Below are excerpts from the 60 page Wichita State University Feasibility Study, which was reported on January 30, 2000. The single-engine airplane, PWCR^TM Model P, was analyzed. As pointed out earlier, the single-engine airplane illustrates the design procedure. Larger or smaller airplanes can be designed. The WSU study confirms that the Power-Wing^TM concept is a feasible approach.

CONCEPTUAL DESIGN OF A PROPULSION WING AIRCRAFT by: M. Gawad Nagati and Kamran Rokhsaz Department of Aerospace Engineering Wichita State University Wichita, KS 67260-0044

The report that follows presents the conceptual development for a 14-15 passenger Propulsion Wing Commuter aircraft. The work performed by the investigators to arrive at the proposed configuration was approached from a technical standpoint, and was based on experimental data obtained under the supervision of Mr. Kenneth Razak at the Wichita State University wind tunnel. Mr. Razak provided explanations for these test data, as well as guidance on the operational objectives of the aircraft (its reference mission) throughout the design process.

Based on these data and on the performance, and stability and control computations performed during this effort, the configuration we arrived at is believed by us to be a viable design for operations in and out of undeveloped airports. This would greatly support the Small Aircraft Transportation System envisioned by NASA.

II. TECHNICAL APPROACH

A. BACKGROUND

The blown flap, as a high lift device, has been the subject of research for several decades. References 1 through 5 represent a very small cross section of the literature available on the merits of these systems. These studies have all concluded that a properly designed blown flap, at moderate rates of blowing can generate extremely large lift coefficients.

In 1958, commissioned by the Cessna Aircraft Company, Dean Kenneth Razak undertook a study of blown flaps from a very different view point. He, and subsequently N. Akesson and W. Yates considered blown flaps as a means of uniformly dispensing herbicide, insecticide, and fertilizers in agricultural operations. Their studies, supported by wind tunnel and simulated flight tests, lead to a prototype called the "Distributor Wing Airplane". This aircraft demonstrated all of the engineering principles that its developer promoted. However, changes in the global agricultural market dissolved the configuration's economic feasibility.

Despite all of the promising aspects of blown flaps, these devices have not been employed in practical cases for a variety of reasons. However, all of these reasons can be traced back to the lack of an economic return for the design and operation of an aircraft using these systems.

In June 1999, Dean Kenneth Razak, former Dean of Engineering at Wichita State University, approached the Department of Aerospace Engineering to revive the idea of blown flaps under the new name "Propulsion Wing". The driving force behind the renewed interest in the topic was the revitalized general aviation field and the promotion of the concept of Small Aircraft Transportation System by NASA. Dean Razak believed that there would be many global markets available for a family of small aircraft that could be used for transportation among some 5000 small airports in the United States and among thousands of other small fields elsewhere in the world. The final configuration to be designed under this project was to be a single-engine 12- to 15-seat Executive Bush Plane. The aircraft was to be capable of operation from short runways, typical of those used by general aviation aircraft in this country. Also, the aircraft was to employ the concept of propulsion wing along with integrated active gust load alleviation.

B. METHOD OF ANALYSIS

1. Weights: Component weight estimates were obtained from conventional techniques used by the aircraft industry outlined in References 6 through 9. Whenever possible, several estimates were compared and the most logical numbers were adopted. These were not always the lowest estimated weights.


2. Aerodynamics: Aerodynamic data was primarily extracted from the reports provided by Dean Razak that documented the wind tunnel tests previously performed at Wichita State University. This included lift and viscous drag information. Wherever possible, data from three-dimensional tests were used. In those cases where such data was lacking, such as span loading with deflected flaps, a vortex lattice model was employed. In every case, corrections were made for the drag of appendages, such as the landing gears, the wing struts, etc.


3. Propulsion System: Fan data was obtained from Reference 10. Search of the reliable literature for more up-to-date information was not successful. Therefore, the data from Reference 10 was used with 5% increase in maximum flowrate and 5% decrease in the required power to reflect the advances in technology over the past several decades.
   
   For both engines, performance, fuel consumption, and weight data were primarily those of the manufacturer.


4. Performance: For take-off analysis, equations of motion were solved in three stages. The first stage was that of ground roll for which the lift coefficient was fixed. The second stage was that of acceleration to climb speed in level flight. The third stage was that of climb at constant speed until 50 feet above ground. Total take-off distance was defined as the sum of the three. A curve-fit of the experimental data was used for estimating the drag coefficient.


5. Stability and Control: Longitudinal stability and control information was determined from a vortex lattice computer code that modeled the wing and the tail simultaneously. The input to the code consisted of the aircraft geometry and component weights and locations. The code could then determine the location of the center of gravity and the aircraft neutral point and trim the configuration. This code clearly indicated whether the configuration was stable or not. The effect of the fuselage on longitudinal stability and control was omitted. Lateral-directional stability derivatives were estimated using methods References 12 and 13.


6. Geometric Layout: AutoCAD software was used to assist in geometric layout and to produce the required drawings.



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