Deputy Sheriffs mopperle 4162 Posted April 26, 2011 Deputy Sheriffs Share Posted April 26, 2011 When I did my first flight with the Katana I realized that the stick needed a lot of pressure to prevent the aircraft going like a rocket into the sky Then I saw a discrepancy between the trim indicator and what I can see outside, what looks more like "Nose Up" then "Neutral" as shown on the indicator Indicator: Outside view: Is this a bug or did I miss something? Link to comment Share on other sites More sharing options...
Mr.Düssel 44 Posted April 26, 2011 Share Posted April 26, 2011 Hi oder hallo! Did you use the trim tab during your preflight preparations? You have to adjust them manually by "hand" .... Link to comment Share on other sites More sharing options...
Deputy Sheriffs mopperle 4162 Posted April 26, 2011 Author Deputy Sheriffs Share Posted April 26, 2011 Hi oder hallo! Did you use the trim tab during your preflight preparations? You have to adjust them manually by "hand" .... Hallo, yes, but I see tabs only for the rudder and the ailerons. Link to comment Share on other sites More sharing options...
Snave 466 Posted April 26, 2011 Share Posted April 26, 2011 You appear to be confused between the trim indicator and the function of trim. Trim is a FORCE multiplier/demultiplier, and the position of the indicator is NOT the same as the position of the trim tab. Link to comment Share on other sites More sharing options...
Deputy Sheriffs mopperle 4162 Posted April 26, 2011 Author Deputy Sheriffs Share Posted April 26, 2011 OK, so in this case the indicator only refers to the load the actuator apllies on the elevator controls? But how to bring the elevator trim tab into a "neutral" position? Link to comment Share on other sites More sharing options...
Snave 466 Posted April 26, 2011 Share Posted April 26, 2011 You adjust the trim using the button on the centre console - or the equivalent FSX keyboard or joystick setting. At no point should that be taken to mean that the trim tab itself should be level. Its neutral setting may be up or down, it's the effect that is `neutral`. Trim varies with load, configuration and speed and power and is felt as a force on the stick. Not with FSX though. The reason that neutral trim is required in the checklist is purely to provide a baseline setting for later adjustment or else stick forces could be very high in a dangerous phase of flight. Link to comment Share on other sites More sharing options...
tup61 185 Posted April 26, 2011 Share Posted April 26, 2011 At no point should that be taken to mean that the trim tab itself should be level. Its neutral setting may be up or down, it's the effect that is `neutral`. Trim varies with load, configuration and speed and power and is felt as a force on the stick. Not with FSX though. The reason that neutral trim is required in the checklist is purely to provide a baseline setting for later adjustment or else stick forces could be very high in a dangerous phase of flight. Very interesting. Never knew that. I like that kind of information! Keep it coming! The manual may explain how things work, but it doesn't tell you why (which btw is normal and no complaint about the nice manual...!) I like those real life pilot tips and tricks: it's always good to know why things work the way they do. Specially when things go wrong in mid air. Link to comment Share on other sites More sharing options...
Ron Attwood 33 Posted April 26, 2011 Share Posted April 26, 2011 Very interesting. Never knew that. I like that kind of information! Keep it coming! The manual may explain how things work, but it doesn't tell you why (which btw is normal and no complaint about the nice manual...!) I like those real life pilot tips and tricks: it's always good to know why things work the way they do. Specially when things go wrong in mid air. Wot he said. I actually feel as though I'm learning to fly rather than how to make a sim work.....If you know what I mean. Link to comment Share on other sites More sharing options...
Snave 466 Posted April 26, 2011 Share Posted April 26, 2011 Very interesting. Never knew that. I like that kind of information! Keep it coming! The manual may explain how things work, but it doesn't tell you why (which btw is normal and no complaint about the nice manual...!) I like those real life pilot tips and tricks: it's always good to know why things work the way they do. Specially when things go wrong in mid air. It's all to do with rigging. The Katana uses pushrods for aileron and elevator (cables for rudder) and the trim tab is controlled by the switch on the central console which operates an electrical actuator beside the vertical push rod in the vertical stabilizer. The actuator applies - via compression springs - a load on the elevator controls to increase (or more often relieve) the pressure felt on the stick. That's trim as the Real World knows it. (FSX `sees` trim as a secondary control surface which offsets or exaggerates the movement of the controller. All wrong, but that's a story for another day.) The rigging part is that it is normally optimal to have a trim tab show minimum deflection at cruise - produces less drag and makes for a more efficient airplane. To achieve this it is possible to adjust the elevator using the push rods so that for a given set of parameters, the aircraft will be `in trim` with least deflection at one speed, one throttle setting, one weight and one CG. But given the comparative light weight of the Katana, even small changes can have a disproportionate effect so if you want to actually experiment to see how `our` aircraft is setup then you'll need to do a series of tests changing the possible weights and moving the CG around - so that will be pilot, passenger, baggage fairings and fuel, (I don't think the other fluids have a `weight` in the sim, but I wouldn't put it past Marcel...) So in rigging you'd normally set the Katana up on the ground so that `neutral` trim means modest control surface forces that can be overcome relatively easily by even the most limp-wristed flyer. But that may mean offsetting the rigging of the elevator with some quite high trim tab adjustment value. It just is what it takes to get the job done. But there's no direct relationship between a neutral trim gauge setting and a neutral trim tab setting. Get it? At some point in the experiment, you will probably find a combination that has the trim tab virtually flush with the elevator, and with the aircraft neither climbing nor descending. It seems to be at a low power setting, single pilot, little baggage and less-than-full-fuel but actually it doesn't matter - only in the sim can you actually see the trim tab when in the air anyway! And it doesn't matter so much in a 100-knot airplane - drag increases as the square of the speed, so your 150-knot go-anywhere tincan drinking 15 gallons an hour needs to have a lot more attention devoted to rigging than our plastic tadpole with a 5-gal/hr consumption as the differences are non-linear! Hope this helps! Link to comment Share on other sites More sharing options...
tup61 185 Posted April 26, 2011 Share Posted April 26, 2011 Wot he said. I actually feel as though I'm learning to fly rather than how to make a sim work.....If you know what I mean. I know what you mean! I have the exact same feeling! Get it? Hope this helps! Got it! And it sure helps! I'm all ears. Link to comment Share on other sites More sharing options...
alehead 126 Posted April 29, 2011 Share Posted April 29, 2011 As I understand it, the trim tab works in an opposite sense to the control surface it is used to trim out. Pull back the stick and the elevator goes up, the nose goes up. Push the stickforward, the elevator goes down, the nose goes down. Operate the trim tab to trim nose down, the trim tab appears to point upwards, operate the trim tab to trim nose up, the tab moves down... That is certainly how I have always understood it... From Wikipedia, which cited The Anatomy Of The Aeroplane Darrol Stinton, ISBN 0-632-01876-3: "When a trim tab is employed, it is moved into the slipstream opposite to the control surface's desired deflection. For example, in order to trim an elevator to hold the nose down, the elevator's trim tab will actually rise up into the slipstream. The increased pressure on top of the trim tab surface caused by raising it will then deflect the entire elevator slab down slightly, causing the tail to rise and the aircraft's nose to move down." The appearance of the trim tab and the display is as it should be... Andrew Link to comment Share on other sites More sharing options...
Snave 466 Posted April 29, 2011 Share Posted April 29, 2011 Not always true, but a truism. The simplistic notion also reinforces the idea that the trim surface is a control surface. It isn't, it's a force multiplier or reduction tool. You trim for the force on the stick or yoke, not to slightly move the actual control surface, although in some cases that is what is done: Think of it this way: If I tie an elastic band round the Katana stick, and sit on the other end, as I push the stick forward I feel an increase in the amount of force required to hold the stick in that position. While some of that force IS dependant on the position of the elevator (it's deflecting into the slipstream after all to create a nose-down moment in response to the stick `request` to push the nose down) the force felt on the stick that can be trimmed out may well still be well within the capabilites of the trim system to trim out so the stick stays where it is put - even though some of that force is coming from a source other than the elevator deflection itself. All it needs is some extra movement of the trim tab. This is known as a SERVO tab, and moves in the opposite direction to the control surface. However, it is my understanding (and I am relying on memory here as I'm only interested in how to fly it, not build it) that the Katana actually uses an ANTI-servo trim tab whereby the tab deploys IN THE SAME DIRECTION as the control surface to create additional axis stability about that moment of rotation. But like I say it doesn't matter except to `outside flyers` who like looking at elevators in flight - and has no bearing on the realism of the trim system in FSX, which is fundamentally bogus anyway! Link to comment Share on other sites More sharing options...
Snave 466 Posted April 29, 2011 Share Posted April 29, 2011 OK I just double-checked and the DA20-A1 Katana DOES use an ANTI-SERVO tab that moves in the same direction as the elevator 1. GENERAL The DA 20 KATANA is equipped with an electric elevator trim system which allows the trimming of the airplane for different center of gravity positions. The elevator is adjusted using a rocker switch, located on the center console. A signal is transmitted to an electric motor which adjusts the position of the elevator assembly. The tab located on the rear of the elevator acts as an anti-servo tab and increases the elevator control forces. Note the use of `increase`. Conversely, and this is typical of how these things can be missed - the C1 Continental powered version uses a SERVO tab. Link to comment Share on other sites More sharing options...
alehead 126 Posted April 29, 2011 Share Posted April 29, 2011 Cool info, thanks Simon... Andrew Link to comment Share on other sites More sharing options...
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