There are a lot of variable names in the aircraft polar plots.
IS there a list or reference somewhere? I only recognize 20% of them.
Specific plot i want is:
If I have a working aircraft simulation and I want to see the spar bending moment by station from root to tip, what variables would I plot?
Same question for elevator?
is there any way to auto trim the elevator/flying stab for zero pitching moment at each op point?
If I wanted that same moment number for 4G just multiply by 4 or do I just redo the anaylysis with all the weights at 4X?
Thanks....
If you would like to refer to this comment somewhere else in this project, copy and paste the following link:
Hi Paul,
I don't have the time to read and comment on all the variable definitions chatGPT spat out right now, but I can quickly answer your other questions:
The bending moment over the span can be plotted in the planes operating point view. It will display both the bending moment for the wing as well as the tail at the same time. You can also export the operating point with all the information.
There is no direct way to automatically trim the aircraft. What you can do instead is use the stability analysis and define the horizontal tail tilt or elevator angle as the control parameter. In that case, the analysis will calculate the zero moment angle for every control parameter and find the speed to balance the weight. Basically the other way round, matching an angle of attack and flight speed to a given elevator angle instead of finding the requried elevator angle for a given angle of attack and speed.
Unless you change something in the wing configuration for the higher load case (snap flaps or the likes) multiplying by four should give pretty much the same results as increasing the mass. Increasing the mass would obviously lead to an increase in calculated airspeed, but the differences that introduces are either not accounted for by the analysis to begin with or are within its uncertainty.
One comment about chatGPT answers, especially regarding aircraft: It often is confidently wrong. Particularly with parameters; different authors use different definitions and there are too few letters in the latin and greek alphabets to only use one letter for one parameter. Furthermore, some of the parameters depend on what reference system they are defined in.
The general parameters are mostly agreed upon, so it should get them right, but I wouldn't bet on it. These are the parameters you likely know already anyway.
Understanding is key here; if you know what you are investigating, you know what range of outputs is reasonable, and therefore can judge if the parameter is what you believe it is and also if the analysis is giving you reasonable results.
Some of the parameters are defined in the guidlines document and most of them should be familiar. If not, you most likely don't need them or they won't be of any help until you have studied that field a bit.
Cheers,
Stefan
Last edit: Stefan 2024-06-07
If you would like to refer to this comment somewhere else in this project, copy and paste the following link:
I pulled the variable's out of the graph selection dialog(s) and asked Chat GPT to give definitions and short description of why that variable matters.
If someone tha tis not as clueless as I could review for accuracy this should get added to guide/documents somewhere as looking at the history multiple people have asked for this.
Here it is in pasted text and attached as a Rich Text Document and PDF.
I can provide in any other format Word supports if that is helpful.
Aircraft Analysis Polar plot variables:
• Alpha: The angle of attack of the aircraft. Matters because it determines how the airflow interacts with the wings, influencing lift and drag forces and, consequently, the aircraft's performance and stability.
• Beta: The sideslip angle of the aircraft. Important for understanding how the aircraft responds to crosswinds and asymmetrical aerodynamic forces, affecting its stability and control.
• Cl: Lift coefficient, indicating the amount of lift generated by the aircraft's wings. Crucial for assessing the aircraft's ability to generate lift at different angles of attack and for designing efficient airfoils.
• CD: Drag coefficient, representing the resistance encountered by the aircraft as it moves through the air. Essential for evaluating the aircraft's aerodynamic efficiency and fuel consumption.
• CD_viscous: Viscous drag coefficient, representing drag due to the viscosity of the airflow around the aircraft. Important for understanding the effects of surface roughness and aerodynamic cleanliness on drag.
• CD_induced: Induced drag coefficient, caused by the generation of lift. Significant for assessing the efficiency of the aircraft's lift production and its impact on overall drag and fuel consumption.
• CY: Side force coefficient, indicating the lateral force experienced by the aircraft. Matters for assessing the aircraft's lateral stability and control, particularly during maneuvers.
• Cm: Pitching moment coefficient, representing the aircraft's tendency to pitch. Crucial for stability analysis and control system design to ensure proper pitch control during flight.
• Cm_viscous: Viscous pitching moment coefficient. Important for understanding the aerodynamic effects contributing to the aircraft's pitching moment, aiding in stability analysis and control design.
• Cm_induced: Induced pitching moment coefficient. Significant for assessing the contribution of lift-induced effects to the aircraft's pitching moment, influencing stability and control characteristics.
• Cn: Yawing moment coefficient, indicating the aircraft's tendency to yaw. Essential for assessing directional stability and control, particularly during yaw maneuvers.
• Cn_viscous: Viscous yawing moment coefficient. Important for understanding the aerodynamic effects contributing to the aircraft's yawing moment, aiding in stability analysis and control design.
• Cn_induced: Induced yawing moment coefficient. Significant for assessing the contribution of lift-induced effects to the aircraft's yawing moment, influencing stability and control characteristics.
• CL/CD: Lift-to-drag ratio, representing the efficiency of the aircraft in generating lift relative to drag. Crucial for evaluating overall aerodynamic performance and fuel efficiency.
• sqrt(Cl^3/Cd^2): Square root of the ratio of lift cubed to drag squared. Provides a measure of aerodynamic efficiency, helping to assess the balance between lift and drag for the aircraft.
• 1/Rt(CL): Inverse of the square root of the lift coefficient. Important for analyzing the effects of changes in lift coefficient on the aircraft's aerodynamic performance.
• Fx(N), Fy(N), Fz(N): Force components in the x, y, and z directions, respectively. Crucial for understanding the aerodynamic forces acting on the aircraft and for structural analysis and design.
• Vx(m/s), Vy(m/s), Vz(m/s): Velocity components in the x, y, and z directions, respectively. Essential for determining the aircraft's motion and dynamic behavior in different directions.
• V(m/s): Magnitude of velocity, indicating the speed of the aircraft through the air. Crucial for assessing performance, range, and fuel consumption.
• Gamma: Flight path angle, the angle between the velocity vector and the horizontal plane. Important for trajectory analysis and understanding the aircraft's climb or descent behavior.
• L(N.m), M(N.m), N(n.m): Moments acting on the aircraft in the x, y, and z directions, respectively. Crucial for stability analysis and control system design.
• Cpx(m), Cpy(m), Cpz(m): Aerodynamic center positions in the x, y, and z directions, respectively. Significant for stability analysis and control surface design.
• BM(N.m): Bending moment, representing the moment exerted on the aircraft structure. Essential for structural analysis and design to ensure structural integrity and performance.
• m.g.Vz(W): Weight component in the z-direction. Important for understanding the vertical forces acting on the aircraft and their effects on flight dynamics.
• Efficiency: Represents the efficiency of the aircraft in terms of aerodynamic performance, fuel consumption, or other relevant metrics. Crucial for assessing overall performance and operational costs.
• (XCp-XCG)/MAC(%): Indicates the relative position of the aerodynamic center to the center of gravity, expressed as a percentage of the mean aerodynamic chord. Important for stability analysis and control design.
• ctrl: Control variable, representing the input to control surfaces or systems. Crucial for understanding and analyzing aircraft control and maneuverability.
• XNP(m): Neutral point position, indicating the aerodynamic balance point of the aircraft. Essential for stability analysis and determining longitudinal stability characteristics.
• Phugoid Freq(Hz): Phugoid frequency, representing the frequency of longitudinal oscillations in the aircraft. Important for stability analysis and assessing longitudinal dynamic behavior.
• Phugoid Damping: Damping ratio of phugoid oscillations. Significant for stability analysis and understanding the damping characteristics of longitudinal motion.
• Short Period Freq(Hz): Frequency of short period oscillations in the aircraft. Crucial for stability analysis and assessing the dynamic response of the aircraft to pitch disturbances.
• Short Period Damping Ratio: Damping ratio of short period oscillations. Important for stability analysis and understanding the damping characteristics of pitch motion.
• Dutch Roll Freq(Hz): Frequency of Dutch roll oscillations in the aircraft. Essential for stability analysis and assessing lateral dynamic behavior.
• Dutch Roll Damping: Damping ratio of Dutch roll oscillations. Significant for stability analysis and understanding the damping characteristics of lateral motion.
• Roll Mode t2(s): Time constant for roll mode oscillations. Important for stability analysis and assessing the time response of roll motion.
• Fx.Vx.(W): Product of force component in the x-direction and velocity component in the x-direction, representing power. Crucial for understanding energy consumption or production during flight.
• Extra Drag (N): Additional drag force acting on the aircraft. Important for assessing total drag and its impact on performance and fuel consumption.
• Mass(kg): Mass of the aircraft. Essential for determining inertia properties, performance, and structural loading.
• CoG_x(m), CoG_z(m): Center of gravity position in the x and z directions, respectively. Crucial for stability analysis, control system design, and determining aircraft loading limits.
Single OP point available Variables:
• Total Angle: The overall angle of attack of the airfoil or aircraft, usually measured in degrees. It matters because it directly influences the aerodynamic forces acting on the airfoil or aircraft, such as lift and drag.
• Local Lift Coefficient: The lift coefficient at a specific point on the airfoil or aircraft, providing information about the lift generation characteristics across the surface. It matters for understanding the distribution of lift and the aerodynamic performance of the airfoil or aircraft.
• Local Lift C.CL/M.A.C: Local lift coefficient multiplied by chord length and divided by mean aerodynamic chord (M.A.C), giving the lift force per unit length along the wing or airfoil. It matters for structural analysis and load distribution considerations.
• Airfoil Viscous Drag Coefficient: The drag coefficient attributed to viscous effects on the airfoil, representing the energy dissipation due to friction between the air and the airfoil surface. It matters for assessing the total drag and overall efficiency of the airfoil.
• Induced Drag Coefficient: The drag coefficient associated with the generation of lift, primarily caused by the wingtip vortices. It matters because induced drag contributes to the total drag force experienced by the aircraft and affects its fuel efficiency.
• Total Drag Coefficient: The overall drag coefficient of the airfoil or aircraft, comprising both viscous and induced drag components. It matters as it directly influences the total drag force acting on the aircraft, affecting its performance and fuel consumption.
• Local Drag C.Cd/M.A.C: Local drag coefficient multiplied by chord length and divided by mean aerodynamic chord (M.A.C), providing the drag force per unit length along the wing or airfoil. It matters for structural analysis and drag distribution considerations.
• Airfoil Pitching Moment Coefficient: The coefficient representing the pitching moment exerted on the airfoil due to changes in angle of attack. It matters because it affects the stability and control characteristics of the aircraft.
• Total Pitching Moment Coefficient: The overall coefficient representing the total pitching moment acting on the aircraft, combining contributions from various aerodynamic surfaces. It matters for assessing the stability and controllability of the aircraft.
• Reynolds Number: A dimensionless parameter used to characterize the flow regime around the airfoil or aircraft, indicating whether the flow is laminar or turbulent. It matters because it influences the aerodynamic behavior and performance of the airfoil or aircraft.
• Top Transition x-pos% and Bottom Transition x-pos%: The positions along the airfoil chord where the flow transitions from laminar to turbulent, expressed as a percentage of the chord length. It matters for understanding boundary layer behavior and drag prediction.
• Center of Pressure x-pos%: The location along the airfoil chord where the resultant aerodynamic force (lift and drag) acts, expressed as a percentage of the chord length. It matters for stability analysis and control surface design.
• Bending Moment: The moment exerted on the airfoil or aircraft structure, causing bending deformation. It matters for structural analysis and design to ensure structural integrity and performance.
• Cl/Cd: The lift-to-drag ratio, indicating the efficiency of the airfoil or aircraft in generating lift relative to drag. It matters because it provides insight into the aerodynamic performance and efficiency of the aircraft.
• sqrt(Cl^3/Cd^2): Square root of the ratio of lift cubed to drag squared, providing a measure of aerodynamic efficiency. It matters because it offers a concise representation of the balance between lift and drag for the airfoil or aircraft.
Very cool program...
One more question when I'm looking at a graph the mouse cursor turns to crosshair...
Is there any want to read numeric values of the plot under the cross hair?
Also the graphs cut off the axis name and units?
If you would like to refer to this comment somewhere else in this project, copy and paste the following link:
Display works fiune with numbers on one my big computer, no numbers or graph labels at all on the laptop. Both running same version. Will try messing with the margin numbers.
If you would like to refer to this comment somewhere else in this project, copy and paste the following link:
There are a lot of variable names in the aircraft polar plots.
IS there a list or reference somewhere? I only recognize 20% of them.
Specific plot i want is:
If I have a working aircraft simulation and I want to see the spar bending moment by station from root to tip, what variables would I plot?
Same question for elevator?
is there any way to auto trim the elevator/flying stab for zero pitching moment at each op point?
If I wanted that same moment number for 4G just multiply by 4 or do I just redo the anaylysis with all the weights at 4X?
Thanks....
Hi Paul,
I don't have the time to read and comment on all the variable definitions chatGPT spat out right now, but I can quickly answer your other questions:
The bending moment over the span can be plotted in the planes operating point view. It will display both the bending moment for the wing as well as the tail at the same time. You can also export the operating point with all the information.
There is no direct way to automatically trim the aircraft. What you can do instead is use the stability analysis and define the horizontal tail tilt or elevator angle as the control parameter. In that case, the analysis will calculate the zero moment angle for every control parameter and find the speed to balance the weight. Basically the other way round, matching an angle of attack and flight speed to a given elevator angle instead of finding the requried elevator angle for a given angle of attack and speed.
Unless you change something in the wing configuration for the higher load case (snap flaps or the likes) multiplying by four should give pretty much the same results as increasing the mass. Increasing the mass would obviously lead to an increase in calculated airspeed, but the differences that introduces are either not accounted for by the analysis to begin with or are within its uncertainty.
One comment about chatGPT answers, especially regarding aircraft: It often is confidently wrong. Particularly with parameters; different authors use different definitions and there are too few letters in the latin and greek alphabets to only use one letter for one parameter. Furthermore, some of the parameters depend on what reference system they are defined in.
The general parameters are mostly agreed upon, so it should get them right, but I wouldn't bet on it. These are the parameters you likely know already anyway.
Understanding is key here; if you know what you are investigating, you know what range of outputs is reasonable, and therefore can judge if the parameter is what you believe it is and also if the analysis is giving you reasonable results.
Some of the parameters are defined in the guidlines document and most of them should be familiar. If not, you most likely don't need them or they won't be of any help until you have studied that field a bit.
Cheers,
Stefan
Last edit: Stefan 2024-06-07
I pulled the variable's out of the graph selection dialog(s) and asked Chat GPT to give definitions and short description of why that variable matters.
If someone tha tis not as clueless as I could review for accuracy this should get added to guide/documents somewhere as looking at the history multiple people have asked for this.
Here it is in pasted text and attached as a Rich Text Document and PDF.
I can provide in any other format Word supports if that is helpful.
Aircraft Analysis Polar plot variables:
• Alpha: The angle of attack of the aircraft. Matters because it determines how the airflow interacts with the wings, influencing lift and drag forces and, consequently, the aircraft's performance and stability.
• Beta: The sideslip angle of the aircraft. Important for understanding how the aircraft responds to crosswinds and asymmetrical aerodynamic forces, affecting its stability and control.
• Cl: Lift coefficient, indicating the amount of lift generated by the aircraft's wings. Crucial for assessing the aircraft's ability to generate lift at different angles of attack and for designing efficient airfoils.
• CD: Drag coefficient, representing the resistance encountered by the aircraft as it moves through the air. Essential for evaluating the aircraft's aerodynamic efficiency and fuel consumption.
• CD_viscous: Viscous drag coefficient, representing drag due to the viscosity of the airflow around the aircraft. Important for understanding the effects of surface roughness and aerodynamic cleanliness on drag.
• CD_induced: Induced drag coefficient, caused by the generation of lift. Significant for assessing the efficiency of the aircraft's lift production and its impact on overall drag and fuel consumption.
• CY: Side force coefficient, indicating the lateral force experienced by the aircraft. Matters for assessing the aircraft's lateral stability and control, particularly during maneuvers.
• Cm: Pitching moment coefficient, representing the aircraft's tendency to pitch. Crucial for stability analysis and control system design to ensure proper pitch control during flight.
• Cm_viscous: Viscous pitching moment coefficient. Important for understanding the aerodynamic effects contributing to the aircraft's pitching moment, aiding in stability analysis and control design.
• Cm_induced: Induced pitching moment coefficient. Significant for assessing the contribution of lift-induced effects to the aircraft's pitching moment, influencing stability and control characteristics.
• Cn: Yawing moment coefficient, indicating the aircraft's tendency to yaw. Essential for assessing directional stability and control, particularly during yaw maneuvers.
• Cn_viscous: Viscous yawing moment coefficient. Important for understanding the aerodynamic effects contributing to the aircraft's yawing moment, aiding in stability analysis and control design.
• Cn_induced: Induced yawing moment coefficient. Significant for assessing the contribution of lift-induced effects to the aircraft's yawing moment, influencing stability and control characteristics.
• CL/CD: Lift-to-drag ratio, representing the efficiency of the aircraft in generating lift relative to drag. Crucial for evaluating overall aerodynamic performance and fuel efficiency.
• sqrt(Cl^3/Cd^2): Square root of the ratio of lift cubed to drag squared. Provides a measure of aerodynamic efficiency, helping to assess the balance between lift and drag for the aircraft.
• 1/Rt(CL): Inverse of the square root of the lift coefficient. Important for analyzing the effects of changes in lift coefficient on the aircraft's aerodynamic performance.
• Fx(N), Fy(N), Fz(N): Force components in the x, y, and z directions, respectively. Crucial for understanding the aerodynamic forces acting on the aircraft and for structural analysis and design.
• Vx(m/s), Vy(m/s), Vz(m/s): Velocity components in the x, y, and z directions, respectively. Essential for determining the aircraft's motion and dynamic behavior in different directions.
• V(m/s): Magnitude of velocity, indicating the speed of the aircraft through the air. Crucial for assessing performance, range, and fuel consumption.
• Gamma: Flight path angle, the angle between the velocity vector and the horizontal plane. Important for trajectory analysis and understanding the aircraft's climb or descent behavior.
• L(N.m), M(N.m), N(n.m): Moments acting on the aircraft in the x, y, and z directions, respectively. Crucial for stability analysis and control system design.
• Cpx(m), Cpy(m), Cpz(m): Aerodynamic center positions in the x, y, and z directions, respectively. Significant for stability analysis and control surface design.
• BM(N.m): Bending moment, representing the moment exerted on the aircraft structure. Essential for structural analysis and design to ensure structural integrity and performance.
• m.g.Vz(W): Weight component in the z-direction. Important for understanding the vertical forces acting on the aircraft and their effects on flight dynamics.
• Efficiency: Represents the efficiency of the aircraft in terms of aerodynamic performance, fuel consumption, or other relevant metrics. Crucial for assessing overall performance and operational costs.
• (XCp-XCG)/MAC(%): Indicates the relative position of the aerodynamic center to the center of gravity, expressed as a percentage of the mean aerodynamic chord. Important for stability analysis and control design.
• ctrl: Control variable, representing the input to control surfaces or systems. Crucial for understanding and analyzing aircraft control and maneuverability.
• XNP(m): Neutral point position, indicating the aerodynamic balance point of the aircraft. Essential for stability analysis and determining longitudinal stability characteristics.
• Phugoid Freq(Hz): Phugoid frequency, representing the frequency of longitudinal oscillations in the aircraft. Important for stability analysis and assessing longitudinal dynamic behavior.
• Phugoid Damping: Damping ratio of phugoid oscillations. Significant for stability analysis and understanding the damping characteristics of longitudinal motion.
• Short Period Freq(Hz): Frequency of short period oscillations in the aircraft. Crucial for stability analysis and assessing the dynamic response of the aircraft to pitch disturbances.
• Short Period Damping Ratio: Damping ratio of short period oscillations. Important for stability analysis and understanding the damping characteristics of pitch motion.
• Dutch Roll Freq(Hz): Frequency of Dutch roll oscillations in the aircraft. Essential for stability analysis and assessing lateral dynamic behavior.
• Dutch Roll Damping: Damping ratio of Dutch roll oscillations. Significant for stability analysis and understanding the damping characteristics of lateral motion.
• Roll Mode t2(s): Time constant for roll mode oscillations. Important for stability analysis and assessing the time response of roll motion.
• Fx.Vx.(W): Product of force component in the x-direction and velocity component in the x-direction, representing power. Crucial for understanding energy consumption or production during flight.
• Extra Drag (N): Additional drag force acting on the aircraft. Important for assessing total drag and its impact on performance and fuel consumption.
• Mass(kg): Mass of the aircraft. Essential for determining inertia properties, performance, and structural loading.
• CoG_x(m), CoG_z(m): Center of gravity position in the x and z directions, respectively. Crucial for stability analysis, control system design, and determining aircraft loading limits.
Single OP point available Variables:
• Total Angle: The overall angle of attack of the airfoil or aircraft, usually measured in degrees. It matters because it directly influences the aerodynamic forces acting on the airfoil or aircraft, such as lift and drag.
• Local Lift Coefficient: The lift coefficient at a specific point on the airfoil or aircraft, providing information about the lift generation characteristics across the surface. It matters for understanding the distribution of lift and the aerodynamic performance of the airfoil or aircraft.
• Local Lift C.CL/M.A.C: Local lift coefficient multiplied by chord length and divided by mean aerodynamic chord (M.A.C), giving the lift force per unit length along the wing or airfoil. It matters for structural analysis and load distribution considerations.
• Airfoil Viscous Drag Coefficient: The drag coefficient attributed to viscous effects on the airfoil, representing the energy dissipation due to friction between the air and the airfoil surface. It matters for assessing the total drag and overall efficiency of the airfoil.
• Induced Drag Coefficient: The drag coefficient associated with the generation of lift, primarily caused by the wingtip vortices. It matters because induced drag contributes to the total drag force experienced by the aircraft and affects its fuel efficiency.
• Total Drag Coefficient: The overall drag coefficient of the airfoil or aircraft, comprising both viscous and induced drag components. It matters as it directly influences the total drag force acting on the aircraft, affecting its performance and fuel consumption.
• Local Drag C.Cd/M.A.C: Local drag coefficient multiplied by chord length and divided by mean aerodynamic chord (M.A.C), providing the drag force per unit length along the wing or airfoil. It matters for structural analysis and drag distribution considerations.
• Airfoil Pitching Moment Coefficient: The coefficient representing the pitching moment exerted on the airfoil due to changes in angle of attack. It matters because it affects the stability and control characteristics of the aircraft.
• Total Pitching Moment Coefficient: The overall coefficient representing the total pitching moment acting on the aircraft, combining contributions from various aerodynamic surfaces. It matters for assessing the stability and controllability of the aircraft.
• Reynolds Number: A dimensionless parameter used to characterize the flow regime around the airfoil or aircraft, indicating whether the flow is laminar or turbulent. It matters because it influences the aerodynamic behavior and performance of the airfoil or aircraft.
• Top Transition x-pos% and Bottom Transition x-pos%: The positions along the airfoil chord where the flow transitions from laminar to turbulent, expressed as a percentage of the chord length. It matters for understanding boundary layer behavior and drag prediction.
• Center of Pressure x-pos%: The location along the airfoil chord where the resultant aerodynamic force (lift and drag) acts, expressed as a percentage of the chord length. It matters for stability analysis and control surface design.
• Bending Moment: The moment exerted on the airfoil or aircraft structure, causing bending deformation. It matters for structural analysis and design to ensure structural integrity and performance.
• Cl/Cd: The lift-to-drag ratio, indicating the efficiency of the airfoil or aircraft in generating lift relative to drag. It matters because it provides insight into the aerodynamic performance and efficiency of the aircraft.
• sqrt(Cl^3/Cd^2): Square root of the ratio of lift cubed to drag squared, providing a measure of aerodynamic efficiency. It matters because it offers a concise representation of the balance between lift and drag for the airfoil or aircraft.
Where can I find the guidlines document?
https://sourceforge.net/projects/xflr5/files/
This may help too
https://sourceforge.net/p/xflr5/code/HEAD/tree/trunk/xflr5/doc/Abbreviations-en-fr-de.odt
Very cool program...
One more question when I'm looking at a graph the mouse cursor turns to crosshair...
Is there any want to read numeric values of the plot under the cross hair?
Also the graphs cut off the axis name and units?
André
Display works fiune with numbers on one my big computer, no numbers or graph labels at all on the laptop. Both running same version. Will try messing with the margin numbers.