Pilum

Excellent news. Thanks for the info Kuky!

Also: When you say "fixed" does that mean missile kinematics only or does that include guidance as well? I mean, I would be happy if they started with the kinematics because that would go a long way but to also get guidance improvements would be awesome! :beer:

Allright! Now that sounds promising! :thumbup: BTW: Anybody know if this is limited to the Leatherneck missiles or can we look forward also to fixes for the other missiles like AIM-120 and the R-27-series etc?

Noticed that the thread has been tagged [FIXED INTERNAL] now so I figured this issue had been addressed but this does not seem to be the case: I still get around 4300 km/h missile top speed from a +800 km/h launch at 6 km altitude so it's still too high and the missile still behaves as if it has the speed-brakes deployed after motor burnout. FIXED sounds like past tense to me but does [FIXED INTERNAL] mean problem acknowledged and fix is under way? OTOH there is also the [FIX UNDERWAY] classification so I'm just trying to make sense of what does [FIXED INTERNAL] mean and what are the plans?

Ok Yo-Yo good to hear that you found the source to the high climb rates. Such an adjustment of the power would be welcome and could very well be an explanation for what we are seeing. I would gladly share my simulation results and also the methodology behind them with you but I would prefer to do that via PM and mail if that is OK with you? :smilewink:

I agree completely with what Solty, Grapejam and Kwiatek have been saying: All logic and evidence combined points to that the the Focke-Wulf chart showing 22 m/s climb at 1.8 ata for the Dora is with exhaust thrust included. Attached is also a C++ simulation showing that a correctly modeled Dora will fulfil both the Steig&Kampfleistung flight measurements and the Kennblatt and the calculated 1.8 ata chart by Focke-Wulf: As can be seen in the figure there is no contradiction at all between the flight tests and the calculated values by Focke-Wulf when looking at the delta between Steig&Kampfleistung and 1.8 ata and that it would be wrong to add the exhaust thrust resulting in a climb rate of 28 m/s since this is already included. In addition, if the reason for the 6 m/s climb difference between DCS and the Focke-Wulf chart was that exhaust thrust was not included in the Focke-Wulf calculations and that when this is added we get the 28 m/s we see in DCS where does that leave the DCS Me1094? Since the DCS K4 is climbing 30 m/s at 1.8 ata does that mean that the climb charts calculated by Messerschmitt showing around 24 m/s are also without exhaust thrust? So in order for all this to make sense we have to assume that both Focke-Wulf and Messerschmitt left exhaust thrust out of their estimates? I find this quite unlikely and more plausible explanation being that the climb figures of 28 and 30 m/s for the Dora and K4 in DCS are just too optimistic. Fw190D9climbexhausttcomp.bmp

Yeah that would be nice! Trouble with glider sims is you miss the seat of the pants "push" to center in thermals no? How ever would you model that? :smilewink:

Glad you found the posts on exhaust thrust interesting Jcomm! And yes, as the figures show it affects the performance a lot so it is certainly important to have it accounted for when estimating performance :smilewink: Speaking of that, I am now really looking forward to the release of the Spitfire in DCS to see how exhaust thrust will be added there. Having both studied historical data and flown a number of different flight sims over the years one has become accustomed both to certain absolute levels of performance and also certain performance relationships between different aircraft (e.g. climb) so it will in this context be very interesting to see how the Spitfire is modeled and performs in DCS I think.

The effects of exhaust thrust on Dora performance Propeller driven aircraft in WW2 such as the Fw-190D9 that did not have an exhaust driven turbocharger like the P-47 but instead used a compressor to attain higher than atmospheric boost pressures as a rule had carefully designed and tuned exhaust stubs. The reason for this is that there is a substantial amount of thrust to be gained by directing the exhaust gases from the engine to the rear thereby adding this to the thrust of the propeller. Taking the Junkers Jumo 213A that powered the Fw-190D9 we have modeled in DCS as an example, how much exhaust thrust did this engine produce? Well if we assume a high boost scenario with the engine producing around 2100 hp, the exhaust thrust would be in the order of 1400 N which is quite significant. This exhaust thrust is especially welcome and significant at high speeds since it is close to speed independent, i.e. the 1400 N in exhaust thrust the Jumo 213A engine produced at standstill is present also at high speed. This becomes especially important to increase top speed performance since the propeller engine thrust is inversely proportional to speed, i.e. Tp= (n x P)/v, where n=propeller efficiency, P=Engine power and v=TAS. Applying this to derive a C++ calculated top speed for the Dora including exhaust thrust under these conditions the top speed is circa 615 Km/h with, while the top speed without exhaust thrust is around 580 Km/h. So, when looking at historical data it will be quite obvious if exhaust thrust is included or not since the speed difference is so substantial. However, the exhaust thrust also has a significant impact on climb performance as the attached simulation figure shows. The solid blue line shows the climb rate with exhaust thrust and the dashed line without exhaust thrust. As can be seen, the sea level climb rate with exhaust thrust is around 22.6 m/s while without exhaust thrust accounted for it is reduced by 2.8 m/s to circa 19.8 m/s. Consequently, since exhaust thrust is such an important contributor to the overall performance of a WW2 type compressor driven aircraft in both top speed and climb, these effects are absolutely necessary to include in any meaningful performance estimate and which is also why all performance estimates I have ever seen have always included this effect.

You keep saying that your calculations agree with what Yo-Yo is saying Crumpp but how can you be so certain of that? Do you agree Yo-Yo? Do you really think that a sea level climb rate of 28 m/s for the Dora at 1.8 ata is reasonable and what we should expect to see in DCS?

Ok you have a lot of "if's" there. Does that mean that in your opinion the reason for the difference between DCS and the Focke-Wulf data is due the compound effect of a low estimate by Junkers coupled with a low estimate by Focke-Wulf and no exhaust thrust added which leads to the 6 m/s difference in climb speed? Why ever would they publish such a chart and make no mention whatsoever of these assumptions? But if not 6 m/s then how large is this "significant improvement"? Your SWAG was 28 m/s and Focke-Wulf's is 22 m/s so the difference there is 6 m/s. If it's not 6 m/s then what what is the actual climb rate of the Dora at 1.8 ata, i.e. the one we should expect to see in DCS without conservative estimates by Junkers and Focke-Wulf and WITH exhaust thrust included?

So are you saying that you would estimate that adding exhaust thrust would add 6 m/s? i.e. lift the Focke-Wulf figure of 22 to 28 m/s in climb?

Well the Focke-Wulf estimated climb rate is around 22 m/s for 1.8 ata as far as I can tell. If it goes up to 28 m/s (or do you have another estimate?) if exhaust thrust is added, why on earth would Focke-Wulf publish a chart showing 22 m/s climb rate without this included when it would go up to 28 m/s with exhaust thrust accounted for?

Yo-Yo: So are you saying that the Focke-Wulf figures are without exhaust thrust?

Sorry can't do that since it is in the C++ code in a number of different function that are called upon to estimate prop and exhaust thrust, parasite and induced drag all as functions of altitude, mach etc. Basically I numerically iterate different climb angles and speeds until I find the optimum.

Yes, I do have issues with your calculations since these show climb rates that are way higher than those calculated by Focke-Wulf. And no, the burden is not on me but on you, since I rely on numbers calculated by Abteilung Flugmechanik-L at Focke-Wulf and you rely on calculations that are by your own admission SWAG's.

I agree and that is a good point. In fact it looks like both the Dora and K4 have too high climb rate right now in DCS: A thread was started on the K4 which showed an initial climb rate of 6100 fpm or circa 31 m/s. http://forums.eagle.ru/showthread.php?t=137503 However, the difference is that the K4's excessive climb rate thread has been closed and confirmed to be a bug: http://forums.eagle.ru/showpost.php?p=2292272&postcount=85

ROTFL :megalol:

Crumpp, you must have missed the "Focke-Wulf" when I asked. I think we are all pretty clear on what your calculation method yields. However, we are interested in manufacturer calculations or flight test data for 1.8 ata OK?

Yep, that looks quite familiar don't it :) And about the racks: Those would make an impact on top speed but in climb rate the difference would be really small. Will be interesting to see if we will see some calculations or flight test data by Focke-Wulf to back up Crumpp's 28 m/s climb SWAG but I would not hold my breath! :music_whistling:

So summing up the posts up till now the motivation for the high 1.8 ata Notleistung climb rate we find in DCS is Yo-Yo pointing out that there can be 10% variations between flight tests and calculated figures and in support of this is referencing some figures for 1.45 ata Steig & Kampffleistung? In addition, Crummp has chimed in to explain that a variation in climb rate of 20% from manufacturers published calculated data is not uncommon? Is that it? So is it a high end Dora we have in DCS that is 10-20% better than Focke-Wulf published figures? What are the implications for other planes modeled in DCS? Will we see other planes that deviate 10-20% from manufacturers published figures or is this limited to the Dora only and if so based on what data? In addition, for some strange reason, my C++ calculation estimate of 10 min to 9 km for 1.8 ata (attached below) seems to tab up pretty well with the Focke-Wulf estimate of 9.19 min for 2.02 ata which makes more sense as compared to the 7.75 min result in DCS IMHO. However, that could of course be due to that Abteilung Flugmechanik-L and me, unlike Crumpp, don't understand the maths and physics involved here. Finaly: USARStarkey, I must say I really admire your stamina and patience in all this! :notworthy:

I just tried out the DCS Dora climb time from sea level to 9000 m at 1.8 ata in the latest release 1.2.15 and it still seems to be the same climb time, i.e. 7 min 45 s. This can be compared to the IRL data of 9.19 min for 2.02 ata (See 7th row in first table below): This is also in good agreement with an alternative method estimate of 9.2 min based on eyeballing the average climb time from the attached chart which AFAIK is for Sondernotleistung 2.02 ata. Both these figures indicate that the DCS Dora climb rate at 1.8 ata is higher than the IRL data for 2.02 ata. So based on the above, I think it is proven that the Dora climb rate in DCS at 1.8 ata is currently way to high in comparison to historical data and it therefore seems appropriate to move this thread to the bug section.

But the trouble right now in DCS is that the trim range does NOT cover the whole speed range: At top speed you need to apply a bit of down elevator to stay level. If you let go of the stick the K4 climbs. Again, if you don't want to add a trim tab option for the elevator then how about adding a constant to the elevator hinge moment to offset the adjustable tailplane trim range to a more nose heavy range? Again, this would be "historically" correct since any pilot could do this. Why on earth would a pilot fly around in an airplane that you could not trim to level flight at high speed when all he needed to do was get the trim tab on the elevator slightly adjusted?

OK, maybe painting up hypothetical scenarios with "naysayers" and "those people" in reference to the Spitfire is better classified as being made in poor taste rather than dissing. Sounds good!

Sure, we don't need to introduce a secondary source for trim in pitch: However, what a change in the elevator trim tab setting would accomplish is a translation of the trim range of the adjustable tailplane to encompass a larger nose down range meaning you could actually trim out the K4 also for high speeds. How large this translation should be would be determined by how much up bend you would apply to the trim tab and the point here was that if this was configurable in DCS (prior to take off) then we could all set this to our own individual taste just as it would be nice to do this also for rudder and aileron. Again, all this would be historically correct since this is what you IRL can do as well: The tabs allow you to within reasonable limits set at which speed and power setting your plane trims out in yaw, roll and pitch. However, if having all this configurable in DCS is off the table then just adding a constant value to offset the current K4 adjustable tailplane trim range in pitch towards a more nose heavy range that would also be OK IMHO.