Unique Operating Conditions Analysis of Turboshaft Engines Based on Nonlinear Integrated Model

The unique mission of the helicopter compared to the fixed-wing aircraft introduces challenges to the aerodynamic stability of the turboshaft engine. Thus, the assessment of the availability of stability margin for special operating conditions in the envelope of this equipment is required to guarantee flight safety. In this paper, a rapid nonlinear complete engine method is developed to investigate the effect of helicopter ground-effect operation and high-altitude hovering on aerodynamic stability by considering factors including inlet distortion and component matching. Research indicated that the most dangerous point of stability margin in a unique section of the flight envelope is high altitude hovering, with about a 16.7% reduction in available stability margin compared to standard ground test conditions. This paper also investigates the effects of typical helicopter ground effects on a turboshaft engine and shows that the stability margin will be reduced by a maximum of 1.43% in hovering if the influence of ground effects in the flight envelope is not considered in the design.