Pilum

Mattebubben: I know you only posted the chart and did not defend or vouch for it so no worries there. :) I just think there is something strange with it. Maybe someone mixed up instantaneous with sustained numbers I don't know but at least the M-2000/Viggen comparison does not make sense IMHO. I don't think Tharos who AFAIK first posted the chart ever replied to the question where it came from and it would be interesting to learn the history behind it. However, noticed you say the Viggen has a better sustained turn rate than I think so I would appreciate to know what that means? So what does the Viggen do? I have not done any calculations myself or seen any charts so I would be interested to hear how you came to that conclusion. Maybe we are using different terminology here because you say bleeding energy while doing those manouvers which I don't associate with sustained performance. However, if you are talking about instantaneous turn rate the I agree that the Viggen is no slouch as you put it. Finally, charts of both would be nice but based on the four points I made previously I think anyone who thinks they will show similar sustained turn performance will most likely be sorely disappointed. Actually, I think if you look a doghouse turn charts for jet fighters you will see that M=0.9 is a pretty good speed for sustained manouvering. IIRC then there is a nice M-2000 doghouse chart somewhere in the RAZBAM part of the forum.

I don’t want to rain on the parade but if Leatherneck are going to deliver a true rendition of the AJS Viggen then those who intend to use that chart for planning how to deal with the other aircraft in the table are most likely going to be very disappointed: The Viggen is NOT a good sustained turning fighter (Instantaneous yes, sustained no) and that it should have as good a sustained turning capability as the M-2000 defies logic: 1) Both planes have about the same span loading, i.e. wingspan/weight 2) The M-2000 has a somewhat lower wing loading 3) The M-2000 has a much higher thrust to weight ratio 4) The Viggen is a very, very stable aircraft and a lot of the weight is carried by the carnard. The M-2000 OTOH has fly by wire relaxed stability which significantly reduces trim drag in turns. Now all these things taken together with the laws of aerodynamics and flight mechanics suggest that the M-2000 should make very short work of the Viggen in a sustained turn fight and makes me very suspicious as to the veracity of the table…….

I also got my extension a few days ago. I choose the standard 10 cm version. Machining was good with nice finish and threads fit in nice with those on the stick. A nice touch was that the cable is slightly longer than needed meaning you get a natural pressure on the Warhog connectors so there is no risk of loosing the electrical connection. So I'm very satisfied with my purchase.

Here is a chart showing the effects of weight on the Spitfire Mk9 speed as a function of altitude. As Yo-Yo already pointed out, weight does of course factor in at higher altitudes since the induced drag becomes more and more important at higher altitudes and weight is of course not unimportant and it is a big factor in determining the aircraft's ceiling and acceleration but that is another matter entirely. However, as can be seen in the figure, for the Spitfire Mk9 with its relatively low wing loading the effects of a 5% difference in weight on maximum speed up to and including FTH are negligible. Finally, as Otto pointed out earlier, there is no easy way for you to verify the accuracy of my simulations since you only see results. However, I have posted in various sim forums over the years and I think you can verify the accuracy of the C++ model in the same way you would verify a flight simulator: Compare the sim data with IRL data and see to what extent they agree. IMHO I think what I have posted so far over the years tabs pretty well with IRL median values but then again I can’t be considered impartial can I so you just need to form your own opinion. :smilewink:

I think Yo-Yo is quite correct about the significance of a 5% weight change: My C++ simulation estimate of the difference in speed for a 5 % weight change at FTH for the Spitfire Mk9 is 1.41 Km/h or an astounding 0.2%. Getting late now and busy on Wednesday but will post "flea" figure on Thursday if needed. :smilewink:

Since it was some time ago I modelled the Spitfire Mk9 in my C++ simulation code I reviewed it and revised my figures at bit (circa 5 mph lower speed and circa 700 ft less critical altitude than the earlier estimate in post #73) but the latest estimate in the figure below still seems to tab pretty well with the DCS Mk 9 model. Concerning the accuracy of the results I can only say that I have over the course of more than 10 years modelled circa 20 different aircraft in my C++ simulation and the nice thing once you have a good model is that usually the numbers tab pretty well with the IRL median values. The funny thing is that on a technological level both Allied and Axis planes seem to be close in performance and once you have the basic data like power, weight, wing area, wing span, prop diameter, prop rpm, tip speeds etc. it turns out that there are not that big differences in key performance parameters such as propeller efficiency, ram recovery etc. This is why I trust the 21,000 ft critical altitude figure I get from my simulations for the Merlin 66 powered Spitfire Mk9 because this is what you would expect to see from a decently designed ram intake and I can see no reason why the Brits should botch this up? In addition, the air intake pictures presented above look reassuring since they incorporate boundary layer separation so the pressure recovery should be in line with a state of the art intake from that time. Anyway, when I plug in the power/altitude characteristics of the Merlin 66 into my code I get a full throttle critical altitude of 21,000 ft and a top speed of 410 mph which looks pretty close both to the DCS values and what looks like the IRL median figures as well. Of course there are always the outliers or tail end data as Yo-Yo calls them but why on earth would you want to bring those to the table since they by definition are unrepresentative? That’s a rhetorical question by the way so I’m not expecting an answer…….:music_whistling:

I don’t have time for anything more than a quick post today but I want to get in that I think the speed and ram boosted FTH in the figures Yo-Yo posted look all right to me: Did some quick C++ simulations runs with the Merlin 66 at +18 boost at 15 deg C for a production model Spitfire Mk9 and got the following numbers: Max speed SL: 538 Km/h or 334 mph Max speed at ram boosted FTH: 668 km/h at 6.6 Km altitude or 415 mph at 21700 ft altitude So to me it looks like the DCS Mk9 model is pretty close to what one could expect! :thumbup:

Was not planning to post at all here since I can't see that you or Crumpp have "proved" anything but seeing the two quotes above changed my mind. If we find a little red cross by your name it won’t be because you have been martyred and silenced. It will be because you continuously bring up the same subject again and again and even hint that other who have “complained” have been banned, i.e. silenced by the DCS moderators. To crown it all, you even suggest that the DCS developers have “balanced” the sim, i.e. premeditatedly doctored the performance. Both pretty serious allegation so I would not be surprised if you end up in ban-land. You make your own bed so don’t be surprised if you get to lie in it…… Also can’t see why you bemoan Crummp’s fate: That he is still banned is IMHO well deserved since he has been badmouthing DCS products over at the Il-2 Battle of Stalingrad forum and even put up his DCS P-51 key for sale there so I'm not loosing any sleep over that either.

First a comment to Hummingbirds theory that the K4 should go faster because calculations are always conservative. Having worked with military aircraft systems (In engineering, management and marketing) for more than 10 years I can tell you that these theories are just plain wrong: Calculated performance figures are not always conservative. They can just as often be very optimistic: While engineering estimates may be conservative, the company management and marketing departments have a tendency to want to see optimistic figures. Why? Well it is because systems are bought on a price/performance basis. Now the procurement agencies know this so they enter penalty clauses into contract so companies are not tempted to promise too much. However sometimes company management will rationalize and be willing to take the risk of penalties just to take the contract. So any calculated figure you see may or may not have received TLC by the company management and/or marketing department. Which means that any calculated figure you see may deviate in any direction. You have no way of knowing this unless you have access to the raw calculations behind the curve, the by now famous K4 speed curve included. Sorry but there it is. In addition, if you have data from flight tests these may or may not be representative: In order to find that out you ideally need to have a lot of different test results and filter out the outliers that are due to measurement errors or other deviations. Unfortunately, on top of all these innocent sources of errors there is a more sinister aspect which needs to be taken into account: The internet being the place it is harbours some individuals who attempt to skew the picture by deliberately manipulating the data. Note that this need not involve actual falsification of data but can be achieved more subtly by simply only making only the very best data available and filtering the rest. So to avoid all these pitfalls you need data from as many sources you can find. In addition, taking the K4 as an example, you don’t necessarily need K4 data at 1.8 ata to determine 1.8 ata performance with a good degree of accuracy: If you have for example data at Steig & Kampf Leistung you can use this to reverse engineer drag and then make a good prediction with another engine or power output. Now from what Yo-Yo has said in this thread my understanding is that he has based the top speed value he is targeting for the K4 based on input from multiple sources and I use the same approach myself in my C++ modelling: collect a lot of data, input into model, run the simulations, tune the model, check the fit to known data points until you have the best fit to the data you have. For me this resulted in a K4 top speed of 587 Km/h at 1.8 ata and to my understanding this is in the ballpark of what we should expect to see when the mod is implemented. AFAIK Yo-Yo has acknowledged that the data you have presented has been taken into account and the top speed value chosen seems to be based on multiple sources including your input so I don’t see how the way some of you keep regurgitating the same K4 speed chart, wheel door and tailwheel values over and over will help? Maybe it’s time to close the thread? :music_whistling:

Definitely. Also nice to see that things worked out well in the end and a good judgement call by the developers IMHO. :thumbup:

OK, thanks for the info and that certainly sounds plausible. I get 587 km/h at sea level in my C++ simulations but I think I may be a bit on the optimistic side. :)

Well that sounds a lot like the royal "we" and I'm sure they have the fullest of confidence for you seeing your penchant for high end Me-109 performance outliers. :music_whistling: Great, so you agree that the figures are with exhaust thrust or are you simply playing at semantics? OK, so it was semantics: you do think exhaust thrust is missing after all. I do hope that Yo-Yo clears this up because AFAIK that exhaust thrust is missing is an interpretation you and Crumpp have been eagerly peddling for a while now and I don't think he has ever said that. OK, good that a fix is underway. Let's see what that brings shall we?

Just noticed some other things that have been sneaked into the K4 storytelling: First of all that it is “obvious” that exhaust thrust is missing from climb figure and that the kennblatt speed figures are “most likely without“ wheel doors and retractable tail wheel. “Obvious and most likely” based on what? Other than wishful thinking?

Well Adam, as to who is trying what and who has an agenda I think I'll leave that to the developers to decide. That you and Hummingbird are pushing the idea that exhaust thrust is not included is just silly and I wish you good luck trying in to convince Yo-Yo et al to boost the DCS K4 speed another 10-20 Km/h due to "missing exhaust thrust". :megalol:

Exhaust thrust not included? What absolute nonsense. Of course exhaust thrust is factored into any performance figure since publishing any performance figure without it would be meaningless since it has such a large impact on performance. If you want a reliable base figure for the Me-109K4 top speed at 1.8 ata then look at the Kennblatt: This gives 580 Km/h. Suggesting that this is missing 20 Km/h and should in fact be 600 Km/h when exhaust thrust is factored in is simply laughable.

Thanks for the (formerly) secret parts of the SFI! I really enjoyed reading it, especially the parts about the countermeasures and how the pilots operated these and their tactical use. I worked for more than 10 years in the Swedish defence industry with some of these systems and I never, ever thought I was going to read about them at this level of details on the public internet but since the story has been published by the Swedish chapter of the AOC, the contents must have been duly vetted so it should be safe to link. I think the pdf linked below contains a lot of general goodies but if you are especially interested in the AJ-37 countermeasures suite and usage there is a special section about that which contains details about tactical use of the countermeasures on the AJ-37 and technical details about the radar warning system, KA, KB and U22 pod systems. For those of you who don’t read Swedish: Don’t despair: Simply copy the sections that interested you and run through Google translate. It works surprisingly well….. https://www.google.se/url?sa=t&rct=j&q=&esrc=s&source=web&cd=1&cad=rja&uact=8&ved=0ahUKEwiOsvWmvtHKAhVCiSwKHf2wDk0QFggeMAA&url=http%3A%2F%2Fwww.vikingroost.org%2Fpdf%2FMMrapport__utg_2.pdf&usg=AFQjCNH_JuQq8kQliBQ1IIAfnnEAt1qfSw

Maybe so but I posted the story mainly because I thought it sounded pretty hairy to land on a runway you can't see while squeezing in between pines......;)

Concerning the width of Swedish road base landing strips: They were not always that wide...... A friend of mine flew J-35 Drakens out of J21 in Luleå in the 80' and he once told me this story: "When landing on a road base, you did not always see the actual runway due to it being so narrow and due to the high aoa. However, all you had to do was to ensure the pines on your left and right were at the same distance from your wingtips and you were good to go.....:music_whistling:

A small anecdote: I can actually personally testify that the stick forces to move the ailerons on a Fw-190A are small and that there was very little friction in the system. ;) When I was a kid I visited the National War Museum I think it was in Johannesburg SA and in those days the cockpit was open and you could actually lean in. I distinctly remember the feel of moving the stick and the squeak it make. The crate had been sitting outside (under a roof) for 30 years by that time but it still moved smoothly. Probably as close as I'm gonna get to flying a Warbird.......

The 190D9 "Ersatzteilliste" mentions "Stosstange" i.e. pushrods and in the picture below the linkage that connects the ailerons to the control column look very much like a rod system. The 190A series also have a pushrod system for the ailerons AFAIK.

You miss the point Crumpp: I never said the ballast changes the CG limits or that it was added for this purpose. Ballast in the tail is added to shift the CG rearwards to DECREASE the stability of the plane. I’m not at home now so I don’t have my notes but I calculated the CG of the Mk9 sans rear fuel and it’s around 6.3” from the datum without ballast. Now apparently, the boffins at Supermarine thought this was too far forward so they add 17.5 lb ballast to shift the CG back to circa 6.8” in this configuration. If memory serves me right the rear limit is at 9” so it’s still well within the allowable range. So no, they did NOT add the ballast to change the CG range. They added the ballast to shift the CG of the plane which affects ALL load conditions from empty to fully loaded. The concept I’m trying to explain is that the CG is still within the range and they did not have to add the ballast. However, adding ballast shifts the CG backwards for ALL load condition, making the plane more unstable in ALL load conditions. Now ask yourself, from which state does it make sense to increase instability? On a plane that is stable or on a plane which is already unstable? As I have a life outside these forums, don’t expect another reply until tomorrow evening CET. Me and the missus are going to the theatre. It's a deal we have: She get's to watch some unstable actors, I get to fly some stable planes in DCS! ;)

In addition to all the pilots accounts I'd say read the POH for the Mk9: This describes the Spitfire as "pleasant" to fly. Two points here: First, I seriously doubt the publication was written to be read by pilots of Chuck Yeager's ability and above. Second: Find me an airplane that is unstable with the pilot in direct control, i.e. without FBW, that pilots describe as "pleasant" to fly. :joystick: So summing up: The only evidence suggesting Mk9 instability in this thread has been connected with fuel in the rear tank. In addition, contrary to earlier claims there seems to be no Mk9 instability report. Nor is there any other evidence suggesting that the Mk9 is unstable unless there was fuel in the rear tank. However, we do know that the designers did put ballast in the tail which reduces stability which only makes sense on an already stable plane. The result is a plane which AFAIK the overwhelming majority of all who flew it loved and if anyone can find data suggesting pilots professing love for unstable planes I'd love to see that. :)

And let's not forget the Rb-15F: AFAIK the AJ-37's were upgraded to be able to carry that as well and that is a way more advanced missile much more difficult to spoof.

An example of a Baltic scenario where the AJ-37 would fit in: The linked clip shows recorded PPI films from a Swedish radar station on Gotland. Again, it's in Swedish but there are some nice Baltic scenarios included in which the pictures do the talking: One (about 19:30 into the clip) is a WP exercise in which 20 Su-24's, 15 Tu-16's and 6 An-12's practice. The scenario begins with a column of An-12's (EW-versions) that fly out west and start laying chaff and then turn north. The accompanying Tu-16's then unleash heavy jamming at about 20:10. According to the speaker, about 100 WP a/c in total participated in the exercise. If this would have been a hot Baltic scenario, you can be sure there would have been plenty ships steaming west with sea-skimming AJ-37's unleashing swarms of RB-04 as well. :music_whistling:

I'm with you IF they manage to pull all of that off. But doing all that seems like a HUGE undertaking compared to "just" doing a plane so I really hope they don't choke on it. OTOH, being a Swede you will not see me complaining if they model the Baltic and Gotland. :thumbup: