Fundmental fatigue crack propagation tests with C-T type specimens were conducted at various load ratios (R) such as 0.1, 0.3 and 0.5 in T6 and Thermomechanically treated (TMT) conditions of 7039 Al alloy. Better mechanical properties from monotonic test as well as fatigue crack propagation were obtained by TMT process owing to uniform distribution of fine microstructures and non-existence of precipitation free zone (PFZ). Through the measurement of Kop and ${Delta}K$ at various R the concept of effective stress intensity factor range ratio, U was reviewed to asses the load ratio effect on fatigue crack propagation. A relationship between U and variables such as ${Delta}K$ and R was obtained empirically. This may enable us to predict ${Delta}K_{eff}$ that is of critical importance for prediction of fatigue crack propagation rate.