How X-Plane Works | Hacker News Reader

How X-Plane Works

x-plane.com

185 pointssusam59 comments

For the hackers around here: There is a plug-in by NASA called "XPlaneConnect", that allows you to control aircraft in X-Plane from code See here: https://github.com/nasa/XPlaneConnect

I've used it to write some Python code that mimics upset recovery procedures that we teach human pilots. It's quite fun putting an aircraft in a tricky position and then seeing your code recover it nicely to straight and level flight. (Or seeing your code roll it over and fly it into the ground if you got the math wrong :-))

I wrote a rudimentary autopilot in Go that used a Kalman filter to maintain straight and level flight. It was a fun exercise!

And I wrote one in Python to climb/turn as well! And to navigate to any of the built-in X-Plane navaids -

https://austinsnerdythings.com/2024/04/06/adding-track-follo...

and the first post in the series -

https://austinsnerdythings.com/2021/10/15/creating-an-autopi...

I did a similar thing in Kerbal Space Program using krpc (though less for human training and more for fun) - https://github.com/standaloneSA/krpc_state_machine/tree/mast...

At a startup I worked at, we had our adaptive control pilot software flying our drone designs in XPlane for testing and demo purposes.

The developer's blog is really cool, has lots of neat practical opengl insights and stuff https://hacksoflife.blogspot.com/

Great article! However the kick into MSFS imo isn’t necessary, as it appears to use blade theory and CFD just as well: https://news.ycombinator.com/item?id=32073528

The article doesn't mention MSFS. However, MSFS does not use blade element theory, but a unique system of "normalization". https://docs.flightsimulator.com/msfs2024/html/7_Samples_Tut...

CFD is only used in a couple of the dozens of aircraft in MSFS. It still uses the "normalization" process that feels a lot like stability derivatives.

It can give good results, but overall the system in MSFS is too complex with too many parameters to tweak, leading to nearly all aircraft modeled having quite innacurate flight characteristics anywhere outside the normal flight envelope.

> The article doesn't mention MSFS.

It does, in the last paragraph.

So, as I understand it, the wing is broken down in sections, each of which will use some tabulated lift and drag for that airfoil at the current velocity vector and dynamic pressure? That seems fine. But it doesn't talk about how it deals with the fuselage and how it calculates its lift/drag. Calculating pressure drag is complicated and depends on the details of the airflow around the fuselage, and there's intersection drag at the interfaces with the wings/empennage. A significant portion of the drag for piston airplanes is also the cooling drag of the air that's forced through the cowling and the engine baffles. Does anyone know to what extent this is taken into account?

I'm not knowledgeable enough to tell if there are answers there, but some of these questions might be addressed in the deep dive of the F-4 Phantom modelization.

https://developer.x-plane.com/2022/02/x-plane-12-flight-mode...

This is a good read

In my experience this also uses tabulated data or simplified equations based on some geometric parameters (such as the exposed surface area). For the purposes of simulating flight, ball park figures are sufficient to get a reasonably accurate representation of an aircraft's behaviour and stability in various flight conditions. The additional accuracy you get from fluid dynamics simulations is computationally expensive and usually only needed in aircraft design.

There was an ooooold DOS game called Flight Unlimited that correctly(-ish) modeled flaps, rudder, etc, and ran you through a flight school to teach barrel rolls, Immelmann turns, etc.

I've been looking for an Xbox/Console game that lets you fly and crash a plane, shoot things in a game-like context, not slide around in some space invaders bubble with laser turrets painted to look like missiles.

Flight Simulator misses the mark (I think) because it's not so game-y. All the fighter jet games I've tried miss the mark because their physics is way too arcadey. Any recommendations?

I remember Flight Unlimited. Besides what you mention I remember it having very impressive world graphics for its time.

What you are looking for seems fairly niche to me especially on console, the only game that comes to mind is Star Wars Squadrons.

On PC I'm sure the story is a bit different (but not being much of a gamer these days I may not be the best person to ask). It may be worth checking out MicroProse games. This is the legendary publisher of old, with the brand being passed on through various mergers and acquisitions and the current stewards do a remarkable job and publish quality titles. Tiny Combat Arena may be worth checking out as it fits your description somewhat (if you can get past its stylised graphics).

Appreciate it! I know it's kindof niche, but Tiny Combat Arenas description seems exactly on point, unfortunate that it's only on PC.

I never considered Star Wars Squadrons, all the reviews on console seriously dragged the game, and I don't have a lot of time (and I think their multiplayer is kindof dead by now), but it has been coming up at $8.99 when I was paying attention so I'll keep an eye out.

Thanks again!

Edit: look up screenshots from this one: https://en.m.wikipedia.org/wiki/Sid_Meier%27s_Ace_Patrol ...it was effectively a turn-based version of what I was talking about. https://www.mobygames.com/game/65565/sid-meiers-ace-patrol/s...

Looks like Austin found an editor to clean up his texts which otherwise end up super nerdy and way too long. This is excellent, readable, and punchy. Makes me consider getting X-Plane 12 even though I already have 11 (and MSFS 2020 and 2024).

ChatGPT

Just watched the trailer, are those in-game graphics or is that a specially rendered trailer? It looks very realistic.

Edit: in game graphics are pretty amazing https://youtu.be/Y35JsotTCNQ

Those are in-game. If you feel that was realistic, you should see what Microsoft Flight Simulator 2024 looks like[1].

[1]: https://www.youtube.com/watch?v=A4zEesJbKqE

Hmm several of those scenes look better in fs2020.

Also many comparisons were made in totally different lighting conditions and aren't comparable. Like some taken at dusk in one version and daytime in the other.

One thing that is noticeable to me is that they finally fixed the runways. In fs2020 they all look like they were built this morning, all pristine and saturated black. Anyone who flies for real knows that's very unrealistic :) Runways get very little maintenance and cleaning because they want to keep them open for traffic. The fs2024 look much more realistic.

Is FS 2024 low-poly or does flatter colors and bright lighting make it so?

It’s fresh and buggy, the LOD system seems to make some areas have much less detail than necessary, and fix is being worked on (it’s among a top 3 issues in issue tracker)

Yeah there seem to be lots and lots of bugs involving VR too and they're very slow to fix them. Some of the fixes have been delayed to the second sim update

So I hardly tried it yet myself. I'll just wait until it works properly. And I don't do flightsims without VR.

Yep, I take it as having purchased a Flight Simulator 2026 with a bonus of early access to the betas. It will be a great game when it's finished :).

Yeah and at least we have 2020 which is pretty good by now.

It was worse when 2020 first came out with so much stuff broken or missing (eg VR support). The only alternative I had then was X-Plane. Which is not bad but decidedly previous-gen in terms of visuals.

Ps I really wish FS2024 would implement X-Plane's ergonomic yoke option for VR. I really miss that one.

But the MS Flight Simulator is not available for Mac. X-Plane on the other side is available also for Mac, Linux, iOS and Android.

Sorry for the slightly off-topic question:

As a "kid" I loved Flight Simulator (this was 25+ years ago). If I wanted to get back into it today are there any recommendations what to use/get in terms of software and hardware today for a beginner?

I did briefly (1h or so) try Flight Simulator 2020 but I was missing a kind of tutorial path starting with an absolute beginner. I might misremember this though!

So: Any recommendations on software, hardware, tutorials? I'm not looking to become a pilot, just spend a few hours every week learning a bit and having fun.

FS2020 has some simple tutorial missions for taking off, landing, etc. Other than that there are loads of great YouTube channels such as Squirrel that walk you through things https://www.youtube.com/playlist?list=PLbphwhPw2JuvwwsD-H3xo...

As for hardware, I'd recommend at minimum a joystick of some kind if you don't have one.

And finally I'd give you a shameless plug for my app SmoothTrack which lets you fluidly control the game camera with small head movements - https://smoothtrack.app ;-)

I've been wondering about this myself. Being a Mac user, I haven't really had a chance to use recent versions of MSFS in a couple decades. But... like you, I spent a lot of time learning rudiments of flying and navigation from it about 25 years ago. Appallingly, on my first and only flying lesson over Los Angeles (c. 2002), I knew enough about the controls and instruments that the instructor thought I knew what I was doing, and allowed me to take off and land by myself. The landing bit didn't work out that great and required some major intervention at the last second... but, still here ;)

As a Mac user, your best bet is probably X-Plane. There's only a few short tutorials, but given your history you should have no issues :)

MSFS on the X Box Series S/X is incredible. It even supports joysticks. There’s just something about flying over cities you’ve been to and seeing them so realistically rendered. There are definitely some glitches, but overall it is a pretty amazing experience.

Same here! I got all the way back to the airport, lined up, but was too high and didn't know how to safely lose it. I knew better than to lower the nose, but was afraid to withdraw power and stall 50 feet AGL so I gave him the controls. The experience (of flying - out to Catalina and back) left me speechless. My brain was so overloaded from tasks, instruments and sensory input (there's a LOT of stuff in the sky in SoCal, not all of which is man-made or talking to ATC) I had nothing to say when we touched down. It was incredible and I wish I could do it again. But it's kinda unethical to keep paying for "introductory lessons".

Funny. Yea. Also came into Santa Monica way too high, even though I was lined up perfectly. I was in a war with myself between what my brain said I needed to do and what my gut didn't want to do. I gave the instructor controls and he opted to turn us into a side slip that felt like 30 degrees yaw, and we dropped like a stone sideways. At about 300 ft he turned rudder and landed straight like he was parking in his driveway. Scared the absolute crap out of me.

And yeah, LA sky is dangerous. In that flight I had a dot the size of a mosquito loom into a small jet in about 5 seconds...

if I do another $60 intro lesson, it'll be up here in Oregon.

A few minutes after takeoff from Gillespie, I noticed a bird turn from a dot, then a black blob, rapidly passing above us. I turned to look at the instructor and said "did you see that?" ? We were at maybe 6,000MSL and there were birds above us. I wasn't scared but just astonished at how much was going on.

I got bit by this bug some years ago.

I can suggest you get a machine dedicated to the task of running only flightsims. ;) You're going to need disk space and GPU.

My current "flight" laptop is a mid-spec gaming system from 3 years ago, paired with a Warthog HOTAS setup with stick, throttle and rudder controls (https://www.thrustmaster.com/products/hotas-warthog/), a dedicated speaker system, and a comfy lazyboy specifically for the task of seating me in comfort for hours on end. ;)

There are a couple alternatives to the Warthog - many people suggest Virpil (https://virpil-controls.eu) or VKB (https://flightsimcontrols.com/product/gladiator-evo-space-co...) controls instead.

One thing to know is that Virpil is backwards-compatible with Warthog, so if you go the (cheaper) route with Warthog and later decide to upgrade, that's a bonus.

Either way, be prepared for an investment. This is one of those hobbies where you can start out mid-range/cheap, and end up investing 5x - 10x as much as you become a better (armchair) pilot.

Still .. cheaper (and safer) than having a real airplane, and a lot of fun ..

Try FlightGear (https://www.flightgear.org/) it is a Free Software simulator, and super fun .. specially with real maps and weather. And there are bunch of tutorials.

For software, you're looking at, in no particular order:

  - X-Plane 12
  - Microsoft Flight Simulator 2020/2024
  - Prepar3d (fork of Flight Simulator X)
  - FlightGear (free, open-source)
  - Digital Combat Simulator World (aka DCS World, combat flight simulation; specialises in jet fighters)
  - Orbiter 2016 (space flight simulator; also free)

Modern flight simulators today are generally quite intensive on hardware—especially the CPU—even at low rendering settings. The article is a great example; all of these calculations are fully CPU-bound. It is strongly recommended to get a high-frequency, high-core-count, large-cache CPU—this is probably any of the 3D V-cache Ryzens (5800X3D, 7800X3D, 9800X3D). A _decent_ GPU is recommended for graphics eye candy, but not strictly necessary for accurate flight simulation if you're happy to turn the graphics knobs down (although I've heard that FS2024 has offloaded some weather and physics calculations to the GPU; don't quote me).

For simulation hardware, you can't go wrong with a Logitech Extreme 3D Pro joystick which is fairly inexpensive new (https://www.logitechg.com/en-gb/products/space/extreme-3d-pr...), although you can actually still use mouse + keyboard if you're more interested in simulating the systems and procedures of jet airliners.

Tutorials: I do believe the game simulators have built-in tutorials, though it's been a while since I've followed any of them. Searching for '<flight simulator> Cessna 172 VFR tutorial' is a decent place to start. For a more structured work-through, PilotEdge (a virtual ATC network) has some: https://www.pilotedge.net/workshops

Speaking of virtual ATC, at some point you'll get bored of being the only person simulating. All the game simulators have a multiplayer option, but if you want to get serious with the role-playing, VATSIM is a great place to start and has worldwide coverage, depending on when ATC providers log on. I've found that European ATC is generally online on weekday evenings UTC, and American ATC is generally online on Saturday mornings (UTC) and at the weekends.

PilotEdge has more limited, but more round-the-clock coverage, and is a paid network, and takes the seriousness and realism to the next level.

Vatsim is a great place to start if you're very serious about your radio protocol. Don't expect them to take you by the hand and teach you. They expect you to know what you're doing. They don't have any time for people who are just there for a chat. It's a pretty serious sim community. Nothing bad about that but if you're just messing around and hoping to say hi to some other people it doesn't really go down well there.

> Vatsim is a great place to start if you're very serious about your radio protocol

> They expect you to know what you're doing.

These two statements are a little contradictory. Definitely VATSIM is not a place to start, they expect you to know how to operate in ATC and even just operating your plane is a significant hurdle in the beginning which you need to get over before going to VATSIM.

Yeah the place to start thing was something that the OP said. I intended to put that into perspective by adding some ifs and buts.

But yeah to be honest vatsim is not a good starting point at all. Totally agreed there. I just didn't want to sound negative. Especially because I don't think it's a negative thing at all. They're just people that are very serious about simming and there's nothing bad about that.

And yeah controlling the plane is the first thing to learn. If you can't maintain altitude or a vector I'm sure they'll call you out just like a real ATC would. When I learned to fly the comms part would stress me out because it was distracting. So usually the instructor would handle it. I was lucky to learn at a controlled airport so I would spend the day between flights just listening. I even had an air band receiver in the car :)

Thank you!

Yeah, I'm mostly looking for someone to hold my hand. The limited amount of time I have I'd love to actually learn and play and not search for the "best tutorial for XYZ". So anything with a guided path is perfect.

I do have an old Saitek Cyborg Evo, not sure if it still works) so I'll try that first.

FSacademy has lesson packs that I've found pretty good for Microsoft Flight simulator. Though they are not super US-centric.

The built-in lessons are decent for the basics. The older flight simulator lessons with Rod Machado were much, much better. I had picked up FSX on Steam for cheap during some sale, and they are available digitally there. I've still used that for reference, and even though they obviously don't integrate interactively with the new Microsoft Flight simulator, you can still use them as ideas to practice skills.

If you decide to get serious about it, bite the bullet and get rudder pedals. In my opinion adding feet coordination is a much bigger adjustment than yoke versus stick or a fancier stick.

Also VR is truly a game changer. It requires beefy hardware and will ratchet up the cost, but it will seem downright cheap compared to real flight time.

for software, I'm very happy with X-Plane, specially if you own a mac. For hardware, you could use an xbox joystic, but I would highly recommend this: https://yawmanflight.com/ - it's perfect for on-the-go and tbh much more convenient than a full yoke + pedals. I sold my yoke and pedals and now just use the yawman.

If you're a nerd, https://av8n.com/how/ is one of the greatest tutorials there are. It's not simulator-specific but goes through all the fundamentals at a level where you'll be able to handle a lot of non-usual situations on your own.

MSFS 2024 has career mode with flying lessons. Initially buggy, but imo will be fine in a few months.

Thanks to the massive GPU/APU wave we’re starting to see some very fun demos using realtime computational fluid dynamic simulations instead of blade element models [1].

This would let you accurately sim helicopter prop wash on landings, wake turbulence, and some of the more extreme flight characteristics of the Alaskan style STOL aircraft with bush wheels and snow mobile engines [2].

In particular Blade Element simming struggles when one is riding the stall envelope as seen in the later field of aviation.

[1] https://youtu.be/RIxrN7yedyQ

[2] https://youtu.be/B-brmk1ua1g

How's the simulation of planes in Kerbal Space Program or Juno New Origins work compared to this?

I don't think vanilla KSP aerodynamics simulate airflow at all. You could have wings clipping and they would still pretend to be generating lift. The F.A.R. mods adds much more realistic aerodynamics.

Thanks. Does FAR use a similar strategy as this or something different?

I so miss that past X-Plane version where you could build your own planes and even fly around (and spectacularly crash) in the thin Mars atmosphere. And planes were still completely controllable from the keyboard.

What happens if you put a Boeing 737 MAX airframe into this simulator?

Strictly speaking the airframe of the 737 MAX is airworthy and stable, and it should remain straight and level given the physics simulations of the airframe.

Whether or not it nosedives would depend on how accurately the problematic MCAS systems (which then actuate the flight surfaces) are simulated.

Without MCAS, the 737 MAX has a significant pitch up tendency. You can actively trim your way out of this, but it might be a quite notable effort. It is airworthy, but that does not mean it is automatically flying straight and level.

With working MCAS, it should fly roughly like the pre-MAX version, with automatic trim adjustments to hide the significant pitch up tendency that the pre-MAX version with its much smaller engines did not have.

With a buggy MCAS with the failure conditions met, you might have sporadic significant pitch-down.

(... And with a blown load reduction device in the left engine, e.g. from a large bird strike, you'll have the cockpit filled with smoke at fatal toxicity within 39 seconds, but despite being completely avoidable by flicking one switch, and despite also affecting other aircraft with similar devices, the FAA doesn't find it worth any immediate action.)

All documentation I've seen says that MCAS only activates when the plane has a dangerously high angle of attack, flaps are retracted, and the autopilot is not engaged.

Almost all flights other than by test pilots or air show pilots will never have MCAS do anything unless it receives faulty sensor data, as was the case in the two crashes.

Yes, this is how it should have operated from the beginning. MCAS was flawed when the MAX was first put into operation. Personally, I feel that the MCAS system is "airworthy" now. But that is just MCAS...What is more concerning to me is the quality issues that Boeing has for all aspects of their aircraft. To be clear, this is not specific to the MAX, this is any aircraft that Boeing has pushed out their doors in the past 10 years or so. The foundation for Aviation Safety has a an excellent podcast that goes over the numerous quality issues Boeing has that still exist to this day. https://www.foundationforaviationsafety.org

Boeing used to be a great company that prioritized safety over everything else. (If it ain't Boeing, I ain't going) The "merger" with McDonnell Douglas was the end of that version of Boeing. IMHO, the Boeing 777 was the last great airplane Boeing built. That plane would not be made in the Boeing of today because the initial investment was so high.

Within the normal flight envelope MCAS doesn't activate. MCAS was designed only for the case of high alpha low speed high thrust. Otherwise the max flies very similarly to the NG. The MCAS crashes were only possible because of faulty AOA sensors. There is no inherent defects in the flight characteristics of the MAX.

To be clear, even if MCAS was strictly necessary during all aspects of normal flight, it is not a defect in flight characteristics to require computerized control of flight control surfaces as long as the aircraft is properly designed for it (as opposed to acting with gross neglect for human life). See any fighter jet, or even a regular Airbus with its highly abstract fly-by-wire system.

It nosedives randomly?

(if accurate)

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