Course: Aircraft Design and Development
Introduction
1. Background, context, perspective, history, enabling technological advances
Aircraft programs have defined aviation eras through innovation, performance, and safety. In the late 1980’s, market demands indicated the need for a commercial aircraft with a capacity of 300 to 500 passengers. Satisfying the need of global customers necessitated the development of solutions that could be adapted to the change in customers’ requirements and requests for specific aircraft configurations, components, and features. With its first flight on June 12th, 1994, the 777 confirmed the making of an aircraft designed to meet changing market demands through cabin flexibility, range capabilities and multiple aircraft sizes (Upton, 1998). The 777 program used global customers inputs as a defining element for the aircraft. 300 global airlines employees were integrated into Design and Build Teams. The 777 program also opted for concurrent work processes as opposed to sequential work processes which ensured participation and involvement of all different teams throughout the aircraft build phases (Upton, 1998).
2. Design goals and top-level requirements
The objective of the program was to design a large twin engine aircraft with a capacity of 305 to 440 passengers. Requirements included the integration of a fly-by-wire computerized control system, a self-monitoring maintenance system, lower life-cycle maintenance costs, a landing gear system composed of six wheels, shared parts and standard features across all 777 lines and configurations, flat panel liquid crystal displays, graphite composite floor beams and folding wing tips (Battershell, 1999). Other design objectives included a minimization of overall system weight and drag, the use of weight saving composite materials, lower engines noise and emission levels, and the design of more efficient engines (Upton, 1998).
Synthesis and Analysis
3. Cost, materials, technical, and environmental constraints
The 777 Program was characterized by flexibility in a quest to build an aircraft that meets varying market demands. Constraints were generally less rigid, and engineers were able to evaluate multiple alternates design solutions and configurations. Nevertheless, one of the most significant constraint of the program was the required use of 3D CATIA Computer Aided Design (CAD) models as opposed to hard mock-ups. In fact, the 777 is the first aircraft entirely designed digitally (Dietrich et al., 2007). This parallel design approach significantly optimized cycle time and quality. Cabin flexibility, higher range capabilities and multiple aircraft sizes were required. The 777-200 has a passenger capacity of 305 to 440 passenger and a range of 5523 miles while the 777-300 has a passenger capacity of 328 to 550 passengers and a range of 6444 miles (Upton, 1998).
4. Trades made to achieve selected optimum
Performance and technical innovation were a priority of the 777 programs. Lower aircraft system weight was achieved through the use of weight saving composite materials. Drag was minimized through an extremely efficient airfoil design and the use of leading edge slats, flaps and flaperons (Rogers et al., 2001). A minimization of noise pollution and environmental pollution and an improvement of fuel efficiency were achieved through the design of a new engine: a High by-Pass turbofan with criteria such as higher by-pass ratio, increased overall pressure ratio, improved thermal efficiency and reliability of individual components. Airlines employees’ design and configuration inputs included refueling panel locations, nickel plated fuel tank wiring, translating ceiling stowage bins, cabin sizing and aft galley spacing (Upton, 1998).
Evaluation and Conclusion
5. Final design effectiveness evaluation, strengths, and weaknesses
The 777 aircraft enabled airlines to complete configuration changes within days instead of weeks. The aircraft was also optimized through the integration of multiple advanced technologies. The aircraft wingspan is approximately 200 ft. It allowed the large aircraft to achieve a higher climb rate and lower cruise speed (Upton, 1998). This in turn improved fuel efficiency. The aircraft exceeded company, customers, and market expectations by offering higher payloads and higher range to users. Passenger capacity and improved fuel efficiency lowered operational cost for customers. In fact, the aircraft’s Hi-by-Pass turbofan generated 40% more thrust, improved fuel consumption and lower noise levels. When it comes to strengths, the fly-by-wire systems provided flexibility in-flight and an additional safety factor as opposed to the sole use of mechanical systems (Sabbagh, 1996). Now, its most significant weakness is the aircraft weight. The limited use of lighter composite materials to build the 777 aircraft affected its performance characteristics and capabilities (Upton, 1998).
6. Lessons learned applicable to today.
The 777 Program opted for concurrent work processes which ensure participation and involvement of all stakeholders and different teams throughout the aircraft build phases. This allows for solving multiple program issues ahead of time and led to a significant optimization of cycle time and a minimization of development, design, and manufacturing issues (Woolsey, 1991). Design elements applicable to today’s practices include the use of 3D CAD mock-ups, flexible seating configurations, the use of weight saving composite materials, the design of fuel efficient engines with lower environmental impacts and the use of control surfaces to minimize drag and improve aircraft range, maximum speed, and cruise speed (Upton, 1998).
References
Battershell, A. L. (1999). The DoD C-17 Versus the Boeing 777. A Comparison of Acquisition
and Development. National Defense University Press Publication: Washington, DC.
Dietrich, A., Stephens, A., & Wald, I. (2007). Exploring a Boeing 777: Ray Tracing Large-Scale
CAD data. IEEE Computer Graphics and Applications, 27(6), 36-46.
doi:10.1109/MCG.2007.147
Rogers, S. E., Roth, K., Cao, H. V., Slotnick, J. P., Whitlock, M., Nash, S. M., & Baker, M. D.
(2001). Computation of Viscous Flow for a Boeing 777 Aircraft in Landing Configuration.
Journal of Aircraft, 38(6), 1060-1068. doi:10.2514/2.2873
Sabbagh, K. (1996). 21st century jet: The Making and Marketing of the Boeing 777. New York:
Scribner.
Upton, J. (1998). Boeing 777, Airliner Tech Series, Vol 2. Specialty Press and Wholesalers:
North Branch, MN.
Woolsey, J. P. (1991). 777: A Program of New Concepts. Air Transport World, 28(4), 60.
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