Transcript AIRCRAFT RELIABILITY

AIR TRANSPORTAION AND AIRCRAFT MAINTENANCE (AE1012)
AIRCRAFT RELIABILITY
Y.K.Sinha
Rajalakshmi Engineering College
Topics to be covered
• Aircraft reliability
• The maintenance schedule & its
determinations
• Condition monitoring maintenance
• Extended range operations (EROPS) &
ETOPS
• Ageing aircraft maintenance production
What is reliability ?
• Reliability is a broad term that focuses on the
ability of a part, assembly or system to perform its
intended function
• Mathematically speaking, assuming that the part,
assembly or system is performing its intended
function at time equals zero (T0), reliability can be
defined as the probability that an item will
continue to perform its intended function without
failure for a specified period of time (T0 + TS)
under stated conditions.
RELIABLE
T0
TS
TS
T0
UNRELIABLE
Definition of Reliability
Reliability is the probability that a part,
assembly, or system will perform its
intended function in a stated condition or
environment for a predetermined length of
time without failure.
What is Reliability ?
Reliability is performance over time.
Why is reliability needed ?
It is the key design parameter over the
aircraft life cycle that shows effectiveness,
affordability
and
operator’s
satisfaction.
How is the airplane reliability established ?
By continuous recording, analysis and
monitoring data pertaining to operation of
aircraft systems, sub-systems and
components.
Equipment failure
Most equipment failures have no
relationship to length of time in-service.
Most failures are unpredictable. But if you
detect a future failure early, you can
handle it most cost effectively before it
becomes a breakdown
Equipment degradation
Condition Monitoring
Reliability Programme
A Reliability Programme is an event reporting
system based on performance values
experienced under actual conditions. It provides
a means of measuring the performance of
aircraft systems and components and comparing
the performance to predetermined levels of
acceptable performance. An event reporting
system and data analysis permits the rapid
identification of adverse trends. If the systems
and components do not meet established levels,
an alert is issued and an investigation is initiated
to assess the problem and initiate a programme
of corrective actions.
COLLECTION
• Pilot Reports
• Delays & Cancellations
• Component Removals
• Inspection Findings
• Shop Findings
• Power Plant Data
• Structural Data Flight Statistics
• OMT / QAR Data
DATA DISPLAY,REPORTS
ANDANALYSIS
• Statistical Reports
• Trend Monitoring
• Fleet Campaign
• Validation Study
• Historical Data
CORRECTIVE ACTION AND
ANALYSIS
• Modify Maintenance Process
• Modify Maintenance Tasks
• Service Bulletin Modifications
• Correct Maintenance Procedures
• Modify/Correct Shop Procedures
• Escalate/Reduce Intervals
•
Adjust Inventory Levels
Reliability Programme Advantages
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Improved management of airworthiness
Effectiveness of maintenance programmes
Provides visibility for cost control
Optimizes management of fleet performance
Timely database sustains the fleet vital statistics
Supports technical efficiency of the Operations
Control Center
• It provides the tools for reliability analysis of
aircraft structures.
Reliability Programme Disadvantages
• Lack of data discipline provides mis-information
• The larger the fleet operation the larger the
computing resources required
• Data must be consistent and accurate to be
meaningful.
Reliability theory
• Reliability is the probability that a device
continues to perform a particular function over
a particular period of time and under stated
conditions.
• Let R denote the reliability of a component, and
let F be the rate of failure, then
R+F=1
• R dependent on the failure-free operation.
Reliability (ctd)
• In reliability theory it is customary to assume a
constant failure rate. Then we typically express
reliability R, the probability of survival to time t,
in the form:
R = e-t = e -t/T
where T = mean time between failures, or
mean time to failure whichever is
most appropriate in the circumstances.
Reliability formulae
• Consider the situation where a system is
composed of several subsystems whose
reliability is known, the terms being compatible.
• There may be parallelism, interconnections of
various kinds, etc.
• Two common methods of interconnection are
important - in series and in parallel.
Connection in series
• Let R1, R2, R3, ..., Rn denote the reliability of
components, and F1, F2, F3, ..., Fn denote the
corresponding failure rates.
• Then the system operates only if all the
components themselves operate.
• The overall reliability of the system is R where
R = R1 x R2 x R3 x ... x Rn
Connection in parallel
• In this case the system operates if at least
one of the components operates.
• The relevant formula is then:
F = F1 x F2 x F3 x ... x Fn or
(1 - R) = (1 - R1) x (1 - R2) x (1 - R3) x ... x
(1 - Rn)
Combination