Abstract: During on the spot measurement of airplane loading spectra, it is an annoying problem how to determine the flight takeoff landing number of minimum no loading measurement sampling economically and scientifically ensuring the typical representativity, science, comparability and revealability of actual measurement loading data above the confidence level of 90% in compiling airplane loading spectra home and abroad so far. According to t distribution theory, this paper proposes a criterion and estimation equations of the confidence level of normal mean population by which the flight takeoff landing number of minimum no loading measurement can be defined under a certain confidence level and error limit so that the flight takeoff landing number of minimum no loading measurement sampling can be determined.

Key words: t distr ibution theor y, the flight rising- falling number of minimum no-loading measur ement sampling, confidence level, design cr iter ion