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54 Aircraft
the design gross weight and the rotor area:
(DL)rotor = T
A = fW WD
A
= fW
A/Aref
where probably
rotor fW =1, and the lifting rotors are all rotors not designated antitorque or auxiliarythrust.
If there are N lifting rotors of the same area, with no overlap, then fA = 1, Aref = NA,
fW = A/Aref =1/N, and (DL)rotor = DL. For rotors designated antitorque or auxiliary-thrust, the disk
loading is calculated from the design rotor thrust: (DL)rotor = Tdesign/A.
For coaxial rotors, the default reference area is the area of one rotor: fA = 1/2, Aref = A, fW = 1/2,
and (DL)rotor = 1/2DL. For tandem rotors, the default reference area is the projected area: Aref =
(2 − m)A, where mA is the overlap area (m =0for no overlap, m =1for coaxial). Then fA = 2−m
2 ,
fW = 1/2, and (DL)rotor = 2−m
2 DL. Optionally, the reference area for tandem rotors can be total rotor
area instead: Aref =2A.
The aircraft wing loading is the ratio of the design gross weight and a reference wing area: WL =
WD/Sref. The reference area is a sum of the wing areas, Sref = S. The wing loading of an individual
wing is the ratio of a specified fraction of the design gross weight and the wing area:
(WL)wing = W
S = fW WD
S
= fW
S/Sref
where probably
wing fW =1. If there are N wings of the same area, then fW = S/Sref =1/N, and
(WL)wing = WL.
7–2 Controls
A set of aircraft controls cAC are defined; they are connected to the component controls. The
connection to the component control c is typically of the form c = STcAC + c0, where T is an input
matrix and c0 the component control for zero aircraft control. The connection (matrix T )isdefined for
a specified number of control-system states (allowing change of control configuration with flight state).
The factor S is available for internal scaling of the matrix. The control state and initial control values
are specified for each flight state.
Typical (default) aircraft controls are the pilot’s controls: collective stick, lateral and longitudinal
cyclic sticks, pedal, and tilt. Units and sign convention of the pilot’s controls are contained in the matrix
T . For the single-main-rotor and tail-rotor configuration, it is often convenient for the collective and
cyclic stick motion to equal the collective and cyclic pitch input of the main rotor, and the pedal motion to
equal the collective pitch input of the tail rotor. The aircraft controls should be scaled to approximately
the same amplitude, by appropriate definition of the T matrix and scale factor S.
These aircraft controls are available for trim of the aircraft. Any aircraft controls not selected for
trim will remain fixed at the values specified for the flight state. Thus by defining additional aircraft
controls, component controls can be specified as required for a flight state.
Each aircraft control variable cAC can be zero, constant, or a function of flight speed (piecewise
linear input). The flight-state input can override this value of the aircraft control. The input value is an
initial value if the control is a trim variable.
Each component control variable c0 (value for zero aircraft control) can be zero, constant, or a
function of flight speed (piecewise linear input). The component control from aircraft control (TcAC)is
a fixed value, or a function of speed, or a linear function of another control (perhaps a trim variable).
WD
Aref
WD
Sref