Tech Briefs Magazine - September 2021 - 22

TECHNOLOGY LEADERS Aviation/Aerospace
The Problem of Obsolete Avionics
A
ircraft that were designed in
the past century were expected
to have a service life of 20 to 30
years; however, many aircraft
are being flown longer or upgraded for
life extension.
One issue that fleet owners face for
their older aircraft is obsolescence of
avionics systems. This article presents
different strategies for addressing this
growing problem, including replacement
of obsolete line replaceable units
(LRUs) using commercial off-the-shelf
(COTS) products.
Using Custom COTS for Managing
Obsolescence
All aircraft are sold with an estimated
lifespan of service. Usually, it is anticipated
that under normal usage, you
would expect to get a number of years,
e.g., 20, out of the aircraft before it
needs replacing. An aircraft's various
onboard systems have supply and maintenance
contracts designed with this
lifespan in mind; however, many aircraft
end up in service for longer than originally
anticipated, which can create part
obsolescence issues. It gets harder to
find a way to replace or repair a part as
time goes on and aircraft can be
grounded if a necessary part fails and
there is no replacement.
Extending Aircraft System Life
During the design verification of a
new aircraft type, a design life is estimated
and assigned to all aircraft built to
the type design. Traditionally, an aircraft
is expected to be retired when the
design life is reached. In recent decades,
fleet operators have increasingly sought
ways of extending the useful life of older
aircraft to keep yielding economic benefit
from them before needing to purchase
a new fleet. Unfortunately, this
means fleet operators globally are now
faced with challenges associated with
aging aircraft. In fact, the UK Ministry of
Defence (MoD) classified 75% of their
fleets as " aging. " 1
Whether civilian or military, aging aircraft
often require a range of structural
and operational corrective actions
ensure continued airworthiness. A po -
to
22
Cov
Avionics
Metal fatigue
Hydraulics system leaks
Wing upgrades
Software
Engines
Center wing box
An aircraft may need several upgrades or part replacements in order to successfully fly beyond its original
design life.
Landing gear
Tape to Solid-State
Some systems undergo significant technological upgrades, like flight data recorders moving from magnetic tape to
solid-state recording.
tential point of weakness lies within the
avionics subsystems. These would have
been designed with maintenance support
contracts to meet the aircraft's
design life. Failure of one of these systems
may ground the aircraft by removing
a mission-critical function or by violating
(or not being on) the aircraft's
minimum equipment list (MEL). Many
of these systems can be difficult and
expensive to replace or repair and since
they are often very specific to the aircraft,
modern COTS replacements may
not be available.
Approaches to Managing Avionics
Subsystem Obsolescence
Although it is understood that it is difficult
to plan how long aircraft will
remain in service and to estimate the
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failure rate of systems, the ideal solution
to obsolescence is to have a sufficient
supply of spares to cover the needs of
the aircraft over its lifetime. This may
include monitoring the reliability of various
systems and taking advantage of any
" last-time buy " options. Proactive obsolescence
management programs are
invaluable but even the best ones can,
justifiably, not foresee extended aircraft
use or unseen component failures.
One solution will be to look to the original
equipment manufacturer (OEM) to
see if they are able to repair the affected
items under a new maintenance contract.
An OEM may be happy in principle to do
this but may be unable to if one or more
critical components are themselves obsolete.
Even if it
is possible, the cost to
redesign and requalify a unit using differTech
Briefs, September 2021

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Tech Briefs Magazine - September 2021

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