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Chapter 7
Aircraft
The aircraft consists of a set of components, including rotors, wings, tails, fuselage, and propulsion.
For each component, attributes such as performance, drag, and weight can be calculated. The
aircraft attributes are obtained from the sum of the component attributes. Description and analysis of
conventional rotorcraft configurations is facilitated, while retaining the capability to model novel and advanced
concepts. Specific rotorcraft configurations considered include: single-main-rotor and tail-rotor
helicopter; tandem helicopter; and coaxial helicopter.
The following components form the aircraft:
a) Systems: The systems component contains weight information (fixed useful load, vibration, contingency,
and systems and equipment) for the aircraft.
b) Fuselage: There is one fuselage for the aircraft.
c) Landing Gear: There is one landing gear for the aircraft.
d) Rotors: The aircraft can have one or more rotors, or no rotors. In addition to main rotors, the
component can model tail rotors, propellers, proprotors, and ducted fans.
e) Forces: The force component is a simple model for a lift, propulsion, or control subsystem.
f) Wings: The aircraft can have one or more wings, or no wings.
g) Tails: The aircraft can have one or more horizontal or vertical tail surfaces, or no tails.
h) Fuel Tank: There is one fuel tank component for the aircraft. There can be one or more sizes of
auxiliary fuel tanks.
i) Propulsion Groups: There are one or more propulsion groups. Each propulsion group is a set of
components (rotors) and engine groups, connected by a drive system. The engine model describes a
particular engine, used in one or more engine groups. The components define the power required. The
engine groups define the power available.
j) Engine Groups: An engine group consists of one or more engines of a specific type. For each engine
type an engine model is defined.
7–1 Disk Loading and Wing Loading
The aircraft disk loading is the ratio of the design gross weight and a reference rotor area: DL =
WD/Aref. The reference area is a sum of specified fractions of the rotor areas, Aref = fAA (typically
the projected area of the lifting rotors). The disk loading of a rotor is the ratio of a specified fraction of