Is there an easier way :)
Results 1 to 10 of 10

Thread: Is there an easier way :)

  1. #1

    Is there an easier way :)

    Hi
    Im trying to adjust the DEFLECTION v DYNAMIC PRESSURE but the maths leaves me wallowing and wanting
    As the table is liner there has to be a simple maths to work out the IN/X param as a speed at sea level ? why they didnt just use speed as the
    X param is beyond me given how simple the table is
    Thanks
    Wozza
    The source code for Vista may very well be the longest suicide note in history

  2. #2
    Here's the math:

    V_fps = SQRT(2*q/rho)

    q = (rho/2) * V_fps^2

    V_mph = V_fps * 3600/5280

    Alt (ft) rho
    00000 0.002378
    05000 0.002049
    10000 0.001756
    15000 0.001496
    20000 0.001267
    25000 0.001065
    30000 0.000889
    35000 0.000736
    40000 0.000582
    45000 0.000459
    50000 0.000361
    55000 0.00026
    60000 0.00019

    A good approximation for rho:

    rho = 0.002378 * (1.0 - 0.00000688 * altitude)^4.256


    This is pretty easy to code into a spreadsheet.

  3. #3
    Quote Originally Posted by sparks View Post
    Here's the math:

    V_fps = SQRT(2*q/rho)

    q = (rho/2) * V_fps^2

    V_mph = V_fps * 3600/5280

    Alt (ft) rho
    00000 0.002378
    05000 0.002049
    10000 0.001756
    15000 0.001496
    20000 0.001267
    25000 0.001065
    30000 0.000889
    35000 0.000736
    40000 0.000582
    45000 0.000459
    50000 0.000361
    55000 0.00026
    60000 0.00019

    A good approximation for rho:

    rho = 0.002378 * (1.0 - 0.00000688 * altitude)^4.256


    This is pretty easy to code into a spreadsheet.
    WOOOOOOSH!! thats the sound of what you typed passing way over my head
    spreadsheet I thought you used those to stop paint from getting on the floor
    Thanks for taking the time to reply but Im at a total utter loss when it comes to these formulas...I can understand the physics/theory behind it but not the maths (yeah Im lazy but have killed of way to many brain cells)
    maybe i didnt explain it well enough,My way of thinking in sim not real world is that at say 500ft at a certain speed the Y param will take effect rather than spend mths working out the maths there has to be a simple rule of the thumb to convert the X var to a "knots mph kmh" times,divided added or minus numberX = dynamic pressure
    Thanks
    Wozza
    The source code for Vista may very well be the longest suicide note in history

  4. #4
    Hi
    Was sitting here thinking and thought why not do some in sim testing
    what I did was set the elevator X1=0 Y1=1, X2=50 Y2=1 X3=51 Y3=0
    then bump up to 2000ft and dived with engine off and waited till elevator stopped working not the most mathematical solution but an interesting way to while away the hrs.
    ball park figures so far
    X of 25 = 95mph
    X of 50 = 145mph
    X of 100 = 195mph
    X of 150 =245mph
    X of 200 = 295 mph
    whilst not perfect there is a trend forming,Ive only tested with one aircraft so It will be interesting to see if its the same trend for different aircraft\airfiles
    if not at least I have sufficient info to fudge my project
    Wozza
    The source code for Vista may very well be the longest suicide note in history

  5. #5
    Over Iraq yesterday someone was talking to bagdad from FL570... pretty low Rho up there!!!!

    Sometimes physically plotting the "curves" will cause the light bulb to illuminate if perusal of the formulas and tables do not initially.

    Cheers: t

  6. #6

  7. #7
    Quote Originally Posted by sparks View Post
    mph to dynamic pressure at sea-level...
    Ahhh now thats easier
    now if i can work out something along these lines for the prop table
    Id be able to fix those as well yeah I know a whole different kettle of fish
    thanks agsin
    Wozza
    The source code for Vista may very well be the longest suicide note in history

  8. #8
    Herr Carter;

    In Jerry's old workbook series the generated tables were visible in graphical form. Another application is Aircraft Airfile Manager which also generates the tables in graphical form and are directly editable by airthemetic entries to the ordinates.

    Cheers from Dubai.... T

  9. #9
    Quote Originally Posted by fliger747 View Post
    Herr Carter;

    In Jerry's old workbook series the generated tables were visible in graphical form. Another application is Aircraft Airfile Manager which also generates the tables in graphical form and are directly editable by airthemetic entries to the ordinates.

    Cheers from Dubai.... T
    Ich bin dummkopf
    Using the graph above Ive now set the controls to freeze just over tha max permissible speed this stops the stupid crash reset if you push the aircraft slightly outside the envelope. Ive set the max speed to 300 mph in the cfg but if you manage to get to that speed your going to a big smoking hole in the ground

    I use AAM but the graphs make no sense to me as for the workbook I dont have excel so no luck there ...then I remembered that someone smarter than me did a 1% airfile for my cfs2 texan using the workbook.So I found that and had a look at the prop tables. A quick cut and paste and it looks like Im getting pretty close to real world fuel burn/speed at a quoted rpm/mp settings,though there are some weird prop pitch numbering in there it appears to work ok
    Now to fix the tail coming up late on take off and the roll issues and I think I can put this sucker to bed
    Thanks
    Wozza
    PS when using airwrench to set the balance up I almost always end up with an aircraft that feels(to me) to nose heavy is this right ? or have I missed something ?
    The source code for Vista may very well be the longest suicide note in history

  10. #10
    Hi Tom or anybody for that matter
    You ever sat in a G model texan? (yeah slightly off topic )
    I only have info on the C model and cant work out where they stuck the
    engine primer and the starter on the G model.Imagine my surprise when I found out they completely changed the cockpit layout in different models
    Thanks
    Wozza
    The source code for Vista may very well be the longest suicide note in history

Similar Threads

  1. OT. Real life easier than FSX
    By dandog in forum FSX General Discussion
    Replies: 43
    Last Post: January 7th, 2012, 11:16
  2. Search and Rescue just got a little easier
    By O-1Driver in forum CFS3 General Discussion
    Replies: 6
    Last Post: January 8th, 2011, 09:19
  3. Making things easier for myself, yard work-wise.....
    By Navy Chief in forum Ickie's NewsHawks
    Replies: 15
    Last Post: July 26th, 2010, 11:07

Members who have read this thread: 0

Bookmarks

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •