Reworking Eric Johnson's Airacobra - Page 2
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Thread: Reworking Eric Johnson's Airacobra

  1. #26

    Status Update

    The recent diversion to work on the P-47D-23 was actually very related to working on the flight model for the Airacobra.
    Both have quite similar centers of gravity though quite different conditions.
    The CoG is pretty far aft in the Thunderbolt when it is fully loaded but stability improves as fuel is burned from the aft fuel tank and is pretty good by the time all fuel and ammunition are expended.
    The CoG is slightly further ahead on the Airacobra and moves rearward as stores are expended and the aircraft becomes increasingly unstable.

    The last version of the AIR file I worked on several months ago (which I will call the "Version A") had a few intentional quirks and handled well but had rather conventional behaviour especially at the stall.
    The updated version which I will call "Version B" incorporates some changes gained from experiments with the Thunderbolt and is much less stable and has some strange stall characteristics which seem to logically match some of the characteristics of the Airacobra.
    There are some maneuvers I still cannot reproduce such as the infamous "Tumble".
    There are some handling characteristics such as the very sensitive elevators that I have chosen to ignore in order to make the models more easily flyable in the simulator and I suspect that might also be preventing the Tumble.

    Along with edits to the AIR file, there have been some minor edits to the model.
    In this screenshot, the narrowed interior frame of the canopy can be seen.
    It was modified so that the Virtual Cockpit view would have smaller obstructions.

    - Ivan.
    Attached Thumbnails Attached Thumbnails P39DEJ_AfterTestFlight.jpg  

  2. #27

    Minor Change in Plans

    My original plan was to change nothing as far as textures and mapping that was not directly related to model changes.
    The main reason was to be able to use existing texture sets on the new model with minimal modifications.
    The second reason was to limit the changes because as with any model that we did not design, there are an endless list of things that can be "improved".
    The third reason is that I simply hate texture mapping and working on new textures.

    There are, however, certain things I just can't tolerate and I came across such a situation.
    Different parts should not map to the same areas of the same texture files.
    When this is done, it becomes impossible to paint one piece with a unique marking without affecting the other pieces which share the same texture; If I paint one wing tip red, I don't want to see a red pattern appear on the tail or some other piece of the aeroplane.

    In this case, the Landing Gear covers mapped to the same areas.
    With the standard Army Air Corps paint schemes, the underside is mostly a single colour, so it is not an obvious problem.
    Stripes and certain camouflage pattern simply could not be done.
    The texture remapping was completed earlier today and I also finished applying a texture to the last piece that I believe needed one: the Control Panel.

    The screenshot shows the new Control Panel. There is no point showing the Landing Gear because the appearance has not changed.

    - Ivan.
    Attached Thumbnails Attached Thumbnails Airacobra_Instruments.jpg  

  3. #28

    Interior Canopy Frame

    One of the pieces that needs to be added via SCASM is the interior of the Canopy Frame.
    The process I use is to first build it as a single AF99 Component and texture it with an interior colour.
    When it is textured, it will still show all polygons on the outside as is typical with Components marked as "Smooth".
    After it is built, I disassemble with MdlDisAs into SCASM code and flip the polygons outside-in with a program I wrote a couple years ago.
    This process seems to work most of the time but in the past I have had some very strange blow ups.
    These days, I am tending to believe that the blow ups were a result of my malfunctioning Development Computer before it finally died.

    Attached are screenshots showing the appearance at each stage.
    The Reversed "Outside-In" model is quite odd to flip around in the simulator.

    - Ivan.
    Attached Thumbnails Attached Thumbnails CFrame_Isolated.jpg   CFrame_Flipped.jpg   CFrane_Inside.jpg  

  4. #29

    Airacobra Instrument Panel

    Hello All,

    The Virtual Cockpit and SCASM edits were done not long after the prior post.
    I had not realised that I didn't post any screenshots.

    The first attached image show what an actual cockpit view from the Airacobra looks like.
    To maintain the aspect ratio of the CFS panel, the last two rows of gauges could not be included.

    The second image is a screenshot of my new Airacobra Panel background with gauges.
    Note that the arrangement of gauges in the CFS panel is only meant to give an impression of the actual instrument panel.
    In the actual aircraft, the instrument panel is very narrow but very high and there are controls tucked into various corners of the cockpit. (The Starter is a pedal on the cockpit floor.) There are also instruments that have no equivalent. (Gauges for the propeller reduction gear, etc.)

    The center panel is mostly correct with the exception that the compass is replaced by a clock. There is no point in having both a Compass and a Directional Gyro in CFS.
    The right panel contains engine gauges as on the actual aircraft.
    The left panel is an assortment of gauges that have no other place.

    Improved versions of some gauges are already in the works and I can see quite a few places where the background can be improved.

    - Ivan.
    Attached Thumbnails Attached Thumbnails P-39Cockpit.jpg   Airacobra_Panel.jpg  

  5. #30

    New Gauges for Airacobra

    Some folks may have noticed that in the last panel screenshot that the Trim Gauge looked a bit odd.
    It resembles the stock SP.Trim Gauge in appearance and general function but is actually a replacement that I programmed a few years back. I wanted a gauge that was a bit easier to read and in which the markings actually had some meaning.
    In the replacement version, the tick marks each represent 10 notches of trim.

    The first gauge I chose to replace specifically for this project was the Fuel Selector.
    The appearance of the actual P-39 Airacobra Fuel Selector is shown in the first attached image.
    Note that it has 5 positions.
    The selector is currently set at the "Reserve" Tank. Going Counter Clockwise, we have
    Right Main Tank
    Left Main Tank
    Off
    Auxiliary Tank (Drop Tank)
    Reserve Tank

    The P-39 had two internal fuel tanks of 60 US Gallons (at most) with one installed in each inner wing section for a total of 120 Gallons. Some models had even smaller fuel tanks (notably the P-39N) for a total of only 87 Gallons.
    The "Reserve" tank was actually just a standpipe reserve and part of the Left Wing Tank.
    In other words, selecting "Left Main" would draw only the top 40 Gallons of Fuel and leave the last 20 Gallons as "Reserve".
    Selecting "Reserve" would draw from the Left Wing Tank until it was empty.

    Although it is possible to implement this in CFS (I believe), I chose to implement the simpler case of just simple Left and Right Main Tanks. Getting too complicated on the first try is generally not a great idea.
    The problem is that there are no stock Fuel Selectors that only have Left and Right Tanks, so I programmed one based in general appearance on the stock P51D Fuel Selector but without the Center Tank.

    The second image shows the new gauge installed in the panel.

    The gauge is done as a FS98 Gauge to avoid the Multi Gauge complications and because there isn't an obvious second gauge I should combine with it. Unfortunately it requires the Render3D setting to be off in order to work.
    I believe there will need to be an updated version as a FS2000 / CFS style Multi Gauge to allow access to Fuel Tanks that are not visible in the FS98 SDK.

    I also made a change to the tick marks on the Trim Gauge but it seems to me that the original version was better.

    - Ivan.
    Attached Thumbnails Attached Thumbnails FuelSelector.jpg   AiracobraPanel2.jpg  

  6. #31
    Hi Ivan, I am curious to know if your plane will also have a VC with working gauges.

    Regards,

    Erik Hertzberger (hertzie).

  7. #32
    Hello Hertzie,

    First of all, I can't really call this "MY" Plane. It is still Eric Johnson's P-39 though of course the modifications are mine.

    I have never really been interested in getting working gauges in a Virtual Cockpit. I don't see the reward as being worth the effort.
    If I were to actually try putting working gauges into the VC, I would start off with a better model or at least one that I owned.
    As I stated a few times before, this particular project has so many things wrong with it that can't really be cured without a total rebuild and since it didn't start as my project, I am not inclined to spend the kind of effort needed to put things right.

    I am basically using this project to aid in development for my own version of the Airacobra.

    My Apologies.
    - Ivan.

  8. #33
    Hello All,

    I had intended to create a new Fuel Gauge before releasing this project but am finding that creating the bitmaps for the gauge is taking much longer than I had expected. The bitmaps are not really that complicated but they do tend to be tedious.
    I do intend to complete the fuel gauge at some point, but improvement would be one of appearance rather than functionality.

    The project was uploading this evening and hopefully will be available soon.
    Let me know what you think of the results of this rather long diversion of a project.

    - Ivan.
    Attached Thumbnails Attached Thumbnails FlightLine.jpg  

  9. #34
    The new aeroplane was approved very early this morning (about 2.5 hours after upload) and can be found here:
    http://www.sim-outhouse.com/sohforum...9&linkid=25234

    I should have added this to the description:
    The markings are intended as a tribute to Number 74 "Nanette" flown by Edwards Park in New Guinea.
    The exact markings are not well documented so they are done in the typical style of aircraft in that theatre and are a guess.

    "Nanette: Her Pilot's Love Story" was a book written as "an exaggeration" by Mr. Park and published in 1977.
    It was quite a good book which I remember reading when I was young.

    - Ivan.
    Attached Thumbnails Attached Thumbnails NanetteBook.jpg   Nanette1.jpg  

  10. #35

    Minor Update

    Project has been updated with a CFS Style Multi Gauge Fuel Selector to improve Cockpit Interior View.
    It seems a bit silly to have a single gauge inside a Multi Gauge package but that is how CFS / FS 2000 does things.

    This should eliminate the black bar at the bottom of some of the interior views.

    - Ivan.

  11. #36

    Center of Gravity

    Even though the Airacobra was released a few months ago, I was never quite satisfied with how things turned out.
    It seemed that the aircraft didn't handle quite as well as it should have. For a while I was trying to find the cause.
    I don't know for sure that I have found the actual problem but a very slight modification to the Center of Gravity seems to have improved the handling much more than I expected.

    Time for some more testing and fine tuning.

    - Ivan.
    Attached Thumbnails Attached Thumbnails Nanette_TestFlying.jpg   Nanette_LowPass.jpg   Nanette_TestingFinished.jpg  

  12. #37

    P-39dej_052

    After a couple months of testing, fine tuning, and other projects, the updated version of Eric Johnson's Airacobra was just uploaded.
    The most significant change was a 1 inch shift of the Airframe CoG Aft and this appears to have fixed most of the handling problems.
    Visual model was not updated for the CoG shift.

    The Airacobra now behaves fairly well when fully loaded and is quite agile.
    It should be flown smoothly without abrupt control movements and speed should be kept as high as possible.
    When the ammunition is expended, stability is very poor and stalls are to be avoided.

    It is actually very easy to land as long as one remembers that the Airacobra is a heavy aeroplane and falls out of the sky at about 95 MPH and gets directionally unstable at the stall. Keep a little margin of speed!

    - Ivan.
    Attached Thumbnails Attached Thumbnails FlyPast.jpg  

  13. #38

    P-39dej_053

    Up to this point, I had been mostly concerned with Flight Performance and never really looked very hard at the Damage Profile except where it might affect performance.
    Recently, a slight diversion with the P-39C version of the Airacobra called my attention to how BAD the current DP file was for the P-39D.
    The differences between the C and D models was a bit less armament and a LOT less armour. The armament was pretty easy to change but when I started editing the Damage values to address the lack of armour, I found that pretty much none of the pieces in the damage boxes actually lined up with where the parts were in the real aircraft. The existing DP also made the Airacobra a much tougher aircraft than it should have been.

    From what I can tell now, the DP file was a modified copy of the stock FW 190A which was an amazingly tough and compact little fighter.
    One of the side effects of this origin was that it didn't have a coolant radiator / reservoir even though the Airacobra has a liquid cooled engine.

    From a weight and performance standpoint, nothing has changed. Folks who choose to fly it in combat will notice that the 37 mm cannon now hits harder as it should considering the shell is over a pound and a quarter in weight and the wing guns are better harmonized (330 Yards), and of course that the pieces now match their actual location inside the aeroplane.

    The existing library entry has been updated.

    - Ivan.

  14. #39
    One of the reasons I chose to remap as few textures as possible when reworking this model from the original was so that it could host other paint schemes that had been developed for the original model by Eric Johnson. That this can be done VERY easily has been shown by the adaptation of the paint scheme used for the P-39CEJ that was recently uploaded.
    Another very nice paint scheme which I may try to adapt may be found in the download section here:

    http://www.sim-outhouse.com/sohforum...id=19&id=13835

    I believe the original artist may be arfyhun. I found this morning that I already had the package on my Development Computer but had just never installed it. Attached is a screenshot from the simulator of the installed aeroplane.

    From the download description, the two models of Airacobra which wore these markings were a P-39D and P-39N. Interestingly, the download is labeled P-39F. The model however is a P-39Q with underwing gun pods which were never installed in either the D or the N model Airacobra. Except for the lack of a fin fillet, my updated model would make a much better canvas though I would also take some liberties in applying the paint job. The current flight model is also a much better match than the one from the package which is much too agile for an Airacobra. Its roll rate would be competitive with an Pitts Special and certainly leave either a P-40 or a FW 190 behind.

    - Ivan.
    Attached Thumbnails Attached Thumbnails AirACutie.jpg  

  15. #40

    Cute Can of Worms

    In poking around with the "Air A Cutie", I came across a few more problems than I had expected.
    First of all, although there was a comment that there were paintings on BOTH sides of the fuselage, the CFS model only has an image on one side; the starboard side is blank.
    In a quick search for photographs of the starboard side of Air A Cutie (The two paintings are not the same), I found that the general consensus among model builders (The ultimate rivet-counters) was that "Air A Cutie" wasn't actually a P-39D-1 but was a P-400 or a British contract Airacobra Mk.I that was taken over by the US Army and used in New Guinea.... Also by 8 FG, 36 FS in 1943. Perhaps there was a THIRD aircraft that wasn't mentioned in the download? Serial number was AP287.

    Attached is an image from a modelling guide.

    If this aircraft really was a P-400 armed with a Hispano 20mm cannon instead of the 37mm, then the visual model should have a long skinny barrel sticking out of the spinner instead of the short little 37mm blast tube.
    Perhaps this would be a good opportunity to replace the cannon barrel with the 20mm version via SCASM?

    - Ivan.
    Attached Thumbnails Attached Thumbnails Air-A-Cutie.jpg  

  16. #41
    Here's some pics of "Air-A-Cutie" showing both sides : She was a P- 400 as can be seen by the long 20 mm cannon barrel. Joke in the SW Pacific was Q: " What's a P -400 ? " A: " A P-40 with a Zero on its tail "


    Attached Thumbnails Attached Thumbnails airacutie12.jpg  

  17. #42
    Hello Sopwith Chameleon,

    Thanks for the photographs. It is pretty clear from your photographs and perhaps others I found that at least one of the Air A Cutie had a 20mm cannon. There is actually quite a bit of disagreement as to whether it was a P-39D-1 or a P-400. The dispute appears to be due to some detail differences in the various models of Airacobra that are in the photographs.

    The exhaust 6 stack versus 12 stack is one recognition feature but may have resulted from an engine replacement in the field. The mechanics were known for scavenging pieces from unserviceable aircraft to maintain others.
    There apparently was also a flare port that was standard on a P-400 that was not present on Air A Cutie in photographs that would suggest that it really was a P-39D.
    The 20mm cannon is also not a good indication because sometimes the 37mm was swapped out in the field for a HS-404 from damaged P-400 aircraft. From discussions with a Airacobra owner, the ejection ports are larger for a 37mm gun but that would not stop installation of the 20mm.

    As for markings, there is a theory that the same aircraft had updates to national insignia and had the wing leading edges and tail surfaces painted white later in its life.

    There is also the possibility that there is a FOURTH Air A Cutie which was a P-39Q-6 Photo Recon bird (S/N 42-20013) which was a conversion from a standard Q-5.

    My own belief is that at most there were two Air A Cutie. This was an awfully elaborate paint scheme to apply and I can't see anyone doing it on four different aircraft.

    Looks like there is a lot of room for artistic license. My issue with this paint scheme is that the texture mapping on this bird isn't square in most places and to get things to look good takes more effort than usual. Also I found that the resolution of the images needs to be pretty small to fit onto the aeroplane and detail in a lot of places is lost.

    - Ivan.

  18. #43

    Air A Cutie - First Try

    This is my first attempt at a custom paint scheme on Eric Johnson's Airacobra.
    It will also probably be my last.
    The textures are mapped so inconsistently that it takes two or three times the effort to get things to line up so they look "OK".
    As mentioned before, the vertical to horizontal scale isn't the same and what is worse is when a large image such as the nekkid chicks crosses pieces with different scaling.

    This one is almost done and just needs a few simple items and lettering added.....
    The 20mm Hispano is on order but delivery time is unknown.

    British aircraft would also have had a bit less performance because of the mandated snow filters but I doubt those would have been left in place in US Army aircraft operating from New Guinea, so there probably was no significant difference in the engines.

    Although the 20mm cannon weighed a LOT less than the 37mm gun, from what I can tell, the aircraft equipped with it were actually heavier.
    In checking the differences in equipment, apparently the CoG change from the cannon was balanced by additional nose armour pieces and relocation of the oxygen bottles. I don't know if a P-400 in US service would have been exactly the same as the Airacobra Mk.I in RAF service though as far as oxygen equipment.
    There are also some differences in ammunition weight but the weight of the cannon ammunition was not the big problem in the Airacobra.
    The weight of the ammunition for the .50 cal cowl MG made the most difference.

    - Ivan.
    Attached Thumbnails Attached Thumbnails Airacutie_Port.jpg   Airacutie_Starboard.jpg  

  19. #44

    Air A Cutie Completed

    The remaining texturing for Air A Cutie was completed yesterday afternoon.
    Things are not too bad when one remembers in advance that there is some wacky scaling to be addressed.
    The AIR file was updated last night. There are no real changes other than the description of armament.
    The 20mm Cannon was assembled using a leftover P-39D airframe to check mounting issues and then removed (copied via SCASM) and then installed in place of the 37mm.

    I have been told that the mounting cradle for the cannon are pretty different between the two cannon.
    The design for the cannon was based on box art from a Monogram 1:48 model of the P-39 (Z-28).

    All that really remains is to gather a few screenshots and to think of something clever to write in the ReadMe file.

    One interesting observation is that the duration of the ammunition supply is much shorter for the Hispano Mk.I / HS-404 gun.
    The 37mm M4 had 30 rounds and a firing rate of 150 rounds per minute which meant that ammunition lasted for 12 seconds.
    The 20mm Hispano had 60 rounds but also had a firing rate of 600 rounds per minute which meant that ammunition is gone in 6 seconds.
    The French version of the HS-404 had an even higher firing rate of 700 rounds per minute.
    There wasn't an easy way of increasing the ammunition capacity because these Hispano guns were fed by a drum.

    - Ivan.
    Attached Thumbnails Attached Thumbnails Airacutie_Left.jpg   Airacutie_Right.jpg   LandingBounce.jpg  

  20. #45

    Air A Cutie uploaded

    Air A Cutie was uploaded last night and approved this morning.
    It can be found here:

    http://www.sim-outhouse.com/sohforum...9&linkid=26680

    Have fun, Folks!

    - Ivan.

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