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Thread: Cessna trim

  1. #1

    Default Cessna trim

    Hi

    I'm having difficulty with the FSX lessons when it comes to trim. I know what to do and can fly the plane only using trim with no problem. But if you follow the lessons the guy says 'don't use trim first, use the yoke to get the right pitch and then trim to maintain that level'. So I try to do that, I pitch the plane how I want it then turn the trim.. however, even when I get the plane flying how I want it (which takes a long time of constantly trimming up and down) the nose suddenly starts moving up or down again. I'm constantly having to change the trim, even when I'm maintaining the same speed. But when you see the teacher do it he just moves the pitch to where he wants and then turns the trim and the nose of the plane doesn't move.. how does he do it? It goes exactly to where he wants it without having to fiddle with the trim and when he does get it right first time it stays there... mine still keeps moving up and down. What am I doing wrong.

    Steve

  2. #2
    Join Date
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    Location
    Memphis, TN.
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    Default

    You are doing NOTHING wrong... he just has 6000 hours more time in the aircraft than you...
    It does take at least a couple hours of practice to begin to get the feel of any particular aircraft.

    Loyd
    Hooked since FS4... now flying: FSX Acceleration on Win7/64, Core Duo E8400; GA-EP45-DS3R; GTX 460-768MB; 4G RAM; Freezer 7 Pro

  3. #3

    Default

    Quote Originally Posted by llivaudais View Post
    You are doing NOTHING wrong... he just has 6000 hours more time in the aircraft than you...
    It does take at least a couple hours of practice to begin to get the feel of any particular aircraft.

    Loyd
    It makes it more difficult with the cessna because there are no numbers on the trim whereas some planes you can see the actual -/+ trim numbers.

  4. #4

    Default

    Quote Originally Posted by flightplanes View Post
    ... What am I doing wrong.

    Steve
    Trying to compete against a computer program.

    There is no instructor actually flying the plane, the plane is following a pre-described path in the sky.

    In most cases you cannot get the trim exact in the sim without fine tuning it with the throttle.

    Also note that you can get a plane to trim and it can speed up a bit, throwing it out of trim and making it climb.

    Trimming is not a "set it and forget it" deal. As you burn fuel the plane gets lighter and will start to climb. If the wind changes you will have to re-trim.

    If you are using a button on a joystick for trim go into the settings and make sure the repeat slider is at least in the middle, if not full left.

    Lastly, practice, practice, practice, ...and then practice some more, you'll get it.

    peace,
    the Bean
    WWOD---What Would Opa Do?
    Farewell, my freind (sp)

  5. #5
    Join Date
    Feb 2010
    Location
    Denver, CO USA KAPA, KLMO, 35CO
    Posts
    1,479

    Default

    Think of trim when you're driving a car; the minute corrections you make with your hands on the steering wheel are very similar to keeping an airplane in trim. In the sim, you're always going to be using a combination of trim, throttle and yoke to keep the airplane going in the direction you want it to go, all at the same time.

    Keep at it; you're doing just fine. PRACTICE, PRACTICE, PRACTICE!


    "I created the Little Black Book to keep myself from getting killed..." -- Captain Elrey Borge Jeppesen
    P4 3.0 SINGLE CORE 2GB CORSAIR RAM ATI RADEON 4650 1GB GPU SAMSUNG 160 GB HDD WIN XP SP3 FS8 FS9 CFS CFS2 IL2

  6. #6

    Default

    Correct - you are doing nothing wrong - you likely do need more time to get the feel of trimming the aircraft.

    BUT ... After comparing my own RW experience and that of several other RW general aviation pilots we have agreed that the trim settings are too sensitive for many of the FSX aircraft (particular culprits are the Cessna 172 and the stock DC-3). I have modified most every aircraft.cfg file for the planes I fly to fix this. Basically the fix changes the amount of trim per each click of the trim button (or key, depending on how you are doing it). [I apologize in advance if you are an expert at this already but I know it took me a while to figure some of this stuff out and things go smoother if the directions are as clear as they can be.]

    Some folks are reluctant to change the aircraft.cfg file but if you save your original one you should be OK. My method is to
    - First make a copy of the aircraft.cfg file in the folder where it is (in the specific airplane's folder in SimObjects)
    - Re-name the copy aircraft_cfg.bak and leave this along with the original file in the folder it applies to
    - Proceed to make any modifications to aircraft.cfg knowing that if something goes wrong you can delete that file and rename
    aircraft_cfg.bak as aircraft.cfg

    (Some in my group prefer to copy the file and move it to a different folder but if you do this you will need to rename it something like:
    aircraft_cfg.C172 - using the example of this being the Cessna 172's file - because every aircraft.cfg file has the same name).

    Open up aircraft.cfg (use Notepad) - find the section [flight tuning] - you will see (without the elevator trim line in bold):

    [flight_tuning]
    cruise_lift_scalar = 1.0
    parasite_drag_scalar = 1.0
    induced_drag_scalar = 1.0
    elevator_effectiveness = 1.0
    aileron_effectiveness = 1.0
    rudder_effectiveness = 1.0
    pitch_stability = 1.0
    roll_stability = 1.0
    yaw_stability = 1.0
    elevator_trim_effectiveness = 1.0
    aileron_trim_effectiveness = 1.0
    rudder_trim_effectiveness = 1.0

    Change elevator_trim_effectiveness = 1.0 to some number less than 1.0. For the Cessna 172 I use 0.5 - here is what my settings look like in the C172 aircraft.cfg file:

    [flight_tuning]
    cruise_lift_scalar = 1.0
    parasite_drag_scalar = 1.0
    induced_drag_scalar = 1.0
    elevator_effectiveness = 1.0
    aileron_effectiveness = 1.0
    rudder_effectiveness = 1.0
    pitch_stability = 1.0
    roll_stability = 1.0
    yaw_stability = 1.0
    elevator_trim_effectiveness = 0.5 //1.0
    aileron_trim_effectiveness = 0.5 //1.0
    rudder_trim_effectiveness = 0.5 //1.0

    Note also that after the three parameters I changed (I change them all even if the aircraft doesn't have that particular capability whenever I make any aircraft.cfg changes) I added after each " //1.0 " - with the // preceding the information this makes this a remark line (you probably did know that) that the program does not read and is my 'extra safety net' just in case I need to revert back to the original settings.

    Experiment with the values - frankly I find little difference between the 0.5, 0.6, 0.7 range of values but individual preferences do vary!
    Last edited by FlyingHorseSindbad; 03-19-2013 at 04:15 PM.
    Dan
    www.vfrprophops.com / www.ifrjethops.com
    Win 8, i7 3770 3.9 GHz, 12 GB DDR3 RAM, NVIDIA GT630 2 GB mem 42" 1080p FSX w/Accell yoke joystick rudder pedals REX TrackIR-5 FlighSim Commander FSUIPC

  7. #7

    Default

    Quote Originally Posted by FlyingHorseSindbad View Post
    Correct - you are doing nothing wrong - you likely do need more time to get the feel of trimming the aircraft.

    BUT ... After comparing my own RW experience and that of several other RW general aviation pilots we have agreed that the trim settings are too sensitive for many of the FSX aircraft (particular culprits are the Cessna 172 and the stock DC-3). I have modified most every aircraft.cfg file for the planes I fly to fix this. Basically the fix changes the amount of trim per each click of the trim button (or key, depending on how you are doing it). [I apologize in advance if you are an expert at this already but I know it took me a while to figure some of this stuff out and things go smoother if the directions are as clear as they can be.]

    Some folks are reluctant to change the aircraft.cfg file but if you save your original one you should be OK. My method is to
    - First make a copy of the aircraft.cfg file in the folder where it is (in the specific airplane's folder in SimObjects)
    - Re-name the copy aircraft_cfg.bak and leave this along with the original file in the folder it applies to
    - Proceed to make any modifications to aircraft.cfg knowing that if something goes wrong you can delete that file and rename
    aircraft_cfg.bak as aircraft.cfg

    (Some in my group prefer to copy the file and move it to a different folder but if you do this you will need to rename it something like:
    aircraft_cfg.C172 - using the example of this being the Cessna 172's file - because every aircraft.cfg file has the same name).

    Open up aircraft.cfg (use Notepad) - find the section [flight tuning] - you will see (without the elevator trim line in bold):

    [flight_tuning]
    cruise_lift_scalar = 1.0
    parasite_drag_scalar = 1.0
    induced_drag_scalar = 1.0
    elevator_effectiveness = 1.0
    aileron_effectiveness = 1.0
    rudder_effectiveness = 1.0
    pitch_stability = 1.0
    roll_stability = 1.0
    yaw_stability = 1.0
    elevator_trim_effectiveness = 1.0
    aileron_trim_effectiveness = 1.0
    rudder_trim_effectiveness = 1.0

    Change elevator_trim_effectiveness = 1.0 to some number less than 1.0. For the Cessna 172 I use 0.5 - here is what my settings look like in the C172 aircraft.cfg file:

    [flight_tuning]
    cruise_lift_scalar = 1.0
    parasite_drag_scalar = 1.0
    induced_drag_scalar = 1.0
    elevator_effectiveness = 1.0
    aileron_effectiveness = 1.0
    rudder_effectiveness = 1.0
    pitch_stability = 1.0
    roll_stability = 1.0
    yaw_stability = 1.0
    elevator_trim_effectiveness = 0.5 //1.0
    aileron_trim_effectiveness = 0.5 //1.0
    rudder_trim_effectiveness = 0.5 //1.0

    Note also that after the three parameters I changed (I change them all even if the aircraft doesn't have that particular capability whenever I make any aircraft.cfg changes) I added after each " //1.0 " - with the // preceding the information this makes this a remark line (you probably did know that) that the program does not read and is my 'extra safety net' just in case I need to revert back to the original settings.

    Experiment with the values - frankly I find little difference between the 0.5, 0.6, 0.7 range of values but individual preferences do vary!
    Thanks Dan I'll try that. I've been putting the full folders for the various planes that I modify in my documents folder under a new fsx planes folder so that I can simply copy and paste the old plane back in no matter what changes I make to the one in the fsx folder.


    Steve

  8. #8

    Default

    Quote Originally Posted by StringBean View Post
    Trying to compete against a computer program.

    There is no instructor actually flying the plane, the plane is following a pre-described path in the sky.

    In most cases you cannot get the trim exact in the sim without fine tuning it with the throttle.

    Also note that you can get a plane to trim and it can speed up a bit, throwing it out of trim and making it climb.

    Trimming is not a "set it and forget it" deal. As you burn fuel the plane gets lighter and will start to climb. If the wind changes you will have to re-trim.

    If you are using a button on a joystick for trim go into the settings and make sure the repeat slider is at least in the middle, if not full left.

    Lastly, practice, practice, practice, ...and then practice some more, you'll get it.

    peace,
    the Bean
    I use the mouse for my trim in the virtual cockpit.. does that make a difference?

    Steve

  9. Default

    I agree with all previously stated. In the RW, I constantly trim in all axes. In a trainer like a C172 you only have pitch trim so you end up holding pressure on rudder and aileron until you balance the fuel to rectify roll trim. But this is CONSTANT if you focus on feeling what the airplane is telling you. Some aircraft require more trim, some less. A P51 for example, unbelievable amount of trimming and footwork on the rudder pedals to fly coordinated and to fly straight and level. It's easy once you learn how to multitask in the cockpit. You will find that the more stability built into a design, the more trimming required once you leave that trimmed condition. The stability built in is trying to take the airplane back to the condition it was trimmed for. It is difficult to reproduce the RW feel especially in small control inputs in the sim. When you build in curves to your input of control, this removes you farther from how real aircraft feel due to the lack of the same system in the RW aircraft for most anyway. It can give less positive feel and the controls get soft when a light input should yield a crisper result of control feel. In summary, keep trimming! We do in the RW as well!

  10. #10

    Default

    I'm using RealTrim by Nils Meier
    http://code.google.com/p/fscode/wiki/RealTrim
    and find its one-stroke trimming allows for very smooth, fast and precise trimming of the plane.

    In addition I've set the response curve for the elevator with FSUIPC to very low sensitivity close to the null position, which allows to adjust very subtle attitude changes, and then trim these out with RealTrim in an instant.

    I couldn't go back to stumbling around with the buttons.
    Attached Images Attached Images  

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