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【范围】
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The original purpose of this document was to establish interface requirements for modular avionics
backplanes to be prototyped up to 1995. The document was issued as ARD50011 in September
1992. It is being reissued as an SAE Aerospace Information Report (AIR) in order to:
a. Preserve the requirements for more than 2 years
b. Support design of retrofits and avionics systems to be fielded in the years 1995 to 2000
c. Provide a baseline for updating the requirements of future integrated systems
These requirements were and are intended to promote standardization of modular avionic
backplane interfaces. These requirements have been driven predominantly, but not exclusively, by
aerospace type military platforms.
1.1 Purpose:
Several studies (2.2.1, 2.2.2, and 2.2.3) have shown that a significant reduction in the life-cycle-
cost (LCC) of complex systems can be obtained through the use of form, fit, and function (F
3
)
interface standards. Perhaps the most recent implementation and application of the F
3
concepts
have been the development of common avionics modules for military aircraft programs.
Significant effort has been expended to develop a family of line replaceable modules (LRM) which
in many cases supplant the use of traditional line replaceable units (LRU). The applications for
use of avionics LRMs include new platforms as well as product improvement, retrofit, and
upgrade programs. Depending on particular programmatic requirements, the following benefits
may be realized when using common avionics LRMs:
a. Reduction in the size of line replaceable items
b. Reduction in the number of types of line replaceable items
c. Reduced Avionics Intermediate Shop (AIS) complexity through a two-level maintenance
structure with less AIS repair
d. Use of common building blocks to provide functions
e. Increased fault detection and tolerance with module level fault isolation
f. Support for reconfiguration.
The key to the application of the modular design approach for avionics lies in the standardization
of backplane interfaces with integrated rack and packaging guidelines.
Currently, standards exist for some interfaces. Examples are the Pi (see AS4710) and TM (see
AS4765) buses, but others may apply. There is a growing awareness that further definition of
backplane interfaces is required. No overall view of backplane functions and requirements is
available within the open literature. This document is intended to provide that overall view and
avoid a fragmented approach to modular avionic backplane interface standardization.
The AS-2 Committee fosters the systematic approach of requirements definition before standard
adoption or development. The baseline for this document was the Modular Avionics System
Architecture (MASA) program document, “Requirements/Standards for a Modular Backplane”
(2.2.4) which was developed by the MASA Interface Panel.
1.1.1 Document Objectives: This document was developed with two main objectives:
a. Define what modular avionics backplane services, interfaces, and physical attributes should
be standardized or specified
b. List task group consensus attributes on which further backplane interface standardization
and specification can be based.
The first objective is covered by Sections 3 and 6 while the second objective is covered by
Sections 4 and 5. Thus, the only requirements included are those for which consensus could
be realized within the group.
1.1.2 Document Structure: A definition of each identified backplane function is given in Section 3,
listing the services which may be required by a modular avionics backplane. Requirements
which may be applied generally to all backplane services are given in Section 4 while Section 5
describes requirements unique to a particular backplane service. Section 6 defines the types of
documentation which are required to implement a backplane system which supports common
avionics interoperability.
1.1.3 Scope of Detailed Service Requirements: This document brings together the definition of all
the services required to be supported by the modular avionics backplane. Some requirements
need to defined in greater detail before standards can be developed. However, these detailed
requirements must be developed for use within the environment and constraints indicated within
this document.
NOTE: The specific requirements defined by the group are considered important even though
only an initial look at the problems. A more detailed investigation of the requirements
could produce other results. The more detailed results should be adhered to, since
the ones in this document are just an initial evaluation of the services.
It should be noted that these are functional requirements and more than one backplane service
may be implemented by a single standard (e.g., Data Flow and Sensor/Video Networks). The
BIRST group advocates consideration of requirements for similar networks during the
development of a standard to minimize the number of standards generated.strRefField
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