Modulus?

[nickpike 0]

Well, there you go, just the man to write a tutorial regerding Aerodynamics calculations.:-) Would you explain further,> Dynamic pressure, q, is a useful parameter for setting things that basically depend on it. Generally much better than 'IAS', etc.for those who do not understand these matters, like me, for example.cheers,nick

[nickpike 0]

BTW Tom,l3 10 % d 8 >= r 8 - 2 / * l3 100 % 10 / flr +works a treat. Note I added 100 % to stop the rolling numbers burrowing into the house foundations.cheers,nick

[Guest Ron Freimuth]

>Well, there you go, just the man to write a tutorial>regerding Aerodynamics calculations.:-) I've written gobs of emails along those lines. Saved a few.>Would you explain further,>> Dynamic pressure, q, is a useful parameter for setting>things that basically depend on it. Generally much better than>'IAS', etc.>>for those who do not understand these matters, like me, ..>nick 'q' is probably the most basic aerodynamic parameter. 'IAS' is only an Indicated value for 'airspeed', and the only place it occurs in the MSFS flight model code is how it is calculated from 'q' or TAS and how IAS is calibrated (now with two parameters in aircraft.cfg). q varies with TAS^2, actually q = 1/2 rho * TAS^2. rho = 0.002377 at ISA SL. q is measured in lb per sq ft in English units. I remember a C172 can land with q ~ 8 lb/ft^2, and cruises at q ~ 40 lb/ft^2. While q is more like 250 lb/ft^2 in a jet transport. I have this macro in my 'Test Base.xml':(A:ambient density,Slug/ft3) Showing how easy it is to get 'rho' for any atmospheric condition in XML. I need only multiply by 1/2 and TAS^2 to get q. Most aerodynamic parameters are scaled by q*Sw. Where Sw = Wing reference area. Thus: Lift(lbs) = q*Sw * CL For CL=1.0, Sw=200 ft^2, Lift= 1600 lb at q = 8.0 lb/ft^2 Drag(lbs) = q*Sw * CD For Sw = 200 ft^2, CD = 0.040, Drag = 8000*0.040 = 320 lb at q=40 lb/ft^2. q = 40 at about 110 kts. Suppose one wants to use the spoiler to generate a drag of 50 lbs at approximately 110 kts IAS. q is about 40, if Sw=200 ft^2, q*Sw would be 8000 lb. For the spoiler, Cd = Cd_ds * def(rad). So, to generate a drag of 50 lbs from the spoiler at IAS ~ 110 kts, we have: 50 lb = 8000 lb *Cd_ds * def. Say we deflect the virtual spoiler by 1/4 radian (we don't animate a spoiler on the AC when it doesn't have one). 50 lb = 8000 lb * Cd_ds * 0.25. So, Cd_ds*0.25 = 50/8000 = 0.00625, Cd_sp = 0.025. Which can be set in the AIR file. At the 'speed' q = 40, deflecting the spoiler by 0.25 radian would set the spoiler drag coefficient to 0.00625 and add a drag of exactly 50.000 lbs. More likely, one might like that 50 lbs drag to not change with speedq. In that case he could calculate the required deflection for the spoiler in XML code. Getting a constant 50 lbs drag regardless of 'speed'. Until speed got so low even a large virtual spoiler deflection wouldn't give that much drag. I skimmed over a 13 MB pdf NASA file on Performance of Light Twins last night. One curve showed how 'cooling drag' varied with AoA. 'q' was not a factor as far as the curve went. Rather, Cd_cooling was plotted as a function of AoA. I assume that drag is due to cowl flaps and how air flow changes through them as AoA changes. Anyway, Cd_cooling varied from maybe 0.0035 down to 0.0020 as AoA changed. Roughly 10% of airframe Cdo. Rather than using 'q' to set the 'cooling drag', one could change the virtual spoiler deflection with a calculation starting with (A:Incidence_alpha,radians) to approximate the curve in the NASA publication. Assuming a correct implementation, one wouldn't have to guess, since the data on cooling drag is available. He could use AFSD to check that the implementation worked correctly. Further, knowing how much Cd operation of cowl flaps adds, one could calculate just how much the top speed of the AC would drop when the flaps are fully open (and, AoA is maybe 2 degrees). Further, he could calculate the increase in fuel consumption required to maintain TAS = 160 kts with the cowl flaps open. With the price of fuel nowadays, that might encourage him to be more careful to not open the flaps more than necessary. Ron

[taguilo 33]

>I'd love to, but it's finding time at the moment. I'm working>on 3 panels at the moment for a certain development group. We>could do with a good tutorial regarding the use of macros,>modulus and an understanding of stack manipulation and how it>works, and the use of operators like 'd', 'r', etc. Do you>fancy putting pen to paper? Be nice to have a tutorial on>formatted text as well, but that's another story.>cheers,>nickI can't promise anything so far, though I'll try to sketch something.Tom