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Ben_Chiu Certificates/Ratings/Crew Stations: 15. "RE: Adverse yaw and roll coupling" 11-19-02, 23:35z  Greeting Mike: > This is from a non-pilot as you know, so bear with me <g>. No worries. There are plenty of pilots out there that don't understand as much aerodynamics as perhaps they should. > My > understanding is that the adverse yaw condition is caused (assuming a > left bank) by the right wing generating more lift (aileron down) hence > more induced drag than the left wing. That induced drag makes the plane > yaw to the right....correct? Correct. > Now, in a knife edge configuration, the rudder acts alone to pitch the > airplane "up." Since it's a purely vertical move, I wouldn't expect yaw > (along the defined "pitch" axis) at all. Similar to moving the elevator > in level flight to pitch up. However, I *would* expect a roll tendancy > to the upper side of the low wing. In other words if you were in knife > edge flight with the left wing pointed to terra firma, and pitched up > with rudder, I'd expect the airplane to tend to roll to the right due to > the increased airflow over the lower wing. I would agree with that. This is roll-coupling. If the rudder did truly act as an elevator (discounting left-turning tendencies in single-engine props), you wouldn't get that roll to the right. I just used the knife edge example to place the rudder in a "position" where it's similarity to an aileron could be more easily pictured in the mind's eye. Let's try this. What happens if an airplane is in a dive and rudder is applied? Does roll-coupling increase, decrease, or remain the same (assuming the same airspeed)? And to get to my question, is there any pitch (rotation along the horizontal axis parallel with the wing) change when rudder is applied? Based on the adverse yaw model, there should be a pitch change, but is there? I suppose we need to define a couple of things here: Adverse yaw is a rotation/movement along a perpendicular axis (vertical axis--yaw) from the originating aircraft movement (longitudinal axis--roll). Given this relationship, I would expect that if the rudder was placed in the same orientation, it would have a similar reaction (rotation on a perpendicular axis). Well, we see a reaction that fits this perpendicular axis, but it's along the longitudinal/roll axis, but it's not what you'd expect. Enter the knife edge flight example. If you applied upward or downward rudder, shouldn't induced drag affect pitch (as in pitch along the horizontal axis) the same way that induced drag creates adverse yaw? To my thinking it should (but the roll-coupling issues leads me away from this), but I have never had the opportunity to test it and see for myself. This is why I was hoping one of the folks that flies akro could tell me. > Just my common sense thoughts... And good ones! Ben -= VPC OffLine Reader 2.1 =- Registered to: Ben Chiu -OLR.PL v1.80- Remove | Alert Edit | Reply | Reply With Quote | Top

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Subject      Author      Message Date     ID      Adverse yaw and roll coupling    Ben_Chiu       11-16-02              RE: Adverse yaw and roll coupling    Tarmack       11-18-02       1            RE: Adverse yaw and roll coupling    Ben_Chiu       11-18-02       4                 RE: Adverse yaw and roll coupling    djpacro       11-19-02       9                      RE: Adverse yaw and roll coupling    Ben_Chiu       11-19-02       14                 RE: Adverse yaw and roll coupling    Mike_Greenwood       11-19-02       10                      RE: Adverse yaw and roll coupling    DHamblin       11-19-02       12                      RE: Adverse yaw and roll coupling    DHamblin       11-19-02       13                           RE: Adverse yaw and roll coupling    Ben_Chiu       11-19-02       16                      RE: Adverse yaw and roll coupling    Ben_Chiu       11-19-02       15                           RE: Adverse yaw and roll coupling    djpacro       11-25-02       21                                RE: Adverse yaw and roll coupling    Ben_Chiu       11-25-02       22         RE: Adverse yaw and roll coupling    DHamblin       11-18-02       2            RE: Adverse yaw and roll coupling    Ben_Chiu       11-18-02       5                 RE: Adverse yaw and roll coupling    DHamblin       11-18-02       7                      RE: Adverse yaw and roll coupling    Mike_Greenwood       11-19-02       11                           RE: Adverse yaw and roll coupling    AlanParkinson       11-22-02       19                                RE: Adverse yaw and roll coupling    Mike_Greenwood       11-23-02       20                      RE: Adverse yaw and roll coupling    Ben_Chiu       11-19-02       17         RE: Adverse yaw and roll coupling    IFLYExtra300S       11-18-02       3            RE: Adverse yaw and roll coupling    Ben_Chiu       11-18-02       6                 RE: Adverse yaw and roll coupling    Tarmack       11-18-02       8                      RE: Adverse yaw and roll coupling    Ben_Chiu       11-19-02       18                 RE: Adverse yaw and roll coupling    ghmorris       12-01-02       23                      RE: Adverse yaw and roll coupling    ghmorris       12-01-02       24                      RE: Adverse yaw and roll coupling    Ben_Chiu       12-01-02       25                           RE: Adverse yaw and roll coupling    ghmorris       12-02-02       26                                RE: Adverse yaw and roll coupling    Ben_Chiu       12-02-02       27                                     RE: Adverse yaw and roll coupling    ghmorris       12-02-02       28

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