An Analytical Assessment of NASA's N+1 Subsonic Fixed Wing Project Noise Goal

The Subsonic Fixed Wing Project of NASA's Fundamental Aeronautics Program has adopted a noise reduction goal for new, subsonic, single-aisle, civil aircraft expected to replace current 737 and A320 airplanes. These so-called 'N+1' aircraft - designated in NASA vernacular as such since they will follow the current, in-service, 'N' airplanes - are hoped to achieve certification noise goal levels of 32 cumulative EPNdB under current Stage 4 noise regulations. A notional, N+1, single-aisle, twinjet transport with ultrahigh bypass ratio turbofan engines is analyzed in this study using NASA software and methods. Several advanced noise-reduction technologies are analytically applied to the propulsion system and airframe. Certification noise levels are predicted and compared with the NASA goal

Development of A Certification Module for Early Aircraft Design

Presented at AIAA Aviation 2019 ForumThe airworthiness certification process of civil transportation aircraft is expensive, timeconsuming, and subject to uncertainty. To reduce the cost and time spent on the certification process, this paper proposes an approach to incorporate certification considerations into early design stages using virtual certification techniques. As a proof of concept, this paper focuses on flight performance certification requirements and developed a certification analysis module for aircraft conceptual and early preliminary design based on FAR-25 Subpart B. The module transforms the regulations from textual documents to quantitative constraint functions and ensures the certification constraint check of the design through physics-based analysis. To validate the module, a Small Single-aisle Aircraft testing model is developed and virtually certified by the module. The certification analysis result of the testing model is benchmarked with public domain data

Integrated Sizing and Optimization of HybridWing Body Aircraft in Conceptual Design

Presented at AIAA Aviation 2019 ForumThe hybrid wing body (HWB) configuration is a paradigm shift in commercial transport aircraft design in terms of environmentally responsible characteristics and significant performance improvements over the conventional tube-and-wing configuration. However, the sizing methods and analysis tools used in conceptual design of tube-and-wing aircraft are not fully compatible with HWB due to the highly integrated fuselage and wing. This paper proposes a novel approach to perform parametric sizing and optimization of HWB aircraft at the conceptual design phase, and develops an interdisciplinary design framework which integrates preliminary aerodynamic analysis, weight estimation, propulsion system sizing, and mission analysis. Enabled by the techniques of Design of Experiments and surrogate modeling, a design space exploration is conducted over the top-level aircraft design variables, including sensitivity assessment, feasible design space identification, and constrained multi-objective optimization. The impact of uncertainties in disciplinary analyses and novel technologies on aircraft-level performance is investigated through an uncertainty analysis

Differential Dynamic Programming to Critical-Engine-Inoperative Takeoff Certification Analysis

Presented at 2020 AIAA AVIATION ForumCritical-engine-inoperative (CEI) takeoff is a required flight test in transport aircraft type certification. Due to the limited excess power following engine failure, this flight test is potentially dangerous and highly sensitive to the flight controls. To enhance the flight safety in CEI takeoff, an optimal longitudinal control sequence is necessary for the flight test. On the other hand, to reduce the cost associated with type certification process, it is desired to incorporate certification analysis in early design phases. Since the certification regulations pose requirements on aircraft dynamic responses, the point-mass based method used in most of the takeoff analyses for aircraft early design is not suitable. To incorporate flight dynamics in takeoff analysis, a robust longitudinal control law is needed for takeoff performance prediction. This paper proposes to use Differential Dynamic Programming (DDP) for the optimization of elevator control for CEI takeoff certification analysis. To evaluate the method, two test cases are performed on the CEI takeoff of a small single-aisle aircraft model with different initial conditions. The results of two cases suggests that the DDP algorithm is able to optimize the trajectory in terms of minimizing takeoff distance, maximizing the rate of climb, and improving the compliance with respect to takeoff certification constraints. The optimized trajectory is sensitive to the initial control sequence given to the algorithm and the cost function settings

A Certification-Driven Platform for Multidisciplinary Design Space Exploration in Airframe Early Preliminary Design

Presented at AIAA Aviation 2020 ForumFollowing the conceptual phase of aircraft design, sizing and performance estimations shift from historical-based empirical equations to physics-based simulations. The initial aircraft configuration is refined with a larger number of objectives and requirements, and certification regulations play a critical role in defining these. Analysis tools in the early phases of preliminary design have an important trade-off between accuracy, complexity, and computational efficiency. A number of analysis frameworks currently exist with varying levels of fidelity, multidisciplinary coupling, and limitations in the number of disciplines, degrees of freedom, and requirements they are able to implement. To enable efficient design space exploration (DSE), this paper proposes an integrated preliminary design framework that couples aerodynamics, structures, subsystems, aircraft performance, flight dynamics, and certification testing at varying levels of fidelity. This framework serves as a numerical testbed that can be used to explore the aircraft configuration and disciplinary design spaces, strength of disciplinary couplings, and propagate disciplinary uncertainties across the entire aircraft system. The framework is demonstrated using the horizontal tail of a large twin-aisle aircraft as a test case