Determination of loads in the ultralight helicopter blades

Abstract

The article describes research that was carried out on coaxial a single-seat ultralight helicopter Rotorschmiede VA-115 which is manufactured by German firm RS Helikopter GmbH. The purpose of the work was to determine the blades’ loads necessary for further blade fatigue analysis and ground bench tests. The methodology for the load determination consisted of deformation measurements using strain gauges in various flight modes from hovering to maximum speed flight, including climb, descent, acceleration, and braking. Ultralight helicopters occupy the smallest cost niche and, as a rule, full-fledged fatigue studies are not performed for such helicopters. The requirements for ultralight helicopters are also quite loyal, allowing them to pass such experiments. Analysis of the data shows that the amplitude of bending moments on the lower rotor is higher by 1.2 to 2 times the value on the upper rotor. The absolute maximum value of the bending moment is significantly greater at the minimum weight, although the oscillation amplitude becomes smaller. The presented data can be useful for designers of ultralight and UAV helicopters with teetering hinge rotors.

Keyword : ultralight helicopter, main rotor, blade, flight, tests