The Device and Method for the Aircraft Steel Ropes Assessing Based on the Tests with the Tensile Testing Machine

Aeronautical and Space-Rocket Engineering


Аuthors

Ageev A. G.*, Kozlov V. V.**, Garyunov D. S.***

Company «Tupolev», 17, nab. Akademika Tupoleva, Moscow, 105005, Russia

*e-mail: snaker-tema@mail.ru
**e-mail: gdanil.s@mail.ru
***e-mail: vickt.kozloff@yandex.ru

Abstract

With a view to the introduction of sanctions against Russia in recent years, including new aviation equipment supply, the issue of the aircraft and their associated items airworthiness maintaining in operation has become increasingly acute. An equally pressing problem is the increase and extension of the service life of steel rope, which are used, in particular, in engine control systems, as well as the transfer of rope to the method of technical operation by condition instead of operation by service life.
Laboratory defective studies of rope, static tension tests according to State Standard 2172-80 on a tensile testing machine and cyclic tension according to State Standard 2387-80 on a rolling test bench, based on the results of trial operation of leading and main objects, are being conducted to extend their service life.
In the course of the work on extending the service life of the steel ropes installed on long-range aviation products, an analysis of regulatory documentation for the aircraft steel ropes and their testing methods was performed, and deficiencies in rolling machines for cyclic tension testing of the steel rope according to State Standard 2387-80 were identified. Laboratory defect testing of the steel rope with operating time was conducted, and diagrams of cable diameter change along its length were plotted.
Variants of a portable device similar in technical essence to the rolling machines according to State Standard 2387-80 were developed, allowing simulate the steel rope bending during its operation on rollers and its wear due to the reciprocating movement of the steel rope on rollers to approximate the test conditions to operational ones. Development of the device, which allow to conducting endurance tests of the aircraft steel rope on a tensile testing machine opens possibility to abandon the design, production and certification of a separate rolling test benches according to State Standard 2387-80.
To reduce the test equipment operating time, the tests were not conducted until the rope breakage, but until a specified number of loading cycles, which correspond to the number of engine control lever response cycles for the designated service life of the aircraft, were achieved.
The tests for extending the designated service life of the steel rope were performed in the shortest possible time with a labor intensity eightfold less than that predicted for the rolling test-bench. It allowed ensuring urgent duty of the AT products without the need to put the products in operation for repair and perform a labor-intensive operation to replace the steel rope cable run. The tests were conducted at the Moscow site of the JSC Tupolev without transferring this volume of work to the third-party organizations and to other regions of the Russian Federation, which will allow employing the created production reserve for the future service life tests and studies.
Processing of the endurance test results was reduced to the compliance determining of the set of obtained test results with the normal distribution law with the known methods of mathematical statistics by checking the equality of standard deviations using the F-test and checking the equality of average values by the Student's t-test. Scatter diagrams of residual strength, allowing predict the service life of the steel rope prior to the write-off without the need for visual inspection and destruction of the samples, reducing the operating time of the testing equipment by 40% were plotted.

Keywords:

aircraft steel rope, engine control system, endurance tests, extension of the service life, residual strength, tensile testing machine

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