Cirrus' "Failing Instruments In Rapid Succession"

On 16 Apr 2004 07:08:26 -0700, (Michael) wrote:

Fix it or get rid of it.

I got rid of it.

"Mike Rapoport" wrote
While I generally agree with your statements about old instruments,
presumably the instruments in a Cirrus SR22 are not very old.

There's a difference between a new instrument, and an instrument that
was recently manufactured to an obsolete design. I've spent years
designing instruments (not for aviation - no money there) and learned
something interesting. No design is static - it either evolves or
rots.

When an instrument is first designed, there are inevitable growing
pains in manufacturing. This is expected, and it's fairly typical for
a design engineer to spend a fair amount of time in manufacturing to
bring the production people up to speed. But that's not the end.

In a normal environment, there are continuous changes. Upgrades are
made. Production processes are streamlined. Lower cost vendors are
found, and engineering asessments/changes are made to accomodate the
lower cost parts. Subassemblies are outsourced, and invariably the
outsourcing process turns up problems in the documentation. But even
if you don't plan any changes, they happen anyway. Vendors change
their products subtly, or discontinue them completely, or just go out
of business. Design and production changes are made to accomodate
this.

Eventually the design ages to the point where too many parts are
unavailable, better methods exists, and it's time to redesign from
scratch. That's a normal product life cycle.

In GA, the process is perverted. Any change triggers a paperwork
avalanche, so changes are avoided at all costs. Engineering
involvement with a product post-release is dramatically reduced. Life
cycles are very long. As a result, when an unplanned change occurs,
the product often gets worse. This is a well-documented phenomenon in
aviation engines (when was the last time a large Continental jug made
TBO?) but it's even more true for smaller products.

This was a steam gauge Cirrus. The gauges in it were more than likely
of relatively recent manufacture - and obsolete design.

Michael