
    This is getting more interesting every time.

    Pitch can be forced into high by manually moving down the blue propeller pitch levers on the thrust quadrant, despite the CV-prop entry of 2 in record 330 "Propeller Type".

    I thought the speed limitation at for low pitch was intentional, to make the pilot manually move pitch into high, but of course, if this is altitude-dependant, it canīt be intentional! Itīs curious anyway, and can be left that way.

    Hereīs a little performance table for this.
    I havenīt adjusted Torque or Drag to get correct specified performance yet.
    I was looking for exactly where pitch went from low to high.
    Of course, it not olnly depends on altitude, but also on speed.

    18 Pitch:
    _500 ft, 689 Hp, 1951 RPM, 194.5 mph, 1858 torque, 714 Thrust.
    1000 ft, 708 hp, 1985 RPM, 197.4 mph, 1879 torque, 725 thrust.
    1500 ft, 724 hp, 2003 RPM, 199.6 mph, 1899 torque, 733 thrust.
    2000 ft, 733 Hp, 2022 RPM, 201.4 mph, 1904 torque, 737 thrust.

    Note: Any millimetrical misalignment on even only one of the blue propeller pitch levers (this often happens on start-up if full power is given too soon), will facilitate the automatic change to 35 pitch if it can get above about 204 mph when at 2000 ft.

    2000 ft, 736 Hp, 2026 RPM, 208.0 mph, 1906 torque, 899 thrust.

    Even at 2800 ft, pitch will stay at 18 pitch, unless a certain speed is surpassed, but it is difficult to establish when.
    At first I thought it was also about 204 mph, but later during another test the change already occurred below 200 mph.


    At any rate, now I will try and adjust power and speeds as you suggested before doing any other tests.
    Cheers,
    Aleatorylamp
    "Why make it simple if you can also make it complicated?"

  15. #165
    Hello Aleatorylamp,

    Last night, I was a bit bored, so I did a little testing with the FW 200.
    You are right, it does get "Stuck" at about 197 MPH or so at the 500 feet altitude where I was testing.
    On my test panel, I did not think of bringing up the engine controls panel, so I just used <Control>F2 to drop the RPM a bit and was able to switch to 34 degrees pitch.
    To me, this seems to be pretty reasonable behaviour.

    My problem here was that I did not have a way of telling where I had the RPMs set for (didn't think of the propeller control lever), so when I increased RPM to get closer to full power, it would drop the pitch back down to 18 degrees again.
    (By the way, I suspect that the actual low pitch setting was a bit higher than 18 degrees.)

    So far, I see that all your testing is done at low level.
    I can tell you that for some reason, the Power Coefficient (Engine Power) is quite low below about 3000 feet.
    Do some testing higher up and you may find a difference in behaviour.
    I was figuring that for that era, the cruising altitude was 8,000 feet to about 10,000 feet (Probably closer to 8,000 feet) the pilots would want to get the aeroplane up higher to cruise faster in the less dense air but also have enough air not to need oxygen for crew or passengers.

    Your table is interesting and would be useful data for a checklist, but I suspect you do not really have a feel for what is really happening here. (I know I didn't when I started messing with these tables and even now I find things that should be obvious if I really had a good feel for how things worked.)

    The actual values as you can tell from the Table 512 labels are Cp and J.

    The values you mentioned are all included in Cp and J:
    Speed affects Advance Ratio
    RPM affect Advance Ratio AND Power Coefficient
    Horsepower affects Power Coefficient
    Altitude affects Power Coefficient (but it also affects Engine Power.......)

    Both are pretty easily defined, but the combination is not necessarily intuitive (at least not for me).
    My suggestion is to build a spreadsheet for calculating these values and alter the inputs to see how Cp and J change.
    You may be quite surprised by some of the effects of changing a single variable.

    As I mentioned earlier, a couple ideas occurred to me while I was working on the FW 200 propellers and I need to think about how they affect the propeller tables I generated for the Ki 61.

    - Ivan.

  16. #166
    Hello Ivan,
    Thank for your post. I still have to study it more closely, as well as your previous one.

    I only had enough time to do the main testing at S.L. and critical altitude (5900 ft).
    S.L. because it would be the basis for the rest, and Critical altitude because I was getting a power surge there, which I wanted to reduce without losing too much S.L. performance.

    My initial trials increasing torque from 0.4995 to 0.51, 0.505 and 0.500, and reducing drag from 57 to 54 and eventually 52, gave an excessive power surge at 5900 ft. First, 836 Hp, then 815 Hp and 807 Hp, and I eventually managed to reduce that to 792 Hp by just going the the opposite way with the Torque graph, leaving it at 0.490.

    This has the result that at 300 ft, with 18 pitch it goes to 195.3 mph with 657 Hp and 1923 RPM. Then, pulling the prop pitch levers to get 35 pitch, it goes up to 222.2 mph with 701 Hp and 2206 RPM.
    Then, at 5900 ft critical altitude, Iīm getting 244.5 mph with 791 Hp and 2208 RPM.

    Thatīs the current position with the testing Iīve been able to do, and Iīm looking through my documents to try and decide if this is OK.

    The pencilled BMW 132 Graph table related to the BMW-132 L and H 800 and 830 Hp engines, is the only reference point I have, and Iīm trying to imagine if the older 720 Hp BMW 132-G could have a 720 Hp line starting at S.L. and giving 791 Hp at 1800 meters altitude.

    Note that for the engine on the pencilled graph, RPM for 720 Hp is 2250, and not 2050.
    The older engine had 6:1 compression ratio, and these had 6.5:1. Presumably, with the lower compression, the 720 Hp max. power would have been a 5-minute affair, not a 30 minute thing by any means. Continuous power was 550 Hp though.
    The newer engine on the graph has this at S.L. and going up to 625 Hp higher up.

    Have to rush!

    Update:
    The graph must refer to the 132-Dc, that gave 850 Hp. At first I though of the 132-H1, but that one went up to 1000 Hp for 1 minute. Then, it could not have been the 132-L or -H, because those only went up to 800 and 830 Hp, not 850.
    The -Dc gave 790 Hp for Take-off and 780 Hp at 9000 ft, and I donīt know about 1-minute power foir the -DC.

    I was looking more closely at the graph, and the comment about the 720 Hp being a 30-minute thing, could confirm this.
    The -H1 delivered 1000 Hp for 1 minute, and 800 Hp for 5 minutes. The Dc and H1 engines had a 0.62:1 reduction gear, hence a 3-bladed CV propeller, so it is hardly a good comparison for the 720 Hp engine. Also, the critical altitude was higher, between 7000 and 9000 ft, depending on throttle setting, and the supercharger supplied a maximum of 1.38 ATA. This engine seems to have had a "Vollgashöhe" i.e. a maximum throttle altitude as of 1100 meters, not below.

    The 132-L engine was the one that was most similar to the engine Iīm using, but the pencilled graph does not refer to it.
    It gave 800 Hp for 1 minute and 720 Hp for 5 min at 2150 RPM, had almost the same supercharger, no reduction gear and a 2-pitch-position, manual propeller.This engine also seems to have had a "Vollgashöhe", an altitude of 1400 meters, below which maximum throttle was not allowed.

    What is clear, is that there is quite some confusion as regards Fw200 engines!!
    So it is going to be even more difficult to try and extrapolate the behaviour of the 720 Hp 132-G from this graph!

    What I have done, is drawn in the 1.2 ATA graph in red, corresponding to the 132-G engine that delivered 720 Hp at S.L., and maintained 1.2 ATA upto 1800 meters, 5900 ft. I wonder if this could be plausible.

    Consequently, I would wager that the peak at critical altitude should be about 760 Hp, perhaps not 791, as Iīm getting now, and that the 657 Hp at S.L. would be quite low.


    Cheers,
    Aleatorylamp
    Last edited by aleatorylamp; May 24th, 2017 at 12:43.
    "Why make it simple if you can also make it complicated?"

  17. #167
    Hello Aleatorylamp,

    You do realise that as soon as you significantly (and it does not take much to be significant) alter the power curve, the propeller tables need to be rebuilt again, right?
    That is why I was waiting for you to be really sure about your power and performance numbers before even looking at anything.

    - Ivan.

  18. #168
    Hello Ivan,
    OK, thanks. I understand. But perhaps the propeller tables are OK notwhithstanding, because Iīm trying something that might work to get the curve better:

    After getting the torque graph to give me about 720 Hp at 300 ft, Iīve lowered Boost gain a little so that the 800 Hp peak at critical altitude of 5900 ft critical goes down to 764 Hp. Drag is adjusted so that Iīm getting about 225 mph at S.L. and about 243 mph at Critical Altitude. Then Iīll test some other altitudes further up and see what happens.

    Of course, this slight reduction in Boost Gain has an adverse effect: Manifold Pressure is supposed to stay at the maximum 34.87 upto critical altitude, and it doesnīt anymore - it went down to 33.4 - so perhaps my idea is not so good after all.

    Update:
    Iīve started testing a bit further up, and it gets better.

    For the moment itīs back to about where I was a short while ago:
    S.L: Correct 720 Hp at 2023 RPM, and 224 mph (OK)
    Critical altitude 5900 ft: quite high 811 Hp, with 2223 RPM, and 246 mph (OK).
    and higher up at 9800 ft, much better 695 Hp, with 2210 RPM, and 245.2 mph (OK).

    I have had no time to test cruise speeds yet, but tomorrow is another day!

    You mentioned that pitches were not exactly 18 and 35, which is what Iīm getting - probably because my beta-min and beta-max are defined as 18 and 35 in the air file. Should I define other values for this?

    Cheers,
    Aleatorylamp
    Last edited by aleatorylamp; May 24th, 2017 at 14:42.
    "Why make it simple if you can also make it complicated?"

  19. #169
    Hello Aleatorylamp,

    I was getting 719 HP @ 500 feet and 223 MPH or so before I quit testing.
    I was only testing for the propeller pitch versus power, so that was sufficient.
    I am not sure it was at full RPM at the time, but those values were pretty close at least for power.

    The comment I made about Low Pitch and High Pitch angles is because I suspect that although 18 degrees seem pretty optimal when running a CS propeller, the actual aeroplane probably had a higher Minimum Pitch than 18 degrees because this model was coming off its minimum pitch just after the take-off run.
    Then again, this kind of depends on the match of the original Power Coefficient Table.
    Another indication that this number was too low is the huge dip in efficiency between 18 degrees and 35 degrees in the Efficiency Table.
    The Efficiency drop between 18 and 35 was hidden earlier by use of a CS propeller.

    You have quite a few variables here, so there may be more than one solution.
    Obviously we CAN get 18 degrees Minimum Pitch to work.

    By the way, here is an illustration of how things can get interesting:
    I was originally working from your performance data sheet which says
    5900 feet ---- 757 HP
    I presume this was at 2050 RPM which with a Constant Speed Propeller is pretty much guaranteed.
    Cp = 0.060919


    Now you have 764 HP which probably is not significantly different if it is still at 2050 RPM.
    Power Coefficient would be very slightly higher but not enough to make a difference.
    Cp = 0.061482

    Not VERY different at all, but you will notice a slightly earlier shift to High Pitch.


    But for 811 HP at 2223 RPM, Life gets interesting. You remember I said earlier that things are not always intuitive....
    Cp = 0.051183

    Hmmmm..... My guess is that you might notice it NOT shifting to High Pitch until around 240 MPH to 245 MPH or so.
    Perhaps it would even be past your maximum level speed?
    This is by eyeball correlation of the version of Propeller Tables as I sent them to you.
    This time around I did NOT do any very precise calculations other than for Cp which is pretty easy.
    Bottom line is that the shift point WILL be higher and performance will be pretty awful until that shift happens because the Propeller Efficiency is dropping very fast at that speed with 18 degrees pitch.
    At 245 MPH you would get around
    40% Efficiency with 18 degrees Low Pitch
    and
    73% Efficiency with 35 degrees High Pitch

    Life can get really messy really fast here.

    - Ivan.

  20. #170

    Letīs try a higher low pitch.

    Hello Ivan,
    Thanks for your post. Yes, it is a very interesting experiment!
    A good side-effect is that you seem to be getting some information out of it for your Ki-61 as well.
    All the better!

    The 757 Hp at 5900 ft would be fine, better than 764 or 760, but then S.L. power would go even lower!
    The thing was that due to the increased peak at 5900 ft, I was willing to accept 764 Hp, instead of 575, just so to get away from the >800 peak there.

    I was basically just rounding it off to 760 Hp, which was only a decuction I had derived from the pencilled graphs of the CV-prop -DC or -H1 engine, whose power graphs "conveniently" included a graph for 720 Hp.
    However, 757 Hp is of course better, because of the less efficient propeller.

    I think it will be better to leave that part of the curve alone then.


    So, you are saying that increasing low pitch will give us more S.L. power, which will be necessary.
    Iīll go with that!
    An increase there will bring down the >800 peak at 5900.
    As you say,
    the CV prop will have hidden the lower efficiency of the 18 degrees.

    I did some more altitude tests, and got very satisfying results:
    12500 ft: 242.6 mph, 610 Hp, 2166 RPM
    15000 ft: 242.0 mph, 546 Hp, 2174 RPM
    19700 ft: 237.5 mph, 434 Hp, 2137 RPM

    Then I did some 12500 ft Cruising tests, which were also good:
    Fast cruise, at 0.8 ATA: 224.8 mph, 477 Hp, 2018 mph
    Normal Cruise 0.76 ATA: 217.3 mph, 422 Hp
    Eco-Cruise at 0.73 ATA: 208.0 mph, 370 Hp, 1870 RPM

    OK, then. Would you think that the default setting of 20 degrees used for fixed pitch propellers would be best?
    I remember trying out fixed propellers on the Condor and they seemed to work quite acceptably.

    Another thing you mentioned, is the speed at which the propeller would come off low pitch.
    On one hand, you say that it comes off low 18 pitch very soon after the take-off run, and on the other, low pitch seems to be maintained all the way up to 195 mph. Higher would of course make things messy, as you say.
    If you are suggesting that this could be lowered, I expect it would be better, so we wouldnīt get the propeller staying at low pitch at 195 mph.

    P.S. Still another thing you said: While testing, you were getting 719 Hp at 500 ft and 223 mph. Thatīs fine! I can readily accept that - itīs not really very different from 720 Hp at 300 ft with 226.8 mph.
    This, combined with the 575 Hp at 5900 ft would be perfect! Strange that I am only getting either one or the other of these correct at any time, not both.

    Question: Is it possible to have the same power of 719 Hp at 500ft both with low pitch and relatively low speed, and then ALSO with high pitch at higher speed? I would expect, technically yes...

    Cheers,
    Aleatorylamp
    Last edited by aleatorylamp; May 25th, 2017 at 04:04.
    "Why make it simple if you can also make it complicated?"

  21. #171

    Communications

    Hello Aleatorylamp,

    Actually the issue I noticed that will get me to revisit the Ki 61 Propeller is negative Power Coefficients.
    The numbers I am using right now pretty much mimic the stock Propeller Tables in that respect, but with the radical edits to get your Propeller Power Coefficient Table, it occurred to me that this probably was not the right approach.
    Free time over the last couple days has been spent reading up on Windmilling Propellers and their effects.
    It IS related to the Ki 61 propeller table, but in reality has more to do with working on the twin engine stuff.
    If your single engine fighter loses an engine, you WILL go down. It is just a matter of time and angle of how you meet local terrain.
    With a twin (and less so with more engines) single engine performance simulation is fairly important and I knew very little about that area until recently.
    The next step is to create an experiment that can give better insight into how CFS handles negative Power Coefficient values.
    As usual, one "new" idea puts a whole lot more stuff on the task list.

    Quote Originally Posted by Aleatorylamp
    Another thing you mentioned, is the speed at which the propeller would come off low pitch.
    On one hand, you say that it comes off low 18 pitch very soon after the take-off run, and on the other, low pitch seems to be maintained all the way up to 195 mph. Higher would of course make things messy, as you say.
    As often happens, we are seriously miscommunicating again:
    When I described changing pitch from 18 degrees just after take-off, I was referring to the original CS propeller.
    It would obviously be dependent on the stock Hurricane's Power Coefficient Table that you were using, but since it was matched to your engine by Power Coefficient value similarity, it would imply that 18 degrees allows your engine to reach full RPM just after take-off which is great for a CS propeller but suggests that 18 degrees is too fine of a low pitch value if you ONLY have two angles instead of a whole range in between.
    Arriving at this conclusion is not exactly that simple because the advance ratio between the Hurricane and FW 200 are so different, but it is one piece of data that should not be ignored.

    Please Review the attached Screenshot of the Propeller Efficiency Table (511) from the Condor.
    Note that I have removed the graphs for 25 degrees and 30 degrees to reduce the clutter and because they were not really relevant to this discussion.

    The two pitch values in use are Red Dash lines.

    Note where they cross. That is where we would want a propeller pitch change for optimum performance.

    Note the values just above the Advance Ratios. Those are the True Airspeed MPH for each Advance Ratio assuming 2000 RPM.

    Note also that the rising slopes and peaks of these efficiency graphs (other than for 25 and 30) are unmodified from the original values used for the Constant Speed Propeller.
    One of the big advantage of the CS propeller over the two-pitch is that it can maintain a full 2050 RPM pretty much at any speed above about 100-110 MPH while the two-pitch propeller tends to lug below its optimum airspeed.

    Remember I stated that the rising slopes and peaks were unaltered.
    Note from the screenshot that 18 degrees and 15 degrees pitch have VERY small advantages over 20 degrees but past J=0.6, their efficiency drops VERY badly and I even raised the efficiency of the 15 degree graph at J=0.8 so that the interpolation for 18 degrees would not be quite so bad.

    Quote Originally Posted by Aleatorylamp
    OK, then. Would you think that the default setting of 20 degrees used for fixed pitch propellers would be best?
    I remember trying out fixed propellers on the Condor and they seemed to work quite acceptably.
    So.... To make a short answer VERY LONG.... a low pitch value of 20 degrees makes a whole lot more sense from an efficiency and geometry standpoint than 18 degrees.

    Quote Originally Posted by Aleatorylamp
    P.S. Still another thing you said: While testing, you were getting 719 Hp at 500 ft and 223 mph. Thatīs fine! I can readily accept that - itīs not really very different from 720 Hp at 300 ft with 226.8 mph.
    I told you I was limiting changes to just the propeller tables. That was so we could discuss things from a known common point.
    That didn't mean that there were no other problems.
    If 719 HP instead of 720 bothers you, adjust it up a touch.... You actually have a lot of room at Sea Level to do this because the Power Coefficient is much much lower than elsewhere.
    If the lower speed bothers you, adjust the Coefficient of Drag. If that not precise enough, increase the Oswald Efficiency number to bring it back down again because that number is a bit on the low side anyway.

    Quote Originally Posted by Aleatorylamp
    Question: Is it possible to have the same power of 719 Hp at 500ft both with low pitch and relatively low speed, and then ALSO with high pitch at higher speed? I would expect, technically yes...
    I don't see why you can't, but I believe the problem here is not so much the power as reaching a consistent RPM and that may be a lot more difficult. That is why I suggested using the torque curve to keep power very similar for the operating range you want (as I did for the Ki 61) and use differences in manifold pressure to control engine output.
    This is not unrealistic when compared to the torque graphs from real engines though you have to remember that real engines don't factor out friction into yet another graph when they are being dyno-ed.

    - Ivan.
    Attached Thumbnails Attached Thumbnails Condor511-Screenshot.jpg  

  22. #172
    Hello Ivan,
    Thanks for your explanatory post. I see that I have understood most of it, and other posts, except for where and how the 4 different variables all interact - thatīs where I get lost, but I donīt think thatīs the problem.

    Iīm fine with 20 degrees for low pitch. I limited minimum pitch to 20 instead of 18, and take-off was fine, so weīll be fine with the new value. No problem. I donīt think thereīs any problem with the pitch switch either, and thereīs no problem at higher speeds. The prop always goes into 35 pitch there.

    The headache is the 811 Hp peak at critical altitude instead of the expected or hoped 757 Hp.
    I wouldnīt mind even 770 Hp, for that matter, and from what I can see, it has nothing to do with the change in low pitch.

    Alternatively, looking at it from the opposite side, tuning the curve down to get the peak into manageable levels, i.e. 764 Hp or even 770 Hp, as near as possible to my 757 Hp), the headache is then the reduced 657 Hp at S.L.

    The manouevering capacity offered by modifications in Drag, Oswald Factor or Torque Graph is too small to help here.

    Cheers,
    Aleatorylamp
    "Why make it simple if you can also make it complicated?"

  23. #173
    Hello Aleatorylamp,

    You have me pretty confused by the last couple posts about your engine power issues.

    From your performance document:
    1) S.L. 300 ft: 226.6 mph
    720hp - 34.9 MP (1,2 ATA)
    Pitch 26.4, Thr: 1010
    2) 5900 ft: 243.6 mph
    757 Hp - 34.9 MP (1.2 ATA)
    Pitch 29.0, Thr: 984
    3) 8500 ft: 243.0 mph
    689 Hp – 31.7 MP (1.1 ATA)
    Pitch 28.9, Thr: 897

    Are you telling me that you did not actually get these numbers in testing?
    Or are you telling me that a change in the propeller tables radically changed the engine output?

    - Ivan.

  24. #174
    Hello Ivan,
    The performance document dates from a date which is rather older than the new propeller tables.
    Why would I want to do all that testing again? The older .air file. is tested, done and finished.

    The first part of the document states the specifications of the real aircraft, and the second part
    describes the actual model performance results - with the old .air file, of course.
    Why would I write out a performance document stating test results that I didnīt get? I donīt
    understand your comment.


    When you sent me the new propeller tables, a couple of days ago, the first thing was to see how
    they worked, and of course I started testing them. Once I saw how they were doing, the next
    step was to try and adjust performances as closely as possible to the specifications and/or
    performances described in the performance document.

    The first thing I noticed was how effectively the low and high pitch were working, the 18 or 20
    degree issue for
    low pitch being a rather minor affair.

    It was then that I encountered the problems I have been describing: Now I can either have
    720 Hp at S.L. with an 811 Hp peak at CA, or I can have correct output at
    C.A. with by far
    insufficient power at S.L., and Iīm trying to correct this without much success.

    So, I went back to the new .airfile you sent me a couple of days ago, with the new propeller
    tables 511 and
    512, and with NO other alterations. Just for the record, these are the maximum
    speed, power and RPM
    readings for this new .air file, all speeds at 35 pitch:

    __300 ft: 214.0 mph, 712 hp, 1985 RPM
    _5900 ft: 235.8 mph, 808 hp, 2198 RPM
    _8500 ft: 235.2 mph, 728 hp, 2182 RPM
    _9800 ft: 234.5 mph, 689 hp, 2172 RPM
    12500 ft: 232.8 mph, 608 hp, 2149 RPM
    15000 ft: 231.0 mph, 542 hp, 2125 RPM
    19700 ft: 224.1 mph, 431 hp, 2075 RPM

    I hope this helps.
    Cheers,
    Aleatorylamp
    Last edited by aleatorylamp; May 25th, 2017 at 13:05.
    "Why make it simple if you can also make it complicated?"

  25. #175
    Sorry Aleatorylamp,

    It didn't come out quite the way I had intended.
    I was wondering if the test performance was of the AIR file you sent to me or an earlier version because I know that you tend to make a lot of little adjustments very quickly.
    I had the same issue when looking at old test results for my Ki 61.
    I was working on version 0.58 and the test sheet I was looking at was for version 0.55.
    The new results I was getting obviously did not match all that well.
    The changes were not great, but there were enough differences that I had to go back and redo a few things.
    Luckily I make a habit of documenting the significant changes IN the AIR file and could trace things back to version 0.55 and see when things had changed.

    I believe I know where the problem lies and how to go about correcting it.
    The problem is that this is complicated enough that I can't just give you more than just general directions on where the changes need to be made because it is a matter of changing something and seeing if something else needs to be changed.

    I believe that the windmilling propeller aspect will need to be removed to get the proper performance which means that the propeller tables need to get tuned again.
    Basically what is happening is that the new Power Coefficient Table is pretty good for 18 degrees but for there not to be a possible stable angle between 18 degrees and 35 degrees, the graph for 35 degrees needs to be very very close to that for 18 degrees and is being brought down too fast and does not supply resistance to keep RPM from climbing.
    The best way to do things is to bring the 18 degree curve up to the one for 35 degrees but then even when efficiency drops to zero, it will not windmill because the curve is still positive.

    As I commented before, the interactions are complicate enough that it would be a whole lot quicker for you just to send me what you have (if you have changed anything you want to keep) and let me do the final performance tuning.
    If you haven't changed anything you need to keep, I can tune to best match your performance sheet, but I will warn you in advance that I don't generally try to get as close as you do to the target number.
    I tend to numbers slightly higher than the specification.
    If there are some numbers you are trying to change from the performance document, please let me know that also.

    My apologies again for doubting your test results.

    - Ivan.

Members who have read this thread: 5

Bookmarks

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •