In numerical lifting surface calculations, assessment of convergence characteristics of number-sequences is a difficult task. Methods are investigated which needs no comparisons with other schemes. Among several kinds of convergence, the "N-r type" appears often in our practical investigations. For this type, a formulation is presented which gives a solution having a specified accuracy without iterative processes. It is an important requirement in order to save computation time. As a demonstrative model, a new method of chordwise quadrature "TrTr-NONEQ" is presented. This model verifies that the general formulation is sufficiently reasonable. In addition TrTr-NONEQ exhibits many advantages over other current, such as WAGNER'S, GAUSS' and CUNNINGHAM'S, methods.