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Abstract

Aircraft, their assemblies, and units must provide high durability and reliability, and maintain mechanical and technological characteristics throughout the life span of the aircraft. Different elements of aircraft structures work under mechanical loads, over a wide temperature range, with varying degrees of exposure to corrosive environments. Aircraft structural materials have a variation in the characteristics values and require the various testing methods for their inspection.

In many NDT methods applied in aviation materials testing, signals that could be represented by a narrowband processes model are used. Known methods of their processing are focused on determining and analyzing the signals amplitude characteristics, but the information resource contained in phase characteristics is not used.

In the article, the methodology for signal processing and determining phase characteristics in the time domain are discussed. It is based on the combination of the discrete Hilbert transform and the deterministic and statistical methods of the phase measurement. There are given examples of the application of the methodology for pulsed eddy current testing of electrically conductive materials and products, ultrasonic thickness measurement of products made of materials have significant ultrasonic attenuation, the realization impulse variant of acoustic impedance flaw detection of products made of composite materials. The examples have shown that the proposed signal processing methodology enables to determine new information parameters and signal characteristics for the industry, and extend the scope of known NDT methods.

Abstract

In paper the issue of a rocket flight impact and overall survivability of such flight by Apis mellifera (western honeybees) specimens is raised. Author claims that it is the key for using them on Mars for pollination in future, as this species is considered as one of the best pollinators, and should be examined before sending first human missions to the Red Planet. Rocket payload ‘BeeO!Logical’ was designed in order to conduct the research, the first of its kind worldwide. Its assumptions are presented along with overall descriptions of the experiments in two sounding rockets. Analysed data included survivability, carbon dioxide concentration values (respiration levels), temperature and humidity. It has been shown that A. mellifera specimens are able to survive the rocket flight. Project development possibilities are described, including widening the scope of the research with bumblebees (Bombus) and implementation of biocybernetic model of bee colony.

Abstract

Efficiency is a crucial parameter for an airplane to reduce both cost of operations and emission of pollutants. There are several airplane concepts that potentially allow for increasing the efficiency. A few of them were not investigated thoroughly enough yet. The inverted joined wing configuration, with the upper wing in front of the lower one is an example of such concept. Therefore, a project consisting of development of an experimental scaled demonstrator, and its wind tunnel and flight testing, was undertaken by consortium: Institute of Aviation, Warsaw University of Technology, Air Force Institute of Technology and a MSP company. Results led to a conclusion, that the inverted joined wing configuration allows to build an airplane with excellent performance, but its advantage against the conventional airplane is marginal because of large trimming drag of the configuration with relatively high position of the thrust vector in pusher configuration. It was applied because the demonstrator was a flying model of manned airplane and the tractor configuration would affect the pilot’s field of observation. However, in case of the UAV, this reason becomes insignificant. Therefore two configurations of tractor propulsion were tested to see, if their performance is better than the performance of original design.

Abstract

Eddy current (EC) method is considered as most applicable for in-service detection of fatigue subsurface cracks initiated in aircraft multilayer structures near the rivet holes. At the same time, the successful solution of this problem is obstructed by additional noise created by defect-free rivets. All EC inspection techniques for the detection of subsurface cracks around the rivets can be classified into three main groups: 1) static mode – carried out by placing the EC probe concentrically on the rivet head; 2) rotational mode – when the EC probe is rotated around the rivet axle and 2) sliding mode – performed by the movement of EC probe along the rivet line or near it. All these approaches have some advantages and limitations. In this study, known EC techniques for the detection of cracks in multilayer aircraft structures are analyzed. New advanced EC techniques for the detection of fatigue cracks in internal layers of the riveted structures based on different types (ring, sliding, and rotational) probes are presented. The static EC method with developed low-height ring-type probe creates the possibility to detect cracks in the difficult of access areas. The possibility to estimate the length of detected cracks by a ring-type probe is shown. The proposed rotational remote field EC probe can detect as small as 1.0 mm long cracks under the button-head rivet and 2 mm thick upper skin with a high signal-to-noise ratio. Therefore, in many aircraft structures, fatigue cracks will be detected before a critical threshold achieved. New EC sliding techniques based on remote field and double differential probes were proposed for the rapid detection of cracks in internal layers of riveted aircraft structures. Remote-field EC probe for reliable detection of fatigue cracks in third and fourth layers of five-layer units was proposed. Another sliding technique based on a double differential EC probe gives the possibility to detect transverse cracks in the second layer without the rivet row area access. The main advantage of developed techniques is high inspection reliability due to the possibility to discriminate the signals created by cracks and defect-free rivets. Presented inspection procedures include the selective signal analysis in the complex plane diagram. Proposed EC inspection techniques were successfully implemented into the aircraft maintenance practice.

Abstract

This article summarizes avionics safety-critical software development methodologies and implications of the DO-178C standard from an Agile application perspective. We explain the safety-critical software categorization. It also outlines the main differences and advantages of different approaches to the development process, from Waterfall through the V-model to Iterative and Incremental. Agile principles are explained as well as a Scrum – which is a popular framework in the non-safety-critical software industry. The application of Agile, for safety-critical software considerations, is based on the practical knowledge of the authors, and looks at the potential solution from a DO-178C standard, size of the project, scalability, and organizational culture points of view. Definition of the Agile type of framework, consistent with the certification process and existing standards, has been highlighted as a potential game-changer for the avionics industry.

Abstract

The goal of this paper is to investigate the influence of the objectively existing effectiveness functions of an aircraft control system upon the control and managerial decision making process in the framework of the subjective entropy maximum princi-ple. The subjective analysis theory entropy paradigm makes it possible to consider the aircraft control system based upon personal preferences as an active system governed by an individual (active element of the control system) with the help of her/his individual subjective preferences optimal distributions obtained in conditions of operational multi-alternativeness and those operational alternatives the active system active element’s individual subjective preferences uncertainty. The described ap-proach takes into account the simple two-alternative operational situation in regards with the objectively existing effectiveness functions, related to the aircraft control system, in the view of a controlled parameter and a combination of it with its rate as the ratio. The obtained expressions for the objective functional extremal functions of the effectiveness and preferences, as well as the subjective entropy of the alternatives preferences, illustrated in diagrams visualize the situation and allow taking a good choice. The ideas of the required proper governing, managing, and control methods choice optimization with respect to only 2 alternative objective effectiveness functions arguments might be simple; nevertheless, increasing the number of parameters and further complication of the problem setting will not change the principle of the problem solution.

Abstract

The paper presents research on the near real-time atmospheric sounding system. The main objective of the research was the development and testing of the weather sounding system based on a weather balloon. The system contains a redundant system of radiosondes, a lifting platform containing weather balloon and a holding system as well as ground station. Several tests of the system were performed in August and September 2019. Altitude, reliability, resistance to weather conditions and data convergence were tested. During tests, new procedures for such missions were developed. The final test was performed for the ILR-33 Amber Rocket as a part of pre-launch procedures. The test was successful and allowed to use acquired atmospheric data for further processing. Several post-tests conclusions were drawn. The altitude of sounding by a weather balloon depends mostly on weather conditions, the amount of gas pumped and the weight of a payload. The launching place and experience of the crew play an important role in the final success of the mission, as well.

Abstract

The presented paper considers a comparison of the traditional methods for the state maximal probability determination to the proposed hybrid probabilistic and variational concept. It is shown the advantages of the described multi-optional hybrid-effectiveness functions uncertainty measure conditional optimization doctrine in the sense of avoiding the traditional ways analytical complicatedness concerning the maximal probability of the possible state determination. The results of the numerical example are presented.

Abstract

The article is in line with the contemporary interests of companies from the aviation industry. It describes thermoplastic material and inspection techniques used in leading aviation companies. The subject matter of non-destructive testing currently used in aircraft inspections of composite structures is approximated and each of the methods used is briefly described. The characteristics of carbon preimpregnates in thermoplastic matrix are also presented, as well as types of thermoplastic materials and examples of their application in surface ship construction. The advantages, disadvantages and limitations for these materials are listed. The focus was put on the explanation of the ultrasonic method, which is the most commonly used method during the inspection of composite structures at the production and exploitation stage. Describing the ultrasonic method, the focus was put on echo pulse technique and the use of modern Phased Array heads. Incompatibilities most frequently occurring and detected in composite materials with thermosetting and thermoplastic matrix were listed and described. A thermoplastic flat composite panel made of carbon pre-impregnate in a high-temperature matrix (over 300°C), which was the subject of the study, was described. The results of non-destructive testing (ultrasonic method) of thermoplastic panel were presented and conclusions were drawn.

Abstract

Noise generated by helicopters is one of the main problems associated with the operation of rotorcrafts. Requirements for reduction of helicopter noise were reflected in the regulations introducing lower limits of acceptable rotorcraft noise. A significant source of noise generated by helicopters are the main rotor and tail rotor blades. Radical noise reduction can be obtained by slowing down the blade tips speed of main and tail rotors. Reducing the rotational speed of the blades may decrease rotor thrust and diminish helicopter performance. The problem can be solved by attaching more blades to main rotor. The paper presents results of calculation regarding improvement of the helicopter performance which can be achieved for reduced rotor speed but with increased number of rotor blades. The calculations were performed for data of hypothetical light helicopter. Results of simulation include rotor loads and blade deformations in chosen flight conditions. Equations of motion of flexible rotor blades were solved using the Galerkin method which takes into account selected eigen modes of the blades. The simulation analyzes can help to determine the performance and loads of a quiet helicopter with reduced rotor speed within the operational envelope of helicopter flight states.