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P factor. Relative wind in a climb…

Asked by: 2548 views ,
Aerodynamics, Commercial Pilot, Flight Instructor, Private Pilot, Student Pilot

Very confused. P factor is always described as if during a climb the relative wind is no longer parallel to the forward movement of the aircraft. A steady climb or descent has the same relative wind as straight and level. So how is P factor even possible? I would agree that during the initial change from straight and level to a climb there is a change in relative wind. But once established it is no different than straight and level. So is p factor only an issue for a few seconds? It is taught as though during the entire climb it’s an issue. If so how is this possible if it all depends on the relative wind change?

 

http://www.aviation-history.com/theory/relative_wind.htm

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4 Answers



  1. Mark Kolber on Dec 26, 2019

    You are “in” the relative wind. If there is any difference at all, it’s negligible.

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  2. Best Answer


    Craig on Dec 26, 2019

    aeroskytech.com/english/firstnotions/firstnotions.html
    aopa.org/images/asf/spin_8.jpg

    Take a look at the diagrams on the web pages above. Look at the pitch angle diagrams, flight paths and AOA’s.

    It’s true that the relative wind is the parallel and opposite direction of the aircraft flight path. Draw a straight line horizontally through the body of the plane from nose to tail. That angle between the plane’s longitudinal axis and the flight path will likely be greater for an aircraft in a climb than for an aircraft in straight and level flight. Thus the AOA of the propeller blade will also be greater, which increases the P-factor.

    It’s kinda like slow flight. You’re flying straight and level (and probably unaccelerated). The relative wind is opposite the flight path. That propeller blade is tilted upward. The angle of the wings or the angle of the propeller blades in relation to the relative wind is much greater in slow flight than in straight and level unaccelerated cruise flight….so more P-factor.

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  3. ednpilot on Dec 26, 2019

    It has more to do with the speed rather than condition of flight (climb/descent, etc). Because when P Factor is talked about, it\’s usually in the context of \”in climb attitude at slower speeds\” – this is because at slower airspeeds, the relative wind and flight path don\’t necessarily correspond with the angle your airplane is pitched up. You might be pitched up significantly, but if you\’re going slow enough, you\’re flying straight and level (slow flight while holding altitude). Thus rudder is required during the entire portion of flight you\’re in a pitch-up attitude while at slow speed because that downward sweeping blade is taking out a \’bigger bite\’ of air during that time. Once you gain enough speed, you\’ll notice that your required rudder diminishes because your flight path/relative wind are opposite each other (for the most part) in the climb (usually a little rudder is required during a climb in a single-engine).

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  4. dmatthewp on Dec 26, 2019

    Craig. Thanks. Best diagram I’ve seen. It may not be true but I don’t thing the PHAK or any other publication explains it this way. I only see a propeller at an angle and relative wind depicted as slicing across the aircraft at an angle. I wish they would add the think of it as slow flight” with the trajectory of the aircraft flattened as compared to the pitch angle. Now I understand it perfectly.

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