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| IL-2 Sturmovik The famous combat flight simulator. |
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#1
06-26-2013, 05:21 PM
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From 2002 discussions on trim with Oleg I got some answers.
Question was why holding the stick steady off center doesn't get the same speed/acceleration as stick centered by trim. After all, trim will move a hands-off stick or column. Answer worked out to that we think the stick is held steady but it is not. This is mainly due to hardware, short gaming sticks and small involuntary muscle tremors. This is partly borne out by the reported results from those who made and use full size sticks to play IL-2. And since 2002 the impact of needing to be trimmed has been less. For my part, and you can easily check this yourself, there are two things that help. 1) use a light touch on your joystick. Try flying holding the stick with just 2 fingers and thumb just for while. When you catch yourself resting your arm weight on the stick or elbow on the table, get your arm up so it's not weighing the stick down. If you find yourself clenching the stick, loosen up. Besides the weight and ham-handing those are great ways to transmit tiny muscle tremors to the stick. 2) go into stick sensitivity and add FILTER to the pitch/elevator axis. Try about 50% at first. Maybe you need more or less but you should see results in minutes of testing. FILTER will flatten out the small and fast shakes even at less than 50% while yes, slowing your jerk-speed by a fraction of a second that you can see by watching the red and green blocks in the stick test area of the same stick sensitivity screen. It's not perfect but you should gain something if you're not already light-handed and using FILTER. 
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#2
06-26-2013, 09:07 PM
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This is all very interesting, but it is still obvious that the elevators on all of these aircraft are far too sensitive and that trim displacement is disproportionately ineffective compared to other aircraft modeled on the basis of old data and reputation. “Easily trimmed” means easily trimmed no matter how you want to parse it. If an aircraft has “sensitive tabs” I would expect it to mean that the elevator and rudder require fairly minor displacement to wash out higher stick or pedal forces over a wide range of speeds. When one aircraft type is clearly identified by everyone who flew it as excessively demanding of trim and other aircraft types are specifically identified as needing very little or no trim adjustment by the same group of people I tend to think that I should need to adjust the one type fairly regularly and the others considerably less.
Let’s try to put ourselves in the 1930s-era high performance aircraft designer’s shoes. Aircraft are starting to exceed level speeds of 300mph (480kph), and if you didn’t place and design the control surfaces just right, control forces became greater than the average pilot could exert. The vast majority of trim tabs were on the rudders of monoplanes, usually big ones like the Martin B-10 until the mid-30s, at which point the technical issues appear to have been largely overcome and they start showing up on the rudders and elevators of an expanding variety of aircraft (and the ailerons of aircraft that had wing tanks). The best pilots of the era tended to be drawn from the physical elites not least because you still had to exert fine control at a high force and because the buyers of high-performance military aircraft tended to be skeptical of depending upon new-fangled trim adjustment to keep the aircraft controllable. With good reason; changing trim was often clumsy and slow, unable to keep up with the higher speeds and acceleration of the modern monoplane fighters, so the designer/manufacturer was still expected to minimize the need (as opposed to the option) for trim for small speed variations. Trim was all mechanical, based on cables, pulleys, rods and screws motivated by human muscle and it was much slower than the digitally sensed and controlled systems we take for granted today, which were originally developed for high speed jets and found their way into civilian aviation, once they became cheap enough. Simply put, trim adjustment in the late 1930s and early 1940s was considered a necessary evil to be avoided where possible and emphatically NOT a desirable convenience that obviates the need to exert even more (expensive) fineness in design and execution of the aircraft’s wings and control surfaces. It added weight and complexity to the aircraft, as well as cost. So a wide range of speed change without requiring an adjustment in elevator or rudder was naturally going to be a primary design consideration. I would maintain that the Mustang was the most sophisticated high performance aircraft design around at the time of its introduction, and that the sophistication of its design would therefore be relatively sensitive to very minor changes. How sensitive to change is the Mustang’s wing to minor changes? The wing was filler finished and hand polished. The upper and lower wings were covered with a surface to assure smoothness of the airfoil sections. The metal covered ailerons are statically, dynamically and aerodynamically balanced, and the wing’s efficiency is well known to be adversely affected by nicks, dents and scratches on the surface. Look at any shot of a Mustang in flight taken from above, and check out the wings—you will see nothing like the panel lines and obvious distinct panels of the fuselage on those wings (I think of all the Mustang models I built over the years and the care with which I ‘detailed’ those wing panels for the sake of ‘authenticity’…), even on aircraft that were in constant combat operations. I can picture the engineering officer responsible for maintaining those aircraft ordering 55 gallon drums of putty and reams of sandpaper to the bemusement of his buddies whose squadrons flew P-47s. How adversely? It was found during factory tests that with a strip of wire 1/16 of an inch (roughly 1.6mm) taped along the leading edge of the wing, the aircraft would not leave the ground. America’s Hundred Thousand and every pilot I've ever read or talked to on the subject reports that the Mustang needed very little trim adjustment throughout its performance range and that tabs had to be applied with care; if the wings were that sensitive to minor changes, I would expect the elevators and rudder to be in very nearly the same class, that is, that very small adjustments would have great effect, and that they would not be necessary until a great deal of change in speed or power had taken place. Is that consistent with what we see in the Il-2 Sturmovik ’46 Mustangs? Are the other aircraft I've mentioned treated in proportion? cheers horseback
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#3
06-27-2013, 05:35 AM
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#4
06-27-2013, 06:52 AM
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If you can't overcontrol at high speeds or in turbulent conditions then you'll get sweet F-A control at low speeds.
Terms to look up are Maneuver Speed and V-Speeds. Going from flight sims in the past, maneuver speed being the fastest you can pull full stick deflection on ONE AXIS is about 240-250 mph for the P-51. By 360 mph it's -probably- not safe to pull half way, I leave it to someone else to guess why. Note that in WWII fighters the pilot can't take what the plane can. They had feel and were less prone to trying things that gamers who have no feel take for granted. Also that IL-2 is a simulation. When some G-limit (like 12 G's) is reached even momentarily it is bye-bye wings. Pilot blackout though seems to have a time element. BTW, I just came across FreeChecklists.net. Here is the P-51 page: http://freechecklists.net/Resources/.../P-51+Mustang/ And from the 1944 manual on page 19 under Maneuvers Prohibited: "It is impossible to do a good snap roll with the airplane and most attempts usually end up in a power spin."
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#5
06-28-2013, 07:54 PM
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It is just silly to require the Player to click the elevator trim three or four times for every speed variation of less than 20kph indicated (plus a couple of clicks of rudder trim to compensate for nose angle immediately afterwards) for aircraft that history (and multiple current examples) shows (1) didn't require it and (2) will be constantly varying in speed and angle of attack with no accurate on screen display to indicate vector/trim state. That this group is composed almost entirely of aircraft that exist in large numbers that fly to this day leads me to wonder if their FMs are a bit too detailed for the game engine or that there might be some kind of common mathematical error somewhere, possibly as a result of the conversion from Imperial measurements to metric. Most of the aircraft instrument panel displays are hard to read at best (always in Wide View, and often in 'Normal' view) and far too many of them are grossly inaccurate; artificial horizons that are indistinct or offset to an exaggerated degree, climb indicators that are slow and frankly, lie much of the time (when you have an indicator that measures feet of climb in feet per minute, and one deflection division mark is supposed to represent 100 feet, you shouldn't be able to change heights by 60 or more feet in less than 3 seconds with the needle just above the '0' mark, and I experienced this routinely in a great many of the aircraft I've tested so far, the notable exceptions being the Soviet and the IJA fighters). Two changes seem obvious to me; first, the addition of a temporary trim state display similar to the ones we get when we adjust throttle, prop pitch, supercharger or radiator settings. I'd like to see something along the lines of x% up Elevator Trim, x% Right Rudder Trim, and x% Right Aileron Trim with full trim deflection being 100%. Second, make the cockpit instrument displays consistently accurate to exactly the same standard for every aircraft; currently, there seems to be a great deal of variation in instrument accuracy and readability from inside the cockpit. I understand that unless there is one common conversion error that is easily detected, major changes in FMs is way more work than can be fairly asked of TD, in the near or far term, but the community shouldn't pretend that the inaccuracies aren't there. cheers horseback
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#6
06-26-2013, 09:30 PM
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So for the last six or seven years, my stick, pedals and throttle have been in exactly the same spot, which cut down on a lot of problems that plague other simmers, especially the ones who use sticks that feature heavy springs and no way to anchor the darn things. I haven't played with filtering very much, though; that's a worthwhile suggestion. Thanks. The addition of a smaller pot in series with the larger one is also a good idea; one of my nephews managed to break the case of my CH Yoke several years back so I took it apart and used the electronics as a base for a trim and button box; trouble is, the pots will only use about (the most linear) 60 degrees of rotation, so just breathing on them can be excessive when I try to use them for trim in Il-2 (not so much with FSX or the DCS Mustang, but you still have to be careful). cheers horseback
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#7
06-27-2013, 01:54 AM
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60 degrees turn? You can get better ones.
What matters is how many ohms range you get from stop to stop and how many ohms your hardware uses. Ohms is resistance. I would start with the pot you currently use and put a meter across one of the outside legs of the pot to the center leg to find out what you got. The standard plug into the gameport stick runs from 0 to 100k ohms. 1/100th of a turn covers 1k ohms. If I put that in series with a 10k pot then that pot will be 1/10th as sensitive as the 100k. The digitizer measures how much voltage gets through with 0 ohms meaning full and increasing ohms going towards none, 110k total as opposed to 100k is not a big deal and should only affect calibration. That's why I tell that you can have one pot/slider for coarse adjustment and the other for fine adjustment. If you want 20x fine then for a 100k coarse you would add a 5k fine that would change the total resistance 1/20th as much for the same turn as the coarse knob. Maybe the better setup would be a coarse long slider and turn pot for fine adjustment. What your stick uses for values, you will have to find out for yourself. If you're up for it there are hobby controller electronics in the $60 and under range like the BUO-series at leobodnar.com (has 12-bit A/D) and less-accurate (10-bit) but far cheaper DIY MCU's like the Teensy's and Leonardo's (that can use external ADC chips to get more bits resolution but that's 'cheating', hehe) and make your own stick which is not for the faint of heart or mind. The hard part could be making acceptable knobs, grips, and bases, ie the mechanical bits. Plaster molds and bondo then hours of sanding, filling, etc? I can code the latter and breadboard them but have no shop space and am lousy at soldering and fine work due to shaky hands. The newer controllers and software (since 200  make it easier than ever but I say that already knowing C since the 80's. Your mileage may vary, learning to code from zip may not be worth what you get. There's a lot of help available from Leo for his products (already coded) and on the Arduino forum for those.In the last two years I have recovered/relearned a lot of my old "skillz" playing with Arduino. I have even made leds that self-adjust with changes to ambient light (LOL Fehler, how much resistor? MINE changes itself!).
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#8
06-28-2013, 08:29 PM
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The pots that CH used for my old yoke are all 270 ohms, but they use only the 'middle range' of the pots because that is where the change in resistance is most consistent; the resistance between the 10th and 11th degrees is almost exactly the same as the resistance between degrees 45 and 46. This allows them to use less expensive pots and still give you pretty good precision across the range of movement that their mechanical setup allows. Since little Joey only cracked the plastic case and one of the Yoke handles (it was only a drop of about six feet!), I was able to recover the CH control circuit card as well as the five axes and the 12 buttons plus POV hat; this means that when I plug the USB into my computer it sees a CH Yoke and automatically puts me into the CH Control Manager software, which allows me to combine it with my other CH controllers into one or two (rather than four or five) controllers for Il-2, which I'd rather not lose. I was able to cut out the throttle/prop pitch/mixture levers' mounts so those three axes are intact, while the X-Y axes are now mounted in the box as twist knobs, with that short range of movement I was complaining about; I'm wondering if rather than putting another potentiometer in series, it might be better to put one in parallel to get that fine control. I'm also still looking at those gear kits that Tamiya makes for robots and RF controlled vehicles with an eye to adapting one of those to my needs with something along the lines of 20:1 ratios. I'm not very familiar with programming (one course in Basic back in college 25 years ago), so tossing the little CH CCA is something I hesitate to do. cheers horseback
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#9
06-28-2013, 08:56 PM
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Two more charts and data tables; USN/USMC fighters at 100m/330ft, and Mid-War Soviet Fighters @100m/330ft.
A few notes: 1. The Soviet fighters really shine at this altitude (this means that I said "Holy *&^%*&%$%!!!!" a lot when I reviewed the data and had to slow the track down to half or quarter speed to catch the speed changes in time); compared to the 3000m data, they are far more impressive. The La-5FN is indisputably 'king of the hill' at this level, although I have yet to do the Seafire LF III. 2. The Soviet fighters also tended to drop their noses as speed increased, generally around the 360 to 400 kph range, but it was only about half the radius of the gunsight circle in WW view. I started taking screenshots at certain intervals to confirm this, so I am certain that it is happening. 3. The USN/USMC fighters are mostly 4.11.1 versions that I had already completed before the patch was released; after three comparisons to 4.12 runs, it became obvious that there were no changes. 4. I haven't had a chance to do the same sort of screen shot comparisons with the Corsair and Hellcat that I did with the Soviet fighters because the idea didn't come to me until I was doing the Russian runs; I have started a folder labeled 'nose drops' and will use it for fodder on another thread, I think. 5. Using Max' suggestion of applying 50% filter to my ailerons, elevator and rudder axes made some difference; still, very tiny movements in elevator or rudder when I attention wandered from the climb or alt indicator or artificial horizon (and when these instruments are obscured or widely separated, I had some real issues) resulted in big swoops and climbs in a matter of two or three seconds, often well out of proportion to the indicated displays (as mentioned in an earlier post) Enjoy, discuss, debate. cheers horseback
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#10
06-28-2013, 10:16 PM
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Hybrid Mode
