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Open access

Marcin Kurdelski and Andrzej Leski

Crack Growth Analysis of the Landing Gear Pull Rod of the Fighter Jet Aircraft

This paper describes the problem of searching for the causes of damage in the form of rupture of a strength member of the main landing gear. There have been two incidents noted which both occurred during hangar storage. It should be pointed out that the two occurrences mentioned concern a particular aircraft currently in operation, and that these incidents occurred a few days after the last flight.

This article presents part of the investigation process needed to determine the causes of cracks in the test item. The crack growth analysis of the pull rod was performed using the NASGRO software. In order to perform the calculations, the information was gathered during previously conducted material studies and flight tests.

Open access

Marcin Kurdelski and Andrzej Gębura


The paper deals with selected issues related to operation of steering disks designed for helicopters that are currently in operation of the Air Force of the Republic of Poland. The attempt is made to present a prediction of hazards to the transmission gear of that helicopter where the forecast is based on a theoretical analysis of mechanical phenomena as well as the statistical and diagnostic analyses. The major attention is paid to the opportunity to diagnose hazardous locations of the helicopter steering disk with use of a non-destructive FAM-C method originally developed by ITWL. The method is based on tracking of frequency modulation parameters generated by the on-board AC generator. The examination does not require the installation of any additional sensor since the transmission is subjected to neither additional load nor distortions of the rotation speed occur.

The authors of this study disclosed the initial results from diagnostic measurements as well as snapshots taken during the disassembling of steering disks from Mi-24 and Mi-17 helicopters that were operated under heavy duty conditions of military missions in Iraq and Afghanistan. They also suggested an easy and cheap method for field checking of the steering disk bearing by photogrammetric measurements. It is also demonstrated that the method of diagnostic investigations can be also spread onto other helicopter makes and types.

Open access

Marcin Kurdelski and Andrzej Gębura


W publikacji przedstawiono wybrane problemy eksploatacyjne tarcz sterujących śmigłowców eksploatowanych w lotnictwie Sił Zbrojnych RP. Przedstawiono również prognozy zagrożeń dla zespołu transmisji tego śmigłowca, opartej na analizie teoretycznej zjawisk mechanicznych, jak również analizie statystycznej i diagnostycznej. Główną uwagę zwrócono na możliwości diagnozowania miejsc zagrożeń w tarczy sterującej śmigłowca nieinwazyjną metodą FAM-C, opracowaną w ITWL. Metoda ta jest oparta na śledzeniu parametrów modulacji częstotliwości generowanych przez prądnicę pokładową prądu przemiennego. Badanie to nie wymaga instalowania żadnych dodatkowych czujników, gdyż podczas pomiaru zespół transmisji nie doznaje żadnych dodatkowych obciążeń ani zniekształceń prędkości obrotowej.

Autorzy w publikacji zaprezentowali wstępne wyniki pomiarów diagnostycznych oraz materiały z demontażu tarcz sterujących śmigłowców eksploatowanych w warunkach misji wojskowych w Iraku i Afganistanie, wykonanego na śmigłowcach Mi-24 oraz Mi-17. Zaproponowano także, zdaniem autorów, prostą i tanią metodę polowego sprawdzania łożyska głównego tarczy sterującej metodą pomiaru fotogrametrycznego. Autorzy wykazali, że metodologię badań diagnostycznych można i trzeba rozciągnąć na inne typy śmigłowców

Open access

Marcin Kurdelski and Łukasz Obrycki

The Cracks Propagation Calculations in the PZL-130 Orlik Structure

The article presents the results of research carried out under a research project on the evaluation of fatigue life. The subject of the analysis was the critical elements of the PZL-130 Orlik. The numerical crack growth analyses were performed using the NASGRO equation. The Orlik aircraft are mainly used for the basic pilot training in the Polish Air Force. Each airplane is equipped with a digital flight data recorder. The record of more than 36000 flight hours is the basis for numerical analysis of fatigue life.

Open access

Andrzej Leski, Sławomir Klimaszewski and Marcin Kurdelski

The Fatigue Life Assessment of PZL-130 Orlik Structures Based on Historical Usage Data

Material fatigue is the basic factor limiting aircraft's durability. It comes from the fact that changing loads affect aircraft structure as well as from the fact that aircraft's mass restrictions do not allow for diminishing stress to the level when material fatigue does not occur. Estimating fatigue durability of a particular structure as well as its actual fatigue damage degree is possible when the history of loads affecting the structure is known.

Accuracy of loads monitoring influences the accuracy of indicated fatigue wear. In case of older structures, which have been maintained according to safe life principle, the number of hours have been commonly used as a fatigue wear indicator. After aircraft structure reaches flying time estimated by the produces, it is considered as fatigue wear and it is no longer in service. In case of a lack of results of loads spectrum measurements, results of tests conducted for other aircraft (of similar structure and assignment) can be used. For this purpose, average loads spectrum has been elaborated for particular aircraft groups, for example, HELIX, FELIX, FALSTAFF, ENSTAFF, TWIST(10). In the case of small aircraft, the data from FAA (2) report have been often used.

This article describes the way of fatigue wear estimation for PZL-130 Orlik aircraft on the basis of historical data from flight recorders.

Open access

Piotr Reymer, Marcin Kurdelski, Andrzej Leski, Andrzej Leśniczak and Michał Dziendzikowski


The Su-22 fighter-bomber is a military aircraft used in the Polish Air Force (PLAF) since the mid 1980’s. By decision of the Ministry of National Defence Republic of Poland, the assumed service life for this type of aircraft was prolonged up to 3200 flight hours based on the Full Scale Fatigue Test (FSFT) results. The FSFT was conducted using the real load profile defined during the Operational Load Monitoring Program (OLM) and the 3200 hour service life was also based on this load profile.

In order to assure safe operation of all the 18 Su-22 aircraft, the Individual Aircraft Tracking program was introduced. The program was based on the results of the FSFT as well as the analysis of the flight parameters recorded by the THETYS onboard flight recorder.

In this paper, the authors present the methodology, assumed fatigue hypothesis and preliminary results of the IAT program for the Polish Su-22.

Open access

Marcin Kurdelski, Michał Stefaniuk, Wojciech Zieliński and Tomasz Bartoszek


The combat-trainer jet aircraft is an important element in the process of fighter pilot training. This type of aircraft provides a means of transition from basic training on low-speed propeller trainers to piloting high-speed and highly maneuverable fighter aircraft. Nowadays, in Poland, the PZL TS-11 “ISKRA” jet trainers, designed in 1960s, are employed for training purposes. Because of financial considerations this trainer hasn’t been yet replaced by modern aircraft that conforms to current specifications and needs.

As is the case with other aircraft in service of the PLAF, the TS-11 fleet has a large reserve of remaining Hourly Service Life (HSL). This opens an opportunity to extend the Calendar Service Life (CSL), so as it matches the HSL. To this end, a series of technical and research activities needed to be undertaken. The Air Force Institute of Technology is conducting the necessary verification of airframe structural conditions in cooperation with the Military Aviation Works No. 1 J.S.C. (branch in Dęblin) responsible for the overhaul and repair operations.

The AFIT’s activities in this program include:

  • deformation analysis of the selected surface areas of the wing and the fuselage;

  • assessment of hidden corrosion in riveted joints;

  • non-destructive testing of selected riveted joints.

This paper describes the deformation analysis. As of today, the first stage of the deformation inspection has been completed. At this stage, baseline surface measurements were obtained. Further inspections shall be performed cyclically. The future measurements will be used to establish the areas that deform due to the aircraft operation.

Open access

Piotr Reymer, Marcin Kurdelski, Andrzej Leski and Krzysztof Jankowski


The Su-22 fighter-bomber is a military aircraft used in the Polish Air Force since the mid 1980’s. By the decision of the Polish Ministry of Defense the predicted service life for this type of aircraft will be extended to 3200 flight hours. Due to the fact that some aircraft were nearing the end of the service life guaranteed by the manufacturer, the actual service life, determined based on the flight profile in the Polish Air Force, had to be validated. Consequently, the Full Scale Fatigue Test (FSFT) had to be carried out in order to verify that the required service life was attainable.

This article describes the process of preparation of the load spectra used in the Su-22 FSFT. Due to the fact that the Su-22 has a variable sweep wing the whole test was divided into three Stages (landing, flight and flap loads) carried out at different wing sweep angles (30°/45°/30°).

The spectra were developed using the historical data gathered from Flight Data Recorders (FDR), strain signals acquired during the Operational Load Monitoring program (OLM) and aerodynamic calculations.