P6DOF Aerodynamics Data¶
Aerodynamics data is composed of two distinct categories – aero_data and aero_component blocks. The aero_data block includes the aerodynamics produced by the object without any controls input or effects from any movable surfaces/components. There is only one aero_data block, although it may contain additional aero_data blocks within it that serve as aero sub-modes. An object usually contains multiple aero_component blocks, with one of more for each axis of control and/or for each control surface, depending on the level of detail for the model.
Each of these command blocks are detailed below.
Core Aerodynamics Data (Non-Controls Data)¶
This block defines the primary aerodynamics for the vehicle. The data includes one or more geometric parameters as well as multiple stability derivative tables. See P6DOF Theory for information on how this data is used. In addition, this block includes support for “aero modes”, which allow a vehicle to have discrete aerodynamic modes, such as a retarded-fall bomb that has two aero modes – clean and high-drag.
- aero_data … end_aero_data¶
The geometric data offers two modes: wing-based or reference area. When using wing-based mode, the wing_chord_ft, wing_span_ft, and wing_area_sqft should be specified. When using reference area mode, the ref_area_sqft should be specified. The stability derivative tables are each a function of mach and alpha (angle-of-attack) or mach and beta (angle-of-sideslip), as appropriate. The tables focus on the base, non-controls aerodynamics of the vehicle. The secondary aerodynamics consist of control surface aerodynamics and are defined using aero_component, which is completely separate from aero_data.
aero_data wing_chord_ft ... wing_span_ft ... wing_area_sqft ... ref_area_sqft ... use_legacy_derivatives ... use_reduced_frequency ... aero_center_x ... aero_center_y ... aero_center_z ... cL_alpha_mach_table ... cL_alpha_beta_mach_table ... cLq_alpha_mach_table ... cL_alphadot_alpha_mach_table ... cd_alpha_mach_table ... cd_beta_mach_table ... cd_alpha_beta_mach_table ... cy_beta_mach_table ... cy_alpha_beta_mach_table ... cyr_beta_mach_table ... cy_betadot_beta_mach_table ... cm_alpha_mach_table ... cm_alpha_beta_mach_table ... cmq_mach_table ... cmp_mach_table ... cm_alphadot_mach_table ... cn_beta_mach_table ... cn_alpha_beta_mach_table ... cn_betadot_mach_table ... cnr_mach_table ... cnp_mach_table ... cl_beta_mach_table ... cl_alpha_beta_mach_table ... clp_mach_table ... cl_alphadot_mach_table ... cl_betadot_mach_table ... clr_mach_table ... clq_mach_table ... aero_mode ... end_aero_mode end_aero_data
- wing_chord_ft <real-value>¶
The mean chord of the wing measured in feet. This should be used along with wing_span_ft and wing_area_sqft.
- wing_span_ft <real-value>¶
The wing span of the wing measured in feet. This should be used along with wing_chord_ft and wing_area_sqft.
- wing_area_sqft <real-value>¶
The area of the wing measured in square feet. This should be used along with wing_chord_ft and wing_span_ft.
- ref_area_sqft <real-value>¶
The aerodynamic reference area of the vehicle measured in square feet. If this is used, wing_chord_ft, wing_span_ft and wing_area_sqft should not be used.
- use_legacy_derivatives <boolean-value>¶
This should be true when using the “legacy” stability derivatives (which are DEPRECATED and should not be used in any new development).
Default: false
- use_reduced_frequency <boolean-value>¶
This should be true when using the “reduced frequency” stability derivatives. If false, the rate derivatives (e.g. cLq_alpha_mach_table, cnr_mach_table) will be multiplied by their corresponding angular rates. If true, the rate derivatives will instead be multiplied by a non-dimensional reduced frequency. For pitching moment and lift coefficient derivatives, the reduced frequency is calculated as the angular rate times the wing_chord_ft divided by twice the speed. All other coefficient derivatives use wing_span_ft instead of chord. See P6DOF Theory for more information.
Default: true
- aero_center_x <length-value>¶
The aerodynamic center (x-axis) of the vehicle relative to the reference point in object coordinates. This “aero-center” is the “aerodynamic reference point” at which aerodynamic forces and moments will be calculated. The typical definition of aerodynamic center (as it relates to longitudinal stability) is the location at which the moment does not change regardless of the angle of attack. Thus, the pitching moment remains constant at that particular point. Hence, the aerodynamic center, rather than the center of pressure, is used in the analysis of longitudinal stability.
- aero_center_y <length-value>¶
The aerodynamic center (y-axis) of the vehicle relative to the reference point in object coordinates.
- aero_center_z <length-value>¶
The aerodynamic center (z-axis) of the vehicle relative to the reference point in object coordinates.
Lift Derivatives¶
- cL_alpha_mach_table¶
This is a 2-dimensional regular_table that outputs the lift coefficient (cL) based on the Mach and angle of attack (alpha), with a table order of Mach-alpha-value. This derivative may only be used when use_legacy_derivatives is true.
Warning
This derivative is DEPRECATED and should not be used for any new development.
Sample 2-dimensional table:
sample_cL_alpha_mach_table regular_table independent_variable mach precision float 0.000 0.900 1.2 end_independent_variable independent_variable alpha units deg 0.0 18.0 20.0 end_independent_variable dependent_variable precision float 0.0 1.2 1.3 0.0 1.2 1.3 0.0 1.2 1.3 end_dependent_variable end_regular_table end_sample_cL_alpha_mach_table
- cL_alpha_beta_mach_table¶
This is a 3-dimensional regular_table that outputs the lift coefficient (cL) based on Mach, angle of attack (alpha), and angle of sideslip (beta), with a table order of Mach-alpha-beta-value. This derivative may only be used when use_legacy_derivatives is false.
- cLq_alpha_mach_table¶
This is a 3-dimensional regular_table that outputs the lift coefficient (cL) based on Mach, angle of attack (alpha), and pitch rate (q), with a table order of Mach-alpha-q-value. This derivative may only be used when use_legacy_derivatives is false.
- cL_alphadot_alpha_mach_table¶
This is a 3-dimensional regular_table that outputs the lift coefficient (cL) based on Mach, angle of attack (alpha), and alpha-dot (the rate of change of alpha), with a table order of Mach-alpha-alphaDot-value. This derivative may only be used when use_legacy_derivatives is false.
Drag Derivatives¶
- cd_alpha_mach_table¶
This is a 2-dimensional regular_table that outputs the drag coefficient (cd) based on the Mach and angle of attack (alpha), with a table order of Mach-alpha-value. This derivative may only be used when use_legacy_derivatives is true.
Warning
This derivative is DEPRECATED and should not be used for any new development.
- cd_beta_mach_table¶
This is a 2-dimensional regular_table that outputs the drag coefficient (cd) based on the Mach and angle of sideslip (beta), with a table order of Mach-beta-value. This derivative may only be used when use_legacy_derivatives is true.
Warning
This derivative is DEPRECATED and should not be used for any new development.
- cd_alpha_beta_mach_table¶
This is a 3-dimensional regular_table that outputs the drag coefficient (cd) based on the Mach, angle of attack (alpha), and angle of sideslip (beta), with a table order of Mach-alpha-beta-value. This derivative may only be used when use_legacy_derivatives is false.
Side-Force Derivatives¶
- cy_beta_mach_table¶
This is a 2-dimensional regular_table that outputs the side force coefficient (cy) based on the Mach and angle of sideslip (beta), with a table order of Mach-beta-value.
Warning
This derivative is DEPRECATED and should not be used for any new development.
- cy_alpha_beta_mach_table¶
This is a 3-dimensional regular_table that outputs the side force coefficient (cy) based on the Mach, angle of attack (alpha), and angle of sideslip (beta), with a table order of Mach-alpha-beta-value. This derivative may only be used when use_legacy_derivatives is false.
- cyr_beta_mach_table¶
This is a 3-dimensional regular_table that outputs the side force coefficient (cy) based on the Mach, angle of sideslip (beta), and yaw rate (q), with a table order of Mach-beta-q-value. This derivative may only be used when use_legacy_derivatives is false.
- cy_betadot_beta_mach_table¶
This is a 3-dimensional regular_table that outputs the side force coefficient (cy) based on the Mach, angle of sideslip (beta), and rate of change of sideslip (beta-dot), with a table order of Mach-beta-betaDot-value. This derivative may only be used when use_legacy_derivatives is false.
Pitching Moment Derivatives¶
- cm_alpha_mach_table¶
This is a 2-dimensional regular_table that outputs the pitch coefficient (cm) based on the Mach and angle of attack (alpha), with a table order of Mach-alpha-value. This derivative may only be used when use_legacy_derivatives is true.
Warning
This derivative is DEPRECATED and should not be used for any new development.
- cm_alpha_beta_mach_table¶
This is a 3-dimensional regular_table that outputs the pitch coefficient (cm) based on the Mach, angle of attack (alpha), and angle of sideslip (beta), with a table order of Mach-alpha-beta-value. This derivative may only be used when use_legacy_derivatives is false.
- cmq_mach_table¶
This is a simple table that outputs the pitch damping coefficient due to pitch rate (cmq) based on Mach. When use_legacy_derivatives is true, the value will be multiplied by the pitch rate in deg/sec, while when use_legacy_derivatives is false (new derivatives are being used), the value will be multiplied by the pitch rate in rad/sec.
- cmp_mach_table¶
This is a simple table that outputs the pitch damping coefficient due to roll rate (cmp) based on Mach. This derivative may only be used when use_legacy_derivatives is false.
- cm_alphadot_mach_table¶
This is a 2-dimensional regular_table that outputs the pitch (damping) coefficient (cm) based on the Mach and the rate of change of alpha (alpha-dot), with a table order of Mach-alphaDot-value. This derivative may only be used when use_legacy_derivatives is false.
Yawing Moment Derivatives¶
- cn_beta_mach_table¶
This is a 2-dimensional regular_table that outputs the yaw coefficient (cn) based on the Mach and angle of sideslip (beta), with a table order of Mach-beta-value. This derivative may only be used when use_legacy_derivatives is true.
Warning
This derivative is DEPRECATED and should not be used for any new development.
- cn_alpha_beta_mach_table¶
This is a 3-dimensional regular_table that outputs the yaw coefficient (cn) based on the Mach, angle of attack (alpha), and angle of sideslip (beta), with a table order of Mach-alpha-beta-value. This derivative may only be used when use_legacy_derivatives is false.
- cn_betadot_mach_table¶
This is a 2-dimensional regular_table that outputs the yaw coefficient (cn) based on the Mach and rate of change of sideslip angle (beta-dot), with a table order of Mach-betaDot-value. This derivative may only be used when use_legacy_derivatives is false.
- cnr_mach_table¶
This is a simple table that outputs the yaw damping coefficient due to yaw rate (cnr) based on Mach. When use_legacy_derivatives is true, the value will be multiplied by the yaw rate in deg/sec, while when use_legacy_derivatives is false (new derivatives are being used), the value will be multiplied by the yaw rate in rad/sec.
- cnp_mach_table¶
This is a simple table that outputs the yaw damping coefficient due to roll rate (cnp) based on Mach. When use_legacy_derivatives is true, the value will be multiplied by the roll rate in deg/sec, while when use_legacy_derivatives is false (new derivatives are being used), the value will be multiplied by the roll rate in rad/sec.
Rolling Moment Derivatives¶
- cl_beta_mach_table¶
This is a 2-dimensional regular_table that outputs the roll coefficient (cl) based on the Mach and angle of sideslip (beta), with a table order of Mach-beta-value. This derivative may only be used when use_legacy_derivatives is true.
Warning
This derivative is DEPRECATED and should not be used for any new development.
- cl_alpha_beta_mach_table¶
This is a 3-dimensional regular_table that outputs the roll coefficient (cl) based on the Mach, angle of attack (alpha), and angle of sideslip (beta), with a table order of Mach-alpha-beta-value. This derivative may only be used when use_legacy_derivatives is false.
- clp_mach_table¶
This is a simple table that outputs the roll damping coefficient due to roll rate (clp) based on Mach. When use_legacy_derivatives is true, the value will be multiplied by the roll rate in deg/sec, while when use_legacy_derivatives is false (new derivatives are being used), the value will be multiplied by the roll rate in rad/sec.
- cl_alphadot_mach_table¶
This is a 2-dimensional regular_table that outputs the roll coefficient (cl) based on the Mach and the rate of change of angle of attack (alpha), with a table order of Mach-alphaDot-value. This derivative may only be used when use_legacy_derivatives is false.
- cl_betadot_mach_table¶
This is a 2-dimensional regular_table that outputs the roll coefficient (cl) based on the Mach and the rate of change of angle of sideslip (beta), with a table order of Mach-betaDot-value. This derivative may only be used when use_legacy_derivatives is false.
- clr_mach_table¶
This is a simple table that outputs the roll damping coefficient due to yaw rate (clr) based on Mach. When use_legacy_derivatives is true, the value will be multiplied by the yaw rate in deg/sec, while when use_legacy_derivatives is false (new derivatives are being used), the value will be multiplied by the yaw rate in rad/sec.
- clq_mach_table¶
This is a simple table that outputs the roll damping coefficient due to pitch rate (clq) based on Mach. This derivative may only be used when use_legacy_derivatives is false.
Aero Modes¶
- aero_mode <string> … end_aero_mode¶
Aero modes may be defined to allow a vehicle to have discrete aerodynamic modes, such as a retarded-fall bomb that has two aero modes – clean and high-drag. Aero modes support all commands that aero data support with the exception of an aero_mode (aero_modes can not be nested within each other). Each aero mode name must be unique for that object. Aero modes are typically changed using sequencers and the action_change_aero_mode.
If use_reduced_frequency or use_legacy_derivatives are not explicitly set within an aero_mode block, those undefined settings will be set from the settings defined (or left as defaults) by the parent aero_data block.
aero_mode <string> wing_chord_ft ... wing_span_ft ... wing_area_sqft ... ref_area_sqft ... use_legacy_derivatives ... use_reduced_frequency ... aero_center_x ... aero_center_y ... aero_center_z ... cL_alpha_mach_table ... cL_alpha_beta_mach_table ... cLq_alpha_mach_table ... cL_alphadot_alpha_mach_table ... cd_alpha_mach_table ... cd_beta_mach_table ... cd_alpha_beta_mach_table ... cy_beta_mach_table ... cy_alpha_beta_mach_table ... cyr_beta_mach_table ... cy_betadot_beta_mach_table ... cm_alpha_mach_table ... cm_alpha_beta_mach_table ... cmq_mach_table ... cmp_mach_table ... cm_alphadot_mach_table ... cn_beta_mach_table ... cn_alpha_beta_mach_table ... cn_betadot_mach_table ... cnr_mach_table ... cnp_mach_table ... cl_beta_mach_table ... cl_alpha_beta_mach_table ... clp_mach_table ... cl_alphadot_mach_table ... cl_betadot_mach_table ... clr_mach_table ... clq_mach_table ... end_aero_mode
Movable Aerodynamics Data (Control Surface Aero)¶
Secondary aerodynamics include aerodynamic effects produced by control surfaces or other components, such as landing gear, that produce aero effects as a function of angle. For example, retractable landing gear produce significant drag when extended (angle of 90 deg) and no drag when retracted (angle of 0 deg).
- aero_component … end_aero_component¶
The use of aero components can be simple, such as having three “generic” yaw, pitch and roll aero components, or can be more complex and realistic, such as having sixteen specific components: LeftAileron, RightAileron, LeftStabilator, RightStabilator, LeftRudder, RightRudder, LeftSpeedbrake, RightSpeedbrake, LeftFlap, RightFlap, LeftSpoiler, RightSpoiler, NoseLandingGear, LeftLandingGear, RightLandingGear, and ArrestingHook. During runtime, the position of aero components is controlled by the P6DOF Flight Control System Definition.
aero_component type ... ref_area_sqft ... use_legacy_derivatives ... use_reduced_frequency ... cL_angle_alpha_mach_table ... cd_angle_alpha_mach_table ... cd_angle_beta_mach_table ... cd_angle_mach_table ... cy_angle_beta_mach_table ... cm_angle_alpha_mach_table ... cmq_angle_mach_table ... cn_angle_beta_mach_table ... cnr_angle_mach_table ... cl_angle_mach_table ... cl_angle_alpha_beta_table ... clp_angle_mach_table ... clq_angle_mach_table ... clr_angle_mach_table ... cLFactor_angle_mach_table ... end_aero_component
- type <string>¶
This sets the name/type of the aero component. The name must be unique within the set of aero components for the given p6dof_object_type.
Warning
In order for an aero_component to operate, it must be “connected” to flight_controls via the control_surface command in flight_controls.
The control_surface name and the aero_component type must match exactly and are case-sensitive.
- ref_area_sqft <area-value>¶
This is the reference aerodynamic area for the aero component. If this is not specified, the wing_area_sqft defined in aero_data is used.
- cL_angle_alpha_mach_table¶
This is a 3-dimensional regular_table that outputs the lift coefficient (cL) based on the Mach, angle of attack (alpha), and control surface angle, with a table order of Mach-alpha-angle-value. Sample 3-dimensional table:
sample_cL_angle_alpha_mach_table regular_table independent_variable mach precision float 0.000 0.900 1.2 end_independent_variable independent_variable alpha units deg 0.0 18.0 20.0 end_independent_variable independent_variable angle units deg -10.0 0.0 10.0 end_independent_variable dependent_variable precision float -1.0 0.0 1.0 -1.0 0.0 1.0 -1.0 0.0 1.0 -1.0 0.0 1.0 -1.0 0.0 1.0 -1.0 0.0 1.0 -1.0 0.0 1.0 -1.0 0.0 1.0 -1.0 0.0 1.0 end_dependent_variable end_regular_table end_sample_cL_angle_alpha_mach_table
- cd_angle_alpha_mach_table¶
This is a 3-dimensional regular_table that outputs the drag coefficient (cd) based on the Mach, angle of attack (alpha), and angle of the control surface, with a table order of Mach-alpha-angle-value. This derivative should be used when drag is only a function of alpha (not beta). When this derivative is used, cd_angle_beta_mach_table and cd_angle_mach_table should not be used.
- cd_angle_beta_mach_table¶
This is a 3-dimensional regular_table that outputs the drag coefficient (cd) based on the Mach, angle of sideslip (beta), and angle of the control surface, with a table order of Mach-beta-angle-value. This derivative should be used when drag is only a function of beta (not alpha). When this derivative is used, cd_angle_alpha_mach_table and cd_angle_mach_table should not be used.
- cd_angle_mach_table¶
This is a 2-dimensional regular_table that outputs the drag coefficient (cd) based on the Mach and the angle of the control surface, with a table order of Mach-angle-value. This derivative should be used when drag is a function of both alpha and beta. (Although this function does not include either alpha or beta, it is more appropriate than either the pro-alpha or pro-beta derivatives.) When this derivative is used, cd_angle_alpha_mach_table and cd_angle_beta_mach_table should not be used.
- cy_angle_beta_mach_table¶
This is a 3-dimensional regular_table that outputs the side force coefficient (cy) based on the Mach, angle of sideslip (beta), and angle of the control surface, with a table order of Mach-beta-angle-value..
- cm_angle_alpha_mach_table¶
This is a 3-dimensional regular_table that outputs the pitch coefficient (cm) based on the Mach, angle of attack (alpha), and angle of the control surface, with a table order of Mach-alpha-angle-value.
- cmq_angle_mach_table¶
This is a 2-dimensional regular_table that outputs the pitch damping coefficient due to pitch rate (cmq) based on Mach and the angle of the control surface.
- cn_angle_beta_mach_table¶
This is a 3-dimensional regular_table that outputs the yaw coefficient (cn) based on the Mach, angle of sideslip (beta), and angle of the control surface, with a table order of Mach-beta-angle-value.
- cnr_angle_mach_table¶
This is a 2-dimensional regular_table that outputs the yaw damping coefficient due to yaw rate (cnr) based on Mach and the angle of the control surface.
- cl_angle_mach_table¶
This is a 2-dimensional regular_table that outputs the roll coefficient (cl) based on the Mach and angle of the control surface, with a table order of Mach-angle-value.
Warning
This derivative is DEPRECATED and should not be used for any new development.
- cl_angle_alpha_beta_table¶
This is a 3-dimensional regular_table that outputs the roll coefficient (cl) based on the angle of the attack (alpha), the angle of slideslip (beta) and the angle of the control surface, with a table order of alpha-beta-angle-value. This derivative may only be used when use_legacy_derivatives is false.
- clp_angle_mach_table¶
This is a 2-dimensional regular_table that outputs the roll damping coefficient due to roll rate (clp) based on Mach and the angle of the control surface.
- clq_angle_mach_table¶
This is a 2-dimensional regular_table that outputs the roll damping coefficient due to pitch rate (clq) based on Mach and the angle of the control surface.
- clr_angle_mach_table¶
This is a 2-dimensional regular_table that outputs the roll damping coefficient due to yaw rate (clr) based on Mach and the angle of the control surface.
- cLFactor_angle_mach_table¶
This is a 2-dimensional regular_table that outputs the lift factor based on the Mach and angle of the control surface, with a table order of Mach-angle-value. The lift factor is multiplied by the calculated lift. It is used for lift reducing components such as spoilers. This is DEPRECATED and should not be used in new developments.
Warning
This derivative is DEPRECATED and should not be used for any new development.
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