What N1 settings are required to get it moving, and will it taxi on idle thrust realistically. Captain Sim 727 taxi's amazingly real. Please can you make the 737 do the same, really makes it a lot [email protected]

Hello, just curious about your notion about Captain's Sims 727 realism in this regard. First, do you know exactly how much thrust is needed to move any particular airliner? 757,737 or 727, and how does *weight* play a part in this? I know that to get a aircraft moving it takes much more thrust then to maintain a given taxi speed. Also, when you say how *real* the 727 is, do you go by a chart or somthing to know how much thrust is needed in every condition, like for a soft runway or for rain or snow on the runways?[h5]Best Wishes,Randy J. SmithSan Jose Ca[/h5][h3]" A little learning is a dangerous thing"[/h3] [h5]AMD XP 2200 |MUNCHKIN 512 DDR RAM |ECS[/b ][i] K7S5A MB[/i] |GF3 64 MEG @ 215/545|WIN XP PRO |MITSUBISHI DIAMOND PLUS 91 19"[/h5]

In 747 PS1.3 it takes 40% N1 to get the aircraft moving from a stand still, once the aircraft has started rolling the throttles are moved to idle to maintain the speed.Alex

Randy,>> do you go by a chart or somthing to know how much thrust is needed in every condition, like for a soft runway or for rain or snow on the runways?I have never seen such charts in any manuals, do they exist at all ? I could assume, the needed amount is somewhat memorized by crews.Mike

Well for a given weight and condition I can picture a *common* thrust setting, but if your aircraft is lightly loaded it will take less thrust to get it rolling. All I am saying is that we cannot just say that a 737 or any airliner will always move with a *certain* thrust level for all conditions. A 744 will move with 40% N1 but what if your heavy and on sloping runway? Or in snow? Or a headwind etc.[h5]Best Wishes,Randy J. SmithSan Jose Ca[/h5][h3]" A little learning is a dangerous thing"[/h3] [h5]AMD XP 2200 |MUNCHKIN 512 DDR RAM |ECS[/b ][i] K7S5A MB[/i] |GF3 64 MEG @ 215/545|WIN XP PRO |MITSUBISHI DIAMOND PLUS 91 19"[/h5]

Effects like runway sloping is beyond FS2002/4 since all runways are flat. Snow, rain - we can neglect it too, lets be serious. Wind - ok, how about if we neglect it too, again we are talking about the first order of approximation here. I don't think anyone ever achieved (or attempted) to achieve even this first order, so lets make some baby steps before we will run.So what is this first order of approximation ?Basic physics:thrust to get moving = W*fsthrust to keep moving = W*fdW = weight of the aircraftfs = coefficient of static rolling friction for the aircraft typefd = coefficient of dynamic rolling friction for the typeAlways fs > fd in our imperfect world.I am sure both coefficients can be obtained from some source but considerable digging may be required.Frankly it is so easy that Microsoft should give developers all the tools to do it - including selection of your own coefficients. If you have to resort to some sort of black magic to make friction work - it probably won't work right or will have other unwanted side effects. The ball is in MS court. They should fix it - it is about time.Michael J.

Well that's because there is a flaw in the code for friction/ground resistance, not that many have not tried to work around this, many have. It's in Microsoft's ballpark, but until they fix this *issue* we have to play David blain to make it work correctly. The reason I had brought up the real thrust factors was because it was claimed that the Captain Sim's 727 taxi thrust etc was *realistic* which is impossible because like you pointed out, real world conditions do not exist in the flight simulator world. I rest my case.[h5]Best Wishes,Randy J. SmithSan Jose Ca[/h5][h3]" A little learning is a dangerous thing"[/h3] [h5]AMD XP 2200 |MUNCHKIN 512 DDR RAM |ECS[/b ][i] K7S5A MB[/i] |GF3 64 MEG @ 215/545|WIN XP PRO |MITSUBISHI DIAMOND PLUS 91 19"[/h5]

Randy,we all know if someone uses the word "real" for FS, he doesn't mean the 100 million dollar sim in his living room. We don't have any slippery when wet in FS. Also you need no charts, which I still think don't exist at all. One can ask a pilot at pprune.org for the range of thrust needed to get the ball rolling and an approx speed range that particular plane holds with idle thrust.What Spilot was probably referring to was excessive N1 values (> 50%) for initial movement in some FS jets or excessive speeds then at idle thrust (some FS Airliners accelerate to > 30 kt). Anyway, thanks to the awesome work of Ron Freimuth et al. one can easily adjust it without affecting the flight performance. In the airfile in table 1506 you find thrust scalar vs corrected N1 and Mach No. values. Microsoft interpolates those between Mach 0.0 and Mach 0.9. The trick is to insert a new table at Mach 0.1 (64 kt, does not affect flight performance) to have that interpolation take place between Mach 0.1 and Mach 0.9 then. Then you can safely reduce the thrust scalar values for the lower CN1 values in the Mach 0.0 table. Took me a half hour of work for each airliner I use to have them e.g. start rolling at 40% N1 and then roll with 10-12 kt (or 15 or whatever you want) at idle thrust. No more ride the brakes hot :)Someone has already uploaded such a correction for the 767 to the AVSIM lib.If we can have it a BIT more "real" in FS, then why shall we not take it ? ;).Mike

Oh I love a good healthy friendly discussion! "we all know if someone uses the word "real" for FS, he doesn't mean the 100 million dollar sim in his living room." Well I don't claim to speak for all of us, nor do I *think* that a person who says *real* as regards to FS means a 100 million dollar Simulator. But you can be assured that when I use that wonderful little word, I do mean the 100% Washington built Boeing Aircraft. "We don't have any slippery when wet in FS" Well you're correct, we don't, but then again that's one of my points. "Also you need no charts, which I still think don't exist at all" I was really surprised you actually missed this one, of course there aren't any, it was an example of saying something from no facts, as I have shown, in the real world, a particular thrust/N1 setting does not work in every situation (you can see that FS would have to replicate every aspect to be considered *real* in any sense of the word, one of the many reasons why it's not FAA approved, but it's coming real close)."What Spilot was probably referring to was excessive N1 values (> 50%) for initial movement in some FS jets or excessive speeds then at idle thrust (some FS Airliners accelerate to > 30 kt)" Well, i would not assume to know what you think he *might have* been trying to say, only what he did say (by the way it's really a play on words LOL) but if you know Spilot, from what I have read from his posts, is that he does mean the real McCoy as a comparison, but it's better to let him speak for himself if we have miss-read his post in anyway. How one would get 50% out of what he said is beyond my abilities. Pun intended. [h5]Best Wishes,Randy J. SmithSan Jose Ca[/h5][h3]" A little learning is a dangerous thing"[/h3] [h5]AMD XP 2200 |MUNCHKIN 512 DDR RAM |ECS[/b ][i] K7S5A MB[/i] |GF3 64 MEG @ 215/545|WIN XP PRO |MITSUBISHI DIAMOND PLUS 91 19"[/h5]

Randy,you are reminding people to stay on the carpet regarding that nasty word "realism" in FS. That's absolutely fine ;). I have no doubt PMDG will get it right, so no need to discuss this any further.Mike

Yeah! We are on the same side of the fence Mike. I want the very best that PMDG can produce and also have extreme confidence like you my friend, that they will deliver the most advanced aircraft to date for Flight Simulator, we have some great times ahead of us, so lets always share and discuss issues here, heck, I might just learn something![h5]Best Wishes,Randy J. SmithSan Jose Ca[/h5][h3]" A little learning is a dangerous thing"[/h3] [h5]AMD XP 2200 |MUNCHKIN 512 DDR RAM |ECS[/b ][i] K7S5A MB[/i] |GF3 64 MEG @ 215/545|WIN XP PRO |MITSUBISHI DIAMOND PLUS 91 19"[/h5]

Well guys, I didn't start this post to create a argument, I just was asking a question. I meant that some a/c in FS need half throttle to get the a/c rolling. then about a quarter to keep it moving. I have a 727 manual and talked to various people and they said that it should roll when full about 40 percent n1 from a stop. Then idle thrust to taxi. When it is lightly loaded, the a/c will begin to roll at idle thrust when releasing the brakes. Pilots described that you would let the a/c get up to 15 knots and then get on the brakes and slow it down. Release it and get up to speed then brake. This way you weren't riding the brakes. Realistic? what is made on a computer that is 100% nothing that I know. I mean that is simulates it very good, or the best it can with the limitations of FS. Thanks you very much for the interest and I hope, the 737 will be accurate as much as it can be. [email protected]

You know Michael, I think you have hit on a fantastic idea, and I think we should take this subject on a slightly different tack. I don't pretend to understand how the fs2002 game engine works or how it simulates friction, but I have formulated some thoughts based on previous threads and my own programming knowledge.It seems to me that somewhere in this program, microsoft has hard-coded some value for the coefficient of friction. Perhaps, what MS developers should look into doing is not only modifying this to provide more realistic taxiing conditions, but also making it some sort of dynamic variable based on current conditions, etc. For example, if it's raining and speed > 120 kts then have a the coefficient set to provide very little friction due to tire hydroplaning (the same then applies to snow and icing conditions). This would make rudder steering imparative and wheel-braking almost non-existent (and the use of thrust reverse more important).So I guess to me, it seems that if Microsoft CAN fix the coefficient of friction then it is also feasible to provide different coefficients of friction based on aircraft/environmental conditions.Having said all of that, if the MS game engine doesn't use any real world physics (which I can hardly imaging that it doesn't considering the air files, aircraft.cfg, and flight dynamics) then this discussion is all rather moot anyways.RegardsJeff