Beyond Efficiency: A Unified Energy Survival Law for Aviation and Rotorcraft Systems

Classical efficiency metrics are widely used to evaluate the performance of aviation systems, yet theyoften fail to explain the persistent saturation observed in aircraft range, helicopter hover endurance,and unmanned aerial vehicle (UAV) flight time. Modern propulsion systems already operate near highthermal or electrical efficiency, but improvements in engine performance do not translateproportionally into mission-level gains. This study introduces a Unified Energy Survival–Conversion Lawthat explains these limitations by recognizing that useful output is governed by the fraction of energythat survives irreversible degradation across multiple stages before being converted into useful work.The framework defines an energy survival factor (Ψ) representing the persistence of absorbed energyagainst aerodynamic losses, induced flow, turbulence, and entropy generation, and an internalconversion competency (Cint) describing the finite ability of a system to transform surviving energy intolift, thrust, or mission output. Together, these variables yield a universal relation: Euseful = Ein × Ψ ×Cint. Application of the model to fixed-wing aircraft, helicopters, and UAVs demonstrates that aviationperformance is fundamentally survival-limited rather than efficiency-limited. The framework provides athermodynamically consistent basis for diagnosing performance saturation and guiding survival-centricaerospace system design. Please check the attachment for details