Pilum

Yup, this seems way too optimistic: My C++ simulation yields 8 minutes 10 seconds for a climb from 500 m to 9000 m for the Me109 K4 with B4 & MW50 at 1.8 ata. So it seems that the climb time to this altitude is only about 74% of the time it really should take.

Well, nice to hear that there seems to be others who would like to see the Draken in DCS! :thumbup: I wonder if the DCS AFM is advanced enough to allow a true representation of the Cobra? IRL there is a complicated pattern of separtad potential and vortex lift on a delta at such aoa that requires a lot of processing to emulate. However, I do believe you can do the Cobra in the DCS Su-27? If so is it ”truly” modeled or scripted in into the FM? Anybody know this? Another thing with deltas (at least the Draken) is the superstall phenomena and this would also require some serious processing so I wonder if that is within the capabilities of the DCS AFM? Too bad the Draken video I posted above is to grainy to see the control input the students are using to initiate and get out of the Cobra before getting stuck in a superstall….. On the subject of superstall, here is a short anecdote of what can happen IRL: A friend of mine flew at the F21 wing in Luleå and did an involuntary IRL superstall in a J-35 J “Johan” in the early 80’: They were training ACM and in a head to head pass at 6 Km he craned his head back to keep the other guy in sight and pulled a bit too hard and forgot to keep tabs on alfa. Result? Next thing he knew he was at a stable high aoa doing mild pendular motions in pitch with the altimeter spinning wildly. Luckily he was trained to handle this situation and knew that simply pushing the stick forward would get him nowhere so he immediately started to use the stick to increase the pendular motions by timing the input to coincide with the frequency of the oscillations and IIRC he was as low as 1-2 Km and close to punching out when he finally got out and could recover.......

Well, sorry but adding an F-5 would be just another hamburger to me and frankly I don't think the F-5 is such a hot ship so I doubt I would buy it. Also, I don't really see a good solution for the F-4: What should the RIO solution look like? A MP solution meaning always two people needed or an AI RIO? In the latter case how good should the RIO be? Problem with doing the J-35 Draken is I guess many people can't relate to it. Even if Swedes, Danes, Finns and Austrians were to buy it how big a market is that? Or maybe I'm wrong and there are more people who would like to see it? Anyway, I do think it would be nice with something different like a delta-winged Mirage or Draken though. Maybe one should have a poll? Mirage, Draken, F-4 or F-5? Concerning other aircraft like the Su-22, Mig-23 etc, sure that would be nice as well but right now what I would like to see and gladly pay for is a suitable (and as well made) adversary to the Mig-21bis. The Draken would be nice for me: I'm currently struggling with the Cyrillic text in the Mig but I would of course be quite comfortable with the Swedish text in the Draken cockpit :music_whistling: One that still flies: If you don't have the patience to check out the whole vid, see from around 3 min in and then check out the high alfa landing at the end :thumbup: And last but not least: If you get a pesky Mig on your tail you can always do the Cobra, a Swedish manouver later deviously copied by the Soviets in the Su-27 ;) (Demonstrated about 1:50 s to 2:30 into the clip)

Well since I'm a Swede I have to agree with you: Köttbullar & makaroner is good stuff and the Draken is the best looking aircraft ever ! :v:

I was thinking more like the Mirage III or similar. Setting a Mig-21bis against a M2K seems a bit harsh..... Kotleta, Da?

I recently procured the Mig-21 and first of all let me say I'm very impressed both in terms of the visuals, avionics and also the FM as far as I have been able to tell so far. So my hat is off to the Leatherneck team for a job extremely well done! However, I noticed that many are voting for an F-4 Phantom or another Russian design like Mig-23 or Su-22 as the next addition and while I would like to see those as well I would personally prefer a delta in the Mirage series as the next addition. Why? Well first of all it's a contemporary design that is a good match in terms of dogfighting the Mig-21 which it also did IRL. It was also built in a number of different version that could be modeled meaning one that would be a good match-up both in terms of flight performance and armament could be modeled and while we all want historical accuracy, it does not hurt to model something that would make dogfighting interesting and not skewed in either direction. It is also a single seater (no RIO needed like in F-4) and being a delta it would give us a very different aircraft to fly than yet another conventional wing-tail design. Deltas have their own quirks and are different aerodynamically and given the DCS AFM it would be fun to master flying a delta winged Mirage as well. It is not yet another US or Russian jet but being a French design it would also give us a refreshingly new cockpit environment to get familiarized in. French technical solutions both in terms of aircraft aerodynamics and engine, layout of cockpit and french labels on the switches would add some spice to the fare we currently have. So please give us some French cuisine before adding more hamburgers or kotleta to the menu. :yes: Vive le Mirage III!

Sorry Crumpp but you lost me there: What is the theory we should present to the developers? That you are prone to talking about hood ornaments and flat tires when pressured? That you don't have a report that shows that the Spitfire Mk9 is unstable or that you don't have an answer to post #59? Could you clarify this please?

I'm new to helicopter simulation and I really love the Huey. However, I have no IRL heli experience so I was wondering if there are opinions from those of you who fly both the DCS Huey and a real heli on the FM when it comes to longitudial stability. I have to some extent mastered hovering and after that I decided to try out the armament but I find the Huey very prone to longitudial pendulum motion in pitch when trying to settle the sights. How does the DCS FM and IRL compare on this point? Is this what you would expect IRL as well? I'm refering to a flight mode where the heli has a good forward speed and is not hovering.

Yes, Bongodriver, I agree completely, but this simple fact seems to have escaped Crummp who now seems more focused on hood ornaments and flat tires. Anyway, it seems we need to cut Crumpp some slack so he can sort out his South American FOD problem and find some precious time to find those reports showing the alleged Spitfire Mk9 instability. I would not hold my breath though......

Again you are implying that you have a better background than the rest of us to understand stability and control and again you yourself bring up the subject of academic background and GPA grades. So to put your statement above into perspective why don't you simply answer the questions in post #59?: http://forums.eagle.ru/showpost.php?p=2278425&postcount=59 After all, you yourself brought this subject up so why not finish what you started? Why are you avoiding the question?

More Spitfire MkIX ballast info from Morgan and Schacklady: Page 334 shows a loading plan and here table 2 details two ballast weights in tail: One standard at 17.5 lb and one additional one at 5 lb. However, even though the table is in the Mk IX chapter of the book, there is also a figure of a MkXVI on same page so it's not totally clear that the loading plan is for the MkIX. So seeing ballast is added in tail, this would point to the aircraft being stable since adding ballast otherwize makes no sense. This table also details the moment of arm which is 175 inches. So maybe AB197 did not have 5 x 17.5 lb weight in tail after all but flew with 5 lb with a moment arm of 175 inches and this was interpreted as 5 x 17.5 lb.... Anyway, irrespective of if it was 5 lb or more ballast: You don't add weight in the tail of an already unstable aircraft .......

IIRC then the later Spitfires (like the late Me109's) had ballast added in the tail to compensate for the increased engine installation weights in the later marks. When did this start to be incorporated? Was it already in the Mk9's or was it with the later Griffon variants? It would be reasonable to assume that no more ballast was added than necessary since any added weight to an airplane by definition is bad unless it serves a purpose, in this case to reduce excessive tail loading caused by nose heavyness. So on the Spitfire marks where ballast was added, it stands to reason that no more was added than needed, i.e. the airplane would have been on the stable side since adding more ballast than that would move the airplane towards instability which makes no sense really. Addendum: From Morgan & Schacklady page 323: Weight and loading Spitfire Mk IX AB197: "Tare (includes 5 x 17.5 lb ballast weights in tail) .....". Don't know if that was just AB197 or if other MkIX flew with ballast. Anyway, adding ballast in the tail would not be something you would want to do in an unstable aircraft.......

Crumpp: It is really interesting to hear about your Msc.in aeronautics: I think you mentioned this before as well but IIRC without many details but I'm sure there are many of us here in this forum who would like to know more so it would be great if you could share some of your work experience with us: When did you graduate and what fields did you specialize in? What did you do as masters thesis? How many years have you been in the aviation industry? What aeronautical companies have you worked for and on which projects/aircraft? I'm especially interested since it seems we are colleagues: I got my MSc. in 1986 from the Royal Institute of Technology in Stockholm, Sweden. I specialized in aerodynamics, flight mechanics and structural engineering. My masters thesis was a computer program for predicting the impact on flight performance of external stores on fighter aircraft. It is a derivate of this program I now use to predict WW2 aircraft performance and sometimes post results from here. I have left the industry now but before that I worked for more than ten years at various companies owned by SAAB and Ericsson such as Ericsson SAAB avionics, Ericsson Microwave systems etc. I have worked mainly with countermeasures systems, both tactical and training systems for the JA37 Viggen and JAS39 Gripen fighters. I know you like to tell us and share freely about your experiences as a private pilot in these forums and now that you brought up the subject of education and work experience yourself it would be great if you could share that with us as well. I'm really looking forward to hearing this Crumpp because you have a high profile in these forums and it would therefore be really interesting to know what similar lasting contributions you have made in the aeronautical industry.

Yes, this thread has really been a fascinating lecture and I have thoroughly enjoyed reading it and learning so many new things! For example, I always thought that the British Royal Aeronautical Establishment knew what they were doing but based on new insights gleaned in this thread it now seems I need to revise that opinion. On the subject of lectures, I noticed that the entertaining series on turn performance and correct usage of Equivalent Air Speed (EAS) have been halted for some reason. I wonder why? No matter, this forum will no doubt also next year be blessed with new insights and interesting lectures on the subject of aerodynamics and flight mechanics and it's all for free as well! Happy New Year! :holiday:

Exactly, so maybe we can return to the topic?: P47 versus Spitfire turn performance? Would be a shame if this thread derailed before we concluded that discussion.

Crumpp, even though you have not responded to the question of what altitude the charts in post #1 are for, now that you posted your estimate for 30,000 ft, it can actually be reverse engineered based on that data: For comparison, these are my C++ simulation results: Spitfire Mk9 +18 boost at sea level: 290 KEAS, 20,000 ft: 258 KEAS and at 30,000 ft : 213 KEAS P-47D-10 with D-22 prop at sea level : 290 KEAS, 20,000 ft : 263 KEAS and at 30,000 ft : 239 KEAS Comparing the turn rate chart in post #11 which states 30,000ft, this gives the Spitfire maximum KEAS speed at circa 215 KEAS and the P-47 speed at circa 240 KEAS. i.e. in good agreement with my simulation numbers for 30,000 ft. Based on this it is obvious that your charts in post #1 are not sea level but for 20,000 ft since the zero turn rate speed in your charts tally with my 20,000 ft results. So to conclude: Mine and JtD’s TAS based estimate for the P-47D-22 max sustained load factor at 20,000 ft is around 2.1 at 175 KEAS while your’s using your EAS method can be read off at 3.5 in your chart. In addition, JtD posted an estimate of a max sustained loadfactor of 1.8 at 30,000 ft in post #14 which tabs well with my C++ simulation result of 1.77 which in turn can be compared with your 2.4 g estimate. In addition, your charts in post #1 indicate that the P-47 will outturn the Spitfire at 175 KEAS at 20,000 ft which also seems wrong and is the opposite of what my C++ simulations show. So it seems there is a fundamental flaw somewhere in the way you use EAS to estimate turn performance Crumpp.

Ok Crumpp, so now we have your chart for 30,000 ft but you still have not answered the question about the charts in post #1. Are they for sea level or 20,000 ft?

Well I checked my assumptions in the C++ simulation code and it turns out I had the paddle prop modeled for the D10 already: The reason was I was using P-47D-10 trial data from WW2Aircraftperformance.org where they tested both toothpick and paddle blades on the D-10 model and I tuned the model after the paddle prop so my "D-10" estimate should be quite comparable to the D-22 unless there are other big differences that I'm unaware of? Yes, I agree. I think the different approach in EAS/TAS usage may well be the key here as you say. While EAS can be used as well, the conversions between different altitudes requires careful handling of the density factor sigma if you are using EAS since this otherwize can lead to strange results. Anyway, If Crumpp simply answers the three questions I have asked him in post #4 I'm sure we will find out why the figures attached in post #1 shows the Thunderbolt outturning the Spitfire at 175 KEAS (aircraft variants and conditions as defined by himself).

Yes, there were as you say many versions of the P-47D. The same goes for the Spitfire Mk9. However, in this case if you look at the attached figures it is well defined: P-47D-22 at 56" boost and Merlin 66 Spitfire Mk9 at +18 boost.

OK, that's great because it is difficult to understand how you use EAS Crumpp so it would be good if you explained how it should be used. First of all I thought the P-47 engine produced 2300 hp at 56" boost? You now mention 2800 hp? And secondly, I understand that different Spitfire and P-47 variants behave differently but the question here was the P-47D at 56" boost relative the Spitfire Mk9 at +18 boost right? And thirdly, concerning the altitude, I'm not sure I understand? Are the KEAS turn rate figures you posted for sea level, 20,000 or 30,000 ft?

Since we will soon have both the P-47D and the Spitfire Mk9 in DCS and there has recently been a discussion about different methods doing turn estimates based on EAS or TAS, I did an estimate using TAS and got the following results: Spitfire Mk9 Merlin 66 at +18 boost, maximum sustained loadfactor at 175 KEAS, n= 3.52 sea level, n=2.77 at 20000 ft. Thunderbolt P-47D-10 56” boost, maximum sustained loadfactor at 175 KEAS, n= 2.54 sea level, n=2.08 at 20000 ft However, as indicated in a couple of figures you posted earlier Crumpp, it looks like your EAS method yields very different results: Compare both at 175 KEAS for example, here it looks like the P-47D with n=3.5 will outturn the Spitfire Mk9 with n=3.2? Again, altitude is not given in the figures and you were referring to results for 20000 ft in your post but maybe the figures refer to sea level after all? Is this the performance you expect to see in DCS then Crumpp? The 56” P-47D having better sustained turn performance than the Spitfire Mk9 +18 boost at 175 KEAS ?

Nope, EAS works fine as long as you use it correctly. However, in the figure you posted for the Fw190A8 in post #63 one can read off 3.2 g’s at 165 knots EAS. At sea level this equates to a turn time of 17 s and such a sea level turn rate would be more reminicent of a Spitfire and certainly nothing a Fw190A8 would be capable of.

The sustained load rate figures you posted in post #63 seem very optimistic Crumpp: At what altitude are you assuming the Fw190A8 can sustain 3.2 g’s at 165 knots EAS?

Well pilot's are cautioned not to roll while pulling heavy g-load because this is known to be dangerous. If fact structural engineers refer to this as the rolling pullout load case and it is usually not a dimensioning load case for the airplane meaning you should not expect to be able to pull the same g-load in this case. Usually you have a dimensioning loadcase that you need to show the contractor that is 1.5 times the max permissible. However, usually the pass criteria is that it should not break at this point and usually the contracting authority will allow that the aircraft can redistribute loads through plastic deformation meaning you could pop rivets and wrinkle skin at this point which however will not go down well with your crew chief when you land :music_whistling: I would guess that the Me109K4 had in the order of 6-8 g max permissible at a certain weight and that the wings should consequently come off at around 9-12 g. However, since it's embarrasing to fail the load test in front of the contractor (usually a hydraulics or sandbags test), engineers will have a small "own" safety margin on top of the 1.5 so you should be able to pull a bit more than 1.5 x max permissible but in this region while you may be able to get the plane home but it will probably have to be written off and that will be difficult to simulate in DCS so having the wings come off in combat seems like a better idea. So why not go for something like wings come off at 1.25 x max permissible load factor for symmetric load case as a compromize since allowing the full 1.5 seems too generous given that this basically ruins the aircraft IRL.

Correction: Now with the latest patch it seems like the Dora is back to what is was before (or close to) and that the K4 rudder authority has been similarly adjusted to be less responsive :(