Tango

Reheat can add 50% or more thrust, depending on the situation (it can add drag as well, but that is extremely specific as to when/if that occurs). P25-300 engine: Static thrust (kgf): 4100 Full static reheat (kgf): 6850 (60% increase). Full reheat, near Mach 1.0, sea level (kgf): 9900 Best regards, Tango.

Yes... 10% (at the top end) of any turbine is *significant*. It doesn't explain everything (see my idle glide test - 20 km from 7000 m when it should be 70 km!) but it will affect performance nonetheless. Best regards, Tango.

Even if you're able to maintain altitude/speed (MIL power? No reheat?) your climb performance is dire, compared to what it should be doing. Simply put: MiG-21bis is a ROCKET. If you zoom-climb from sea level at 1200 kph she should attain 42000 ft/min rate of climb (213 m/s). Best regards, Tango.

I think the EGT behavior is the result of the nozzle. Best regards, Tango.

Hi, Here is a climb, clean, to 10000 m. I only made 9000 m. Best regards, Tango. MiG-21 Climb Clean 10000 m.trk MiG-21 Climb Clean 10000 m.txt

I'm sure they will! I know they're working like crazy. Best regards, Tango.

Hmm... as I thought. Regarding the 6000 m/7000 m observation - above this altitude, performance drops off significantly, and rapidly, above this altitude. Even after triple-checking all switches before departure, passing ~6500 m, the aircraft performance reduced, and I was unable to climb above 7800 m with 2x R-3R and center line 490 L tank. It appears the problem persists. :( Best regards, Tango.

Ahhhhhhhhh!!!!!!! This is why restarting the mission made a difference!! I was changing the load-out in real-time (to add pods etc..)!!! Let me test!!! Does this explain the whole 6000 m/7000 m finding we made last night as well? Related: If the nose cone was NOT moving position, then going supersonic should cause serious engine problems due to the shockwave? I've just become slightly skeptical. Best regards, Tango.

Best advice ever! :D Best regards, Tango.

+1 We are compiling some flight test data now. My previous test is bogus - seems something happened to the mission. Best regards, Tango.

I can only suggest you download it and read it. It's rather informative when you get digging. I think I linked it further up this thread. EDIT: Here it is: http://forums.eagle.ru/showpost.php?p=1470696&postcount=852 Best regards, Tango.

The manual states that climb is conducted at 870 kph TAS, at FULL POWER, which in manual-speak, means MIL, or without reheat. Where reheat is to be used, it either states FULL REHEAT or FULL REHEAT AND SECOND REHEAT (e.g. in the case of zoom climb, for example). It states this quite early on, and either references this condition later on (it will say something like "climbing as per paragraph xyz", otherwise it will state exactly the condition under which the aircraft is to be flown for a particular flight phase or maneuver. The only thing missing is some statement about power settings, but it largely talks about maximum performance, so it is either maximum altitude, maximum range, or maximum speed, so it is either "full power" or "full reheat" that it references most of the time. It does mention expected fuel consumption however (it always states this somewhere), so I guess the % RPM is considered pointless. The only time it talks about other power settings is when it is referring to maintaining a specific airspeed in cruise or descent, but then it is either "adjust power to maintain" or "idle". Given the aircraft and its role, I guess it doesn't need to be more specific than that, anyway. Best regards, Tango.

There is something funky about the reheat, because the aircraft can largely hit altitude/maximum speed as it should, but there is still a problem as the climb performance is still wrong, even in full reheat. Best regards, Tango.

Thanks, but that is not it. Also, the flaps retract due to air pressure upon them. The aircraft has waaaay too much drag (as well?). From the flight manual: 10000 m initial, 8 mins 10 secs descent, 97 L fuel burned, 90 km distance covered. Descent condition: IDLE. Best regards, Tango.

Just did a ENGINE IDLE glide test, and I got: * 8000 m altitude loss * 20 km lateral distance * Vertical speed of ~50 m/s * Maintaining 510 kph IAS * Pitch attitude required: -10 degrees! I need to find a better way to measure the distance (using RSBN at the moment). Best regards, Tango.

My first clean test result is in. CONDITIONS: * Temp: +15 °C * QNH: 1013.2 hPa * Takeoff airport: Krymsk * CLEAN (max internal fuel only) * Hot ramp start * FULL REHEAT until 600 kph * FULL POWER (MIL) level acceleration to 870 kph TAS * Climb to maintain 870 kph TAS Max altitude attained: 7200 m Time: 12 mins 20 sec TAS: 810 kph sustained in level flight Conclusion: the engine doesn't produce enough thrust. Even reaching 1000 kph in level flight at sea level will be hard (which it shouldn't be). The manual states for the above test: * 7000 m * 4 mins 10 secs * 40 km distance travelled Next test is gliding at idle to maintain 510 kph IAS to see if basic airframe drag is too high. Best regards, Tango.

http://www.milavia.net/aircraft/mig-21/mig-21_specs.htm FAS.org is not the best resource for info. I'm checking the manual I have here, too, see if it states a ceiling. EDIT: http://www.airvectors.net/avmig21_1.html (scroll to the very bottom). Fishbed-L and -N are similar. EDIT2: Hmm - this manual is very interesting. Just trying to fly the advised 870 kph TAS full power (MIL) climb schedule is difficult in the sim. I'm 99% convinced that the sim is lacking thrust. EDIT3: http://forums.eagle.ru/showpost.php?p=1470696&postcount=852 "...carrying two missiles and a drop tank the maximum range is reached at 10,000 m...". The manual states this for "full throttle" (MIL) power. Optimum climb profile is: * Takeoff with FULL REHEAT to 600 kph, then * Upon reaching 600 kph FULL THROTTLE (MIL) maintaining 870 kph TAS in climb (or 670 kph TAS if carrying bombs on multi-shackle racks). Manual further states time to climb is 7 minutes clean to 10,000 m, starting with 2750 L of fuel following the above climb schedule. * Tests * Best regards, Tango.

The way I found to fix this is to press the key combinations for the keyboard control of these lights - it seems to fix the issue. Best regards, Tango.

I did wonder. Still... try level flight at "only" 50,000 ft in the sim... :( Best regards, Tango.

http://en.wikipedia.org/wiki/List_of_Mikoyan-Gurevich_MiG-21_variants#Trainer_Variants_.281960.E2.80.931968.2B.29 See also this video: http://www.youtube.com/watch?v=-UpyXxl6qE0 EDIT: With a total disregard for limitations, see the attached. :joystick: Best regards, Tango.

You need to unify the two Y-axis - you currently have two sets of Y-axis gridlines overlaying each other. Need an ability to choose Y-axis data. Looking great! Best regards, Tango.

From everything I read about the MiG-21, what we are seeing would only happen if the SAT was something like ISA+50. The MiG either has insufficient thrust, or too much drag. The real thing (two seat version!) held sustained level flight at 62,400 ft. I can't even climb up there. It seems to be an issue that gets worse with altitude. It seems the aircraft is fairly close to real-world up to 5000 m (16404 ft), but above this the sim performance drops significantly compared to what it can do IRL (and IMHO even at 5000 m the performance is already lower). Based on my observations with a clean jet, it appears that it lacks thrust, and the thrust vs. altitude reduces more rapidly than reality. Idle descent requires a vertical speed of ~25 m/s, and engine off requires ~50 m/s, which is what the manuals state. It would however require a much more careful analysis of glide performance before making any comment. Example: the manual states an idle descent from 11000 m at 510 kph IAS will yield a glide distance of 90 km, requiring ~25 m/s RoD. Best regards, Tango.

Hi, These screenshots were taken with a clean jet. 8300 m = 27230 ft. Best regards, Tango. MiG21.zip

Hi, I'm sure I saw this in a screenshot - how do you set/remove the nose cone cover and wheel chocks? Best regards, Tango.

I haven't seen charts for max rate/min radius turns, or discussion of "max corner airspeed". Maybe there is another term used? Best regards, Tango.