Civil Engineering Reference
In-Depth Information
The following issues are documented for all systems:
• Safety study,
• Data integrity,
• Performance,
• Design assurance,
• EMC,
• System configuration management and
• Continued airworthiness.
For more information, contact the FAA or EASA. Another CRI is related to CAN
with the CRI-F09 for critical components; the CAN controller enters this category.
5.3.4
Example: Smoke Detectors Interfaced by a Safety-Critical
Aircraft-Based CAN-Bus Network
5.3.4.1
Abstract
Classic architectures of aircraft systems contain equipment using interfaces with
digital, analogue or discrete signals. The electrical network to interface the equip-
ment varies between the applications. Some equipment require a dedicated power
supply and provides information on an analogue current loop, while others use pro-
prietary digital busses or discrete input/outputs (I/Os) for information exchange.
Initially, CAN was developed for use in the automotive industry, but is nowadays
being used in an increasing number of applications. One of these areas is aviation,
where in the past 5 years CAN has grown from being an exotic newcomer to an
established and widely accepted solution. Within the Fire Protection System on
an Airbus, smoke detectors are installed in various areas overall in the pressurised
zones of the aircraft like lavatories, equipment bays and cargo compartments. As the
CAN bus defines only layers 1 and 2 of the Open Systems Interconnection (OSI)
communication model, additional higher layer features are necessary to achieve the
level of operational assurance required for a safety-critical application, namely fire
protection on an aircraft.
This example is particularly focused on the development of a safety-critical
CAN bus network with strict configuration control of smoke detectors in the scope
of an aircraft application. In 2003, international airworthiness authorities approved
the application in the frame of the Airbus A318 Type certification.
5.3.4.2
Introduction
The objective of the new smoke detection system was to replace the proprietary cur-
rent modulated supply and communication loop with an open, non-proprietary bus
standard. The overall system reliability and performance were aimed to match or
