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Author Topic: [Released] F-117A Nighthawk  (Read 45832 times)

Levi

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[Released] F-117A Nighthawk
« on: January 24, 2015, 07:41:46 am »

Wikipedia: The Lockheed F-117 Nighthawk is a single-seat, twin-engine stealth ground-attack aircraft formerly operated by the United States Air Force (USAF) developed from the Have Blue technology demonstrator and produced by Lockheed's Skunk Works. It is the first operational aircraft to be designed around stealth technology.

Download v1.01
(March 28, 2015)
This is an unofficial conversion for the F-117A Nighthawk from AlphaSim/Virtavia. The conversion is done with Phil Perrott's Permission at virtavia.com.


Version 1.01 (March 28, 2015)
  • Updated lights to work with Outerra Version 0.8.4.5372 and newer
  • Added a few more constants at the top of the script to turn certain group of lights on and off
  • Added lag filter to flight control surfaces and to nose gear steering
  • Added camera motion effects when the aircraft is on ground
  • Script optimizations (from 1759 to 1286 lines)

Version 1.0 released on February 24, 2015

Warning: To avoid instrument vanishing, make sure you have min_obj_size in eng.cfg set to 1.0 or less.

Notes:
- The code that display digits on the panels is an improved version of Uriah's code (thank you for providing it). It's now shorter and much easier to add new numbers.
- New and better technique for making complex animations, such as the landing gear retraction, using axis integrators.
- Most of cockpit stuff such as buttons, switches, etc are completely remodeled, and other parts have been corrected and optimized.
- Number of textures have been drastically reduced from about 260, down to 28 (without gauges, which are 25 textures).

Some features:
- Four versions:
    Black                  | Carries two GBU-10 bombs.
    Camo                  | Carries two GBU-31 bombs.
    Grey                   | Carries two GBU-10 bombs.
    StarsAndStripes    | No weapons.

- Up to eight different camera positions (use 'V' key).
- Avionics:
    Altimeter.
    Radar Altimeter + red light on, when altitude above ground level is below 100 ft.
    RMI (Radio Magnetic Indicator).
    Drift Angle Indicator.
    Angle of attack (AoA) Indicator.
    GForce Indicator.
    Airspeed Indicator.
    Vertical Speed Indicator.
    Left MFD display - ADI data:
        Heading rose + digits.
    Right MFD display - ENG data:
        Throttle position.
        N1% (left & right engine) displayed in digits and bars.
        N2% (left & right engine) displayed in digits and bars.
    Engine panel:
        N1% (left & right engine) displayed in digits.
        N2% (left & right engine) displayed in digits.
    Fuel quantity panel:
        Total fuel displayed with a needle + digits.
        Left & Right tank displayed in digits (This needs some changes though. There are 3 tanks in FDM, but the digits only shows the content in the left tank)

- Lighting System:
  Note: You can turn most of the lights Off by editing the script (ALT+E). The Control panel for lights is located at the top of the script.
    Exterior:
        Landing & Taxi Lights | Turned on only when gears are extended.
        Rotary Beacon Light   | Turned on only when gears are extended.
        Navigation Lights.
    Cockpit:
        Nav GPS blue light on.
        Ambient green light.
        Instrumentation/panels/gauges lights.
        Canopy light.
        Landing gear position lights | each light corresponds to the actual gear position.
        Warning lights based on AoA and Overspeed(more than 536.177 knots).
        Chute deployment && Jett. lights.

- Fully animated Landing Gear (locked when the aircraft is on the ground).
- The maximum steering angle on the nose gear changes dynamically based on the aircraft's velocity.
    This allows you to make sharp turns (87 degrees) at low speeds (very useful when taxiing).
    At high speeds, this allows you to make precise corrections when taking off/landing, due to the limited steering angle.

- Animated Flight Control Surfaces.
- Animated Cowl Flaps (closed at speeds above 40 knots).
- Extendable weapon racks (use 'FLAPS' key).
- Working Drag Chute | FDM + deploy and wind (a fake and random one) animation. It deploys when all wheels on ground, throttle <= 10% and speed >= 50 knots.
- Animated Cockpit Controls:
    Yoke.
    Rudder Pedals.
    Throttle lever.
    Gears lever.
- Extendable Tailhook (waiting for extended keyboard functionality).
- Animated canopy + it's handle + shade flaps (opens when the speed is less than 0.5 knots, and brakes are applied.)
- Sounds:
    5 samples for each engine (when outside the cockpit).
    4 samples for each engine (when inside the cockpit).
    Canopy.
    Cockpit electrical[?].
    Stall.
    Overspeed.
    Gears (retract/extend).
    Touch & Roll | a sound event for each wheel.


Release Video:


Screenshots


« Last Edit: March 28, 2015, 06:47:42 am by Levi »
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konaone

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Re: [WIP] F-117A Nighthawk
« Reply #1 on: January 24, 2015, 11:15:39 am »

 8) 8) 8) 8) 8) 8) 8) :)mythical, great job!!
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ZeosPantera

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Re: [WIP] F-117A Nighthawk
« Reply #2 on: January 24, 2015, 12:12:39 pm »

Now I have to learn to fly again. Damn you.
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PytonPago

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Re: [WIP] F-117A Nighthawk
« Reply #3 on: January 24, 2015, 12:16:14 pm »

Now I have to learn to fly again. Damn you.

 ... why again ?  =D

 ... Great model indeed. The cockpit is gorgeous, hope those panels will have some magic later going on !
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We are still undeveloped as long as we don´t realize, that all our science is still descriptive, and than beyond that description lies a whole new world we just haven´t even started to fully understand.

ZeosPantera

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Re: [WIP] F-117A Nighthawk
« Reply #4 on: January 24, 2015, 01:11:44 pm »

Because I haven't flight sim'd in many years. Last thing I was doing was trying to learn the Apache in OT over a year ago (maybe two).. I may need a better joystick if I am actually going to get into it.
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PytonPago

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Re: [WIP] F-117A Nighthawk
« Reply #5 on: January 24, 2015, 01:28:21 pm »

Because I haven't flight sim'd in many years. Last thing I was doing was trying to learn the Apache in OT over a year ago (maybe two).. I may need a better joystick if I am actually going to get into it.

   ... or get a hold of a de-commisioned fighter jet cockpit. ( thats my dream  ::) )
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We are still undeveloped as long as we don´t realize, that all our science is still descriptive, and than beyond that description lies a whole new world we just haven´t even started to fully understand.

Uriah

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Re: [WIP] F-117A Nighthawk
« Reply #6 on: January 24, 2015, 09:45:32 pm »

I would really like to see more realistic "fighter jet" FDM. The Mig29 is simply far too easy to fly, and I get the feeling of a more game-like experience than sim. By this I mean, in a game an aircraft seems to magically go wherever you want along a perfect flight path, and performs maneuvers that are impossible in the real-world.

The F-117 uses what is called Relaxed Static Stability (RSS), because aerodynamically it is extremely unstable.

http://en.wikipedia.org/wiki/Relaxed_stability

"An aircraft with a "low" wing (i.e., underneath the fuselage) has less roll stability."

As you can see, the F-117 has a low set delta wing, making it unstable in pitch and roll, especially at low Reynolds numbers. I believe JSBSim accounts for stability, and it shouldn't be too difficult to accurately model the pitch and roll instability, and increase it at low speeds. Also the lift coefficient of the F-117 surfaces is dampened by the angular shapes, therefore lift instability will make the aircraft wobbly during landing and take off. Much of this is handled by the fly by wire system in-between the flight controls and the control surfaces. But if you read about pilot accounts of flying the aircraft, they all talk about how different it was to fly than other similar aircraft that came before or after the Nighthawk. You of course won't be able to create a real FDM for it, but I thought that intentional instability could be accounted for in the FDM. This would be a good question for the JSBSim dev mailing list, maybe someone has already developed this.

I'll try to find out a little more about the F-117 lift coeff. and stability pitch roll rates/moments.

Also, since JSB calculates precise numbers, and the real world is full of variation, flying aircraft feels like you are moving along a perfect line.

It would be amazing if you could add "noise" to the lift force of the aerodynamic surfaces and drag, to simulate unsteady flow and pressure which induces slight variations to lift and drag. JSBSim already has this functionality, it just needs to be added into the aircraft.xml FDM file, to add noise to the lift/drag variables by a percentage of the original value. I found this while working on rocket engines. A solid rocket motor propellant has variance in the thrust based on the Isp (Specific Impulse) defined in the example below. I am certain <VARIATION>FILL-IN-THE-BLANK</VARIATION> can be applied to any JSB force or variable based on what I have read. So it just needs to be added to the aerodynamics section and tuned to produce slight variations in the lift and drag, and could also modify the aerodynamic center position slightly along the Y axis to simulate aerodynamic pressure variance.

Note: You can use the CSV flight data output to measure the variance and compare it to the same FDM without the variation. I think with a more advanced method than <VARIATION> you could specify the frequency of the variation, or use a JSB filter to smooth the variation output, (FGFilter). I am able to implement a JavaScript Second-order Kalman Filter by the way, it is better than the JSB filter.

I implemented a script for rockets which decreases the sound as the atmospheric pressure decreases. By the time you get up to 90,000 ft ASL no sound can travel in the near-vacuum. This gave me the idea to play a sound loop of air turbulence inside the cockpit of an aircraft, so when you go into a turn (high AOA), or accelerate to a high speed, the air turbulence sound "gain" or "distance" is increased. All you need is to devise a simple formula which takes into account both angle of attack and speed, which can be called from jsb['variables']. I included my Decrease Sound With Altitude Script below. It works flawlessly! All you need is a clean audio file for the turbulence and a formula for calculating snd gain/distance by AOA/velocity. This would be so simple to do, and the result should be really dynamic and realistic! Happy to produce the audio loop if you need me to.

Regards,
Uriah

Solid Rocket Motor Thrust Variation example: ./engines/SRB.xml

Code: [Select]
<isp> 268 </isp>
  <builduptime> 0.2 </builduptime>
  <variation>
    <thrust>0.02</thrust>
    <total_isp>0.00</total_isp>
  </variation>

Decrease Sound With Altitude example: ./scripts/aircraft.js

Code: [Select]
val = (jsb['atmosphere/P-psf']);
if (val > 0.1){
snd.set_ref_distance(engine_sound_src, (0.1*jsb['atmosphere/P-psf']));
}

else{
snd.set_ref_distance(engine_sound_src, 0.0);
snd.stop(engine_loop_snd);
snd.set_gain(engine_loop_snd, 0.0);
}
« Last Edit: January 24, 2015, 09:55:32 pm by Uriah509 »
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KW71

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Re: [WIP] F-117A Nighthawk
« Reply #7 on: January 25, 2015, 02:39:41 am »

Thanks, Levi! I can't wait to try it!!! Download link?
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PytonPago

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Re: [WIP] F-117A Nighthawk
« Reply #8 on: January 25, 2015, 03:35:51 am »

Yes, the mig-29 is a arcade-like thingy now. Its well seen when ya try to take off in great angles of attack. Lift-weight ratio is wrong or feels too smooth.

 .. those bombers are pretty much flight-incapable without the fly-by wire, but i know the su-27 is also a pretty unstable thing whiteout it ( this one was a failure in the FbW as i remember right ):

« Last Edit: January 25, 2015, 05:18:20 am by PytonPago »
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We are still undeveloped as long as we don´t realize, that all our science is still descriptive, and than beyond that description lies a whole new world we just haven´t even started to fully understand.

Levi

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Re: [WIP] F-117A Nighthawk
« Reply #9 on: January 25, 2015, 03:49:46 am »

Now I have to learn to fly again. Damn you.
... Great model indeed. The cockpit is gorgeous, hope those panels will have some magic later going on !
Yep, I definitely plan to add some magic to those displays. ;D

Thanks, Levi! I can't wait to try it!!! Download link?
The progress is very slow on this one, so I can't really say when will be released.

It seems that the FDM will be a challenge this time.

That <VARIATION> thingy sounds very interesting, I'll definitely have to do some testing with that later on.

The air turbulence sound should be relatively easy to do, though, I think I'll need an audio loop. If you look at the ASK-13 you'll see that I already kinda implemented this, but instead of a turbulence sound, a creak sound and the vario beep, but those are only based on the AoA.

Thank you for all that information Uriah!

Edit: @PytonPago Poor B-2 :( =|
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adler58

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Re: [WIP] F-117A Nighthawk
« Reply #10 on: January 27, 2015, 06:09:40 pm »

A very challenging model, but I'm sure Levi will put it through in an oustanding way :)
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bomber

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Re: [WIP] F-117A Nighthawk
« Reply #11 on: January 28, 2015, 03:36:08 pm »

Flight modelling.......  Where do I start?

First off its shades of grey, it can be either arcade or not...

The question is what standard are we aiming for here at outerra?

If it's arcade, then nick the very best from FlightGear... If that seems harsh, well there's a standing challenge I've laid down there for anyone t to come forward with a flight model that they think is  5 star and I'll challenge it...

But what's important for us here is can we leverage the best in jsbsim to match the wonderful graphics of the outerra world... ?

My suggestion is to forget flight modelling,  i got it covered.... The ask13 is 2 years worth of development, and since the new year is had another rewrite...

But just so you know I hate the above sentence,  because the "don't question me as I've spent x number of years on this" is something I hate...  But in not saying that I'm just asking for time to complete the aerodynamics is as correct as jsbsim can possibly do....  no magic numbers or un-challengable bits of physics code....

...

Oh and I still need some help on writing c++ for the piston engine


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PytonPago

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Re: [WIP] F-117A Nighthawk
« Reply #12 on: January 29, 2015, 02:07:44 am »

Flight modelling.......  Where do I start?

First off its shades of grey, it can be either arcade or not...

The question is what standard are we aiming for here at outerra?

If it's arcade, then nick the very best from FlightGear... If that seems harsh, well there's a standing challenge I've laid down there for anyone t to come forward with a flight model that they think is  5 star and I'll challenge it...

But what's important for us here is can we leverage the best in jsbsim to match the wonderful graphics of the outerra world... ?

My suggestion is to forget flight modelling,  i got it covered.... The ask13 is 2 years worth of development, and since the new year is had another rewrite...

But just so you know I hate the above sentence,  because the "don't question me as I've spent x number of years on this" is something I hate...  But in not saying that I'm just asking for time to complete the aerodynamics is as correct as jsbsim can possibly do....  no magic numbers or un-challengable bits of physics code....

...

Oh and I still need some help on writing c++ for the piston engine


There will be a lot of re-writes ... at all stuff.

   I mentioned quite some time back, that each step humans take in knowledge and science, the potential still "hidden" from us, when looked upon it by the latest state of knowledge, is growing. Looks like the reality was constructed a way in witch there is no visible end in stuff to see and know. BUT, that means not, that its impossible to finish something - it means, that even people after us will have the chance to add some piece of great work into the collection and that the thing in development (or science) is thereby allays in the best, that people, at that time working on it, can muster to their individual limits. ( well, if the free-time for it would get better, it would be probably a too good story. Ankers always have to be hidden somewhere too.  =D )

   ... just like an motivational thought. :)
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We are still undeveloped as long as we don´t realize, that all our science is still descriptive, and than beyond that description lies a whole new world we just haven´t even started to fully understand.

Levi

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Re: [WIP] F-117A Nighthawk
« Reply #13 on: February 10, 2015, 06:48:09 am »

Testing the lighting system:
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bongodriver

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Re: [WIP] F-117A Nighthawk
« Reply #14 on: February 10, 2015, 07:30:57 am »

Looks good, my only critique is that military navigation lights (red/green wingtip lights) don't flash like strobes but instead just alternate on-off, but most of the time navigation lights should be steady.
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