Safety & Energy Efficiency Research on Advanced More Electrical Flight Control Actuation Systems for Short/Middle Range Passenger Aircraft

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Safety & Energy Efficiency Research on Advanced More Electrical Flight Control Actuation Systems for Short/Middle Range Passenger Aircraft


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        <identifier identifierType="DOI">10.23723/10638/20085</identifier><creators><creator><creatorName>V. Kuvshinov</creatorName></creator><creator><creatorName>L. Khaletsky</creatorName></creator><creator><creatorName>A. Steblinkin</creatorName></creator><creator><creatorName>E. Erofeev</creatorName></creator><creator><creatorName>A. Skryabin</creatorName></creator></creators><titles>
            <title>Safety &amp; Energy Efficiency Research on Advanced More Electrical Flight Control Actuation Systems for Short/Middle Range Passenger Aircraft </title></titles>
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	    <date dateType="Created">Sun 1 Oct 2017</date>
	    <date dateType="Updated">Sun 1 Oct 2017</date>
            <date dateType="Submitted">Sat 17 Feb 2018</date>
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Safety & Energy Efficiency Research on Advanced More Electrical Flight Control Actuation Systems for Short/Middle Range Passenger Aircraft V. Kuvshinov, L. Khaletsky, A. Steblinkin, E. Erofeev, A. Skryabin. Central Aerohydrodynamic Institute named after N.E. Zhukovsky (TsAGI) 1 Zhukovsky st., Zhukovsky, Moscow Region, 140180, Russian Federation Abstract The trend in aircraft systems development to overall electrification includes electrification of flight control actuation system (FCAS). Preliminary analysis shows the absence of profits including weight saving obtained by replacement of electrohydraulic actuators with different kinds of electrical ones presented on the market (electromechanical (EMA) and electrohydrostatic (EHA) actuators) within the scope of traditional architecture. So reasonable FCAS electrification should be done by revision of classical architectures with step by step implementation of electric actuators into new types of architectures while EMA & EHA technologies improves. Four possible architectures of advanced more electric FCAS for short/middle range passenger are proposed in the paper. Safety and energy efficiency of these architectures are under consideration. FCAS failure rates, weight savings in comparison to traditional architecture and reduction of power taken from the jet-engines obtained under RESEARCH European-Russian coordinated project are presented in the article. Introduction Aircraft systems electrification has become an aerospace industry trend during the last decade [1,2]. The electrification of the flight control actuation system (FCAS) is just the part of this process, w hich led to the rapid development mainly of tw o technologies for aerodynamic flight control surfaces deflection using electromechanical (EMA) and electrohydrostatic (EHA) actuators. The technologies have already been implemented on different airplanes (A-380, A-350, B-787, F-35 etc.) and development efforts have already gave some benefits in terms of energy redistribution, w eight savings and others [3,4]. Further «deep» FCAS electrification promise to give additional profits mainly in terms of maintenance costs and increasing of overall aircraft energy efficiency. But it’s obvious that the replacement of electrohydraulic servovalve actuators (EHSA) w ith electrical ones w ithin the scope of traditional FCAS architecture w ill not led any w eight savings due to more pow er density ratio (actuator mass to its output pow er) in comparison to traditional hydraulically pow ered actuators. The research presented in the paper aims at development of such «more electric» FCAS architectures for short/middle range passenger aircraft w hich: - Satisfy the current level of flight safety requirements (FAR-25/CS-25) or exceed it; - Allow s to reduce overall w eight of the FCAS w ith A/C energy complex and implement more economical energy utilization onboard. As the result the new architecture should lead to fuel efficiency grow th by 8-10% for short/mid range passenger aircraft. The research is done in the frame of RESEARCH (REliability & Safety Enhanced electrical actuation system ARCHitectures) European-Russian collaboorative project. Advanced FCAS architectures brief description There’re four types of more electric FCAS architectures proposed and estimated. The traditional architecture w ith three centralized hydraulic systems w as used as the basis to compare w ith architectures developed. More electric FCAS architecture proposed are: 1. Architecture w ith the use of «electrical w ing» concept – all aerodynamic surfaces on the w ing are deflected by EMAs. Other surfaces are deflected traditionally – by EHSA pow ered from three centralized hydraulic systems. 2. Architecture w ith the use of «electrical w ing» concept w ith tail and stabilizer surfaces deflecting by EHSA pow ered from three local hydraulic systems placed at the rear part of an A/C (despite architecture 1). 3. Architecture w ith the use of «electrical w ing» concept w ith part of tail and stabilizer surfaces deflecting by electrical back-up hydraulic actuator (EBHA) w ith combined speed regulation pow ered in normal operational mode from tw o local hydraulic systems placed at the rear part of an A/C and part – deflecting by EHAs pow ered directly from electrical system. 4. Architecture w ith total electrification – «electrical w ing» plus «electrical rear part» - elevators and rudder are deflected by EHAs. Within all of these architectures the roll control is suggested to shift from ailerons to differentially deflected elevators to w ithstand poor dynamic characteristics of EMA on ailerons at low control signals. Safety assessment As FCAS is a complicated technical system, consisting of set of separate elements and subsystems, its performance capabilities altogether depend on performance capabilities of its elements and number of interactive aircraft systems. So fault- tree analysis has been used for FCAS reliability analysis. General admissions used in reliability calculation of each control channel (directional, longitudinal and lateral) consist of follow ing points: 1. The loss of one of three control channels is treated as a catastrophic situation. According to aviation rules (FAR-25/CS-25) catastrophic situation is extra situation w hen prevention of loss of life is almost impossible. Therefore the probability of the occurrence of such event must not exceed 10 -9 per 1 flight hour; 2. The probability of electronic control unit (ECU) electric pow er failure occurrence (27 V) is accepted as 10 -9 , because actuators and their ECUs are directed to 1 st category consumers, for w hich the probability of failure occurrence on non- pow er supply is limited by pointed quantity; 3. EHSA’s elements are understood as the group of elements (control valve, actuation cylinder, electromechanical converter etc.) w hich provide actuator w ith functioning of servo unit; 4. EHA’s elements are understood as the group of elements (electric engine, pow er converter, pump, reverse valve, linear drive, actuation cylinder etc.) w hich provide electrohydrostatic actuator w ith functioning of servo unit; 5. During calculations it is taken that reliability of identical elements of electrical pow er system, ECUs, hydraulic system, actuators of each backup channel have identical reliability and characteristics of structure identity. The reliability analysis w as made taking into account fail-safe indexes of full energy complex (including jet engine) of modern aircraft. Special attention w as paid to the failure sequence in the actuation system and sw itching to backup actuators. The calculations also take into account the reliability of the sw itching devices. The results of the reliability analysis for the most critical control channel – longitudinal are presented below . These results show the probability of loss of elevator control per one flight hour. Table 1: The results of reliability analysis for longitudinal control channel. In conclusion of the reliability analysis the main references are maid in order to increase the reliability of more electrical flight actuation system and it’s energy complex. Energy & Weight profits assessment The numerical analysis of FCAS energy efficiency (including w eight savings) w as performed through the follow ing steps: 1. Forming the input data on w eight, consumed/produced pow er, pow er density and energy efficiency factor for flight control actuation system elements and systems producing hydraulic and electrical pow er; 2. Assessment of the energy consumed by different groups of actuators and after that assessment of minimal necessary installed pow er of sources for pow er supply of this different groups; 3. Assessment of summary energy taken from the jet-engines for the FCAS operation; 4. FCAS and energy complex summary w eight assumption or its variation w hile shifting to more electric architecture from traditional one. It critical to note that w eight change assessment include: - Assessment of «direct» w eight change due to changes in systems structure (the number and the nature of its elements), e.g. the use of electrical actuators instead of EHSA or elimination of hydraulic system etc.; - Assessment of w eight change caused by the change of pow er sources (electro- or hydro-) installed pow er w ith the use of mass to pow er ratios; FCAS energy consumption assessment also should include the analysis based on the mathematical modelling of the aircraft energy complex during various flight profiles. That task w as out of the scope of the project and it has the status “to do” at the moment. The results of the research for advanced short/middle range passenger airplane are presented below . Table 2: The results of w eight assessment of different architectures. Conclusions In case new electrical systems w ill be developed, the most promising FCAS architecture is «electrical w ing» (only EMAs are used for w ing surfaces deflection) w ith local hydraulic systems in A/C rear part implementation for pow ering traditional electrohydraulic servoactuators. Additional energy profits can be archived through the implementation of SMART hydraulic system concept w ith pressure and flow rate adaptation to the tail and stabilizer actuators w orking conditions. It should be noted that the revision of FCAS architecture w ill require the new approach to aircraft energy complex development such as increase of the number of airborne electrical systems, decrease of its fault occurrence probability and others. References 1 Konstantinov S. et al, Flight control actuation systems development concept for advanced airplanes, Russian scientific and technical Journal «Flight» (Polet), 2008, Vol. #1. 2 The status and results of R&D projects for advanced electrohydrostatic actuators for Airbus airplanes flight control systems. Foreign papers and articles overview , FSUE «Standardization and Unification Institute» (NIISU), 2003, Vol. 1. 3 Van de Bossche D., The A380 flight control electrohydrostatic actuators, achievements and lessons learnt, ICAS 2006 conference. 4 Nintzel A. Design Study for an Electrohydrostatic Actuator for an A330/340 inboard aileron // Recent Advances in Aerospace Actuation Systems and Components. – Toulouse, France, 2001.