News Column

Patent Issued for Flight Control System and Aircraft Comprising It

August 28, 2014

By a News Reporter-Staff News Editor at Computer Weekly News -- A patent by the inventors Sghairi, Manel (Toulouse, FR); Brot, Patrice (Ramonville Saint-Agne, FR); Aubert, Jean-Jacques (Pibrac, FR); De Bonneval, Agnan (Labege, FR); Crouzet, Yves (Ramonville Saint Agne, FR), filed on January 20, 2010, was published online on August 12, 2014, according to news reporting originating from Alexandria, Virginia, by VerticalNews correspondents.

Patent number 8805600 is assigned to Airbus Operations S.A.S. (Toulouse, FR).

The following quote was obtained by the news editors from the background information supplied by the inventors: "This invention relates to flight control systems (Flight Control Systems) present in aircraft.

"These flight control systems are at the interface between the flying means (joystick, rudder bar, etc.) and the various mobile flight surfaces of the aircraft (such as the vertical, horizontal rudders, the ailerons, the stabilizers, etc.).

"Modern airliners possess 'fly by wire'-type flight control systems in which mechanical actions on the flying means are converted into signals transmitted to actuators controlling the movement of the flight surfaces, these commands being transmitted to the actuators by advanced computers.

"These commands are calculated according to several types of laws. One of these laws, called normal law, is an assisted-flying law that reprocesses the flying instructions provided by the flying means in order to optimize the flying conditions (comfort of the passengers, stabilization of the airplane, protection of the flight domain, etc). Another law, known as direct law, is a law that only retranscribes the instructions for movement of the airplane transmitted by the electrical flight controls without reprocessing of these signals intended to improve flying performances.

"There already is known, as illustrated on FIG. 1, a flight control system 1 comprising a control module 2 having two sets of computers 4 and 5 so as to determine the control commands to be transmitted to actuators 3.

"Set 4 comprises two computers 4-1 and 4-2 capable of calculating the control of actuators 3 established according to the normal and direct control laws (these computers are called primary computers) and a computer 4-3 only capable of calculating this control established according to the direct law (this computer is called secondary computer).

"Set 5 comprises a primary computer 5-1 and two secondary computers 5-2 and 5-3.

"All these computers are installed in an avionic bay and communicate with the actuators via direct point-to-point analog links.

"The actuators are connected to one or two computers, with in the case of two computers a 'master/hold' architecture; the master computer ascertains the validity of the control signal transmitted to the actuator which ensures the integrity of the device. When the master computer breaks down, the computer 'on hold' takes over, which ensures that a computer is always available.

"In order to ascertain the validity of its command, each computer has a dual calculation unit structure (it concerns dual-path computers also called 'duplex' computers), not illustrated on FIG. 1.

"The first unit is a control (COM) unit which implements the processing necessary for carrying out the functions of the computer, namely determining a control signal to an actuator.

"The second unit is a surveillance or monitoring (MON) unit which for its part performs the same types of operations, the values obtained by each unit then being compared and, if there is a discrepancy that exceeds the authorized tolerance threshold, the computer is automatically disabled. It then becomes inoperative and is declared out of order so that another computer can substitute for it in order to implement the functions abandoned by this out-of-order computer.

"In this way each computer is designed to detect its own breakdowns and to inhibit the corresponding outputs, while indicating its condition.

"The hardware of the primary and secondary computers is different so as to minimize the risks of simultaneous failure of the set of computers (hardware dissimilarity).

"Moreover, the hardware of the two paths (COM and MON) of each computer is identical, but for reasons of security the software of these two paths is different so as to ensure a software dissimilarity."

In addition to the background information obtained for this patent, VerticalNews journalists also obtained the inventors' summary information for this patent: "The invention seeks to provide a flight control system that has a modified architecture in comparison with that of the prior art described above, at once less costly in hardware and software resources while meeting the same requirements for security and availability as the system of the prior art.

"To this end, it proposes a flight control system for an aircraft comprising:

"at least one actuator for a mobile flight surface of the said aircraft;

"a flight control module in communication with the said actuator, the said module comprising a first and a second computer, each computer being adapted for calculating a control command established according to at least one predetermined law for control of the said flight surface; characterized in that the said first computer, known as validating computer, comprises logical means adapted for comparing its control command with that of the said second computer, known as master computer, and for transmitting the result of the said comparison to the said actuator, the said actuator comprising logical means adapted for deciding, on the basis of this result, to execute or not to execute the command of the master computer.

"Unlike the COM/MON architecture of the prior art, here the validating computer does not decide on its own whether the command of the master is to be transmitted to the actuator, the command of the master is systematically transmitted to the actuator and it is the actuator itself which, by virtue of the logical means that it comprises, decides, according to the result sent back by the validating computer or computers of the master computer, to execute or not to execute the command of the master computer.

"Since a decision step is moved to the actuator, that makes it possible to produce simpler and less costly computers while providing a greater flexibility for the layout of the system.

"In this way it is possible, in particular, to associate a master computer with several validating computers or else to associate an actuator with several master/validating computer pairs in order to ascertain the reliability of the transmitted command with an increased security.

"This flexibility makes it possible in particular to use single-path computers (computers known as 'simplex,' that is to say devoid of redundant microprocessors) while preserving the same level of security.

"According to optional characteristics, the said master computer also comprises the said logic means for comparison.

"This makes it possible to make each computer multi-purpose, the functions between master and validating being able to be exchanged at any time according to failures of the computers, which contributes to making the system more flexible and to reducing the total number of computers required.

"According to other optional characteristics, the said actuator is in communication with a group of master computers, each master computer being associated with at least one validating computer of a group of validating computers, the said logic means of the said actuator being adapted for selecting the one to be executed from among the commands originating from the said master computers.

"The actuator is associated with several master computers in order to maximize the chances that a command originating from a master will be considered as valid and therefore can be reliable.

"According to other optional characteristics, the said logic means of the said actuator have a priority architecture.

"The master computers connected to the actuator thus are organized in order of priority in such a way that it is the first valid command according to this priority logic that is executed.

"According to still other optional characteristics, each validating computer is adapted for calculating the control command according to a program different from that of the master computer with which it is associated.

"For the same control law, the software dissimilarity for the calculation of a command between master and validating computers provides an additional security.

"According to still other optional characteristics, each computer is adapted for detecting when the computer with which it is associated is calculating the control command according to the same program and if such is the case, for being reconfigured to calculate this control command according to a different program.

"In this way the software reconfiguration makes it possible to maximize the use of each computer which contributes to minimizing the total number of computers while preserving, for the same control law, a software dissimilarity between master and validating computers.

"According to still other optional characteristics:

"the said actuator comprises a control unit and a unit for monitoring the said control unit;

"each unit is connected to at least one master computer and to the associated validating computer; and/or

"one of the units is only connected to a master computer and the other is only connected to the associated validating computer, the said control and monitoring units also being connected to one another.

"The connecting of the control and monitoring units of the actuators with the computers thus can be accomplished directly or indirectly (through the other unit).

"In a second aspect, the invention also applies to an aircraft equipped with a system such as explained above."

URL and more information on this patent, see: Sghairi, Manel; Brot, Patrice; Aubert, Jean-Jacques; De Bonneval, Agnan; Crouzet, Yves. Flight Control System and Aircraft Comprising It. U.S. Patent Number 8805600, filed January 20, 2010, and published online on August 12, 2014. Patent URL:

Keywords for this news article include: Software, Airbus Operations S.A.S..

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Source: Computer Weekly News

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