Useful Life & Inspections
Cirrus airplanes require only routine
maintenance to the extent of their published
useful life. An alternative is to develop major
(or “heavy”) inspections at certain intervals to
check the structure and replace suspect
components.
At Cirrus we chose to test for a useful life of
12,000 flight hours – about 60 years of average
use. Most of our major structures, however, have
been tested for twice this lifetime. At Cirrus
we also chose to demonstrate that the structure
is good for this design life without the need
for any interim, heavy inspections – with their
associated cost and inconvenience.
At Cirrus we expect that, as real-life aircraft
approach 12,000 hours, a further round of
testing, analysis, and inspections will
determine how to extend the useful life.
Other manufacturers use different combinations
of life and inspections. For example:
-
Cessna (formerly
Columbia) 350/400 have a lifetime of over
25,000 hours but with an extensive (bonded
seams, checks for de-lamination, thirty wing
bolt replacement, flight control removals,
etc.) airframe inspection every 3,000 hours.
These aircraft are certified for utility
category (0.6G additional structural
substantiation over the normal 3.8G) but are
significantly compromised: landing weight
reduced 180 lbs from maximum takeoff weight;
Vne (Never Exceed Speed) reduces with
altitude to under 175 knots (KIAS); and
advertised speed at 25,000 feet is about 20
knots above the corresponding Vno (maximum
structural cruising speed).
-
Diamond DA-40 training airplanes have no
published useful life. Those airplanes are,
somewhat similar to older designs, dependent
upon regular “heavy” inspections to identify
structural issues arising from routine use.
These airplanes have an extensive
“wings-off” inspection every 1,000 hours and
even more intrusive structural inspection
every 2,000 hours.
All of these approaches
produce sound, strong airplanes – probably the
best general aviation airplanes ever produced.
Different engineering approaches, though,
produce different trade-offs. At Cirrus we
prefer the simple, uncomplicated approach –
which we believe offers the highest level of
convenience and economy for our customers.
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