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Guest wtsapchy

Trimming Aircrafts

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Hi all,I just want to get some help from those who use keyboard to control pitch up / pitch down. How do know the aircraft is perfectly trimmed ? I mean, when you use joystick, after pulling back the stick on rotation, you hold the stick until the aircraft takes off. Then, you trim the plane until the joystick can be released from your hand without the plane further pitching up or down. At that point, you know the plane is trimmed. But when you use keyboard to control rotation, after you hit that pitch up key several times, the plane rotates and takes off. Afterwards, without a joystick in your hand to get that feeling, how do you 'visually' realize the plane is trimmed ?DanielVHHH

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Hi Daniel,Unless you're flying an aircraft that doesn't have an altimeter or VSI (Vertical Speed Indicator) you can simply watch the altimeter or VSI to see if you're climbing or decending.

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Or you could hold down Shift key and hit Z key, and observe the red altitude numbers at the top of your screen as you adjust trim. When red altitude numbers stabilize, you are trimmed. Hit Shift+Z repeatedly to cycle info on/off.

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Hi all,Thanks ! But that's exactly what I got confused. I mean, isn't that a plane can be perfectly trimmed even though it's climbing or descending. A plane can be trimmed to allow you to release that pressure on the flight joke while climbing at 1800 fts /min. So, a plane is still perfectly trimmed even though the plane is climbing or descending. What is the exact meaning of 'A plane is trimmed' ? Is it just as simple as a zero VSI ? I don't think so.I read the tutorial many times. A plane can be trimmed during any stages of flight, whether climbing, descending or at level flight so as to release that pressure on the yoke. So, if I don't have a flight yoke or joystick to get that feel, how do I know the plane is perfectly trimmed ?Daniel

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The purpose of Trimming is exactly as you say: to relieve control pressure forces. Lets say I'm flying an airplane in a climb at 150 knots. I will pitch to maintain 150 knots, and then I will use the trim switch/wheel to do the rest of the work for me. If I do it right, the airplane should climb at 150 knots and I should be able to almost fly hands off or, at least with fingertip control. You can be trimmed correctly in any mode of flight (climb cruise descent etc). You'll know it when you aren't having to constantly hold back or forward pressure on the control stick/yoke.

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Hi Alex,I perfectly agree with you. That's why I have been asking from the very beginning. If you only use keyboard to control pitch, how do you know the pressure on the stick be released after you hit that trim key several times because you don't have a stick to let you feel the pressure. That's why I ask if there are any ways you can 'visualize' that the plane is perfectly trimmed.DanielVHHH

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Hi Daniel, If you are climbing, and want to do so at say, 150 knots, to achieve this you may have to keep your VSI at say 800fpm, if the aircraft is acomplishing this at the rate of both of these figures without any change, I would say the plane is trimmed. If the speed and VSI starts to change you are not in trim. Your are technically using elevator trim to maintain proper speed, so if the speed is not consistant, this is not being accomplished. It is easier to feel with a yoke IMHO. I could never fly with keyboard. That in itself is an accomplishment that you should be proud of. I wouldn't be able to get off the ground, let alone maintain a procedure climb. I hope this helps.

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Hi Jeff,Thanks for your help ! IAS and VSI are stable. That's the time the plane is perfectly trimmed. That's the answer I am looking for. Thanks a lot again !DanielVHHH

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That just means that you trim stable for level cruise flight. You might wish to use trim for climb, descent, wind correction, uneven loading compensation or any number of things and since there is no physical control feedback you simply use the instruments (IAS or VSI or whatever) which you would do in real life along with the control feedback sensation. There is also rudder trim and aileron trim and other items to trim on the more sophisticated aicraft.Be careful when setting elevator trim on takeoff as it is additive to the trim you already have on the stick. You can very quickly find yourself in too steep of a climb and in a stall. You want to be gently easing off on the stick while adding trim and if you see or feel a large deviation in pitch either way use some stick to counter balance it out. Be aware of your speed in in other words. In time it just becomes second nature.Also trim sensitivity can be adjusted should you find it either too sensitive or not sensitive enough.

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Although It's not in every ones budget, I would invest in any type of joystick, IMHO any joystick is better than the keyboard for reasons such as this one.

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If you only use the keyboard to control pitch you don't *need* to trim.Trimming is about reducing constant loads on the yoke/joystick. You don't have a yoke/joystick, therefore there are no loads to trim off. Therefore you don't need to trim.Just set the aircraft in the desired state and don't push the pitch keys again. The aircraft may wander off as speed, weight, alt, balance, temp, wind etc changes, you could use the pitch trim to "fine tune" the pitch but basically you don't need it.As the others have mentioned though, go get yourself a joystick as quick as you can, doesn't matter how expensive, it will completely change the sim for you.Hope this helps,Ian

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Look at the trim position indicator. If position indicator shows a position above the takeoff position, the airplane is trimmed for fast airspeed. If the position indicator shows a position below the takeoff position, the aircraft is trimmed for slow airspeed.The trim control sets an aircraft's angle of attack, and because angle of attack and airspeed are inversely proportional when holding lift contstant, the trim control is used by a pilot to maintain a desired airspeed. The effect of relieving control pressure is merely a convenient by-product of manipulating the trim wheel.

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eh? You're kidding right?>Look at the trim position indicator. If position indicator>shows a position above the takeoff position, the airplane is>trimmed for fast airspeed. If the position indicator shows a>position below the takeoff position, the aircraft is trimmed>for slow airspeed.OK, that all makes sense but...>The trim control sets an aircraft's angle of attack, andReally??? I was fairly sure the trim control sets (for want of a better expression) the neutral position of the control surface.>because angle of attack and airspeed are inversely>proportional when holding lift contstant, OK, it's non linear so it's not quite as simple as that but you're about right.>the trim control is>used by a pilot to maintain a desired airspeed. No, the trim control is used by the pilot to remove continuous loads on the yoke/control column so he (or she) doesn't have to maintain a constant pressure on it to achieve the desired attitude. The desired attitude may well balance out with the power applied and a constant (and hopefully desired) airspeed will result but that's merely a convenient by-product.>The effect of>relieving control pressure is merely a convenient by-product>of manipulating the trim wheel.Sorry, relieving control pressure is the specifically designed intention of trimming. Given enough electronics, trimming is not required (see the FBW on the (real) airbus and most modern fighter aircraft).I think you need to read a bit more Principles of Flight.Hope this helps,Ian

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Fly By Wire. It means that the controls in the cockpit affect the control surfaces by means of elctrical signals instead of cable driven controls. The Airbus aircraft being the prime example.In the example given by Ian a few posts back, if you let go of the Airbus sidestick controllers, the aircraft will stay at whatever pitch the aircraft was at when you let go. The Airbus aircraft still have elevator trim, however it is not used manually during flight unless the FBW system is degraded in any way. That is a very, very, simplified explanation though - there are some good detailed explanations of the behaviour available at www.airbusdriver.net, look for a reference to "Control Laws".Chrs

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