The promise of multicyclic control

Several types of rotors which employ multicyclic control are reviewed and compared. Their differences are high-lighted and their potential advantages and disadvantages are discussed. The flow field these rotors must operate in is discussed, and it is shown that simultaneous elimination of vibration and oscillatory blade loads is not an inherent solution to the roughness problem. The use of rotor blades as energy absorbers is proposed. Input-output relations are considered and a gain control for ROMULAN, a multicyclic controlling computer program, is introduced. Implications of the introduction of multicyclic systems into helicopters are discussed

Multicyclic jet-flap control for alleviation of helicopter blade stresses and fuselage vibration

Results of wind tunnel tests of a 12 meter-diameter-rotor utilizing multicyclic jet-flap control deflection are presented. Analyses of these results are shown, and experimental transfer functions are determined by which optimal control vectors are developed. These vectors are calculated to eliminate specific harmonic bending stresses, minimize rms levels (a measure of the peak-to-peak stresses), or minimize vertical vibratory loads that would be transmitted to the fuselage. Although the specific results and the ideal control vectors presented are for a specific jet-flap driven rotor, the method employed for the analyses is applicable to similar investigations. A discussion of possible alternative methods of multicyclic control by mechanical flaps or nonpropulsive jet-flaps is presented

An investigation of a stoppable helicopter rotor with circulation control

A stoppable helicopter rotor with circulation control was investigated in the Ames 40 by 80 foot wind tunnel. The model was tested as a rotating wing, a fixed wing, and during transition start/stop sequences. The capability of the model's control system to maintain pitch and roll moment balance during the start/stop sequence, the ability of the blades to withstand the start/stop loads, the adequacy of the control system to maintain balance in the helicopter mode, and the control system capabilities in the fixed-wind mode were assessed. Time-history data of several start/stop sequences of the X-wing rotor, and the steady-state data relating to the model as both a rotor and as a fixed-wing aircraft are presented. In addition, stability data are presented which were acquired during open-loop and closed-loop tests of the hub moment feedback control system

Control of rotorcraft retreating blade stall using air-jet vortex generators

A series of low-speed wind tunnel tests were carried out on an oscillating airfoil fitted with two rows of air-jet vortex generators (AJVGs). The airfoil used had an RAE 9645 section and the two spanwise arrays of AJVGs were located at x/c=0.12 and 0.62. The devices and their distribution were chosen to assess their ability to modify/control dynamic stall; the goal being to enhance the aerodynamic performance of helicopter rotors on the retreating blade side of the disc. The model was pitched about the quarter chord with a reduced frequency (k) of 0.1 in a sinusoidal motion defined by a=15o+10sin_ t. The measured data indicate that, for continuous blowing from the front row of AJVGs with a momentum blowing coefficient (C μ) greater than 0.008, modifications to the stalling process are encouraging. In particular, the pitching moment behavior exhibits delayed stall and there is a marked reduction in the normal force hysteresis

The Relationship of Jewish Community Contexts and Jewish Identity: A 22-Community Study

This paper explores the manner in which Jewish community contexts relate to Jewish identity. We employ the Decade 2000 Data Set that contains almost 20,000 randomly selected Jewish households from 22 American Jewish communities interviewed from 2000 to 2010. Because of the large sample size, and its incorporation of community infrastructure data, this research also is able to examine various influences on Jewish identity that have not been definitively addressed in previous research, including the manner in which characteristics of Jewish community infrastructure are related to individuals’ Jewish identity. The Decade 2000 Data Set used for the analysis is described and some of the methodological considerations involved in its use are presented. Jewish identity is conceptualized as multidimensional, and a factor analysis results in four Jewish identity factors: a communal religious factor, a private religious factor, a broader ethnic factor, and a local ethnic factor. Multiple regressions for each of the Jewish identity factors are related to Jewish community characteristics; more commonly researched individual-level variables (Jewish background and connections, family status, socioeconomic status, demographic/geographic characteristics); and survey-level variables (such as size of sample and year of study) are also controlled. Surprisingly, except for the local ethnic factor, Jewish community characteristics have little relationship to individual Jewish identity. The contributions to a “sociology of Jewish place” and suggestions for further research are also discussed