31th Congress of the International Council of the Aeronautical Sciences

06.1 - Flight Dynamics and Control (Control & Modelling)


M. Sato, Japan Aerospace Exploration Agency, Japan

It is well known that Japan Airlines Flight 123 accident is one of the most tragic accidents in the past accidents. The main cause of the accidents was identified as the loss of aerodynamic control devices, i.e., elevator, aileron and rudder, and spoilers, etc., which was caused by the loss of the hydraulic pressure due to the destruction of the rear pressure bulkhead in the fuselage. However, at the same time, the stability of aircraft motions was also decreased; that is, the damping of oscillatory motions, e.g. Phugoid mode and Dutch-roll mode, became drastically decreased, and the uncomfortable motions continued until the crash of the airplane. In a posteriori analysis and some independent researches in USA (so-called “Propulsion Controlled Aircraft” in short "PCA"), it has been well demonstrated that it might be possible to control the faulty JAL 123 aircraft with only thrust, because the onboard multiple engines were operative by pilot throttle commands. However, neither the decrease of the stability nor the oscillatory motions due to wind gust have been realized in those researches. In this paper, by using the controller design technique in the literature, we realize the situation in which gust response as well as handling response are simultaneously realized with JAXA’s research airplane MuPAL-alpha, which has an ability to mimic other aircraft motions (this property is referred to as “In-Flight Simulator”, in short “IFS”), and examine the maneuverability assessment with the IFS under the condition that the Dutch-roll mode is marginally stable, viz. the gust response continues almost without decreasing. The flight tests confirmed that, even in the situation that Dutch-roll damping is severely reduced, maneuverability is kept and a faulty aircraft is controllable by manual pilot inputs as long as control devices are effective.

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