Re: [Flightgear-devel] New aircraft: SF-25
Hi all, The model was updated again. (Still at http://www.avatarzenekar.hu/files/sf25b.tar.bz2 ). Changes from yesterday: - Dependencies to other models removed - Radio and glider vario now works - Improved sounds I still need some help to figure out why it wants to ground loop so badly on takeoff and especially landing. Any help would be appreciated. Also I promise that if someone sets up the model in FG git, I'll stop spamming the list every time I update it :) Cheers, Vik On 23 August 2011 17:22, Viktor Radnai wrote: > Hi all, > > I have uploaded a newer version of the Falke. Grab it from here as before: > > http://www.avatarzenekar.hu/files/sf25b.tar.bz2 > > The model now has the beginnings of an instrument panel, with instruments > recycled from Instruments-3d or other models. The model specifically depends > on the ASK13, Grob-109, Katana and pa28-161 for now. I had to make a > heavy-handed change to the model, changing the tilt of the instrument panel. > Could someone who actually knows how to use Blender please patch up the > holes left in the fuselage by my change? Also I notice that the wings > sometimes disappear when looking from inside of the cabin, leaving the > wheels, spoilers and ailerons flying in formation with the plane. If someone > could help me fix that, I'd appreciate it. > > I need some help with the instruments as well. The radio, the outside air > temp meter, the glider vario and the engine monitoring instruments don't > seem to work for now. Could you please take a look and give me some pointers > on what I'm missing? > > I did not see what the consensus on adding new models to git was, but could > someone please set up a repo for this model if possible? > > Thanks in advance. > > Cheers, > Vik > > On 08/17/2011 02:10 AM, Viktor Radnai wrote: >> >> Hi all, >> >> I have updated the model. Please download and test again if you are >> interested. >> http://www.avatarzenekar.hu/files/sf25b.tar.bz2 >> >> Many thanks to all especially Gary aka Buckaroo for his yasim xml and >> explanations. >> >> List of changes: >> >> - CG supposedly closer to real CG. >> - More realistic sink rates >> - Probably more realistic engine RPMs as well (can't remember how good >> the ones in the last version were) >> - Brakes now only start working on the last 20% of spoiler travel, as >> they should do >> - Working splash screen, yay :) >> - Incorporated Gary's nasal code snippet for managing the parking brake. >> >> List of known issues: >> - Above mentioned code snippet can't actually test it yet as Shift-B is >> remapped (d'oh). >> - Glide properties seem OK, but trim is nose heavy (stick must be pulled >> most of the time, neutral trim point seems to be near Vne or about 100 >> knots) >> - There seems to be some yaw instability at the moment when the tail >> gear comes off the ground. No idea if this is only in crosswind or not. >> No idea if the real plane does this in crosswind or not. Pulling the >> stick slightly during the takeoff run (which you should do anyway) seems >> to help. Comments from anyone familiar with the type would be very much >> welcome. >> >> Cheers, >> Vik >> >> I can't really follow the discussion on the Yasim internals >> On 08/16/2011 02:29 PM, Gene Buckle wrote: >>> >>> On Tue, 16 Aug 2011, Viktor Radnai wrote: >>> http://www.avatarzenekar.hu/files/P1020617.JPG http://www.avatarzenekar.hu/files/P1020618.JPG >>> Am I the only one that noticed that someone has been mowing a lawn with >>> that prop? :) >>> >>> g. >>> > -- My other sig is hilarious -- EMC VNX: the world's simplest storage, starting under $10K The only unified storage solution that offers unified management Up to 160% more powerful than alternatives and 25% more efficient. Guaranteed. http://p.sf.net/sfu/emc-vnx-dev2dev ___ Flightgear-devel mailing list Flightgear-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/flightgear-devel
Re: [Flightgear-devel] New aircraft: SF-25
Hi all, I have uploaded a newer version of the Falke. Grab it from here as before: http://www.avatarzenekar.hu/files/sf25b.tar.bz2 The model now has the beginnings of an instrument panel, with instruments recycled from Instruments-3d or other models. The model specifically depends on the ASK13, Grob-109, Katana and pa28-161 for now. I had to make a heavy-handed change to the model, changing the tilt of the instrument panel. Could someone who actually knows how to use Blender please patch up the holes left in the fuselage by my change? Also I notice that the wings sometimes disappear when looking from inside of the cabin, leaving the wheels, spoilers and ailerons flying in formation with the plane. If someone could help me fix that, I'd appreciate it. I need some help with the instruments as well. The radio, the outside air temp meter, the glider vario and the engine monitoring instruments don't seem to work for now. Could you please take a look and give me some pointers on what I'm missing? I did not see what the consensus on adding new models to git was, but could someone please set up a repo for this model if possible? Thanks in advance. Cheers, Vik On 08/17/2011 02:10 AM, Viktor Radnai wrote: > Hi all, > > I have updated the model. Please download and test again if you are > interested. > http://www.avatarzenekar.hu/files/sf25b.tar.bz2 > > Many thanks to all especially Gary aka Buckaroo for his yasim xml and > explanations. > > List of changes: > > - CG supposedly closer to real CG. > - More realistic sink rates > - Probably more realistic engine RPMs as well (can't remember how good > the ones in the last version were) > - Brakes now only start working on the last 20% of spoiler travel, as > they should do > - Working splash screen, yay :) > - Incorporated Gary's nasal code snippet for managing the parking brake. > > List of known issues: > - Above mentioned code snippet can't actually test it yet as Shift-B is > remapped (d'oh). > - Glide properties seem OK, but trim is nose heavy (stick must be pulled > most of the time, neutral trim point seems to be near Vne or about 100 > knots) > - There seems to be some yaw instability at the moment when the tail > gear comes off the ground. No idea if this is only in crosswind or not. > No idea if the real plane does this in crosswind or not. Pulling the > stick slightly during the takeoff run (which you should do anyway) seems > to help. Comments from anyone familiar with the type would be very much > welcome. > > Cheers, > Vik > > I can't really follow the discussion on the Yasim internals > On 08/16/2011 02:29 PM, Gene Buckle wrote: >> On Tue, 16 Aug 2011, Viktor Radnai wrote: >> >>> http://www.avatarzenekar.hu/files/P1020617.JPG >>> http://www.avatarzenekar.hu/files/P1020618.JPG >>> >> Am I the only one that noticed that someone has been mowing a lawn with >> that prop? :) >> >> g. >> -- Get a FREE DOWNLOAD! and learn more about uberSVN rich system, user administration capabilities and model configuration. Take the hassle out of deploying and managing Subversion and the tools developers use with it. http://p.sf.net/sfu/wandisco-d2d-2 ___ Flightgear-devel mailing list Flightgear-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/flightgear-devel
Re: [Flightgear-devel] New aircraft: SF-25
Hi all, I have updated the model. Please download and test again if you are interested. http://www.avatarzenekar.hu/files/sf25b.tar.bz2 Many thanks to all especially Gary aka Buckaroo for his yasim xml and explanations. List of changes: - CG supposedly closer to real CG. - More realistic sink rates - Probably more realistic engine RPMs as well (can't remember how good the ones in the last version were) - Brakes now only start working on the last 20% of spoiler travel, as they should do - Working splash screen, yay :) - Incorporated Gary's nasal code snippet for managing the parking brake. List of known issues: - Above mentioned code snippet can't actually test it yet as Shift-B is remapped (d'oh). - Glide properties seem OK, but trim is nose heavy (stick must be pulled most of the time, neutral trim point seems to be near Vne or about 100 knots) - There seems to be some yaw instability at the moment when the tail gear comes off the ground. No idea if this is only in crosswind or not. No idea if the real plane does this in crosswind or not. Pulling the stick slightly during the takeoff run (which you should do anyway) seems to help. Comments from anyone familiar with the type would be very much welcome. Cheers, Vik I can't really follow the discussion on the Yasim internals On 08/16/2011 02:29 PM, Gene Buckle wrote: > On Tue, 16 Aug 2011, Viktor Radnai wrote: > >> http://www.avatarzenekar.hu/files/P1020617.JPG >> http://www.avatarzenekar.hu/files/P1020618.JPG >> > Am I the only one that noticed that someone has been mowing a lawn with > that prop? :) > > g. > -- Get a FREE DOWNLOAD! and learn more about uberSVN rich system, user administration capabilities and model configuration. Take the hassle out of deploying and managing Subversion and the tools developers use with it. http://p.sf.net/sfu/wandisco-d2d-2 ___ Flightgear-devel mailing list Flightgear-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/flightgear-devel
Re: [Flightgear-devel] New aircraft: SF-25
Haha, that was me taxiing her out for takeoff for the first time! Part of the normal taxiway was cordoned off for some kind of car tuning show (you can see that on the left) and we had to go through slightly longer grass, with some weeds sticking out. That's the great thing about a grass airfield, after a point, the planes will take care of the lawnmowing :D On 08/16/2011 02:29 PM, Gene Buckle wrote: > On Tue, 16 Aug 2011, Viktor Radnai wrote: > >> http://www.avatarzenekar.hu/files/P1020617.JPG >> http://www.avatarzenekar.hu/files/P1020618.JPG >> > Am I the only one that noticed that someone has been mowing a lawn with > that prop? :) > > g. > -- uberSVN's rich system and user administration capabilities and model configuration take the hassle out of deploying and managing Subversion and the tools developers use with it. Learn more about uberSVN and get a free download at: http://p.sf.net/sfu/wandisco-dev2dev ___ Flightgear-devel mailing list Flightgear-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/flightgear-devel
Re: [Flightgear-devel] New aircraft: SF-25
On Tue, 16 Aug 2011, Viktor Radnai wrote: > http://www.avatarzenekar.hu/files/P1020617.JPG > http://www.avatarzenekar.hu/files/P1020618.JPG > Am I the only one that noticed that someone has been mowing a lawn with that prop? :) g. -- Proud owner of F-15C 80-0007 http://www.f15sim.com - The only one of its kind. http://www.simpits.org/geneb - The Me-109F/X Project Some people collect things for a hobby. Geeks collect hobbies. ScarletDME - The red hot Data Management Environment A Multi-Value database for the masses, not the classes. http://www.scarletdme.org - Get it _today_! Political correctness is a doctrine, fostered by a delusional, illogical minority, and rabidly promoted by an unscrupulous mainstream media, which holds forth the proposition that it is entirely possible to pick up a turd by the clean end. -- uberSVN's rich system and user administration capabilities and model configuration take the hassle out of deploying and managing Subversion and the tools developers use with it. Learn more about uberSVN and get a free download at: http://p.sf.net/sfu/wandisco-dev2dev ___ Flightgear-devel mailing list Flightgear-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/flightgear-devel
Re: [Flightgear-devel] New aircraft: SF-25
Hi guys, Thanks for this. Gary, I gave your yasim xml a spin. (sorry, long mail ahead) I don't have enough experience with the plane yet to comment on everything. The real thing seems to behave a bit better on takeoff when there is no crosswind -- haven't done a crosswind takeoff or landing yet, so I can't comment on that. One problem with the model is that the support wheels shouldn't both touch the ground, they should allow the plane to tilt maybe 10-15 degrees in either direction. They also bend and flex when slammed hard, for shock absorbtion. The airbrakes are definitely not efficient enough. My school sets down that we must always land the Falke with the engine stopped (they had people breaking the plane with powered landings early on, so they forbade it). Therefore we do a very 'glider-style' landing, pretty steep descent at around 60 knots with the spoilers extended all the way, levelling out just above the runway with the spoilers still out. You just release it back a little so you don't accidentally brake and nose over :) More on that later. This way you touch down at around 35-40 knots, but you must continue to hold the spoilers out, otherwise you might get airborne again above 30 (depending on weight which influences stall speed). See some pics of a landing here: http://www.avatarzenekar.hu/files/P1020616.JPG http://www.avatarzenekar.hu/files/P1020617.JPG http://www.avatarzenekar.hu/files/P1020618.JPG So the speedbrakes must be effective enough to be able to do this :) Regarding the speedbrake/brake link and flight controls... The Falke has a fixed prop and no mixture lever. I've read somewhere that the Limbach engine is actually an adopted VW engine, maybe that's why. Apart from the throttle, all you've got is a carb heat lever and on the C model and later, a cowl flap that helps regulate engine temperature (the B has a fixed cover that you install in the winter only). On landing, the spoiler is your primary glidescope control. I have a Saitek Aviator which has a split throttle -- I map one half to the spoiler and that works great. The problem with the config I submitted is that the brakes start working at around 50% travel. Like you said, this is not correct. Please read on for a somewhat long-winded explanation on how it's used in practice: The Falke's fuselage is welded metal tubing covered with canvas. The actual spoilers are spring-loaded and a fair bit of force is required to pull them out (if you'd let go of the lever, they would slam back down quite violently). There are two spoiler levers in the cockpit -- one on the left, and one between the two seats. When you open the spoilers all the way, the left lever hits one if the fuselage tubes (a vertical one). You've got to pull that lever inward slightly to be able to pull it further back and engage the brakes. Only the C version and newer have a parking brake -- which is actually a small, loose lever dangling on the same fuselage tube that can be used to jam the spoiler in the fully open position. This is the best pic I could find that shows this: http://www.alte-ems.de/flugzeuge/sf25c/sf25c_cockpit1.jpg.JPG The spoiler lever handles are blue, the fuselage tubing and the rest of the spoiler lever is grey. If you look carefully on the left of the pic below the placard you can see a little black knob -- that's the parking brake lever. I'll try to remember to take close ups next time I'll go flying. It's all very crude and simple but actually quite clever and efficient way to ensure that you don't land with the wheel locked. But it seems that it still happens sometimes: http://wap.airliners.net/photo/0003212/L/ :) I wish I had the skills to do these animations, but probably the best I can come up with would be a bit of nasal code to link the spoilers and the brakes. I can see that if we made it work like it does in the real thing, that might confuse and piss off FG users, who might expect that the parking brake, brake and spoiler work independently. Personally I'd prefer if they were linked the following way: 1. If you hit the brakes (b key or toe brake pedals, etc), the spoilers would open all the way. This would do for a handy shortcut for full spoilers. 2. If you set the spoiler controls to 80%, the spoilers should be fully open and you should start applying the brake instead (this would be needed for joystick control). 3. If you set the parking brake, that should apply full brake and full spoilers. This should either override any joystick controls, or it's also OK by me if you can't set the parking brake unless you have either set full spoilers or full brakes. 4. Parking brake should be released by using any of the brake or spoiler controls. What do you think? Is this doable? Does this require nasal coding? Cheers, Vik On 08/16/2011 02:25 AM, Gary Neely wrote: > Vik, > > Based on Maik's CG information and a little nosing around for > performance information onl
Re: [Flightgear-devel] New aircraft: SF-25
Vik, Based on Maik's CG information and a little nosing around for performance information online, I made an el-cheapo quick and dirty FDM: http://ltts.crlt.indiana.edu/grn/flightgear/sf25b-yasim.xml Feel free to use it, lose it, abuse it, or whatever. It's a bit tricky to takeoff and land, especially in any kind of crosswind-- it takes a fair hand on the rudder. It also likes to glide and glide once it gets close to the ground, so you'll definitely not want to approach over 50 kts or you'll never get down. I often side-slipped to help me get down. I disabled the linkage of the spoilers with the wheel brake-- According to the book, brakes are engaged only on the maximum spoiler setting, but I got tired of nosing-over when I landed. ;) You might want to restore that. I didn't try to match sink rate to real, I only tried to get the speed range within reasonable norms and bring control surfaces effects to something that felt reasonable. You might want to mess with the spoiler settings, maybe increase the drag a bit, as the handbook says they're pretty effective, and I tend to err on the understrength side. I'm not a pilot, so definitely feel free to disregard anything I did. -Gary, aka Buckaroo -- uberSVN's rich system and user administration capabilities and model configuration take the hassle out of deploying and managing Subversion and the tools developers use with it. Learn more about uberSVN and get a free download at: http://p.sf.net/sfu/wandisco-dev2dev ___ Flightgear-devel mailing list Flightgear-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/flightgear-devel
Re: [Flightgear-devel] New aircraft: SF-25
Hi, the correct cg for a SF25C is 0.143 .. 0.334m behind the wings tip (measured 0.52m from the center line). Regards, Maik am 15.08.2011 22:07 schrieb TDO_Brandano -: BTW, you can get a pretty good idea of where the CG is on a plane from the landing gear position. On a tail dragger the CG will be slightly behind the main wheel. Too far back and the tail won't have enough authority to lift for takeoff, too far forward and the plane will nose over when braking, or ground loop when rolling on the ground. In this specific model it might be a little further back than most, since it has to keep the tail on the ground with the weight of the passengers. I believe the CG will be approximatively coincident with the pilot position, since in a motorglider that will be the largest variable mass. > Date: Mon, 15 Aug 2011 13:18:53 -0400 > From: grne...@gmail.com > To: flightgear-devel@lists.sourceforge.net > Subject: Re: [Flightgear-devel] New aircraft: SF-25 > > On Mon, Aug 15, 2011 at 12:18 PM, Viktor Radnai wrote: > > Hi all, > > > > Athanasios Goritsas (cc-d) created a nice Falke 3D model with a basic > > Yasim profile, based on the aircraft he flew with. I would like to > > develop his model further (I'm doing my PPL on the real thing atm). We > > would both like to see it in Git (under a GPL license), maybe more > > people would join in developing it further. (If you need a statement on > > this directly from Athanasios, as he's the primary author, let us know.) > > > > In the meantime, could you please check out the plane and shed some > > light to some Yasim parameters. You can grab it from > > http://www.avatarzenekar.hu/files/sf25b.tar.bz2 > > > > The biggest issue with the FDM is that the plane does not seem to have > > enough drag -- it easily goes over Vne, and it's impossible to land > > without spoilers unless you stop the engine (and even then it takes > > forever). Compared to the Grob 109, I had to use an absolutely huge drag > > multiplier to force the bird down (150 instead of 2.5). 150 is probably > > a bit much -- maybe 100-120 would be enough, but I think the airframe or > > the wings are just not generating enough drag. > > > > Not sure if I did a good enough job with the fixed prop. The diameter > > should be correct, not sure about the rest. My school's falke has the 2L > > engine and it spins up to about 2600 when stopped. No idea about the > > prop's most efficient speed and horsepower values are pretty much guesses. > > > > Anyway, please let us know if this is good enough to go into the repo, > > and any suggestions for improvement. Some (working) 3D instrument panel > > would be great, but I have no idea how to make that. Any pointers on > > that would be very much appreciated. Since Falkes have fairly varying > > instrumentation, even a copy of the Grob 109's panel could be OK. > > > > Ah, and the splash screens I've made do not load. What did I do wrong? > > > > Thanks in advance. > > > > Cheers, > > Vik > > > Vik, > > Looks like a great start. The first thing I would do before anything > else is make sure your CG is positioned reasonably. In your SF-25, the > CG is much too far back; given the forward-swept wings, it looks to be > about a meter behind MAC: > > E:\FlightGear projects\sf25b>yasim sf25b-yasim.xml > Solution results: Iterations: 1292 > Drag Coefficient: 10.955851 > Lift Ratio: 291.677826 > Cruise AoA: 1.469686 > Tail Incidence: 2.793443 > Approach Elevator: -0.014301 > CG: x:-0.900, y:-0.000, z:0.284 > > Inertia tensor : 1831.357, -0.000, 78.171 > [kg*m^2] -0.000, 2075.542, 0.000 > Origo at CG 78.171, 0.000, 3856.738 > > The command-line YASim solver is showing CG at x=-0.9, well behind the > wing's root chord position at x="-0.371". > > It isn't worth messing with other YASim values until CG is about > right. I'd first try to locate the real CG range from a certification > sheet or pilot's handbook and then use a YASim element to > shift some of the plane's mass forward toward the nose. Once you get > CG better positioned, you'll have much better luck with other factors. > > After CG, a couple of other things to watch in the solver: Lift ratio > is very high-- this indicates the glides-forever issue. For this plane > I'm guessing you'll want a value somewhere between 100-130, but the > actual value will depend on flight experimentation. Lots of YASim > parameters affect that value. (Note that these YASim drag and lift > numbers should not be treated as real lift/drag ratios; don't try to
Re: [Flightgear-devel] New aircraft: SF-25
BTW, you can get a pretty good idea of where the CG is on a plane from the landing gear position. On a tail dragger the CG will be slightly behind the main wheel. Too far back and the tail won't have enough authority to lift for takeoff, too far forward and the plane will nose over when braking, or ground loop when rolling on the ground. In this specific model it might be a little further back than most, since it has to keep the tail on the ground with the weight of the passengers. I believe the CG will be approximatively coincident with the pilot position, since in a motorglider that will be the largest variable mass. > Date: Mon, 15 Aug 2011 13:18:53 -0400 > From: grne...@gmail.com > To: flightgear-devel@lists.sourceforge.net > Subject: Re: [Flightgear-devel] New aircraft: SF-25 > > On Mon, Aug 15, 2011 at 12:18 PM, Viktor Radnai > wrote: > > Hi all, > > > > Athanasios Goritsas (cc-d) created a nice Falke 3D model with a basic > > Yasim profile, based on the aircraft he flew with. I would like to > > develop his model further (I'm doing my PPL on the real thing atm). We > > would both like to see it in Git (under a GPL license), maybe more > > people would join in developing it further. (If you need a statement on > > this directly from Athanasios, as he's the primary author, let us know.) > > > > In the meantime, could you please check out the plane and shed some > > light to some Yasim parameters. You can grab it from > > http://www.avatarzenekar.hu/files/sf25b.tar.bz2 > > > > The biggest issue with the FDM is that the plane does not seem to have > > enough drag -- it easily goes over Vne, and it's impossible to land > > without spoilers unless you stop the engine (and even then it takes > > forever). Compared to the Grob 109, I had to use an absolutely huge drag > > multiplier to force the bird down (150 instead of 2.5). 150 is probably > > a bit much -- maybe 100-120 would be enough, but I think the airframe or > > the wings are just not generating enough drag. > > > > Not sure if I did a good enough job with the fixed prop. The diameter > > should be correct, not sure about the rest. My school's falke has the 2L > > engine and it spins up to about 2600 when stopped. No idea about the > > prop's most efficient speed and horsepower values are pretty much guesses. > > > > Anyway, please let us know if this is good enough to go into the repo, > > and any suggestions for improvement. Some (working) 3D instrument panel > > would be great, but I have no idea how to make that. Any pointers on > > that would be very much appreciated. Since Falkes have fairly varying > > instrumentation, even a copy of the Grob 109's panel could be OK. > > > > Ah, and the splash screens I've made do not load. What did I do wrong? > > > > Thanks in advance. > > > > Cheers, > > Vik > > > Vik, > > Looks like a great start. The first thing I would do before anything > else is make sure your CG is positioned reasonably. In your SF-25, the > CG is much too far back; given the forward-swept wings, it looks to be > about a meter behind MAC: > > E:\FlightGear projects\sf25b>yasim sf25b-yasim.xml > Solution results: Iterations: 1292 > Drag Coefficient: 10.955851 >Lift Ratio: 291.677826 >Cruise AoA: 1.469686 >Tail Incidence: 2.793443 > Approach Elevator: -0.014301 >CG: x:-0.900, y:-0.000, z:0.284 > > Inertia tensor : 1831.357, -0.000, 78.171 > [kg*m^2] -0.000, 2075.542, 0.000 > Origo at CG 78.171, 0.000, 3856.738 > > The command-line YASim solver is showing CG at x=-0.9, well behind the > wing's root chord position at x="-0.371". > > It isn't worth messing with other YASim values until CG is about > right. I'd first try to locate the real CG range from a certification > sheet or pilot's handbook and then use a YASim element to > shift some of the plane's mass forward toward the nose. Once you get > CG better positioned, you'll have much better luck with other factors. > > After CG, a couple of other things to watch in the solver: Lift ratio > is very high-- this indicates the glides-forever issue. For this plane > I'm guessing you'll want a value somewhere between 100-130, but the > actual value will depend on flight experimentation. Lots of YASim > parameters affect that value. (Note that these YASim drag and lift > numbers should not be treated as real lift/drag ratios; don't try to > make them match a real L/D ratio.) Approach elevator is much too > small-- this value means you'll need alm
Re: [Flightgear-devel] New aircraft: SF-25
On Mon, Aug 15, 2011 at 12:18 PM, Viktor Radnai wrote: > Hi all, > > Athanasios Goritsas (cc-d) created a nice Falke 3D model with a basic > Yasim profile, based on the aircraft he flew with. I would like to > develop his model further (I'm doing my PPL on the real thing atm). We > would both like to see it in Git (under a GPL license), maybe more > people would join in developing it further. (If you need a statement on > this directly from Athanasios, as he's the primary author, let us know.) > > In the meantime, could you please check out the plane and shed some > light to some Yasim parameters. You can grab it from > http://www.avatarzenekar.hu/files/sf25b.tar.bz2 > > The biggest issue with the FDM is that the plane does not seem to have > enough drag -- it easily goes over Vne, and it's impossible to land > without spoilers unless you stop the engine (and even then it takes > forever). Compared to the Grob 109, I had to use an absolutely huge drag > multiplier to force the bird down (150 instead of 2.5). 150 is probably > a bit much -- maybe 100-120 would be enough, but I think the airframe or > the wings are just not generating enough drag. > > Not sure if I did a good enough job with the fixed prop. The diameter > should be correct, not sure about the rest. My school's falke has the 2L > engine and it spins up to about 2600 when stopped. No idea about the > prop's most efficient speed and horsepower values are pretty much guesses. > > Anyway, please let us know if this is good enough to go into the repo, > and any suggestions for improvement. Some (working) 3D instrument panel > would be great, but I have no idea how to make that. Any pointers on > that would be very much appreciated. Since Falkes have fairly varying > instrumentation, even a copy of the Grob 109's panel could be OK. > > Ah, and the splash screens I've made do not load. What did I do wrong? > > Thanks in advance. > > Cheers, > Vik Vik, Looks like a great start. The first thing I would do before anything else is make sure your CG is positioned reasonably. In your SF-25, the CG is much too far back; given the forward-swept wings, it looks to be about a meter behind MAC: E:\FlightGear projects\sf25b>yasim sf25b-yasim.xml Solution results: Iterations: 1292 Drag Coefficient: 10.955851 Lift Ratio: 291.677826 Cruise AoA: 1.469686 Tail Incidence: 2.793443 Approach Elevator: -0.014301 CG: x:-0.900, y:-0.000, z:0.284 Inertia tensor : 1831.357, -0.000, 78.171 [kg*m^2] -0.000, 2075.542, 0.000 Origo at CG 78.171, 0.000, 3856.738 The command-line YASim solver is showing CG at x=-0.9, well behind the wing's root chord position at x="-0.371". It isn't worth messing with other YASim values until CG is about right. I'd first try to locate the real CG range from a certification sheet or pilot's handbook and then use a YASim element to shift some of the plane's mass forward toward the nose. Once you get CG better positioned, you'll have much better luck with other factors. After CG, a couple of other things to watch in the solver: Lift ratio is very high-- this indicates the glides-forever issue. For this plane I'm guessing you'll want a value somewhere between 100-130, but the actual value will depend on flight experimentation. Lots of YASim parameters affect that value. (Note that these YASim drag and lift numbers should not be treated as real lift/drag ratios; don't try to make them match a real L/D ratio.) Approach elevator is much too small-- this value means you'll need almost no elevator to hold an approach. Look for something in the -0.7 to -0.9 range for starters. In any case, don't try to tweak these until CG is resolved. Wing and hstab stall AoA values look really high at 30 degrees. Most conventional high-lift general aviation airfoils seem to be in the 15-18 range. If you know the airfoils used, you can get camber and stall values from the airfoil data. I have a little and rather incomplete YASim guide that might be helpful: http://ltts.crlt.indiana.edu/grn/flightgear/ -Gary, aka Buckaroo -- uberSVN's rich system and user administration capabilities and model configuration take the hassle out of deploying and managing Subversion and the tools developers use with it. Learn more about uberSVN and get a free download at: http://p.sf.net/sfu/wandisco-dev2dev ___ Flightgear-devel mailing list Flightgear-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/flightgear-devel
[Flightgear-devel] New aircraft: SF-25
Hi all, Athanasios Goritsas (cc-d) created a nice Falke 3D model with a basic Yasim profile, based on the aircraft he flew with. I would like to develop his model further (I'm doing my PPL on the real thing atm). We would both like to see it in Git (under a GPL license), maybe more people would join in developing it further. (If you need a statement on this directly from Athanasios, as he's the primary author, let us know.) In the meantime, could you please check out the plane and shed some light to some Yasim parameters. You can grab it from http://www.avatarzenekar.hu/files/sf25b.tar.bz2 The biggest issue with the FDM is that the plane does not seem to have enough drag -- it easily goes over Vne, and it's impossible to land without spoilers unless you stop the engine (and even then it takes forever). Compared to the Grob 109, I had to use an absolutely huge drag multiplier to force the bird down (150 instead of 2.5). 150 is probably a bit much -- maybe 100-120 would be enough, but I think the airframe or the wings are just not generating enough drag. Not sure if I did a good enough job with the fixed prop. The diameter should be correct, not sure about the rest. My school's falke has the 2L engine and it spins up to about 2600 when stopped. No idea about the prop's most efficient speed and horsepower values are pretty much guesses. Anyway, please let us know if this is good enough to go into the repo, and any suggestions for improvement. Some (working) 3D instrument panel would be great, but I have no idea how to make that. Any pointers on that would be very much appreciated. Since Falkes have fairly varying instrumentation, even a copy of the Grob 109's panel could be OK. Ah, and the splash screens I've made do not load. What did I do wrong? Thanks in advance. Cheers, Vik -- uberSVN's rich system and user administration capabilities and model configuration take the hassle out of deploying and managing Subversion and the tools developers use with it. Learn more about uberSVN and get a free download at: http://p.sf.net/sfu/wandisco-dev2dev ___ Flightgear-devel mailing list Flightgear-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/flightgear-devel
