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Thread: What is a Stab Trim ?

  1. #1

    Default What is a Stab Trim ?

    What is it and how does it work ?.

    Thanks

  2. #2

    Default RE: What is a Stab Trim ?

    http://www.flightsim.com/dcforum/Use...ed4475a10b.jpg

    Stab (Meaning stabilator) is alot like elevator trim, depending on the type of aircraft that you are flying - it is a vertical control surface - hope this helps.:-wave

  3. #3

    Default RE: What is a Stab Trim ?

    >What is it and how does it work ?.
    >
    >Thanks

    For my simple answer it is a moveable surface either on the elevators or the rudder which is for adjusting the effect to either the horizontal stabilizer or the vertical stabilizer.
    In the case of the horizontal stabilizer, the vertical tendancy or trim of the craft is dependant on airspeed and center of gravity weight loading. The faster an aircraft goes, usually the tendancy is to pitch up. This trim tab will balance out the trim for a given cruising speed.

    On earlier aircraft such as the German WWII bf109 fighter, all that they had was a piece of metal on the elevator that was bent up or down before the pilot took off. He had no control of this after airborne. On more advanced aircraft, the trim tabs might be controllable from inside of the cabin. It makes it easier to fly wwith the controls and with the tabs properly trimmed, the aircraft may be able to fly straight and level for miles. On some aircraft such as the Blue Angels F-18s the pilots intentionally fly with strong down trim so that they have some pressure (actually pull) on the joystick so that they can physically keep the aircraft accuratly tracking. Otherwise they would end up correcting and over correcting their pitch up and down. That would cause very inaccurate flying and the aircraft would actually hit more often than they do in close formation. The trim tabs on their aircraft are so deflected that it takes a constant ~18 lbs of pull on the joystick to maintain level flight. There may also be trim tabs on the rudder to correct for the aircraft's tendancy to twist (roll) or yaw to the side. These are generally controllable in the MS flightsim with the numberpad commands on your keyboard or with the mouse on most aircraft that have the function added to the panel.
    Bilbo

  4. #4

    Default RE: What is a Stab Trim ?

    Hi. You guys are describing Elevator trim, which is very different than stab (stabilizer) trim.

    Elevator trim is a little tab that moves in the opposite direction as the elevator, as found on a Cessna 172. Stabilizer trim is found on much larger planes, and is basically the rotation of the whole horizontal stabilizer. To se how this works, take the meljet 777, or 747, or any new POSKY model and give it full up trim, then look outside at the horizontal stabilizer. Then put it all the way down and observe the difference. :)

  5. #5

    Default RE: What is a Stab Trim ?

    >Hi. You guys are describing Elevator trim, which is very
    >different than stab (stabilizer) trim.
    >
    >Elevator trim is a little tab that moves in the opposite
    >direction as the elevator, as found on a Cessna 172.
    >Stabilizer trim is found on much larger planes, and is
    >basically the rotation of the whole horizontal stabilizer.
    >To se how this works, take the meljet 777, or 747, or any
    >new POSKY model and give it full up trim, then look outside
    >at the horizontal stabilizer. Then put it all the way down
    >and observe the difference. :)


    In my post I was not just describing elevator trim but also rudder trim. However, the method that you describe was also used on the Ford Tri-motor back in 1929 and is not particularly related to the size of the aircraft. But the real question is, is there a difference in functionality and control implementation?- particularily in relation to the FS2004 simulator.


  6. #6
    Join Date
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    Default RE: What is a Stab Trim ?

    And also on the J-3 Cub, among others...


    Larry N.

  7. #7

    Default RE: What is a Stab Trim ?

    Good explanation. Stabalizer/Elevator trim, the key here is pitch axis, which you covered.

    KJ

  8. #8

    Default RE: What is a Stab Trim ?

    Excellent explanations!!

    Michael

  9. #9

    Default RE: What is a Stab Trim ?

    Didn't know the J-3 has stab trim, interesting. I just didn't want to lead to the idea that all aircraft have it, and in general it is more commonly found in larger aircraft. I thought the original poster understood regular trim tabs, but didn't know what stab trim was. My mistake, sorry. :)

  10. #10
    Join Date
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    Location
    Wolverhampton, West Midlands, England
    Posts
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    Default RE: What is a Stab Trim ?

    Yep and the PA28. :-lol A stabilator is an elevator that moves the whole tail section, and is a hybrid of horizontal stabiliser and elevator.

    Any aircraft that has a stabilator obviously has stabilator trim, called the tab in the picture below.

    http://www.toandfrom.org/lightaircra...stabilator.jpg
    PPL(A)
    PPL(H)
    IMC

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