Won't fly straight

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ballistx
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Won't fly straight

Post by ballistx »

I am new to the A2A 180 and am getting very confused (not hard). I am having 2 main areas of difficulty. One, the autopilot does not seem to work like a real autopilot should. I cannot turn it on to hold altitude unless I activate one of the other functions (St, HDG, TRK1, TRK2). That seems illogical, irrational and justification not to purchase an STEC autopilot in a real plane. Second, when you set up the autopilot and let it trim up the airplane it flies straight and holds altitude. However, when you turn it off the plane immediately dips and turns, which means that the autopilot did not REALLY trim up the plane but just put in temporary offsets to compensate. Again, not realistic or I am doing something wrong?

Second, and more serious, the plane WILL NOT fly a straight heading without about 15 degrees of left yoke or serious left rudder. When the autopilot is on the yoke has about 15 degrees of left bank in order to fly straight. Meaning the autopilot is adjusting the yoke instead of the trim. Major problem as this is NOT how a true autopilot has to work.

There is nothing I can do with the trim setting to get it to fly straight and not bank increasingly to the right. I have calibrated the CH Products yoke and pedals in Windows and they are perfect. I have gone into Flightgear and they are set up exactly as they should be, zero at neutral and full on at extremes. Yoke returns to 000 repeatedly.

The plane is useless if it cannot reasonably straight out of the box and cannot be trimmed with either ailerons or rudder. Anybody got any resolution other than scrapping it for parts?

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Oracle427
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Re: Won't fly straight

Post by Oracle427 »

That is not how an STEC 30 autopilot functions.

It does not trim up the plane for you, so you must manually move the trim to get the plane well trimmed before engaging the autopilot. It will also beep and warn you if it is working too hard against a poorly trimmed condition.

I am not aware of any real autopilot that holds altitude without a type of lateral mode engaged. Perfectly realistic. The STEC is a great autopilot IRL, I used to fly with one all the time and it is dead simple to use.

Check to see if you have rudder or aileron trim applied in FSX. You should map a trim re-center key to recenter those trims. Even though the real and A2A aircraft does not have these trims, FSX does not stop one from using them and it will affect the flight model.

Lastly, have you checked to ensure that the aircraft is in good working order in the preflight walkaround and hangar? It may be possible that a part is not in good order.
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ballistx
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Re: Won't fly straight

Post by ballistx »

Ok, I guess I am not viewing the simulator in the right mode. For a simulator I expect to be able to set up a mission to be midway between the localizer and the LZ. Then I can practice, repeatedly, the control of the aircraft without being distracted by the other aspects of flying. Not true conditions but that is what a simulator is for. Yes, I can do that, however, the darn plane runs out of fuel. I FINALLY ran the first tank dry and the engine stalled. Guess what, when you have 150 lbs of fuel on one tank and none in the other the plane wants to bank towards the full tank.

So, it appears that every time I want to repeatedly repeat specific maneuvers I have to preflight the plane? Certainly adds a significant amount of time to the process and slows down being able to use the simulator in that manner. I can understand and appreciate the exactness of replicating the plane in it's realistic environment and doing the preflights, etc. I can see where that will be an excellent training in getting back to realistic flying after being away for 25 years due to medical (heart stents, etc.). However, I would like to see an option to start anywhere (including mid flight) with a fully functional plane just to practice specific maneuvers, such as slow flight, VMC, etc.

So, problem of trim and banking resolved with fuel. (Red face).

Still do not understand how the STEC cannot handle altitude hold being turned on without some other function. Seems illogical. I don't really want to have to rely on the autopilot to bank the plane for me. I want it to hold altitude while I bank the plane manually so I can control the approach to the ILS. That I can deal with, as this is to get me up to my checkride (after 25 years) without having to spend 15-20 hours in a real plane at $200/hr. So, autopilot is nice to let me concentrate on other things but it is something that can be worked around.

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Oracle427
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Re: Won't fly straight

Post by Oracle427 »

Again, these are high fidelity simulations of the real things. You must use the real world manuals to guide you on how to operate the simulated units. The real world units will not engage a vertical mode without lateral mode engaged. It is not a matter of being a lesser autopilot, this is just how they work. What is the problem with turning the airplane using the heading bug as would be proper technique while the autopilot is engaged?

KAP140, STEC30, STEC55x, GFC700 all behave this way. I can't speak for the older units that I do not have experience with. Curious, what autopilot did you use that allowed one to engage a vertical mode without engaging a lateral mode? I'm not trying to suggest that one doesn't exist, I just haven't come across one in my limited experience (350 hours).

I wouyld also recommend a read through the product manual to understand what you need to do to operate the way you wish. You can do whatever you want to the fuel and load in the aircraft using the A2A menus.

The preflight also takes about 30 seconds if you really rush through it. This isn't a real prefliught where you need to actually walk around the aircraft and remove things. You can very quickly click and look at the screens. You can also turn off damage on each flight and bypass this wear and tear aspect of the simulation.

The A2A aircraft are not like other simple add-on aircraft, there is a lot more going on and you will get surprised this way if you take shortcuts and don't learn how to work with them.

One thing to keep in mind is that A2A went way beyond the capabilities of the base FSX engine and model many aspects of the simulation externally or with customized variables. The result of this is that starting the simulation from a saved state can create odd behaviors. FSX doesn't always resume saved states from advanced add-on aircraft the right way. Personally, I don't try to do this and always being the aircraft back to a landing short of my intended destination if I can't finish the flight right then and there. Some of the other forum members might be able to guide with ways to properly save and resume flights with advanced add-ons.
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ballistx
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Re: Won't fly straight

Post by ballistx »

Having been away for 25 years, all has changed. My current familiarity with the actual use of autopilot currently is with those in the FSX simulator where you can activate alt without anything else. Using the bug in a real plane would be simpler than trying to align the mouse with the knob, keep it there and then move the bug. Also, I was looking for actual, hands on the yoke control of the lateral to concentrate on the feel without having to divert my attention to the altitude. Not saying that is realistic.

As I recall, the 180 I flew in the '90's you could activate them independently. Don't see any reason that they couldn't be.

If I have 15 minutes to practice some approach I don't really want to have to park the plane, fuel it, etc. and then have to close down FSX in order to load the mission to be in the middle of an approach to practice a few landings. Maybe FSX will let me refuel it in mid-air. Haven't checked that. Yes, it can be worked around but wasn't what I expected. What I anticipated was that if I did my pre-flight, full fuel, etc. and then set up an ILS and saved that mission somewhere enroute, then when I load that mission again the plane is in the same condition it was at the time I saved the mission.

What would be convenient would be to be able to set up initial conditions and then save that with the mission in order to be able to repeat the mission from the same starting point, instead of the plane condition the same as left on whatever the last mission was.

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Re: Won't fly straight

Post by Oracle427 »

I'll leave it to others to comment on save/resume. You can absolutely re-fuel in the air, just try it. As far as I know, there is no way to bypass the aircraft fuel/oil state persisting across saved flights. That functionality is the heart of the Accusim product line.

Let's think about why you wouldn't want to have an airplane trying to hold altitude without at least a wing leveler. How would the airplane keep altitude if it was banked and had no way to correct the bank condition? It would likely apply more elevator.

As the bank angle increased, as it likely would, more elevator would be required to maintain altitude. All this time the load factor would be increasing and the aircraft would be shortly entering a spiral dive and tearing itself apart. It just happens that the STEC 30 doesn't support a wing level mode, it needs to follow a heading bug or CDI source. I'm not sure if you can map keys to control the heading bug, maybe someone else can comment on that as I use the mouse.

I use the Accusim aircraft for staying proficient at home. I find it to be extremely useful when I am away from the aircraft. I'm sure with a little adjustment period you'll get oriented and sorted out.
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AKar
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Re: Won't fly straight

Post by AKar »

Just a couple of additional points.
ballistx wrote:Having been away for 25 years, all has changed. My current familiarity with the actual use of autopilot currently is with those in the FSX simulator where you can activate alt without anything else.
Of curiosity, name me one that allows you to do this, without entering into basic lateral mode as well. There are very good reasons for why autopilots in general don't allow you to select most vertical modes without any lateral mode, and very little reasons why one wanted to; the closest common ones to such functionality are the control wheel steering modes some airplanes provide. There are autopilots from bigger plane world that allow individual disconnection of channels, but that has some downsides that ought to be rather obvious.
ballistx wrote:Ok, I guess I am not viewing the simulator in the right mode. For a simulator I expect to be able to set up a mission to be midway between the localizer and the LZ. Then I can practice, repeatedly, the control of the aircraft without being distracted by the other aspects of flying. Not true conditions but that is what a simulator is for. Yes, I can do that, however, the darn plane runs out of fuel. I FINALLY ran the first tank dry and the engine stalled. Guess what, when you have 150 lbs of fuel on one tank and none in the other the plane wants to bank towards the full tank.
The "thing" behind A2A GA airplanes appears to me to be more about bringing in a more comprehensive airplane simulation than simply a flight simulation. Some of their stuff work in real time, apparently, as per computer's clock, so there are compromises what comes to scenario setup and all that. I'd agree it would be cool if they published a module for their Accu-sim which would allow you to set up various training scenarios, and then to revert into persistent airplane, but without having one as of now, I prefer the current way of persistent airplane continuing from where you last left it, even if that forced me to fly complete flights for scenarios.

-Esa

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Re: Won't fly straight

Post by wrkempson »

I have a couple of saved flights that start mid air for landing. Yes, there are some things that I have to adjust, but it is not a problem. Simply pause the flight and put in the lost settings. For example, on my P-51 I have to turn fuel flow on and double check that the battery is on. I also do a quick check on flaps, landing gear, etc. When clicking on a switch or adjusting a lever, the graphic will not move in pause mode. It's just a matter of unpause then pause and you will see the switch move. Fuel can be adjusted while paused, etc. All this takes a minute or so, but is much quicker than starting on the ground.

Experience will tell you what settings may have been lost during the save. Again, just pause the flight and make the plane right again. Unpause and land. You can save the flight in paused mode to start with.

Hope this helps a little with your frustration. It works for me.

Wayne

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Re: Won't fly straight

Post by ballistx »

AKar wrote:Of curiosity, name me one that allows you to do this, without entering into basic lateral mode as well. There are very good reasons for why autopilots in general don't allow you to select most vertical modes without any lateral mode, and very little reasons why one wanted to; the closest common ones to such functionality are the control wheel steering modes some airplanes provide. There are autopilots from bigger plane world that allow individual disconnection of channels, but that has some downsides that ought to be rather obvious.
Not sure if you meant real life or FSX. Real life I haven't been in a small plane in 25 years and memory from back then is sketchy. Regarding FSX, the 172, Baron 58 and add on PA28-200 all let me bank and turn with only the ALT on.

There is a tremendous difference between the A2A 180 and any of the other FSX planes that I have flown. It will take getting used to and the more I advance the more the A2A benefits will come out. My objective is to get back to familiarity for the ground/flight check ride. That will be either in a 172 or a 180. So, when I have gotten up to speed on the 180 I will be purchasing the 172 trainer from A2A. They seem to be exactly what I need over the long haul.

When I get my check ride for VFR, then I will be going for my IFR and it will be of a big help in that aspect as well.

Thanks for all the input.

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Oracle427
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Re: Won't fly straight

Post by Oracle427 »

The stock FSX autopilot is junk and very unrealistic. It will teach you bad habits.

Oh and welcome back into the fold. Looks like a win for Basicmed? :)

I am saying many return to aviation now and that is wonderful to see.

Just wait until you discover the G1000 or similar glass avionics.

Good luck!

I'm resuming my IFR training in about 45 minutes after a several month hiatus. Hope I fly straight. :)
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AKar
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Re: Won't fly straight

Post by AKar »

Just add maybe some value to some fellow simmers around who's interested, a tiny mini-essay...



Why no vertical mode alone?

In simple terms, because the control "channels" as they are sometimes called in control system design are not isolated in their effects. In particular, as all pilots know, the rate of turn is squarely more affected by the pitch control, the elevator, as the bank angle increases, whereas the effect of the bank control, the aileron, diminishes as the bank angle increases.

While this has some implications why such a system that allows a separate pitch channel connection would have some inherent danger in it in any case, this has some particular consequences in our GA airplanes, which for the vast majority, utilize rate-based autopilots.

Put simply, such an autopilot does not know our attitude: bank angle, pitch attitude, all that, are unknown to it. Instead, it senses our rate of turn, pressure altitude and vertical acceleration to smoothly guide the airplane towards the target values. What comes to the roll control via ailerons, the autopilot directly uses the sensed rate of turn to command some aileron input through some heavy dampening. It also uses the static pressure to keep an altitude, and the vertical acceleration for an immediate feedback to avoid entering into phugoid oscillations around the set altitude by immediately correcting any felt change in vertical acceleration, but only via elevator channel, completely independent from the aileron.

Now, such a system design, with isolated channels, assumes by design that the bank angles remain small. This is to avoid the following inherent feedback loop that occurs if the bank angle was large:
  • 1) The autopilot notes a drop in altitude, due to increasing bank;
    2) the autopilot increases the nose-up elevator command to hold the target altitude;
    3) the tilted lift vector results in an immediate increase in airplane's rate of turn, as it affects into the turn;
    4) the autopilot immediately commands ailerons to decrease the bank to keep the rate of turn at the desired value;
    5) the introduced pitch rate is directed up via reducing bank angle, resulting in a gross altitude overshoot and a loss of stable flight.
In principle, by smooth aileron control, the altitude hold could adjust the elevator on its own with pilot controlling the aileron. The next issue would pop up with the system tuning. Assuming a level flight, the bank angle vs. lift required gets extremely sensitive after the transition into so-called steep turn region, where large elevator inputs have a large effect on the rate of turn without having a large effect on the vertical speed. A rate-based autopilot system without direct knowledge of the airplane's bank status would need to be tuned for two inherently different situations in pitch channel: one where any given command gives rather proportional change in g and in rate-of-climb, and also one where hardly any effect occurs on the rate-of-climb after a similar input, but a similar effect in the g is noted.

The dynamics of vertically constrained flight are importantly different at high angles of bank in comparison to near-straight-and-level flight. As an autopilot is primarily a cruise control device, the relatively simple electronics driving its brains are tuned that way. An autopilot that was able to hold the altitude at large angles of bank would get into fly-by-wire territory, being able to constantly estimate the airplane's flight condition and adjust accordingly. Without any feedback of the bank angle, angle-of-attack, airspeed or pitch attitude, it would get pretty difficult to tune the system just right, albeit it could be mentioned that even more complex situations are held in extremely narrow island of stability by modern control systems with similarly restricted inputs, but these require some assumed knowledge of the system's behavior, something that is not assumed to a great extent by a simple autopilot, outside its tuning criteria.

-Esa

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Re: Won't fly straight

Post by DHenriques_ »

ballistx wrote:
AKar wrote:Of curiosity, name me one that allows you to do this, without entering into basic lateral mode as well. There are very good reasons for why autopilots in general don't allow you to select most vertical modes without any lateral mode, and very little reasons why one wanted to; the closest common ones to such functionality are the control wheel steering modes some airplanes provide. There are autopilots from bigger plane world that allow individual disconnection of channels, but that has some downsides that ought to be rather obvious.
Not sure if you meant real life or FSX. Real life I haven't been in a small plane in 25 years and memory from back then is sketchy. Regarding FSX, the 172, Baron 58 and add on PA28-200 all let me bank and turn with only the ALT on.

There is a tremendous difference between the A2A 180 and any of the other FSX planes that I have flown. It will take getting used to and the more I advance the more the A2A benefits will come out. My objective is to get back to familiarity for the ground/flight check ride. That will be either in a 172 or a 180. So, when I have gotten up to speed on the 180 I will be purchasing the 172 trainer from A2A. They seem to be exactly what I need over the long haul.

When I get my check ride for VFR, then I will be going for my IFR and it will be of a big help in that aspect as well.

Thanks for all the input.
Perhaps the best thing about A2A (and the most difficult for us to deal with BTW) is the realism we build into our airplanes.
When you purchase an A2A aircraft you are entering a whole new world of desktop flight simulation. Actually, and I'm being very truthful here, you are entering a world of flight simulation entirely separate from the planes usually found in the base simulator. If you come into the A2A world bringing your experience and expectation with you based on your use of the base simulator planes or even other add on planes, your expectation will be to expect the same behavior from the A2A airplane (and it's systems) as was experienced prior to your A2A purchase.
I's estimate a HUGE amount of the "issues" we have to address here on the forums dealing with an A2A airplane's behavior are either local computer issues or issues being experienced by a user expecting behavior based on their past experience using the simulator.
Assuming no local computer or hardware issues, (they DO happen :-) what we usually end up doing here at A2A is stress the absolute importance of reading our supplied manuals, especially as that relates to aircraft systems and how they function.
Literally everything involved with an A2A aircraft from the flight model down through the aircraft's systems has been designed to function as closely to the actual function as current technology allows. The aircraft even interacts with it's environment correctly. Basically speaking what this means is that if the real plane would feel something as it moves through the air, there is a very good chance your A2A airplane will be feeling it as well. If there is the slightest imbalance in trim the airplane will be feeling that. If the atmosphere and the engine are at odds with each other at any moment, the airplane will be feeling that as well.
What I'm getting at here is that once you decide and have reach the point where you can accept all this and realize that you have to approach an A2A aircraft basically in the same way you would have to approach the actual plane, you are well on your way to realizing that when it comes to A2A, not only reading the manual but understanding the manual is not only advisable but literally mandatory when you purchase one of our planes.
Don't get me wrong here. I'm not saying the planes we design and produce are perfect. What I am saying however is that everything put into our planes has been either put there or checked by real pilots having vast experience. With all that having been said, we also learn every day how to make something even better then it was at release. When that happens we change something to reflect that improvement.
So take heart and don't give up. If you notice something you think might be wrong somewhere, do as you are doing and let us know. There's always somebody here on the forums that can help. We want you as an A2A customer to have the best possible simulator experience. And we won't give up until that happens.
Toward that end, I see you have been having issues with the auto pilot in the Cherokee. I suggest you make a cup of coffee and read our manual section on the auto pilot. The AP installed in the Cherokee is an old type that has been tried and proven over time and understanding EXACTLY how it works will make your flying experience a lot better.
Dudley Henriques

ballistx
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Re: Won't fly straight

Post by ballistx »

My only interest in FSX is to use it in the interim to get my VFR, and possibly my IFR pre-training to shorten my actual flight time requirement. I still need to confirm that I can restore my medical. At 75 and heart stents, fat and out of shape??? Oh well, maybe this will get me the incentive I need.

Things work out this summer (after 8 years) I can get my Piper 6XT and do some real flying

The A2A planes look like they will fill the bill for just what I need for now and perhaps the Piper 250 will be close enough to the Xt.

Thanks to Dhenriques for the insight into the programming complexities of the ALT and bank angle relationships. I have done some fairly sophisticated computer programming and can appreciate what it takes to get just that little bit of the plane correct.

Thanks All

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Re: Won't fly straight

Post by mallcott »

ballistx wrote:My only interest in FSX is to use it in the interim to get my VFR, and possibly my IFR pre-training to shorten my actual flight time requirement. I still need to confirm that I can restore my medical. At 75 and heart stents, fat and out of shape??? Oh well, maybe this will get me the incentive I need.

Things work out this summer (after 8 years) I can get my Piper 6XT and do some real flying

The A2A planes look like they will fill the bill for just what I need for now and perhaps the Piper 250 will be close enough to the Xt.

Thanks to Dhenriques for the insight into the programming complexities of the ALT and bank angle relationships. I have done some fairly sophisticated computer programming and can appreciate what it takes to get just that little bit of the plane correct.

Thanks All
Then clearly you need a sim and a product that DOESN'T deliver poor quality recreations of the real thing. Score one for your choice of an A2A aircraft !

As for the refuelling issue - It's a non-issue IF you have your sim set up correctly.

Fuel is added NOT with the FSX fuel menu but with the A2A-specific menu. You can save the flight after setting up all the parameters for a quick restart of that saved flight and be back to wherever you want, with whatever fuel you want, with the 180 set up as you want, in seconds. It's then repeatable ad infinitum.

As with the real aircraft you are going to have spend some time with the manual for the sim, as there is nothing that you've mentioned that can't be achieved with a little knowledge of the product you have bought and the sim you run it on.

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Re: Won't fly straight

Post by Gabe777 »

I think most aircraft will automatically disconnect the autopilot if you pull on the yoke or trim.

In fact fsuipc has a setting that disconnects the trim (artificially) when the ap is engaged, precisely to prevent you doing it accidently, which is quite easy using using flightsim controllers.

As for autopilot vertical and lateral modes....all I know is, in simple terms, that if you bank, the nose drops and so you have to pull back to maintain pitch....and increase throttle to maintain altitude....so an autopilot would never be able to maintain altitude if it didn't also have control over roll and trims.

In fact you are still required to adjust throttle or you may be asking too much of a plane with rudimentary ap functions, and may stall. This is why airliners have auto throttle on from start to finish often, as they have complex fm systems and certainly don't want the pilot sticking his oar in !

Anyway, at least these real sims make you think about what's happening and why. Get a refresher on basic principles or even the fsx lessons.... throttle for altitude, pitch for speed etc etc.

If you just want to play around, which is always good sometimes, look elsewhere.
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