Aerospace Technic and Technology

It is known that during operation or long-term storage, there is a significant deterioration (degradation) of the strength characteristics of the strength elements of the parachute canopy’s carcase, including shroud lines, canopy’s fabric, reinforcement tapes, free ends of the suspension system, leg straps, etc.

Parachutes are designed considering the specific safety factors of power elements for the extreme loads resistance at the moment of parachute opening. Further operation after the specified period with unchanged safety factors is possible only in flight conditions limitation, in particular, landing speeds. Strength characteristics are characterized by significant scattering. The design of parachutes is carried out considering the guaranteed values of destructive loads of elements with a given level of reliability. In this case, the law of destructive loads distribution must be known.

It was tested the normal distribution applicability of the strength characteristics applying the compound compliance criterion. The basis is the data of strength tests until the destruction of shroud lines samples and fabric of the canopy warpwise and wefting. The samples were cut from D-5 series 2 parachute of the year 1983, Z-5 reserve parachute of 1984, the rescue parachute C-5 K series 2 of the 1989. It was tested totally 301 samples of various materials from these parachutes. At the first stage of processing the test data, by experimental determination of the breaking load, the gross emissions were rejected, then a composite criterion for compliance with the normal law was applied.

According to the results of comparison with experimental data, the validity of the normal distribution of destructive loads for the shroud lines and canopy’s fabrics both warpwise and wefting is unambiguously shown.

The obtained result makes it possible to evaluate the strength characteristics of the carcase elements after operation or long-term storage with the required level of reliability and, in the future, to find the strength degradation factors of the power elements. These factors will limit the maximum allowed landing speed with a specific parachute.

strength; failure load; probability; distribution law; degradation coefficient

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Fomy`chev, P. A. Ustanovleny`e ograny`cheny`j po maksy`mal`num skorostyam desanty`rovany`ya s uchetom degradacy`y` prochnostnux xaraktery`sty`k matery`alov kupola parashyuta. Soobshheny`e 1. Zavy`sy`most` prochnosty` parashyutov ot degradacy`y` prochnostnux xaraktery`sty`k konstrukcy`onnux matery`alov [Setting limits on maximum landing speeds, taking into account the degradation of the strength characteristics of the materials of the parachute dome. Message 1. The dependence of parachute strength on the degradation of the strength characteristics of structural materials]. Aviacijno-kosmicna tehnika i tehnologia – Aerospace technic and technology, 2019, no. 1 (153), pp. 65-71. DOI: 10.32620/aktt.2019.1.08.

Fomy`chev, P. A. Ustanovleny`e ograny`cheny`j po maksy`mal`num skorostyam desanty`rovany`ya s uchetom degradacy`y` prochnostnux xaraktery`sty`k matery`alov kupola parashyuta. Soobshheny`e 2. Zavy`sy`most` maksy`mal`nux skorostej desanty`rovany`ya ot degradacy`y` prochnosty` [Setting limits on maximum landing speeds, taking into account the degradation of the strength characteristics of the materials of the parachute dome. Message 2. Dependence of maximum landing speeds on the degradation of strength]. Aviacijno-kosmicna tehnika i tehnologia – Aerospace technic and technology, 2019, no. 2 (154), pp. 61-68. DOI: 10.32620/aktt.2019.2.08.

State Standard 8.736-2011. The measurements are direct multiples. How measurements are processed. Moscow, Standartinform Publ., 2013. 20 p. (In Russian)