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Chapter 5
Solution Procedures
The NDARC code performs design and analysis tasks. The design task involves sizing the rotorcraft
to satisfy specified design conditions and missions. The analysis tasks can include off-design mission
performance analysis, flight performance calculation for point operating conditions, and generation of
subsystem or component performance maps. Figure 5-1 illustrates the tasks. The principal tasks (sizing,
mission analysis, and flight performance analysis) are shown in the figure as boxes with dark borders.
Dark arrows show control of subordinate tasks.
The aircraft description (fig. 5-1) consists of all the information, input and derived, that defines
the aircraft. The aircraft consists of a set of components, including fuselage, rotors, wings, tails, and
propulsion. This information can be the result of the sizing task; can come entirely from input, for a
fixed model; or can come from the sizing task in a previous case or previous job. The aircraft description
information is available to all tasks and all solutions (indicated by light arrows).
Missions are defined for the sizing task and for the mission performance analysis. A mission consists
of a specified number of mission segments, for which time, distance, and fuel burn are evaluated. For
specified takeoff fuel weight with adjustable segments, the mission time or distance is adjusted so the
fuel required for the mission (burned plus reserve) equals the takeoff fuel weight. The mission iteration
is on fuel weight.
Flight conditions are specified for the sizing task and for the flight performance analysis.
For flight conditions and mission takeoff, the gross weight can be maximized such that the power
required equals the power available.
A flight state is defined for each mission segment and each flight condition. The aircraft performance
can be analyzed for the specified state, or a maximum-effort performance can be identified. The
maximum effort is specified in terms of a quantity such as best endurance or best range, and a variable
such as speed, rate of climb, or altitude. The aircraft must be trimmed, by solving for the controls
and motion that produce equilibrium in the specified flight state. Different trim-solution definitions are
required for various flight states. Evaluating the rotor hub forces may require solution of the blade-flap
equations of motion.
The sizing task is described in more detail in chapter 3; the flight condition, mission, and flightstate
calculations are described in chapter 4; and the solution of the blade-flap equations of motion is
described in chapter 11. The present chapter provides details of the solution procedures implemented
for each iteration of the analysis.
The nested iteration loops involved in the solution process are indicated by the subtitles in the
boxes of Figure 5-1 and illustrated in more detail in Figure 5-2. The flight-state solution involves up