2 hours ago, blingthinger said:

I guess I'm specifically wondering about datarefs. I'm certain Austin is fine tuning the fuselage to some degree. I doubt it's just a cylinder outright. If there are additional parameters you wizard devs use, I'm all ears!

the force vectors are on the "physics model" wireframe, the xp flight model is (and always was) a simplified cfd model, which gets refined as "to simple" gets identified by bug reports.

Last time I saw him doing fuse stuff was circa 2018, it was those changes that broke everyones planes iirc.

https://developer.x-plane.com/2018/05/better-fuselages-through-science/

He just did a load more with the F4 instructor related FM changes.

https://developer.x-plane.com/2022/02/x-plane-12-flight-model-update-supersonic-transition-delta-wings-and-mass-properties/

latest fm dev report is here

https://developer.x-plane.com/article/x-plane-12-flight-model-report/

just some "light reading" lol.

they really are that open with the "behind the scenes" stuff. I find it fascinating and love getting my hands dirty even though I rarely have the time to properly commit to flight sim stuff - hence saving the 744 project.

 

On 7/26/2022 at 10:28 AM, blingthinger said:

I would not dismiss this actually. A great many corporate projects start because some executive thought it would be 'fun'. The fact that there was zero policing on the 'student' licensing side meant they were definitely letting the little folks like us continue having fun with it. 

But did they treat it as a game? Yes. Yes, they did. War games, to be precise. ESP(FSX) was specifically targeting situational awareness training. Largely battlefield procedures. Do you think they were shopping around to replace their F22/F35 simulator cores with ESP? Mmmm, no. Given LM was selling it though, I'm certain at least some military entities around the world have used it at some point.

The fact that XP appears in so many flight training devices (motion or not) is indeed more an indication of Austin's commitment to his product. FSX/ESP has bounced from licensee to licensee (latest is Asobo). Lockheed Martin is probably the only one of that club to be able to take it seriously at the Federal level.

As for flight model quality, it is to a certain degree, a representative badge. Airliners and autopilots are easy. What I want to know is what happens when you stomp on the rudder. Or what happens when jetwash is entraining flow on the horiz stab of an F4. The current flock of look-up-table models (DCS possibly excluded) can't and don't account for that. XP does and will.

I have experienced microbursts in P3D4.5

A2A V-35 under ASN Live using A2A Accufeel.

There is a bit of third party code going on there buy microbursts are surprising hard for sims.

On 7/28/2022 at 9:56 PM, mSparks said:

latest fm dev report is here

https://developer.x-plane.com/article/x-plane-12-flight-model-report/

just some "light reading" lol.

they really are that open with the "behind the scenes" stuff. I find it fascinating and love getting my hands dirty even though I rarely have the time to properly commit to flight sim stuff - hence saving the 744 project.

 

@mSparks, the last link is the reason I have been a fan of X-Plane throughout it's various versions and since I tried the first demo of XP2 ( which for some years was prohibitive because it costed $$$ ).

Sometimes simmers ( me included ) come with the rather rhetorical question - why is X-Plane's FM better ?

It can of course,, just as any other approach used in a nowadays desktop flightsim, have it's limitations and shortcomings, but the level of detail offered to tallented developers has to be clearly identified when we read these reports, by either Austin or one of those devs talking about their work.

There are so many nuances, and yet I'll pick just one, far from being the most relevant but yet much diferent in it's way of modelling flight controls from the one used in all MS-derived sims, up to and including FS 2020 - the THS ( trimmable horizontal stabilizer ) !

In X-Plane we can actually model this sort of trimming, by having pitch trim work on the whole horizontal stabilizer. We can also model aircraft ( like most modern gliders ) where the whole Horizontal Stabilizer is at the same time the Elevator.

The fact that trimming control surfaces also works as IRL, not moving them arbitrarily as we trim even if there isn't enough dynamic pressure ( for instance when the aircraft is standing still at the gate and we're not in a Gale situation ... ).

Reading through those lines also reveals a few other details introduced for X-Plane 12, including prop physics, fuselage and other miscellanious bodies aerodynamics, etc....

OFC this sort of details can also make fine tunning of a given aircraft model more complex because some of the effects modelled don't have direct parameters to modulate their effects depending on the outcome, but just as in any other flight simulator platform, tallented devs will often find their way around these "obstacles"...

I found the section about weaher interesting, although I confess that the component that most directly connects to my interests ( soaring weather ) can still be improved. Yet I get the idea that simulating soaring in XP12 will be more realistic than in previous versions 🙂

Edited July 30, 20223 yr by jcomm

14 hours ago, jcomm said:

The fact that trimming control surfaces also works as IRL, not moving them arbitrarily as we trim even if there isn't enough dynamic pressure ( for instance when the aircraft is standing still at the gate and we're not in a Gale situation ... ).

Well as I said in the past, I consider this specific aspect mostly cosmetic and unrelated to FM realism. The "unrealistic" movement of surfaces with trim even at zero airspeed is necessitated by the limitation of PC flight controls that, in 99% of cases, have no force feedback.

Infact, even in those sims where the surfaces react to airflow during ground roll (XP, DCS), they don't actually react to airflow once in flight (as it should be in a PC flight sim!).

What is important for realism though, is the change in e.g. elevator trimmed position when flaps configuration changes (I think the DCS P51 does that? Or was it the DCS Spitfire?). But that is highly aircraft specific and probably best left to the aircraft designer.

 

8 hours ago, Murmur said:

Well as I said in the past, I consider this specific aspect mostly cosmetic and unrelated to FM realism. The "unrealistic" movement of surfaces with trim even at zero airspeed is necessitated by the limitation of PC flight controls that, in 99% of cases, have no force feedback.

Infact, even in those sims where the surfaces react to airflow during ground roll (XP, DCS), they don't actually react to airflow once in flight (as it should be in a PC flight sim!).

What is important for realism though, is the change in e.g. elevator trimmed position when flaps configuration changes (I think the DCS P51 does that? Or was it the DCS Spitfire?). But that is highly aircraft specific and probably best left to the aircraft designer.

 

Yes, Murmur, it's indeed a very sensible aspect of desktop flight simulation, and I consider that DCS isn't "the best there is" in that respect... As a matter of fact I still have IL-2 Great Battles as the reference and in that sim you do see the control surfaces react to airflow under any circumstances.

On ground for instance, and in a 109 with it's THS but also elevator trim tabs which are ground ajustable you can observe the elevator moving if you brake the aircrfat and add power. The propwash itself when hiting the tail surfaces cause all of the trimmed elements to start moving accordingly. Problem is more in how the controls in the cockpit react... They do move, and even in the air as dynamic pressure builds up, for instance going from a slow flight to a high speed deep dive you can watch their movement.

Edited July 31, 20223 yr by jcomm

On 7/30/2022 at 10:08 AM, jcomm said:

why is X-Plane's FM better ?

This kind of absolute is where a lot of pointless arguments arise imho.

It is possible to make an aircraft suitable for at least some training aspect in pretty much any sim, Condor soaring, MSFS, Xplane, P3D, DCS, Aeroflight, Flightgear etc. etc.

IMHO, XP's unfair advantage is not so much that Austin is breaking boundaries when it comes to creating a highly realistic flight model, which he is - Or whether Ben, Sindey and their art team can do as good a job visually as Microsoft - which of course they can - but rather that the effort required for developers to utilise the flight model for their aircraft is the lowest of all of the sims I've come across, that means the "collective we" get more aircraft of higher quality for significantly less investment on the parts of third parties, greatly increasing the chances that your favourite bird is done to a very high standard without having to remortgage the house to get it - from scratch if necessary.

5 hours ago, jcomm said:

On ground for instance, and in a 109 with it's THS but also elevator trim tabs which are ground ajustable you can observe the elevator moving if you brake the aircrfat and add power. The propwash itself when hiting the tail surfaces cause all of the trimmed elements to start moving accordingly.

Yes that's the effect I was referring to, but on ground it's pretty much only cosmetic. It surely is a nice touch though.

 

5 hours ago, jcomm said:

They do move, and even in the air as dynamic pressure builds up, for instance going from a slow flight to a high speed deep dive you can watch their movement.

Hmmm... But if the aircraft is trimmed for a specific AoA (i.e. for a specific airspeed, barring configuration changes), to go from slow to high speed you need to actually move the control surfaces or change their trim, so that's what happens in every flight sim...

If you mean instead that in IL-2 the surfaces actually move even in transient airflow (say, after giving an elevator pulse and letting the aircraft oscillate), then that would mean IL-2 models stick-free stability, and I'm not sure that would be the right choice in a PC flight sim...

Edited July 31, 20223 yr by Murmur

34 minutes ago, Murmur said:

then that would mean IL-2 models stick-free stability, and I'm not sure that would be the right choice in a PC flight sim...

It 100% depends on the aircraft though.

Off the top of my head, the "real" Gazelle helicopter has sas, the r44 doesnt, that completely changes the helicopter response regardless of the aerodynamics.

Same goes for automatic pitch trimming, some aircraft have it, others dont.

Edited July 31, 20223 yr by mSparks

1 hour ago, Murmur said:

If you mean instead that in IL-2 the surfaces actually move even in transient airflow (say, after giving an elevator pulse and letting the aircraft oscillate), then that would mean IL-2 models stick-free stability, and I'm not sure that would be the right choice in a PC flight sim...

It's something I tried to measure myself, and asked at the IL-2 forums because it also depends on the way the aircraft controls are actually acting / rigging / SAS ( as mentioned by mSparks ) / etc...

In my RW glider tests I used both stick fixed and stick free measurements. They're difficult to make IRL due to various factors, and not having the appropriate intrumentation to measure stick deflections. In IL-2 I get the idea that transient airflow effects are also reproduced, but I would have to have access to the raw data regarding actual control deflection to be sure.

Anyway, when I mentioned it in XP vs MSFS in the very first place I am comparing the fact that MFS always modelled pitch trim as THS. I haven't yet figured out if it's the same with the Modern FM, but in XP we can have different trimming systems available, like IRL, like THS and elevator trim tabs, ground adjustable or controllable from the cockpit. With the new Airbus model I expect o see even fancier trimming systems being modelled.

Edited July 31, 20223 yr by jcomm

1 hour ago, mSparks said:

It 100% depends on the aircraft though.

Off the top of my head, the "real" Gazelle helicopter has sas, the r44 doesnt, that completely changes the helicopter response regardless of the aerodynamics.

Same goes for automatic pitch trimming, some aircraft have it, others dont.

Well any stability augmentation system should be correctly implemented for either fixed or rotary wings, if realism is the target. As you suggested, even in XP, helicopter handling changes immensely depending if it has stability augmentation or not.

Paradoxically (or maybe not), fly-by-wire aircraft can be reproduced more realistically on a PC flight sim because the limitations of PC flight controls tend to disappear (e.g. a joystick is much more similar to a Airbus/F16 sidestick than to a B737 yoke).

 

1 hour ago, Murmur said:

should be correctly implemented

And this is where LRs decades of knowledge and experience of simulating aircraft gives them an unfair advantage. (note to trolls, the unfair part is sarcasm, hard work and dedication isn't cheating)

Chances are, if an option isn't there by default, they already added everything needed to build a custom implementation with minimal effort and without breaking absolutely everything else.

Now, how well a particular aircraft leverages the tools available is a whole other conversation, but not one you can have in general. PMDG have similar experience for the aircraft they have built over the decades - but unlike LR - they aren't really "sharing", so their benefits of decades of knowledge and experience is restricted to the aircraft they produce, and the things they have done themselves.

On 7/29/2022 at 9:30 PM, Gary1124 said:

There is a bit of third party code going on there buy microbursts are surprising hard for sims.

I can see how that would be a challenge for the weather models. I'm not familiar with how they form or how often they are encountered, but I'm betting you wouldn't want to mirror what XP does with thermal modeling. I think that just sets up a random patchwork of updrafts around the terrain, without keying off of terrain or temperatures. Flying from microburst to microburst probably isn't too realistic! Or at least, one shouldn't be flying then if it was.

1 minute ago, blingthinger said:

I can see how that would be a challenge for the weather models. I'm not familiar with how they form or how often they are encountered, but I'm betting you wouldn't want to mirror what XP does with thermal modeling. I think that just sets up a random patchwork of updrafts around the terrain, without keying off of terrain or temperatures. Flying from microburst to microburst probably isn't too realistic! Or at least, one shouldn't be flying then if it was.

The microburst was on final into Space Coast regional in the wake of a (Florida) off shore T-storm. A2A Accusim working off of ASP3D weather data. Even Allegient and Delta doesn't mess with T-storms there. I should have heeded the metar report. I use Allmetstat for metar and flightaware for plates. It's sick. The realworld services match the sim which matches the realworld conditions. Live traffic with a comprehensive visual model library would be the end especially if ATC sees it.

5 hours ago, blingthinger said:

I'm not familiar with how they form or how often they are encountered

 

Edited August 1, 20223 yr by mSparks

They associated with convection and storms resulting from it in highly unstable atmospheric conditions.

Nothing better than reading the description from an official source like the UK MetOffice or NOAA:

How Do Downbursts Form? (weather.gov)

In older versions of XP you could place a downburst irrespective of any other associated weather phenomena, but I strongly believe they'll somehow be tied to convective areas in the new weather engine coming with XP12.

A downburst caused one of the most terrible accidents in the history of civil aviation in Portugal, the Martinair crash during landing at Faro airport ( LPFR ) in 1992:

Did Authorities Cover Up the Real Cause of this DC-10 Crash? Martinair Flight 495 | 4K - YouTube

In an uncomparably smaller scale I myself experienced a downburst episode while flying a Grob 103 Twin Acro near Sintra airbase ( LPST ).

I had taken off from rw 14 and we were briefed for convective cells in the vicinity of the airfield, to the southwest, but since we "had" to make that flight for an aviation magazine we decied to go, me in the Grob 103 two other collegaues in AS K21s.

Around 10 min after takeoff, already in free flight, I decided that the weather conditions weren't compatible with the planned route and were deteriorating rapidly, so I headed to the airbase and radioed our ground station asking for which rw to use since the winds were really strong and there were turbulence patches allover the place. Another pilot had just landed using rw 34 which was indicative of a pronnounced change in wind direction. Was told to use rw 14 because that was what the windsock was indicating at the moment.

A direct to rw 14 threshold path was chosen and I really had to manoeuver to escape some hard turbulence, with strong up and down drafts, but the worst came near the short final, after aligning with the rw I suddenly noticed an incredibly high sink rate. There's no go arround thrust in a glider so my only option was to fully retract the spoilers and fly the glider the best I could. The landing was uneventful, we came to a stop and then, before I had the chance to brief the passenger in the front seat he decided to open his canopy, which was promptly projected and detached from the glider braking into pieces and damaging part of the canopy joint 😕  Took more than a month to repair, but that was nothing compared  to what might actually have resulted from such a wrong decision of flying in that day...

 

Edited August 1, 20223 yr by jcomm