Light Combat Aircraft Research Articles

India’s Quest for Defence Indigenisation: A Case Study of the Indian Navy

India, like all major military powers, has been making sustained attempts at indigenously meeting its defence requirements. However, when one looks at the macro picture, it is apparent that the country has had limited successes in inducting defence platforms or weapon systems that are indigenously designed, tested, manufactured and inducted into the military. There have been some exceptions to this like the HF-24 Marut fighter jet, the Light Combat Aircraft Tejas, the Main Battle Tank Arjun, Leander class frigates, Indigenous Aircraft Carrier Vikrant, Kolkata and Vishakhapatnam class destroyers and the Arihant nuclear submarine. While these examples only prove the general rule, they also point out India’s relative success in creating domestic capacity to build naval platforms. As India embarks on the path of Atmanirbharta (self-reliance), it is crucial for the political and military decision-makers to understand what, why and how the above-mentioned projects, particularly the naval ones, became successful, so that their success can be replicated elsewhere. The article attempts to understand the reasons behind the Navy’s successes. These successes have been the result of an institutionalised—as opposed to an individual-centric—approach by the Navy to create in-house design capabilities, organisational structure, planning procedure, capacity building efforts and linkages with other stakeholders like naval Defence Public Sector Units, Defence Research and Development Organisation and other scientific establishments and industry. This has made the Indian Navy more successful as compared to the other two services of the Indian military when it comes to designing, testing, constructing and inducting indigenous naval platforms.

Aerospace Technologies: A Walk Through and Dreams Ahead

This paper deals with the highlights of the progress made within the country and in particular by Aeronautical Development Agency (ADA) n the various fields of the fighter aircraft technologies and the road map ahead. Many technologies have been developed successfully and incorporated in making of Light Combat Aircraft (LCA). The recent technology developments in the field of aeronautics have made the new generation fighter aircrafts more efficient, lethal and combat effective. India also needs to keep its pace with advancing technology. It requires enormous amount of effort from the scientific and engineering community in India to keep the pace with advancing technology. In this perspective, ADA in collaboration with DRDO and other organizations has initiated R&D activities for the development of these demanding technologies required in the future fighter aircrafts. This paper discusses some of the important technologies already developed and incorporated in LCA and some other ongoing technology developments. Finally it deals with the identification of future technologies essential for future aircrafts and efforts being put in by ADA in realizing these technologies in a foreseeable future.

Advanced Simulation Technologies and Testing Methodologies Applied in the Design and Development of Aero Gas Turbine Engines

An overview of Gas Turbine Engine Development, KAVERI, the power plant for the Light Combat Aircraft (Tejas) and a description of the validated numerical tools, aerothermodynamic and mechanical test facilities of the Gas Turbine Research Establishment (GTRE) are presented. The KAVERI engine compressor, combustion system, turbine, analytical tools, blade heat transfer, exhaust system, Integrated Nozzle Actuation System (INAS), Non-intrusive Stress Measurement System (NSMS) and thermal paint tests are described in detail.

Investigation of Fin Buffet Characteristics of a Developmental Combat Aircraft Through Wind Tunnel Experiments

Airframe buffet is an important dynamic problem associated with combat aircraft flight, especially in the high Angle-of-Attack (AoA) regime. Occurrence of buffet due to flow separation at high angles of attack needs to be structurally cleared and a buffet boundary needs to be established. The methodology adopted to clear the aircraft from buffet during high AoA flight testing of a developmental light combat aircraft is focused in this article. Experimental unsteady pressure data from low speed wind tunnel tests conducted on a scaled down (1:10) model and airframe especially fin vibration data measured from flight tests formed the basis for this methodology. The reference spectrum has been formulated through unsteady pressures measured using pressure transducers mounted on the fin of the wind tunnel model. This spectrum (scaled up to 1:1) i.e. pressure Power Spectral Density (PSD) excitation was used as an input to the FE model of aircraft fin mounted on the rear fuselage. Buffeting response predicted in terms of acceleration PSD on the fin and rudder have been compared with the flight measured acceleration PSD data to validate the numerical model. The validated model is used to predict loads to clear the aircraft for further flight envelope expansion at high AoA.

Feasibility study of FSW, LBW and TIG joining process to fabricate light combat aircraft structure

In this research, friction stir welding (FSW), laser beam welding (LBW) and tungsten inert gas (TIG) welding are used to join precipitation hardening aluminum alloy 2014-T6. This alloy is a potential candidate in heavy structural fabrication industries due to strength ratio. However, the joining of this alloy is a major problem in assembly line. Hence, to find an ideal method for welding this alloy, three processes were compared in terms of mechanical and metallurgical properties of welded joints. Results showed that the FSW joints disclosed better strength than other LBW and TIG joints. In comparison to LBW and TIG joints, FSW conceived narrow heat-affected zone and recorded maximum hardness of 135 VHN. Similarly, the maximum hardness in the LBW and TIG welded joints were 110 VHN and 92 VHN respectively. The reason for maximum strength in FSW joints is the finer size and uniform distribution of strengthening precipitate. (Particle size diameter of 39 nm, thickness of 29 nm).

Designer Solid Shims for Assembly of Advanced Carbon Composite Pre-preg based Aircraft Structures

A modern combat aircraft uses considerable amount of advanced composite material in structure build for better flight performance, stealth requirement and higher payload. Combat aircrafts made using composite structure require large numbers of custom shims of various thickness and shapes throughout interface surface, which are presently prepared by suit on assembly process to fill gaps measured between sub-structure parts and skin. The scope of study is four plus generation combat aircraft like Indian Light combat aircraft. These gaps arise due to composite raw material characteristics, mould tool and manufacturing process which results in geometry variation. This research has focussed the delta wing integral fuel tank composite structure. However, these research findings can be applied in other wing shapes made by composite part within the scope. The shims, whether liquid or solid, are necessary to eliminate gaps, maintain structural performance and minimize pull-down forces required to bring the aircraft into engineering nominal configuration for aerodynamic efficiency. Customized shims amount to significant delays in production with much of the time being spent in the critical path of the aircraft assembly. In this research work, we present an alternative strategy for the use of designer solid shim, based on redesign of lay-up moulding tool (female type) and shims manufacturing with change in existing manufacturing value stream. The experimented method has reduced the manufacturing cost of wing assembly, shorten the shimming process cycle and improve the assembly efficiency, product quality and performance.

Structural Life Management in a Combat Aircraft

The paper briefly describes some of the underlying concepts, issues and strategies for ensuring efficient management of structural integrity of an airframe throughout the useful life of an aircraft—especially that of a military combat aircraft. Much of the discussion in the paper is based on the experience of the authors during the design and development phase of the Indian light combat aircraft, namely, LCA Mk-I Tejas, and the information available about the LCA in the open literature or public domain. Even though not an ageing aircraft, LCA is taken as an example to facilitate bringing out various issues and strategies to resolve them, particularly with relevance to the Indian aeronautical scenario. The use of both metallic and composite materials in modern combat aircraft structures necessitates different design strategies to be adopted for their structural integrity throughout their lifetime. In this respect too, the LCA serves as a good example. Within the limited scope of the paper, the description and discussions are primarily limited to some of the important aspects, such as the fatigue degradation in metallic materials and impact damage in composites—which do form the bulk of the effort of life management of airframe structures. Other issues such as corrosion in metals and environmental degradation in composites are also briefly mentioned. A brief description of the aircraft and its structure is given initially. Major steps in designing for structural life management, such as, estimation of static loads, derivation of fatigue spectra for the intended usage, degradation through fatigue or impact damage, lifing philosophies, estimation of life and monitoring of health and usage of individual aircraft are described. A brief mention is also made about structural health monitoring (SHM) as a future direction in life management. It is expected that the exposition in the paper will help understand issues and strategies that would eventually be required as a combat aircraft gets aged in service.

Janus – A New Approach to Air Combat Pilot Training

Abstract Advanced jet training still relies on old concepts and solutions that are no longer efficient when considering the current and forthcoming changes in air combat. The cost of those old solutions to develop and maintain combat pilot skills are important, adding even more constraints to the training limitations. The requirement of having a trainer aircraft able to perform also light combat aircraft operational mission is adding unnecessary complexity and cost without any real operational advantages to air combat mission training. Thanks to emerging technologies, the JANUS project will study the feasibility of a brand-new concept of agile manoeuvrable training aircraft and an integrated training system, able to provide a live, virtual and constructive environment. The JANUS concept is based on a lightweight, low-cost, high energy aircraft associated to a ground based Integrated Training System providing simulated and emulated signals, simulated and real opponents, combined with real-time feedback on pilot’s physiological characteristics: traditionally embedded sensors are replaced with emulated signals, simulated opponents are proposed to the pilot, enabling out of sight engagement. JANUS is also providing new cost effective and more realistic solutions for “Red air aircraft” missions, organised in so-called “Aggressor Squadrons”.

Evaluation of load-carrying capabilities of friction stir welded, TIG welded and riveted joints of AA2014-T6 aluminium alloy

PurposePresently, the materials used in light combat aircraft structures are aluminium alloys and composites. These structures are joined together through riveted joints. The weight of these rivets for the entire aircraft is nearly one ton. In addition to weight, the riveted connection requires a lot of tools, equipments, fixtures and manpower, which makes it an expensive and time-consuming process. Moreover, Al alloy is also welded using tungsten inert gas (TIG) welding process by proper control of process parameters. This process has limitations such as porosity, alloy segregation and hot cracking. To overcome the above limitations, an alternative technology is required. One such technology is friction stir welding (FSW), which can be successfully applied for welding of aluminium alloy in LCA structures. Therefore, this paper aims to compare the load carrying capabilities of FSW joints with TIG welded and riveted joints.Design/methodology/approachFSW joints and TIG welded joints were fabricated using optimized process parameters, followed by riveted joints using standard shop floor practice in the butt and lap joint configurations.FindingsThe load-carrying capabilities of FSW joints are superior than those of other joints. FSW joints exhibited 75 per cent higher load-carrying capability compared to the riveted joints and TIG-welded joints.Practical implicationsFrom this investigation, it is inferred that the FSW joint is suitable for the replacement of riveted joints in LCA and TIG-welded joints.Originality/valueFriction stir butt joints exhibited 75 per cent higher load-carrying capability than riveted butt joints. Friction stir welded lap joints showed 70 per cent higher load-carrying capability than the riveted lap joints. Friction stir butt joints yielded 41 per cent higher breaking load capabilities than the TIG-welded butt joints. Moreover, Friction stir lap weld joints have 57 per cent more load-carrying capabilities than the TIG-welded lap joints.

Conceptual Study on Integration of Engine Health Monitoring (EHM) System with Integrated Vehicle Health Monitoring (IVHM) System

AbstractAn approach to upgrade existing control system and lean architecture principle is presented to optimize the system along with reduction of weight by understanding the physical system design, Engine Health Monitoring (EHM) system and data study from Integrated Vehicle Health Monitoring (IVHM) system (Aaseng n.d.). This paper brings out the integration of EHM sufficiency with IVHM system. Research effort to describe the hardware, software, algorithms and engine parameters required to monitor various events capturing, health and life management issues with IVHM. Here basic functionality will be performance monitoring, vibration monitoring, event monitoring (including stall, surge, over speed, flameout, over temperature, oil parameter and life monitoring) anti ice system with IVHM requirement of mission completion, safety and data protection.A systematic SE approach and methodology with need and requirement is generated using DOORS software (INCOSE 2011). Full requirement capture with engine designer and aircraft designer (Harinarayana, Developing light combat aircraft: foresight as the guiding principle 2004) for integrating with IVHM (Philip A. Scandura October 30, 2005)has been studied and brought out to model the concept using Rhapsody software. Here various operational scenarios has been attempted to make the functional model. Functional model has been tested for various operational issues and a final configuration has been proposed to the designer (Jaw, Van and Mink 7 – 10 May 2007). This study has brought out a perspective work model for a designer and as a result of this the final product will be tested for integrating the EHM with IVHM

An Overview of High-Performance Aircraft Structural Al Alloy-AA7085

AA7085 Al alloy is a new-generation, high-strength, quench-insensitive alloy that features in airframe applications such as massive bulkhead and wing spars structures in Airbus A380 and Joint Strike Fighter aircrafts. This alloy has a great potential in replacing currently used high-strength AA7xxx alloys in many international and national military aircraft programs [Hawk, Su-30, MiG series, light combat aircraft (Tejas), Hindustan turbo/jet trainer, light combat helicopter, advanced light helicopter, and fifth-generation fighter aircrafts]. An effort has been made to highlight the processing, heat treatment, properties and applications of the AA7085 Al alloy from the existing literature on the AA7085 alloy. The potential applications of this alloy are presented and compared with the currently used AA7075 Al alloy. A typical process cycle involved in the manufacturing of wrought AA7085 alloy products is described in detail. Particularly, the precipitation mechanisms involved in the different temper conditions are critically reviewed with the supporting microstructures. The mechanical properties with a particular emphasis on tensile, fatigue, and fracture toughness properties are discussed in detail based on the analysis of experimental data. The effects of temper conditions on the stress corrosion cracking and exfoliation corrosion have also been reviewed critically.

Clearance of Flight-Control-System Software with Hardware-in-Loop Test Platform

The Indian Light Combat Aircraft has flown more than 2000 flights, including trainer and naval variants, without encountering any major faults in the flight safety-critical fly-by-wire control software. This is partly due to the stringent quality control and rigorous testing of the control-law and air-data-system algorithms carried out on various ground platforms before flight. One of these ground test platforms is the hardware-in-loop test platform (Iron Bird). The processing of tolerance bounds to define the pass/fail criteria is an algorithmic development. It guarantees the correctness of the modules, if the set of inputs generates a set of outputs within processed tolerance bounds. This paper presents the philosophy behind the design of test cases and the tools developed to evaluate the control-law and air-data-system modules on the Iron Bird platform, and the procedure to clear the test results. The computation of tolerance bounds and algorithms for their processing have been evolved over a period based on several criteria, testers’ experience, and the experience gained during various levels of testing of air-data-system and control-law algorithms. This process yielded excellent results, and is accepted as a formal clearance methodology for the onboard safety-critical fly-by-wire system software.

Application of System Identification Techniques to Tejas Flight Test Data

Tejas, the Indian Light Combat aircraft, is a fly-by-wire aircraft with relaxed longitudinal stability that provides for enhanced agility, high maneuverability and performance. The aircraft is presently undergoing extensive flight test trails and the flight data gathered is being used by various design groups to evaluate aircraft systems, performance and aerodynamic characteristics. This paper gives an overview of the application of system identification techniques to Tejas flight test data for validation and update of the aircraft aerodynamic database. The aerodynamic characterization is carried out using two different approaches i) point model identification, and ii) coefficient level matching. Typical results are presented from both the approaches along with the time history plots from the flight updated aero database. The main purpose of this paper is show to how system identification techniques can lead to accurate determination of aerodynamic characteristics from flight test data.

Experimental and Analytical Investigation of Drilling of Sandwich Composites: A Review

A composite material is made out of a mixture or a combination of two or more distinctly differing materials which are insoluble in each other and differ in form or chemical composition. The technological and commercial interest in composite material lies in their superior properties of strength-to-weight, stiffness-toweight, fatigue and thermal expansion compared to metals. Extensive use of composite in application such as rockets, satellites, missiles, light combat aircraft, advanced light helicopter and trainer air craft has shown that India is on par with the advanced countries in the development and use of composites in this area. Drilling is probably the most important conventional mechanical process and it is the most widely used machining operation. Prediction of cutting forces for any set of cutting parameters is essential in optimal design and manufacturing of products. It has been predicted that most of the problem associated with hole making operation, such as drilling, can be attributed to the force generated during cutting operation. Many developments and experiments are going on drilling of Sandwich composite for damage free drilling along with the quality of the hole and the effect of tool geometry and tool material. This paper aims at the comprehensive analytical and experimental investigation work done on the composites material. The conclusion of the paper discusses the development and outlines the trends for the research in this field.

Managing Complexity in Aircraft Design Using Design Structure Matrix

Modern aerospace systems have reached a level of complexity that requires systematic methods for their design. The development of products in aircraft industry involves numerous engineers from different disciplines working on independent components. Routine activities consume a significant part of aircraft development time. To be competitive, aircraft industry needs to manage complexity and readjust the ratio of innovative versus routine work. Thus, the main objective is to develop an approach that can manage complexity in engineering design, reduce the design cycle time, and reduce the product development cost. The design structure matrix (DSM) is a simple tool to perform both analysis and management of complex systems. It enables the user to model, visualize, and analyze the dependencies among the functional group of any system and derive suggestions for the improvement or synthesis of a system. This article illustrates with a case study how DSM can be used to manage complexity in aircraft design process. The result of implementing the DSM approach for Light Combat Aircraft (Navy) at Hindustan Aeronautics Limited, India, (in aircraft design) show primary benefits of 75% reduction in routine activities, 33% reduction in design cycle time, 50% reduction in rework cost, and 30% reduction in product and process development cost of aircraft.

LCA in New Zealand

In 2004, when I started doing LCA work in New Zealand, “LCA” was hardly a known term in New Zealand. A Google search confirmed this and suggested “Light Combat Aircraft”, “Lutheran Church of Australia” or “Legalise Cannabis Alliance” as possible explanations.... Things have changed quite a bit since then! While we admittedly had some catching up to do in terms of adopting Life Cycle approaches, other examples have shown New Zealand to be recognised as a very progressive country, for example, by being the first selfgoverning country in the world to grant all women the right to vote. Some other Kiwi inventions are the electric fence, the disposable syringe, bungee jumping and the first use of a whistle by a referee to end a sporting game. The pragmatic “Kiwi can do” attitude has helped us to make significant progress, and Life Cycle Management, Life Cycle Assessment and Carbon Footprinting are now well established and progressing very fast in New Zealand. As Professor Roland Clift commented after his recent visit to New Zealand “I am seriously impressed by the level of activity and professionalism in LCA and Life Cycle Management (LCM) in New Zealand—it is a model to which others might well aspire.... I was struck by the determination of your members to produce practically useful results but remain methodologically rigorous. It’s a commendable record.” In this editorial, I would like to provide an overview of the development of Life Cycle Association of New Zealand (LCANZ) and its achievements and current activities as well as some notable additional activities in the area of LCA/LCM in New Zealand.

Automated Aircraft Sheet Metal Component Production Technologies

This article comprehensively presents an overview of the technological advances in automated aircraft sheet metal component production technology developments due to the initiative by the Aeronautical Development Agency, Ministry of Defense, Government of India, since 1989 in collaboration with the Indian Institute of Technology, Bombay. Commencing with a modest computer-aided flat pattern development software system suitable for a class of sheet metal components, this activity after several stages of development has now resulted in the development of full-fledged, personal-computer-based graphical interactive, three-dimensional application flat pattern development and automated production loft generation system. This research, encompassing the practical methods (exclusively developed for flat pattern software), literature survey, development of key algorithms suitable for designing a system for automated loft generation for a variety of surfaces with complex geometric features characteristic of aircraft sheet metal components with the aid of a wide choice of surface model creations, and testing and validation (carried out through an associated aircraft factory, Hindustan Aeronautics Limited), is now being published through four full-length papers concluding with the present paper. In fact, comprehensive illustrations of production lofts sampled from over thousands of parts used in the factory pertinent to the Indian Light Combat Aircraft (termed as Tejas) and other projects like Advanced Light Helicopter (termed as Dhruv) sheet metal components are included here to provide insight into these developments, and also to provide a glimpse of the success of the mission of indigenous automated aircraft sheet metal component manufacture.

Project 'Kaveri' an approach to concurrent product development

Technology development is fast becoming a critical input for the progress of any nation. The technologies developed should be globally competitive and timely to be relevant to the present international scenario. Most of the current technologies need to be developed within reduced time and with the least developmental costs for the same reasons. In this context, alliances assume greater significance than ever before. The development of viable leading-edge technologies need the highest level of intellectual and technical inputs. Hence, the optimal use of resources in public/private organisations/academic institutes and the appropriate synergy among these institutes will contribute a very significant role (Ramachandra, 1999). India's Defence Research and Development Organisation is developing the 'Kaveri' engine for Light Combat Aircraft (LCA), christened as 'TEJAS'. Spin-offs would be used for many civil applications. In a nutshell, this paper illustrates the effectiveness of the concurrent engineering strategy adopted towards collaborative approach among the government, industry and academic institutions to meet the development time and cost (Das and Ghosh, 2003).

Concurrent engineering for the development of advanced composites technology for light combat aircraft

This case study of light combat aircraft illustrates the use of concurrent engineering principles to enhance manufacturability and to reduce development cycle time. Use of composites has helped in realising an aircraft that is small, light, cost effective and easily manufacturable. Concurrent engineering helped simultaneously in reducing the cycle time, improving manufacturability, reducing parts count and improving the case of upgradability. This was possible though high level of horizontal coordination.

Developing light combat aircraft: foresight as the guiding principle

The Light Combat Aircraft is the smallest, most lightweight multi-role fighter of its class in the world. It uses state-of-the-art technologies. The aircraft development involved a disciplined and structured approach using the virtual organisation concept. An integrated team consisting of members from industry R&D institutions, customers and academia worked towards the realisation of the aircraft. Foresight helped in conceiving the challenging task, identifying a young team and providing a flexible organisational set-up. The cycle time for development was reduced using a distributed knowledge creation mode intermediated by organisational trust.