A-3 and A-5 damage model - asymmetric HS

[Guest deleted@50488]

I've noticed that it's really easy to lose our left or right horizontal stabilizer and associated elevator when hit while flying the Fw 190 A-3 and A-5 models, so I decided to test the flight model / damage model and, as soon as I get such damage, and no major damage affecting wings or rudder and vert stab, I try to get away from the combat arena, and climb to at least 2000m and:

 

.) I push and pull the stick, while flying wings level, at constant power settings, trying to notice any asymmetry / rolling moment due to it, but most of the time if the aircraft rolls it does so opposite what I would expect;

 

.) To exclude possible prop effects, I then turn the engine off, and rinse and repeat my tests:

 

Let's say the port HS and elevator are lost. When we pull the stick, the resulting moment of the right elevator and HStab only pushing the tail down ( nose up ) should, I believe, cause a right rolling tendency. 

Also, if instead i push the stick, the fact that now we have tha tail rising and the force created is "applied" on the right side of the tail only, I would expect a left rolling tendency ?

 

As I get down, my engine stopped, bleeding off speed, and nearing Vs0, I continue with my stick inputs, but no plausible rolling moments result.

 

I believe that something is missing here, either in the damage model or in the flight dynamics model itself.

 

I am trrying to make tests with other fighters, but haven't yet found one that so easily loses it's left ot right horizontal stabs :-)

[Finkeren]

I’m no aeronautic engineer, but I don’t see why you’d expect a significant tendency to roll?

 

The lift generated by the elevator is applied to the entire width of the elevator more or less evenly, and as such there is no significant leverage effect, unlike the aileron, where the lift is generated only in the outer portion of the wing (and where you do get highly asymetrical control forces if one aileron is out of action)

 

You might expect a very slight rolling motion in the directions you describe due to the fact that the right elevator is joined with the fuselage at a point slightly to the right of center, but that distance is only a few cm so any leverage will be minimal and rolling motion minimal as well.

[Finkeren]

I don’t know if you build scale models Jcomm, but if you have a model of a ww2 era fighter, try putting it in front of you on the table, then place your finger on the underside of one of the elevators and try lifting the tail by applying pressure on the entire width of the elevator, the tail should lift pretty evenly. Now try doing the same thing but this time only apply pressure to the outer tip of one of the elevators, and now you should get the rolling motion and you might even flip the model over.

[Guest deleted@50488]

I see your point Finkeren, but I guess that given the planform of the 190 HS, and even taking into consideration where hinge forces are applied, I would expect that the calculated force will be somewhere near mid spar width, so still creating a moment, I guess ?

Edited January 3, 2018 by jcomm

[Finkeren]

I see your point Finkeren, but I guess that given the planform of the 190 HS, an even taking into consideration where hinge forces are applied, I would expect that the calculated force will be somewhere near mid spar width, so still creating a moment, I guess ?

As I said: I’m no engineer, and it’s very likely there’s something I’m overlooking, but I do suggest you try the little experiment for yourself to observe the difference between applying force at one point vs over the entire width of the elevator. The difference is quite remarkable.

[Guest deleted@50488]

Yes Finkeren, I agree it makes a difference, and your argument is surely valid - I am thinking about it because indeed, and specially given the elevator spans practically across the whole HS section ( left or right HS ) this can be seen as the aerodynamic force being evenly distributed along the whole section...

 

I did do R/C gliders, and some even with electric motors , many many moons ago :-)

Edited January 3, 2018 by jcomm

[A_radek]

 

I did do R/C gliders, and some even with electric motors , many many moons ago :-)

Same same, an obsession in my younger days when pocket money wasn't sufficient for the bigger toys. Squeezing in a far larger engine than what the rc airframe should have was good fun. On one of those occasions (and because this 1.2 meter span balsa model was held together with mostly duct tape) an elevator half started fluttering every high speed pass. Horrible sound but a good laugh so kept pushing it and of course it just broke off. I remember expecting it to crash but other than reduced elevator control especially at low speed it flew just fine. As the kid I was I didn't notice any rolling tendency at all. Though I'm sure a more skilled aerobatic pattern pilot would have noticed a pull through maneuvers. The model was not very scale, low wing box fuselage, semi symmetric airfoil and very little dihedral. Proportionally a larger stabilizer area and stabilizer span compared a ww2 fighter as most rc aircraft have.

 

On a side note I do suspect there's something fishy going on with the 190 stabilizer dm. In the last 2 days I've managed to sever an elevator half off three 190 boys online while not managing to do much else. Not sure if its an oversized hitbox, too few hp points on it, my imagination or something intentional.