Simviation Forum - What really happens?

Apr 24^th, 2005 at 2:31am

Weekend_Flyer Offline
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Ok, this may sound dumb, but its bugging me! I have FS9, CFS2 and CFS3. Ive noticed on both CFSs that when I pull high G turns my airspeed drops really fast and im constantly stalling. On FS9, I dont have that problem. I can turn all day long and my airspeed never drops. Id like to know what really happens. Which sim is right? Could someone explain? Thanks!

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Reply #1 - Apr 24^th, 2005 at 10:38am

beefhole Offline
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In a prop, if you pull a high-G turn, you can sure as hell expect your airspeed to drop. A lot. In a jet, the airspeed will fall, but not as much.

If you're refering to props in FS, it may have something to do with your realism settings-if they're really low, you can pull an immelman in a 172 at 500 ft. Tongue

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Reply #2 - Apr 24^th, 2005 at 11:34am

TacitBlue Offline
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Ive noticed that too, but I only have CFS and FS9. I thought it had something to do with CFS be old, and maybe they didnt know as much about simulating flight dynamics back then. BTW I fly FS9 with realism on max except for torq (seems a little unrealistic with it on max) and I can turn without stalling immediatly like in CFS.

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Reply #3 - Apr 24^th, 2005 at 11:44am

Hagar Offline
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It might depend on which type of aircraft you're using & also your joystick sensitivity settings. The default aircraft in CFS1/CFS2 always seemed to stall a little too easily to me & I'm not convinced this is realistic. Some were obviously better than others in this respect but I've read that the Spitfire was a pussycat & warned you with a little judder when it was about to stall. Simply ease the back pressure on the stick a little to keep the tightest turn possible for as long as you wished. The CFS flight dynamics are basically the same as used in FS, except maybe FS9 where the flight model was slightly improved. I can't speak for CFS3 as I don't use it.

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Reply #4 - Apr 24^th, 2005 at 12:29pm

OTTOL Offline
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Quote:

.......when I pull high G turns my airspeed drops really fast and im constantly stalling....... On FS9, I dont have that problem. I can turn all day long and my airspeed never drops. Id like to know what really happens. Could someone explain? Thanks!

Quote:

Which sim is right?

choice "A"..... Quote:

when I pull high G turns my airspeed drops really fast and im constantly stalling

Quote:

"

Adverse Yaw

Adverse Yaw ... an operating defect

A fundamental knowledge of aerodynamics is basic to becoming a masterful pilot. A masterful pilot is a safe pilot.

Adverse yaw, like density altitude, is a term tossed about by pilots. Pilots have been trained to know what it is ... at least during their primary training. These terms often become forgotten or ignored with the passage of time.

Flight controls–to be effective–are balanced and responsive. The ailerons, however, have an operating defect.

For an airplane to turn, it must be banked so the total lift is divided into a vertical component that supports the weight of the airplane, and a horizontal component that causes the turn.

To make a left turn, the aileron control is moved left. The right aileron moves down, increasing the camber and lift of the right wing, thus causing it to rise. The left aileron moves up, decreasing the camber and lift of the left wing.

The adverse yaw problem arises (no pun intended) because lift and drag are directly proportional. With the increased lift of the right wing comes increased drag, and the decreased left on the left wing causes a decrease in drag.

These combine to cause the nose to yaw to the right. This momentary yaw (to the right in a left turn, to the left in a right turn) is adverse yaw, sometimes called adverse aileron drag."

If you've read about the "wing warping" F-18 that NASA is working on, you'll see that they are trying to eliminate or at least minimize this effect.

When an airplane turns, let's say a turn to the left for our example, the outboard wing(right, in our case)lifts due to the downward deflected aileron. This aileron increases the wing camber which means more lift and in turn more induced drag(that's drag increase No.1). Because the left aileron deflects in the opposite direction, less induced drag occurs. .....left wing-less drag.....right wing-more drag.... What happens now is that the right wing wants to lag behind, creating a crooked flying(slipping)airplane. To counter this, left rudder pressure must be applied to return the nose of the aircraft to the left. The rudder is now hanging out in the slipstream(drag increase No.2). At this point the aircraft is banked. The wings, whose normal function is to keep the aircraft airborne in the vertical plane are now assisting movement in the horizontal direction(horizontal component of lift)obviously, the wings only produce a certain amount of total lift so if you "rob" some of your vertical lift to use in the horizontal plane the aircraft will want to descend. To counter this, elevator pressure must be increased creating more induced drag(increase number three). Finally, and I'll trim the fat on this one, centrifugal force increases=higher G-load which in turn acts in the same fashion as additional weight(more drag).

.....so I loaded up the plane and moved to Middle-EEEE..........OIL..that is......

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Reply #5 - Apr 24^th, 2005 at 1:04pm

Hagar Offline
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My Spitfire Girl
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I don't know if it's the case with modern jets but the rudder is very rarely used during normal flight on jet fighters like the Hawker Hunter. I discovered this myself when allowed a few precious minutes stick time on a Hunter T.7 many years ago. I made the natural mistake of trying to apply rudder in a normal turn only to find the instructor's boot on the opposite pedal preventing it. I asked him when the rudder is used. He said; when taxying & for advanced aerobatics. Charlie will no doubt be able to enlighten me if it's the same on modern jet fighters.

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Reply #6 - Apr 24^th, 2005 at 2:41pm

Weekend_Flyer Offline
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Thanks for the replys. I have the realisim settings on max on all 3 sims. It seems to happen with any prop in either CFS. After reading all the replys ive kinda come to the conclusion that CFS over does it on the stalls and FS under does it.

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Reply #7 - Apr 24^th, 2005 at 9:12pm

OTTOL Offline
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Fintas, Kuwait (OKBK)

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Quote:

I don't know if it's the case with modern jets but the rudder is very rarely used during normal flight on jet fighters

The rudder is used, the person who normally operates it is the only component that isn't . Due to Dutch Roll tendencies, most jets use a Yaw Damper.
The same physics of adverse yaw apply to a jet. The only major difference would be the mild camber associated with a high speed sub-sonic or super-sonic airfoil(much less induced drag).
The Lear for example uses a coupled system with a torque tube interconnect. Essentially, when you roll the airplane, the torque tube on the roll cable transfers energy to the corresponding rudder cable and aids in coordinating the airplane.
On the Lear, while taxiing, the aircraft can be turned with the yoke as well as the rudder pedals. This isn't intentional and the "control yoke" method of steering is much less precise than the correct, intended method of using the pedals but it demonstrates the system very well(especially to new F/O's). Wink

The Lear also has a primary and secondary Yaw Damper. BUT, deligent use of rudder is absolutey mandatory on this same airplane to prevent dutch roll and maintain coordination during landing. (Later models can actually be landed with the yaw damper on.)

.....so I loaded up the plane and moved to Middle-EEEE..........OIL..that is......

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Reply #8 - Apr 24^th, 2005 at 10:18pm

beefhole Offline
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common' yigs!
Philadelphia

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Just like autorudder, except it makes things easier, not harder Cheesy

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