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Thread: Warhawk

  1. #201

    Hawk 87W - Update

    There hasn't been much activity on the Hawk 87W (P-40N) but there has been some.

    The SCASM processing is now complete.
    This means that further texture updates will be much simpler because the files are BMP format.
    The animation changes are also complete.

    One thing that has bothered me for a while is that the low speed handling of the P-40 seemed to be too good.
    There appeared to be way too much control authority.

    My task over the last couple days was to adjust the low speed control without compromising the generally excellent handling.
    After creating spreadsheets to graph the control effect versus aerodynamic force (1/2 Rho V^2) and making adjustments,
    I found that what I arrived at for new values was not significantly different from what is currently in place.
    In other words, it appears to be pretty well tuned (or where I want it to be) now.

    There was one area in which the values were different; My new values for Rudder Effect were a bit lower at low speed.
    The question then becomes: Is the Rudder Effect too high or is the Propeller Torque Effect too low?
    In any case, the Low Speed Rudder Effect is only noticeable if the Tail Wheel is made free castoring instead of steerable which means that in the actual flight model with a steerable Tail Wheel it is invisible.

    The other minor change is to test a different texture pattern on the Spinner.
    The later model P-40 especially when used by the RAF, RAAF, and RNZAF had a tendency to use two colours there.
    The texture is a bit harder to apply than usual because it is Fore-Aft instead of Left-Right.

    - Ivan.
    Attached Thumbnails Attached Thumbnails WarhawkSpinner.jpg  

  2. #202
    Hello Ivan,
    Sounds as though progress is being made!

    At least you have done something, wheras in my case Iīve been totally inactive - with the German course for waiters thereīs no energy left for building aircraft. The timetable is two hours daily at midday and it gets in the middle of cleaning, cooking and lunch and Iīve got a kind of buiderīs block"! Perhaps when the private students have their holidays as of June or July Iīll have some free afternoons to pursue FS building.

    Regarding the steerable tailwheel in FS, I find the way it is controlled in the opposite direction so confusing that I prefer not to have it.

    Cheers,
    Aleatorylamp

  3. #203
    Hello Aleatorylamp,

    Actually I have been working on other projects.
    Some are even CFS related.
    You might have seen my thread in "Other Hobbies".
    There are a few things in that direction that needed pursued.

    - Ivan.

  4. #204

    Under the Knife

    The Technicians and Test Pilots have been working on a little project with the P-40N which has finally come down to a matter of fine tuning.

    Several of the staff were on the Me 109E Trop project and used that aeroplane to experiment with directional control parameters to try to fly a "Knife Edge". The lessons from that project were added to the P-40N where they are working as expected.

    The screenshot shows the P-40N maintaining altitude though drastically losing airspeed while doing it.
    The adjustments are needed to lower the amount of airspeed that is lost so that this maneuver can be flownfor longer.
    Note the low airspeed and extreme yaw angle.

    - Ivan.

    -
    Attached Thumbnails Attached Thumbnails KnifeEdge.jpg  

  5. #205
    Hello Ivan,
    Wow! I believe the Germans call it the "hammerhead".
    It is a very intriguing manouever, this one, how to have the fuselage and vertical stabilizer as sustaining surfaces... totally mind boggling!
    Cheers,
    Aleatorylamp

  6. #206

    Flight Model Updates

    It seems like CFS Superchargers have a bit more capability than I had thought.
    Aleatorylamp came across an interesting supercharger power reduction by adjusting a parameter identified as

    WEP Pressure Change Rate (0.528 or Zero)

    This parameter apparently works as modifier to the SuperCharger Boost Gain parameter.
    If set to Zero, there is no additional power when using WEP above the critical altitude.
    By doing this, the high altitude WEP effect which was causing problems is gone.

    Unfortunately, the testing also showed that the parameters which were modified to allow knife-edge flight affected lateral stability and control in a very unfavourable way so until I can compensate in the AIR file this feature will not be included.

    - Ivan.

  7. #207
    Hello Ivan,
    Iīm glad that regulating the WEP Pressure Change Rate has cured the P-40īs excessive WEP effect at altitude, and hopefully youīll find a way of correcting the knife-edge lateral stability side-effects!
    Cheers,
    Aleatorylamp

  8. #208
    The P-40N didn't have the greatest problems with WEP at altitude; The P-40K and P-40E were quite a bit worse.

    The P-40K also has a new visual model which may the excuse for an updated release.

    In playing with the P-40N, it just did not look right without a shark mouth, so the last couple evenings were spent in repainting the cowl to put a shark Mouth there.

    - Ivan.
    Attached Thumbnails Attached Thumbnails P-40N-SharkMouth.jpg   P-40N-HeadOn.jpg  

  9. #209
    Hello Ivan,
    The Sharkmouth is definitely an asset for this model!
    Cheers,
    Aleatorylamp

  10. #210

    Climb Performance Testing

    Last Night, I ran a test of the P-40N's Climb Performance.

    Results are the following:
    Best Climbing Airspeed is around 195 MPH TAS.
    Yes, I know it varies in IAS with altitude.

    While holding 195 MPH TAS, Climb Rate was
    2800 feet / minute at 500-1,000 feet altitude
    2885 feet / minute at 5,000 feet altitude
    3000 feet / minute at 10,000 feet
    3085 feet / minute at 12,000 feet

    At 5,000 feet, 195 MPH works out to be about 180 MPH IAS, so that is the number I will use for record.
    The climb rates seem to be where I would have wanted them.

    The plan is to test again using IAS at some point to find the Indicated Air Speed at which I can get the best climb rate.

    - Ivan.

  11. #211

    Service Ceiling Test

    Starting with 55% fuel the P-40N Service Ceiling appears to be
    32,700 feet with 509 HP at 293 MPH TAS which is pretty close to 180 MPH IAS.
    Remaining fuel was 64.3 Gallons (73.5 Gallons would be 50%).

    Absolute Ceiling appears to be just over 35,050 feet with 442 HP.

    Unfortunately for me, I started this test fairly low at 27,500 feet, so the actual test took much longer and burned more fuel that I expected.
    The Service Ceiling is a bit higher than I would have wanted, but this was done with autopilot.
    A manually flown test would probably end up a bit lower but also would be a bit harder to reproduce.

    I will probably repeat this test at some point to try to have it finish with 50% fuel.

    - Ivan.

  12. #212
    Hello Ivan,
    Thanks for this useful information. It comes in very handy for my Baltimore Mk.V and MkIIIA/IV tests.
    Cheers,
    Aleatorylamp

  13. #213
    A second test of the Service Ceiling gave 32,400 feet with about 71.5 gallons fuel remaining.

    Climb Rate specifications seem to vary quite a lot depending on the test conditions.
    A test report of the P-40N-5 running at 44 inches Hg showed only a bit over 2200 feet / minute.
    A test report of the P-40N-1 running at 57 inches Hg showed 3100 feet / minute.
    My own test of my "P-40N-15" at 52 inches Hg gave about 2800 feet / minute which seems quite in line with the actual test reports.

    It has been uploaded.

    Hello No Dice,
    You wanted a P-40N for your birthday a couple years back.
    This version is either a few years late or a month or so early.
    I will send you a copy shortly.
    (Anna Honey says I need to prep for some guests now.)

    - Ivan.
    Attached Thumbnails Attached Thumbnails Hawk87W_ServiceCeiling.jpg  

  14. #214
    Hello Ivan,
    A very nice quality-contribution, this long-tail, and a great flier too!
    This time I was careful on take-off and my pride was left intact!
    Cheers,
    Aleatorylamp

  15. #215
    Thanks Aleatorylamp.

    I liked the way it turned out also.

    Next step is to go back and finish up a P-40M which should not be difficult and also to rework the P-40E and P-40K flight models.
    Then there are the P-40C models..... The list is endless.

    - Ivan.

  16. #216
    Hello Ivan,
    Itīs turning out to be quite a unique collection!
    Aleatorylamp

  17. #217
    am in Cambridge, MAssachusetts at the moment and on an iPad.
    Not going to be on much for a few days.

    - Ivan.

  18. #218
    Version 011 contains an updated AIR file.
    There are no performance changes.
    The Aircraft Type Identification has been changed.
    The Length specification in the Description has also been changed.
    (The earlier version listed the length of a Short Tail Warhawk.)

    - Ivan.

  19. #219

    Long Tailed Merlin

    A while back, after receiving an email about No Dice, I was thinking about how he always had a way of giving praise for the projects I had released.
    I went back and found one of the old threads: The one that described the Merlin P-40F, my latest project at that time.
    As usual, he had some nice compliments.

    I followed the thread a bit and my plan at the time was to work on a proper Long-Tail P-40 and then build the Long Tail versions of the Merlin P-40. I had actually gotten pretty far as detailed in THIS thread.
    The P-40M was completed but not released because I could not decide on a good paint job.
    The P-40K was also worked on though I cannot remember where I left it.
    The P-40N was completed and released and even had an immediate update for an error in the description.

    I never actually went back to the Merlin P-40.

    A few months ago, on another forum, there was a very long running discussion about the merits of the Merlin P-40 and its relative performance as a fighter against its contemporaries. There was quite a bit of information presented and some of it resolved some contradictions that I had encountered when working on the original version of the flight model.
    These discussions and the old thread "Ivan's Latest and Greatest" were the reason behind this latest round of updates.

    The updates turned out to be quite easy.
    The model updates were lifted from the P-40N; The longer tail was designed specifically so that the pieces would match easily to the current version of the Short-Tail Warhawk.
    Texture updates were tedious as usual, but not as bad as they could have been because with the design of the Long-Tail, the textures were arranged so that only one mapping edit was needed and only one texture needed to be edited (in theory).

    Attached are some images of the completed textures as applied on the model.
    There are more images and historical information in the thread mentioned earlier.

    - Ivan.
    Attached Thumbnails Attached Thumbnails P-40F-5_Stab.jpg   P-40F-5_Painted.jpg   LongTail-F_Bottom.jpg   LongTail_F_Top.jpg  

  20. #220

    New Propeller

    As part of the updates to the flight model of the P-40F, I thought it would be a good idea to manufacture a custom propeller to replace the current propeller which probably came from the stock P51D.

    None of the P-40 projects that I have released thus far have had anything but a stock propeller with all of its problems.
    Doing a quick comparison showed that just about all the P-40s had pretty comparable propellers with only small variations because of engine output and critical altitude. The only real exceptions were the Merlin equipped versions which used a different reduction gear ratio.

    With this in mind, it made more sense to build a propeller that was best suited for the Allison P-40 and adapt it to the Merlin as was probably done in real life. The P-40N was selected as the development aircraft because its flight model was the most recent and least likely to have other problems.

    The First screenshot shows a speed run after testing to determine engine output at each altitude.
    370 MPH @ 12,500 feet with 1351 HP on Military Power.
    370 MPH can also be achieved at 10,000 feet with 1479 HP on War Emergency.
    Critical Altitude is 12,850 feet.

    Second and Third screenshots show current Propeller Tables 511 and 512 which have the standard Perpetual Motion curves.

    - Ivan.
    Attached Thumbnails Attached Thumbnails SpeedRun.jpg   P40N-511_original.jpg   P40N-512_original.jpg  

  21. #221

    New Propeller - First Attempt

    As some folks may already know, a Propeller for Combat Flight Simulator is really composed of two Records:
    Record 511 - Propeller Efficiency
    and
    Record 512 - Propeller Power Coefficient

    In my opinion, just about any reasonable Propeller Efficiency Table is a suitable starting point as long as it doesn't have the "Perpetual Motion" curves AND as long as the Propeller Power Coefficient Table matches it.

    For a starting point, I decided to use the original Record 511 with minimal but essential modifications.
    The efficiency curve for each blade angle now drops to Zero when the Advance Ratio is high enough that the blade cannot maintain a positive AoA. Note that there is also a bit of an allowance for camber and also for the problem that 0.2 is a pretty large change in Advance Ratio but is the smallest increment we can represent in the table and still have a reasonably wide range of speeds.

    To cover the practical range of speeds that the P-40 was capable of, the maximum Advance Ratio was extended to 2.8 which at 3000 RPM would be the equivalent of 525 MPH. This would be pretty close to the maximum speed expected in a power dive.

    Note that the stock P-51D Record 511 only goes to J=2.2 or the equivalent of 402.6 MPH which doesn't even cover its entire level speed range much less its potential speed in a dive. This is actually a neat way to cheat. At the upper end of the speed range, Propeller Efficiency tends to drop very quickly but since the simulator uses the value for J=2.2 if J is above 2.2, your propeller would be providing much more thrust than it should.

    The added columns for 2.4, 2.6, and 2.8 are what I believe are reasonable continuations of the curves.
    If there are any mistakes, they should not affect the first round of testing which was at or below J=2.0 (375 MPH).

    The original Record 512 had too many odd curves so I decided to use a replacement that I generated using a spreadsheet I wrote for the purpose a couple years ago. The curves are smooth because they are generated by parameters fed into a formula.
    The highlighted cells show the places where I tried to match the original Power Coefficient curves.

    Test Results to Follow.

    - Ivan.
    Attached Thumbnails Attached Thumbnails P40N-511_Mod1.jpg   P40N-512_Mod1.jpg  

  22. #222

    New Propeller - Mod1 Testing

    The updated AIR file loaded into CFS without problems.
    That was a good sign. Formatting errors in the past have caused load failures.
    Engine started - Another good sign.
    Idle Speed 496 RPM - Unchanged from original which made me suspect I might be using the wrong AIR file.
    Sea Level Military Power (1210 HP)
    312 MPH - same.
    Propeller Pitch 35 Degrees - same
    1230 Pounds Thrust - Higher! - Original was 1225 Pounds.

    Sea Level War Emergency Power (1358 HP)
    322 MPH - same.
    Propeller Pitch 37 Degrees - same
    1302 Pounds Thrust - same.....

    10,000 feet War Emergency Power (1479 HP)
    371 MPH - same.
    Propeller Pitch 41 Degrees - same
    1333 Pounds Thrust - Original value unknown, I didn't write it down.

    12,500 feet Military Power (1351 HP)
    372 MPH - Higher. Original was 370 MPH
    Propeller Pitch 41 Degrees - same
    1242 Pounds Thrust - Higher. Original was 1219 Pounds.

    For a first attempt, this was a LOT closer than I was expecting.
    I believe the slight differences are due to slight differences in propeller pitch (less than a degree) and my tuning of the Power Coefficient Table was done by eyeball. There are also limitations with trying to match the odd curves of the original tables (not that I want to) using math formulas.

    The Efficiency Table definitely needs to have some of the mismatched curves smoothed out and adjusting the efficiency down slightly to reproduce the same maximum speed is pretty trivial.
    The question is whether or not the adjustment is really necessary.....

    - Ivan.

  23. #223

    New Propeller - Mod4 Testing

    Yesterday, I had to work with my Son on a writing assignment and didn't get much time with the simulator until fairly late in the evening.

    As can be seen by the title of this post, there have been quite a few changes.
    I was already pretty close, so the first set of changes (Mod2) was just to make some basic corrections to both Tables.
    These changes were simple things such as smoothing out the curves where there were obvious continuity problems and adjusting the efficiency numbers at 0.0 Advance Ratio. (In theory this should be zero but that isn't how CFS works.)
    The Power Coefficient Table was also adjusted at the coarse pitch angles to be closer to the original even though it should have no effect at the power levels and speeds reached by the P-40N.

    There was quite a bit of flight testing especially for level acceleration during which I found that the low level maximum speed was achieved just past one of the dips in the Propeller Efficiency curve (caused by interpolating between 30 degrees and 35 degrees).
    This created an interesting situation which I entirely missed in my previous test runs because I had been using War Emergency Power to get close to the maximum speed before switching back to Military Power to allow speed to climb the last couple MPH.
    The WEP was pushing past the dip. Without WEP, maximum speed was barely above 300 MPH - Sometimes....

    Why SOMETIMES?
    My testing protocol is to record a speed as "maximum" if it has not increased by 1 MPH in 15 seconds.
    The timing is done manually so I may be a couple seconds off at times.
    Let's say that the acceleration slows at 304 MPH so that to reach 305 MPH SHOULD take 14 seconds.
    If my timing is fast, I record it as 304 MPH and quit.
    If my timing was a little slow, I might accept it as 305 MPH and then see how long it took to reach 306 MPH.
    At certain parts of the Efficiency curve, the acceleration might actually increase and not slow down again until overcome by drag at 312 MPH.

    Sea Level Military Power (1210 HP)
    313 MPH - Higher
    Propeller Pitch 34 Degrees - Finer Pitch
    1235 Pounds Thrust - Higher! - Original was 1225 Pounds.

    12,500 feet Military Power (1351 HP)
    370 MPH - Same.... Back down to original speed
    Propeller Pitch 41 Degrees - same
    1222 Pounds Thrust - Higher. Original was 1219 Pounds. This is about as close as it gets.

    In reality it took more than just three more versions of the Propeller Tables.
    It was more like three major revisions and a dozen minor revisions for fine tuning.
    I also found out that one of my tools was very unreliable and needs a bit more programming work.

    Next comes the Climb and Service Ceiling Tests which are sure to be followed by further revisions.

    - Ivan.

  24. #224

    New Propeller - Mod 5 Testing

    This update really should be described as testing of Mod 5 version 65 or something along those lines.
    There have been enough little changes that I haven't bothered to keep an accurate count.
    The week has been very busy but most of it has not been related to flight simulators. Real life intrudes sometimes.

    The Climb Test was pretty much a complete failure.
    The Propeller would select way too coarse a pitch and climb rate was several hundred feet per minute too low.
    My original intent was to hold the two endpoints of each curve in place and only adjust the curve as needed but that was not enough to come up with a working set of graphs for Table 512.

    Altering the endpoint at Zero Advance Ratio seemed to be the best idea; I could significantly improve the shape of the curves and all that would happen is that the Idle speed would change.
    This was done and the Climb Rate was greatly improved. Idle speed went from 496 RPM to 417 RPM.

    The minor adjustments of the curves to improve Climb also seemed to make the Speed at 500 feet a bit worse.
    The maximum was still 312 MPH most of the time, but Acceleration felt slow. This was not surprising because the Propeller Pitch only reached 33-34 degrees which coincided with where both the 30 degree and 35 degree curves dropped off just past J=1.6.
    Adjusting the curves at J=1.6 didn't help much because the real value was J=1.664 and the 30 degree curve dropped to Zero at J=1.8.

    The last idea I tried was to use the Power Coefficient Table to reduce the power requirements for 35 degrees at J=1.6 and even out the curves before and after and it seemed to solve the problem.

    Test results have now changed to the following:

    Sea Level Military Power (1210 HP)
    317 MPH - Significantly Higher
    Propeller Pitch 35 Degrees - Same
    1264 Pounds Thrust - Significantly Higher - Original was 1225 Pounds.

    12,500 feet Military Power (1351 HP)
    370 MPH - Same.... Back down to original speed
    Propeller Pitch 41 Degrees - same
    1221 Pounds Thrust - Higher. Original was 1219 Pounds. Basically the same.

    Climb Rate at 5000 feet is 2900+ feet / minute or pretty close to previous.
    Actual climb rate is probably between 2950 and 3000 feet / minute but autopilot isn't that precise.
    Speed is 180-185 MPH IAS.
    Power is around 1260 HP.
    Climb at WEP was not tried.

    Climb Rate at 10,000 to 13,000 feet is about 3000 feet / minute at 175-185 MPH IAS.
    Speed wasn't precise because it changes slightly during the climb and a couple MPH difference does not appear to make any significant difference.
    Power is around 1323 HP.

    Climbs were done with nearly full fuel so rates should be a bit higher with only partial fuel.

    Now for a Service Ceiling Test

    - Ivan.
    Attached Thumbnails Attached Thumbnails P40N-511_Mod5.jpg   P40N-512_Mod5.jpg   P-40N_Climb5000.jpg  

  25. #225

    Climb Rate & Service Ceiling

    The slightly lower climb rate bothered me a little, so I made a small change to the Propeller Efficiency at J=0.8.
    I also tried adjusting the Power Coefficients to be able to hit full RPM a little earlier but that did not work out well.
    The new climb rates are nearly unchanged but they can be achieved at a wider range of speeds.

    Climb Rate at 5000 feet is about 2950 feet / minute and increasing to almost 3000 feet / minute.
    Speed is 175-185 MPH IAS.
    Power is around 1260 HP.

    Climb Rate at 10,000 to 13,000 feet is about 3000 feet / minute at 165-175 MPH IAS.
    Power is around 1323 HP.

    Climb Rate at 14,000 feet falls to around 2800 feet / minute at 165-175 MPH IAS.
    Power is around 1275 HP and falling quickly.

    Service Ceiling seems to give a range of values from 32,100 feet to 32,700 feet.
    Typical Results:
    Service Ceiling: 32,580 feet
    Speed: 293 MPH TAS (174 MPH IAS) - Propeller Pitch: 35 Degrees.
    Power: 514 HP
    Remaining Fuel: 75.4 Gallons.

    After the Service Ceiling test, I tried a high speed dive and then concluded with an actual landing without breaking the aeroplane. The wobbly landing tells me I need a LOT more practice.

    Attached are the updated Propeller Efficiency Table and a Screenshot of a Warhawk that didn't miss the runway on landing.

    - Ivan.
    Attached Thumbnails Attached Thumbnails P40N-511_Mod6.jpg   P-40N_Landed.jpg  

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