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Guest RichD

Flight Dynamics for Dummies

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I would like to make some minor changes to the Mooney to increase the power and improve the pitch stability. I am looking at the Aircraft.cfg file and I wonder if changing some of the settings would help. I know next to nothing about flight dynamics. Any experts out there who can point me in the right direction. I am willing to spend time testing and changing things but I would like to be sure that any changes I make won't screw something else up. For example I changed the power scalar and that gave me the correct top speed but the climb rate is now too high. I just need a few basics to start with and I'll take it from there. Thanks Richard

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First, you should be certain that you understand what the terms really mean so that you can set things "correctly". In which sim are you working? In Fs02, the Mooney is pretty close to real specs though it was some time ago that I messed with it.When you test it against a cruise spec, you should realize that that spec applies 1) only in standard conditions, 2) generally at or close to max gross weight, 3) only at a specific altitude. This is not made clear in all the publications that give specs. Here's what I mean. At its gross weight of 3,368 lbs, the Bravo should fly at 214 KTAS (knots true airspeed) at 25,000 ft when set at 89% power and leaned for best economy. At 10,000 ft it should fly at 188 KTAS at the same power. In this case, 89% power probably means full throttle, prop at 2400 rpm and leaned for just under max fuel flow toward the rich side. Achieveing this is takes some work. First, it can only be achieved quickly using the autopilot. Second the climb to altitude must be made with careful leaning for max fuel flow at 1000 ft intervals above 3000 ft. At cruise altitude you aould let the autopilot level off and then lean first for max fuel flow and then lean a bit for max safe turbine inlet temperature. The TLS originally carried a max turbine inlet temperature spec of 1750 degrees while most other users of the same type of engine used 1650 degrees. The TLS engines had a shortened life but they gave speeds up to 220 KTAS. A max cruise of 75% is recommended by Lycoming for all other applications of its engines. The Bravo manual calls for leaning to 1650 degrees. So you should see 214 KTAS but only if you take the time to climb to 25,000 ft and then lean properly, flying on autopilot.(I wish I could abbreviate turbine inlet temperature but this Forum won't let me!)At a more common condition - about 3150 lbs and 17,500 feet with power set at 33 inches mp and 2400 rpm, you should see 200 KTAS and 17.5 gph.My approach to getting an aircraft to match a spec is to tune the parasite drag scalar in the aircraft.cfg file. You should not need to touch the engine parameters as they are usually done correctly. But I frequently encounter aircraft models that need a little drag touch up.The following is cut from my own FS02 Mooney Bravo aircraft.cfg file:[flight_tuning]cruise_lift_scalar=1.0parasite_drag_scalar=0.95induced_drag_scalar=1.0elevator_effectiveness=1.0aileron_effectiveness=1.0rudder_effectiveness=1.0pitch_stability=1.0roll_stability=1.0yaw_stability=1.0elevator_trim_effectiveness=1.0aileron_trim_effectiveness=1.0rudder_trim_effectiveness=1.0Note that I have reduced parasite drag using the factor 0.95. I think this is sufficient to meet the cruise specs listed above.Not all aircraft.cfg files include this [Flight tuning] section. But, if they don't you can copy it in from the file of any other aircraft and adjust it accordingly. heck, you can copy this section and paste it into the aircraft.cfg text file.If you are talking about the FS9 model, that's one I have not tried. But, as noted elsewhere in this Forum, it may be slow. The fix is to compare cruise speeds between FS02 and FS9 and use the square of the speed ratio as the factor for parasite drag in the FS9 file. (Or in this case, multiply that factor times the 0.95 that already exists in the FS02 version.)What you want is a plane that not only flies at the correct speed but also uses the correct fuel consumption. in this case I left the fuel flow scalar at 1.0 meaning the engine parameters are good as they are. You would mess this up by using a power factor.

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Thanks for the quick reply. That is the kind of information I was looking for. Something to get started.Thanks AgainRichard

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