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Chapter 1
Introduction
The NASA Design and Analysis of Rotorcraft (NDARC) software is an aircraft system analysis tool
intended to support both conceptual design efforts and technology impact assessments. The principal
tasks are to design (or size) a rotorcraft to meet specified requirements, including vertical takeoff and
landing (VTOL) operation, and then analyze the performance of the aircraft for a set of conditions. For
broad and lasting utility, it is important that the code have the capability to model general rotorcraft
configurations, and estimate the performance and weights of advanced rotor concepts. The architecture
of the NDARC code accommodates configuration flexibility; a hierarchy of models; and ultimately
multidisciplinary design, analysis, and optimization. Initially the software is implemented with lowfidelity
models, typically appropriate for the conceptual design environment.
An NDARC job consists of one or more cases, each case optionally performing 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 calculation, flight performance calculation
for point operating conditions, and generation of subsystem or component performance maps. For
analysis tasks, the aircraft description can come from the sizing task, from a previous case or a previous
NDARC job, or be independently generated (typically the description of an existing aircraft).
The aircraft consists of a set of components, including fuselage, rotors, wings, tails, and propulsion.
For each component, attributes such as performance, drag, and weight can be calculated; and 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 are single main-rotor and tailrotor
helicopter; tandem helicopter; coaxial helicopter; and tiltrotors. The architecture of the code
accommodates addition of new or higher-fidelity attribute models for a component, as well as addition
of new components.
1–1 Background
The definition and development of NDARC requirements benefited substantially from the experiences
and computer codes of the preliminary design team of the U.S. Army Aeroflightdynamics
Directorate (AFDD) at NASA Ames Research Center.
In the early 1970s, the codes SSP-1 and SSP-2 were developed by the Systems Research Integration
Office (SRIO, in St. Louis) of the U.S. Army Air Mobility Research and Development Laboratory.
SSP-1 performed preliminary design to meet specified mission requirements, and SSP-2 estimated the
performance for known geometry and engine characteristics, both for single main-rotor helicopters
(ref. 1). Although similar tools were in use in the rotorcraft community, these computer programs were
independently developed, to meet the requirements of government analysis. The Advanced Systems