Eurofighter Typhoon – Staying Ahead

Agile and stealthy, the twin-engine Eurofighter
Typhoon is the world’s most advanced multirole
combat aircraft, capable of operating from
hastily prepared bases and small runways
around the globe.
The aircraft’s ability to deliver air dominance
beyond visual range and in close combat - and
high sortie rates in all weathers - is made
possible by the unprecedented use of
integrated flight control and avionics systems
supporting the pilot.

Staying Ahead
To deliver unrivalled agility, power and multi-role
capabilities – is at the heart of the designers’ vision. But
such is the unremitting pace of change in the world of
commercial silicon that, still within its development
phase, the Eurofighter program faced a major challenge.
There was the need to insert a new generation of
technology into one of the aircraft’s key sub-systems – the
Defensive Aids Sub-System (DASS) – that provides stateof-
the-art, all round prioritized assessment and fully
automated responses to single or multiple threats.
To help it meet that challenge BAE Systems, the prime
contractor for the DASS, turned to Radstone Technology.
Its response has been to develop a customized formfactor
version of its PowerPC4A rugged single-board
computer, combining cutting-edge design and production
technologies with over 40 years of experience serving the
defense industry. Five Radstone boards now lie at the
heart of each Eurofighter DASS.
“Radstone understood our requirements very well,”
explains Richard Edwards, the Engineering Project
Manager for the DASS at BAE Systems. “They listened to
us and didn’t respond by asking us to make changes to
our existing system; they worked with us to meet our
exact requirements. Their people have a deep
understanding of how to utilize commercial components
in demanding environments and working with them we
have been able to integrate leading-edge silicon into the
program within a very demanding timescale.”

World-Leading Performance and Value
It is not just performance that sets the Eurofighter
Typhoon apart from its rivals. From the start of the
program, a strong emphasis has been placed on reducing
cost of ownership in addition to delivering outstanding
performance and flight safety.

With the increased focus on smart procurement has come
renewed interest in how to best take advantage of the
economic and performance advantages of COTS
(Commercial Off the Shelf) technology without
compromising long-term system integrity.
For the DASS design team at BAE Systems in Stanmore,
England, finding the answer to that question became very
real as – with the system entering the final stages of its
development phase – they decided to replace the original
General Purpose Processor, based on Motorola 68020
technology, with a PowerPC-based solution.
“The original specification was written about a
decade before,” recalls Edwards. “Technology
had moved forward greatly since then, so in
1999 we decided to look towards inserting a
new generation of silicon that promised better
performance and a clearer path for future
growth. Our design brief was clear, but
demanding. We wanted to drop PowerPC boards
into the current processor space and realize the
benefits of increased performance from day one.
Furthermore, because the new boards were going into an
existing system, things like power, weight, interfaces and
form-factor were not open for debate.”

With flight trials due to start in 2002, speed was of the
essence. The initial development contract, won by
Radstone following a stringent international tender, called
for extremely aggressive timescales. Radstone delivered
the first board to BAE Systems in just six months – on
Christmas Eve 1999 – having completed several
significant developments including:
• sourcing and designing-in new components to meet
low power consumption specifications
• reducing the size of its commercial 6U
processor boards by two-thirds to meet
BAE Systems’ exacting formfactor
requirements, enhanced
functionality and the resulting high
component density
• mechanical engineering to ensure that the boards are
able to withstand high levels of vibration
• reducing application software development time by
migrating elements of BAE Systems’ existing periphery
software architecture on to a variant of Radstone’s
standard Board Support Package thereby providing a
software emulation layer.
Stringent Power Requirements
The need to work within the DASS power envelope
posed an immediate question for Radstone engineers
because only 11 Watt were available as opposed to the
17.5 Watt typically drawn from Radstone’s commercial
boards.
Techniques to reduce power consumption such as
removing Level 2 cache were not an option, so Radstone
decided to source alternative components, balancing
slightly less performance against much-reduced power
requirements. The Tundra Universe VME controller was
replaced by an IBM Alma controller, while the Motorola
PMC 106 Northbridge was switched with the Galileo
Terrano. Despite this, the new Radstone design offered
BAE Systems a ten-fold increase in processor
performance.
Reduced Form Factor – With Increased
Functionality
One of Radstone’s first tasks was to develop a board that
matched the original 7 x 4 inch form factor – and the pinouts
– of the original design instead of the industry
standard 9 x 6 inches. BAE Systems also required
additional functionality over Radstone’s standard
PowerPC4A.





“We had a lot of development work and software
invested in the DASS’ legacy SDLC (Serial DataLink
Controller) interface,” explains Edwards. “It was based
on the 85230 Zylog interface chip, and we were keen to
be able to port as much of our software as possible to the
new chipset.”
Radstone’s solution was to dedicate an engineer for six
months to design and blow a new Field Programmable
Gate Array (FPGA) that integrated the DASS’
communications circuits to the Northbridge, including
some additional functionality requested by BAE Systems.
Recognizing the importance of this part of the design,
Radstone produced a trial board with the core FPGA
mounted on a PMC module which sat on a standard
processor card, so that BAE Systems could continue with
software authoring in parallel with the development of
the main processor design. More functionality was added
later.
Richard Campbell, BAE Systems’ Senior Software Engineer
on the Eurofighter program, explains the significance of
the module: “Both we and Radstone recognized that this
was one of the critical areas of the development. The
module was a very good way of de-risking that part of the
design, enabling us to work on the SDLC algorithms and
porting software to VxWorks before we received the main
card. Our ability to start testing was very significant
because the SDLC code is very timing dependant and the
use of faster processors required very thorough testing.”

Radstone recognized from the start of the program that
the reduced form-factor and increased functionality also
inevitably led to the need for very high component
density on the board. One facet of the solution was the
decision to use then innovative sequential build
technology, which enabled placement of BGA
components on both sides of the board irrespective of
position. Radstone pushed its PCB (Printed Circuit Board)
manufacturing partners to the limit with it’s mechanical
and electronic design engineers (equipped with state-ofthe-
art CAD (Computer Aided Design) tools such as
Mentor Expedition PCB Design and Signal Integrity
Analysis) designing complex networks of micro-vias with
completely different patterns on each side of the board.

Withstanding an Extremely Hostile
Environment
Radstone designs rugged systems; it does not ruggedize
commercial systems for a hostile environment. Its
solutions can be found in the nose cones of torpedoes
and orbiting the earth in the NASA International Space
Station. Even so, with the Eurofighter DASS the company
faced one of its most hostile environments yet.
“The environmental requirements set by the Eurofighter
program were unusually severe – we have seen nothing
quite like it before or since,” admits Edwards. The reason
is simple – the cards ‘live’ in the avionics bay of the
Eurofighter, close to its guns and the vibration those guns
create.
Hostile environments are, however, well understood by
Radstone and are countered using a range of techniques.
The original DASS PCBs used a specialist manufacturing
technique for which there was a price premium. In contrast, Radstone’s commercial rugged PCBs are built to
the company’s design, with two thick copper cores, in
addition to the signal layers, that act as both mechanical
stiffeners and an integral part of the heat management
system. Radstone’s commercial board not only proved up
to the environment, it also resulted in reduced board
costs. One challenge facing Radstone, however, was that
the physical space limitations of the DASS enclosure
meant the company was not able to utilize its normal
technique of using a stiffening bar to reduce vibrationinduced
flex across the PCB. Besides which, BAE
Systems need access to a high-speed bus on one side of
the card used for software testing.
It’s said that necessity is the mother of invention, but the
elegance of Radstone’s solution belies its fresh thinking –
a stiffening bar was actually soldered onto one side of the
card, leaving free access to the high-speed bus on the
other side.
Edwards also remembers being impressed by Radstone’s
approach to component placement and thermal
management – both key to ensuring ruggedness.
A detailed component placement review by Radstone
early in the design process, identified where best to sit
components on the board in order to best match their
characteristics to the stress across a PCB while keeping
electrical connections as short as possible.