The paper proposes a solution to the problem posed by the inclusion of complex interstage nodes into communication networks. Thus nodes are prone to exhibit failure modes that may lead to repetitive errors that breach the usual set of assumptions considered for medium-level protection mechanisms. The specific class of application targeted (e.g., servomechanisms controlling flight control surfaces) is characterized by: i) slow dynamics of the controlled processes does not impose a high integrity level for each transmitted message, but rather for a set of successive messages, ii) the reference values assigned during the mission (e.g., cruise phase) are expected to be maintained identical for several cycles, and thus should the protection fail for one message, then it will be the same for subsequent messages. To cope with this, the proposed integrity protection scheme features distinct error coding functions, thus providing complementary detection capabilities to consecutive messages.

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Abstract-We present, in this paper, ongoing work that investigates a new error detection policy aiming at enhancing communication integrity in the presence of permanent errors (single and multiple). We consider critical embedded systems which are based on complex networks including active interstage nodes. This property increases the occurrence probability of permanent errors. The novelty of the proposed policy lies in the fact that unlike classical policies using a single error detection function, it is based rather on a set of different error detection functions. The different used functions must be complementary in terms of detection capability in order to increase the resultant error detection capability. Our reference application to illustrate the proposed concepts is the Flight Control System (FCS). However, our objective is also to apply the proposed approach to other application domains sharing similar features and characteristics.

The evolution from mechanical to Fly-By-Wire (FBW) designs of Flight Control Systems (FCS, the system that controls the aircraft trajectory) in both airplanes and helicopters has been a crucial step offering a variety of benefits such as easing the pilot mission and reducing the mechanical complexity of the aircraft. Yet, all these advantages have limited improvement unless the required safety level is met. In fact, for such systems, a very high safety level is imposed by both the safety-critical property of the system and certification standards (e.g., ARP4754A and ARP4761 standard). Now, industrials such as Airbus Helicopters aim at installing fully digital FBW architectures on future helicopters. This step raises new challenges particularly to comply with certification standards requirements. We present, in this paper, the architecture of future fully digital Airbus Helicopters FCS considered at the end of feasibility study. We focus particularly on the communication integrity issue of future digital architectures. In such systems, the non-detection of corrupted messages could lead to catastrophic consequences. To enhance communication integrity, we propose an end-to-end communication integrity approach based on the black channel concept, it is to be implemented in the application layer. This approach uses error detection codes. Given the constraints of targeted systems namely "embedded" and "safety-critical" features, the selection strategy of error detection codes consists in a trade-off between the computational cost and the error detection capability.

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