Jetstream96

Default cessna won't spin

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Just bought x-plane 11 and tried the default Cessna 172. I enter a stall, and apply full left rudder and full back elevator. However the plane just will not spin. Instead it enters a spiral turn every time. I also tried to move the CG to the back but still no spin. Is this a known issue or I am missing something?

Thanks

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Without knowing the X-Plane 172 at all, the real 172 is quite spin-resistant and there are many who share your experience trying to demo spins in the real aeroplane!

Leaving a little bit of power (~1400-1600 rpm) on, and adding some pro-spin aileron are accepted techniques to help provoke it... but you may still just end up in a lazy spiral dive.

Good old Cessna...

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Regarding spin, I don't know, but even making sure my "Stability Augmentation Sliders" are full right ( none ), it acts like a FBW F35, stopping instantly any roll rate as soon as the yoke is brought to neutral :-/

The Airfoilabs C172 behaves more credibly though...

Didn't test spins on either, but it appears to not be that difficult IRL, or in other sims... FSX / P3D, AEFS 1 & 2...

 

 

 

 

 

 

 

 

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The flight model of default aircrafts is not as carefully tuned as you would expect on a high-end 3rd party aircraft, especially in the out-of-envelope regimes. This is also true e.g. for FSX or P3D, where the flight model of the default aircrafts is more "basic".

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I noticed the same in Xplane 11. The C172 is very resistant to spinning (like the real airplane.) The best I could get was incipient spin and the airplane flew right out.

Very happy with the more complete flight dynamics in Xplane 11.

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5 hours ago, skelsey said:

Without knowing the X-Plane 172 at all, the real 172 is quite spin-resistant and there are many who share your experience trying to demo spins in the real aeroplane!

Leaving a little bit of power (~1400-1600 rpm) on, and adding some pro-spin aileron are accepted techniques to help provoke it... but you may still just end up in a lazy spiral dive.

Good old Cessna...

Oh my power was on idle. Perhaps that is the reason why I can't spin. I will definitely try your techniques tomorrow. Will come back and report the results.

3 hours ago, KenG said:

I noticed the same in Xplane 11. The C172 is very resistant to spinning (like the real airplane.) The best I could get was incipient spin and the airplane flew right out.

Very happy with the more complete flight dynamics in Xplane 11.

Thanks for the useful info. Indeed I could make this bird to spin momentarily in x-plane. 

3 hours ago, jcomm said:

Regarding spin, I don't know, but even making sure my "Stability Augmentation Sliders" are full right ( none ), it acts like a FBW F35, stopping instantly any roll rate as soon as the yoke is brought to neutral :-/

The Airfoilabs C172 behaves more credibly though...

Didn't test spins on either, but it appears to not be that difficult IRL, or in other sims... FSX / P3D, AEFS 1 & 2...

I tried stability augmentation at 0 and 50% and didn't see any difference regarding spin.

I heard Airfoilabs is pretty good. But I don't really want to spend $$ on addons yet. 

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18 minutes ago, Jetstream96 said:

Oh my power was on idle. Perhaps that is the reason why I can't spin. I will definitely try your techniques tomorrow. Will come back and report the results.

Good luck! Remember also that you will need to hold the pro-spin inputs (i.e. full rudder and full back stick) otherwise the aeroplane will generally recover by itself very promptly.

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16 hours ago, skelsey said:

Good luck! Remember also that you will need to hold the pro-spin inputs (i.e. full rudder and full back stick) otherwise the aeroplane will generally recover by itself very promptly.

Just tried it again. The best I can do is spin for about 270 degrees. The stalled wing has a strong tendency to drop and the plane always recovers from spin on itself. I guess the flight model for the default Cessna isn't the best. Anyways it's good enough for me and right now I am enjoying some cross-country flights in this little bird.

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To be honest, to my knowledge there isn't any add-on aircraft that has a 100% realistic spin behaviour in X-Plane (unless I missed something). While on the other hand there are aircrafts for FSX (e.g. RealAir) and now also for AeroflyFS 2 that seemingly feature some realistic spin dynamics.

Since X-Plane uses correct equation of motions, allows customization of moments of inertia, and allows customization of aerodynamic coefficients for the airfoils in the 0-180 range, there shouldn't be anything that prevents the implementation of realistic spin dynamics. But probably it's something that is not so easy to achieve.

The only limitation is that X-Plane does not allow to define custom flight control effectiveness for a given AoA, but this should have been improved in X-Plane 11 according to release notes.

 

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Actually, the K-21 in X-plane, which is a default and rather "old" model ported from XP9, spins better than the real thing, which is very difficult to get into a decent spin :-)

I have a good deal of hours logged in AS-K21s IRL, and was only able to spin properly when flying alone, or flying with a good rearward CoG ...

But the stall characteristics of the X-Plane 10 & 11 AS-K21 are very far from realistic - I guess that, just as Murmur pointed out, edting the corresponding objects in airfoil maker would allow to fine tune it for better / more plausible stalls ...

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The problem I noticed is that any aircraft that is capable of spin in X-Plane, can then be easily induced to flat spin (often unrecoverable) with pro-spin ailerons. I suppose this is not a realistic behaviour for every aircraft.

 

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Actually, there are a number of aircraft in which spins are prohibited. The C172 is a spinner but it is a lazy spinner. The 152 is a better spinning aircraft. For an airplane that can be held in a spin, the Extra 300 is an excellent airplane for doing spins. That is an airplane I recently flew and did 13 left turns and 1/2 turn to the right on recovery.

By, default FSX/P3D are very poor in the realm of spinning. I have not tried Real Air, but I did try A2A and was unable to spin their Cherokee. I don't own their C172. I have also discovered that accelerated stalls and wing unloading are non-existant in FSX/P3D. You can do both all day long in Xplane. 

 

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49 minutes ago, Murmur said:

The problem I noticed is that any aircraft that is capable of spin in X-Plane, can then be easily induced to flat spin (often unrecoverable) with pro-spin ailerons. I suppose this is not a realistic behaviour for every aircraft.

 

This is a very good observation. I noticed it in various add-ons indeed, and it also puzzles me why if they spin and stall more or less plausibly, they also tend to enter those deadly flat spins...

Even worst then, the rate at which they spin around the "Z" axis is incredably fast, as if there was no drag at all...

 

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2 hours ago, jcomm said:

This is a very good observation. I noticed it in various add-ons indeed, and it also puzzles me why if they spin and stall more or less plausibly, they also tend to enter those deadly flat spins...

I guess the problem is that accurately simulating these situations at the edge of and beyond the normal flight envelope is extremely challenging.

Even professional, multi-million-dollar ZFT-certified full flight simulators struggle to simulate the stall accurately, so I guess we have to be realistic in our expectations of our $60 software running on a desktop PC!

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9 minutes ago, skelsey said:

I guess the problem is that accurately simulating these situations at the edge of and beyond the normal flight envelope is extremely challenging.

Even professional, multi-million-dollar ZFT-certified full flight simulators struggle to simulate the stall accurately, so I guess we have to be realistic in our expectations of our $60 software running on a desktop PC!

That is true, but other flight sims and add-ons have demonstrated that they can do a decent reproduction of spins (as also acknowledged by real life pilots on forums), so it would be nice to have something like that in X-Plane too.

 

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