Full Up Elevator during Cat Launches

[RustBelt]

OK, I'll try to express my concern as simply as I can: HB Tomcat during the in-game cat launches requires no elevator movement to achieve the same pitch at rotation as the real-life F-14 with elevators fully up - why?

 

Because in real life they aren't bring Held full up. They just flop full up during the launch, combined with the nose being latched to the catapult shuttle. Once the Cat Shot ends so does the acceleration force pulling on the stick.

 

To get super gritty it's like this at release (-0 seconds) the elevators are full up, the stick went from having a force pulling back on it to having no force being applied to it. The elevators have lots of force applied to them that's feeding back into the control linkage, with the little bit of deck left the nose strut begins extending forcing the nose up.

 

Between -0 and about +0.5 second the nose up pitch caused by the nose strut extending and the pitch up moment from the elevators drives the bob weight down which applies a forward pressure on the stick mechanism. At the same time the aerodynamic forces no longer being countered by the Hydraulically boosted flight controls being pulled aft by the acceleration force, as well as the bob weight applying forward force on the stick, the elevators quickly unload and streamline to their trimmed position, slowed and restrained from fluttering by the eddy current damper in the control linkage.

 

Meanwhile a plane that's barely flying starts falling off the front of the deck. It's in a fully unloaded state for a split second (say +0.5 to around +0.8 seconds) this "freefall" reduces the bob weight load on the stick allowing the aircraft to achieve a positive AoA trimmed condition (direction of flight combined with relative wind) Now the wings can get a real bite of air.

 

The plane then flies off in trim in a climb. By +1.5 seconds or so the pilot now has their hand back on the stick and is in control of an already mostly trimmed aircraft that if things are going well, is climbing and accelerating.

 

Now, here's why in DCS it doesn't work like that.

1) The carrier is a kludgey beta product rushed out as a stop gap when the F/A-18 was released in Early Access (which it still is BTW). Its deck isn't acting entirely like a real "ground" and who knows how well the Catapult is being accurately modeled either.

 

2) Unless you have a Force Feedback Joystick, the Sim ALWAYS sees a force on the stick due to the Joystick's centering spring. There's never a time in the Sim where the planes Control Stick is actually free of forces and able to bang around. It's slaved to your Joystick which barring a table failure or drunken mis-adventure, is fixed and no load not coming from your input or the centering spring exists on it. So the control stick in the plane doesn't act like it would in a real plane moving around in space with forces acting on it and momentum and such.

 

3) Even with a Force Feedback Stick, inertial mass of the control stick is still probably not being simulated, so unless you're in a 6 degree of freedom motion sim, the plane in the sim accelerating WON'T cause a Force Feedback Joystick to move hands off except in relation to loading on the control surfaces, it's mostly only being fed Control Load based on the aerodynamic model plus mathemagic to "feel" right when you are interacting with it. It's part of why even with a FFB stick you can still pull full aft at Mach 1 and get into an immediate deep accelerated stall, which in a real plane would require a crazy amount of upper body strength to overcome the flight control load and the Bob Weight and Eddy Current Damper. Not to mention the transient G load on your body.

[Belphe]

Because in real life they aren't bring Held full up. They just flop full up during the launch, combined with the nose being latched to the catapult shuttle. Once the Cat Shot ends so does the acceleration force pulling on the stick.

 

To get super gritty it's like this at release (-0 seconds) the elevators are full up, the stick went from having a force pulling back on it to having no force being applied to it. The elevators have lots of force applied to them that's feeding back into the control linkage, with the little bit of deck left the nose strut begins extending forcing the nose up.

 

Between -0 and about +0.5 second the nose up pitch caused by the nose strut extending and the pitch up moment from the elevators drives the bob weight down which applies a forward pressure on the stick mechanism. At the same time the aerodynamic forces no longer being countered by the Hydraulically boosted flight controls being pulled aft by the acceleration force, as well as the bob weight applying forward force on the stick, the elevators quickly unload and streamline to their trimmed position, slowed and restrained from fluttering by the eddy current damper in the control linkage.

 

Meanwhile a plane that's barely flying starts falling off the front of the deck. It's in a fully unloaded state for a split second (say +0.5 to around +0.8 seconds) this "freefall" reduces the bob weight load on the stick allowing the aircraft to achieve a positive AoA trimmed condition (direction of flight combined with relative wind) Now the wings can get a real bite of air.

 

The plane then flies off in trim in a climb. By +1.5 seconds or so the pilot now has their hand back on the stick and is in control of an already mostly trimmed aircraft that if things are going well, is climbing and accelerating.

 

Now, here's why in DCS it doesn't work like that.

1) The carrier is a kludgey beta product rushed out as a stop gap when the F/A-18 was released in Early Access (which it still is BTW). Its deck isn't acting entirely like a real "ground" and who knows how well the Catapult is being accurately modeled either.

 

2) Unless you have a Force Feedback Joystick, the Sim ALWAYS sees a force on the stick due to the Joystick's centering spring. There's never a time in the Sim where the planes Control Stick is actually free of forces and able to bang around. It's slaved to your Joystick which barring a table failure or drunken mis-adventure, is fixed and no load not coming from your input or the centering spring exists on it. So the control stick in the plane doesn't act like it would in a real plane moving around in space with forces acting on it and momentum and such.

 

3) Even with a Force Feedback Stick, inertial mass of the control stick is still probably not being simulated, so unless you're in a 6 degree of freedom motion sim, the plane in the sim accelerating WON'T cause a Force Feedback Joystick to move hands off except in relation to loading on the control surfaces, it's mostly only being fed Control Load based on the aerodynamic model plus mathemagic to "feel" right when you are interacting with it. It's part of why even with a FFB stick you can still pull full aft at Mach 1 and get into an immediate deep accelerated stall, which in a real plane would require a crazy amount of upper body strength to overcome the flight control load and the Bob Weight and Eddy Current Damper. Not to mention the transient G load on your body.

 

That did the trick - thank you! :)

[sLYFa]

NATOPS which we can't officially link here but it's just a Google away.

 

Unfortunately not. Weigth and Balance is a seperate document (actually even unique to a specific aircraft). A few CG numbers for common weapon configurations would be very helpful already.

[draconus]

good advices but no hard data on CG:

https://forums.eagle.ru/showthread.php?p=4033413

https://forums.eagle.ru/showthread.php?t=235235