Journal of KONES Powertrain and Transport, Vol. 26, No. 3 2019 GYROPLANE ROTOR HUBS STRENGTH TESTS Małgorzata Wojtas, Agnieszka Sobieszek Łukasiewicz Research Network – Institute of Aviation Department of Transport and Energy Conversion Division Krakowska Av. 110/114, 02-256 Warsaw, Poland tel.: +48 22 8460011 ext. 224 e-mail: malgorzata.wojtas@ilot.edu.pl agnieszka.sobieszek@ilot.edu.pl Abstract In this article a review of rotor, hub constructions were presented. Discussed rotor’s hub is made of composite or aluminum alloys materials. Two types of rotor hub were presented (four-blades and two-blades teetering rotor hub), each of them are dedicated to gyroplanes. Typical gyroplane main rotors are characterized by simple design, especially in case of rotors for light gyroplanes. In the following part of the article the type of strength tests required by certification process were shown. The test programs based on legal aspects of admission to the flight tests taking into account legislation such as CS 27 (Subpart C – Strength Requirements), CAP 643 British Civil Airworthiness requirements Section T Light gyroplanes, ASTM F2972. Furthermore, this article discusses strength tests of gyroplane rotor hub such as measured parameters, methodology of measurement, types of sensors, course of test, test stands, and limit loads. The loads during “pull-up from level flight” manoeuvre are limit loads during tests. Required additional processes, like a verification the same parameters by two types of method were shown i.e. deformation of structure were tested by strain gauges and reverse engineering. Strength tests had to be made before flight test, based on results of them aircrafts are flight authorized. In conclusion, the results of tests were presented and fulfilment of legal assumptions and requirements were shown. Keywords: gyroplane, strength tests, rotor hub, aviation regulations 1. Introduction This article discusses the one of the primary gyroplanes components – rotor hubs. At the beginning of work, the development of gyroplane rotor hubs is presented. Straight hubs with arms parallel to the rotor axis of rotation are presented up to more complex hub designs with a positive cone angle or four rotating hub arms. The main attention is focused on strength tests of the gyroplane rotor hubs. Shortly discussed strength tests based on the requirements contained in aviation regulations, like: ASTM F2972 (Standard Specification for Light Sport Aircraft Manufacturer’s Quality Assurance System) [7] for simple solutions of gyrocopter rotor hubs. The final goal focused on tests of the strength of the four-plane rotor hub designed for Class A gyroplanes (four- or six-seater gyroplanes). The scope of the tests was established with the Polish Civil Aviation Authority with reference to CAP 643 British Civil Airworthiness requirements Section T Light gyroplanes [2] and CS 27 – Small Rotorcraft (Subpart C – Strength Requirements) [4]. These tests were part of the type-certification tests for the newly designed gyrocopter rotor hub. 2. Gyrocopter rotor hubs review Main rotor of gyroplanes is rotating because of autorotation phenomenon, air flowing through the rotor disc is essential to generate rotation. The primary function of the gyroplane rotor is lift force generation needed to keep the machine in the air. The thrust is generated by a pusher or uncommonly tractor propeller. Most of gyroplanes are equipped with two-blade teetering main rotors with one centrally ISSN: 1231-4005 e-ISSN: 2354-0133 DOI: 10.2478/kones-2019-0082