Vojnotehnicki glasnik / Military Technical Courier

11-24

Authors: Sokolović Vlada S., Marković Goran B., Dikić Goran D.

In GPS receivers, navigation bit allocation is performed throughout the process of signal tracking and detection. In the process of signal tracking, the locally generated signal must be synchronized with the received signal. The Costas phase-locked loop (PLL) behavior, which is often used for signal synchronization, is characterized by dominant tracking error sources. The resulting phase tracking errors are significant in the presence of weak signals, i.e. signals with the low signal-to-noise ratio (SNR). In order to improve the signal synchronization and enable signal tracking by the receiver, we here proposed the usage of a non-data-aided (NDA) phase estimator. Based on the practical processing of the GPS signals, it is shown that the applied NDA algorithm is more resistant to sudden changes in frequency (phase) of the input signal than the previously considered phase discriminator in the Costas PLL. Also, we have shown that the solution analyzed here exhibits more stable operation in signal tracking for a low SNR.

46-67

Authors: Mrdak Mihailo R.

The physical and mechanical properties of coatings are heavily influenced by the technologies of powder production and by the parameters of the plasma spray process. One of the most important parameters that affects the physical and mechanical properties of coatings is the morphology of powder particles - homogeneity, granulation and granulation range, directly related to the technologies of powder production. This paper describes the technological processses of powder production most commonly used and shows the SEM micrographs of powder morphologies. Depending on the manufacturing process, powder particles have different characteristics regarding their shape, size, specific gravity, purity, etc. Since these characteristics have a significant impact on the quality and properties of deposited coatings, it is necessary to possess knowledge about the characteristics of powders in order to better control the behavior of particles in the plasma jet, in order to produce the expected characteristics of the coating. Powders have a variety of characteristics to be set for the operating parameters of the deposition in order to obtain the desired coating characteristics.

99-115

Authors: Ketu Nabil S., Demić Miroslav M., Muždeka Slavko R., Krsmanović Milan M.

This paper contributes to the modeling of a semi-active control of a quarter vehicle model using air springs. A conventional mass-spring-damper model has been used along with an air spring. Based on the theory of thermodynamics, the dynamic equation of the air spring model was established. The simulation model was implemented using MATLAB and the transfer functions with varying parameters were calculated. The simulation results show that air spring pressure, the valve diameter, the dumping coefficient and the mechanical stiffness affect the dynamic response of the system. A semi-active control methodology was then established by controlling the valve diameter using two declinations of an on-off logic switch based on the velocity of the suspended mass and the relative velocity at both ends of the air spring. The obtained results show reduced oscillation amplitudes around the natural frequency of the system.

135-165

Authors: Stojanović Dejan S.

The research goal is to enable prediction of events in the incoming period on the basis of a large number of collected relevant data that may represent a potential risk and the danger of ordnance explosion effects in the Army of Serbia. The realization of the objectives of the research requires the use of appropriate methods and techniques for dating and study of existing teoretical and practical solutions as well as proposing new ones in the areas of interest. During the research, the following scientific methods were used: comparative method, content analysis and positivist method. The investigation has covered situations which may arise at workplace due to various threats caused by both the human factor and chains of events, followed by the identification of potential forms of risk to people and property by ordnance explosion effects in the Army of Serbia. The collected data on potential forms of endangering people and property by ordnance explosion effects were analysed and their positive and negative consequences were discussed. The levels of safety risks to people and property from ordnance explosion effects are assessed and decisions are made about the forms of threat and to what extent they will be dealt with in the future.

192-214

Authors: Kovačević Nenad V.

After the re-admission of the Republic of Serbia to the United Nations (UN), members of the Ministry of Defence ( MoD) and the Serbian Army Forces (SAF) have been engaged in multinational operations (MNOP). The first engagement of three military observers was in UN MNOP in East Timor (UNMISET) from 26.06.2002. Until the closing of the mission, there were five members of the MoD and SAF engaged. Currently, there are 247 members of the MoD in 10 UN MNOP worldwide, engaged in different roles. During UN multinational operations, one of the key problems is posed when encountering some kind of explosive ordnance (referred to in the article as MES). In order to avoid consequences of improper explosive ordnance handling, full attention has to be paid to prevention, i.e. good preparation, During the preparation of MoD and SAF members to be sent to UN MNOP, the main problems concern professional staff (a small number of qualified and trained instructors) and necessary literature. The paper presents a review of the currently available literature and the experience of the MoD and SAF members who were engaged in UN MNOP in dealing with explosive ordnance, notably mines.

11-28

Authors: Danijela D. Protić

This paper presents the training, testing and pruning of a feedforward neural network with one hidden layer that was used for the prediction of the vowel ”a”. The paper also describes Gradient Descent, the Gauss-Newton and the Levenberg-Marquardt optimization techniques. Optimal Brain Surgeon pruning is applied to the trained network. The stopping criterion was an abrupt change of the Normalized Sum Squares Error. The structure of the feedforward neural network (FNN) was 18 inputs (four for glottal and 14 for speech samples), 3 neurons in the hidden layer and one output. The results have shown that, after pruning, the glottal signal has no effect on the model for a female speaker, while it affects the prediction of the speech pronounced by a male speaker. In both cases, the structure of the FNN is reduced to a small number of parameters.

42-62

Authors: Marija Z. Malnar, Nataša J. Nešković

WMNs (Wireless Mesh Networks) represent a new trend in wireless communications, providing greater flexibility, reliability and better network performances than standard WLANs (Wireless Local Area Networks). Having in mind a need for more efficient and faster data transmission, one of the greatest challenges in designing WMNs is to provide greater throughput. This is done by introducing networks the nodes of which have multiple interfaces that can work on one of multiple channels (the channel is chosen by a predefined algorithm), so-called Multi-Channel Multi-Interface (MCMI) WMNs. In order to provide better network performances, it is necessary to define routing protocols and metrics used to find and select the optimal route from the source to the destination node. Since WMNs are characterised by a high dynamic range of the received signal level, especially when they are realized in complex environments such as indoors, it is necessary to define routing metrics that can follow these fast changes in propagation conditions that occur in each link in the network.

87-113

Authors: Vojkan M. Radonjić, Slobodan R. Đukić, Danko M. Jovanović, Saša M. Petrović

This paper deals with an analysis and a comparison of the reliability of two types of special-purpose devices used in radio-relay systems. Based on the results of the analysis and the experience in top-level domains device maintenance, this paper proposes a modernization method of the existing analog radio-frequency filter with an appropriate digital filter. The proposed modernization of the technological process improves the characteristics of maintainability, increases reliability in performance while dramatically reducing the cost of equipment maintenance.

137-159

Authors: Mihailo R. Mrdak

Plasma is an electrically conductive gas containing ions, electrons and neutral molecules. This state of matter is created by an electrical discharge and can be maintained at steady state by introducing alternating or direct current. The paper describes the structure of plasma, the thermodynamic characteristics and a method of creating plasma that allow the application of plasma as a source of energy for plasma spray processes. In general, all existing materials in a form of powder may be deposited by plasma coating on the surfaces of various materials. At high temperatures, powder material particles are introduced into a conductive plasma gas, melting and accelerating to the substrate to form coatings. The wide use of plasma spray coatings in all industrial areas is of particular importance, because different combinations of surface layers can significantly increase the resistance of machine parts to: wear, abrasion, erosion, cavitation, corrosion and fatigue resistance at low and elevated temperatures with increased resource and reliability of the parts in service.

176-199

Authors: Srboljub J. Marinković, Aleksandar Ž. Drenovac

Aircraft maintenance, as a specific field of military materiel maintenance, is characterized by high reliability standards, based on regulations and technical standards. A system approach to maintenance represents the key element of maintenance quality, while aircraft maintenance staff has a crucial influence on the final outcome of aircraft maintenance.

215-239

Authors: Dejan R. Inđić, Miroslav R. Terzić, Stevan V. Žigić, Srđan Z. Rutić

Nuclear and chemical accidents in modern society often cause devastating consequences to people, material resources and the environment. This kind of accident requires special procedures and activities during the elimination of the consequences, because of the specific characteristics of highly toxic substances used in nuclear and chemical plants. The Serbian Army with its units and organizations can contribute significantly to the implementation of tasks of eliminating the consequences of such accidents. The paper describes the role and the tasks of the Serbian Army as well as one of the methods to utilize its units to provide assistance to the population in case of nuclear and chemical accidents.

262-277

Authors: Mladen R. Tišma

- Russia to relaunch production of Tu-160 strategic bombers; - Italian Air Force presented a new aircraft for selective and initial training; - China is developing fifth generationSTOVL fighter aircraft; - South Africa’s Denels consider restarting production improved attack helicopters; - Successful first flight of S-97 Raider helicopter; - India to modernize and arm Hawk Mk 132 trainer aircraft; - Public presentation and the first flight of An-178 transport aircraft; - Indian Air Force handed over the first modernized Mirage 2000; - Introduced a new version of the Israeli Air Force missiles i-Derby; - Talks about the possibility of equipping FA-50 light fighters with Al-Tarik precision guided munition; - Sagem offers the arming of French C-130 transport aircraft with precision guided bombs; - India has selected the A330 to develop a new AWACS; - The Brazilian navy took the first modernized AF-1 strike fighter; - Russia plans to build a new aircraft carrier.

282-303

Authors: Nikola M. Ostojić, Nebojša N. Gaćeša

Glory and power of Russian weaponry at the parade commemorating the 70th anniversary of Victory Day.

9-29

Authors: Leonid I. Gretchihin

The article describes the formation of the cluster grid structure of semiconductor crystals of A3B5 type.The deformation of the electron shells of the atoms in semiconductor crystal structure elements has been presented. Crystals of the Indium compounds and the elements from Group 5 of the Mendeleev periodic table have been used to show the energy levels where a semiconductor quantum generator is generated. The technological conditions for an A3B5 type laser realisation have been defined.

47-63

Authors: Mihailo R. Mrdak

This paper analyzes vacuum plasma spray VPS - Cr3C2 - 25(Ni20Cr) coatings. Commercial powder marked Sulzer Metco Woka 7205 is used. The powder is deposited with a plasma gun F4 at a distance of 340 mm from the substrate. The main objective of the study was to eliminate, at the reduced pressure of inert gas Ar, the degradation of primary Cr3C2 carbide into Cr23C6 carbide which significantly reduces the microhardness and mechanical properties of the coating. The coating is deposited with a thickness of 100 - 120 µm on a steel substrate. The microhardness of the coating was tested by HV0.3. The microhardness values were in the range of 1248 - 1342 HV0.3. The bond strength of the coating was tested by tension. It was found that the bond strength between the substrate and the coating has a value of 89 MPa. The microstructure of the coating was tested by the light microscopy technique. The structure of the coating consists of an NiCr alloy base with a dominant primary Cr3C2 carbide phase. In addition to the Cr3C2 phase, the Cr7C3 phase is also present. The coating etching was done with the reagent 1HNO3 : 4HCl : 4H2O that primarily dissolves nickel to enable the distribution of the carbide phase to be clearly seen in the coating. Etching the coating with this reagent revealed the presence of the largely undegraded primary Cr3C2 carbide phase which provides high hardness values to the coating.

87-107

Authors: Dalibor P. Petrović, Obrad T. Čabarkapa

This article - paper presents the design of the main rotor of the helicopter supported by the patent documents, as a very useful tool (instrument) to reach the specific ideas and design in order to find the most economical way for the quality solution for a certain technical problem present in the process of design (construction). A large amount of technical information first appears in patent documents and about two thirds of this information cannot be found on any other site. The structure of patent documents is presented with an emphasis on the elements that relate to technical information with the detailed explanation of the possibilities of the application of the patent documentation during the process of design of the main helicopter rotor. The procedure and methods of research of the related patent documents are presented on a specific example of helicopter rotor design. The Espacenet database of patent documents was used as the most comprehensive and the most frequently used database containing over eighty million different patent documents about inventions and technical improvement (advancement) from all over the world.The crucial part of the paper relates to the presentation of a patent search method in order to find a technical solution for the structures of the main helicopter rotor which relates to the provision of the required casting and rapid response changes of accommodation angle (step) of the rigid rotor blades of helicopters. Introduction Patent documents contain the largest database of various specifications, which, in order to preserve novelty of the innovation, first appear in patent documents three to five years earlier than in other technical reference publications. For this reason, patent documentation is an essential source of information for researchers - designers, primarily with the aim of finding structural solutions to the technical problem being solved, as well as for the monitoring and establishing new trends in the development of specific systems and equipment. Patent documentation and content of patent documents Patent documents contain technical, legal and bibliographic information to determine the patent. Technical information is of fundamental importance to designers for understanding the invention. If the technical information contained in the patent documents contains the solution of the specific problem to be solved, it is necessary to examine the legal basis for using this information, in order to avoid violation of intellectual property rights. Patent documents search By searching a patent documents database, an expert in a particular field of technology is allowed to: be up to date with the latest technical and technological solutions, find ready-made solutions to specific technical problems, get ideas for starting future development, establish patent activities of competitors in the market, get insight into the trends of development in a particular technical field, assess technology offered for licensing, have a more favorable positioning during negotiations on the transfer of technology as well as a variety of other information. The application of patent documents in designing the main helicopter rotor Search and analysis of patent documents is given as an example for rigid rotors, in which the bearings are replaced by elastic elements. In terms of design, these rotors are derived by connecting the blades and the head with elastic elements or by linking the blades with the elastic rotor head. During the design of the rotor head, advanced search for patent documents in the Espacenet basis is applied. Conclusion This article - paper emphasizes the significance of patent documents and the necessity of the search of patent documents databases, while designing the main rotor of a helicopter. The proper use of patent documents is a very useful tool for getting to specific ideas for solving specific technical problems during design. In this specific example, a technical problem related to a structural solution of the head of the rigid rotor of a helicopter, in order to provide the necessary casting and a rapid response of changes of the accommodation angle (step) of rigid rotor blades of helicopters. The basic intention of this paper is to illustrate and explain to researchers - designers that it is necessary to use patent documents in the process of design - construction.

131-145

Authors: Drage T. Petreski, Andrej P. Iliev, Aleksandra D. Petreska

The introduction of the European emergency number 112 in the Republic of Macedonia should provide benefits that will be implemented and regulated in accordance with the European legislative framework. This number has already provided numerous benefits to all member states of the European Union. Its implementation should be supported by the introduction of the latest technology information and communication solutions, hardware and software solutions tailored to the situation in the country. It will replace four current phone numbers for emergency calls that are a responsibility of the Ministry of Interior (192), local fire units (193), emergency care (194) and the Center for Crisis Management (195). These numbers are planned to be replaced by the European emergency number 112 together with its full implementation into the integrated information - communication center.

161-178

Authors: Predrag J. Pešić

Kaizen is a Japanese philosophy that focuses on continuous improvement, simplification and acceleration of processes, by reducing or eliminating waste and by spending a minimum of resources needed, while delivering the best possible quality products and services. It is a process that, when done correctly, humanizes the workplace, eliminates overly hard work and teaches people how to perform tests of their own work (using scientific methods) and eliminating scrap in the business process. Many military organizations have recognized the benefits of Kaizen and implemented it into their practice. Kaizen is one of the most acceptable methods of continuous process improvement in logistics. It is cost effective and flexible and allows incremental process improvement. At the same time, it provides logistics with quick, effective and efficient responses to any changes in its turbulent and complex environment. Introduction The introduction points out the importance of Kaizen as a world process aimed at eliminating all forms of waste and at efficient use of resources in manufacturing and service processes. It is both applicable in the economy and military organizations, in highly developed as well as developing countries. The aim of the article is to define an effective and efficient management approach to introducing the Kaizen process into logistics. Principles and basics of the Kaizen concept A brief overview of the basic principles and basics of the Kaizen management is given as well as tools and techniques for its implementation. Figure 1 shows the given Kaizen approach to process improvement. Since Kaizen insists on improved standardization procedures, the most important point is the difference between the methodology of Kaizen and ISO 9000.. Methodology of the implementation of Kaizen in logistics Since logistics is a large manufacturer, supplier and distributor of funds and a major consumer of financial resources, the article states the reasons for the need of implementation of Kaizen. Four types of Kaizen are possible to be implemented into logistics.. Table 1 gives the complexity of the distribution of Kaizen. Since there is no universal methodology for the implementation of Kaizen, Figure 2 gives a general map of the MEGA implementation process. The map shows the key processes (P) and input documents (UD) for the process implementation, resources (R) engaged in the implementation process and the output documents (ID) made (or updated) at the end of the process . Value stream and waste in logistics Value stream is a basic factor that must be considered when making a decision on the implementation of Kaizen. The ultimate goal of Kaizen is to eliminate any waste in a process or a work area; therefore, Table 2 lists seven basic types of waste in the logistic function of supply. The organization and implementation of Kaizen events The central part of the paper contains an analysis of implementing Kaizen principles and a methodology of the organization, implementation and monitoring of the implementation of Kaizen events. Specific guidelines for organizing and conducting Kaizen events are given. The scheduled time for a Kaizen event is shown in Figure 3. The main conclusion drawn is that there is no standardized, generic and universally applicable procedure, but only a framework for the implementation of the Kaizen program. The framework for the implementation involves several phases: from the identification of pre-conditions and priorities, through recording the current state and defining the future (target) one to its implementation in the strict sense, presentation and follow-up. Since waste elimination is in the focus of every Kaizen event, it is necessary to identify waste first. Table 2 lists the seven basic types of waste in the logistic function of supply. In any process there is specific waste, so it is necessary to develop a detailed checklist of waste, the form of which is shown in Table 3. It is particularly emphasized that Kaizen is a continuous cycle that keeps repeating. In this way, Kaizen improvements become a part of everyday life, which is the main objective of implementing Kaizen in logistics. Introducing Kaizen in local practice The paper points to the fact that the Kaizen philosophy may be appropriate particularly in the economic environment in Serbia and in the material support to the Army, because no large financial investments are necessary. There are two preconditions for its implementation: changing habits and mindsets of employees and their mass involvement and training. Therefore, the task of the organization management to encourage employees to continually learn and improve themselves is stressed in particular. Conclusion It can be concluded that a special benefit of the application of Kaizen in the Army is the fact that it is not linked with large financial investments and sophisticated technologies, that its principles do not have to be applied at once, but can be introduced step by step thus initiating a process of improvement that is continuous and never ending, because a current situation can always be improved. The fact is that the application of Kaizen will not be easy. It will require time and patience, as well as continuous education and training of all the involved. It is emphasized that changes are ineffective if they do not affect more (if not all) segments of an organization. Therefore, it is essential that the principles and methods of the Kaizen concept be extended to the whole environment of logistics. The general conclusion is that a strategic decision to implement Kaizen would help it to become a business life style and corporate culture in logistic and the entire military organization.

195-203

Authors: Slavko J. Pokorni

The article presents the basic information about the overal results, significance, international programme committee and working areas of the 6th International Scientific Conference on Defensive Technologies, OTEH 2014, in comparison with previous five conferences. The number of sections, number of papers, number of authors/coauthors, number of sessions and number of members of the scientific commitee are presented in the review. This year conference is the best regarding the number of papers and the number of authors/coauthors since this conference got its international character.

210-226

Authors: Dragan M. Vučković

Azerbaijan developing ZKDM combat vehicle Fire works: ARS seek greater range and accuracy Iran shows updated Falaq-1 and Falaq-2 rockets TOS-1A advances Russian firepower Iran reveals its Bavar-373 SAM New gun shapes up for Russian MBT

238-244

Authors: Miloš M. Jevtić

Weapons "FN P-90"The emergence and development of the concept of weapons for personal protection. A detailed description of the structural design of Belgian weapons "FN P-90", with emphasis on experiences from field use, and tactical - technical data.

9-31

Authors: Danijela D. Protić

In this paper, several linear and nonlinear techniques for speech processing based on AR, ARX, ARMAX, WLS and FNN models are proposed. The impact of the glottal wave to modelling is also shown in details. GD, BPA and LM approximations are used for model training and optimization. A comparative experimental analysis of five considered models is done based on the prediction of a speech signal. The results on training and testing are presented through learning and training errors for all models given.

56-66

Authors: Nadica S. Miljković, Goran S. Bijelić, Olivera C. Đorđević, Ljubica M. Konstantinović, Haritz R. Zabaleta, Tomislav B. Šekara

Low Back Pain (LBP) is one of the most common incidences all over the world. For the assessment of LBP, descriptive medical scores are widely used. Nevertheless, there is a need for the quantitative assessment of LBP by appropriate physiological and kinematic measurements. Quantitative assessment methods are of interest since they might provide reliable and repeatable measures related to low back pain in both everyday clinical practice and at home or work. In this paper, we proposed simple measurements of the trunk angle and the activity of back muscles during simple flexion/relaxation task for an improved assessment of LBP (Low Back Pain). The application of the proposed instrumentation and signal processing is evaluated in three healthy subjects and in two individuals with LBP.The presented data analysis indicates that angle velocity might be a promising parameter in a combination with electromyography profiles for differentiation between healthy subjects and in individuals with LBP for improved medical diagnostics and assessment.

84-101

Authors: Dejan M. Tepšić, Mladen Đ. Veinović

Mobile ad hoc networks (MANETs) are self-configuring networks of nodes connected via wireless without any form of centralized administration. This kind of networks is currently one of the most important research subjects due to a huge variety of applications (military, emergency, etc.). In MANETs, each node acts both as a host and as a router, thus it must be capable of forwarding packets to other nodes. Because of the node mobility, topologies of these networks change frequently. Traditional routing protocols used in wired networks cannot work efficiently in MANETs. Therefore, special routing protocols for MANETs are needed. The objective of this paper is to research the current state of the art of existing routing protocols for MANETs, and to compare different approaches. Routing protocols are classified according to the method of forwarding packets into unicast, multicast and broadcast. There are three main classes of unicast routing protocols for MANETs: proactive, reactive and hybrid. Introduction A mobile ad hoc network (MANET) is a dynamic network that allows wireless networking on the go, without the need for pre-built network infrastructure. It consists of mobile nodes, where a node can be a man carrying a handheld computer equipped with appropriate devices for wireless communications, a laptop computer, a robot, or anyone who is equipped with the appropriate equipment for wireless communication. MANET networks operate without centralized infrastructure, while the nodes mutually cooperate to ensure connectivity. MANET routing protocols When establishing communication over the wireless network, if two nodes are not directly connected through a communication link, messages must be forwarded through transit nodes. Finding the routes between two nodes that send messages within the communication network is called routing. Routing protocols designed for use in traditional fixed networks cannot be used in MANET networks. The specific characteristics of these networks require special routing protocols that deal with solving the specific challenges. Classification of the existing MANET routing protocols Unicast routing protocols designed for use in mobile ad hoc wireless networks can be classified according to the mechanism of updating information on routes into three categories: - proactive (periodic) routing protocols - each node maintains one or more tables in order to preserve the network topology and the information about the routes, - reactive (on-demand) routing protocols - routes are found only when needed, - hybrid routing protocols - combines features of proactive and reactive routing protocol. Multicast routing protocols Multicast routing protocols can be classified into four categories according to the route construction method: tree based, mesh based, hybrid, and stateless routing protocols. Broadcast routing protocols Broadcast routing protocols can be classified into the following categories: counter-based, area-based, neighbor-based, cluster-based and probabilistic-based methods. The choice of unicast routing protocol in MANETs When it comes to choosing a unicast routing protocol within the MANET network, the reactive approach achieves better results when node mobility is high and when the amount of traffic transmitted between the nodes is small. On the other hand, proactive routing protocols are recommended when the network is generally static, and when the amount of generated traffic between nodes is high. When a balance between the different models of the mobility of nodes and different amounts of generated traffic between nodes within a network is needed, it is recommended to use a hybrid routing protocol which combines both classes of protocols, a proactive one and a reactive one. Conclusion The topology of mobile ad hoc networks can be dynamic and unpredictable. Traditional routing protocols used in cable networks cannot be directly applied to mobile ad hoc wireless networks. Three major classes of unicast routing protocols are proactive, reactive and hybrid.

114-136

Authors: Slaviša I. Vlačić, Aleksandar Z. Knežević, Nikola Đ. Pekić

Multirole combat aircraft represent a dominant category of combat planes. They can perform many different assigned taskssuch as those of- primary fighters, bombers and reconnaissance aircraft. In the execution of some tasks, it is evident that the crew of multirole combat aircraft is overloaded.This fact imposes the use of the two-seat cockpit configuration instead of the most common single seat cockpit configuration. Both configurations have their advantages and disadvantages, which requires a careful consideration of some tehnical and tactical aspects in the cockpit configuration of the multirole combat aircraft fleet. Some of the most important apects are considered in this paper. Introduction Multirole combat aircraft belong to a tactical combat aircraft category intended for the execution of many different tasks such as those of bombers, fighters, attack andreconnaissance aircraft. They were developed from fighter aircraft and emerged as a result of a fast technological advance at the domain of electronic equipment and weapon systems. Widening the combat capabilities of multirole aircraft in comparison to fighter aircraft from which they emerged imposes the reassessment of the attitudes towards the cockpit configuration, i.e. towards the decision which configuration to implement – one or two seat variant. Historical approach to cockpit configuration From the historical point of view, fighter planes, predecessors of multirole combat aircraft, developed in two directions: day fighters and fighters designated for accomplishing tasks in Instrumental Meteorological Conditions and by night. Fighter planes from the first category were mostly single seaters and the second ones were two seaters. In a two seater, the rear cockpit was usually occupied by qualified radar/weapon officers and rarely by qualified pilots. The complexity of fighter planes imposed a need for designing two seaters for pilot training. The ratio between two and single seaters in the 2nd and 3rd generation of combat planes was similar for the western and eastern models. The share of two seaters was between 13 and 18 percent. The fast development of electronic equipment and precisely guided ammunition has led to a significant evolution of existing fighters. Through the programs of comprehensive modernization they have become true multirole combat aircraft. This category was accepted by small airforces as well as by large ones. Correlation between technical-technological advance and crew overloading A wide spectrum of tasks performed by multirole combat aircraft was achieved by advance in the domain of navigational, radar and sensor systems as well as in information and communication technologies. All the mentioned systems and subsystems enabled a higher level of situation awareness of the pilot and his better task completion, but his overloading significantly increased. Therefore, decreasing crew task overloading has become a significant aspect in formulating requests for the cockpit layout. Solving the problem of crew overloading during the past two decades has taken two directions. The first was keeping the single seat cockpit configuration and the second one was the customization of two seat trainers for multirole combat tasks. In order to explain these two directions, the following 4th generation airplanes in different variants were considered: Eurofighter, F-15, F-16, F/A-18, JAS-39 Gripen, MiG-29, Su-27/30 and Rafale. The first direction includes airplanes such as Eurofighter and JAS-39 Gripen whilst the second, to a greater or lesser extent, includes F-15, F-16, F/A-18, MiG-29, Su-27/30 and Rafale. Technical factors of configuring multirole combat aircraft cockpit configuration Single seaters were preferred by the countries that in their initial tactical requirements required solely the fighter airplane. With changing circumstances, these countries redesigned their projects and upgraded them to multirole platforms. A smaller number of two seaters were justified by their higher acquisition price (10% higher) and by higher direct operational costs during the life cycle. Pilot overloading was reduced by the application of highly automatized systems, digital flight control systems and carefree handling, GPWS, and helmet-mounted cueing systems. A typical example is Eurofighter. Preferences for the two-seat cockpit layout over single seaters is evident in the case of Rafale and also in the case of F-15, F-16, F/A-18 and Su-27/30 - especially in the case of planes built after 2000. From the very beginning, Rafale was developed as a multirole platform. The other considered airplanes were developed as single seaters. However, after some combat and exploitation experience, the two-seat cockpit configuration is preferred nowadays. The share of two seaters in the total number of multirole combat airplanes is experiencing growth. In certain cases, as in the example of MiG-29M/M2, single seat layouts are produced out of two-seat cockpit airplanes. Multirole characteristics and the growth of combat capabilities of the two-seat configuration resulted in supplying the rear cockpit with equipment and devices alongside with enlarged authorization on decision process and actions against airborne and ground targets. Enhanced coordination between crew members due to the application of these technological solutions is also noticeable. Technical factors of configuring multirole combat aircraft cockpit configuration Two-seat models of multirole combat airplanes have higher MDZFW (Maximum Design Zero Fuel Weight) and less internal fuel weight. The consequence is a smaller tactical range. In order to extend the tactical range of two seaters, Conformal Fuel Tanks (CFT) are applied. As an effect, the CFT increase aerodynamic drag, reduce G overload and reduce maximum speed as well as aircraft acceleration. This category of fuel tanks is impossible to jettison, and that is why this configuration is used as a forced solution. A typical example is F-16 and its latest block versions dedicated to fighter-bomber tasks. No matter what the tasks of the multirole combat aircraft are, if there is a second crew member in the rear cockpit, his training is necessary. In certain airforces the pilot in the rear cockpit is preferred, whilst others have weapon systems officers. The concept of two-crew member functioning was devised through the independent and autonomous use of sensors data and individual detecting and acting upon targets from both cockpits. The operator in the rear cockpit wears a helmet-mounted cueing system which additionally increases the efficiency of the aircraft as a platform. Conclusion Rapid development of electronic equipment and precisely guided ammunition has allowed the evolution of fighters into multirole combat airplanes. Technical and technological advance was perceived through the installation of multifunctional radars capable of working in numerous modes, optical sensors, equipment for self-protection and electronic countermeasures as well as data-link devices. These technical subsystems have provided to the pilot a means for a higher level of situational awareness and more high quality, effective and safer task completion. With no doubt, this process increased pilot task burden and raised a question of configuring combat aircraft cockpits as single seaters or two seaters. It is also obvious that single seat planes are cheaper in exploatation than two seaters. In order to reduce crew overloading and increase combat plane efficiency, a high level of automatization was applied, based on digital flight controls careless airplane handling, a GPWS (ground proximity warning system) and a helmet-mounted cueing system. The fusion of sensor data was also enabled. The exploitation experience and lessons learned from local conflicts had a significant impact upon the increase of the number of two-seat multirole combat airplanes. It is evident that the two-seat cockpit configuration prevails in today’s production of multirole combat aircraft, or at least has a higher share in the serial production than it was the case in the first production lots. Configuring a fleet of multirole combat aircraft with two seaters is more evident in the case of smaller airforces that are in need of a true multirole platform because of the unification of their aircraft fleets. Though it stands that a smaller tactical range and a possibility of loss of two crew members are two-seater disadvantages, the number of acquired two seaters is still far from desired, especially in cases when there is a need for fighter-bomber and interdiction strike tasks. On the basis of available statistics, it can be concluded that the number of two-seated cockpit airplanes have experienced growth in the past two decades and that they are preferred by airforces with extensive combat experience as well as by airforce experts out of the circles of aircraft manufacturers and armament dealers.

144-168

Authors: Nenad V. Kovačević, Goran M. Lazić

The article presents a brief overview of modern developments and directions of further development of amphibious assets for overcoming water obstacles in foreign armed forces, notably the amphibian assets of the armed forces of the Parties of the North Atlantic Treaty Organization (NATO), the Russian Federation and the People's Republic of China. The article follows the historical path of the development of amphibious assets.The paper deals with the classification of amphibious assets in foreign armed forces.In preparing the article, there was a big problem to find the latest literature so data from the Internet was largely used. The literature that exists in the Army of Serbia is related to the seventies of the last century, when there was the last investment in amphibious assets.The knowledge on the amphibious assets for overcoming water obstacles in foreign armed forces can be seen as a help in assessing the effects of their use and the need for innovation and investment in the country’s own resources. Introduction The introduction explains the very concept of water hazard and its characteristics.It also explains the importance of water obstacles in the development of military equipment, but also in terms of the execution of tactical operations and procedures. Historical development of amphibious assets This section shows the historical development of amphibious assets from the early nineteenth century through World War II and Cold War until today.The historical development of amphibious assets is shown through figures 1 to 3. The classification of amphibious assets in foreign armed forces is given as well. Amphibious assets of the armed forces of the NATO countries The amphibious assets of the armed forces of the NATO countries shown here are representative for the armed forces of the NATO countries. The assets of the armed forces of the United States, the United Kingdom, France, Turkey and Germany are given in figures 4 to 11 and explained with their tactical - technical data. Amphibious vehicles of the armed forces of the Russian Federation The amphibious vehicles of the armed forces of the Russian Federation displayed here are representative for the armed forces of the Russian Federation. The displayed assets are just modified versions of the eighties assets, primarily due to the minimal investment of the Russian armed forces into the sector of weapons and equipment. The assets are given in figures from 12 to 18 and explained with their tactical - technical data. Amphibious assets of the armed forces of the People's Republic of China The amphibious assets of the armed forces of the People's Republic of China shown here are representative for the armed forces of the People's Republic of China. Only the original assets of Chinese production are shown since all other assets come from the Russian armed forces. They are shown in Figures 19 and 20 and followed with their tactical - technical data. Conclusion The conclusion discusses the tendency of further development of amphibious assets in foreign armed forces.

190-208

Authors: Mladen R. Tišma

Contract to equip Eurofighter with AESA radar Kaptor E signed; Carrier-based version of PAK-FA multirole fighter in plan; Flying car from Slovakia; F-35C first carrier landing; Chinese J-31 fighter aircraft officially presented to the public; Embraer unveiled a prototype of KC-390 transport aircraft; Russia develops new AWACS under the designation A-100; The first modernized bomber Tu-160 flies; Iran conducted a successful test flight of unmanned aircraft reverse-engineered from American RQ-170; China and Russia jointly to develop the largest and most powerful helicopter in the world; Lithuanians develops new VHF early warning radar; Ukraine considers the licensed production of L-15 aircraft; The new missile to equip the aircraft PAK-FA entered serial production in 2015; USN to convert TV-guided Mavericks to laser guided missiles; Lockheed Martin to equip F-22 fighters with AIM-9X missiles; China launched new military satellites; Ukraine is developing new missiles and trackers; Russia is developing a new generation of satellites for early warning.

225-238

Authors: Nikola M. Ostojić

The text is about armaments and military equipment displayed during the parade “March of the Victorious” in Belgrade, 2014. It reflects on most important components of armaments and equipment in the context of bringing the Armed Forces of Serbia up to date, and on the overall impression of the parade as a representative and referent frame of capacities of the Armed Forces for conflicts with possible enemies in all dimensions of war.

243-247

Authors: Nebojša N. Gaćeša

Russian-Serbian joint antiterrorist exercise

263-264

Authors: Nebojša N. Gaćeša

Informations for contributors and readers

282-287

Authors: Nebojša N. Gaćeša

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