This project is a proposal for the AIAA 2016-2017 Undergraduate Aircraft Design Competition. Although the project was not officially submitted to the AIAA, the final designs satisfy all requirements and regulations of the AIAA Request for Proposal. The competition calls for the design of a two business jet family that fly at Mach 0.85 and 35,000ft. The larger plane must carry 8 passengers, while the smaller must carry 6. The aircrafts have ranges of 2,500nmi and satisfy all applicable FAR 23/25 requirements. The design is multifaceted, combining aspects such as aerodynamic design, interior design, and the business model and market outlook.
Initial Design
The initial design is an interative cycle between proprietary and public tools. The initial design begins with using the "Preliminary Aircraft Sizing" toolbox. This is a growing code that allows for maximum takeoff weight, surface area, thrust, and sizing calculations. This provides necessary parameters to enter into openVSP for three-dimensional modeling and analysis. OpenVSP calculates important parameters cush as lift-to-drag ratio, aspect ratio, and coefficient of lift. These parameters interface into the initial weight and surface area calculations and being a new iteration cycle. After various iterations the design converges and the deisgn proceeds to the next step.
openVSP
The Eaglet design process depended heavily on OpenVSP and its modeling capabilities. The entire three-dimensional model of both Eaglet jets were designed and analyzed using OpenVSP's modeling toolbox and its vortex lattice solver. Initial design parameters were generated using the "Preliminary Aircraft Sizing" toolbox. These parameters build up a three-dimensional model in the OpenVSP environment. This three dimensional model is then analyzed for lift and drag. These values, generated by the vortex lattice solver are fed into the "Preliminary Aircraft Sizing" toolbox, creating an iterative design process.
Suave & AVL
The SUAVE design environment is a novel aircraft deign suite that allows for a wide range of calculations and design simulations. The final design produced in OpenVSP was re-modeled in SUAVE. This buildup includes all aspects of the plane ranging from size parameters to powerplant design. SUAVE is also linked to AVL, a software that resembles OpenVSP. SUAVE and AVL combined to performance plots for the designes, including weight and throttle plots as well as lift and drag calculations. SUAVE integration not only allowed for a centralized performance analysis database but also permitted cross-software validation, comparing OpenVSP and AVL performance parameters.
CFD
The initial aerodynmic optimization for Eaglet was on the design of the wings using Syn88, a transonic wing design code. Both the top and bottom wings were optimized for the cruise-segment of Eaglet's flight. These results were imported onto the OpenVSP model and the CFD for Eaglet was done on the 8-person design. The aircraft was exported as a shell file from OpenVSP and imported into Pointwise meshing software. In this meshing environment the aircraft was meshed in an unstructured block mesh for an inviscid solver. Pointwise conveniently generates an ANSYS Fluent case file with the mesh already imported. This case was then initialized in Fluent and run using an inviscid density-based simulation at cruising altitude.
Control Surfaces and Dynamics
Eaglet features a complex and novel box-wing configuration, giving rise to initial uncertainties regarding flight stability parameters and coefficients. The first step to understanding the stability of the aircraft was to design the control surfaces on all of the wings and systems. These surfaces were designed using calculations found in design literature. All stability coefficients were calculated for both the 8-person and 6-person variants and these coefficients were simulated using a simulation code developed by Prof. Robert Stengel and Princeton University. This analysis generated graphical control plots including bode and step response plots. The complex dynamics of the aircraft also require advanced fly-by-wire control to control necessary surfaces.
Structural Design
The Eaglet jet family requires similarity between models, but also features a complex and novel design that produces unique loads on the wings and fuselage. The computer aided design of Eaglet's structure was thorough and rigorous. The entire process was carried out in PTC CREO which allowed for both modeling and structural analysis of the system. The CREO models include all structural elements ranging from ribs to bulkheads. Simulating this complex system aided in the material selection process for the entire aircraft, informing decisions on what each component should be made of.
Interior Design
The Eaglet family is intended to be a medium-sized business jet and thus lends itself to a corporate jet interior configuration. The aircraft is designed with a closed cockpit with seating for the pilot and copilot and additional seating in the main cabin for all passengers. Both versions of the airplane include a storage compartment for baggage, a lavatory, and a kitchenette. The unique wing design of the aircraft places the exit door near the rear of the fuselage permitting more seating forwards the center and front of the airplane. The complex aerodynamic design of the fuselage for this aircraft complicates the design of the cockpit, straining the overnose and upward view angles. The cockpit was carefully designed for a overnose angle of 7 degrees and an upward view angle of 20 degrees.
Business Model and Outlook
The business model and outlook for the Eaglet jet family is a combined study of both the current jet market and the DAPCA IV model. The current jet model is based on a linear fit of current aircraft that are ordered by their total price and takeoff weight. The more thorough DACPA IV model instead more accurately determines the costs and profitability of the program by tabulating the costs of each production cost ranging from engineering design to manufacturing engineering and hours. This model suggests that the 6-person variant should be priced at $10 million and the 8-person variant should be $13 million. Although slightly higher than the current options found in the market, Eaglet boasts novel and unique features such as the box-wing that boost the efficiency and cost effectiveness for the consumer in the long-term.
Opensource
This project has been published on Github and all design and analysis files have been posted publicly. All files can be found on the Github repository found here. If there are any questions, comments, or recommendations on the design, please contact Bernardo Pacini using the "contact" form on this website.
