Jiacheng Xie
(Advisor: Prof. Dimitri N. Mavris)

will propose a doctoral thesis entitled,

Incorporating Airworthiness Certification Requirements into Unconventional Transport Aircraft Conceptual Design and Optimization

On

Monday, August 09th at 3:00 p.m.
https://bluejeans.com/124457277/0966

Abstract
Future aircraft are expected to be performance-efficient and environment-friendly. In response to aggressive environmental design goals, novel aircraft configurations and propulsion architectures have emerged in recent years. Although these revolutionary technologies are expected to improve aircraft aerodynamic and propulsive efficiencies, certification issues are impeding their implementations. The type certification is a mandatory process to ensure the safety of a new type of aircraft prior to entry into commercial services. This process is expensive, time-consuming, and subject to uncertainties since intensive analyses, experiments, and flight tests must be performed to demonstrate the compliance with airworthiness rules. Because of the novel design features and advanced technologies, unconventional aircraft may pose unique flight characteristics that are different from their conventional counterparts in certification flight tests, which makes the type certification process riskier and more challenging.

In traditional aircraft development process, the conceptual sizing and optimization is primarily driven by top-level performance requirements, but considerations on certification requirements are limited until the preliminary or detailed design starts. The challenge to consider certification requirements in conceptual design arises from the fact that the vehicle design knowledge is limited at early design phases and frequently updated as the design process moves to later stages. Because most existing certification analysis methods are computationally expensive and require detailed design information, in current conceptual design practice, some subsystems and components which should otherwise be sized according to certification requirements are typically accounted instead by semi-empirical methods with the correction factors based on the historical data of certified aircraft. However, applying this practice to unconventional aircraft poses a risk of converging to infeasible designs in terms of certification constraints, since the historical data of conventional aircraft may be inappropriate to represent the unique flight characteristics of unconventional aircraft. To minimize the cost associated with the design modifications to meet certification requirements, it is necessary to shift the certification considerations to early design stages before the degrees of design freedom are locked down.

This thesis aims to develop a methodology to explicitly account for the airworthiness certification requirements of Title 14 of Code of Federal Regulations Part 25 Subpart B Flight and Subpart C Structure in unconventional aircraft conceptual design and optimization. To demonstrate the proposed methodology, the NASA PEGASUS hybrid-electric aircraft is selected as the use case. The first objective of this thesis is to develop a certification analysis capability based on linearized flight dynamic simulation to capture the dynamic responses of unconventional aircraft in certification tests with design knowledge available at the conceptual stage. The second objective is to integrate the certification analysis capability with disciplinary analysis tools to create a certification-driven design framework and investigate the impacts of certification constraints on unconventional aircraft conceptual sizing and optimization. The third objective is to quantify the impacts of epistemic and aleatory uncertainties on certification analysis and certification-constrained design process.

Committee

• Prof. Dimitri N. Mavris – School of Aerospace Engineering (advisor)
• Prof. Daniel P. Schrage– School of Aerospace Engineering
• Prof. Brian J. German– School of Aerospace Engineering
• Dr. Evan D. Harrison – School of Aerospace Engineering
• Dr. Nicholas K. Borer – NASA Langley Research Center