SwingKid

You'll forgive me, but in post #175, it wasn't clear that you were talking about 40,000 feet at all. I'm not sure why you keep repeating this, since nobody seems to disagree with it. If you mean to say that "same at 10,000" automatically proves "same at 40,000", then we disagree. I'm afraid I don't understand this. I can gain altitude, even without accelerating. (?) When I followed your suggestion to calculate the TAS of Mach 0.9 at different altitudes, I was suddenly reminded that above 30,000 feet, there is an inversion - the TAS for a given Mach begins to decrease with altitude, and then to stabilize at around 35,000 feet. I began to wonder if maybe Lock On is not modelling the aircraft incorrectly, but rather - the air above 30,000 feet? I didn't test the idea further. If you mean my "Average error" - that is not a simple function, because the angle of the climb changes from the start to the finish of the climb. At low altitude, distance vs. time is small, while at high altitude, it's much larger. But the "averaging" only looks at the total time and the total distance. They are not proportional, so they have different percentage errors. Anyway, the "average error" is not a very useful calculation. If you look at the green bars in the charts, the specific errors near 35,000 and 40,000 feet seem very similar for both time and distance, as one would expect. -SK

I was doing that. -SK

I made an error in my distance calculation. I edited my post - the distance discrepancy should have said 46%, not 228%. After a compliment like that, how can I refuse? :) Ok, I calculated the true airspeeds in km/h for each altitude level and flew the Dash-1 climb profile again. Here is what I found, flying in mil power more precisely this time: Time to 40,000' in Lock On: 6:21 min Time to 40,000' by Dash-1: 4:30 min Average error: 41% Distance to 40,000' in Lock On: 50.3 nm Distance to 40,000' by Dash-1: 38 nm Average error: 32% However, Rhen's problem is even more severe than it appears above. This is because my "Average error" includes both the climb portion at low altitude, where the error is zero, AND the error at high altitude, which is larger than the above percentages would suggest. Consider: The red dots represent my climb measurements in military power. Notice that for climbs to an altitude of 25,000 feet or less, the Lock On model is quite accurate - the red dots are touching the curves where they are supposed to be. The vast majority of the error (green bars) happens when the Lock On F-15C pilot tries to climb from 35,000 to 40,000 feet - in this region, the red dots are quite far from their correct locations. This means that most of the cumulative "41%/32%" time/distance error is being created in a quite narrow altitude band, where it is probably much larger than that. (Note: the first chart is from the Dash-1 time-to-climb chart for military power, the second is from the distance-to-climb chart) Can't we calculate this from the Streak Eagle data? -SK P.S. Someone please tell me if the following track plays correctly, because I might have accidentally recorded it on an incompatible beta version: http://www.ecf.utoronto.ca/~pavacic/lomac/f15milcl.zip

Thanks for the response Rhen. The high-altitude, mil-power regime is obviously important to you, and for this case I agree the Dash-1 figures are the way to go. The low-altitude, max-power regime is of more interest to me, because it lets me isolate a few parameters at a time for testing, without worrying about ram drag or other complications. I still believe that unless we get the low-altitude, max-power regime correct, there is no way to "bump up the thrust" at higher altitudes. That is basically a hack - it might make connecting to the tanker easier, but things like that can throw off the whole balance in air combat. And for the low-altitude, max-thrust regime, the Dash-1 lets me down in precision of langugage, by interchanging "1 nm" with "negligible," and other approximations. For low-altitude, max-power, the Streak Eagle records are IMHO a much better reference, and that is what I considered this whole thread to be about. So in essence there seem to be two problems - one above Yo-yo's "sweet spot" of 10,000 feet altitude where everything magically seems to work out in his charts, and another one below. And they seem to affect all SFM aircraft, one way or another. The question is - having identified these problems, how does Yo-yo proceed to a solution? If you feel that the low-alt performance can be tolerated, and the high-alt thrust can just be "bumped up" to compensate even if the error is in drag or something else, then I guess we should just respectfully agree to disagree. Something as complex as a combat sim flight model does not lend itself well to quick-hack, end-of-pipe solutions, IMHO. The unforeseen consequences of such changes always seem enormous afterward - e.g. the "Tunguskas shooting down Mavericks" affair, when they tried to allow Patriots to shoot down ARMs. I want to know exactly what is causing the problem, and attack it at its source. Cheers, -SK

Since the afterburning thrust is similar to the 23,450 lbf of the F100-PW-220, we'll assume that the military thrust is also similar. Based on that, I have found the following result for maximum military thrust: Lock On F-15C: ~23,100 lbf thrust Real F-15C: ~29340 lbf thrust Lock On F-15C underpowered in military thrust by: 21.3% Note that from post #145, we found that in the afterburning regime, the Lock On F-15C was underpowered by 27.5%. So, it would appear that at sea level, max thrust is actually significantly more wrong than mil thrust in Lock On. I've also tried to fly Rhen's test of a climb to 40,000 feet at mil power. I seriously doubt the precision of this kind of test, since it relies on maintaining a speed of Mach 0.9 by watching a Mach meter that is graduated in units of 0.5. The KCAS dial also reads a different value than the HUD, calling into question the claim that one is "maintaining 350 KCAS." The whole test seems to mainly involves holding a pitch of around 6.5 degrees for about 6 minutes, and feels extremely "mushy." If I wasn't at 0.9 Mach like I thought, then over six minutes, huge errors are going to appear in my measurement, and the whole test is worthless. That being said, my result was: Time to 40,000' in Lock On: 7:07 min Time to 40,000' by Dash-1: 4:30 min Lock On climb performance underpowered by: 58% Distance to 40,000' in Lock On: 55.3 nm (corrected 2007/04/30) Distance to 40,000' by Dash-1: 38 nm Lock On climb performance underpowered by: 46% (corrected 2007/04/30) -SK

If you feel this way (and I have a lot of respect for you as a "voice of reason"), then it seems that the discussion has moved well past what the title of the thread, and the first post in it, have anything to do with - without ever having solved the basic discrepancy exposed in post #145. In that sense, I think it's appropriate now to ask D-Scythe what exactly he feels he accomplished by starting this topic at all, and dragging my good name into it. :) "Are you not entertained??" -SK

(Sorry to skip ahead, I'll probably reply to other stuff later) Out of curiosity - how do you resolve the apparent contradiction that the Lock On SFM follows the Dash-1, the Dash-1 is good enough for the real pilots, but the Lock On SFM is not good enough for the real pilots? -SK

Correct. I would agree, not only for this chart, but also for others in the Dash-1. The low-altitude lines all look like someone took a ruler and just drew a stright line through (0,0) - without any regard for what this physically means. That's the whole point I'm trying to make - to Yo-yo, to Rhen, to anyone who is interested. The Dash-1 contains some data that is too approximate for our use. Back up a bit, I think you have misunderstood the order of cause and effect that I'm trying to present: (1) By F=m*a, I have established, beyond any reasonable doubt, that the sea level thrust of the F-15C in Lock On does not exceed 34,000 lbf. (2) Despite this, the sea level performance of the F-15C in Lock On matches the Dash-1. (3) Therefore, the Dash-1 does not describe the sea level performance of the 47,000 lbf F-15C correctly. (3) follows from (1) and (2), not the other way around. Me? Of course. I use the Streak Eagle data, which has so far given me no such ridiculous contradictions. Does the Dash-1 have more useful charts? No. They are all like that - straight lines that somebody drew with a ruler down from high altitude to the artifically fixed point of (0,0). I have some more data, but it is MUCH more complicated to analyze. It's basically a graph of airspeed, altitue, Gs, turn rate, turn radius, etc. during a mock dogfight between an F-15 and an A-4. Beautiful stuff, but if we can't even agree on what thrust the F-15C should be producing at takeoff, and whether tLock On and/or the Dash-1 describe it correctly, then we have little hope of analyzing that. Trouble is, do we know what the mil power thrust is supposed to be? Much easier to analyze max power, I think. That thrust evel is published in many places, and is more easily verifiable. Walk before we run. -SK

The fact you can do all of the above, with only 34,000 lbf thrust. A real F-15 has 47,000. http://forum.lockon.ru/showthread.php?p=323739#post323739 Therefore, matching the Dash-1 = underpowering the F-15. -SK

Hmm, I don't think anybody in these 22 pages is complaining about performance at 10,000 feet. -SK

Well that's an interesting change of topic, but it's not what the Dash-1 says, and it's not what I was asking. Please, let's clarify with an illustration: First, I have taken the liberty of marking the part of the Dash-1 that YOU said to disregard with a big red "X" Now, let's turn our attention to the region of the Dash-1 chart that is in the blue circle. What we're looking at here is the curve labeled "5,000 FT." In particular, note how unlike all the other curves on this chart, the 5,000-ft curve becomes perfectly vertical as we follow it downwards. The two purple arrows indicate the gross weights of 30,000 and 45,000 lbs. Between these two arrows, the 5,00 ft curve is vertical. It is NOT vertical between 40,000 and 50,000 lbs. That's why in this post: http://forum.lockon.ru/showthread.php?p=323798#post323798 I am asking about 30,000 lbs and 45,000 lbs. The Dash-1 chart claims that regardless of this weight difference of 50%, the F-15 will require the exact same horizontal distance to climb to 5,000 feet, and that the horizontal distance is 1.0 nm. It makes no such claim for an F-15 increasing its weight from 40,000 to 50,000 lbs. What do you think? Is the Dash-1 chart correct about this? -SK

What's wrong with http://forum.lockon.ru/showthread.php?p=321044#post321044 and http://forum.lockon.ru/showthread.php?p=322900#post322900 ? -SK

Of course, I have accounted for both. The bench thrust is at a speed of zero. The thrust that I measured in Lock On is also at a speed of zero. At zero speed, ram loss is also zero, both for the real F-15C and for Lock On. -SK

You mean to say that below 5000 feet, a 45,000 lb F-15 climbs the same as a 30,000 lb F-15? -SK

Huh? MAX (47klbf) thrust will take a 30klb F-15 from 0 to 350 KCAS in about 12 seconds, over a distance of 0.6 nm. What does the Dash-1 expect that we're doing for the next 0.4 nm/18 seconds, in order to prevent our F-15 from accelerating past 350 KCAS, before we start our climb? Turning loops in a holding pattern over the runway? :) -SK

Rhen, I hesitate to say, "the Dash-1 is full of crap," but I think you'll be forced to agree that its information is not appropriate for the type of performance modelling we need in Lock On. Consider the following chart. It dosn't take a rocket scientist - anyone who's watched a Viking takeoff at an airshow will know that a 30,000-pound aircraft with 47,000 lbf engine thrust does NOT need two nautical miles of horizontal distance to reach a mere 5,000 feet of altitude. The problem is that we're focusing on a tiny corner of the Dash-1 chart, where most of our sim flying is done, but that part of the chart is just a ruler-drawn extrapolation of the performance of MUCH heavier, draggier F-15s to much higher altitudes - which is what most of the Dash-1 is about. This crude level of approximation in the low-altitude, low-weight, low-drag parts of the chart(s) is NOT sufficiently precise of a reference for our simulator. How did the underpowered engine thrust get past beta testing? Well of course - it didn't. As D-Scythe has already indicated, we've been reporting and complaining about this for years. Unfortunately, somebody keeps telling ED that "the Dash-1 is correct," so we never get listened to! ;) -SK

From what I understood, the instructor says that the gunsight used in the MiG-21 was basically the same as in the MiG-15 - designed for gunfights, not missile combat. As a result, the Vietnamese pilots needed to be trained flying in two-seaters, how to judge the distance to the F-4, and to hold their fire until they were close enough for the shot. -SK

What, you trust an Eagle pilot and his "Dash-1" nonsense over me?? You'll live to regret that. :) Check PM -SK

Already accounted for. -SK

You mean how I pause the game, and then press Ctrl-Enter to advance one frame at a time while paused? What the devil - that's not listed in the keycommands?! Where did I learn about it..? Tester's tricks. :) -SK

What do you mean? I quoted myself describing the method. I added 2,500 lbf VMAX bonus per engine (cited from ref. 1) to the 23,830 lbf F100-PW-100 thrust (cited from ref. 2). 1. J.P. Stevenson, "McDonnell Douglas F-15 Eagle", Aero Series #28, 1978. 2. D.R. Jenkins, "McDonnell Douglas F-15 Eagle", Aerofax, 1998.

Hey, that's a great idea SwingKid, why didn't I think of that? Lock On F-15C: ~34,000 lbf thrust real F-15C: 46,900 lbf thrust Streak Eagle: ~52,700 lbf thrust Lock On F-15C underpowered by: 27.5% Streak Eagle more powerful than real F-15C by: 12.4% Well look at that, the Streak Eagle is a much better approximation of the real thing than the Lock On F-15C! Who would have known. D-Scythe, apparently. For comparison: Lock On Su-27: ~18,600 kgf thrust real Su-27: 25,000 kgf thrust Lock On Su-27 underpowered by: 25.6% Lock On MiG-29: ~14,000 kgf thrust real MiG-29: 16,600 kgf thrust Lock On MiG-29 underpowered by: 15.7% No wonder, we have little problem accelerating vertically in Lock On's MiG-29... -SK

To me, it's apparent that they are flying an aircraft with MUCH more thrust. No, they are qute specifically measuring all the record times from the moment of brake release, as you can see in some of the labels: http://www.ecf.utoronto.ca/~pavacic/lomac/f15climb07.jpg Another one of my favourites: http://www.ecf.utoronto.ca/~pavacic/lomac/f15climb06.jpg Out-climbs an Apollo moon rocket to 60,000 feet :) -SK

Really? I consider it an already-done deal, that they are just leaking to us slowly to create the facade of a public debate. (e.g. invading Iraq, missile defense, etc.) I'd sooner predict forbidding US companies from doing business in China, than denying the IAF a conventional weapon. -SK

It's called a "collimator" - basically a normal convex or flat Fresnel lens, with the subject being located at a certain focal distance. A flight sim application: http://www.rickleephoto.com/rlcoll.htm -SK