[Flightgear-devel] Motion Base Simulator ?
You've seen those hydraulically actuated little simulator rides? Forget that, here's a bigger one: http://tinyurl.com/2oxzd Jon ___ Flightgear-devel mailing list [EMAIL PROTECTED] http://mail.flightgear.org/mailman/listinfo/flightgear-devel
RE: [Flightgear-devel] Web, tables, and image layout
OK. Fixed. Jon www.jsbsim.org ___ Flightgear-devel mailing list [EMAIL PROTECTED] http://mail.flightgear.org/mailman/listinfo/flightgear-devel
Re: [Flightgear-devel] Web, tables, and image layout
I figured it out. This works: http://sourceforge.net/export/projnews.php?group_id=19399&limit=10&show_summaries=1"; target=MAIN> onmouseover="loadImage(this,sbB2);showStatus(alt);return true;" onmouseout=defaultStatus();loadImage(this,sbB1); alt="Latest news about JSBSim" src="menu_sep_news_2.jpg" border=0> While this does not: http://sourceforge.net/export/projnews.php?group_id=19399&limit=10&show_summaries=1"; target=MAIN> onmouseover="loadImage(this,sbB2);showStatus(alt);return true;" onmouseout=defaultStatus();loadImage(this,sbB1); alt="Latest news about JSBSim" src="menu_sep_news_2.jpg" border=0> The subtlety is that there can be no whitespace between the beginning of a data cell and the first element of the cell, nor can there be any whitespace between the last element in the cell and the close of the cell (i.e. with a ). In the second case, above, there is a carriage return after the opening , and also before the closing . This is, apparently, a no-no. Jon ___ Flightgear-devel mailing list [EMAIL PROTECTED] http://mail.flightgear.org/mailman/listinfo/flightgear-devel
RE: [Flightgear-devel] OpenAL - http://www.openal.org
Curtis L. Olson writes: > > I have an application in the pipeline where I'll need to play left > engine sound out of the left speaker and right engine sound out of the > right ... hopefully resulting in the proper effect when an engine goes out. > > As far as I know, this is impossible to do directly with plib because it > only supports 8 bit mono sounds ... no stereo. You can't even fake it > by crafting two .wav files one with no right channel and one with no > left ... no stereo support in plib. > > I'm looking at OpenAL and it appears that everything has to be > positioned spacially (for good or bad). I'm going to quietly ingore the > calls for doppler affects, etc. and other fancy stuff at this point ... > that would go into the "someday after the basics are working" bin. An OpenAL extension was just written for OpenSceneGraph perhaps it might be worth taking a peek, I haven't yet. http://www.vrlab.umu.se/research/osgAL/ Cheers Norman ___ Flightgear-devel mailing list [EMAIL PROTECTED] http://mail.flightgear.org/mailman/listinfo/flightgear-devel
[Flightgear-devel] OpenAL - http://www.openal.org
I have an application in the pipeline where I'll need to play left engine sound out of the left speaker and right engine sound out of the right ... hopefully resulting in the proper effect when an engine goes out. As far as I know, this is impossible to do directly with plib because it only supports 8 bit mono sounds ... no stereo. You can't even fake it by crafting two .wav files one with no right channel and one with no left ... no stereo support in plib. I'm looking at OpenAL and it appears that everything has to be positioned spacially (for good or bad). I'm going to quietly ingore the calls for doppler affects, etc. and other fancy stuff at this point ... that would go into the "someday after the basics are working" bin. Does anyone have strong opinions against OpenAL or have reasons I shouldn't explore it? I might try support both plib and openal ... or not depending on how things go ... the sound code isn't all that complicated, but there is some library dependencies wired in there. This would add another build dependency to FG, but OpenAL is a pretty standard thing that appears to support all the platforms that plib supports. Thoughts? Curt. -- Curtis Olsonhttp://www.flightgear.org/~curt HumanFIRST Program http://www.humanfirst.umn.edu/ FlightGear Project http://www.flightgear.org Unique text:2f585eeea02e2c79d7b1d8c4963bae2d ___ Flightgear-devel mailing list [EMAIL PROTECTED] http://mail.flightgear.org/mailman/listinfo/flightgear-devel
Re: [Flightgear-devel] Spitfire Propeller vs. YASim
Vivian Meazza wrote: > Here are some calculations on propeller rpm. > [...] > We can see that 2850 is unlikely to be the rpm of a 10.75 diameter > propeller Yeah, you're right. This is a real bug. I was playing with it this morning, and we're hitting an edge case in the propeller solver. The propeller as defined is actually fine. It sinks the right amount of power and generates appropriate thrust at the specified cruise RPM. The problem is that (due to a deficiency in the model) the torque required to turn the propeller are *lower* RPMs increases faster than the engine torque does*. So while the engine and propeller are matched at cruise; the combination can't get there because it can't accelerate the prop at low speeds. The end result is that this breaks the "stabilize" step in the solver, which tries to iteratively solve for the steady state RPM for an engine/prop before running the aero FDM. Mathematically, the current propeller model has two minima, and it's picking the wrong one. The spitfire is hitting the condition because of the high gear ratio, recent changes in the engine code which reduce available power at low speeds (to get idle speeds right), and a miscalbration quirk in the manual pitch handling (setting "0.5" for manual pitch doesn't produce the same results as a non-variable propeller). I'm not quite sure what the right thing to do here is. One trick would be to jigger the stabilize routine so it starts from an RPM within the right range, but that's going to be really hard to maintain over time. Let me think about it... Andy ___ Flightgear-devel mailing list [EMAIL PROTECTED] http://mail.flightgear.org/mailman/listinfo/flightgear-devel
RE: [Flightgear-devel] Spitfire Propeller vs. YASim
Vivian Meazza wrote > > Andy Ross > > > [Starting a new thread. The reply nesting level in my > > mozilla window was getting freaky.] > > > > Vivian Meazza wrote: > > > The engine I'm trying to specify developed 1140 HP at engine > > > revolutions of 2850 rpm at a boost pressure of 9 psi. It > was fitted > > > with 1:0.477 reduction gearing, which I think means that > > the propeller > > > turned at 1360 rpm. > > > > Hrm, 1360 RPM is very slow for a cruise value, just over idle > > speed for a smaller plane. Likewise, 2850 RPM really isn't > > that fast for a piston engine. It's at the top end of > > ungeared engines like a Lycoming O-360 or whatnot, but not > > really very fast for four stroke engines as a whole (my > > Saturn redlines at 6000, for example). > > > > Is it possible that the 2850 number is a *propeller* RPM at > > max power? Then you'd get a max power engine speed of 5975, > > which seems plausible to me and avoids the problems with > > solving for a propeller which "cruises" at a pitch where > > normal props would be windmilling. > > > > Does anyone have good info on whether the cockpit engine > > speed gauge in a Spitfire (which is presumably what most > > sources will quote for > > "RPM") reads engine or propeller speed? > > > > Andy > > > > > I believe the low propeller rpm was to do with tip speeds > approaching or exceeding Mach 1 at high aircraft speeds. I > will research that next. > > Regards > > Vivian > Here are some calculations on propeller rpm. The propeller the tip speed should be as high as possible with the only limitation being that the tip should not get into the region of aerodynamic compressibility. Typically a figure of Mach 0.85 is used as the magic number that should not be exceeded. (This makes some allowance for the speed increase as the air passes over the aerofoil curved surface and the increase in air velocity caused by the propeller operation.) If we take 8000 ft as the operating altitude then Mach 1 = 1085 ft/sec (approx) Assuming that the forward velocity of the aircraft is 300 mph = 440 ft/sec Then the maximum rotational velocity may be calculated by Pythagoras: Max Rotational Velocity = ((M *1085)^2 - (V)^2)^0.5 -(1) where M is the designed Mach Number (0.85) and V is the aircraft forward velocity = ((0.85*1085)^2 -(440)^2)^0.5 = 810.52 ft/sec RPM at Max rotational velocity is given by: RPM = Max rotational velocity*60/(PI * D) -(2) Where D is the propeller diameter (ft) = 810.52*60/(PI * 10.75) = 1420 rpm Thus we can see that 1360 rpm is more appropriate for this application than 2850 We can also calculate the Max Rotational Velocity @ 2850 Max rotational velocity (PI * D) = (RPM/60) * (PI * D) = (2850/60) * (PI * 10.75) = 1604 ft/sec We can also calculate the Mach Number of the tip by rearranging and substituting in (1) M = ((1604^2+440^2)^0.5)/1085 where M is the Mach Number of the tip = 1.5329 We can see that 2850 is unlikely to be the rpm of a 10.75 diameter propeller Well, I hope I've got the math right! Please pick holes in it. Regards Vivian ___ Flightgear-devel mailing list [EMAIL PROTECTED] http://mail.flightgear.org/mailman/listinfo/flightgear-devel
Re: [Flightgear-devel] High-Quality US Airport Diagrams and Terminal Procedures
Ampere K. Hardraade wrote: What is DAFIF? First hit from Google: https://164.214.2.62/products/digitalaero/index.cfm The databases are available online in two formats: a fixed-length-field format, and a tab-delimited format called DAFIFT. Go for the latter. All the best, David ___ Flightgear-devel mailing list [EMAIL PROTECTED] http://mail.flightgear.org/mailman/listinfo/flightgear-devel
[Flightgear-devel] Web, tables, and image layout
I went ahead and posted the update to the JSBSim web site last night. The slide image buttons don't quite line up. When they do, the effect will be quite nice, I believe. Anyhow, the only thing I can think of that could be responsible at this time is that the images must be an even number of pixels in height. That doesn't sound likely to me, but it's the only cause I can even think of. If anyone else wants to take a look, the website is www.jsbsim.org. The specific panel URL is www.jsbsim.org/Side_Bar.html. Any comments regarding image quality or artistic or navigational issues are solicited and appreciated. Jon ___ Flightgear-devel mailing list [EMAIL PROTECTED] http://mail.flightgear.org/mailman/listinfo/flightgear-devel
RE: [Flightgear-devel] Spitfire Propeller vs. YASim
Andy Ross > [Starting a new thread. The reply nesting level in my > mozilla window was getting freaky.] > > Vivian Meazza wrote: > > The engine I'm trying to specify developed 1140 HP at engine > > revolutions of 2850 rpm at a boost pressure of 9 psi. It was fitted > > with 1:0.477 reduction gearing, which I think means that > the propeller > > turned at 1360 rpm. > > Hrm, 1360 RPM is very slow for a cruise value, just over idle > speed for a smaller plane. Likewise, 2850 RPM really isn't > that fast for a piston engine. It's at the top end of > ungeared engines like a Lycoming O-360 or whatnot, but not > really very fast for four stroke engines as a whole (my > Saturn redlines at 6000, for example). > > Is it possible that the 2850 number is a *propeller* RPM at > max power? Then you'd get a max power engine speed of 5975, > which seems plausible to me and avoids the problems with > solving for a propeller which "cruises" at a pitch where > normal props would be windmilling. > > Does anyone have good info on whether the cockpit engine > speed gauge in a Spitfire (which is presumably what most > sources will quote for > "RPM") reads engine or propeller speed? > > Andy > I pondered that question for quite a while before I decided to use that data. And I agree that the max engine rpm sounds low when compared to modern engines, particularly modern automotive engines. Propeller rpm seems impossibly low, and I wondered if I am misinterpreted the meaning of the published gear ratio of 1:0.477. All documents that I have seen quote the max engine of the Merlin as 3000 (2850 is the max cruise). Similarly, all the POH (Hurricane/Spitfire/p51d) quote the cockpit instrument as "engine rpm" Compare the 2 engines Bore 5.4 in, Stroke 6 in, Displacement 1,649 cu in (27 litres). Max rpm 3000 Bore 3.38 in, Stroke 3.46 in, Displacement 180.75 cu in (2.962 litres) max rpm 6000 This is a rough formula derived for automotive applications. A piston speed of 3500 fpm is usually quoted as an estimate for non-high performance modern engines. RPM limit = (Piston speed (fpm) * 6) / stroke (in) If we take the Saturn data, and re-arranging, we get: Piston Speed = 6000*3.4/6 = 3460 fps We can see that the Saturn complies with this paradigm. Now taking the Merlin data: RPM Limit = 3500 * 6/6 = 3500 rpm We can say that it is highly unlikely that the Merlin engine would have been capable of achieving the 6290 rpm required if the max rpm were quoted as propeller rpm. This would call for a piston speed of: Piston Speed = 6290 * 6/6 = 6290 fps 4000 is usually quoted as the maximum for high performance engines, although the modern F1 engine exceeds this, 4000 would be a reasonable limit for a 1930's engine I think it is safe to assume that the rpm quoted for the engine rpm for the Merlin is indeed the engine rpm. I believe the low propeller rpm was to do with tip speeds approaching or exceeding Mach 1 at high aircraft speeds. I will research that next. Regards Vivian ___ Flightgear-devel mailing list [EMAIL PROTECTED] http://mail.flightgear.org/mailman/listinfo/flightgear-devel
