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Understanding Propeller Torque and P-Factor: Difference between revisions
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Understanding Propeller Torque and P-Factor (view source)
Revision as of 18:58, 21 September 2010
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This is an attempt to answer the frequent question "Why is my aircraft turning left all the time?" | This is an attempt to answer the frequent question "Why is my [[aircraft]] turning left all the time?". | ||
This occurs only in aircraft with propellers at the front of the aircraft. And | This occurs only in aircraft with propellers at the front of the aircraft. And yes, it does occur in real life. Four distinct phenomena cause the effect, all causing the aircraft to turn in the same direction. They are: | ||
==Prop wash== | ===Prop wash=== | ||
A propeller pushes air not just horizontally to the back, but more in a twisting helix around the [http://en.wikipedia.org/wiki/Fuselage fuselage] (clockwise as seen from the cockpit). As the air whirls around the fuselage it pushes against the left side of the vertical tail (assuming it is located above the propeller's axis), causing the plane to yaw to the left. The prop wash effect is at its greatest when the airflow is flowing more around the fuselage than along it, i.e., at high power and low airspeed, which is the situation when starting the takeoff run. | A propeller pushes air not just horizontally to the back, but more in a twisting helix around the [http://en.wikipedia.org/wiki/Fuselage fuselage] (clockwise as seen from the cockpit). As the air whirls around the fuselage it pushes against the left side of the vertical tail (assuming it is located above the propeller's axis), causing the plane to yaw to the left. The prop wash effect is at its greatest when the airflow is flowing more around the fuselage than along it, i.e., at high power and low airspeed, which is the situation when starting the takeoff run. | ||
==Propeller | ===Propeller torque effect=== | ||
Torque effect is the influence of engine torque on aircraft movement and control. It is generally exhibited as a left turning tendency in piston single engine propeller driven aircraft. | Torque effect is the influence of engine torque on aircraft movement and control. It is generally exhibited as a left turning tendency in piston single engine propeller driven aircraft. | ||
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On aircraft with contrarotating propellers (propellers that rotate in opposite directions) the torque from the two propellers cancel each other out, so that no compensation is needed. | On aircraft with contrarotating propellers (propellers that rotate in opposite directions) the torque from the two propellers cancel each other out, so that no compensation is needed. | ||
Further Reading: [http://www.aerospaceweb.org/question/dynamics/q0015a.shtml Propeller Torque Factor] | Further Reading: [http://www.aerospaceweb.org/question/dynamics/q0015a.shtml Propeller Torque Factor] | ||
== P-Factor == | === P-Factor === | ||
P-factor is the term for asymmetric propeller loading, causes the airplane to yaw to the left when at high angles of attack. | P-factor is the term for asymmetric propeller loading, causes the airplane to yaw to the left when at high angles of attack. | ||
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According to What You Need to Know About Aerodyanics... by Franklin Gutierrez. | According to What You Need to Know About Aerodyanics... by Franklin Gutierrez. | ||
== Gyroscopic Precession == | === Gyroscopic Precession === | ||
This is the tendency of a spinning object to precess or move about its axis when disturbed by a force. The engine and propeller act as a big gyroscope. However, gyroscopic precession is likely to be minimal in a typical aircraft. | This is the tendency of a spinning object to precess or move about its axis when disturbed by a force. The engine and propeller act as a big gyroscope. However, gyroscopic precession is likely to be minimal in a typical aircraft. | ||
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== External Links == | == External Links == | ||
* [http://www.auf.asn.au/groundschool/umodule11.html#tophenomena Engine effects and aerodynamic phenomena] Recreational Aviation Australia Ground School article on "prop wash," prop torque, gyro precession, p-factor and other similar factors affecting taildraggers. | * [http://www.auf.asn.au/groundschool/umodule11.html#tophenomena Engine effects and aerodynamic phenomena] Recreational Aviation Australia Ground School article on "prop wash," prop torque, gyro precession, p-factor and other similar factors affecting taildraggers. | ||
* [http://www.americanparagliding.com/propellerforces.htm http://www.americanparagliding.com/propellerforces.htm] The forces of P-factor, gyro precession and asymmetric blade thrust act with particular intensity in powere parachute gliders (paragliders), as this article relates. | * [http://www.americanparagliding.com/propellerforces.htm http://www.americanparagliding.com/propellerforces.htm] The forces of P-factor, gyro precession and asymmetric blade thrust act with particular intensity in powere parachute gliders (paragliders), as this article relates. | ||
{{Understanding}} | {{Understanding}} | ||