31-03-2015, 08:05 PM
It was fun 
Knife edge is basically a harrier turned on its side. For a given airspeed, a certain (significant) amount of rudder deflection is necessary to keep the plane flying in a sustained horizontal line. The ailerons are mostly centred, except for tiny corrections to keep the wings pointing at the sky & ground. Optionally, the elevator can be used to steer circuits.
Once comfortable with sustained upright harriers and knife edge, inverted harriers are the next step. Four-point rolls are relatively easy by then. With more practice, those lead to rolling circles, and then rolling harriers - possibly the most iconic of all 3D plane maneuvers. Knife edge may not seem all that interesting or useful, but it's in fact a basic building block of a lot of advanced aerobatics.
Also, knife edge is a good way to gauge whether a plane is neutral in its handling. Anything with dihedral or washout, like a typical warbird or glider, will attempt to roll its way out of a knife edge posture. Other planes might pull toward the canopy or the landing gear, as if the elevator is being applied (except it's not!). Well-balanced and purpose-designed 3D planes will maintain their knife edge posture with only minimal corrective input.
Knife edge is basically a harrier turned on its side. For a given airspeed, a certain (significant) amount of rudder deflection is necessary to keep the plane flying in a sustained horizontal line. The ailerons are mostly centred, except for tiny corrections to keep the wings pointing at the sky & ground. Optionally, the elevator can be used to steer circuits.
Once comfortable with sustained upright harriers and knife edge, inverted harriers are the next step. Four-point rolls are relatively easy by then. With more practice, those lead to rolling circles, and then rolling harriers - possibly the most iconic of all 3D plane maneuvers. Knife edge may not seem all that interesting or useful, but it's in fact a basic building block of a lot of advanced aerobatics.
Also, knife edge is a good way to gauge whether a plane is neutral in its handling. Anything with dihedral or washout, like a typical warbird or glider, will attempt to roll its way out of a knife edge posture. Other planes might pull toward the canopy or the landing gear, as if the elevator is being applied (except it's not!). Well-balanced and purpose-designed 3D planes will maintain their knife edge posture with only minimal corrective input.