Power supply of aircraft flight control actuators in case of all propulsion engines failure

Аuthors

Ermakov S. A.^1*, Obolensky Y. G.^**, Sukhorukov R. V.^2***

1. Moscow Aviation Institute (National Research University), 4, Volokolamskoe shosse, Moscow, А-80, GSP-3, 125993, Russia
2. Kompani «Kronshtadt», 54-4, Malyi ave., Saint-Petersburg, 199178, Russia

*e-mail: ermakov1029@yandex.ru
**e-mail: y.obolensky@rsk-mig.ru
***e-mail: roman.sukhorukov@irkut.com

Abstract

The paper reviews a possible solution to the problem of power supply of the actuators of the main flight control surfaces, which ensures the safe controllable flight of a passenger airplane in case of failure of all of its propulsion engines. In this critical emergency situation the performance of the main sources of the hydraulic power degrades and the flow of the hydraulic fluid, which is generated by the pumps, approaches zero. If the propulsion engines can enter the autorotation mode, the process of degradation of hydraulic power to supply hydraulic power to the actuators of the main flight control surfaces. Such power supply could be combined with the power of the emergency ram-air turbine, which transforms the ram air energy into the hydraulic power by means of a turbo-pump unit.
The paper analyzes the process of degradation of the hydraulic power supply to the flight control actuators. This analysis shows that there are some time intervals, during which it becomes impossible to control the flight. The paper suggests carrying out a modification of a typical composition and configuration of the airplane onboard hydraulic system, which would ensure the controllability of the flight. The paper adduces the results of simulation of operation of the flight control actuators in case of all propulsion engines failure. The simulation is carried out for a typical composition and configuration of the onboard hydraulic system and for a modified system, which incorporates an additional emergency pump with a direct current electric drive. This additional hydraulic power source is only engaged temporarily during the time when the ram-air turbine and the turbo- pump unit are extended into the air flow. The additional hydraulic power source is disengaged after the feed rate of its pump stabilizes. The paper reviews a model, which simulates the process of degradation of the hydraulic power supply. It also adduces the results of simulation of actuation of the flight control surfaces, which was carried out with the help of the aforementioned model. These results show that the operation of the flight control actuators, which are driven by the harmonic input control signals, may be distorted substantially in case of the propulsion engines failure and RAT engagement. The abovementioned distortions of the processes of actuation of the flight control surfaces disappear after the incorporation of the emergency power unit into the onboard hydraulic system of the airplane.

Keywords:

hydraulic flight control system, passenger airplane, propulsion engines failure

References

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