Flight Control System Performance Evaluation Technology Of Super-Low-Altitude Airdrop

In our national domestic constraction, there is a pressing need for super-low altitude airdrop techlonogy; which accurately drops heavy equipment from transport aircraft at a super-low altitude. At the duration of airdrop, the aircraft flies with low speed and altitude. Meanwhile, it is affected by various disturbances. Its requirements for Flight Control System (FCS) are more strict. To design required FCS, performance evaluation is very important.This thesis focuses on the performance requirements and evaluation method for FCS of super-low altitude airdrop, and developing evaluation software. Firstly, airdrop instrument and procedure were researched. Then, according to FCS' structure, it was proposed that the evaluation scheme should contain both flying qualities evaluation and airdrop task requirements.Flying qualities deal with the performance of Stability Augmentation and Control Augmentation loop of FCS.Task requirements deal with the performance of Control-Guidance loop.At the duration of airdrop, the aircraft slowly maneuvers and accurately tracks flight path. It should meet the category C flying qualities requirements for transport aircraft, specified in GJB-185-86. Based on these requirements, several flying quality criteria, which reflect the characteristics of airdrop, were studied, and then chosen to form an evaluation scheme. Equivalent system and linearazation are both essential technics used in flying qualities evaluation. Several algorithms, such as least-squares algorithm, maximum-likelihood algorithm, were studied. Their performance was compared through simulation. Finally least-squares algorithm was chosen as the equivalent system method applicating in evaluation software.In different phases of airdrop, the tasks of FCS are diffrent. So, this paper designed the airdrop task requirements for each phase. Requirements' range was determined attribute to the aircraft which was researched. As different task is, as the task environment is different too. It is important for FCS to adapt different environment. This paper analysised some environmental factors' influence on airdrop task performance, including cargo-weight, parachute-radius, wind, etc. Then Monte-Carlo method was used to evaluate task performance in different environment.After the requirements and method research, an evaluation software platform was developed for some airdrop FCS' performance evaluation. It is concluded that the evaluation scheme, which is discussed, is able to comprehensivey evaluate the performance of airdrop FCS. This thesis is pioneering and the result has a broad application prospect in engineering.