Online detection and avoidance of helicopter TGT limits

Turboshaft engines of rotary-wing aircraft impose limitations on the flight envelope via Turbine Gas Temperature (TGT). Pilots are required to react on possible violations by monitoring TGT limits. For a fly-by-wire system, avoidance of the TGT limit could be accomplished using tactile cues and advanced envelope protection algorithms. In this paper, a neural-network-based adaptive limit detection algorithm is used to estimate approaching TGT violations and the corresponding control limits on the collective control. Collective limits are then used for avoidance of the TGT limit. High fidelity helicopter and engine models are used to show that TGT violations can be estimated with sufficient lead time to warn the pilot using tactile cues.