Author

Julian Roche

Date of Award

12-2015

Document Type

Thesis - Open Access

Degree Name

Master of Science in Aerospace Engineering

Department

Graduate Studies

Committee Chair

Dr. J. Gordon Leishman

First Committee Member

Dr. Anastasios Lyrintzis

Second Committee Member

Dr. John Ekaterinaris

Abstract

The relative performance attributes of compound helicopter concepts have been examined, including their potential for meeting the requirements of several challenging mission profiles. For each concept, which included lift and/or propulsive compounding, a suite of aerodynamic performance models was developed using energy methods. In the case of a lift-compounded concept, an aerodynamic model representing the force interaction effects of the main rotor wake with the wing was also developed. Models of a conventional helicopter and of a tiltrotor were implemented as well, and the results used as a datum for comparison. In each case, the predictive capabilities of the model were validated using flight test data. The comparisons were conducted on the basis of equal aircraft gross weight and also on the basis of equal useful load. The performance of each rotorcraft was then assessed in terms of key attributes, including maximum attainable airspeed, flight efficiency (lift-to-drag ratio), along with the anticipated flight range and endurance. Parametric studies on the compound helicopter concepts were conducted to explore the relative advantages of adding a wing (including the effects of span and aspect ratio) and of the propulsive system (i.e., thrust augmentation). In general, it was found that a pure lift compounded helicopter concept did not offer improvements in capabilities over a conventional helicopter. However, both lift and propulsive compounding used together were shown to significantly improve the flight capabilities over a conventional helicopter, to a degree that the resulting performance was almost as good as a tiltrotor in terms of maximum airspeed and flight efficiency. Finally, some other relative merits of compound helicopters are discussed, including estimates of capital and operating costs.

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