Journal articles: 'Helicopter transmissions'

1

Haiwei, Wang, Li Lulu, and Yuan Sheng. "Research on Rapid Assembly Technology of Helicopter Transmissions." MATEC Web of Conferences 306 (2020): 05004. http://dx.doi.org/10.1051/matecconf/202030605004.

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Research and application of rapid assembly technology can widely improve the design efficiency of helicopter transmissions. An assembly model of helicopter transmissions is presented by introducing Geometric Constraint Graph (GCG) method. A hierarchical model is obtained by multi-shrink decomposition. A corresponding data structure is generated according to the hierarchical model. CATIA based a parametric component database is built up. The Assembly modelling software is implemented by using VB. Finally, a helicopter transmissions example is taken as application and the rapid assembly for helicopter transmission system is achieved.

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Davies, D. P., and B. C. Gittos. "Gear Steels for Future Helicopter Transmissions." Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering 203, no. 2 (July 1989): 113–21. http://dx.doi.org/10.1243/pime_proc_1989_203_062_01.

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In order to reduce weight, improve reliability and increase safety, significant changes in the design of future helicopter transmissions are envisaged. Such designs are likely to place new demands on conventional steels which will eventually result in the capability of the gear steels themselves to become the limiting factor, restricting any further opportunities for transmission design and development.

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Xue, Hui Ling, Geng Liu, Xiao Hui Yang, and Bing Han. "Key Technologies Research of Helicopter Transmissions." Applied Mechanics and Materials 743 (March 2015): 55–60. http://dx.doi.org/10.4028/www.scientific.net/amm.743.55.

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In the recent years, there has been significant interest in the new developments and improvements of the helicopter transmission systems. The main goal of the helicopter transmission research is the reduction of overall gear train weight while maintaining the efficiency and reliability. This paper reviews some significant technical developments in the component level and in the system configuration level. In addition, comprehensive test and verification technology of helicopter transmission system is discussed.

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Litvin, F. L., J. C. Wang, R. B. Bossler, Y. J. D. Chen, G. Heath, and D. G. Lewicki. "Application of Face-Gear Drives in Helicopter Transmissions." Journal of Mechanical Design 116, no. 3 (September 1, 1994): 672–76. http://dx.doi.org/10.1115/1.2919434.

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The use of face-gears in helicopter transmissions was explored. A light-weight, split torque transmission design utilizing face-gears was described. Face-gear design is discussed. Topics included basic design geometry, tooth generation, limiting inner and outer radii, and recommendation for the gear ratio. Face-gear experimental studies were also included and the feasibility of face-gears in high-speed, high-load applications such as helicopter transmissions was demonstrated. Torque-split tests were performed and demonstrated an accurate split of torque using the face-gear concept.

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White, G. "Split Torque Helicopter Transmissions with Widely Separated Engines." Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering 203, no. 1 (January 1989): 53–65. http://dx.doi.org/10.1243/pime_proc_1989_203_054_01.

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A three-stage helicopter transmission of split torque type is shown to offer advances in a configuration that allows the engine axes to be widely separated and parallel. Three variants of the configuration are examined; one design with separated drive paths and four final-drive pinions is discussed in detail. This design offers 26 per cent less weight and 9 per cent lower losses than current production transmissions. Comparison is made with epicyclic type transmissions of similar rating that have been developed in the past decade.

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6

Ye, Qian. "Event-driven PID control of autonomous quadrotor helicopters." Journal of Algorithms & Computational Technology 12, no. 2 (March 7, 2018): 159–64. http://dx.doi.org/10.1177/1748301818761134.

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This paper proposes an event-driven PID control mechanism for autonomous quadrotor helicopters that will reduce the usage of communication channels. Compared to traditional PID controller, the event-driven PID controller can maintain the satisfactory stabilization effect with the ability of reducing the number of transmissions significantly. The simplified dynamics model of quadrotor helicopter is also established. Finally, the improvements realized by the developed method are verified in the computer simulations.

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Astridge, D. G. "Helicopter Transmissions—design for Safety and Reliability." Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering 203, no. 2 (July 1989): 123–38. http://dx.doi.org/10.1243/pime_proc_1989_203_063_01.

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Recent improvements in design and component technologies are reviewed against a background of accident data analysis, resulting in grounds for confidence in higher safety levels in future rotorcraft transmission designs. Recommendations are made concerning the realization of significant safety and reliability benefits afforded by effective health and usage monitoring systems. The results of this study are applicable to all new aerospace gearbox applications including helicopters, tilt-rotor aircraft, advanced propeller engines and accessory drive systems.

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Handschuh, R. F., D. G. Lewicki, and R. B. Bossler. "Experimental Testing of Prototype Face Gears for Helicopter Transmissions." Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering 208, no. 2 (July 1994): 129–36. http://dx.doi.org/10.1243/pime_proc_1994_208_262_02.

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An experimental programme to test the feasibility of using face gears in a high-speed and high-power environment was conducted. Four face gear sets were tested, two sets at a time, in a closed-loop test stand at pinion rotational speeds to 19 100 r/min and to 271 kW (364 b.h.p.). The test gear sets were one-half scale of the helicopter design gear set. Testing the gears at one-eighth power, the test gear set had slightly increased bending and compressive stresses when compared to the full-scale design. The tests were performed in the NASA Lewis spiral bevel gear test facility. All four sets of gears successfully ran at 100 per cent of design torque and speed for 30 million pinion cycles, and two sets successfully ran at 200 per cent of torque for an additional 30 million pinion cycles. The results, although limited, demonstrated the feasibility of using face gears for high-speed, high-load applications.

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9

Lewicki, David G., Robert F. Handschuh, Zachary S. Henry, and Faydor L. Litvin. "Low-noise, high-strength, spiral-bevel gears for helicopter transmissions." Journal of Propulsion and Power 10, no. 3 (May 1994): 356–61. http://dx.doi.org/10.2514/3.23764.

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10

Tumer, Irem Y., and Edward M. Huff. "Analysis of Triaxial Vibration Data for Health Monitoring of Helicopter Gearboxes." Journal of Vibration and Acoustics 125, no. 1 (January 1, 2003): 120–28. http://dx.doi.org/10.1115/1.1526130.

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Research on the nature of the vibration data collected from helicopter transmissions during flight experiments has led to several crucial observations believed to be responsible for the high rates of false alarms and missed detections in aircraft vibration monitoring systems. This work focuses on one such finding, namely, the need to consider additional sources of information about system vibrations. In this light, helicopter transmission vibration data, collected using triaxial accelerometers, are explored in three different directions, analyzed for content, and then combined using Principal Components Analysis (PCA) to analyze changes in directionality. The frequency content of the three different directions is compared and analyzed using time-synchronously averaged vibration data. To provide a method for analysis and monitoring purposes, the triaxial data are decorrelated using a mathematical transformation, and compared to the original axes to determine their differences. The benefits of using triaxial data for vibration monitoring and diagnostics are explored by analyzing the changes in the direction of the principal axis of vibration formed using all three axes of vibration. The statistical variation introduced due to the experimental variables is further analyzed using an Analysis of Variance approach to determine the effect of each variable on the overall signature. The results indicate that triaxial accelerometers can provide additional information about the frequency content of helicopter gearbox vibrations, and provide researchers and industry with a novel method of capturing and monitoring triaxial changes in the baseline vibration signatures.

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11

Krantz, T. L., M. Rashidi, and J. G. Kish. "Split Torque Transmission Load Sharing." Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering 208, no. 2 (July 1994): 137–48. http://dx.doi.org/10.1243/pime_proc_1994_208_263_02.

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Split torque transmissions are attractive alternatives to conventional planetary designs for helicopter transmissions. The split torque designs can offer lighter weight and fewer parts but have not been used extensively for lack of experience, especially with obtaining proper load sharing. Two split torque designs that use different load-sharing methods have been studied. Precise indexing and alignment of the geartrain to produce acceptable load sharing has been demonstrated. An elastomeric torque splitter that has large torsional compliance and damping produces even better load sharing while reducing dynamic transmission error and noise. However, the elastomeric torque splitter as now configured is not capable over the full range of operating conditions of a fielded system. A thrust balancing load-sharing device was evaluated. Friction forces that oppose the motion of the balance mechanism are significant. A static analysis suggests increasing the helix angle of the input pinion of the thrust balancing design. Also, dynamic analysis of this design predicts good load sharing and a significant torsional response to accumulative pitch errors of the gears.

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12

Yin, Ze Yong, Bi Bo Fu, Tong Bo Xue, Yong Hong Wang, and Jie Gao. "Development of Helicopter Power Transmission System Technology." Applied Mechanics and Materials 86 (August 2011): 1–17. http://dx.doi.org/10.4028/www.scientific.net/amm.86.1.

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The helicopter power transmission system technology is the key technical area for improving the helicopter performance, reducing the noise/vibration level of helicopters and decreasing the cost of life cycle of helicopters. In this paper, the technical characteristics of the helicopter power transmission system are introduced first. Then, the development history and trend of the transmission configuration, the component and the design and analysis technique of the transmission system are described. The advanced material and process technology applied in the helicopter power transmission system are also described. Finally, the power transmission system technology used in the high speed helicopters is briefly presented.

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13

Fu, Chenxi, Ning Zhao, and Yongzhi Zhao. "Load Sharing Multiobjective Optimization Design of a Split Torque Helicopter Transmission." Mathematical Problems in Engineering 2015 (2015): 1–15. http://dx.doi.org/10.1155/2015/381010.

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Split torque designs can offer significant advantages over the traditional planetary designs for helicopter transmissions. However, it has two unique properties, gap and phase differences, which result in the risk of unequal load sharing. Various methods have been proposed to eliminate the effect of gap and promote load sharing to a certain extent. In this paper, system design parameters will be optimized to change the phase difference, thereby further improving load sharing. A nonlinear dynamic model is established to measure the load sharing with dynamic mesh forces quantitatively. Afterwards, a multiobjective optimization of a reference split torque design is conducted with the promoting of load sharing property, lightweight, and safety considered as the objectives. The load sharing property, which is measured by load sharing coefficient, is evaluated under multiple operating conditions with dynamic analysis method. To solve the multiobjective model with NSGA-II, an improvement is done to overcome the problem of time consuming. Finally, a satisfied optimal solution is picked up as the final design from the Pareto optimal front, which achieves improvements in all the three objectives compared with the reference design.

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14

Markova, E. V., A. M. Al-Darabseh, I. E. Daba’bneh, A. R. Ahmed, and B. T. Arazveliev. "DEVELOP AN INTEGRATED TECHNICAL SITUATION CONTROL SYSTEM TO CONTROL HIGH QUALITY HELICOPTERS BASED ON FIBER OPTIC TECHNOLOGY." Izvestiya of Samara Scientific Center of the Russian Academy of Sciences 23, no. 1 (2021): 21–27. http://dx.doi.org/10.37313/1990-5378-2021-23-1-21-27.

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This article draws attention to the difficulties in developing an integrated approach, especially the evaluation and evaluation of the main helicopter technology. Fiber optic technology is a technology that allows you to create a unified system. This allows the measurement of various physical parameters such as vibration, distortion, temperature, volume and other parameters, given the magnitude of optical fiber science. RMB can be integrated into production, which is an important factor in the amount of RMB related to the design and manufacture of helicopters. The test results, the test bench, and the rotor of the helicopter and light using optical fiber transmission in the Prague fiber optic filter emphasize the importance of developing technology to track the helicopter's use of optical fiber. Other embodiments of the use of optical transmission systems that use fiber-optic technology, such as cable warning of explosives and helicopter damage as well as system weight and transitions. The conduction system monitors air technology.

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15

Jonak, Kamil, and Arkadiusz Syta. "Gearbox damage identification using Ensemble Empirical Decomposition method." MATEC Web of Conferences 252 (2019): 06005. http://dx.doi.org/10.1051/matecconf/201925206005.

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In this article, we have conducted a comparative analysis of vibration signals from helicopter aircraft propulsion transmissions, registered on an industrial research stand. We compared acceleration vibrations in the case of gears without physical damage and gears with one tooth missing. Based on recorded signals, we determined the values of indicators based on the statistical properties of signals and compared them with each other. For a more exact comparison, the distribution of the tested signals to the empirical modes using the EEMD (Ensemble Empirical Mode Decomposition) method was performed. This allows to treat individual modes as components of a signal at specific frequencies, and also prevents mixing of modes in individual components, which may take place in the classic EMD analysis. It should be noted that individual modes may correspond to characteristic frequencies for the operation of the transmission. When comparing the values of the most frequently used indicators, modes/frequencies in which the damage was most visible were indicated.

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16

McSwain, R. H., E. B. S. Pardue, R. W. Hendricks, and M. V. Mathis. "X-Ray Stress Analysis of Nickel-Plated Components Using Different Radiation Wavelengths." Advances in X-ray Analysis 29 (1985): 49–55. http://dx.doi.org/10.1154/s0376030800010119.

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X-ray stress analyses were performed on seven (7) nickel-plated camshafts from helicopter transmissions. The purpose of this investigation was to determine if this residual stress technique was useful in determining the state of stress in load-bearing plated surfaces of critical reworked aircraft components. Specifically, it was desired to characterize six different stages of nickel plating processing. These were: as-plated, plated and baked, machined, machined and baked, ground, and ground and baked. Three different radiation wavelengths with different penetrations were used In this investigation. CrKα , CoKα , and CuKα, radiations were each used on all of the camshafts. These wavelengths were selected to determine if there were stress gradients in the plated layers. This paper presents and discusses the results of these studies.

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17

Wang, Wenyi, and Albert K. Wong. "Autoregressive Model-Based Gear Fault Diagnosis." Journal of Vibration and Acoustics 124, no. 2 (March 26, 2002): 172–79. http://dx.doi.org/10.1115/1.1456905.

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This paper presents a model-based technique for the detection and diagnosis of gear faults. Based on the signal averaging technique, the proposed technique first establishes an autoregressive (AR) model on the vibration signal of the gear of interest in its healthy-state. The model is then used as a linear prediction error filter to process the future-state signal from the same gear. The health condition of the gear is diagnosed by characterizing the error signal between the filtered and unfiltered signals. The technique is validated using both numerical simulation and experimental data. The results show that the AR model technique is an effective tool in the detection and diagnosis of gear faults and it may lead to an effective solution for in-flight diagnosis of helicopter transmissions.

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18

DeTurk, Scott M., and Roy J. Cunningham. "Correlation between fatigue crack growth rate and striation spacing in XZM." Proceedings, annual meeting, Electron Microscopy Society of America 48, no. 4 (August 1990): 834–35. http://dx.doi.org/10.1017/s0424820100177301.

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Much information can be learned from the fracture surface of a metallic component. At a microscopic level, the relationship between a fatigue fracture surface and the rate at which the crack propagated through the material is of particular interest. At certain growth rates, a fatigue fracture surface is comprised of striations which are the results of a cyclical loading being applied to a component. When evaluating a fatigue fracture surface to determine crack growth rates, a Transmission Electron Microscope (TEM) is employed to observe the striations. However, the following question arises, “Does one fatigue striation equal one load cycle”? In previously published literature, the relationship of one striation being equal to one load cycle has been confirmed for various aluminum alloys. The test data presented herein is for steel, i.e., a High Hot Hardness (HHH) gear material utilized in helicopter transmissions. The correlation of one striation being equal to one load cycle was obtained and documented during a fatigue crack growth test of X2M gear steel. A prime use of this data would be in the evaluation of a fatigue fracture surface to determine the initiation time and propagation rate for a service related failure.

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Zhang, Su Ning, Wen Qiang Ding, and Yong Hong Wang. "Development Solution of Civil Helicopter Transmission Train Vibration Monitoring System." Applied Mechanics and Materials 86 (August 2011): 342–47. http://dx.doi.org/10.4028/www.scientific.net/amm.86.342.

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Health & Usage Monitoring System (HUMS) is designed for improving airworthiness, reliability and effective maintenance management of helicopter by analysis of detected / diagnosed operation data internal/external environment data collected from the helicopter. Vibration monitoring system plays as an important part of entireness integrated HUMS, which offers a considerable improvement to conventional monitoring techniques. This paper covers development solution of civil helicopter transmission train Vibration monitoring system. Vibration monitoring system (VMS) constantly checks the performance of safety-critical components, provides warnings in advance of potential equipment failures and collects valuable data for routine maintenance of the helicopters.

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Harris, T. A., and J. I. McCool. "On the Accuracy of Rolling Bearing Fatigue Life Prediction." Journal of Tribology 118, no. 2 (April 1, 1996): 297–309. http://dx.doi.org/10.1115/1.2831299.

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Ball and roller bearings are designed to meet endurance requirements basically determined according to the Standard fatigue life calculation method. This method is based on the Lundberg-Palmgren fatigue life theory as modified by reliability, material, and lubrication factors. As application load and spied requirements have increased, the Lundberg-Palmgren method has resulted in bearings of increased size, adding unnecessarily to the size and weight of mechanisms. This is a critical design situation for weight and size-sensitive components such as aircraft gas turbine engines and helicopter power transmissions. The bearing life prediction method developed by Ioannides and Harris recognizes the existence of a fatigue limit stress. If the stresses an operating bearing experiences do not exceed the limit stress, the bearing can achieve infinite life. In any case, the method tends to predict longer lives than the Lundberg-Palmgren method. This paper evaluates the life prediction accuracies of the Lundberg-Palmgren and Ioannides-Harris methods by comparing lives calculated according to these methods and to those actually experienced in 62 different applications. As a result of the investigation, the Ioannides-Harris method is shown to more accurately predict bearing fatigue endurance.

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21

Kurdelski, Marcin, and Andrzej Gębura. "Evaluation of Steering Disks in Mi-17 and Mi-24 Helicopters by Means of the Fam-C Method." Research Works of Air Force Institute of Technology 33, no. 1 (January 1, 2013): 127–58. http://dx.doi.org/10.2478/afit-2013-0008.

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Abstract The paper deals with selected issues related to operation of steering disks designed for helicopters that are currently in operation of the Air Force of the Republic of Poland. The attempt is made to present a prediction of hazards to the transmission gear of that helicopter where the forecast is based on a theoretical analysis of mechanical phenomena as well as the statistical and diagnostic analyses. The major attention is paid to the opportunity to diagnose hazardous locations of the helicopter steering disk with use of a non-destructive FAM-C method originally developed by ITWL. The method is based on tracking of frequency modulation parameters generated by the on-board AC generator. The examination does not require the installation of any additional sensor since the transmission is subjected to neither additional load nor distortions of the rotation speed occur. The authors of this study disclosed the initial results from diagnostic measurements as well as snapshots taken during the disassembling of steering disks from Mi-24 and Mi-17 helicopters that were operated under heavy duty conditions of military missions in Iraq and Afghanistan. They also suggested an easy and cheap method for field checking of the steering disk bearing by photogrammetric measurements. It is also demonstrated that the method of diagnostic investigations can be also spread onto other helicopter makes and types.

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22

Zhang, Chi, Cheng Dong Xu, Xin Pei, and Chun Sheng Hu. "Information Acquisition of Maintenance, Repair and Overhaul/Operations System for Helicopters." Applied Mechanics and Materials 220-223 (November 2012): 2150–55. http://dx.doi.org/10.4028/www.scientific.net/amm.220-223.2150.

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The helicopter Maintenance, Repair and Overhaul/Operations (MRO) system enables the best sharing of the maintenance resources and maintenance ability in a wide area, so as to promote the specialization of the helicopter maintenance organizations. Information acquisition is an important and difficult part of the helicopter MRO system. This paper systematically analyzes the condition monitoring methods which are used to monitor the rotational speed, temperature, pressure, vibration and flight parameter in different parts of a helicopter, and then it puts forward some improved ways for information acquisition. Considering the helicopter’s features, the process of information acquisition is illustrated. In addition, this paper presents the basic requirements of data sampling, and it also shows a detailed discussion on data format and data transmission in the helicopter MRO system. At the end of the paper, a system mode and architecture of helicopter MRO system are proposed.

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23

Chen, Y., V. Wickramasinghe, and D. G. Zimcik. "DEVELOPMENT OF SMART STRUCTURE SYSTEMS FOR HELICOPTER VIBRATION AND NOISE CONTROL." Transactions of the Canadian Society for Mechanical Engineering 31, no. 1 (March 2007): 39–56. http://dx.doi.org/10.1139/tcsme-2007-0003.

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Helicopters are susceptible to high vibratory loads, excessive noise levels and poor flight stability compared to fixed-wing aircraft. The multidisciplinary nature of helicopter structures offers many opportunities for the innovative smart structure technology to improve helicopter performance. This paper provides a review of smart structures research at the National Research Council Canada for helicopter vibration and cabin noise control applications. The patented Smart Spring approach is developed to vary the blade impedance properties adaptively to reduce the vibratory hub loads transmitted to the fuselage by vibration reduction at the source. A smart gearbox strut and active structural acoustic control technologies are investigated to suppress the vibration and tonal gear meshing noise into the cabin either by modifying the vibration load transmission path, or weakening the coupling between exterior and cabin acoustic fields. Two adaptive seat mount concepts are proposed to reduce the vibration of the aircrew directly to improve ride quality of the vehicle.

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24

YAMAUCHI, Nobuyoshi. "Helicopter Transmission." Journal of the Japan Society for Precision Engineering 58, no. 8 (1992): 1281–83. http://dx.doi.org/10.2493/jjspe.58.1281.

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Gębura, Andrzej, and Krzysztof Zientalski. "Selected Problems Of Transmission Wear Of The Mi-24 Helicopter." Research Works of Air Force Institute of Technology 37, no. 1 (December 1, 2015): 25–44. http://dx.doi.org/10.1515/afit-2015-0024.

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AbstractThe hypothesis of mutual, destructive impact of the worn upper bearing of the WR-24 transmission on the Mi-24 helicopter's gearbox was stated. The Mi-24 is the only helicopter operated in Poland, in which the gearbox is mounted outside the main transmission – in the centre of the transmission shaft, between the main gearbox and the tail rotor. Damage to the gears in the gearbox of power generators is equivalent to termination of the tail rotor's drive. Such a termination immediately causes rotation of the body in the direction opposite to the direction of rotation of the main rotor. It is associated with the loss of lift and steering. It may lead to a disaster. Such an incident occurred in January 2011 in Afghanistan – both authors participated in its investigation. The authors, taking into account very good, almost legendary combat properties of the Mi-24, and their research of the specifics of wear and tear of the transmission elements, they think that, first, funds for development and implementation of the drive unit monitoring system should be made available specially for this helicopter. For this purpose, the authors propose to use the FAM-C method. It is characterised with significant ergonomics. Thank to this, multiple kinematic pairs can be observed simultaneously, and, therefore, the relationships between them as well.

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Spikes, H. A. "Future helicopter transmission oils." Journal of Synthetic Lubrication 3, no. 3 (1986): 181–208. http://dx.doi.org/10.1002/jsl.3000030303.

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Xuejun, Li, Jiang Lingli, Hua Dengrong, Yin Daoxuan, and Yang Dalian. "An Analysis of the Gear Meshing Characteristics of the Main Planetary Gear Trains of Helicopters Undergoing Shafting Position Changes." International Journal of Aerospace Engineering 2021 (July 30, 2021): 1–12. http://dx.doi.org/10.1155/2021/9965818.

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The complex three-shaft three-reducer structural designs of helicopter transmission systems are prone to changes in the relative positions of shafting under the conditions of main rotor and tail rotor loads. These changes will affect the transmission characteristics of the entire transmission system. In this study, the planetary gear trains of helicopters were examined. Due to the fact that these structures are considered to be the most representative structures of the main reducers of helicopters, they were selected as the study objects for the purpose of examining the meshing characteristics of planetary gear trains when the relative positions of the shafting changed due to the position changes of the main rotor shafts under variable load conditions. It was found that by embedding the comprehensive time-varying meshing stiffness values of the main rotor shafts at different positions, a dynamic model of the relative position changes of the planetary gear trains could be established. Then, combined with the multibody dynamics software, the meshing characteristics of the sun gears, and the planetary gears, the planetary gears and the inner ring gears were simulated and analyzed under different inclinations and offsets of the shafting. The results obtained in this study revealed the following: (1) the average meshing force of the gears increased with the increases in the angle inclinations, and the meshing force between the sun gears and the planetary gears increased faster than the meshing force between the planetary gears and the inner ring gears. It was observed that during the changes in the shafting tilt positions, obvious side frequency signals had appeared around the peak of the meshing frequency in the spectrum. Then, with the continuous increases in the tilt position, the peak was gradually submerged; (2) the average meshing force of the gears increased with the increases in the offset, and the increasing trend of the meshing force between the sun gears and the planetary gears was similar to that observed between the planetary gears and the inner ring gears. It was found that when the shafting offset position changed, there were obvious first and second frequency doubling in the spectrum; (3) the mass center orbit radii of the sun gears increased with the increases in the shafting position changes, and the changes in the angular tilt position were found to have greater influencing effects on the mass center orbit radii of the sun gears than the changes in the offset positions. This study’s research findings will provide a theoretical basis for future operational status monitoring of the main transmission systems of helicopters and are of major significance for improvements in the operational stability of helicopter transmission systems, which will potentially ensure safe and efficient operations.

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Cai, Xian Xin, Xiao Jun Guo, and Hai Yue Long. "Transmission System Health Management Technique." Applied Mechanics and Materials 86 (August 2011): 487–91. http://dx.doi.org/10.4028/www.scientific.net/amm.86.487.

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Health management techniques used by a helicopter transmission system, THM, are presented in this paper, including outline of the system, framework of the system and the procedures of the damage prediction. The improvement scheme of the system is proposed and investigated. THM has been tested in a process of a helicopter flying test, which indicates that techniques used here are effective.

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Fraser, K. F., and C. N. King. "Helicopter transmission fatigue life estimation." Journal of Aircraft 25, no. 5 (May 1988): 465–71. http://dx.doi.org/10.2514/3.45605.

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Mauricio, Alexandre, Junyu Qi, Linghao Zhou, Wenyi Wang, David Mba, and Konstantinos Gryllias. "Perspectives on Health and Usage Monitoring Systems (HUMS) of helicopters." MATEC Web of Conferences 314 (2020): 02008. http://dx.doi.org/10.1051/matecconf/202031402008.

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Helicopters are extensively used in civil applications as they are versatile in their capabilities to manoeuvre. Their operation under harsh conditions and environments demand for a strict maintenance plan. Main gearboxes (MGB) of helicopters are a critical component responsible for reducing the high input speed generated from the gas turbine engines. Health and Usage Monitoring Systems (HUMS) are installed in an effort to monitor the health state of the transmission systems, and ideally, to detect and diagnose the type of a generated fault. Even though the development of HUMS contributed to the reduction of worldwide helicopter accident rate, more advanced systems are needed based on the investigation of the air accidents of AS332 L2 Super Puma in Scotland in 2009 and of EC225 LP Super Puma in Bergen in 2016, due to failure of a planet gear of the MGB. A plethora of signal processing methodologies have been proposed for the early detection of faults but often they fail in complex structures, such as planetary gearboxes operating under various conditions. In this paper the performance of a recently proposed diagnostic tool, called IESFOgram, is evaluated and compared with state of the art techniques, applied on signal captured on a Category A Super Puma SA330 MGB.

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Ding, Wen Qiang. "Application Probing of Advanced Helicopter Transmission System Technology." Applied Mechanics and Materials 86 (August 2011): 59–64. http://dx.doi.org/10.4028/www.scientific.net/amm.86.59.

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This paper performs analyses and studies to a part of the foreign advanced helicopter transmission system technology. It introduces the design train of thought, main component structures and relevant parameters. It will give a reference to engineering technical personnel of the helicopter transmission system.

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Elasha, Faris, Matthew Greaves, and David Mba. "Planetary bearing defect detection in a commercial helicopter main gearbox with vibration and acoustic emission." Structural Health Monitoring 17, no. 5 (January 11, 2018): 1192–212. http://dx.doi.org/10.1177/1475921717738713.

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Helicopter gearboxes significantly differ from other transmission types and exhibit unique behaviours that reduce the effectiveness of traditional fault diagnostics methods. In addition, due to lack of redundancy, helicopter transmission failure can lead to catastrophic accidents. Bearing faults in helicopter gearboxes are difficult to discriminate due to the low signal-to-noise ratio in the presence of gear vibration. In addition, the vibration response from the planet gear bearings must be transmitted via a time-varying path through the ring gear to externally mounted accelerometers, which cause yet further bearing vibration signal suppression. This research programme has resulted in the successful proof of concept of a broadband wireless transmission sensor that incorporates power scavenging while operating within a helicopter gearbox. In addition, this article investigates the application of signal separation techniques in detection of bearing faults within the epicyclic module of a large helicopter (CS-29) main gearbox using vibration and acoustic emissions. It compares their effectiveness for various operating conditions. Three signal processing techniques, including an adaptive filter, spectral kurtosis and envelope analysis, were combined for this investigation. In addition, this research discusses the feasibility of using acoustic emission for helicopter gearbox monitoring.

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Krzymień, Wiesław, Michał Szmidt, and Sławomir Cieślak. "Vibration Properties of Steel Constructed Hospital Elevated Helipads." Transactions on Aerospace Research 2020, no. 3 (September 1, 2020): 11–20. http://dx.doi.org/10.2478/tar-2020-0013.

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AbstractPolish Medical Air Rescue helicopters facilitate the rapid transport of patients to large hospitals. The requirements of the space around the helipad and the safety of flight operations mean that hospitals closer to city centers create more elevated helipads than ground-based helipads. The helipads can vary in the way they are constructed and located - depending on the possibilities offered by hospital buildings and their surroundings.Vibroacoustics Laboratory of the Institute of Aviation measured the vibration properties of some elevated helipads. The goal of this research was to determine the vibration properties of the helipads itself and the transmission of vibrations to the construction of the helipads, the building and its equipment caused by the landing and taking-off of a helicopter.This article presents some of the results of measurements of vibrations of steel constructed elevated helipads with the use of a modal hammer and while landing and taking-off of a helicopter, as well as comparison of the vibration properties concerning various elevated concrete helipads.

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Asiri, S., A. Baz, and D. Pines. "Periodic Struts for Gearbox Support System." Journal of Vibration and Control 11, no. 6 (June 2005): 709–21. http://dx.doi.org/10.1177/1077546305052784.

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Passive periodic structures exhibit unique dynamic characteristics that make them act as mechanical filters for wave propagation. As a result, waves can propagate along the periodic structures only within specific frequency bands called “pass bands” and wave propagation is completely blocked within other frequency bands called “stop bands”. In this paper, the emphasis is placed on developing a new class of these periodic structures called passive periodic struts, which can be used to support gearbox systems on the airframes of helicopters. When designed properly, the passive periodic strut can stop the propagation of vibration from the gearbox to the airframe within critical frequency bands, consequently minimizing the effects of transmission of undesirable vibration and sound radiation to the helicopter cabin. The theory governing the operation of this class of passive periodic struts is introduced and their filtering characteristics are demonstrated experimentally as a function of their design parameters. The presented concept of the passive periodic strut can be easily used in many applications to control the wave propagation and the force transmission in both the spectral and spatial domains in an attempt to stop/confine the propagation of undesirable disturbances.

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Liu, Jian Wu, Shuai Wang, and Yong Hong Wang. "Helicopter Transmission System Technology Readiness Assessment." Applied Mechanics and Materials 86 (August 2011): 389–93. http://dx.doi.org/10.4028/www.scientific.net/amm.86.389.

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This paper states evaluative methods of technology readiness which are used in the national background projects development. The methods conduct helicopter transmission system technology maturity research and assessment of native significant project according to methods of technology readiness assessment. The conclusions indicate that methods of technology readiness assessment have very important promoting action to native project development and scientific decision-making. The project which adopts mature critical technology implies that guarantee the schedule of project development and reduce risk of project development. Actualizing assess methods of technology readiness can be an important part of project development risk management.

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Liu, Wei Zhen, Wen Qiang Ding, and Yong Hong Wang. "The Design Concept Application on RMS for Tail Drive System of Civil Helicopter." Applied Mechanics and Materials 86 (August 2011): 120–24. http://dx.doi.org/10.4028/www.scientific.net/amm.86.120.

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To raise the market competition ability of the civil helicopter, it is required to have high technical content in RMS including reliability, maintainability, safety, supportability and testability for the new generation civil helicopter. To meet the requirements of the civil helicopter, it is decided to follow strictly the maintenance matrix from the preliminary design phase of the transmission system. To decrease the maintenance cost, the structure will be optimized during the detail design phase and checked by DMU (Digital Mockup) in VPM (Virtual Product Model) system. And to get the high safety and reliability, some advanced design technical are applied and substantiated by some new test methods. This paper explains design concept application on RMS for tail drive system of the civil helicopter by showing some practice for an example. It can provide the method and reference for the development of civil helicopter transmission system.

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Hu, Baian. "Study on General Principle for Structure Fatigue Substantiation of Helicopter Transmission Systems." Applied Mechanics and Materials 86 (August 2011): 90–95. http://dx.doi.org/10.4028/www.scientific.net/amm.86.90.

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On the base of reading up the latest overseas certification specifications and integrating the experience of engineering practice, the requirement for structure fatigue substantiation of helicopter transmission system was expounded, and the related key concepts were explained in detail. Furthermore, the general method for structure fatigue substantiation was presented. Thus, the frame of general principle for structure fatigue substantiation of helicopter transmission systems was basically founded.

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Sharke, Paul. "Torque Take Off." Mechanical Engineering 122, no. 10 (October 1, 2000): 58–61. http://dx.doi.org/10.1115/1.2000-oct-1.

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This article focuses on that helicopters often display a rotor torque reading on their instrument panels to tell pilots how close they are flying to transmission design limits. With no measure of torque, a limit based on engine power is necessarily conservative. Torque monitors can increase a helicopter’s time between overhauls. Mechanical resonance, it seems, developed when the two engines were operated at matched torques. The torque meter lets the pilot split the torque to the two engines by 2 percent, diminishing any resonance. Permitted speculation, the Siemens researchers observed applications for their instrument beyond the traditional realm of torque measurement. In automotive applications, for instance, the researchers envision their torque measurement system one day being used in car engines to provide data in real time to the engine controls.

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Niinomi, Yutaka, and Toshiya Igarashi. "Plane antenna for helicopter relay transmission system." Journal of the Institute of Television Engineers of Japan 42, no. 10 (1988): 1128–30. http://dx.doi.org/10.3169/itej1978.42.1128.

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Coy, John J. "Effect of lubricant on helicopter transmission efficiency." Journal of Synthetic Lubrication 4, no. 1 (1987): 53–73. http://dx.doi.org/10.1002/jsl.3000040105.

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Augustyn, Sławomir, and Andrzej Gębura. "Capabilities of the FAM-C method to diagnose the accessory gearboxes and transmission -train assemblies of the MI-24 helicopters." Research Works of Air Force Institute of Technology 30, no. 1 (October 1, 2012): 199–220. http://dx.doi.org/10.2478/v10041-012-0012-2.

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The study has been intended to present some selected service-imposed issues with the transmission system of the Mi-24 combat helicopter. An attempt has been made to present predictions about possible threats/hazards to the transmission system of this helicopter. The forecast has been based on the FAM-C analysis of changes in instantaneous frequency against time and, to some extent, on mechanical measurements of disassembled structural components/subassemblies. The greatest emphasis has been laid on capabilities to identify and diagnose locations in structural components of the Mi-24 helicopter (where many and various hazards may arise) using the non-destructive diagnostic method FAM-C developed at ITWL (Air Force Institute of Technology). The method has been based on the tracking of parameters of modulation of airborne alternator produced frequencies. The testing requires no extra sensors, since the built-in airborne AC, DC, and tachogenerators themselves are the diagnostic transducers. While taking FAM-C measurements, the transmission system experiences no extra loads or rotational-speed distortions.

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Stanisławski, Jarosław. "A Simulation Model for Computing the Loads Generated at Landing Site During Helicopter Take-Off or Landing Operation." Transactions on Aerospace Research 2019, no. 2 (June 1, 2019): 59–75. http://dx.doi.org/10.2478/tar-2019-0010.

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Summary The paper presents simulation method and results of calculations determining behavior of helicopter and landing site loads which are generated during phase of the helicopter take-off and landing. For helicopter with whirling rotor standing on ground or touching it, the loads of landing gear depend on the parameters of helicopter movement, occurrence of wind gusts and control of pitch angle of the rotor blades. The considered model of helicopter consists of the fuselage and main transmission treated as rigid bodies connected with elastic elements. The fuselage is supported by landing gear modeled by units of spring and damping elements. The rotor blades are modeled as elastic axes with sets of lumped masses of blade segments distributed along them. The Runge-Kutta method was used to solve the equations of motion of the helicopter model. According to the Galerkin method, it was assumed that the parameters of the elastic blade motion can be treated as a combination of its bending and torsion eigen modes. For calculations, data of a hypothetical light helicopter were applied. Simulation results were presented for the cases of landing helicopter touching ground with different vertical speed and for phase of take-off including influence of rotor speed changes, wind gust and control of blade pitch. The simulation method may help to define the limits of helicopter safe operation on the landing surfaces.

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Yin, Mei, Jun Peng Qiu, and Jie Gao. "Preload Design of Bearings in Helicopter Transmission System." Applied Mechanics and Materials 86 (August 2011): 170–75. http://dx.doi.org/10.4028/www.scientific.net/amm.86.170.

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In order to reduce running noise and enhance the stiffness and accuracy of shaft guidance, the bearings often use preload design in some position of the helicopter transmission system. In addition, the preload design of the bearings can compensate for wear in the operation and provide long service life of the bearings. By expatiating on the effect, types, determination and adjustment procedure, it offers reference for the design of preload for bearings.

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Kolesnikov, V. I., P. A. Koropets, and E. S. Sinyutin. "Vibration-Based Diagnostics of Helicopter Transmission Gear Couplings." Russian Aeronautics 63, no. 1 (January 2020): 7–13. http://dx.doi.org/10.3103/s106879982001002x.

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White, G. "Design study of a split-torque helicopter transmission." Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering 212, no. 2 (February 1, 1998): 117–23. http://dx.doi.org/10.1243/0954410981532180.

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A helicopter transmission with split-torque drive trains to the main rotor and tail rotor drive shaft is described. A design based on two 1200 kW engines supplying torque to a 350 r/min main shaft demonstrates a weight reduction of 40 per cent, extreme low height and reduced losses. Four double-helical pinions drive a combining gear and provide a 10:1 reduction ratio to the main shaft; flexible torque tubes, set by fine-difference splines, control the division of torque between pairs of pinions. Rotor loads bypass the transmission housings and pass to the fuselage through a large-diameter mast that encloses an integral sump and cooler.

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Simmons, Richard, Paolo Dini, Nigel Culkin, and Giuseppe Littera. "Crisis and the Role of Money in the Real and Financial Economies—An Innovative Approach to Monetary Stimulus." Journal of Risk and Financial Management 14, no. 3 (March 20, 2021): 129. http://dx.doi.org/10.3390/jrfm14030129.

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‘Financial crisis’ is sometimes regarded as synonymous with ‘economic crisis’, but this is an oversimplification and risks missing the feedback loops between the financial and real economies. In this paper, the role of money is revisited in the context of distinguishing the real economy from the financial economy. A theoretical framework is developed to explain how endogenous (bank credit) and central bank exogenous (quantitative easing, QE) money creation feed into the real and financial economies. It looks at how the velocity of monetary circulation varies between the two economies and across asset types within the financial economy. Monetary transmission mechanisms are set into a framework that helps explain how QE stimulus risks combining asset price bubbles with poor growth in the real economy. The real economy transmission mechanism of ‘helicopter money’ is given context, enabling an assessment of the efficacy of both the QE and helicopter money policy routes. Finally, we present a new type of monetary transmission, ‘Smart Helicopter Money’, to deliver monetary stimulus to innovators, SMEs and high-growth firms via both complementary currencies and a modified form of QE in order to achieve proportionally greater impact on the real economy.

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Qiu, Jun Peng, Mei Yin, and Ling Song Guo. "Lubrication Mode and Selection of the Helicopter Transmission System Roller Bearing." Applied Mechanics and Materials 86 (August 2011): 156–61. http://dx.doi.org/10.4028/www.scientific.net/amm.86.156.

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The bearings will directly affect the performance of helicopter transmission system whether they are in normal work or not. Lubrication is the essential element for the normal work of bearings. Under the condition of the bearing design and manufacture technique, material technique is becoming more and more advanced, and lubricant becomes “the fifth main part”, which has been got a wide-ranged agreement. One of the most critical factors to improve bearing life is lubricant. This paper analyzes lubrication type and mode, and the failure of helicopter transmission system roller bearing caused by improper lubrication. It further explains the importance of lubrication to the bearings. And how to select lubrication mode and lubricant to improve the bearing life is also summed up.

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Deaconu, Marius, Grigore Cican, Adina-Cristina Toma, and Luminița Ioana Drăgășanu. "Helicopter Inside Cabin Acoustic Evaluation: A Case Study—IAR PUMA 330." International Journal of Environmental Research and Public Health 18, no. 18 (September 15, 2021): 9716. http://dx.doi.org/10.3390/ijerph18189716.

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This paper presents an inside-cabin acoustic evaluation of the IAR PUMA 330 helicopter, manufactured by IAR S.A. Brasov. In this study, based on the acoustic assessment inside the helicopter, areas with high noise levels are identified. In this regard, several tests were carried out in accordance with the ISO 5129 standard. In the first stage of the assessment, a measurement campaign was performed to identify the acoustic leaks from the outside noise sources propagating inside the cabin (in the door area) and the acoustic attenuation of the helicopter structure. These tests were performed on the factory runway, with the helicopter in parked position (ground tests). During the ground tests, the helicopter engines were turned off. The tests consisted of placing two loudspeakers directed towards the helicopter door and generating pink noise. Inside the helicopter, the entire door frame opening was scanned with an intensity probe to identify acoustic leaks areas. The second assessment stage was to determine the areas of the cabin with the highest levels of noise. Within the measurement campaign, 16 microphones were placed inside the cabin, at the level of the passengers’ heads, arranged in seven zones. The tests were carried out with the helicopter engines started, staying at fixed point above the ground (hovering), and then a flight test, in which all the maneuvers necessary for the use of the helicopter were performed (in-flight tests). Based on the measurement results, it was possible to highlight the noise spectral components in each of the seven areas. The noise assessment revealed high noise levels inside the cabin, having as main noise sources the transmission gear and the door area, leading to the need for reducing the noise exposure for passengers and crew, thus the need to reduce noise levels inside the helicopter.

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Brennan, M. J., R. J. Pinnington, and S. J. Elliott. "Mechanisms of Noise Transmission through Helicopter Gearbox Support Struts." Journal of Vibration and Acoustics 116, no. 4 (October 1, 1994): 548–54. http://dx.doi.org/10.1115/1.2930462.

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Helicopter gearbox support struts are structural members designed to take large compressive and tensile mechanical loads. They also act as vibration transmission paths connecting the major noise and vibration generators of the main rotor and gearbox to the fuselage and cabin. In this paper the mechanisms of vibration transmission through these struts are examined. The differences between the low frequency behavior that is important in the transmission of the rotor vibrations, and the high frequency behavior that is important in the transmission of gear noise are discussed. A flexible element is introduced in series with the strut, and the limitations of this simple passive measure in attenuating longitudinal and flexural vibrations are highlighted. The analysis shows that there is a difference in the mechanisms of vibration transmission between low and high frequencies, and that there are difficulties in applying effective passive vibration isolation measures to this system.

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Stanislawski, Jaroslaw. "A simulation investigation of helicopter ground resonance phenomenon." Aircraft Engineering and Aerospace Technology 91, no. 3 (March 4, 2019): 484–97. http://dx.doi.org/10.1108/aeat-11-2017-0256.

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Purpose The purpose of this paper is to present a simulation method applied for investigation of helicopter ground resonance phenomenon. Design/methodology/approach The considered physical model of helicopter standing on ground with rotating rotor consists of fuselage and main transmission gear treated as stiff bodies connected by elastic elements. The fuselage is supported on landing gear modeled by spring-damper units. The main rotor blades are treated as set of elastic axes with lumped masses distributed along blade radius. Due to Galerkin method, parameters of blades motion are assumed as a combination of bending and torsion eigen modes. A Runge–Kutta method is applied to solve equations of motions of rotor blades and helicopter fuselage. Findings The presented simulation method may be applied in preliminary stage of helicopter design to avoid ground resonance by proper selection of landing gear units and blade damper characteristics. Practical implications Ground resonance may occur in form of violently increasing mutual oscillations of helicopter fuselage and lead-lag motion of rotor blades. According to changes of stiffness and damping characteristics, simulations show stable behavior or arising oscillations of helicopter. The effects of different blade balance or defect of blade damper are predicted. Originality/value The simulation method may help to determine the envelope of safe operation of helicopter in phase of take-off or landing. The effects of additional disturbances as results of blades pitch control as swashplate deflection are introduced.

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Journal articles on the topic 'Helicopter transmissions'

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