Oryx

Yes, that is indeed one way to do it. More primitive actuator disk models used in older CFD codes usually neglected rotation imparted on the flow (it is one of their fundamental assumptions and "1D" momentum theory cannot capture it), although there could be more sophisticated actuator disk models that do capture it. The ones I am familiar with were useful for predicting overall propeller performance and the large scale influence of the propeller, but would not capture things such as induced cross-flow velocities. However, with moving meshes it is now possible to model the individual blades, a

Dancho The NACA reports, AIAA articles and textbook that I listed are all useful references and go a long way towards both understanding the underlying physics and modelling it. Like many (in fact, most) things in aerodynamics, there is no simple method consisting of a single equation that will give you all the answers. The papers you referenced are not really directly relevant to slipstream modelling - at least I don't see the direct link. However, I have often used quaternions in flight dynamics modelling as an alternative to Euler angles. That is a bit of a different topic though.

Not quite - the shift usually starts happening in the transonic regime and any shock formation around the aircraft, even when still subsonic, starts changing the trim requirements significantly. It just becomes more pronounced when fully supersonic. The A-6 could get well into the transonic regime. That being said, a requirement for a wide CG envelope, for example to carry a wide variety of stores, would also require more down force from the tail for the most forward part of the CG envelope, regardless of compressibility effects.

It is actually very common, especially on the jets built prior to the fly-by-wire era. At supersonic speeds, the aerodynamic center of the wing moves from about 25% m.a.c. to 50%, so the neutral point also shifts rearward accordingly. The result is that the jet becomes overly stable and "nose heavy" at supersonic speeds, requiring very high down force from the tail for trim. It therefore made sense to use airfoils with "negative camber" or some other method to deal with the high download requirement. The F-4 is another good example. Some jets would compensate by transferring fuel rearwards (su

I have not read the other discussions you have written that one of the other posters alluded to, but you are definitely mistaken on this topic. (That is unless you were referring to the incorrect use of "spiraling" instead of "helical", but that is obviously semantics - the rest of the description made it clear what Fly-n-hi was referring to.) In fact, the propeller has to impart rotation into the slipstream as it is the direct reaction of the air to the torque. In turbine engine design for example, it is one of the reasons for the stator blades/disks behind the moving blades. I certainly do n

All WWII aircraft had airfoiled fins. A symmetrical airfoil shape is still an airfoil. I think you meant to say "cambered" instead of "airfoiled". Cambered means that the mean camber line is not a straight line or, in other words, that the airfoil is asymmetrical.

Hi Berkut A question: Are you calling BS on the comparison to the F-22 top speed, or the claim of 2500 km/h? The 2500 km/h is approximately Mach 2.35 at 36,000 ft, which is the same as the max Mach for the Su-27. I think they simply use the Su-27 number for press releases, which is probably quite plausible and I also wouldn't be surprised if that number was used as a design target. I don't think it is particularly unrealistic and by now they probably did the envelope expansion already on an earlier prototype, so it is not impossible that they have already achieved it also. As far as I kno

Strange, I just tried it and it worked. I also didn't get the advertisements as I am using AddBlockPlus. I use Firefox, by the way. When I click on the link, there is a short countdown on the MegaFileUpload site before the download button activates. Then left-click on it, and after a second or two Firefox asks me where I want to save the file. It is a .rar, so you need something like 7-zip to unzip it.

True - I don't agree with every decision they made over the years. None of their kits is perfect either. Still, I think they put more effort in to get things right than the majority of other companies and the results generally speak for themselves: The 1/48 MiG-21 series (with the exception of the Bis nose), 1/48 Bf-109E, 1/48 and 1/72 Bf-110, Hellcat and now the Spitfire. All of those kits are among the best kits you can buy for the aircraft they represent. Maybe all still short of perfect and most of them have at least a few issues, but all very, very good. With that track record, I can easi

I think what they do is called marketing, and it is VERY effective - look at the rate at which people are buying their kits. However, in the case of Eduard's new kits, much of their own excitement about their products is very much justified. Notice that we are discussing a minor dimensional detail on one decal on their sheet, rather than fuselage length, or wing shape or other more serious issues. The very fact that this is how deep you have to dig to find mistakes is an indication of how good the kit is. I think in the case of the new Spitfire, what they produced pretty much IS the best and m

I have this on DVD - I think I bought it at MAKS - and I think it is actually the best documentary on the Su-27 that I have seen so far, with a lot of footage from inside the design bureaus and a lot of information that I wasn't aware of even though I have many books (in English and Russian) on the aircraft. Only partially related to the topic - not long ago I had the opportunity to have a long discussion with one of the TsAGI directors, who told me the whole background on the development of the "Pugachev Cobra" maneuver. This went all the way from the initial discovery of the hysteresis in t

Honza, I think this model is absolutely beautiful. I truly wish I had your skills and talents. I would also like to add about the weathering. Personally, I love the way it looks on this model. A lot of people are unhappy with how this type of weathering compare to photographs of the real thing. However, I feel one has to be very careful of photographs. One of my other hobbies is aviation photography, and over the years I started trusting photographs less and less when it comes to its depiction of fine surface details as well as colour. I have noticed in many of my collections, depending on th

I think you will have to explain a bit better what it is that is so offensive about the bunnies? I don't get it, and I think I have read every Eduard Info magazine that came out. As for the MiG-21MF kit that got you entry into the club, if that is the MiG-21 you were referring to: It came with decals for the bunny-scheme, but also two alternate schemes, so you can certainly build it as a "normal" MiG-21MF. Lots of aftermarket MiG-21MF decals also available if you want something different. The box comes with a lot of Brassin add-ons, including cockpit, wheels and weapons, so is in itself a pr

I agree in principal with what you say, but I would like to add that every modeller has his own idea of what a minor and what a major inaccuracy is. Even if I was to disagree with Gabor's overall assessment (I am waiting for more information before I make any decision on that), I do feel that with the amount of research he is doing and the amount of information he is providing, I can give him some leeway to express his opinion in whatever wording he feels is suitable. I am sure we all know what part of what he says is just an opinion. If he was insulting individuals, I would agree with the cri

I understand your comments completely, Gabor. I have worked with the full-scale Mirage F1, Gripen and a few others, all in the flight test environment. I (and a few of my colleagues who also build models) cringe each time the ESCI/Italeri Mirage F1 or the Italeri Gripens are described as accurate or good kits that just need a bit of work. Some are apparently satisfied by those models, but I have stared at the plastic in the box many times and then put it back on the shelve hoping someone will one day do something better. Making all the corrections that I know have to be made is just a little t