Crumpp

Here is another propeller report to add to the discussion! :smartass: http://naca.central.cranfield.ac.uk/reports/1953/naca-tm-1355.pdf

Very Good..excellent links!! Best post yet....just show a little more "Aero" in your "dynamics" and it will be spot on target!! :lol:

Good footage. Notice the airplane is tumbling and not spinning.... It is not that it more valid, the question is what do you want to do with the information? The first report I posted is a mathmatical description of propeller effects on stability. It provides the big picture using a very common and accepted propeller theory. It is not a adoption of helicopter theory either, it is made to model the behaviors of a Constant Speed Propeller on a single engined aircraft. The second report I posted is a mathmatical microscope looking at a very specific and narrow portion of the aircraft behaviors. It simply illustrates the fact propeller effects on the longitudinal axis are not really a factor except for very low velocity just above the stall. It is a mathmatical microscope like the next reports posted in the thread. Unlike the first reports, the preceding reports are not a simple system that describes the propellers effect on the overall aircraft behaviors nor do they even present complete information on propeller effects on stability. All of the reports accurately describe aircraft behavior within the intended scope. The question becomes how much time and computing power one wants to use to get the same result. Of course, that is not even considering the fact only two small areas of effect are described in the other reports given. In otherwords, we need a few more reports and a lot more information!! Make sense now?

Quantity is not really the point. :music_whistling: Thanks for sharing! :thumbup:

Thanks Mugen! Does it work with the P51 and Dora?

Yo-Yo, thank you for taking the time to address the players and the answer you gave on page 2 was good enough! :thumbup: Here is another report dealing with propeller effects on stability and control. This time the influence on static longitudinal stability. Again, it uses blade theory and notes the static longitudinal stability effects are minimal except at very low velocities.

Absolutely. As you point out, the stabilizing moments tend to "hide" the effect leaving the most dramatic effects as the slipstream. Propeller instability effects tend to manifest themselves as a steady build up of force as the aircraft enters slowflight slowing down to reach the stall point in the air. Does DCS use momentum or blade theory? I included a report from the NACA. "Notes on Propeller and Slipstream in relation to stability" uses blade element theory. So you might find it convenient to use provided DCS uses blade theory, LOL.

Keep in mind Jcomm, P-factor is asymmetrical disc loading. The blades are at different angles of attack and therefore producing different amounts of lift. Gyroscopic effect is when the relative wind pushes on the blade, the resultant force is felt 90 degrees in the plane of rotation. They sound really similar but they are not. Torque, P-factor, and gyro effect are all actually pretty minor in effect. The airplane just has a lot of natural dampening working against them such that they do not influence it all that much. The major effect on stability is the spiral slipstream. That is a function of the helix angle formed by the aerodynamic pitch of the blade. The difference between the zero lift blade angle and the angle of attack is the slippage of the propeller. The distance on the helix path of the blade is called the pitch length and varies with velocity and power in a Constant Speed Propeller. How it strikes the fuselage and surfaces of the aircraft determine its effects. There are several mathematical models that attempt to replicate it's effect.

Looks like you got it. P-factor is about the angle of the relative wind on the propeller disc while gyro effect is where the resultant force applied to the disc is felt. Of all the propeller effects, P-factor, torque, and spiral slipstream.... It is the spiral slipstream that accounts for the majority of the "propeller effects" observed. http://www.qmfc.org/school/asym.htm

There is a track of the FW190 entering left and right, power on and power off spins included at the beginning of the thread.

There wasn't a thing said about LE flaps. As far LE slats, I guess designs like the Eurofighter Typhoon do not count?

Exactly. The LE slats are the aerodynamic equivalent of training wheels. There is a reason why most modern fighters use them as well as almost every transport category aircraft in existence in the modern world.

:thumbup:

Why?? Because you are going to watchdog and be the protector of the FM? Seems to me the guy cares greatly about the accuracy of the FM's and once more....knows what he is doing. Not only that, the team is very good about communicating with the players. This is not some ongoing error, either, Kwaitek. This was tested a few weeks ago and was fine with the exception of one small portion of the envelope due to slip stream effects. In tweaking one behavior with the math...sometime other things crop up. That is how it works. The Spin/stall characteristics have changed in the last few weeks. Sometimes it is like that when working with mathematical models. Give them a chance and be glad you do not get "You is wrong" and defensive behavior. Instead, problems are addressed and the sim moves forward. BTW, when you do get "You is wrong" on these boards...it is very likely....You is Wrong. Most of the discussion I have seen arise from a players misunderstanding and misconception. See, like this statement. No aircraft is "spin proof" but some you have to work very hard to get them to spin. It seems to me, the perception of what it means to "work very hard" to enter a spin does not mean anything in your thinking. You thinking "work very hard" means "easy to spin and will get away from you if you are not careful giving constant attention".

I do get it. Go back a couple of pages and look for Yo-Yo's answer. http://forums.eagle.ru/showpost.php?p=2322005&postcount=12

Pay attention....notice how many times they say, "carelessness and ignorance". Again, it is not that easy to get into a spin, the airplane is designed to fly and wants to fly.

If you do spins, it is actually harder than you think to get into one. Try teaching them Yes, pilots do inadvertently enter them from time to time. IMHO, you have to be pretty distracted and behind the airplane for that to happen. The spin entry is fine in DCS with the exception of the power on spins to the right. Yo-Yo is tweaking things in the FM, let's not compound problems by rushing off to fix a secondary effect that is not the problem!

It is not a Cessna 172. It is typical of a high performance low wing taildragger to drop ~30 degrees of wing in the stall IF you do not lift the wing with rudder. It is a combination of propeller effects that cause it with spiral slipstream being the largest contributor. Here....at 5:36...the Mustang does the exact same thing. Listen to the instructor in the few minutes before talk about how gentle the Mustang stalls. He also cautions this pilot about NOT using any lateral input but only use rudder to lift the wing. My Thorp does the exact same thing.

I think you are coming late to the conversation because your comment makes little sense in the context of the discussion. However, I agree that are other methods to evade and counterattack. What is not correct is linking this behavior as "typical" of the design. One can simply look at the lift polars to see there are no violent post stall behaviors in coordinated flight. Eric's description of the control inputs set the aircraft up for a uncoordinated condition which explains things Fredrich. If you understand how to read the shape of a polar curve, there is no argument that can be made the FW-190 had a violent stall in coordinated flight.

Here you go Kwiatek http://forums.eagle.ru/showthread.php?t=136596&page=5&highlight=Crumpp Yo-Yo understands what is causing the effect Kwiatek and is working to improve all these FM's.

What Eric describes and Yo-Yo is trying to tell you is the effect is caused by a deliberate uncoordinated power off aileron turns. You pull the power, hard roll entry in one direction followed by immediate and very hard roll in the opposite direction without any rudder input. There is no rudder input.

No problem. Thanks for the quick reply!!!

As a real life pilot....I know what a spin is Kwaitek. :music_whistling: I just checked it again. Spiral slipstream is a tad overdone. The Dora spins fine power Off to the left and right. Power on it spins to the right but left will not spin because the slipstream keeps it from entering. This same subject came up 3 weeks ago and the aircraft did not act like this. Power on to the left was difficult but not like it is now.

The Dora and P-51 both spin normally. The Bf-109 should be rather difficult to get to spin as it has LE slats.

You are absolutely correct. Just to be clear, I do not think anybody said that sideways force increases. Grass is kind of tough to nail down because it effects change with moisture and grass length. If one "picked a side" as is typical in a less mature bulletin board crowd, one could fill it with "evidence" their point of view is correct. The otherside could do the same. Everyone would be a loser in that situation and our grass fields would simply be extremes instead of accurate. When it is wet and slick it is exactly like Effte describes: The science behind a grass field does not make groundlooping an impossibility, it will just give you a better chance of preventing any swing from developing into a ground loop. :)