RCAIDE.Library.Methods.Aerodynamics.Common.Drag.asymmetry_drag

asymmetry_drag#

asymmetry_drag(state, geometry, engine_out_location=0, single_engine_thrust=0, windmilling_drag_coefficient=0.0)[source]#

Computes asymmetry drag coefficient due to engine failure and resulting trim requirements.

Parameters:

state (Data) –
Flight conditions and aerodynamic state containing:
- conditions.freestream.dynamic_pressurefloat
  Freestream dynamic pressure [Pa]
- conditions.aerodynamics.coefficients.drag.windmilling.totalfloat, optional
  Windmilling drag coefficient [unitless]
geometry (Data) –
Vehicle geometry containing:
- reference_areafloat, optional
  Reference area for drag coefficient calculation [m²]
- mass_properties.center_of_gravityarray
  Center of gravity location [m]
- networkslist
  
  List of propulsion networks containing:
  
  number_of_enginesint
  Total number of engines [unitless]
- wingslist
  
  List of wing objects containing:
  
  tagstr
  Unique identifier for the wing
  
  sreffloat
  Reference area of the wing [m²]
  
  spans.projectedfloat
  Projected span of the wing [m]
  
  aerodynamic_centerarray
  Aerodynamic center location [m]
  
  originarray
  Wing origin location [m]
  
  verticalbool
  Flag indicating if wing is vertical tail
engine_out_location (float, optional) – Lateral distance of failed engine from aircraft centerline [m]
single_engine_thrust (float, optional) – Thrust produced by remaining operational engine [N]
windmilling_drag_coefficient (float, optional) – Windmilling drag coefficient for failed engine [unitless]

Returns:

asymm_trim_drag_coefficient – Asymmetry trim drag coefficient [unitless]

Return type:

float

Notes

This function calculates the additional drag required to trim the aircraft when one engine fails, creating an asymmetric thrust condition. The calculation accounts for the drag caused by yawing moment created by the asymmetric thrust and the counteracting moment from the vertical tail.

Major Assumptions

Two-engine aircraft configuration
Vertical tail provides the primary yawing moment for trim
Linear relationship between trim drag and asymmetric thrust moment
Windmilling drag contributes to the asymmetric moment

Theory

The asymmetry drag is calculated from the trim requirement to balance the yawing moment:

\(D_{trim} = \frac{(y_{engine})^2 (T_{single} + D_{windmilling})^2}{q_{\infty} \pi (h_{vt} \cdot l_{vt})^2}\)

where:

\(y_{engine}\) is the lateral distance of the failed engine [m]
\(T_{single}\) is the thrust of the remaining engine [N]
\(D_{windmilling}\) is the windmilling drag force [N]
\(q_{\infty}\) is the freestream dynamic pressure [Pa]
\(h_{vt}\) is the vertical tail height [m]
\(l_{vt}\) is the moment arm of the vertical tail [m]

The windmilling drag force is:

\(D_{windmilling} = C_{D,windmilling} \cdot q_{\infty} \cdot S_{ref}\)

The asymmetry drag coefficient is:

\(C_{D,asymmetry} = \frac{D_{trim}}{q_{\infty} \cdot S_{ref}}\)

Definitions

‘Asymmetry Drag’: Additional drag required to trim the aircraft when thrust is asymmetric due to engine failure.
‘Windmilling Drag’: Drag produced by a failed engine that continues to rotate due to incoming airflow.
‘Trim Drag’: Drag increment required to maintain aircraft equilibrium in asymmetric flight conditions.

References

[1] Unknown source