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

摘要

The transport aircraft response to atmosphericturbulence has been of great concern in recentyears among all kinds of adverse weatherconditions. The main focus is the suddenplunging motion with the abrupt change inaltitude because it affects the flight safety themost in severe atmospheric turbulence. Themain objective of this paper is to present acomparative analysis of flying qualities for anew and an aging twin-jet transports by usingthe eigenvalues of flight motion modes fortransport aircraft in severe atmosphericturbulence with sudden plunging motion intransonic flight. These two similar twin-jettransports are employed for comparativeanalysis. The longitudinal and lateraldirectionalmotion modes are analyzed throughdigital flight simulation based on decoupleddynamic equations of motion. The eigenvalueequations of the decoupled dynamic equationsof motion are polynomials of the 4th degree andtheir roots are solved with a quadratic factoringmethod based on the Lin-Bairstow algorithm. Itis shown that the magnitude of the imaginarypart of eigenvalues can be related to theseverity of plunging motion and can be used asa key parameter in describing the level of loadfactor it will reach. A low value of theimaginary part implies low system stiffness. Alow load factor reached in plunging motionshould affect flight safety the most.