Vibration Isolation of Aircraft Power Plants

Taylor, E. S.; Browne, K. A.

doi:10.2514/8.760

Cited by 48 publications

(13 citation statements)

References 2 publications

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“…(16), the augmented state variables, 1 X and 2 X , are governed by a system of ordinary differential equations, and associated with a downwash velocity at the three quarter chord location, ( ) Q ψ , [15]. These augmented states are driven by the time history of ( ) Q ψ at each spanwise location.…”

Section: Aerodynamic Modelmentioning

confidence: 99%

“…This phenomenon has occurred in both turbo-prop and tiltrotor aircraft. The whirl flutter phenomenon in general aircraft with a propeller was first examined by Taylor and Brown [1]. However, a tiltrotor aircraft is more susceptible to this type of instability due to its higher level in the rotor blade flapping, bending, and the prominent control system flexibility.…”

Section: Introductionmentioning

confidence: 99%

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Analysis of tiltrotor whirl flutter in time and frequency domain

2009

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The whirl flutter phenomenon in a rotor is induced by in-plane hub forces, and imposes a serious limit on the forward speed. In this paper, based on Greenberg's model, quasi-steady and unsteady aerodynamic forces are formulated to examine the whirl flutter stability for a three-bladed rotor without flexible wing modes. Numerical results are obtained in both time and frequency domains. Generalized eigenvalue solution is utilized to estimate the whirl flutter stability in the frequency domain, and Runge-Kutta method is used to analyze it in time domain. The effects of varying the pylon spring stiffness and the swashplate geometric control coupling upon the flutter boundary are investigated. An optimum pitch-flap coupling parameter is discovered through the parametric study. Aeroelastic stability boundaries are estimated with the three different aerodynamic models. It is found that the analysis with the full unsteady aerodynamics predicts the highest flutter speed.

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Section: Aerodynamic Modelmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Analysis of tiltrotor whirl flutter in time and frequency domain

2009

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“…The model was designed as a typical aeroelastic model with 5 duralumin spar and balsa segment structure. The model was used for investigation of the influence of the wing to the characteristics of the whirl flutter.…”

Section: Experimental Research Of Whirl Fluttermentioning

confidence: 99%

“…The prop-whirl flutter phenomenon was analytically discovered by Taylor and Browne in 1938 [5]. The next work in the field was performed by Ribner in 1945 [1], [2] who set the basic formulae for the aerodynamic derivatives of propeller forces and moments due to the motion and velocities in pitch and yaw.…”

Section: Introductionmentioning

confidence: 99%

Design and Development of New Whirl Flutter Aeroelastic Demonstrator

Cecrdle

Malecek

2014

55th AIAA/ASME/ASCE/AHS/ASC Structures, Structural Dynamics, and Materials Conference

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This paper deals with the design and development of the new whirl flutter aeroelastic demonstrator. The paper gives a theoretical background of the whirl flutter phenomenon and summarizes the whirl flutter occurrence in the aerospace practice. The second part is focused on the experimental research of the whirl flutter. At first the brief summary of past main developments in this field is provided. The main part deals with the new aeroelastic demonstrator "W-WING" designed and developed at the VZLU. The demonstrator represents the wing and engine of the twin turboprop commuter aircraft. Contrary to the most of past demonstrators it includes thrusting propeller. It allows the changes of the main structural parameters influencing the whirl flutter stability characteristics. The demonstrator is intended for the experimental investigations in the VZLU 3m-diameter low-speed wind tunnel. The results will be utilized for validation of analytical methods and software tools as well as in the frame of the research projects. KEYWORDS aeroelasticity, flutter, whirl flutter, W-WING demonstrator 1.0 INTRODUCTIONThe turboprop aircraft airworthiness regulations include the requirement of certification considering the whirl flutter. The whirl flutter (also called gyroscopic flutter) is the specific case of flutter which takes account for the additional dynamic and aerodynamic influences of the engine rotating parts. Rotating parts like a propeller or a turbine increase the number of degrees of freedom and cause additional forces and moments. Moreover rotating propeller causes a complicated flow field and interference effects between wing, nacelle and propeller. The essential fact is an unsymmetric distribution of forces on a transversely vibrating propeller. Whirl flutter may cause a propeller mounting unstable vibrations, even a failure of an engine, nacelle or whole wing.The prop-whirl flutter phenomenon was analytically discovered by Taylor and Browne in 1938 [5]. The next work in the field was performed by Ribner in 1945 [1], [2] who set the basic formulae for the aerodynamic derivatives of propeller forces and moments due to the motion and velocities in pitch and yaw. After the accidents of two Lockheed L-188 C Electra II airliners in 1959 and 1960 the whirl flutter phenomenon came to the practical applications.The complicated physical principle of the whirl flutter required the experimental validation of the analytically gained results. Experimental research activities are demanded especially due to the unreliable analytical solution of the propeller aerodynamic forces. Other key issue is the influence of the structural damping. Whirl flutter is extremely sensitive to the structural damping. The validation of analytical results as well as the gaining of the reliable input data for analyses are in many cases feasible only experimentally. Downloaded by KUNGLIGA TEKNISKA HOGSKOLEN KTH on July 29, 2015 | http://arc.aiaa.org |

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“…The propeller whirl flutter phenomenon was analytically discovered by Taylor and Browne [1]. The next pioneering work was performed by Ribner, who set the basic formulae for the aerodynamic derivatives of propeller forces and moments due to the motion and velocities in pitch and yaw in 1945 [2,3].…”

Section: Introductionmentioning

confidence: 99%

Aeroelastic Stability of Turboprop Aircraft: Whirl Flutter

Cecrdle¹

2018

Flight Physics - Models, Techniques and Technologies

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This chapter is focused on a specific type of dynamic aeroelastic stability phenomenonwhirl flutter. Whirl flutter is caused by the effect of rotating parts of a turboprop power plant (propeller and, gas turbine engine rotor). The chapter presents fundamental facts regarding the whirl flutter phenomenon, including a historical overview and information regarding the occurrence of whirl flutter in aerospace practice. After that, the physical principles of whirl flutter are explained using a simple mechanical system with two degrees of freedom. Next, an analytical solution to determine the aerodynamic forces caused by the gyroscopic motion on each of the propeller blades is provided and the influences of the main structural parameters on the whirl flutter stability are discussed. The second, practical part is focused on the experimental research of the whirl flutter phenomenon and on the certification-related issues. The methodology of certification according to the FAR/CS 23 regulation standard is demonstrated on the example of a twin wing mounted tractor engine commuter aircraft.

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Vibration Isolation of Aircraft Power Plants

Cited by 48 publications

References 2 publications

Analysis of tiltrotor whirl flutter in time and frequency domain

Analysis of tiltrotor whirl flutter in time and frequency domain

Design and Development of New Whirl Flutter Aeroelastic Demonstrator

Aeroelastic Stability of Turboprop Aircraft: Whirl Flutter

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