I. Introduction
The fatal accidents data demonstrates there are about 23 percent of all fatal accidents take place in the landing phase from 2003 to 2012, though this phase just accounts for about 1% proportion in flight cycle [1]. One of the most dangerous potential flight accidents factors is hard landing. According to the servicing manual of Boeing Company, hard landing is defined as an event such that the vertical acceleration or speed exceeds the prescribed threshold. It may cause the damage of the wings, landing gear or plane structure [2]. To analyze the dynamic complex land process, the Quick Access Recorder (QAR) is widely used for aircraft health status monitoring. The QAR data contains variety of flight information. It is used in many methods to analyze landing status and aid decision-making in land process.