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#61
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*********A DEFENCE FOR MXMORAN***********
In article ,
Mxsmanic wrote: Mike Ash writes: Pray tell, how do you avoid running into walls, falling down stairs, getting hit by cars, etc. when you do that? The question is one of equilibrium, not obstacle avoidance. There are no stairs, walls, or cars in the air. It is possible to walk competently for an indefinite period with one's eyes closed. It is not possible to fly competently for any significant period with eyes closed. No, the question is whether "you can't rely on this sense alone" is equivalent to "this sense is not useful". Walking consists of a LOT more than staying upright. Close your eyes next time you're walking down the street and see how long it takes you to get hit by a bus. Clearly you need your eyes. And yet, your sense of balance is still useful. So it is with physical sensations in VMC. -- Mike Ash Radio Free Earth Broadcasting from our climate-controlled studios deep inside the Moon |
#62
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*********A DEFENCE FOR MXMORAN***********
On Mar 5, 9:27
And now, for something entirely different! What you don't know about, I have to measure for a living. You fly code that is barely close to a PCATD. Thats a joke approval wise. You answer about 10 questions in a 5-10 page document, and you promise to get reapproval if you make hardware or flight model changes to the unit. A busy guy from the local FSDO comes out and test flys it for about 30 minutes to sign you off. Its a formality at best. There are small minutae in the rules for the quality of the visuals, and how the flight model has to handle, but no specs on how tight the timing loops in the software must match the real aircraft. IN MS, you are always about 150-200 mS , ie one tenth to two tenths of a second or more behind the flight model on the visuals, and your flight model is updating every 16.76 ms, and that is tied to the monitor vertical refresh rate, which is one of the few accurate timing sources on a PC platform under windows. In fact window's timing varies all over the place. As a result, they have to do a lot of fudges in the code to smooth things out. From the 1978 Skyhawk manual, 65 KIAS is the recommended speed for just about everything. One knot is 1.68 feet per second. So at 65 knots your doing 109 feet per second. A 200 mS error at 109 feet per second is 22 feet on the runway distance or roughly 5 feet on a 3 degree glide slope. So your +/- 10 feet visually off or below the runway in software at any given time right as your wheels hit. Lets recalculate that for a F18. FAS.org claims 134 knots approach, your moving 226 feet per second, and on a 3' glide slope thats 11 feet. Since your always at least 200 mS behind, you have a potential error of +/- 22 feet at that airspeed and that update rate. Moral of the story, FS is helping you land with a software fudge, because the granularity of your visual corrections is very rough as you get close to the ground. In a real aircraft, there are cables and servosystems, they react nearly instantly, but there is no software fudge on a manual landing. Yet in MSFS, even a 10 year old kid can hit the edge of the stripes on the runway time after time, because the visual update rates must be slowed close to the ground. The math says it has to be, or you would miss the deck by some multiple of 22 feet. IN a real aircraft, there is no 22 foot vertical fudge. Plus that doesn't include the average human's .1 second reaction rate. How do we measure that 200 mS delay?, there are a couple of ways. You can command a max roll on the stick and measure the time to the aircrafts maximum roll rate analysing the video on a tape frame by frame. Or you can have a switch on the stick, a special pixel programmed to flip from black to white, and a digital timer with a photosensor. I know for a fact the delay on FS04 is roughly 150 mS minimum from max command input to a visual change. That is a measured value. FS10 will be no faster, its a hardware thing. So if we put you in a real aircraft, you've been trained to compensate for a time lag on all your reactions. That is a Bad thing. Next up, lets talk about your feel for the controls. You invariably have a 8 bit control resolution on your joystick, ie your stick position is one possible position in 256 available. So lets say your joystick swings +/- 20 degrees, that means you need to move your stick 7 degrees before the software even notices it. You move a real yoke 7 degrees and your gonna really be rolling or pitching. So your already trained to overcontrol if we plop you in that 747 cockpit. Oh and it gets worse. To smooth things out, you'll find that in slow flight MS and other simulators condition you to jerk the controls quite a bit to get motion started in the above mentioned landing mode. Its control law smoothing, and its done to make you feel comfortable as you approach the ground, otherwise with that 200 mS lag, you'd come darn close grinding a wing tip into the ground from the roll error every time. The real aircraft, other then control system friction and cable stretching, has unlimited resolution, and the flight response shows it. MS does a lot of fudging to make your flight smooth and landings easy. The real thing doesn't. Heck, with those errors how do you think people can catch the wire in carrier landings on consumer sim software, time after time? The answer is the flight model code is doing it for you. Especially when landing. Still think you'd make it if we stuck you a in a real plane alone? Odds are you'd lead or lag in time so much on the landing you'd break the gear or cartwheel. Your conditioned to do it by the code and the system timing and control resolution. I'm curious, is your sim set up so one PC runs the flight model and controls and the other does the visuals? Or do you just have one machine and one graphics card? . Because we need one dedicated flight model machine just to get rid of the lag. And we use 10 bit controls, and I'm being asked for more resolution. Oh, dont get me started on flight models. Look at a real Bell 206. It does have horizontal stabilizers, does it not? If you look closely the airfoil is inverted on them. Well, most flight models put them in as flat planes. This causes the aircraft to oscillate in pitch as the airspeed increases. It took a long while to figure out that the guy who did the flight model was wrong on that. In one very popular sim, the rotorcraft model is a cessna 172 body with a rotor added and the wing removed, and the tail rotor and main rotors are defined as a thrusters. Because their is no rotor disk in the form of a wing , Ground effect does not show up on approach. Your basic sim software is very unlike the real thing. Steve |
#63
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*********A DEFENCE FOR MXMORAN***********
On Mar 5, 9:33*pm, wrote:
On Mar 5, 9:27 *And now, for something entirely different! [snip for brevity] Great post, Steve! * Your basic sim software is very unlike the real thing. Indeed. The Human Factors group here has done extensive research which bears this out. Regards, Jon "This will end your Windows session. Would you like to play another game?" |
#64
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*********A DEFENCE FOR MXMORAN***********
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#65
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*********A DEFENCE FOR MXMORAN***********
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#66
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*********A DEFENCE FOR MXMORAN***********
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#68
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*********A DEFENCE FOR MXMORAN***********
"Mxsmanic" wrote in message ... writes: Close enough to be safe and satisfy the tower, since in real life those are the relevant criteria. What was the exact figure? 3.2 miles? 3.0004 miles? 4.5 miles? You clearly answered that one yourself, dumb ass. |
#69
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*********A DEFENCE FOR MXMORAN***********
Mxsmanic wrote:
writes: Close enough to be safe and satisfy the tower, since in real life those are the relevant criteria. What was the exact figure? 3.2 miles? 3.0004 miles? 4.5 miles? Close enough to be safe and satisfy the tower, since in real life those are the relevant criteria and no one cares about putting error bars on the number. No one but an anal retentive buffoon would ask such an asinine question. -- Jim Pennino Remove .spam.sux to reply. |
#70
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*********A DEFENCE FOR MXMORAN***********
Mxsmanic wrote:
writes: And if it doesn't move, the movement relative to the nose of the aircraft is, wait for it, zero. In the sim, I have the nose of the aircraft turned off most of the time, but I can see what is moving with respect to the screen borders, which serves the same purpose (MSFS also provides a guide that you can optionally put on the screen, if you need it). Whoopee!!! It went right over your head, didn't it? In a real airplane you don't have screen borders, a nose you can turn off, or a "guide" you can turn on. -- Jim Pennino Remove .spam.sux to reply. |
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