Re: [Flightgear-devel] My Flight in a B-1B Flight Simulator at Dyess AFB
Cameron Moore wrote: Everyone in my office it tired of hearing about it, so I thought I'd turn to you guys. I had a chance to go fly in a B-1B flight simulator as part of a tour at Dyess AFB today. (See below for some links[1] to Wow, a full size B-1 simulator. Now *that* must be impressive! Anyway, it was a fun trip. If any of you ever get a chance to climb into a big sim like this, go for it. Merry Christmas! I second that. Every time I get a chance to step into one of those simulators I have a great time. It's definitely worth it. Erik [1] http://www.kgwings.com/fieldtrips/dyess/sim1.JPG http://www.kgwings.com/fieldtrips/dyess/sim2.JPG http://www.kgwings.com/fieldtrips/dyess/b1sim.JPG ___ Flightgear-devel mailing list [EMAIL PROTECTED] http://mail.flightgear.org/mailman/listinfo/flightgear-devel
Re: [Flightgear-devel] My Flight in a B-1B Flight Simulator at Dyess AFB
After that I went to met up with a fuel tanker to try and refuel. Trying to hook up with the tanker was the most challenging part of the experience. I spent what felt like 10 minutes trying to speedup, slowdown, noseup, nosedown, left, right until I gave up. I've only refueled in 707's, but: Everybody has trouble at first, but aileron and elevator response are almost instantaneous, and the control surfaces are sized and scheduled to give a certain amount of roll or pitch rate, so that's probably not where the delay comes from. When it comes to roll control the main problem is the receiving airplane's interaction with the wingtip vortices from the tanker. I don't know if their simulator models this effect. If it does, it could be mistaken for lack of roll response. Elevator response is not a problem usually. In fact, it's usually too touchy at first because the CG has moved aft as fuel was burned prior to refueling. As you take on fuel the CG moves forward and the pitch control becomes less sensitive. I don't know if swing-wing airplanes do this, as they have their own bag of CG problems and solutions. Speed response is pretty slow due to the airplane's inertia and the engines' spool-up time. The problem gets worse as the receiving airplane gets heavier. The interaction of the above may cause one or more channels in your brain to drop out for a second, which could also be perceived as slow response. This also happens when you first try to learn an instrument scan. You can practice refueling to some extent in FlightGear using the AI tanker. There is an annoying problem though, in that as you get close to the tanker it appears to jump in 30-foot leaps (so you can't *really* practice refueling). Also, we don't model downwash, wingtip vortices, weight change, and CG travel. Dave -- David Culp davidculp2[at]comcast.net ___ Flightgear-devel mailing list [EMAIL PROTECTED] http://mail.flightgear.org/mailman/listinfo/flightgear-devel
Re: [Flightgear-devel] My Flight in a B-1B Flight Simulator at Dyess AFB
David Culp wrote: You can practice refueling to some extent in FlightGear using the AI tanker. There is an annoying problem though, in that as you get close to the tanker it appears to jump in 30-foot leaps (so you can't *really* practice refueling). That sounds like a bug. My reading of the AI code indicates that motion should be continuous, no? Also, we don't model downwash, wingtip vortices, weight change, and CG travel. Actually, weight change and CG travel due to fuel load *are* modelled. With YASim, at least, there is currently no way to get the new fuel state into the FDM (it wants to own the fuel load instead of reading it out of the property tree). But that's a really easy thing to fix if someone wants to work on this. Andy ___ Flightgear-devel mailing list [EMAIL PROTECTED] http://mail.flightgear.org/mailman/listinfo/flightgear-devel
Re: [Flightgear-devel] My Flight in a B-1B Flight Simulator at Dyess AFB
One question though. I mentioned trying to line up with a fuel tanker and how the delayed movement was throwing me off. My guess is that this behavior was due to slow control surface movements. My question is if JSBSim simulates control surface movement speeds (excluding the flaps which do) or is the control surface deflection always exactly equal to the control input? I think It has more to do with moving multiple tons of steel and aluminum with a tiny little control surface. g. ___ Flightgear-devel mailing list [EMAIL PROTECTED] http://mail.flightgear.org/mailman/listinfo/flightgear-devel
Re: [Flightgear-devel] My Flight in a B-1B Flight Simulator at Dyess AFB
You can practice refueling to some extent in FlightGear using the AI tanker. There is an annoying problem though, in that as you get close to the tanker it appears to jump in 30-foot leaps (so you can't *really* practice refueling). That sounds like a bug. My reading of the AI code indicates that motion should be continuous, no? I'm not sure where the problem is. I know very little about the graphics side of things. This would be a nice problem to solve, because formation flying is not possible yet. The AI airplane does move in discreet steps (once per sim tic) as does the user's view point, I assume. I guess they aren't drawn at the same tic? Also, we don't model downwash, wingtip vortices, weight change, and CG travel. Actually, weight change and CG travel due to fuel load *are* modelled. With YASim, at least, there is currently no way to get the new fuel state into the FDM (it wants to own the fuel load instead of reading it out of the property tree). But that's a really easy thing to fix if someone wants to work on this. That would be a good thing.I've been wondering how to let the receiver know that it is in position and can start downloading fuel. In the real world, the tanker has a box behind it which contains all possible positions of the fuel nozzle. If the position of the receiver's receptacle is within the box, then fueling can occur. Dave -- David Culp davidculp2[at]comcast.net ___ Flightgear-devel mailing list [EMAIL PROTECTED] http://mail.flightgear.org/mailman/listinfo/flightgear-devel
Re: [Flightgear-devel] My Flight in a B-1B Flight Simulator at Dyess AFB
On Wednesday 24 December 2003 16:53, David Culp wrote: After that I went to met up with a fuel tanker to try and refuel. Trying to hook up with the tanker was the most challenging part of the experience. I spent what felt like 10 minutes trying to speedup, slowdown, noseup, nosedown, left, right until I gave up. I've only refueled in 707's, but: Everybody has trouble at first, but aileron and elevator response are almost instantaneous, and the control surfaces are sized and scheduled to give a certain amount of roll or pitch rate, so that's probably not where the delay comes from. When it comes to roll control the main problem is the receiving airplane's interaction with the wingtip vortices from the tanker. I don't know if their simulator models this effect. If it does, it could be mistaken for lack of roll response. Elevator response is not a problem usually. In fact, it's usually too touchy at first because the CG has moved aft as fuel was burned prior to refueling. As you take on fuel the CG moves forward and the pitch control becomes less sensitive. I don't know if swing-wing airplanes do this, as they have their own bag of CG problems and solutions. Speed response is pretty slow due to the airplane's inertia and the engines' spool-up time. The problem gets worse as the receiving airplane gets heavier. The interaction of the above may cause one or more channels in your brain to drop out for a second, which could also be perceived as slow response. This also happens when you first try to learn an instrument scan. You can practice refueling to some extent in FlightGear using the AI tanker. There is an annoying problem though, in that as you get close to the tanker it appears to jump in 30-foot leaps (so you can't *really* practice refueling). Also, we don't model downwash, wingtip vortices, weight change, and CG travel. Dave -- David Culp davidculp2[at]comcast.net I've been wondering if that could be smoothed a bit by using a running average instead of using the raw data as it comes in. This would introduce a degree of lag, of course, depending on the data rate and number of samples. Considering that at close ranges it's pretty unusable, a half-second or less lag - say ten samples at a sample rate of 30/sec - might be acceptable. Just a thought, of course:) Happy xmas all. LeeE ___ Flightgear-devel mailing list [EMAIL PROTECTED] http://mail.flightgear.org/mailman/listinfo/flightgear-devel
Re: [Flightgear-devel] My Flight in a B-1B Flight Simulator at Dyess AFB
On Wed, 2003-12-24 at 05:51, David Megginson wrote: Cameron Moore wrote: One question though. I mentioned trying to line up with a fuel tanker and how the delayed movement was throwing me off. My guess is that this behavior was due to slow control surface movements. My question is if JSBSim simulates control surface movement speeds (excluding the flaps which do) or is the control surface deflection always exactly equal to the control input? Hinge moments for control surfaces probably have something to do with it, but remember also that you're flying a heavy, fast plane. Even if the plane is very responsive to control input (which has more to do with aerodynamic damping effects than control-surface response speed), you're not going to be able to change the flight path on a dime. All other things being equal, a plane that flies twice as fast (say, because of heavy wing-loading) needs twice as much time and four times as much space to make a change in its flight path -- that's why a little Cessna or Piper can start its landing flare over the runway itself, while a transport jet has to start flaring at least a half mile back (pulling up the nose at the last moment would only change the attitude in which the jet smashed into the runway). Airliners aren't that sluggish ... the flare is initiated below 50 ft AGL and that is definitely over the runway. Jet fighters turn fast only by pulling ridiculously high G-forces, and even then, they need a lot of time and space to turn around. I'm sure that inertia has a lot to do with it as well, but I don't know enough about physics to describe those effects. Inertia is a player, but most aircraft do not have large roll moments of inertia .. the mass tends to be concentrated close to the roll axis. All the best, David ___ Flightgear-devel mailing list [EMAIL PROTECTED] http://mail.flightgear.org/mailman/listinfo/flightgear-devel -- Tony Peden [EMAIL PROTECTED] ___ Flightgear-devel mailing list [EMAIL PROTECTED] http://mail.flightgear.org/mailman/listinfo/flightgear-devel
Re: [Flightgear-devel] My Flight in a B-1B Flight Simulator at Dyess AFB
Tony Peden wrote: Airliners aren't that sluggish ... the flare is initiated below 50 ft AGL and that is definitely over the runway. I guess that brings us back to the old discussion about round-out vs. flare (U.S. books seem to distinguish the two). The jets are are nose-high and slowing about 1/2 mile back, whatever you want to call that, while the single-engine props are sometimes still nose-low at full approach speed when they cross the runway threshold. Inertia is a player, but most aircraft do not have large roll moments of inertia .. the mass tends to be concentrated close to the roll axis. I'm thinking of the effect of inertia on changing the flight path, not on changing the orientation. I obviously have no real-life experience, but I imagine that the hard part of an in-air refueling is getting the plane into the right place relative to the tanker and keeping it there, which involves modifying the plane's velocity and path of flight rather than simply its pitch and roll. I understand how velocity affects that (a plane twice as fast needs twice the time and four times the space to make the same change in direction with the same load factor), but I don't understand how inertia plays into it. All the best, and happy holidays to everyone, David ___ Flightgear-devel mailing list [EMAIL PROTECTED] http://mail.flightgear.org/mailman/listinfo/flightgear-devel
Re: [Flightgear-devel] My Flight in a B-1B Flight Simulator at Dyess AFB
On Wed, 2003-12-24 at 17:53, David Megginson wrote: Tony Peden wrote: Airliners aren't that sluggish ... the flare is initiated below 50 ft AGL and that is definitely over the runway. I guess that brings us back to the old discussion about round-out vs. flare (U.S. books seem to distinguish the two). The jets are are nose-high and slowing about 1/2 mile back, whatever you want to call that, while the single-engine props are sometimes still nose-low at full approach speed when they cross the runway threshold. The nose up attitude is, I suspect, nothing more than a product of the angle of attack needed to fly at 1.3-1.4 times the stall speed. Procedures wise, though, once you are at landing flaps and trimmed on glideslope and final approach speed (which could be at the outer marker) the pilot would, on an ideal day, maintain speed and attitude all the way to the flare. Inertia is a player, but most aircraft do not have large roll moments of inertia .. the mass tends to be concentrated close to the roll axis. I'm thinking of the effect of inertia on changing the flight path, not on changing the orientation. I obviously have no real-life experience, but I imagine that the hard part of an in-air refueling is getting the plane into the right place relative to the tanker and keeping it there, which involves modifying the plane's velocity and path of flight rather than simply its pitch and roll. I understand how velocity affects that (a plane twice as fast needs twice the time and four times the space to make the same change in direction with the same load factor), but I don't understand how inertia plays into it. All the best, and happy holidays to everyone, David ___ Flightgear-devel mailing list [EMAIL PROTECTED] http://mail.flightgear.org/mailman/listinfo/flightgear-devel -- Tony Peden [EMAIL PROTECTED] ___ Flightgear-devel mailing list [EMAIL PROTECTED] http://mail.flightgear.org/mailman/listinfo/flightgear-devel
[Flightgear-devel] My Flight in a B-1B Flight Simulator at Dyess AFB
Everyone in my office it tired of hearing about it, so I thought I'd turn to you guys. I had a chance to go fly in a B-1B flight simulator as part of a tour at Dyess AFB today. (See below for some links[1] to images on someone else's website -- I forgot to take my camera.) As you can see from the pictures, it is a full-motion simulator (made by Boeing). The tour was given by a friend, Lt. Col. Baron, that is a B-1 Flight Instructor. He took myself and two other men for the morning in the sim and a little tour of a stationary B-1B and the control tower. My time in the sim went something like this: I started after another person had landed; I was at the end of the runway facing the wrong way. Added full right rudder and about half throttle to turn around at the end of the runway (it took a few seconds before it actually started moving). The aircraft didn't turn well at all although I was pushing the right rudder all the way forward -- Baron said it was probably a glitch in the sim. Anyway, I finally got turned around, went full afterburners, and took off without incident. Got to about 2000ft and did a couple barrel rolls while breaking the sound barrier. :-) After that I went to met up with a fuel tanker to try and refuel. Trying to hook up with the tanker was the most challenging part of the experience. I spent what felt like 10 minutes trying to speedup, slowdown, noseup, nosedown, left, right until I gave up. Lt. Col. Baron said it's 90% anticipation. I think with more practice I could do it. Part of my problem was that I would overcorrect since there was a delay between my stick commands and the actual movement of the B-1; by the time I had the aircraft going were I thought I needed to be going and recentered the stick, I had already held it too long. I could feel it happening, but couldn't get the hang of it. I wanted to stay there until I nailed it, but due to time constraints, I just gave up. Anyway, after fighting with the tanker a while, I went back for an ILS approach at Dyess. Lt. Col. Baron set me up with a 200ft ceiling, so I was flying through nothing but clouds until I went below 200ft. I punched through the clouds right in front of the runway and brought her down nicely. (woohoo!) I was flying completely off the digital HUD displays. The display had a little cross target that you wanted to put your center on, and it would guide you down for a perfect landing. It was a lot easier than I anticipated -- the computer definately made it easier on me. That concluded my flight, but the next guy did a lot of the same stuff, only he did his landing at night with a 200ft ceiling. Very cool! Now on to what you guys really want to know... What was the sim like? Well, it was extremely impressive. The physical hardware of the simulator was awesome. The instruments and controls and everything were very cool and realistic. The flight stick was much stiffer than I expected, and I had to use a lot more muscle than I would have thought. Lt. Col. Baron said that the flight stick in a real B-1 was a little easier to handle but also a little more sensitive. Oh, I finally figured out what I want for Christmas while I was there -- some rudder pedals for my PC. Having never flown in a real cockpit before, it was my first experience with rudder pedals, and I loved them. Anyway... As for the software side of the sim, it looked and felt a lot like FlightGear+JSBSim. There were some bugs: visual artifacts like faraway tiles flashing yellow and the friction coefs on the gear were to high according to Baron (while taxiing if you throttle back to idle, the aircraft would stop rather quickly. Baron said in a real B-1 it would continue to roll a lot further). The terrain around Dyess (which is were we flew) is mostly flat, so I couldn't really tell how well the terrain data was, but it's looked comparable to FGs. They had random trees scattered around pretty much like FG does based on land cover data. They had the major roads modeled like FG (or did we ever add that to the base scenary?) -- it looked like it came from the same datasource as ours but I'm not positive. Their airbase and neighboring cities definately looked better than FG's simply because they had actually spent time adding models for various things (like hangars, control towers, water towers, major buildings in nearby Abilene, cellular and radios towers, etc). I thought our textures were better though. It's been a while since I've actually ran FG so I don't know how the night lighting compares to ours; I'll have to compile FG sometime and see. One thing I thought was cool was that during the night approach in the clouds, every second or so everything would flash white. It was due to the external lights flashing and bouncing off the clouds. It was a nice effect, but I'm not sure how accurate it was. Overall, I thought FG stacked up very well against the software side of this simulator. We obviously can't touch
RE: [Flightgear-devel] My Flight in a B-1B Flight Simulator at Dyess AFB
As for the software side of the sim, it looked and felt a lot like FlightGear+JSBSim. There were some bugs: Hmmm... ;-) Jon ___ Flightgear-devel mailing list [EMAIL PROTECTED] http://mail.flightgear.org/mailman/listinfo/flightgear-devel
Re: [Flightgear-devel] My Flight in a B-1B Flight Simulator at Dyess AFB
On Wednesday 24 December 2003 01:17, Cameron Moore wrote: Everyone in my office it tired of hearing about it, so I thought I'd turn to you guys. Nice story. I always like reading about people on this mailinglist flying real aircraft or high-end sims and comparing (some of) the experience to FlightGear. --Ivo ___ Flightgear-devel mailing list [EMAIL PROTECTED] http://mail.flightgear.org/mailman/listinfo/flightgear-devel
Re: [Flightgear-devel] My Flight in a B-1B Flight Simulator at Dyess AFB
* [EMAIL PROTECTED] (Jon Berndt) [2003.12.23 19:02]: As for the software side of the sim, it looked and felt a lot like FlightGear+JSBSim. There were some bugs: Hmmm... ;-) Hehe. I didn't mean to imply that JSBSim has bugs (though it does ;-). I meant that the handling was about the same in both. One question though. I mentioned trying to line up with a fuel tanker and how the delayed movement was throwing me off. My guess is that this behavior was due to slow control surface movements. My question is if JSBSim simulates control surface movement speeds (excluding the flaps which do) or is the control surface deflection always exactly equal to the control input? -- Cameron Moore [ Why is a carrot more orange than an orange? ] ___ Flightgear-devel mailing list [EMAIL PROTECTED] http://mail.flightgear.org/mailman/listinfo/flightgear-devel
