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Comparative Analysis of the Load Spectra Recorded During Photogrammetric Missions of Lightweight Uavs in Tailless and Conventional Configurations

Rodzewicz Mirosław, Głowacki Dominik, Hajduk Jaroslaw

Fatigue of Aircraft Structures

2022

Iss. 14

114--134

The purpose of this article is to present the results of the investigation regarding the differences of the load spectra of two unmanned fixed-wing aircraft performing photogrammetry missions: X-8 (flying wing) and PW-ZOOM (conventional configuration). The focus was on the analysis of a number of load cycles for various load increments within the range of the operational loads. The load spectra were determined using the acceleration signal recorded in the autopilot logs as an input. This signal was transferred to the chain of local extreme values scaled in the form of discrete load levels, and then the transfer arrays were derived with use of the rainflow counting algorithm. On this basis, the incremental load spectra were determined for each flight. These load spectra were subjected to statistical analyses to determine the load spectra representative of the flight sessions in a few ways between non-conservative (i.e., focused on average load histories) and conservative (i.e., focused on the worst load histories observed during the flight session). Finally, the fatigue life was calculated by having the structural element of the assumed fatigue properties subjected to the load spectra of both airplanes. A large (exceeding one order of magnitude) difference in the number of load cycles for larger load increments in the analyzed load spectra was shown. This difference is related to the different dynamic characteristics of the two aircraft, in particular the gust response. As a result, there is a several-fold difference in fatigue life.

Impact Loads and Crash Safety of the Cockpit of a Composite Glider

Lindstedt Łukasz, Rodzewicz Mirosław, Rzymkowski Cezary, Kędzior Krzysztof

Fatigue of Aircraft Structures

2019

Iss. 11

39--55

One major problem associated with gliding is the safety of the crew during landings in the country outside the airfield. The analysis of glider-accident statistics shows that such out-landings may significantly influence the safety. Therefore, of vital importance are the crashworthiness properties of the glider fuselage structure. The subject of the study was the PW-5 glider fuselage made of composites and subjected to high loads typical of glider crashes. The aim was to provide experimental data for validation of a numerical model of the cockpit-pilot system during impact. Two experimental tests with the composite glider cockpit were performed using a typical car-crash track. During the first test the cockpit with a dummy inside was crashed onto the ground at the angle of 45 degrees at a speed of 55 km/h. Accelerations and deformations at chosen points in the cockpit as well as signals coming from the dummy sensors and forces in the seat belts were recorded. The second test was an impact into a concrete wall at a speed of about 80 km/h. The full-scale tests were accompanied by a number of quasi-static and dynamic laboratory tests on samples of composite material. The experimental tests provided valuable results for the parametrical identification of a simulation model developed using the MADYMO software.