Impressions on FSX Flight and Powerplant models

[Murmur 3,941]

>Great video.>He talks like the main character of the "Sick Sad World">tv-show. :DSorry guys! Wrong forum, lol.Marco

[chrisal 9]

I just want to reinforce Jon's comment regarding the contributors to the Avhistory.org forum.Have you ever tried to create an FDE from the ground up - rather than crudely "adjust" the default 737?These people can and do. They probably understand more about the FS simulation and real world flight/engine dynamics than the rest of us put together. As Jon said, they even created the tools we use.The authenticity of the flight experience surely depends very largely on the accuracy of aircraft behaviour - unless, of course, we all want a totally stable point-and-shoot arcade game.So it really is to be regretted if FSX has not enabled more subtle and realistic adjustment than FS9 and predecessors.Let's hope this is not the case.CheersChris

[Guest Ron Freimuth]

>I'm a bit confused as to how the change to zero lift drag>would come into play in flight. Do we normally operate these>aircraft at the airspeeds where that variance would be seen as>preventing accurate simulation? Prop aircraft models generally don't require Compressibility (Mach) effects in the model. Though, Compressibility does have some effect for high performance aircraft flying at high altitudes. Jet aircraft almost always enter the transonic range; that's why most jets have swept wings to delay the Critical Mach Number (MCr), where flow first becomes supersonic and shock waves form.>Also, is the value of significant enough a change to truly>prevent accurate flight dynamics without it, or is it just a>personal pet peeve of yours that it's not supported? I've found one can model typical jet transports fairly closely with the coarse, default Mach tables. Which have an implicit Mach scale going from Mach 0.0 to Mach 3.2. In increments of 0.2 Mach. TBL 401 is also critical, fortunately that can be set with high resolution in the transonic region; it uses floating point datums that can be set as needed. At lower flight levels and/or flight weights, Cdp predominates. Total drag coefficient, CD, equals Cdp + Cdi. Cdi is typically 35% of Cdp. Cdp = Cdo + Cdm, and Cdm may only be 2% of Cdo at Typical Cruise Mach. However, to model an aircraft such as the 747 at the highest normal cruise, M 0.865, one has to compromise the Cdm table, which can only be set at M 0.6, 0.8, 1.0, etc. Fuel consumption varies almost directly with Drag. If one wants accurate PPH over the normal range of cruise Mach's problems often arise. The coarse Mach tables are mainly a problem with supersonic jets, such as fighters. Ability to penetrate the 'sound barrier' realistically, and accurate cruise fuel flow require higher resolution tables than provided in MSFS/CFS. While more than just Cdm affects drag, real graphs of this component typically show Cdp (Cdo+Cdm) starting to increase rapidly at Mach 0.975, peaking around 1.00, then often dropping as the hypersonic realm is entered. In FS/CFS, one can only set straight line variations at M 0.8, 1.0, 1.2, etc. Which gives way too much increase at M 0.9, but possibly not enough at M 1.0. >Bottom line... does the end user actually see a completely>different aircraft with the good doctor's values or is it>something so trival that it's insignificant? In the end, it's just a matter of whether 'Arcade Game' performance modeling is good enough, or if something better is desirable. MSFS graphics have continued to increase in resolution, I often have a hard time telling if an image is of a real aircraft, or an FS screen shot. Unfortunately, fine structure detail in the AIR file tables has generally not increased since FS98 (though, a few new tables have been added since FS98). According to the Avhistory.org thread, high resolution Mach tables were implemented in the pre-beta CFS4 (which never got to beta testing). But, the enhancements implemented in CFS4 were discarded in the later development of FSX. RAF

[WarpD 824]

Sounds to me like the vast majority of FS users would never see a difference.Given that, and considering MSFS is a commercial product designed to target a broad audience of customers... I don't see the lack of supersonic aircraft modelling as being a critical failure.Not that I'm against improved flight dynamics, I'm just not agreeing that FSX is to be poo-poo'ed.It's like I said before... some people didn't get what they consider to be the only important changes. That does not make FSX bad.

[tgibson 11]

Hi,No one here said that FSX was bad. They said that the FDE was no improvement over FS9. And I guess if that is one of the important things to them, then this is disappointing. I have no problem with someone saying that, as long as the background is clear (which it was). I am also disappointed that the FDE's have not been improved, or at least brought back up to FS2002 levels.However, while the FDE equations might not have changed, several people have commented that the flight experience in FSX is better, due possibly to better interpretation of the same FDE's.--Tom GibsonCal Classic Propliner Page: http://www.calclassic.comFreeflight Design Shop: http://www.freeflightdesign.comDrop by! ___x_x_(")_x_x___

[Guest Ron Freimuth]

>Hi,>>No one here said that FSX was bad. They said that the FDE was>.........>However, while the FDE equations might not have changed,>several people have commented that the flight experience in>FSX is better, due possibly to better interpretation of the>same FDE's.>>-->Tom Gibson I have mentioned that I suspect the FM iteration rate has been increased, or improved. Based on user reports, and the fact that the Ultra Light is set with lower MoI's and weights than would be stable in FS9 and earlier. I have also mentioned the new SDK (in the FSX Beta) still has the same old explanations for lines in aircraft.cfg. Some are amateurish, others vague. Some are simply wrong. Moments of Inertia are given in "slugs per foot squared" in some places. Simply wrong, the correct English dimensions are "slug - foot^2". They still have 'Time Constant' bass ackwards. The line with 'Prop Coefficient of Friction' is incorrectly named. A year ago someone determined that it actually relates to Prop Coefficient of Power (Cp) (at high Beta). Such matters do little to inspire confidence. RAF

[Guest Douglas K]

This subject seems premature, since the game isn

[mgh 89]

"Moments of Inertia are given in "slugs per foot squared" in some places. Simply wrong, the correct English dimensions are "slug - foot^2". "In England, and all other counties that have adopted SI, the units of moment of inertia are kilogram metre squared.

[Guest Ron Freimuth]

>"Moments of Inertia are given in "slugs per foot squared" in>some places. Simply wrong, the correct English dimensions are>"slug - foot^2". ">>>In England, and all other counties that have adopted SI, the>units of moment of inertia are kilogram metre squared. True, kg-m^2 in SI. g-cm^2 in CGS. However, much, probably most, of the aerodynamics engineering literature still uses English units. Including, I think, NASA documents. English engineering units are fine, as long as they are correctly applied. While European "Metric" measurements in common aviation usage as at least as ######ized as the English usage goes. For example, aircraft weights are given in kilograms, which is not a weight, but a mass. RAF

[Guest Ron Freimuth]

>This subject seems premature, since the game isn

[Guest Douglas K]

>>>> It appears the availability of the Demo, and then the FSX Beta, was mainly to honor the 'new openness' the ACES people agreed on over a year ago. They came too late to have much effect on FSX development. The official Beta testing should have been enough to resolve the issues. The more public releases were mainly to appease the masses who just can't wait to see what the new version might offer.<<<

[mgh 89]

"While European "Metric" measurements in common aviation usage as at least as ######ized as the English usage goes. For example, aircraft weights are given in kilograms, which is not a weight, but a mass"It's not ######ised but correctly distinguishes between mass and force.The kilogram is the SI unit of mass, which is constant for a given object. The packet of sugar on my shelf is correctly labelled as being 1kg. Weight is a force and is the mass multiplied by the acceleration due to gravity and has units of Newtons. The gravitational force varies by about 0.5% over the earth's surface so an aircraft's weight would vary depending on where it is.SI eliminates the nonsense of the Imperial system having to use pounds force, pounds mass, poundals, and slugs as units to distinguish between mass and force.1 pound force = 4.448 Newtons1 pound mass = 0.435 Kilograms1 poundal = 0.1382 Newtons 1 slug = 14.594 kilograms

[Guest Mathias]

>1 slug = 14.594 kilogramsThanks for finally letting me see the "slug light"! It does not even show up on the great little convert.exe conversion utility...Concerning improved flight models in FSX - there is indeed at least one which was far overdue: Bell_206B_JetRanger.airNo longer the fidgety FS98 file, but a joy to hover - much better simulating what this heli's rotor blades do to stabilize it.Don't know about the internals, though, like engine simulation and such.