S77th-GOYA Posted June 17, 2006 Posted June 17, 2006 What did the Mach meter say? Speed of sound varies with altitude, so I dunno how fast that is. At 36,089 feet, geopotential of tropopause, Mach 1 is 573.8 knots. At 45,000 Mach 1 is still 573.8 knots. See Chart A here: http://www.grc.nasa.gov/WWW/K-12/WindTunnel/Activities/lift_formula.html My original testing was done intentionally just above geopotential of tropopause. So, at 45,000 the 15 is slower than my original test. Another thing to consider is fuel load. The speeds acheived in Yo-Yo's chart were certainly not just before flame out. That makes LOMAC's modelling appear even worse.
TucksonSonny Posted June 17, 2006 Posted June 17, 2006 Anyway, just did a test myself. Set temperature to -10 degrees C, altitude 13600 m (45 300ft approx), started in the air with 50% fuel, 2600 kmph (almost Mach 2.39). Ran fuel down to zero. According to this chart, I should be hitting Mach 2.5, although it would put me in the "red" zone. With 1000 lbs of fuel left, my speed was only Mach 2.34, and not accelerating. Temp at 50k+ should be about -70°C. I wonder if this is modeled. DELL Intel® Core™ i7 Processor 940 2,93 GHz @3 GHz, 8 MB cache | 8.192 MB 1.067 MHz Tri Channel DDR3 | 512 MB ATI® Radeon™ 4850 | 500 GB 7200 rpm Serial ATA | Samsung SM 2693 HM 25.5 " | HOTAS Cougar Thrustmaster |
S77th-GOYA Posted June 17, 2006 Posted June 17, 2006 Set temperature to -10 degrees C The isn't at -10 degrees C, it's 10 degrees C less than standard atmosphere. http://www.desktopaero.com/stdatm.html
D-Scythe Posted June 17, 2006 Posted June 17, 2006 The isn't at -10 degrees C, it's 10 degrees C less than standard atmosphere. http://www.desktopaero.com/stdatm.html True, but I don't know the temperature at 13600 m in LOMAC. Since I can't remember what standard atmosphere was, and since I'm assuming that Lock On uses some sort of scaling system of temperature vs. altitude, I just set the normal temperature -10 degrees Celsius and hoped I was right. EDIT: Anyway, looked into it a bit deeper. The brick wall effect is noticeable at Mach 2.5 here as well, so the Eagle probably has enough power to go faster. Unfortunately, even in my very favourable test at 46 000 ft (where the F-15 has already established altitude and speed, and has the luxury of accelerating to flame out), LOMAC's F-15 is still over 6% slower than an F-15 with the Mach 2.5 absolute airspeed limit. The wing weapons pylons probably factor in a bit to reduce overall speed, but we in LOMAC have the luxury of starting at altitude and speed, and running our F-15 until its tanks are dry, which should make up for it somewhat. In any case, even if Mach 2.5+ is unrealistic, it still seems that LOMAC's F-15 is definitely lacking a bit in power at altitude - I'd be expecting speeds over Mach 2.4 at least.
S77th-GOYA Posted June 17, 2006 Posted June 17, 2006 True, but I don't know the temperature at 13600 m in LOMAC. Since I can't remember what standard atmosphere was, and since I'm assuming that Lock On uses some sort of scaling system of temperature vs. altitude, I just set the normal temperature -10 degrees Celsius and hoped I was right. A sea level temperature of 15 degrees C is standard. IF LOMAC models a standard atmosphere, an in game setting of 5 degrees C should give the 15 mach 2.5 @ 45,000 feet.
D-Scythe Posted June 17, 2006 Posted June 17, 2006 A sea level temperature of 15 degrees C is standard. IF LOMAC models a standard atmosphere, an in game setting of 5 degrees C should give the 15 mach 2.5 @ 45,000 feet. Well, setting temperature to -10 degrees celsius shouldn't hurt max speed, IMO, but I'll retry my test a bit later at 5 degrees.
S77th-GOYA Posted June 17, 2006 Posted June 17, 2006 Well, setting temperature to -10 degrees celsius shouldn't hurt max speed, IMO, but I'll retry my test a bit later at 5 degrees. I agree. Just trying to be precise (pedantic, if you want). If you noticed, my test at 45k was less than freezing as well. The LOMAC 15 has been tested to be underpowered from sea-level on up. What seems to be the enigma is how ED models thrust v drag v altitude. (and possibly lift v gravity, as well) Because it doesn't seem to match reality.
GGTharos Posted June 17, 2006 Posted June 17, 2006 For the joke once I was cruising back to the home plate with a clean su-27 on HL 504th server @45k+ alt speeding between Mach 2.2 and reaching Mach 2.4 in the end with almost no fuel left. The enemy was as usual flying @2000-5000m and in large numbers below me. It was a surprise for me that nobody was able to intercept me or catch up with me and some even did not notice me (I guess the alt difference and speed advantage). I wonder why almost everyone prefers low altitude (I guess dodging/outrunning missiles in thick air is one reason) It's because avionics and missiles aren't modelled very realistically. Consider this: Fighter aircraft are built to get up to high altitude /quickly/ ... you can thus deduce that this is the preferred combat environment. According to a real F-15C pilot, anything that gets down low and slow is DEAD; for one, your own radar does a number on itself (does not happen in LOMAC) second, missiles coming down from above won't lose you (in LOMAC, they do) and third, you're not outmaneuvering squat at that speed. These factors to a large degree cause people to fly in the weeds, which is not proper fighter tactics for offense against high-flying fighters. It also lowersyour missile range which again is not properly modelled in LOMAC. Basically, being low should mean you're on the defensive. In addition being low and slow should be you're landing, or surredendering, 'cause realistically the only thing you're achieving in that position is making yourself an easy target. Recall the truck that was destroyed by an F-15C launching an AIM-7, using AA radar because for some reason AWACS thought it was a helo. Your plane's min flying speed in likely quite a bit above that of the truck's max speed. You're not getting away ... but in LOMAC, you can, because radar missiles are too easy to spoof, it's too easy to break lock, and radar missiles won't track below a certain altitude. Ehm ... /rant. [sIGPIC][/sIGPIC] Reminder: SAM = Speed Bump :D I used to play flight sims like you, but then I took a slammer to the knee - Yoda
GGTharos Posted June 17, 2006 Posted June 17, 2006 I agree. Just trying to be precise (pedantic, if you want). If you noticed, my test at 45k was less than freezing as well. The LOMAC 15 has been tested to be underpowered from sea-level on up. What seems to be the enigma is how ED models thrust v drag v altitude. (and possibly lift v gravity, as well) Because it doesn't seem to match reality. I would say that it 'doesn't match reality very well' ... but close. I think once the F-15C is transitioned to AFM (whenever that happens) we will see much more accurate performance. [sIGPIC][/sIGPIC] Reminder: SAM = Speed Bump :D I used to play flight sims like you, but then I took a slammer to the knee - Yoda
D-Scythe Posted June 17, 2006 Posted June 17, 2006 I agree. Just trying to be precise (pedantic, if you want). If you noticed, my test at 45k was less than freezing as well. The LOMAC 15 has been tested to be underpowered from sea-level on up. What seems to be the enigma is how ED models thrust v drag v altitude. (and possibly lift v gravity, as well) Because it doesn't seem to match reality. Actually, (I don't know if I'm supposed to disclose this), but Swingkid and ED had a pretty big discussion about this during V1.2 beta testing, and in terms of climb rate at low to medium altitudes, LOMAC's F-15 matched the real F-15 to the second. Thus, even though I won't say that the F-15 isn't underpowered at low/medium altitudes, but it seems very likely that the Eagle's performance at high altitude is not quite right. It definitely seems to be underperforming at high altitudes.
S77th-GOYA Posted June 17, 2006 Posted June 17, 2006 in terms of climb rate at low to medium altitudes, LOMAC's F-15 matched the real F-15 to the second. No, it matched the USAAF's climb schedule. Not the max performance of the plane itself. The thread's around here somewhere. Even SwingKid finally realized that the 15's thrust was very much undermodelled. The thread was about vertical acceleration, if you want to search for it. here: http://forum.lockon.ru/showthread.php?t=15815&page=5&highlight=vertical+acceleration
D-Scythe Posted June 17, 2006 Posted June 17, 2006 Yup, you guys are absolutely correct. I remember that thread, but didn't realize it was more "up-to-date". Hmm, this does seem to be a problem then.
Rhen Posted June 17, 2006 Posted June 17, 2006 Goya, just to answer your question from that thread, IIRC. Thrust loss per 5000ft is about 15%, up to about 20,000ft, from there it goes up to about 16-17%. These numbers are based on a Standard Aeronautical Day, with normal lapse rate, to tropopause, and in mil power at M0.95. Afterburner numbers are pretty close to this too, but thrust falls off a little quicker at higher altitudes - negligible, an increase of 1-2% above 20k IIRC. This is for the F100 PW-220, which is what I'm most familiar. The -100 is similar, with a slightly higher starting thrust and more unstable because of lack of DEEC. Gotta like the DEEC - allows you to slam the throttle around and still not stall/flameout the engines at high altitude/alpha.
GGTharos Posted June 17, 2006 Posted June 17, 2006 Hm. So you're already under 1:1 TWR by the time you reach 10000'. [sIGPIC][/sIGPIC] Reminder: SAM = Speed Bump :D I used to play flight sims like you, but then I took a slammer to the knee - Yoda
S77th-GOYA Posted June 17, 2006 Posted June 17, 2006 Hm. So you're already under 1:1 TWR by the time you reach 10000'. Depends on weight doesn't it? Clean with a 25% fuel load would likely still be above 1:1 at 10k ft. And Rhen, how much does speed change the thrust of those engines? As a side note, notice how the design limit changes depending on engine trim on Yo-Yo's chart?
Rhen Posted June 17, 2006 Posted June 17, 2006 Thrust increases by 5% per engine for each M0.1 increase in speed - approximately, IIRC, from mach numbers from 0.7 to afterburner engagement, at 10,000ft. Numbers vary with altitude, airspeed, and temperature. Drag/weight also plays a factor, but strictly speaking, letting 2 F100 PW220s flying formation with each other with variable inlets but without an aircraft around them, this should be fairly accurate. Btw, as a pilot, these numbers aren't what we remember. We remember the "dog house" charts. These numbers are interesting to know, but usually slip most fighter pilot's minds. As a Chem major in college, numbers tended to stick better with me than most. Oh, yeah. Engine trim - not trimmed to 102%. Why? Because engines cost money. It's just like the VMax switch, which stays safety wired shut - for the most part. :smilewink: For the reg happy out there - the Dash 1 states that use of the VMax switch is prohibited.
upyr1 Posted June 17, 2006 Posted June 17, 2006 Note that this is the F-15A manual. It is entirely possible that the F-15C has greater static thrust (ie. non afterburning) even though the max thrust is lower, and thus might perform in exactly this manner in real life in the lower altitude regime. This type of enhancement is what the A-10C is going to receive ... the max thrust isn't increasing, but the available thrust at a given altitude is, which will solve many problems for this aircraft. Thanks for noting that this if this is F-15A of F-15C manual as that would offer to explenations about why the diagrmas don't match either the LOMAC being a pure mathmatical version dose not modle structual limits or b. as the LOMAC modle is the F-15C improvments to the trust to weight ratio have have resulted in improved preformance.
D-Scythe Posted June 17, 2006 Posted June 17, 2006 Oh, yeah. Engine trim - not trimmed to 102%. Why? Because engines cost money. It's just like the VMax switch, which stays safety wired shut - for the most part. :smilewink: For the reg happy out there - the Dash 1 states that use of the VMax switch is prohibited. Wouldn't the engines be trimmed as such in combat though? In any case, here's the figures for the F100-PW-220 engine, taken from Falcon 4's HFFM. Taken without permission, so if these figures do show up among some of you in the future, please give full credit to the HFFM crew. Another thing, I know that the performance of the 220 on the F-16 would not be the same as the performance of the 220 on the F-15C, especially around Mach 2 and above (due to the variable inlets on the F-15C and the F-16's lack there of), but it's a good way to get a general picture of engine performance, I think. EDIT: Apologize, it's also a bit hard to read. But each number corresponds to a certain speed, and each set of numbers correspond to the indicated altitude. 19 # Number of Mach Breaks 0 0.2 0.4 0.6 0.8 0.9 1.0 1.1 1.2 1.3 1.4 1.5 1.6 1.7 1.8 1.9 2.0 2.1 2.2 # THRST2 - THRUST AT MIL POWER (THROTL = 1.00) # # Alt 0 12500 12330 12260 12290 12350 12250 12050 11501 10820 10129 9455 8873 8385 7971 7625 7342 7108 6944 6797 # # Alt 10000 9100 9100 9300 9800 9950 9870 9680 9325 8897 8475 8018 7613 7230 6917 6630 6403 6213 6037 5913 # # Alt 20000 5900 6000 6300 6750 7650 7930 7890 7675 7400 7117 6867 6646 6517 6425 6316 6283 6270 6250 6224 # # Alt 30000 3720 3840 4090 4460 5120 5575 5800 5893 6034 6111 6194 6268 6379 6438 6490 6528 6562 6650 6667 # # Alt 40000 2400 2470 2600 2840 3250 3500 3800 4182 4609 5083 5600 6054 6544 7042 7475 7910 8282 8655 8972 # # Alt 50000 1325 1400 1560 1750 2150 2400 2650 3054 3578 4103 4622 5130 5764 6266 6748 7208 7594 7940 8255 # # Alt 60000 700 750 860 975 1150 1275 1400 1600 1800 2000 2200 2400 2600 2800 3000 3200 3400 3600 3800 # # Alt 100000 57 56 62 66 77 84 92 102 114 128 143 159 166 168 169 169 169 168 164 # # THRST3 - THRUST AT FULL AB (THROTL = 1.05) # # Alt 0 22200 21420 22700 24240 26000 27000 28400 31600 33500 34400 34370 33495 31925 29790 27150 23985 20560 16855 12950 # # Alt 10000 16000 15700 16860 18910 21075 22100 23319 24700 26450 28250 30100 31250 31315 30770 29495 27735 25600 23225 20690 # # Alt 20000 10950 11225 12250 13760 15975 17100 18300 19750 21150 22350 23550 24150 24425 24290 23615 22680 21425 19875 18200 # # Alt 30000 7050 7323 8154 9285 11115 12150 13400 15250 16600 17250 17850 18450 19100 19550 19650 19515 19265 18840 18355 # # Alt 40000 4350 4435 4800 5400 6250 7100 8500 10100 11700 12400 12775 13125 13500 13900 14100 14260 14405 14520 14575 # # Alt 50000 2500 2600 2835 3215 3950 4500 5057 6000 7000 7750 8000 8200 8300 8350 8400 8510 8590 8710 8850 # # Alt 60000 1350 1400 1600 1800 2200 2450 2850 3400 4000 4350 4450 4500 4750 4615 4805 4880 4885 4905 4840 # # Alt 100000 163 163 177 201 247 281 316 375 438 484 516 531 541 547 550 550 550 547 531
Pilotasso Posted June 17, 2006 Posted June 17, 2006 Wouldn't the engines be trimmed as such in combat though? In any case, here's the figures for the F100-PW-220 engine, taken from Falcon 4's HFFM. Taken without permission, so if these figures do show up among some of you in the future, please give full credit to the HFFM crew. Another thing, I know that the performance of the 220 on the F-16 would not be the same as the performance of the 220 on the F-15C, especially around Mach 2 and above (due to the variable inlets on the F-15C and the F-16's lack there of), but it's a good way to get a general picture of engine performance, I think. EDIT: Apologize, it's also a bit hard to read. But each number corresponds to a certain speed, and each set of numbers correspond to the indicated altitude. 19 # Number of Mach Breaks 0 0.2 0.4 0.6 0.8 0.9 1.0 1.1 1.2 1.3 1.4 1.5 1.6 1.7 1.8 1.9 2.0 2.1 2.2 # THRST2 - THRUST AT MIL POWER (THROTL = 1.00) # # Alt 0 12500 12330 12260 12290 12350 12250 12050 11501 10820 10129 9455 8873 8385 7971 7625 7342 7108 6944 6797 # # Alt 10000 9100 9100 9300 9800 9950 9870 9680 9325 8897 8475 8018 7613 7230 6917 6630 6403 6213 6037 5913 # # Alt 20000 5900 6000 6300 6750 7650 7930 7890 7675 7400 7117 6867 6646 6517 6425 6316 6283 6270 6250 6224 # # Alt 30000 3720 3840 4090 4460 5120 5575 5800 5893 6034 6111 6194 6268 6379 6438 6490 6528 6562 6650 6667 # # Alt 40000 2400 2470 2600 2840 3250 3500 3800 4182 4609 5083 5600 6054 6544 7042 7475 7910 8282 8655 8972 # # Alt 50000 1325 1400 1560 1750 2150 2400 2650 3054 3578 4103 4622 5130 5764 6266 6748 7208 7594 7940 8255 # # Alt 60000 700 750 860 975 1150 1275 1400 1600 1800 2000 2200 2400 2600 2800 3000 3200 3400 3600 3800 # # Alt 100000 57 56 62 66 77 84 92 102 114 128 143 159 166 168 169 169 169 168 164 # # THRST3 - THRUST AT FULL AB (THROTL = 1.05) # # Alt 0 22200 21420 22700 24240 26000 27000 28400 31600 33500 34400 34370 33495 31925 29790 27150 23985 20560 16855 12950 # # Alt 10000 16000 15700 16860 18910 21075 22100 23319 24700 26450 28250 30100 31250 31315 30770 29495 27735 25600 23225 20690 # # Alt 20000 10950 11225 12250 13760 15975 17100 18300 19750 21150 22350 23550 24150 24425 24290 23615 22680 21425 19875 18200 # # Alt 30000 7050 7323 8154 9285 11115 12150 13400 15250 16600 17250 17850 18450 19100 19550 19650 19515 19265 18840 18355 # # Alt 40000 4350 4435 4800 5400 6250 7100 8500 10100 11700 12400 12775 13125 13500 13900 14100 14260 14405 14520 14575 # # Alt 50000 2500 2600 2835 3215 3950 4500 5057 6000 7000 7750 8000 8200 8300 8350 8400 8510 8590 8710 8850 # # Alt 60000 1350 1400 1600 1800 2200 2450 2850 3400 4000 4350 4450 4500 4750 4615 4805 4880 4885 4905 4840 # # Alt 100000 163 163 177 201 247 281 316 375 438 484 516 531 541 547 550 550 550 547 531 was that taken from F4? :D .
D-Scythe Posted June 17, 2006 Posted June 17, 2006 was that taken from F4? :D Of course. And I stated as much at the beginning of my post, as well as saying that it shouldn't be a totally accurate indication for the performance of the F-15C's F100-PW-220, especially at speeds approaching and beyond Mach 2, but they're numbers, and they look pretty. In any case, it seems that in certain regimes, even the Dash 220 can produce thrust in excess of 30 000 lbs of thrust. This is contrary to the thread that Goya quoted before, where Swingkid determined that there was little proof that the Dash 220 ever produced more than 20 500 lbs of thrust in the F-15C.
Pilotasso Posted June 17, 2006 Posted June 17, 2006 One more thing, how are the engines rating tests donne? 20500lbs of thrust are probably made in static testbeds. Gas powered machines usualy pick up power as they ingest more air with the increased speed. Sometimes that can lead to uncontrolled RPM buildup to the point of disintegration. .
Guest IguanaKing Posted June 17, 2006 Posted June 17, 2006 Air temperature is also a consideration in engine power. ;)
D-Scythe Posted June 17, 2006 Posted June 17, 2006 One more thing, how are the engines rating tests donne? 20500lbs of thrust are probably made in static testbeds. Gas powered machines usualy pick up power as they ingest more air with the increased speed. Sometimes that can lead to uncontrolled RPM buildup to the point of disintegration. No idea, but I'm sure Pratt and Whitney or General Electric know what they're doing. Whether they'd release such data to the public is another thing though. Furthermore, I'm sure Mav-JP and Raptor from the HFFM team, as well as ED, know what they're doing as well. There are literally hundreds of things to consider, dozens of complicated engineering formulas to solve, but I'm sure AFM and HFFM provide excellent representations of engine performance. But if the Dash 220 never actually do produce more than 20 500 lbs of thrust (number given by Swingkid) in LOMAC, that's a bit wrong. There seems to be plenty of places where the 220 produces more than 20 500 lbs in AB.
S77th-GOYA Posted June 17, 2006 Posted June 17, 2006 Swingkid determined that there was little proof that the Dash 220 ever produced more than 20 500 lbs of thrust in the F-15C. Ok, I just ran some more tests, and... I'm confused. I don't see any evidence, that Lock On's F-15C engines ever produce more than 41000 lbf thrust, if that. On the other hand, the time-to-height test matched very well. What's going on? -SK That was from testing LOMAC F-15. 1
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