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Analysis of Dynamic Flight Loads
KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Flight Dynamics. (Flygdynamik, Flight Dynamics)
2012 (English)Licentiate thesis, comprehensive summary (Other academic)
Abstract [en]

This thesis deals with the determination of loads on an aircraft struc- ture during flight. The focus is on flight conditions where the loads are significantly time-dependent. Analysis of flight loads is primarily motivated to ensure that structural failure is avoided. The ability to ac- curately determine the resulting structural loads which can occur during operation allows for a reduction of the safety margins in the structural design. Consequently it is then possible to decrease the aircraft struc- tural weight. The demand for safe and fuel efficient aircraft creates a desire for efficient and accurate methods for determining the structural loads.

The first paper of this thesis discusses the use of control laws for robust atmospheric turbulence load alleviation in the time domain. A numerical aircraft model including structural elasticity and unsteady aerodynamic effects is used. A limited set of longitudinal flight mechanic degrees of freedom are considered and two methods for structural load analysis are compared for evaluation of the wing root bending moment.

In the second paper a method to perform time domain simulation of both motion of center of gravity and elastic deformation is described. The intention with the development of this simulation method is to enable efficient analysis of dynamic flight loads.

A third study is finally included, where steady and unsteady pressure measurements have been carried out during wind tunnel testing. The motivation for performing these experiments is that knowledge about the aerodynamic force distribution which affect an aircraft structure is needed to correctly determine the structural loads.

Place, publisher, year, edition, pages
KTH Royal Institute of Technology, 2012. , 27 p.
Series
Trita-AVE, ISSN 1651-7660 ; 2012:27
National Category
Aerospace Engineering
Identifiers
URN: urn:nbn:se:kth:diva-94881OAI: oai:DiVA.org:kth-94881DiVA: diva2:526304
Presentation
2012-05-28, D3, Lindstedsvägen 5, Stockholm, 10:15 (English)
Opponent
Supervisors
Note
QC 20120529Available from: 2012-05-29 Created: 2012-05-11 Last updated: 2012-05-29Bibliographically approved
List of papers
1. Robust Turbulence Load Alleviation
Open this publication in new window or tab >>Robust Turbulence Load Alleviation
2011 (English)In: IFASD 2011: International Forum on Aeroelasticity and Structural Dynamics, 2011Conference paper, Published paper (Other academic)
Abstract [en]

Using a comparatively detailed aeroelastic model for a generic commuter aircraft, a turbulence load alleviation system is designed with the objective of reducing structural fatigue. An H-optimal controller for the nominal model is found to be highly sensitive to small disturbances in the control system dynamics, so that a slightly perturbed closed-loop model is destabilized. Robust control methods are exploited to construct an alternative controller which improves robustness to disturbances at a small cost in nominal performance. Finally, fatigue loads experienced by the (open-loop and controlled) model are evaluated by means of two different load reconstruction methods, showing that the simpler modal displacement approach may introduce significant errors in wing bending moments.

Keyword
robust control theory, aeroservoelasticity, flight simulation
National Category
Aerospace Engineering
Identifiers
urn:nbn:se:kth:diva-77685 (URN)
Conference
International Forum on Aeroelasticity and Structural Dynamics 2011, Paris, France
Note
QC 20120214Available from: 2012-02-14 Created: 2012-02-07 Last updated: 2012-05-29Bibliographically approved
2. Time-domain simulation for flight loads analysis
Open this publication in new window or tab >>Time-domain simulation for flight loads analysis
2012 (English)Report (Other academic)
Abstract [en]

A method for performing flight simulations considering both the motion of the center of gravity and the elastic deformation of the aircraft structure is developed. The time history of the included states is intended to be used for analysis of structural loads. The utilized time-integration scheme, the evaluation of ex- ternal forces and the solution of the equations of motion for the included states are presented. The effect of including elastic ef- fects and quasi-steady aerodynamic modeling is investigated for a simple longitudinal maneuver with a generic commuter aircraft.

Publisher
19 p.
National Category
Aerospace Engineering
Identifiers
urn:nbn:se:kth:diva-94871 (URN)
Note
QC 20120511Available from: 2012-05-11 Created: 2012-05-11 Last updated: 2012-05-29Bibliographically approved
3. Steady and unsteady pressure measurements on a swept-wing aircraft
Open this publication in new window or tab >>Steady and unsteady pressure measurements on a swept-wing aircraft
2011 (English)Report (Other academic)
Publisher
18 p.
Series
Trita-AVE, ISSN 1651-7660 ; 2011:91
National Category
Aerospace Engineering
Identifiers
urn:nbn:se:kth:diva-91404 (URN)
Note
To be submitted for publication. QC 20120315Available from: 2012-03-14 Created: 2012-03-14 Last updated: 2012-05-29Bibliographically approved

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CiteExportLink to record
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Citation style
  • apa
  • harvard1
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Output format
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