EVALUATIONS OF FLYING QUALITIES FOR A NEWAND AN AGING TRANSPORT AIRCRAFT IN SEVERE ATMOSPHERIC TURBULENCE

摘要

The transport aircraft response to atmospheric turbulence has been of great concern in recent years among all kinds of adverse weather conditions. The main focus is the sudden plunging motion with the abrupt change in altitude because it affects the flight safety the most in severe atmospheric turbulence. The main objective of this paper is to present a comparative analysis of flying qualities for a new and an aging twin-jet transports by using the eigenvalues of flight motion modes for transport aircraft in severe atmospheric turbulence with sudden plunging motion in transonic flight. These two similar twin-jet transports are employed for comparative analysis. The longitudinal and lateraldirectional motion modes are analyzed through digital flight simulation based on decoupled dynamic equations of motion. The eigenvalue equations of the decoupled dynamic equations of motion are polynomials of the 4th degree and their roots are solved with a quadratic factoring method based on the Lin-Bairstow algorithm. It is shown that the magnitude of the imaginary part of eigenvalues can be related to the severity of plunging motion and can be used as a key parameter in describing the level of load factor it will reach. A low value of the imaginary part implies low system stiffness. A low load factor reached in plunging motion should affect flight safety the most.