The Real Reason
The left turning tendency occurs when the propeller pushes back a stream of air mass which spirals as it streams to the rear.
With its spiraling motion the air mass hits the vertical fin at a slight angle. This pushes the tail to the right and yaws the nose to the left. Heres where the fun begins.
The propeller hits a small particle of air mass at the right -hand side of the planes nose. The impact of the propeller sends it backwards and downward along the right side of the fuselage where it crosses underneath the pilots seat to the left side of the fuselage where it flows upward (cork-screw) and backward along the left side of the tail. It is then ready to cross over the top of the tail back to the right side; but, it finds its path blocked by the tail fin. The air mass particle impacts the fin with a force and shoves the tail fin to the right.
At the same time, in the beginning, another air mass particle is caught by the propeller on the left side of the planes nose. The impact sends the air mass particle speeding backward along the left side of the fuselage and slightly upward. It crosses over the top of the cockpit and flows downward and backward along the right side of the tail. It is then ready to cross underneath the tail back to the left side. But, it runs into a problem. There is no tail fin to block the air mass particle. It exerts no force on anything and flows away behind the plane.
The net result of these two circulating air mass particles is a resultant shove of the tail fin to the right and a yaw of the plane to the left.
In aircraft design the tail fin is set at a slight angle so to line it up with the actual line of direction of the air flow at the tail in cruising, level flight. The true reason for off setting the tail fin is not to make a force but, rather, to keep a force from being made.
In slower flight, as the tightness of the spiral of the air mass particle increases, the sideways shove of force on the tail fin increases. If the design angle offset is not sufficient, the left turning tendency continues and you must hold right rudder.
In gliding flight this tendency doesn't appear because the propeller is not creating a slipstream. The offset built into the tail fin is not necessary and, in fact, yaws the nose of the aircraft to the right. The pilot, in a glide, now holds slight left rudder.
You could abolish the left turning tendency by putting as much tail fin underneath the tail as there is atop the tail. The problem is the tail fin underneath would interfere with the conventional landing gear of a tail dragger. New plane design, with tricycle landing gear, have allowed the tail fin arrangement mentioned above to appear in modern planes.
The H-tail is here and slanted engines have eliminated left turn tendencies that plagued older aircraft.
The left turning tendency occurs when the propeller pushes back a stream of air mass which spirals as it streams to the rear.
With its spiraling motion the air mass hits the vertical fin at a slight angle. This pushes the tail to the right and yaws the nose to the left. Heres where the fun begins.
The propeller hits a small particle of air mass at the right -hand side of the planes nose. The impact of the propeller sends it backwards and downward along the right side of the fuselage where it crosses underneath the pilots seat to the left side of the fuselage where it flows upward (cork-screw) and backward along the left side of the tail. It is then ready to cross over the top of the tail back to the right side; but, it finds its path blocked by the tail fin. The air mass particle impacts the fin with a force and shoves the tail fin to the right.
At the same time, in the beginning, another air mass particle is caught by the propeller on the left side of the planes nose. The impact sends the air mass particle speeding backward along the left side of the fuselage and slightly upward. It crosses over the top of the cockpit and flows downward and backward along the right side of the tail. It is then ready to cross underneath the tail back to the left side. But, it runs into a problem. There is no tail fin to block the air mass particle. It exerts no force on anything and flows away behind the plane.
The net result of these two circulating air mass particles is a resultant shove of the tail fin to the right and a yaw of the plane to the left.
In aircraft design the tail fin is set at a slight angle so to line it up with the actual line of direction of the air flow at the tail in cruising, level flight. The true reason for off setting the tail fin is not to make a force but, rather, to keep a force from being made.
In slower flight, as the tightness of the spiral of the air mass particle increases, the sideways shove of force on the tail fin increases. If the design angle offset is not sufficient, the left turning tendency continues and you must hold right rudder.
In gliding flight this tendency doesn't appear because the propeller is not creating a slipstream. The offset built into the tail fin is not necessary and, in fact, yaws the nose of the aircraft to the right. The pilot, in a glide, now holds slight left rudder.
You could abolish the left turning tendency by putting as much tail fin underneath the tail as there is atop the tail. The problem is the tail fin underneath would interfere with the conventional landing gear of a tail dragger. New plane design, with tricycle landing gear, have allowed the tail fin arrangement mentioned above to appear in modern planes.
The H-tail is here and slanted engines have eliminated left turn tendencies that plagued older aircraft.
