Lessons learnt from Boeing 737 MAX accidents about human factor considerations in aircraft design and certification

Recently two newly certified Boeing 737-8 (MAX) (Lion Air flight JT610 and Ethiopian Airlines flight ET302) crashed within 4 months resulting in 346 fatalities. The causes of both accidents are similar: the unintended and repetitive activations of the Maneuvering Characteristics Augmentation System (MCAS), which resulted in repetitive aircraft nose down commands through horizontal stabilizer trim. The crews were not able to resolve the abnormal situation. Flight LNI043 just preceding the JT610 accident faced a similar situation resolved with major difficulties. MCAS is a flight law, implemented in Flight Control Computers (FCC), introduced by Boeing in B737 type definition as part of the modification from NG to MAX and certified under FAA regulations, the resulting amended type certificate being validated by various other aviation authorities

Safety and Certifiability Evaluation of Distributed Electric Propulsion Airplane in EASA CS-23 Category

Distributed Electric Propulsion (DEP) is one of the unconventional airplane architectures of interest in the quest for decreasing aviation environmental footprint. This configuration integrates strong and innovative couplings between systems and aircraft design disciplines. To address limitations of the traditional approach for certification and of the associated means of compliance when certifying innovative products, the European Union Aviation Safety Agency (EASA) issues in 2017 a novel certification philosophy that relies on high-level objective-based safety requirements. In this context, this paper presents a safety and certifiability evaluation of DEP airplane in EASA CS-23 category, with a methodology for aircraft-level safety assessment during preliminary design, a certification gap analysis with regards to existing means of compliance, and some proposals to clear the certification path for DEP configuration

Reduction of Vertical Tail Using Differential Thrust: Influence on Flight Control and Certification

International audienceThe flight control characteristics and certification compliance of a Distributed Electric Propulsion (DEP) aircraft using differential thrust is studied through exploration of flight envelops. Identification of critical flight phases specific to the use of propulsion systems as actuators for flight control is performed. In particular the influence of engine failures on the flight envelop and means of mitigation are given. It is concluded that an aircraft using differential thrust has a most advantageous flight envelop at the point of neutral directional static stability allowing a reduction of 45% of the vertical tail surface area. Additionally, the directional control could be entirely provided by differential thrust, eliminating the need for a rudder. Study of this type of aircraft showed specific failure modes that differ from the actual certification prescriptions. New more relevant definitions and parameters are proposed as basis to demonstrate compliance with high level certification objectives

A Formal Framework for Modeling and Prediction of Aircraft Operability using SysML

Aircraft operability characterizes the ability of anaircraft to meet operational requirements in terms of reliability, availability, risks and costs. Airlines policy must cope with operational decision-making and maintenance planning to handle the impacts of any event that generates a maintenance demand during operations. Aircraft operability is therefore considereda major requirement by each airline. The subject reaches a complexity level that deserves investigations in a Model-Based System Engineering (MBSE) approach enabling abstractions, as well as simulation and formal verification of models. In this paper, aircraft operability is modeled using Finite State Machines(FSM) supported by SysML. Simulation and model checking techniques are used to evaluate the impact of an event on airline operations using operability Key Performance Indicators (KPIs)such as reliability, availability and cost. The modeling frameworkis demonstrated on a case study of air-conditioning pack. This kind of operability analysis helps to project the potential impactof aircraft design on airline operations early in the aircraft development

FAST-OAD-GA: an open-source extension for Overall Aircraft Design of General Aviation aircraft

In order to respond to the growing need for a reduced environmental footprint of the commercial aviation sector, new aircraft architecture and propulsion technology have become a major focus in the aerospace research field. In this context, many new projects featuring innovative configurations or powertrains, for which light aircraft are under consideration as final products or as small scale test platforms for larger airplane, have taken shape. The assessment of the feasibility of such concepts requires an Overall Aircraft Design (OAD) study at a preliminary stage in order to rule out non-viable design choices and identify key features. Consequently, OAD tools play a key role during the conceptual design phase as they allow to automatically carry out said studies and, using their Multidisciplinary Design Analysis and Optimization capabilities, identify the most likely design. FASTOAD- GA, an open-source extension of FAST-OAD completes the aircraft design techniques from FAST-OAD with general aviation specific models to enable the preliminary sizing of aircraft regulated by the EASA CS-23. This paper presents the FAST-OAD framework, its capabilities, the models added by FAST-OAD-GA for general aviation aircraft sizing and the upcoming changes to model innovative architectures

Operability projection of major aircraft components during early aircraft design

Aircraft operational performance is a key factor to achieve airline profitability and meet passenger expectations. It is determined by the ‘operability’ of major aircraft components along with the operational context in which the aircraft operates. Operability is the ability of a system to meet its operational requirements in terms of reliability, availability and costs. This paper proposes a approach to take into account the type of technology employed in a major aircraft component to perform operability projections. An operability model is developed using Bayesian networks that helps project the influence of different input parameters on the operational performance of the major aircraft components. An approach combining engineering and in-service data is used to instantiate the different parameters and train the Bayesian network model. The trained model can be used by system designers to perform operability projections of different design solutions through Bayesian inference and make trade-off studies from an operability point of view. Clustering of the data using unsupervised learning is also addressed in this paper to identify the best combinations of input parameters that can produce the desirable operational performance

Hybrid electric distributed propulsion overall aircraft design process and models for general aviation (FAST GA)

In the frame of the European objectives in terms of CO2 emissions, the aeronautics is looking for a technological rupture to achieve them, in particular, the aircraft design domain pursuits this through the research of innovative architectures. One of these innovative configurations currently being explored includes the hybrid electric energy source (thermal/electric) for Distributed Electric Propulsion (DEP) architecture. This Paper details a code developed to size a general aviation aircraft at concept level, by only defining its top level requirements and the main architecture parameters. The code can manage both conventional and hybrid power source as well as concentred or distributed propulsion architectures in order to allow the user to evaluate and compare the feasibility and benefits respectively of these innovative architectures. This code is a branch of the code “FAST-CS25” (Future Aircraft Sizing Tool for conventional CS-25 type) held by ONERA/ISAE-SUPAERO. The presented work aims at the expansion of the FAST code to CS-23 conventional type, hybrid electric energy source, and distributed propulsion system configurations. Through this paper, the models and the main sizing loops for the concept design are described, but putting special emphasis on the distributed propulsion aerodynamics and wing mass estimation. These detailed models where validated with the NASA X-57 DEP aircraft satisfactory. The whole concept design loop of a hybrid energy aircraft was validated with the eGenius hybrid energy aircraft

Wing Structural Model for Overall Aircraft Design of Distributed Electric Propulsion General Aviation and Regional Aircraft

International audienceIn the context of reducing the environmental footprint of tomorrow’s aviation, Distributed Electric Propulsion (DEP) has become an increasingly interesting concept. With the strong coupling between disciplines that this technology brings forth, multiple benefits are expected for the overall aircraft design. These interests have been observed not only in the aerodynamic properties of the aircraft but also in the structural design. However, current statistical models used in conceptual design have shown limitations regarding the benefits and challenges coming from these new design trends. As for other methods, they are either not adapted for use in a conceptual design phase or do not cover CS-23 category aircraft. This paper details a semi-analytical methodology compliant with the performance-based certification criteria presented by the European Union Aviation Safety Agency (EASA) to predict the structural mass breakdown of a wing. This makes the method applicable to any aircraft regulated by EASA CS-23. Results have been validated with the conventional twin-engine aircraft Beechcraft 76, the innovative NASA X-57 Maxwell concept using DEP, and the commuter aircraft Beechcraft 1900

Wing Structural Model for Overall Aircraft Design of Distributed Electric Propulsion General Aviation and Regional Aircraft

In the context of reducing the environmental footprint of tomorrow’s aviation, Distributed Electric Propulsion (DEP) has become an increasingly interesting concept. With the strong coupling between disciplines that this technology brings forth, multiple benefits are expected for the overall aircraft design. These interests have been observed not only in the aerodynamic properties of the aircraft but also in the structural design. However, current statistical models used in conceptual design have shown limitations regarding the benefits and challenges coming from these new design trends. As for other methods, they are either not adapted for use in a conceptual design phase or do not cover CS-23 category aircraft. This paper details a semi-analytical methodology compliant with the performance-based certification criteria presented by the European Union Aviation Safety Agency (EASA) to predict the structural mass breakdown of a wing. This makes the method applicable to any aircraft regulated by EASA CS-23. Results have been validated with the conventional twin-engine aircraft Beechcraft 76, the innovative NASA X-57 Maxwell concept using DEP, and the commuter aircraft Beechcraft 1900

A preliminary comparison study between conventional and more-electrical regional aircraft using Pacelab

Today’s engineers are facing new challenges when it comes to implementing more-electrical architectures, specifically within the aviation industry. Therefore, tools such as Pacelab Suite can be used to conduct preliminary analysis of such modern architectures within an aircraft for a specific designed mission. This work mostly pertains to the development and analysis between a conventional and a more-electric architecture of a regional aircraft on Pacelab. Conventionally, three types of non-propulsive power are used to drive the various sub-systems in an aircraft: hydraulic, pneumatic and electrical sub-systems. Recently, a trend towards more-electrical architecture is being adopted in the aviation industry owing to the many drawbacks identified with conventional sub-system architecture. The conventional architecture of a large regional aircraft (ATR-72) was studied and the complete architecture of the electrical, hydraulic, flight controls, fuel and pneumatic systems is modelled using the Pacelab Suite. The conventional model of the aircraft is subjected to different scenarios in order to evaluate the aerodynamics, fuel consumption and electrical energy performance for a comparison with more electrical versions. The intent of this work is to analyze whether one of the two architectures significantly outperforms the other considering a mission-level metric. Further, it is also planned to subject the more-electric model to the same scenarios as the conventional model and draw conclusions on the merits and demerits of introducing More-Electric Aircraft (MEA) architecture in a regional aircraft