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Guest georg

Rolling / friction during taxi (747)

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Guest georg

Hi,My question is based on the FS9 version of the 747 and maybe this issue is solved in FSX. I've always found it a bit weird that I have to add quite a remarkable amount of thrust to begin taxi and to keep up taxi speed. When idle is used, the plane slows down quite quickly even without the brakes. I happened to visit a 744F and I especially asked the pilot how much throttle you have to use for taxiing. He said that you maybe only add a little bit to begin moving and then you just go on idle. You may even have to use brakes to slow down even while idle, ofcourse depending on aircraft weight. They sometimes shut down one or two engines after landing and even then you may not need much more thrust. I know that FS might set its own limitations again but I know one well known 767 which has this quite well done. Is there perhaps something I could modify myself to improve it?Thanks!

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Do a search for sim.dll It fixes the friction issues within FS9 and makes the braking a little more realistic. been using it for years and it works well for me. But make sure you back up your old one!!Rob


Rob Prest

 

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Guest jumbojock

Hi GeorgeBraking amount depends on a number of factors, two of them All Up Weight, the other residual thrust. We fly 2 engine types, soon to be a third. At similar weights, the RR engines have less residual thrust and so once moving we still tend to use a little to keep going and turn corners. However, the P&Ws tend to be taxied with the thrust levers at idle once we're moving.Were you to close the thrust levers at heavy weights, you'd slow to a halt.David "jumbojock" Robertson

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The friction model is FS9 was certainly messed up, and everyone seemed to know it except MS. This is fixed in FSX.


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Georg- here's a benchmark from my setup.PMDG 747- CD vers. FS9 v1.0@ Gross Wt 600,000 - a throttle setting of N1 35.0 will maintain a steady roll of approx 15 Knots.Alex Reid

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I am not sure I understand what you mean "search for sim.dll" Are you talking about online or in FS9 directory? In my directory, I have sim1.dll. If the directory is what you are talking about, can you provide more information on what to look for or how you open the dll to correct the problem? Again, I am not sure I understand what you are explaining in order to correct the problem. I would apppreciate any help.Perry Fincher


Perry Fincher

CEO of Pan American Virtual

www.panamericanva.com

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Oh really? I haven't switched to FSX yet, but I always keep a lookout for improvements/changes and one day I guess I will switch over. Is the FSX ground friction really more realisticer than FS9?Hmmm...the day of the switch just got a little closer ;)Subin

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>Oh really? I haven't switched to FSX yet, but I always keep>a lookout for improvements/changes and one day I guess I will>switch over. Is the FSX ground friction really more>realisticer than FS9?>>Hmmm...the day of the switch just got a little closer ;)>>SubinThe groundbound dynamics of the FS9 PMDG 744 have been identified by the team themselves in the past as being a compromise imposed upon them by the inherent issues within FS9 itself. The replacement sim.dll file referred to alleviates the issue but introduces other inaccuracies as a result.I've become accustomed to it now but at first it was tricky to get a nice consistent taxi speed. My advice is to get her rolling, then make TINY adjustments to the thrust to maintain the speed, the better your throttle controller the easier this is. At much heavier weights (where the issue is most noticeable) I tend to get her rolling on the straight at about 14 knots with enough thrust to increase it gradually, then I tap the brakes to rein it in every 30 seconds.As for switching to FSX, only if you have a good machine, my friend! :-)


Mark Adeane - NZWN
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Guest georg

Thanks for all the help. I got the replacement sim1.dll and it really helps. Landing roll braking was also just fine and it didn't slow down so quickly if I didn't apply any braking.I have been trying to switch to FSX and although I think I have a good computer, I still can't use any complicated addons. I don't know what could be wrong. I've tuned graphics down as much as I have been able to and the result is still bad. Default planes are all ok, but addons cause a lot of trouble.

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Where did you get sim1.dll? I have done a bunch of searching but didn't find any usefull links that worked. The friction thing causes me serious agravation.


Tom Landry

 

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It used to be on the Avsim libray but had to be removed due to it being a hack. try searching on google but if you are really stuck I can zip it and mail it to you.Rob


Rob Prest

 

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Here's a poor man's tactic for tiny throttle adjustments.I made a 2" extension to my CH yoke throttle lever- the handles being a pair of plastic sewing thread spools. (vaguely similar in appearance to the two throttle knobs on a 737!)The extra lever length makes all the difference in making very small throttle adjustments.Alex Reid

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Found it! It seems to work well. Before I used to set the throttles to about 37% N1 just to maintian speed and it wasn't uncommon to go to 40%+ to get around corners. At two thirds fuel it only took about 32% N! to get moving and scrubbed little speed in the turns. My 767 move a little too freely but I tend to fly only one type of plane over a while so it is no big deal to go between the two .dlls Thanks for the help.


Tom Landry

 

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Remember also that 40% N1 is your max in the terminal area. For heavier weight takeoffs, it takes a bit of patience to get the bird rolling. You've got to get to about 5 knots before you start trying to turn, and it takes a while to get to 5 knots. With that said, I've found that about 32% N1 works at taxi speed (25 knots) on a 2/3rds fuel load. That percentage is always dependent upon what the taxi speed restrictions are, of course, as well as the weight. A good place to practice taxiing is SFO. 747s are allowed only 10 knots of taxi speed on the terminal side of the runway complex, so it makes for quite a challenge to find the correct thrust setting. After crossing the runways, you can go 25 knots (max on the 747).What I do is confirm again that the ground crew is clear, release brakes, then push 40% N1. I wait for it to build a few knots (Top left on the ND). Once I get to the taxi speed I want, I'll slowly throttle back until the number no longer moves. It takes a bit of guessing and experience to get it right, but even the FS9 model is workable in this manner. Soon it becomes easy to taxi, even when you have to slow down for the 10 knot, 90*+ turns. In that case, the friction model can be used to your advantage, rather than using the brakes.


I can't be in all places at once. If you see someone is having an issue with an Angle of Attack product, or something that should be brought to my attention, please message me. I want everyone to have a stellar experience with AOA. Thanks so much!

Chris Palmer

Founder/President

Angle of Attack

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