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Monitoring of helicopter swash-plate wear using the FAM-C diagnosis method

Gębura Andrzej, Kowalczyk Henryk, Tokarski Tomasz, Handzel Kacper, Klimaszewski Sławomir Jerzy, Zgrzywa Franciszek

Diagnostyka

2022

Vol. 23, No. 1

art. no. 2022104

Helicopter rotor dynamics (blade vibrations, ground resonance, influence of forward speed, etc.) play an important role in the wear and tear of the transmission system and power unit. Particularly fast wear of these components is to be expected in military helicopters in combat conditions, where the flight dynamics parameters are often exceeded. The FAM-C method developed at the Air Force Institute of Technology in Poland has been used to assess and monitor this wear. This method can be used to monitor damage to helicopter propulsion and transmission, where other "classical" methods are less effective due to a very complicated system of forces, variable as to the direction of amplitude and frequency, causing vibrations in closely spaced kinematic pairs. For this reason, vibroacoustic and thermal effects are created around these kinematic pairs, which interfere with each other. In a helicopter, the propulsion unit, including the power transmission unit, is at the same time the carrier unit. This has forced designers to construct a propulsion system with a much greater number of joints and bearing supports. This article presents the possibilities of the FAM-C method for monitoring of swash-plate main bearing wear. The swash-plates are not formally part of the helicopter's propulsion unit but are used to direct the thrust vector of the blades i.e., they direct the helicopter's power vector. Since during this process their components are observable by the FAM-C method, the authors found it necessary to include issues related to their diagnosis in this study. In the FAM-C method, the signal from the AC generator during the normal operation of the helicopter is processed. Analysis of this signal allows simultaneous monitoring of multiple engine and transmission components simultaneously. It does not require any separate sensors for this purpose - one "full-time" alternator or tachometer generator is - with proper collection and processing of the output voltage signal - the source of a whole range of diagnostic information. Thus, one generator is an observer of the technical condition of many elements of the power unit simultaneously. What's more, the signal can be collected from any place in the electrical network, which makes it possible to install the measuring system in safe locations, even while the power train is running. Some examples of diagnostic symptoms leading to wear detection are described. Research based on analysis of these findings with the use of the FAM-C method is described in the paper. In the FAM-C method, signal from the AC generator used in routine operation of the helicopter is processed. Signal analysis enables simultaneous monitoring of several engine and transmission elements. Some examples of diagnostic symptoms used to detect wear are described in the paper.

Problemy korozyjne struktury połączenia metalizacyjnego poszycia statku powietrznego - wybrane problemy

Ciężak Patryk, Gębura Andrzej, Szawłowski Sergiusz, Kwiatkowski Tadeusz, Handzel Kacper, Paszek Sławomir, Marcinkowska Maria, Kowalczyk Henryk, Olkowicz Klaudia

Journal of KONBiN

2021

Vol. 51, iss. 4

91--105

Artykuł ujmuje kompleksowo problemy korozyjne związane ze strukturą obwodów powrotnych wojskowych statków powietrznych o metalowej konstrukcji kadłuba. Autorzy opisują problemy związane z wykorzystaniem kadłuba jako obwodu powrotnego prądu elektrycznego, w szczególności z przewodami minusowymi łączącymi kadłub z zaciskami minusowymi odbiornika lub źródła, rzadko poruszane w literaturze naukowej z uwagi na "trywialność" zagadnienia. Aby zmniejszyć błąd pomiarowy, autorzy do pomiarów rezystancji poszycia kadłuba wykorzystują metodę techniczną o natężeniu prądu probierczego zwiększanego proporcjonalnie do pola powierzchni i stopnia sfałdowania powierzchni stykowej.

The article comprehensively describes corrosion problems related to the structure of ground-return circuits of military aircraft with metal fuselage structure. The authors describe problems related to the usage of the fuselage as a ground-return circuit of electric current, especially with negative circuits connecting the fuselage with negative terminals of the receiver or the source, rarely discussed in the scientific literature due to the triviality of the problem. Given the necessity to reduce the measurement error, the authors use a technical method for measuring the resistance of the fuselage fabric covering with the intensity of test current increased in proportion to the surface area and the degree of folding the contact surface.