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Agarwal N.K.,Hindustan Aeronautics Ltd HAL | Negi G.C.S.,Hindustan Aeronautics Ltd HAL
ARF 2015 - 4th Asian-Australian Rotorcraft Forum | Year: 2015

Aviation industries have always been looking forward for new developments with the objective to produce aircraft with less carbon footprint, improved performance, handling qualities and comfort. One of the important contributors to achieve the various desired benefits is "Flight Control System". In order to achieve these benefits, fixed-wing aircraft have been using Fly-by-Wire technology since 1960s and moved to latest Power-by-Wire technology through passing of conventional flight control actuation system technologies. However, when one looks at the rotary-wing aircraft, this is not so where still most of the in-service helicopters are flying with conventional mechanical or hydro-mechanical flight control system. The first rotorcraft could enter into service with this advanced technology only in early 2000s after a gap of more than three decades of use on fixed-wing aircraft. The chronology of fixed-wing and rotary-wing aircraft for use of digital fly-by-wire technology is well evaluated and presented here. This paper provides the various causes for slow progress in implementation of this advanced technology on rotorcraft and the same has been evaluated on various issues over the conventional hydro-mechanical system.

Subramanian K.,Hindustan Aeronautics Ltd HAL | Venkatesan C.,Indian Institute of Technology Kanpur
5th Asian-Australian Rotorcraft Forum, ARF 2016 | Year: 2016

In helicopters, the rotor blade structural dynamic characteristics play an important role in the overall performance of the vehicle, defined in terms loads, vibration and handling qualities. The placement of natural frequencies in flap and lag is a critical step in the design of a practical rotor blade. A systematic optimization procedure in the design of cross sectional variations of structural and inertial properties will greatly help in the design process. An optimization procedure developed for the placement of natural frequencies in a non-uniform rotor blade is presented in this paper. The first flap and the first lag natural frequencies are considered for the optimization. A single cell section is selected for the blade root cross section in this study. The wall thickness of the single cell section is selected as primary design variable. The secondary design variables, stiffness and structural mass properties are modelled as parametric equations of the primary design variable. In this work the constraints are imposed on minimum wall thickness to cater for axial stress due to centrifugal force. A gradient based method along with the interior penalty function is used for the optimization. To automate the complete optimization process, the optimization program is linked with the computational tools Cross Sectional Properties Evaluation (COPE ) and Structural Dynamics Analysis of Rotor Blade (SDAR). These codes are developed at Helicopter Lab of Aerospace Engineering department, IIT Kanpur and validated with experimental data. © 2016, American Helicopter Society International. All rights reserved.

Bhat R.R.,Hindustan Aeronautics Ltd HAL | Nandi V.,Hindustan Aeronautics Ltd HAL | Manohara V.,Hindustan Aeronautics Ltd HAL | Suresh S.V.,Hindustan Aeronautics Ltd HAL
Journal of Failure Analysis and Prevention | Year: 2011

Heavy damage was reported on the outer race and rolling elements of a ball bearing belonging to jet engine of a military aircraft. Flaking type of damage was noticed only at one particular location on the outer race of the bearing and on almost all the balls of the bearing. The inner race and the cage of the bearing were free from any damage. The chemistry, hardness, and microstructure of the bearing components met the specification requirements. In the actual engine assembly, the bearing was mounted on shaft of bevel gear. Careful examination of the inner diameter (ID) of the inner ring of the bearing revealed nonuniform contact marks. The contact marks were observed in the form of discoloration of the ID surface. The nonuniform contact was attributed to eccentricity caused by improper mounting of the bearing onto the shaft of the bevel gear. This resulted in preferential loading, causing flaking at one particular location on the raceway of the outer ring and damage to the balls of the bearing. Hence, it was concluded that the ball bearing had failed because of assembly error after the last repair of the engine. © ASM International 2011.

Venkaiah P.,Hindustan Aeronautics Ltd HAL | Avala R.,Hindustan Aeronautics Ltd HAL
IEEE MTT-S International Microwave and RF Conference 2015, IMaRC 2015 | Year: 2015

A pulsed power amplifier that achieves stringent spectral requirements at RF frequencies by significantly reducing the side band radiations using a squared cosine pulse modulation scheme is proposed. The scheme compliance the requirements of MIL STD 291C, an interface standard for Tactical Air Navigation, TACAN signal. The Squared Cosine baseband is generated using an FPGA by employing a Look-Up table based method. The digitally generated samples from FPGA are passed through a DAC followed by a reconstruction filter for its smoothening. High slew rate Opamp followed by a power MOSFET further amplifies the pulse level and current drive requirements, to implement drain modulation of GaN based RF power amplifier. The designs are tested on a developed board with integrated power amplifier in the frequency band of 1025MHz to 1150MHz in step of 1MHz. The test results are matching with theoretical and simulated results. © 2015 IEEE.

Nandi V.,Hindustan Aeronautics Ltd HAL | Bhat R.R.,Hindustan Aeronautics Ltd HAL | Yatisha I.N.,Hindustan Aeronautics Ltd HAL | Suresh S.V.,Hindustan Aeronautics Ltd HAL
Journal of Failure Analysis and Prevention | Year: 2012

One of the 12 screws meant to fasten the diffuser segment to the flange of a turbine casing in an aeroengine was found broken in-service. Cracks were also observed in some of the remaining screws. The screws made of 35NC6 steel material were plated with cadmium. The chemistry, hardness, and microstructure (heattreatment condition) of the screws met the drawing requirements. Heavy oxidation was noticed on the surface as well as on the fracture surface of the screws. Fractographic studies showed brittle intergranular features. Scanning electron microscope-energy dispersive x-ray spectroscopy (SEM-EDS) analysis detected cadmium on the entire fracture surface of the screws. Micro-examination and SEM-EDS analysis of the cracked screws showed the presence of cadmium all along the path of crack propagation including the crack tip. From microscopic and fractographic studies, it was concluded that the screws had failed by liquid-metal-induced embrittlement (LMIE). It appeared that the screws had experienced high service temperature that had resulted in melting of the cadmium plating on the screws. The molten cadmium had penetrated (adsorbed) along the grain boundaries of the screw material causing the screws to eventually fail in the brittle (intergranular) manner by the phenomenon of LMIE. © ASM International 2012.

Panda P.K.,National Aerospace Laboratories, Bangalore | Sahoo B.,National Aerospace Laboratories, Bangalore | Chandraiah M.,National Aerospace Laboratories, Bangalore | Raghavan S.,Hindustan Aeronautics Ltd HAL | And 3 more authors.
Journal of Electronic Materials | Year: 2015

Piezoelectric materials have a unique ability to interchange electrical and mechanical energy. This property allows the absorption of mechanical energy such as ambient vibration and its transformation into electrical energy. The electrical energy generated can be used to power low-power electronic devices. In the present study, energy harvesting by lead zirconate titanate (PZT) multilayer (ML) stacks and bimorphs is presented. The devices were fabricated by a tape casting technique and were poled at 2 kV/mm for 30 min immersed in a silicone oil bath maintained at 60°C. The energy harvesting characteristics of the fabricated devices were measured in a suitably assembled test setup. The output voltage obtained from the PZT bimorphs and ML stacks was 450 mV and 125 mV, respectively. The higher output voltage from the bimorph is due to its low capacitance. © 2015, The Minerals, Metals & Materials Society.

Vasantharaju C.,Hindustan Aeronautics Ltd HAL | Ashok B.,Aeronautical Development Agency ADA | Naiju C.D.,Vellore Institute of Technology
International Journal of Product Lifecycle Management | Year: 2015

To enhance performance effectiveness, the design of aircraft system and components must incorporate the radical technologies in all specialisations. As the technology advances, the corresponding complexity also advances. Hence, there is a need to design the aircraft systems and subsystems with components in such a manner to accommodate futuristic technologies and compress the design cycle times. In the present scenario, the aircraft parts are complex and have high interdependencies which make it difficult to identify and incorporate the technological advances in scheduled time line. Different management and model-based techniques such as PERT, CPM, multi-disciplinary optimisation (MDO), FEM, etc., were used for cycle time reduction. Markov process is a stochastic approach which is explored for the objectives of knowing the strength and weakness of the organisation and to reach the futuristic goals with available resources, thereby anticipating the futuristic technological changes and trying to fulfil mission requirements at design stage itself. In this paper, Markov chain approach is illustrated for cycle time reduction with a typical case study for military aircraft sub assembly. Copyright © 2015 Inderscience Enterprises Ltd.

Vasantharaju C.,Hindustan Aeronautics Ltd HAL | Ashok B.,Aeronautical Development Agency ADA | Naiju C.D.,Vellore Institute of Technology
ARPN Journal of Engineering and Applied Sciences | Year: 2014

The design of Aircraft and especially the fighter Aircraft is increasingly getting complex. Added to the complexities of the design and need to integrate several disciplines, there is an added challenge of working with technologies that are still in drawing boards to be incorporated in future design. Needless to add, validation and testing of entire system / subsystem is a pain point. Hence there is a clear need to design the aircraft in such a manner to accommodate for futuristic technologies and compress the design cycle times. On an average, design and development of a Military aircraft either for developed countries or developing countries requires a minimum of 13 years from the launch of project to the first flight. As the years get passed on new technologies and advancement also develops and it will become difficult to identify and incorporate to the ongoing projects. A novel approach of using Markov process for achieving these objectives is explored. Markov based approach as a stochastic approach normally used to predict future states on the basis they have no link to the past is explored. A step by step approach by taking a typical design life cycle process of a particular component/assembly of aircraft is discussed. In this, design is split in to sequential stages, based on our prior design experience a probability is assigned to all foreseeable possibilities, and then that is converted to transition probability. Using a simple concept that any probability less than 1.0 leads to extended design life cycle, suitable cost and time factors. © 2006-2014 Asian Research Publishing Network (ARPN).

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