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Supersonic the hedgehog

Spent the last few weeks tweaking the more esoteric parameters of the airfile, and finally came down with something that I believe I can live with. Still a little bouncy in pitch, but apart from that it flies more or less “on the numbers”. High Mach numbers are now easiest to achieve at around 10 km altitude, and the effective ceiling is somewhere around 15 to 16 km.

Did some aerobatics today at low altitude, staying below 700 kmh all the time on full throttle. Pulling a few G:s will keep alpha up and speed down, as it should. Flies like a dream in my opinion. Roll damping has been adjusted to get a snappier roll, as the real thing could actually do a full roll in 2 seconds. If you liked the somewhat sluggish response of the previous versions you might not feel at home with the new FDE, but this is actually more realistic. I think.

Put the afterburner back in the mix today and started tweaking the afterburner thrust curve and the high Mach drag values. I have been using the NASA EngineSim applet as a starting point, then recalculating those results on the data I have from Rolls-Royce and Volvo for the RM6C engine with the EBK67 afterburner. Feels OK, although I suspect that wet thrust might now be a little too high. Will try to check this with some Draken pilots. Peaks at M 1.75 with bingo fuel at 10 km altitude, this should be more or less accurate according to the real flight manual.

A number of bugs related to the autopilot appeared during this testing round, probably because I have been pushing the limits a bit. Will work on these bugs the rest of the week, then start finishing up for a 4.1b2 release at the end of the month.

Stay tuned /Tom

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Almost there

The new FDE is now “almost finished” – which really means that we are now in the kingdom of Pareto and Murphy. The final stage of any project is inevitably where most of the work is being done, and where everything inevitably goes wrong. That said, I am actually optimistic about releasing 4.1b2 within the next few weeks.

The big difference between the previous (current) version of the Draken FDE and this attempt is that I am now starting with a blank sheet and some good books on aerodynamics, instead of just tweaking a stock FDE until it squeaks. The 4.0 FDE performs OK within, say, 75% of the envelope. The new version will hopefully be able to “touch the edges”.

I started by remodeling the engine, which now produces net dry thrust within 5% of the real thing all the way from the runway to the “coffin corner”. It also has the correct thrust-specific fuel consumption and a more linear throttle response. All based on the sparse documentation from Rolls-Royce, Volvo and Saab that I managed to find.

The next step was to rework the lift and drag parameters to achieve the correct airspeed, angle-of-attack, pitching moment, etc. during climb and cruise. A great help in this was that I finally found some actual airfoil data for Draken. At the moment I am working on stability and control derivatives, which turned out to be the trickiest part. I don’t have the real values, so it is basically a lot of maths, guesswork, and test flights.

Putting the final touches on the derivatives today, then adding the afterburner and starting on the supersonic parts.

/Tom

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What happened to 4.1?

What ever happened to the release of 4.1 proper? Or the second beta?

The first beta turned out to be riddled with bugs and performance problems – some discovered by me in the weeks following the upload, some duly reported by users. I planned to put out a second beta that took care of most of these bugs, but the issues with flight performance were very troubling and I decided to postpone the second beta while working on the FDE. There is, after all, no point in uploading another version which still does not fly properly.

This is basically the problem: A lot of the engine parameters were totally wrong in 3.x and 4.0 due to my misunderstanding a crucial part of the SDK documentation. To compensate for the erroneous engine params I had been tweaking the aerodynamics to a point where the curves were completely off the chart. I have spent the last month reworking this, starting from scratch and actually following instructions this time. The result is a completely new FDE which gives a more or less correct engine thrust at all altitudes. The next step is to rework the lift/drag parameters to also get the correct airspeed and angle of attack, which is what I am working on right now.

Apart from this I have added a lot more 3D details in the VC and made some changes to the sometimes quirky radios and nav systems. When I eventually upload the next version I will try to include a detailed change list. No promises as to when this will be though, I really want to get the FDE right first.

Stay tuned, /Tom

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Draken 4.1 beta 1 download

41b1

The first public beta version of Draken 4.1 can now be downloaded using the link at the bottom of this post. Reading the following information before downloading will probably save both you and me a lot of pain, so please do.

  • Please read the End User License Agreement (EULA) that is included in the installer, and make sure you understand it before completing installation. By installing the software, you are bound by the agreement. The EULA can also be found here.
  • The installer will overwrite any previously installed files relating to Draken in the Effects, Gauges, Sounds and Additional Scenery folders of FSX. If you have made any modifications to these files on your computer, please remember to make backups. To revert to a previous version, just run the installer for that version again.
  • The Flight Manual has not yet been updated to reflect the latest changes. However, it is still compulsory reading before asking me any questions of the “how to start the engine” kind.
  • The navaids in the included scenery (Barbro) are not always at their precise locations, although they are perfectly usable for navigation. They will be corrected in the final release.
  • A brief list of the changes made between 4.0 and 4.1b1 can be found in a previous post. There have been additional changes since then, and I will try to update the change list as soon as possible.
  • Feedback should preferably be sent to me using the contact form but if you already have the address you can also just email me the usual way.

Download link:    [wpdm_file id=2]

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Beta release imminent

Compiling and test driving before releasing the 4.1 beta. As always, problems that were not there during development have a tendency to surface when you are preparing a release. So, some minor fixes left to do before I put 4.1b1 up for download.

Added the missing radar hand control to the cockpit model today. It was not planned for 4.1 but I added it anyway, just for the hell of it. Not really useful as there is no radar targeting yet, but at least the handle is there, replacing the rather ugly 2D gauge.

handcontrol-added

The beta will be released this weekend. No kidding!

/Tom

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Change log for 4.1b1

A pre-release of version 4.1 of Draken for FSX will be available shortly. Here is a list of some of the changes made in this update:

Flight dynamics

  • Fuel consumption reduced – was almost twice of real TFSC
  • Improved engine response in lower throttle range
  • Lift and drag parameters corrected
  • Indicated speed calculation corrected – see previous posts
  • Fuel tank volumes corrected
  • Empty weight and MTOW corrected

Model and textures

  • Added missing details in LODs 20-150
  • Added LOD5 (untextured flats)
  • Remapped nose decals (larger size decals now possible in repaints)
  • Added 3D version of engine panel in VC
  • Added missing circuit breakers in VC
  • Added deicing emergency cutoff valve in VC
  • Reflective and refractive textures fixed (mirrors, switches, glass,etc.)
  • Lots of cosmetic changes to objects and textures

Systems and gauges

  • Afterburner functions rewritten from scratch
  • Drag chute function changed – added reset from panel
  • RAT function completely rewritten – now controlled by rpm, not throttle
  • MTR function changed – now reduces throttle in 2% steps
  • Cabin Pressure Difference gauge completely rewritten
  • Autopilot override function now triggers warning light
  • Automatic switch between Altitude Hold and Attitude Hold in transsonic fixed
  • Wheel brakes are now anti-lock as default
  • Missing and erroneous tool tips fixed
  • Lots of minor adjustments and cosmetic changes

Notes

Some of the problems that appear in multiplayer were addressed in this update, but not all of them. At the moment I only have one computer that can run FSX, so I have not been able to test MP locally. Most multiplayer issues will be solved in version 5.0.

If you have done repaints they may have to be modified to work with version 4.1 as there is some remapping of the exterior.

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Reboot

As you may have noticed, I have once again taken a long – and much needed – pause from all things Draken. Things have lately started rolling again though, so I am reopening the blog for what it’s worth. At the moment there is no timetable, I will just try to handle one thing at a time and see how they turn out.

Before my last break I was working on a number of issues and had already solved most of them, but was stuck on some (and still am). You can read more about them here.

NEW: I am currently working on a number of FSX Missions to accompany Draken: some basic tutorials on flying this beast, and a couple of intercept missions. Creating missions is new to me, and I am still learning. But great fun!  See screenshots below.

Version 4.1 is coming along fine with a great number of changes and bug fixes already applied (a change list will be published shortly). There may or may not be a preview release of 4.1 in November, but definitely a final release before the end of the year. Then on to the brand new 5.0 version. ;)

Stay tuned   /Tom

An-2
Matching speeds with an An-2 is… challenging.
Radar
Visual and radar contact with an F/A-18 in high speed intercept.
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Problems – October 2013

These are the major unsolved problems I am working on right now. They are related to both the final update of the FSX version (4.1) and to the planned P3D version (5.0).

Multiplayer

There are a number of problems with Draken in multiplayer, one of them being that animations and fx are not working from the other player’s POV. The reason behind this is that Draken contains custom animations and functions that are compiled into the model. These will not carry over into MP,  you only get the animations that are also present in the model you are flying. So other players flying Draken will see the custom animations, but not players in other types of aircraft. The only way around this is to rewire the custom animations to stock animations. I am working on this but it will take some time.

Another problem is that smaller parts of the model disappear as you move away, regardless of which LOD is currently active. This is due to the somewhat erratic LOD handling in MP, where the SmallPartRejectRadius entry in fsx.cfg takes precedence over the LOD:s. There are numerous posts on the Internet saying that this is deprecated since SP2, but this is not true. If the entry is missing from fsx.cfg in SP2/Acc, the parameter will default to 1.0 (pixels) according to the SDK – although in reality it seems to be more like 2.0. Setting the value to zero will render “everything” but you will also take a minor/major performance hit depending on your hardware, number of players, etc. My advice is to try values between 0.0 and 2.0 and find a good balance for your MP environment.

Afterburner

In Draken the afterburner is activated manually with a key command, but shut off automatically as soon as you move the throttle back. This is achieved by setting the afterburner_throttle_threshold entry in aircraft.cfg to >1.0. This unfortunately also means that the throttle setting will automatically go to the threshold value as you hit the A/B key, which in this case means full throttle.

I discovered that the reason for this is that afterburner_throttle_threshold is not simply a threshold value for triggering afterburners, it’s actually a scalar for the throttle tables in the airfile – but only when afterburners_available is set to a value greater than zero. For example, a value of 0.8 means that you will get maximum fuel flow (and N2) at 80% throttle position. Now a single-stage afterburner (afterburners_available = 1) will ignite at 99% throttle, regardless of the threshold value. With multiple-stage afterburners, the activation threshold is lower. I have not yet figured out exacly why and how these factors work together. But the gist of this is that you cannot separate afterburner from throttle position in FSX. In the real Draken you could adjust the throttle while on afterburner, which could be crucial in formation flying. In FSX this is not possible. With afterburner on, you are stuck with the threshold value. It took me years (!) to discover that this is a limitation in FSX itself.

Another problem is that in multiplayer, other players will not see your afterburner fx since they are tied to a custom function compiled into the model (see above). I therefore tried to rewrite the A/B logic using only the stock functions and animations. This turned out to be a major headache for me, as the criteria for A/B actuation are quite complex in Draken compared to (for instance) the stock F/A-18. I am still working on this but I doubt that I will ever get it completely right…

Radio frequency settings, etc.

People are often complaining (politely) about the fact that the radios in Draken are tied to local variables, which apparently poses a problem when using ATC or when flying in a VA environment such as VATSIM. Now, the radios were among the first gauges I developed for Draken, more than a decade ago, and they were designed for the single-player flying that I was doing at the time. I have since done some changes and simplified the radios so that they respond to FSX key commands, but there is still some work to do. My goal is to have most of the radio and avionics settings using standard variables. Working on this, too.

So, a lot to do, as always.  ;)

Stay tuned  /Tom

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Not dead yet

Hello again, whoever is listening.

Draken development has been low-priority for a while due to personal and family problems. But the agenda still holds, I am hellbent on moving my simulation of one of the most wonderful jet fighters ever into the the next-generation world of flight simulation. Pretentious? Maybe. But that’s me.

I have now finally moved from modeling in GMax to 3DS Max with the new 64-bit Prepar3D SDK. This means that I have a lot more freedom in modeling, and more powerful tools for texture mapping. Texturing is thus getting a radical overhaul, primarily to allow for higher resolution (and more flexible) repaints.

The virtual cockpit is also being almost completely redone, mainly because VR is getting to be a big thing in simulation games. Lockheed Martin are talking about Oculus Rift compatibility, and there are a lot of users already using different 3D solutions. So I realise the need to come up with a cockpit environment where you can actually move around in three dimensions and still have that “sense of immersion” .

Any screenshots? Not right now. I really need to shape up and get the new texture mapping done first. Then, maybe.

Please stay tuned,

/Tom

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Progress

work

Finally managed to export the complete 3d model from GMax into 3DS Max, which means that I can start to remodel and retexture my baby the way I always wanted to. Expect more detail, higher resolution textures, and a better overall experience.

Kudos to Tom Faulds, Manfred Jahn et al who made this possible. See this link for more info about the export script.

The new model (5.0) is developed concurrently with the final upgrade of the FSX version (4.1) which is still modeled in GMax.

The target platform for the new model is Prepar3D, although it will be FSX compatible. Repaints that you have made for the 4.x version will not be compatible with version 5.0 for obvious reasons.

Screenshots of the new model will be up as soon as I get some texturing done.