TylerTheHottie Posted November 16, 2015 Posted November 16, 2015 So part of the start up procedure I understand is to at some point set your takeoff trim. Can someone just explain what it does? it doesnt seem to do anything whether I take off with it set or not.....
electro_monkey Posted November 16, 2015 Posted November 16, 2015 As far as I know It's purpose is just to reset trim to zero position. i5-9600K / RTX 2060 / 32 GB DDR4-3200 CL16 / Win10 x64 / Cobra M5 (BRD)+ Gametrix ECS / Opentrack
Luzifer Posted November 16, 2015 Posted November 16, 2015 Since you don't have visual indication of trim in the A-10C, the takeoff trim button will move the trim to takeoff settings automatically if you hold it until the light comes on. You may not have noticed a difference on the first flight since the plane is loaded with trim in the takeoff position already. If you land, refuel/repair/rearm and take off for another flight, that button will take care of your trimming. Taking off with a plane trimmed for landing is a quite unpleasant experience. I, uh, heard that somewhere. 1
TylerTheHottie Posted November 16, 2015 Author Posted November 16, 2015 Since you don't have visual indication of trim in the A-10C, the takeoff trim button will move the trim to takeoff settings automatically if you hold it until the light comes on. You may not have noticed a difference on the first flight since the plane is loaded with trim in the takeoff position already. If you land, refuel/repair/rearm and take off for another flight, that button will take care of your trimming. Taking off with a plane trimmed for landing is a quite unpleasant experience. I, uh, heard that somewhere. are you saying that it like sets the flaps and stuff to takeoff? and engages nosewheel steering and everything? is that what you mean?
0xDEADBEEF Posted November 16, 2015 Posted November 16, 2015 no, it is setting the trim. this is a separate system of your aircraft and has nothing to do with flaps or nosewheel steering. I'll try to explain the trim system in a simple way. You will use the trim system in flight to have your aircraft fly straight with your stick centered. If you do not trim you will have to keep your stick a little bit forward if you fly fast, and a little bit aft if you fly slow. so if you fly fast you will have to trim forward to have you stick centered, if you fly slow you will have to trim it back. This is a very basic flying system that every aircraft has.
Delarius Posted November 16, 2015 Posted November 16, 2015 Excellent description, however I'd like to point out one small thing - which may not be quite so evident if you don't have a force feedback stick. In the A-10C when you adjust the trim the stick moves to the trimmed position. This is different than on most aircraft. The reason is that the A-10C trims with its control surfaces, whereas planes like Cessna's trim using trim tabs, not their main control surfaces. I'm also not absolutely sure if pressing "T.O. Trim" has the exact same functionality as pressing "Trim reset". In theory it should be somewhat different but it might just be a glorified 'trim reset', at least as implemented by DCS A-10C.
0xDEADBEEF Posted November 17, 2015 Posted November 17, 2015 Excellent description, however I'd like to point out one small thing - which may not be quite so evident if you don't have a force feedback stick. In the A-10C when you adjust the trim the stick moves to the trimmed position. This is different than on most aircraft. The reason is that the A-10C trims with its control surfaces, whereas planes like Cessna's trim using trim tabs, not their main control surfaces. That is not quite 100% accurate. I did not describe this in the first answer on purpose, because the first step is understanding what trim is and I wanted to keep the thread on topic. Since you took it further, I'm trying to clarify. Having trim-tabs or not does not affect if the stick moves or not. The Stick in the A10C moves because you don't have a force feedback stick, not because there are no trim-tabs. Lets get some facts straight about how real aircrafts work - there is no real "center position" like on our non-FFB-sticks in a real aircraft - just accept this for now please. - If you fly fast your stick will be forward, if you fly slow your stick will be aft while holding altitude. - This is because the horizontal stabilizer will generate more lift at high speeds, and less at slow speeds. if you do not trim the aircraft, you will almost always have a force on your stick you have to counter in order to keep altitude (unless you fly at a certain speed in a certain altitude with a certain center of gravity at a certain temperature). Since this would be very uncomfortable to fly, aircrafts have a trim system. This systems job is to remove the forces from the stick. The simplest form to do so is trim-tabs, which are found on the control surfaces (a control surface on the control surface if you like). If you wish to trim up you move the trim tab down, which will generate a counter-force that removes the force from your stick. The stick itself will NOT move, but you will not need to apply a force to hold it in position. The same principle applies with every other trim system, no matter if it is trim-tabs, stabilizers or fly-by-wire systems. They all remove the force from the stick, they do not move the stick itself. So here comes the tricky part of not having a force feedback joystick in a simulator. Since we cannot adjust the center position on spring-centered joysticks, we have to overcome this with moving the stick. So if you would want to trim a fast flying aircraft forward, you have to move the stick backward while pressing the forward-trim button. Ideally while doing this the stick in the virtual cockpit would not move (if done in a clean fashion). Like already explained above, if you have a force feedback stick you dont have to move the stick at all while trimming, but you will feel the force become less, until its gone. If you then keep trimming the force would be applied on the opposite direction.
Luzifer Posted November 17, 2015 Posted November 17, 2015 That is also not quite 100% accurate, since we are nitpicking here. :) As an aside there are actual spring centered (in the pitch direction) sticks in airplanes where the trim mechanism moves the center point of the spring. I think most modern sailplanes fall under that category. The more pertinent point is that if the trim acts on the elevator, then it just moves where the zero force point is. That means if you apply zero force on the stick (by letting it go), trimming will move the stick. That just follows as the inverse of trimming changing force on a stick held in a fixed position. However, if that happens on the ground or not simply depends on whether the trim system is aerodynamic (no aerodynamic forces parked on ground, so no) or hydraulic/electric/spring center force based (then yes). I'm not sure right now how the feeling is on trim systems where it acts on the stabilizer instead of the elevator (most airliners), i.e. whether stabilizer movement acts back on the yoke or whether the yoke is exclusively elevator movement and thus sees no trim. Fly-by-wire systems are different again in that they usually don't have force feedback and a fixed center position — just like our sticks without force feedback. Since they process the input anyway, trim may happen automatically.
0xDEADBEEF Posted November 17, 2015 Posted November 17, 2015 See, this is why I tried to keep it simple in the first place ;)
Delarius Posted November 17, 2015 Posted November 17, 2015 FFB sticks Since you took it further, I'm trying to clarify. Having trim-tabs or not does not affect if the stick moves or not. The Stick in the A10C moves because you don't have a force feedback stick, not because there are no trim-tabs. Not sure I fully understand. As I do have a force feedback stick, it's quite evident in that the stick does physically move when trimming. Can't imagine going back to non Forcefeedback - particularly for Huey, but if you watch the stick in game, or observe the stick IRL they both move when trimming even with your hands off the stick.
TylerTheHottie Posted November 17, 2015 Author Posted November 17, 2015 That is not quite 100% accurate. I did not describe this in the first answer on purpose, because the first step is understanding what trim is and I wanted to keep the thread on topic. Since you took it further, I'm trying to clarify. Having trim-tabs or not does not affect if the stick moves or not. The Stick in the A10C moves because you don't have a force feedback stick, not because there are no trim-tabs. Lets get some facts straight about how real aircrafts work - there is no real "center position" like on our non-FFB-sticks in a real aircraft - just accept this for now please. - If you fly fast your stick will be forward, if you fly slow your stick will be aft while holding altitude. - This is because the horizontal stabilizer will generate more lift at high speeds, and less at slow speeds. if you do not trim the aircraft, you will almost always have a force on your stick you have to counter in order to keep altitude (unless you fly at a certain speed in a certain altitude with a certain center of gravity at a certain temperature). Since this would be very uncomfortable to fly, aircrafts have a trim system. This systems job is to remove the forces from the stick. The simplest form to do so is trim-tabs, which are found on the control surfaces (a control surface on the control surface if you like). If you wish to trim up you move the trim tab down, which will generate a counter-force that removes the force from your stick. The stick itself will NOT move, but you will not need to apply a force to hold it in position. The same principle applies with every other trim system, no matter if it is trim-tabs, stabilizers or fly-by-wire systems. They all remove the force from the stick, they do not move the stick itself. So here comes the tricky part of not having a force feedback joystick in a simulator. Since we cannot adjust the center position on spring-centered joysticks, we have to overcome this with moving the stick. So if you would want to trim a fast flying aircraft forward, you have to move the stick backward while pressing the forward-trim button. Ideally while doing this the stick in the virtual cockpit would not move (if done in a clean fashion). Like already explained above, if you have a force feedback stick you dont have to move the stick at all while trimming, but you will feel the force become less, until its gone. If you then keep trimming the force would be applied on the opposite direction. My mind is....blown.
Corbett1403 Posted November 17, 2015 Posted November 17, 2015 (edited) take off trim noobie question Takeoff Trim Control Button. Labeled T/O TRIM, pressing this button will automatically set all trim tabs to neutral, takeoff settings. When all trim tabs have been set to the proper setting, the takeoff trim light above the button will light and indicate TAKEOFF TRIM." This was taken from the A10c manual which you could grab and read as it helps with understanding how the aircraft functions plus you can go back and check anytime you can view the manual for free online. Sent from my iPhone using Tapatalk Edited November 17, 2015 by Corbett1403 1
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