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Pitch-roll oscillations during spins


Maverick Su-35S
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Hi,

 

After reading the following article: https://forums.eagle.ru/attachment.php?attachmentid=145242&d=1469709160, I was very delighted to understand the effects and differences in performance obtained within various changes that the F-5 had benefited of throughout it's design program and I couldn't wait to jump back in the cockpit of this purely lovely DCS product to try and replicate some of that article's results which of course, regard the flight model of the aircraft in DCS.

 

The main reason why I fly in DCS is because the flight models of each aircraft can bring me closer to how would the aircraft behave in a real flight, so the flight model of each aircraft is what I put my money on and my main goal for using flight simulators. Doing missions, shooting, fighting is on 2nd place and anyway..., every game is good at that, but a simulator..., can only be as good as what it can best do.

 

Now, the reason why I start this thread is because, although I've read the article and I acknowledged that ED knows about it, I can't yet find some stall&spin characteristics of the aircraft during it's flight tests. In it's early patches, the F-5 in DCS was prone to depart in yaw at slightly above 20 deg. AoA, which was indeed much lower than what tests showed in the above article including the fact that the real jet proved to be stable in roll-yaw at very high angles of attack of 45 through almost 70 most probable due to the high energy vortex generated by the lerx (leading edge root extension) which improved aileron and rudder effectiveness. Even if in the early patches the F-5 was prematurely departing and possibly had an exaggerate loss of controls effectiveness during spins, the wing rocking effect and pitch oscillations during spin were present and seemed realistic. Now these important effects seem to not be present anymore and I believe that are must!

 

In real life a fighter with lerx indeed finds the pitch-roll oscillations during spins at much higher angles of attack and has an increased tendency to these effects during spins in comparison to a non-lerx airplane. Sometimes, depending on the yaw rate (not too high not too low) the rolling oscillation during a spin becomes so intense that the plane may at some point flip upside-down and vice-versa and this is contributed to the wild variation of the center of pressure between one wing and the other. A remarcable aerodynamic effect indeed.

 

Here are some great examples:

 

https://www.youtube.com/watch?v=AJgflKRbYgY

 

 

https://www.youtube.com/watch?v=ZpxD6n9ZWyQ

 

 

https://www.youtube.com/watch?v=xTrLzkA_mCc

 

 

 

Is there any way that pitch-roll oscillations may occur again in later patches?

 

 

A great day and Merry Christmas to everyone!

When you can't prove something with words, let the maths do the talking.

I have an insatiable passion for helping simulated aircraft fly realistically!

Sincerely, your correct flight model fanatic!

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