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n4gix

Autopilot keeps climbing

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Hi gangFor some time now the autopilot has been misbehaving and I just can't figure out what's going on. The problem is the climbing and altitude feature (VNAV in the more advanced models). Very often I set an altitude and the plane starts climbing ok but as it reaches that altitude it just keeps climbing. I suspect it might have something to do with trimming and how the joystick works. I have tied the elevator trim to an axis on my Saitek X52 and apparently, whenever I touch it it still affects the elevator, regardless of the autopilot being in control.Can someone verify trimming is not exclusively left to the autopilot when it's engaged? Is the joystick's different axis sending continous signals to the sim, even when I don't touch it? Does anyone know what's going on?CheersEDIT: Corrected my terrible spelling :(./Jonas

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Vnav suggests a jet with a modern autopilot. In Vnav, (pitch) trim is Exclusively an Auto Pilot function. Jets don't have elevator trim tabs and use the Horizontal Stabilizer for pitch trim. This pitch trim can be manually controlled, however with Vnav engaged touching any manual pitch trim control will Immediately disconnect the AP. Who knows what happens in a FSX default model, but that's how a real airplane works. Watch your flight mode annunciators for AP status. Is the AP engaged? Is just Lnav flying the airplane, with Vnav disengaged? What's the Auto Throttle doing? Captain? Inquiring passengers want to know . . . for their lives sake!

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>Watch your flight mode annunciators for AP status. Is the AP>engaged? Is just Lnav flying the airplane, with Vnav>disengaged? What's the Auto Throttle doing? Captain? >>Inquiring passengers want to know . . . for their lives sake!LOL! Well, the autopilot doesn't disengage when I touch the trim wheel on my Saitek, at least not in any model I'm flying. This includes some of the stock ones (172, Caravan etc.), the Super 80, a few twin turbos and, occasionally, the PMDG 747. I have the same problem in all of these but there might be some 3rd party planes that does model the AP auto-disconnect as you describe, I don't know.I guess I'll simply try to clear the Saitek joystick axis being bound to the e-trim and see if the problem goes away.Cheers/Jonas

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/Jonas:why are you trimming the aircraft when the autopilot is controlling? --

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>why are you trimming the aircraft when the autopilot is>controlling? I'm not, at least not deliberately. I have tried it out now and confirmed that tying a joystick axis to a trim surface is not a very good idea. Once I started to suspect the axis-bound elevator trim, reproducing the problem was very easy. I tried to take off, having cleared the joustick axis/e-trim assignment and set the AP to climb to 2500' before I engaged the AP. All worked fine and the AP levelled off at the assigned altitude as expected. I then punched 5000' in to the AP which immediately started to climb but then I went ahead and reassigned the joystick axis as an elevator trim controller. This time the AP was unable fight off the trim commands being sent and busted the assigned altitude. Just to make sure, I then cleared the axis assignment again and the AP immediately started to descend to the altitude programmed into it.So, the simple conclusion is: Don't tie any trims to any joystick axis, at least not if you have a Saitek X52 like I have because it keeps trimming regardless of the AP being engaged or not, the sim doesn's seem to be able to ignore joystick axises. Tying joystick buttons works fine but axis doesn't.Can't decide whether this should be considered a sim defect or not but there you have it. Guess I should've figured this out before I came here but, hopefully, some other flyer will be less confused if he/she is encountered with an AP that just won't stop climbing (or descending for that matter).Cheers/Jonas

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But Jonas...Why would/did you assign elevator trim to a joystick?Rob O.

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Hi,I have a Hotas Cougar control system and have always had elevator trim assigned to a wheel, (antenna elevation actually) on the throttle stick, both with FS9 and FSX and have never had a problem with autopilot and trim. It is possbile to use the trim while the autopilot is controlling altitude and rate but the auropilot just re-adjusts and keeps on doing its thing. I have never had a problem with altitude overun. It might be peculiar to the Saitek or it might be due to the setup or a particular aircraft. I have had no problems with any aircraft in my stable.

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>Why would/did you assign elevator trim to a joystick?Well, why wouldn't I? Back when I was flying small GA's in real life the trim wheel was a fairly large device, usually sitting between the seats somewhere. 'Wheel' is the keyword here and I feel that tying the trim to something as similar as possibly would make trimming easier and, actually, it does (as long as you don't engage the AP of course). Fiddling with the keyboard is both unrealistic and actually pretty frustrating as there's no cues as to how much trim is actually being applied at the moment. Of course, that info can sometimes be read somewhere in the VC but having a physical wheel for that type of input is always a better idea IMHO.Do you mean to tell me I'm the only one ever having come up with the idea of tying other inputs than just the elevator, rudder and pitch to the joystick? :( Cheers/Jonas

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John,I know I can re-program the Saitek X52 to have it emulate keystrokes when I turn the wheels (on the thrust lever) and I guess that probably will solve the problem as (I suspect) it will no longer send continous input when I don't. I'll try that later.Is your Cougar re-programmed like that or is it real axises you're talking about? You migth be right and it's a Saitek issue but it would surprise me as the type of signals should be the same AFAIK.Cheers/Jonas

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>Well, why wouldn't I?Because the Joystick commands a continuous input with increasing rate the greater the deflection, unless in the null position. This is *not* how one uses trim IRL. In essence, you are trying to fly the airplane with trim alone? Unless making small trim changes, seems this would result in the proverbial phugoid flight path. The *only* (off-hand) reason I can think of doing this would be if an Elevator Cable snapped or was bound-up somehow.Maybe I misunderstand what you are doing... are you using one joystick for the Main Flight Controls and a second for the Trim?John's example of using the Antenna Elevation Wheel on the Thrustmaster Cougar HOTAS is an excellent idea (although the wheel's movement is a little loosey-goosey, I bet it works very well).>Fiddling with the keyboard is both unrealistic and actually pretty frustrating as there's no cues...Sure there are cues... just like IRL... If you have to maintain any amount of Stick Pressure, then you need trim... it's as simple as that.And I really don't get the "unrealistic part". Unless you're in a full mock-up cockpit of the plane you're flying, one can always claim "unrealistic". Whether you have to hold a key on the keyboard, hold the up/down key on an Xbox D-Pad etc... Your brain still has to key off the fact that you are maintaining a certain control stick pressure, and you have to do "something" to remove that pressure.>Do you mean to tell me I'm the only one ever having come up with the idea of tying other inputs...Probably not... However, I must say (in my limited time as a CFI) that I never had a student that insisted on using the trim inputs to fly the plane... It was always the other way around. ;-)Rob O.

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Jonas, I have never had a Saitek so bear with me. My wheel on the Cougar is not programmed to send keystrokes it is another analogue axis available in the FSX Controls/Control Axes section labelled "Elevator Trim Axis" I just have it assigned to the Cougar's "Antenna" Wheel. Sending keystrokes from an analogue axis is frought with problems. If your Saitek wheel is also a proportional axis you should have no problem assigning it to the "Elevator Trim Axis". I also have the FSX Mixture axis assigned to my Cougar Range wheel.I hope this gives you some ideas.

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Rob O I beg your pardon, my Cougar Wheel is not loosey goosey and works as well as the trim lever did on my RW aircraft although I had no autopilot on those. Actually the aforesaid wheel is right under my left thumb and is second nature to use even on short finals. BTW I once flew one of my own RW aircraft for two hours on trim and rudder alone, never touching the stick. It was just one of those delightful days that happen every now and again;-)

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>John's example of using the Antenna Elevation Wheel on the>Thrustmaster Cougar HOTAS is an excellent idea (although the>wheel's movement is a little loosey-goosey, I bet it works>very well).And that's exactly what I was doing too, using the antenna wheel on the Saitek X52 thrust handle (it's a HOTAS). If you imagined me with a second joystick, then I fully understand why you thought it weird. Anyway, that wheel represents a joystick axis and, as you say, it works very well; until I engage the AP that is. As the antenna wheel (the axis) kept feeding the sim with input, even when the AP was engaged, I kept missing my altitudes. >And I really don't get the "unrealistic part". Well, maybe the "unrealistic" aspect wasn't really my main concern then. I just *prefer* using a wheel because it's much easier and I can make smaller adjustments. Like John said, it becomes "seconds nature" once you get used to it.John, I'm still curious about whether your Cougar antenna wheel functions as a joystick axis or as keyboard input.Cheers/Jonas

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Jonas,My wheel is functionally the same as any other analogue proportional axis like the stick axes (ailerons and elevator) and the throttle axis. However, I can program it to send keystrokes as well as movement or instead of movement. In my FSX installation files it is a pure analogue proportional axis (just like the throttle) but bound to the "Elevator trim axis" through the FSX controls/axes section. I don't even have any keystrokes defined for up and down trim anymore having removed them (KP1 & KP7 from memory) early in the FS9 piece. I tried using keystrokes on a wheel once and it was a hopeless cause. So in summary my Wheel is acting the same way as a joystick axis not a keyboard input device. There is an obvious trap with keystrokes on a wheel you need a neutral point that ensures that the keystroke sending is stopped and you will need some software to check that this is not happening. As I don't own a Saitek and cannot help you further in that endevour.I believe that there are plenty of Flightsim enthusiasts using a wheel for trim but they may not frequent this forum often as they are too busy enjoying the FSX experience. You will of course need an analogue axis that is not self centering like the joystick but stays where it is put like the throttle.Jonas, your aspiration is both valid and doable if your equipment will allow. When you succeed you will find yourself in a far better "Real as it gets world".

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John...When I said "loosey-goosey" I meant the rheostat or potentiometer or whatever is *maybe* a little too easy to move to serve in place of a trim wheel and would take a little getting used to (certainly seems that way on mine and I have no clue how to "tighten" it up). Is good to hear that works so well for u. I have been too shy up to this point to try my Cougar using the just released Vista 64 RC drivers on my x64 XP system. I'm certainly more interested in trying the Cougar now so thanks for the info.>BTW I once flew one of my own RW aircraft for two hours on trim and rudder alone...Yes, sure enroute that's the way to do it... should be "hands off" for the most part. I did say,

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