ENGINE - Royal Australian Navy

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FIGURE 1- OMS SUB-SYSTEM BLOCK DIAGRAM
the avionics system. There are two
DGU units used in the Seahawk
helicopter. Each DGU hardware
component contains identical
software. The use of two DGUs
ensures that the DGU's database,
navigation state, and overall TDS
status is consistent such that either
DGU may assume bus control
should the other fail. Consequently,
any failure of both DGUs, including
degraded performance of the DGUs,
will not affect the operation of the
remaining equipment operating on
the Mll-STD-1553B bus.
FIGURE 2- DGU #2 IN THE S-70B-2
Engineering Support
The Original Equipment Manufacturer
(OEM), Rockwell Collins, provides a
limited level of engineering support
for the DGU through a Product
Support Agreement (PSA). All other
engineering activities are performed
by NASPO. RAN and contractor
personnel at the Avionics workshop
conduct all deeper maintenance. This
maintenance includes all test and
repair activities required to ensure
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the circuit cards, box and chassis are
serviceable.
Software Support
Software maintenance on the DGU
is conducted by NASPO, using a
combination of Commonwealth and
contracted support.
'The in-service maintenance and
development of safety-related
software for airborne and related
systems, if conducted without
sufficient rigour, has the potential
to impact the integrity of those
functions implemented by the
software, and therefore the safety
of the aircraft. Furthermore, the
recording, tracking and resolution
of problems associated with
safety-related systems is critical to
ensuring these systems achieve the
required level of safety. Only through
appropriate in-service management
will software achieve and maintain
its intended level of safety.'"
The NASPO Software Support Centre
(SSC). in accordance with the
NASPO Engineering Management
Plan and under NASPO's AEO
umbrella, has the following scope of
responsibilities:
1. Interface Manager for all TDS
integration activities;
2. In-service management of
problem reports (STERs) and
a point of contact for problem
resolution;
3. Development and maintenance
of plans and requirements for
software maintenance and
development;
4. Configuration management and
control of S-70B-2 Tactical Data
System and support system
software products;
5. Developmentand implementation
of software changes;
6. Test and Evaluation of software
products; and
7. Design review and approval of
software changes.
There is a consensus that the
development of software has
overtaken the development of
hardware as the major design effort
and the highest costs that arise in the
replacement of obsolete hardware.'
Software failures or potential
enhancements are reported
by operators and maintainers
at 816SQN, or are identified by
NASPO during defect investigations.
The NASPO SSC, in a Software
Trouble/ Enhancement Report
(STER), captures these failures or
potential enhancements, which are
categorised in terms of severity
and importance. If a STER is raised
that has safety implications or is
deemed so important that it must
be implemented immediately, then
a contingency build of software is
developed as a matter of urgency,
using a modified version of the SSC
Software Development process.
Each year, the non-critical open
STERs are reviewed and a number
are nominated for implementation in
a new build of software.
Since introduction into service,
the DGU has undergone several
changes in software version. The DGU
software was originally delivered with
Blue label (Bl) 107 software. There
have been several builds developed
in-house by the SSC including
Bl132, Bl144 (Fast Track FUR) and
Bl1 75 (DGU NOGO).
The SSC Test Rig is used for software
testing and qualification, and
consists of a combination of real
aircraft items and simulations to
DGTA 2008, AAP7001.054
Airworthiness Design Requirements
Manual, Section 2 Chapter 17
3 BAE Systems Australia Defence,
Nesterov. S, Simmonds. S 2008,
Evolution of Complex Safety-Critical
Avionics Systems in an NCW
Environment.