Propeller Aircraft Design Optimization for Climate Impact Reduction

This paper studies the climate impact of propeller aircraft which are optimized for either minimum direct operating costs, minimum fuel mass, or minimum average temperature response (ATR100). The latter parameter provides a measure of the global warming impact of the aircraft design, considering both CO2 and non-CO2 effects. We study turboprop-powered aircraft in particular because these offer higher propulsive efficiency than turbofan aircraft at low altitudes and low Mach numbers. The propeller aircraft are designed for medium-range top-level requirements, employing a multidisciplinary design optimization framework. This framework uses a combination of statistical, empirical, and physics-based methods, which are verified using existing engine and aircraft data. For this medium-range design case, a climate impact reduction of 16% can be realized when shifting from the cost design objective to the climate objective. The optimal solutions for the fuel mass and climate objectives are nearly identical as CO2 and other fuel proportional climate effects are the main contributors. The effects of NOx and contrails are lower than for the turbofan aircraft due to the lower cruise altitude of the propeller aircraft. Compared to turbofan data, propeller-powered aircraft can achieve a further 33% reduction in climate impact, comparing both climate-optimal designs. This reduction is lessened to 23% when the propeller aircraft is constrained to achieve the same mission block time as the turbofan aircraft. Note that these reductions in ATR100 require a propeller efficiency of 88%. Overall, the results show that the utilization of propeller-powered aircraft in the medium-range category can further reduce the climate impact compared to climate-optimal turbofan aircraft designs.