PhD Studentship: in Nonlinear Flight Dynamics Applied to Generic T-Tailled Airliner Upset

Supervisors: Professor Mark Lowenberg (M.Lowenberg@bristol.ac.uk), Dr Duc Nguyen (duc.nguyen@bristol.ac.uk)

Overview

Accidents due to airliner upset, which have for many years been the largest cause of fatalities, remain a considerable safety concern. Airliner upset and loss-of-control are nonlinear flight dynamics phenomena so that predicting their characteristics for a particular aircraft is challenging, as is the task of designing methods of prevention and/or recovery.

There is extensive experience in nonlinear flight dynamics research at the University of Bristol, both computational and experimental. The former includes applications of bifurcation analysis techniques whilst the latter focuses on dynamic wind tunnel testing using the so-called ‘manoeuvre rig’ – which provides a multi-degree-of-freedom testing approach aimed at investigating the aerodynamics and flight mechanics of model aircraft motions, driven by on-board control surfaces or externally via the rig, that involve nonlinear and unsteady flow phenomena.

The project

This PhD will build on previous research into the flight dynamics of the NASA Generic T-Tailed airliner model (GTT). This aircraft configuration was defined by NASA specifically for studying upset in T-tailed airliners where the deep stall phenomenon can lead to loss of control. The previous PhD entailed static wind tunnel testing of a GTT wind tunnel model and a series of radio-controlled flight tests of a model of the same scale. It produced new and valuable insights into the causes and manifestations of the nonlinear behaviours.

GTT flight test aircraft, built and tested by PhD candidate, Daniel Pusztai in 2023.

The proposed PhD aims to extend the understanding of the GTT stall and post-stall dynamics by a combination of computational work and experiments on the manoeuvre rig, to physically simulate free-flight conditions in a controlled environment. Objectives include deepening our understanding of the aerodynamic phenomena governing stall and post-stall behaviour, classifying the different types of behaviour and their dependence on flight parameters, and evaluating the role of kinematic and inertial nonlinearities that come into play once instabilities arise. The PhD could potentially also apply this knowledge to the design of improved control laws.

A combined computational-experimental approach has been shown in other nonlinear dynamics studies at the University to be particularly valuable in uncovering the multiple attractors underlying observed responses. It is expected that in this PhD it will lead to novel contributions to the field of airliner upset and loss-of-control.

The candidate

To be eligible for funding, the candidate must have achieved a first-class or upper 2:1 undergraduate degree in aerospace or mechanical engineering, or equivalent; or, if in final year of undergraduate or masters study, should currently hold grades that strongly suggest that a 1^st or high 2:1 or equivalent will be achieved.

In order to be a good fit for the position, the candidate should also have:

• a strong background in flight dynamics and in engineering mathematics;
• some experimental experience, ideally in wind tunnel testing;
• display potential for independent research and have a creative and inquisitive mind.

Funding restrictions: none (note: studentship funding needs to be sought for this project).

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