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1967-02-01
Technical Paper
670331
J. D. Kester, T. G. Slaiby
This paper discusses the design of the JT9D-1 engine from the viewpoint of the noise reduction features which have been incorporated. Fan noise is predominant from high bypass ratio turbofans. The various sources of fan noise are discussed and the research work of the past several years on methods of noise reduction are reviewed. The paper discusses the application of the results of this work to the JT9D-1 design.
1967-02-01
Technical Paper
670162
A. M. Sogoian, W. V. Paliga
1967-02-01
Technical Paper
670161
Robert M. LaBreche
This paper contains a practical discussion of the applications of reverberation chambers to acoustical measurement problems often encountered by noise control engineers. The important characteristics of a reverberation chamber are explained and typical reverberation chamber construction demonstrated. The advantage of the reverberation chamber as a simple method of measuring certain acoustic phenomena and acoustical properties is illustrated by its application in three typical examples. First, the application of the room to measurements involving directional sound sources is illustrated by a study of automotive alternator noise. Second, the use of the room as a nondirectional sound source in measurement of acoustical material properties is illustrated by sound barrier tests of material sample installations.
1967-02-01
Technical Paper
670168
Roy D. McKenzie, Wm. Max Howell, David E. Skaar
The method is presented which enables a prediction of vehicular performance relative to a specified physical environment. The discussion centers around the parameters which are required to specify the vehicle, the driver, and the environment together with the computational procedure used to estimate vehicular mobility in terms of these parameters. Analog and digital simulation results are presented for wheeled and tracked vehicles respectively.
1967-02-01
Technical Paper
670140
L. J. Moulton
This paper reviews various environments established by the aircraft gas turbine itself, by the aircraft, and by new aircraft engine specifications within which fuel and control systems must operate. Emphasis is on the design requirements placed on controls to assure satisfactory operation in these environments. The influences on design choices and the demands for special testing are discussed for several components. As its objectives, the paper identifies specific areas which may prove troublesome as controls are designed to meet the new requirements. Recognition of potential problem areas is suggested as a first step toward successful design.
1967-02-01
Technical Paper
670155
James J. Dias
The advent of the on-board gas turbine auxiliary power unit in commercial aircraft created problems of excessive noise levels affecting both passengers and aircraft personnel. This paper analyzes those problems and outlines the advanced techniques being used to reduce gas turbine noises to an acceptable level. Being directed primarily at the gas turbine engineer, a brief explanation of pertinent acoustical terminology is presented to provide a basis for his understanding. Treatment of the major noise sources of a gas turbine and its installation are discussed and evaluated from the standpoint of maximum noise reduction.
1967-02-01
Technical Paper
670157
Henry B. Moore, J. Michael Clinch
The effectiveness of extended plug nozzles in reducing jet engine exhaust noise was investigated on small scale laboratory nozzles at ITT Research Institute and on a small turbojet engine at Williams Research Corp. The geometry of the nozzle was optimized on the basis of noise reduction versus thrust loss. The extended plug reduced noise on both laboratory nozzles and the turbojet engine for pressure ratios above critical. The use of a small turbojet engine for evaluating noise suppression devices is described.
1967-02-01
Technical Paper
670021
Bruce D. Van Deusen
This paper describes techniques that predict and analyze dynamic response of vehicles traversing random rough surfaces. Road irregularities are statistically classified by frequency and amplitude distribution. This classification determines the nature of random inputs to mathematical vehicle models and allows computer prediction of dynamic response of a simulated vehicle. Once inputs and models are defined, parametric analysis with output criteria specified statistically can be performed. This allows prediction of vehicle riding quality and evaluation of design concepts. Statistical analysis of accelerometer measurements on actual vehicles permits verification of the design process and meaningful comparison between vehicles.
1967-02-01
Technical Paper
670068
Robert C. Hogle
There is no handbook of vehicle electrical system design or no secret formula which can serve as a guide in the development of electrical components for competitive events. The basic approach to the extent possible, therefore, was to use production components or components for which we had considerable background experience.
1967-02-01
Technical Paper
670061
Homer J. Wood
Curve-fitting functions are combined with transfer functions and special parameter groupings to demonstrate that amplitude-limiting effects of hydrodynamic bearings on vibrations associated with critical speeds of flexible rotors are due to nonlinear characteristics. It is shown that stable and/or critically-damped operation can be achieved by designing bearings within proper ranges of a “dynamic load number” and controlling unbalance expressed as principal axis deviation related to clearance. The form of the attitude angle function is shown to be particularly significant with respect to unbalance tolerance. Practical application techniques are illustrated.
1967-02-01
Technical Paper
670193
R. Bruce Hopkins
A brief description of the representation of physical systems as idealized systems and the computation of natural frequencies is given. Using an example of an engine and power shift transmission system, it is shown that a simplified analysis can be made with small effect on the computed natural frequencies. The prevention of torsional vibrations with a power shift transmission, and the prevention of gear rattle in conventional transmissions, is discussed.
1967-02-01
Technical Paper
670234
Frederick W. Garry
Techniques for increasing the life of small jet engine components have been developed. Turbine nozzles have been improved by introducing localized cooling, and by changes in mechanical design. In the bearing area, life has been increased by reduction of axial thrust and vibratory loads, and the total bearing-lubrication system has been improved by changes in sump venting and carbon seal cooling. Rotor vibration problems have been decreased by changes in design assembly and techniques and bearing supports; and the results of vibration on connecting components have been controlled by study and treatment on a system basis. Integration of numerical computation with test results and field experience is presented as a basis for rational life predictions of rotor parts.
1967-02-01
Technical Paper
670237
E. Forest Critchlow
Abstract Some of the more general types of dynamic vibration that exist in aircraft, particularly the powerplant components, are reviewed for reciprocating and turbine engines as well as helicopter and unconventional drive systems. The responsiveness of various components to the source of excitation, resulting in either resonant or nonresonant (forced) vibration, is discussed. The importance of evaluating the fatigue life of a component at varying load conditions, both in the laboratory and field, is stressed.
1967-02-01
Technical Paper
670873
S. Rubin, F. A. Biehl
The paper demonstrates a mechanical impedance approach to an aircraft vibration problem. The desire is to reduce cabin noise resulting from fuselage vibration generated by engine rotor unbalance disturbances. A simplified analytical model is used in combination with experimental impedance data to investigate the effectiveness of several schemes applied to the engine/airframe interface. Airframe vibration absorbers are found to be the most effective. Qualitative correlation is achieved with the results of the installation of absorbers on the Douglas DC-9 aircraft. A more comprehensive analytical model is generated to account for three-dimensional effects; data acquistion for this model is discussed.
1967-02-01
Technical Paper
670507
V. A. Zastrow, E. R. Bernson
The causes of turbine blade excitation are described, and the factors that influence amplitudes of vibration are discussed. Blade rotation in an asymmetrical pressure field produces a periodic force on the blade. Harmonics of this periodic force excite the blades at their natural frequencies. Gas disturbances created by nozzle vanes also can excite the blades. Amplitudes are affected by the type of exhaust system combined with the type of turbine housing, turbine housing design, engine speed, vane design, and any local gas disturbance or condition that creates asymmetrical gas flow through the turbine housing.
1967-02-01
Technical Paper
670099
R. Thomas Bundorf
The handling behavior of an automobile towing a full-size travel trailer at high speed is studied analytically. A computer simulation of the system indicates the proper range of design and load parameters for best handling quality and illustrates the effect of some hitch design parameters. Associated analysis provides supplementary insight into the factors affecting stability of automobile-trailer combinations.
1967-02-01
Technical Paper
670892
Leonard, Segel, Ray W. Murphy
This paper presents a detailed, yet by no means exhaustive, survey of the application of mathematical modeling and simulation to dynamic problems in various engineering fields. After a brief discussion of the steps involved in the modeling process, applications are cited in the fields of aircraft design, control systems, circuit analysis and synthesis, structures, process control, vehicles other than aircraft, and human performance. Detailed consideration is given to two examples: design and optimization of an aircraft control system, and prediction of nonperiodic structural loading on a rotary wing. Finally, it is suggested how techniques successfully applied in other fields can aid in automotive vehicle safety studies.
1966-08-01
Standard
ARP699C
This Recommended Practice is intended to outline the design, installation, testing, and field maintenance criteria for a high temperature metal pneumatic duct system, for use as a guide in the aircraft industry. These recommendations are to be considered as currently applicable and necessarily subject to revision from time to time, as a result of the rapid development of the industry.
1966-06-20
Standard
AIR764A
This technical report documents three surveys to determine realistic vibration requirements for skid control systems specifications and obtain updated vibration information for locations in aircraft where skid control system components are mounted.
1966-05-15
Standard
AIR902
A photographic technique is described for determining minimum observer-to-aircraft distances during acoustic "fly-over" tests. Possible sources of error are discussed, and it is shown that with ordinary care results are sufficiently accurate to require no correction.
1966-05-01
Standard
J919_196605
This SAE Standard describes the instrumentation and procedures to be used in measuring sound levels at the operator station for self-propelled sweepers as defined in SAE J2130 and self-propelled off-road work machines in categories 1, 2, 4, and 5, of SAE J1116. This SAE document is applicable to machines that have operator stations where the operator can either stand or sit and will be either transported by, or walk with the machine during its operation. The sound levels obtained using this procedure are repeatable and representative of the higher range of sound levels generated by machines under actual field operating conditions. Due to variability of field operating conditions, this data is not intended to be used for operator noise exposure evaluations. Measurement and calculation of the operator's sound exposure should follow SAE J1116.
1966-05-01
Standard
J903A_196605
This SAE Recommend Practice establishes for passenger cars, light trucks, and multipurpose vehicles with GVW or 4500 kg (10 000 lb) or less: a. Minimum performance standards for windshield wiper systems. b. Test procedures that can be conducted on uniform test equipment by commercially available laboratory facilities. c. Uniform terminology of windshield wiper system characteristics and phenomena consistent with those found in guides for the use of engineering layout studies to evaluate system performance. d. Guides for the design and location of components of the systems for function, servicing of the system, etc. The test procedures and minimum performance standards, outlined in this document, are based on currently available engineering data. It is the intent that all portions of the document will be periodically reviewed and revised as additional data regarding windshield wiping system performance are developed.
1966-03-01
Magazine
1966-02-01
Technical Paper
660317
Robert B. Meyersburg
Realistic assessment of the role of V/STOL air transportation in the 1970’s is important to government transportation policies being formulated. Studies of a system, including the vehicle, airport, air traffic, and navigation facilities, were conducted in a specific market -- the California Corridor. Four VTOL aircraft representing various concepts were designed to a common set of requirements. These aircraft, one STOL, a conventional jet aircraft, and a conventional helicopter, were operated in a simulated airline network. Costs and revenues were compared to those of conventional jet aircraft operating on the same airline network. Ground transportation systems were assessed, including the automobile which is a formidable opponent on shorter routes. However, the STOL/VTOL systems by virtue of their convenience and overall speed, capture some traffic from other transportation means and generate new customer markets.
1966-02-01
Technical Paper
660311
Clarence E. Danforth
Precise analysis and experimental verification as an integral part of the complex design process make possible the jet execution and attainment of design goals for long life jet engines. This paper emphasizes the key factors of fatigue insensitivity as represented by control of vibration, the cyclic character of engine operation, the control of transient thermal response, and a constant alertness to the limitations of familiar measures of material strength in establishing permissible levels of structural loads. Each factor is discussed fully in relation to specific areas of the engine and is supported by illustrative test and computational data.
1966-02-01
Technical Paper
660295
W. M. Magruder, J. F. McDonald
The operational and maintenance characteristics of a commercial double delta supersonic transport are compared with those of contemporary subsonic vehicles. It is shown that the large delta wing in combination with the high thrust engines provides exceptional safety margins for take-off and landing conditions. The pilot's viewpoint is given upon low speed handling and controllability in emergency situations. Comments on maintenance considerations peculiar to such an aircraft are made and the general design philosophy is reviewed at this stage of the U. S. Supersonic Transport Program.
1966-02-01
Technical Paper
660281
R. E. Black
A welcome relief to airport runway, taxiway, gate position saturation, and air traffic congestion is offered by the new Super Sixty Series DC-8, which now carries twice as many passengers per flight. Airplane operators benefit from substantially lower direct operating costs per seat-mile and more efficient utilization of pilot manpower in an area of growing shortage. These airplanes have a special family of problems in common with earlier jets, including community annoyance caused by noise, runway strength limitations, and the requirement for an increase in terminal people and bag gage handling equipment.
1966-02-01
Technical Paper
660598
Douglas W. Rowley
The noise properties of the agricultural farm tractor are discussed. The major noise sources are identified, along with a review of why, how, and to what degree these sources should be controlled. Because of their similarity, the information is also applicable to construction machinery equipment. The control of intake and exhaust noise is dealt with from an overall tractor noise standpoint -- tractor noise being more than just exhaust noise. The conventional air cleaner is treated as a silencing device. Experimental data and analytical methods are presented to substantiate that one must be concerned with the entire exhaust or induction system -- not just the muffler or air cleaner -- to get the optimum benefit from the materials and space used while retaining maximum engine and vehicle performance.
1966-02-01
Technical Paper
660599
Robert T. Larsen
Dynamic testing yields more realistic values for the spring rates of rubber mounts used in vibration isolation systems. Shore durometer, 20% load deflection, tensile modulus, and other static tests have generally shown little relation to the actual spring behavior under field conditions.

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