The article presents a methodology for the implementation of preliminary and state tests on the example of the project entitled “Jet air targets with a programmable flight route” conducted by the Air ...Force Institute of Technology. The experience in the field of maneuvering aerial targets has allowed for implementation of an aerial jet target set. The further stages of research necessary to implement the set for operation have been presented. Investigations of the aerial jet targets were carried out based on the regulations in force in the Polish Armed Forces.
The motivation behind solving the issue of estimating the flow parameters of the pneumatic system of a launcher was the need to obtain the take-off energy with a value exceeding 80 kJ. The take-off ...energy and the initial speed of the unmanned aerial vehicle (UAV) depends on the pressure drop time in the launcher’s pneumatic system. The aim of the research was to estimate the flow parameters of the trigger system of the UAV launchers in order to achieve the shortest time of its operation. Due to the lack of a description of the selection of pneumatic elements and their flow characteristics in the available literature, the article attempts to analytically describe the air flow through pneumatic units. The trigger system is described using the sonic conductivity and the critical pressure ratio. Due to the lack of numerical data on the flow parameters of pneumatic units, a test stand was designed and constructed to determine these parameters. The values of the sound conductivity and the critical pressure ratio were determined for each of the pneumatic units and for the entire system. The proposed method makes it possible to determine the relationship between the operating time and the values of the flow parameters of the pneumatic launch tube release system. It also provides guidelines for design and technological solutions for the trigger system of any pneumatic launcher.
The correct operation of the hydraulic pump and achieving the assumed durability depends on the purity of the used working fluid. The research paper discusses a method for evaluating the ...contamination sensitivity of a hydraulic plunger pump. The theoretical grounds for evaluating the contamination sensitivity of hydraulic plunger pumps of a hydraulic drive based on the contamination sensitivity factor were presented. An example of evaluating contamination sensitivity of an NP-34M hydraulic plunger pump was discussed.
The subject of this publication is a mathematical model of a pneumatic supply system for an emergency parachute system. This system is intended for a vertical take-off and landing UAV. An overview of ...emergency parachute landing system designs is presented in the introduction. Based on a schematic diagram and a 3D computer model, the construction and operation principles of an emergency parachute system, currently being developed at AFIT, was presented. A mathematical model, which enables the determination of the energy of gas (compressed CO
) stored in the accumulator tank was described. The conducted tests, which involved weighing the accumulator after filling with liquefied CO
from a special cartridge and equivalent mass ejections were discussed. These tests involved recording the track of the equivalent mass movement and time necessary to determine velocity. The results of calculations regarding the equivalent mass energy imitating an emergency parachute, CO
volume and mass in the accumulator in liquefied and gaseous state were presented. Based on the conducted calculations and the obtained characteristics, the developed mathematical model was assessed, and the final conclusions formulated.
Defects in an aircraft can be caused by design flaw, manufacturer flaw or wear and tear from use. Although inspections are performed on the airplane before and after flights, accidents still result ...from faulty equipment and malfunctioning components. Determining the causes of an aircraft accident is an outcome of a very laborious and often very long investigation process. According to the statistics, currently the human factor has the biggest share within the causal groups. Along with the development of aviation technology came a decline in the number of accidents caused by failures or malfunctions, though such still happen, especially considering aging aircraft. Discovering causes and factors behind an aircraft accident is of crucial significance from the perspective of improving aircraft operational safety. Effective prevention is the basic measure of raising the aircraft reliability level, and the safety-related guidelines must be developed based on verified facts, reliable analysis and logical conclusions. This article presents simulation tests carried out by finite element method and constitutive laboratory tests leading to the explanation of the direct cause of a military aircraft accident. Computer-based simulation methods are particularly useful when it comes to analysing the kinematics of mechanisms and potential stress concentration points. Using computer models enables analysing an individual element failure process, identifying their sequence and locating their primary failure source.
Throughout previous practice, estimating the life of aviation hydraulic drive assemblies has been utilizing a variant, which requires
conducting long-lasting studies of the drive assemblies until ...they move to the unfitness state. Such studies, which enable estimating life a posteriori, are costly and long-lasting. Hence the need to look for new strategies for estimating life. The article presents
a method of estimating the durability of a hydraulic drive assembly based on the control of its change in technical condition. Inspection of the technical condition enables timely detection of the condition before the emergency hydraulic assembly. The novelty of the
method is to use, to detect the condition before the emergency team, the principle of determining the pre-emptive control parameter
tolerance. Pre-emptive tolerances are a set of control parameter values between threshold levels and pre-emergency (allowable)
levels. The intensity of depletion of durability (intensity of aging, wear) is random. The paper presents a stochastic description of
the control parameter change and the resulting empirical relationships between the control parameter verification time probability
density (verification periodicity) and the control parameter value change probability density. The inter-relations between these two
functions were described. It also presents empirical relationships enabling the determination of the permissible value for the control
parameters and the periodicity of the control parameter checks after exceeding the limit value. An example of estimating the life of
a hydraulic piston pump on-board an aircraft operated in the Polish Air Forces was shown. The permissible values and the time
for the first control parameter verification after exceeding the limit value were determined for selected control parameters of the
hydraulic pump. The proposed method binds life (fitness time) with the physical wear mechanisms concerning the assemblies. It
can be applied in work aimed at determining the resource life of technical equipment. Furthermore, it enables utilizing technical
equipment according to a technical state strategy with monitoring the parameters.
Malfunctions of Aviation Hydraulic Pumps Ułanowicz, Leszek; Jastrzębski, Grzegorz; Szczepaniak, Paweł ...
Journal of KONBiN,
10/2020, Letnik:
50, Številka:
3
Journal Article
Recenzirano
Odprti dostop
Hydraulic pumps are among the most complex and responsible units from the point of view of aircraft flight safety. One of the most important scientific and technical problems in improving the ...reliability of hydraulic pumps is to understand the physical nature of the cause of damage in them and on this basis to develop measures and recommendations to ensure their reliability. The article discusses the characteristics of hydraulic piston pairs of hydraulic pumps according to the kinematics of their movement and load conditions. Selected actual damages of axial piston pumps are discussed. The paper presents a simplified 3D solid model of the cylinder-piston assembly and the mechanism for adjusting the inclination of the piston cylinder block, the axial hydraulic pump, and the model of breaking loads for selected elements of this pump. The digital solid model and element load analysis were developed in SolidWorks Simulation.
The occurrence of an external leak in the aviation fuel unit leads to a catastrophic aviation event. The aim of the research was to estimate the flow of the fuel stream through the fuel filter ...chamber with its external unsealing. The research was carried out using experimental methods and computer CFD modelling. Experimental studies were carried out on a specially designed test stand. During the tests, the flow rate of the fuel stream flowing out to the environment was changed. Numerical calculations allowed to obtain the values of the stream and pressure inside the leaky filter chamber. The results of numerical calculations were compared with the results of experimental measurements. The CFD method significantly supplemented the information on the fuel flow inside the considered filter chamber at its external unsealing. The use of software based on the CFD method allows to obtain reliable values characterizing the fuel flow in the aviation fuel unit.
The article presents the tests that were conducted to examine the possibility of the fuel filter shank’s thread shearing under the impact of hydrostatic pressure. Increased wear due to friction was ...confirmed on the threads of the titanium shanks that were tested, together with significantly reduced wear of the mating threads and steel sleeves. Shearing tests confirmed that to shear a thread that is worn to a degree similar to the threads that were tested, it is necessary to apply eight times more static pressure than the maximum pressure in the filter. A comparison of the shape of the coils of the thread that was subjected to the pressure test with the thread from the damaged filter demonstrated a significant difference in the wearing of these elements due to friction.
One of the approaches to ensure friction stability in hydraulic precise pairs can be coating their components with low-friction materials with the friction coating method using a metal, e.g. brass. ...The article presents the method of applying brass on the steel surface of a hydraulic pair using friction. It discusses the technology of brass plating of hydraulic precise pairs and the results of laboratory tests involving friction-brasses hydraulic precise pairs. The factors impacting the quality of brass-coating process of hydraulic precise pairs and the requirements set for hydraulic precise pairs subject to friction-brassing were also discussed.
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