Besides other aspects such as safety, capital expenditures, lifetime and maintenance of a wind energy converter, the power curve is the defining performance characteristic in order to derive its economic viability. Power curves for horizontal axis wind turbines have been studied, validated and optimized for decades. This study tackles the power curve estimation and optimization of airborne wind energy converters, in particular systems that use the so-called pumping, or Yo-Yo principle. A fast but detailed model of the pumping airborne wind energy system is used to calculate a family of power curves at different fixed altitudes. Based on these power curves a yield estimation method is presented which also considers power losses due to ice accretion, insufficient conditions for take-off and low visibility situations. Furthermore estimated yield values are presented for an example location.