Person:

Mavris, Dimitri N.

Permanent Link

https://hdl.handle.net/1853/71501

Associated Organization(s)

Organizational Unit

Daniel Guggenheim School of Aerospace Engineering

Organizational Unit

Aerospace Systems Design Laboratory (ASDL)

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Publication Search Results

Now showing 1 - 8 of 8

Evaluation of Off-Nominal Performance and Reliability of a Distributed Electric Propulsion Aircraft during Early Design

(Georgia Institute of Technology, 2021-01-04) Bendarkar, Mayank ; Sarojini, Darshan ; Harrison, Evan D. ; Mavris, Dimitri N.

General Aviation (GA) is likely to be at the forefront of a paradigm change in aviation, where the introduction of novel concepts such as Urban Air Mobility (UAM), architectures like e-VTOL, and technologies like Distributed Electric Propulsion (DEP) are expected to make aircraft more efficient and reduce their environmental footprint. However, these architectures carry with them an uncertainty related to the off-nominal operational risk they pose. The limitations and off-nominal operational considerations generally postulated during traditional safety analysis may not be complete or correct for new technologies. While a lot of the literature surveyed focuses on improving traditional methods of safety analysis, it still does not completely address the limitations caused due to insufficient knowledge and experience with transformative technologies. The research objective of the present work is to integrate the Bayesian safety assessment framework developed previously by the authors with conceptual and 6-DoF performance models for DEP aircraft to evaluate off-nominal performance and reliability using information that is typically available in conceptual or preliminary design phases. A case study on the electric power architecture of the the NASA Maxwell X-57 Mod. IV is provided. A maximum potential flight path angle metric, as well as trimmability considerations using a 6-DoF model constructed using available literature help determine hazard severity of power degradation scenarios. Bayesian failure rate posteriors are constructed for the different components in the traction power system, which are used in a Bayesian decision framework. The results indicate that while most of the components in the traction power architecture of the X-57 Mod. IV are compliant with failure rate requirements generated, the batteries, cruise motors, and cruise motor-inverters do not meet those requirements.
Dynamic Simulation of Vehicle Maneuvers for Loads Analysis

(Georgia Institute of Technology, 2020-06) Jing, Xiao ; Berthon, Benjamin P. ; Somers, Luke A. ; Morgan, James R. ; Rairigh, Geoffrey R. ; Sarojini, Darshan ; Harrison, Evan D. ; Mavris, Dimitri N.

Testing critical loads during specific dynamic maneuvers is essential to aircraft structural design, and several such dynamic load cases must be demonstrated during the certification process. A simulation capability is developed in this work to calculate critical loads on the vertical tail of a business jet resulting from yaw maneuvers required for certification. The data produced from these simulations can be used to inform future structural design decisions. Models for the pilot and flight control system are developed to simulate the pilot control actions needed to perform the maneuvers within the boundaries of pilot capabilities and flight control system limits. Aerodynamic and propulsive data are used to calculate the forces and moments on the aircraft and solve the 6-degree of freedom equations of motion to accurately model the aircraft’s trajectory. Sectional aerodynamic characteristics of the horizontal and vertical tail are used to calculate the structural loads at each section of the tail. The summation of these forces and moments yields the loads at the vertical tail root, which can be used to assess the structural design of the tail. The simulation is demonstrated on a T-tail business jet with three weight conditions and at flight conditions throughout the flight test envelope. The ultimate loading conditions and the number of control application cycles required to reach ultimate loads at the vertical tail are determined using the maneuver simulation.
Differential Dynamic Programming to Critical-Engine-Inoperative Takeoff Certification Analysis

(Georgia Institute of Technology, 2020-06) Xie, Jiacheng ; Harrison, Evan D. ; Mavris, Dimitri N.

Critical-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 Model-Based Aircraft Certification Framework for Normal Category Airplanes

(Georgia Institute of Technology, 2020-06) Bendarkar, Mayank ; Xie, Jiacheng ; Briceno, Simon ; Harrison, Evan D. ; Mavris, Dimitri N.

A typical aircraft certification process consists of obtaining a type, production, airworthiness, and continued airworthiness certificate. During this process, a type certification plan is created that includes the intended regulatory operating environment, the proposed certification basis, means of compliance, and a list of documentation to show compliance. This paper extends previous work to demonstrate a model-based framework for the management of these certification artifacts for normal category airplanes. The developed framework integrates the regulatory rules and approved means of compliance in a single model while using best-practices found in Model-Based Systems Engineering (MBSE) literature. This framework, developed using SysML in MagicDraw captures not just the textual requirements and verification artifacts, but also their relationships and any inherent meta-data properties via custom defined stereotype profiles. Additionally, a simulation capability that automates the extraction and export of the applicable rules (certification basis) and corresponding means of compliance for any aircraft under consideration at the click of a button has been developed. The framework also provides numerous additional benefits to different stakeholders that have been described in detail with examples where necessary.
Aircraft Performance Model Calibration and Validation for General Aviation Safety Analysis

(Georgia Institute of Technology, 2020-03) Puranik, Tejas G. ; Harrison, Evan D. ; Chakraborty, Imon ; Mavris, Dimitri N.

Performance models facilitate a wide range of safety analyses in aviation. In an ideal scenario, the performance models would show inherently good agreement with the true performance of the aircraft. However, in reality, this is rarely the case: either owing to underlying simplifications or due to the limited fidelity of applicable tools or data. In such cases, calibration is required to fine-tune the behavior of the performance models. For point-mass steady-state performance models, challenges arise due to the fact that there is no obvious, unique metric or flight condition at which to assess the accuracy of the model predictions, as well as because a large number of model parameters may potentially influence model accuracy. This work presents a two-level approach to aircraft performance model calibration. The first level consists of using manufacturer-developed performance manuals for calibration, whereas the second level provides additional refinement when flight data are available. The performance models considered in this work consist of aerodynamic and propulsion models (performance curves) that are capable of predicting the non-dimensional lift, drag, thrust, and torque at any given point in time. The framework is demonstrated on two representative general aviation aircraft. The demonstrated approach results in models that can predict critical energy-based safety metrics with improved accuracy for use in retrospective safety analyses.
A Framework for General Aviation Aircraft Performance Model Calibration and Validation

(Georgia Institute of Technology, 2018-06) Puranik, Tejas G. ; Harrison, Evan D. ; Mavris, Dimitri N.

A wide range of aircraft performance and safety analyses are greatly facilitated by the development and availability of reliable and accurate aircraft performance models. In an ideal scenario, the performance models would show inherently good agreement with the true performance of the aircraft. However, in reality, this is almost never the case, either owing to underlying simplifications or assumptions or due to the limited fidelity of available or applicable analysis tools. In such cases, model calibration is required in order to fine tune the behavior of available performance models to obtain the desired agreement with the truth model. In the case of point-mass steady-state performance models, challenges arise due to the fact that there is no obvious, unique metric or flight condition at which to assess the accuracy of the model predictions, and since a large number of model parameters may potentially influence model accuracy. This work presents a systematic two- level approach to aircraft performance model calibration that poses the calibration as an optimization problem using the information available. The first level consists of calibrating the performance model using manufacturer-developed performance manuals in a multi objective optimization framework. If data is available from flight testing, these models are further refined using the second level of the calibration framework. The performance models considered in this work consist of aerodynamic and propulsion models (performance curves) that are capable of predicting the non-dimensional lift, drag, thrust, and torque produced by an aircraft at any given point in time. The framework is demonstrated on two popular and representative single-engine naturally-aspirated General Aviation aircraft. The demonstrated approach results in an easily-repeatable process that can be used to calibrate models for a variety of retrospective safety analyses. An example of the safety analyses that can be conducted using such calibrated models is also presented.
General Aviation Approach and Landing Analysis using Flight Data Records

(Georgia Institute of Technology, 2016-06) Puranik, Tejas G. ; Harrison, Evan D. ; Min, Sanggyu ; Jimenez, Hernando ; Mavris, Dimitri N.

Ensuring a safe and stabilized approach and landing is one of the important objectives in General Aviation applications. This phase is one of the main phases during which accidents occur. A "nominal" or reference trajectory for General Aviation approach and landing operations is critical for flight instruction and retrospective safety assessments reliant on flight data records captured with on-board systems. While this is a more crisply defined area in commercial aircraft operations, it is not so well-defined in General Aviation. The different aspects that need to be considered in defining a nominal trajectory and provide analyses that can be carried out using flight data records are examined. Various ways of defining this nominal or reference approach trajectory are proposed with the eventual aim of using this in conjunction with energy-based methods and metrics to assess and enhance safety in General Aviation aircraft operations.
Energy-Based Metrics for General Aviation Flight Data Record Analysis

(Georgia Institute of Technology, 2016-06) Puranik, Tejas G. ; Harrison, Evan D. ; Min, Sanggyu ; Jimenez, Hernando ; Mavris, Dimitri N.

Energy management and energy state awareness are important concepts in aircraft safety analysis. Many loss-of-control accidents can be attributed to poor energy management. Energy-based metrics provide a measurable quantity of the energy state of the aircraft and can be viewed as an objective currency to evaluate various safety-critical conditions. In this work, we have surveyed key energy-based metrics from various domains and identified the challenges of implementing these metrics for General Aviation operations. Modifications to existing metrics and definition of some new energy metrics are proposed. A methodology is developed that can be used to evaluate and visualize the energy metrics. These energy metrics can then be used to understand and enhance General Aviation aircraft safety using retrospective flight data analysis.