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
    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.


    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:

    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


    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  

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