KAMILA KUSTROŃ, Ph.DDEPARTMENT OF AIRCRAFT

Room 309kkust@meil.pw.edu.pl

Duty hours: : 10.15– 11.45 Thirsdays

ANK 315 AIRCRAFT MAINTENANCELECTURES 4 , 5, 6

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DESIGN PHILOSOPHIES v. MAINTENANCE PHILOSOPHIES

RELIABILITY & MAINTENANCE CHARACTERIZATION OPTIMIZATION OF MAINTENANCE RELIABILITY OF SYSTEMS, FMEA/FMECA RCM, MSG3 AVIATION ORGANIZATIONS, AUTHORITY

REGULATIONS DEGRADATION PROCESSES, DAMAGES TEST 2, INTRODUCTION TO DIAGNOSTICS,

DIAGNOSTICS, NDT, NDE, SHM, EHM, HUMS AIR OPERATOR VISITING TEST 3, HUMAN FACTOR, FLIGHT SAFETY

DESIGN PHILOSOPHIES v. MAINTENANCE PHILOSOPHIES

RELIABILITY & MAINTENANCE CHARACTERIZATION OPTIMIZATION OF MAINTENANCE RELIABILITY OF SYSTEMS, FMEA/FMECA RCM, MSG3 AVIATION ORGANIZATIONS, AUTHORITY

REGULATIONS DEGRADATION PROCESSES, DAMAGES TEST 2, INTRODUCTION TO DIAGNOSTICS,

DIAGNOSTICS, NDT, NDE, SHM, EHM, HUMS AIR OPERATOR VISITING TEST 3, HUMAN FACTOR, FLIGHT SAFETY

NEXT LECTUREToday Lecture

Reliability can be defined as the ability of a system or component to perform its required functions under stated conditions for a specified period of time

In the aviation industry and even in general, operators want infinite performance, at zero life-cycle costs, with 100% availability from the day they take delivery to the day they dispose of it

One step to reach a high level of availability is to increase the reliability of the products, although this on its own can’t fulfill all those demands, but it is a link in the chain consisting of reliability, maintenance and logistics support, where maintenance comes as a natural part of reliability

RELIABILITY FUNCTION

Reliability Function, R(t), represents the probability of failure prior to some point in time, represented by t The Reliability Function is usually used when reliabilities are being calculated

Unreliability Function , F(t), is the probability that a failure will occur before time t and is called the Cumulative Distribution Function [CDF].F(t) = 1-R(t) F(t) is also referred to as the unreliability function and can be thought of representing the probability of failure prior to some time, t.

The Unreliability Function is usually used when probabilities of failure are being calculated

Failure_rate(t)= f(t)/R(t)

over a time interval (t2 − t1) from t1 (or t) to t2 and Δt is defined as (t2 − t1)

Note that this is a conditional probability, hence the R(t) in the denominator

Mean Time to Repair (MTTR)

Mean Time Between Failures (MTBF)

This is the combination of all technical and administrative actions, including supervision actions, intended to remain an item in, or restore it to, a state in which it can perform a required function.

Objectives of maintenance:- Reduce consequences of failure- Extend the life of the system, by keeping the system in proper condition for a longer time. In other words, to increase the “up” time of the system-Ensure that the system is fit and safe to use- Ensure that the condition of the system meets all regulatory requirement (airworthy)- Maintain the value of the system- Maintain the reliability and achieve a high level of safety- Maintain the systems availability and therefore minimize the life cycle cost- conditional maintenance (condition-based)

To maintain the performance of a system, the system MUST undergo maintenance

For maintenance to be carried out, the operator must know:- when and how often maintenance tasks should be performed- how they should be performed- how many people will be needed and what skills and how much training they will need- how long the system will be down- what facilities and equipments will be required- what is the cost of restoration

In the aviation industry, several of these questions are strictly regulated by the authorities

There are two main methods to measure maintainability:

- Mean Time to Repair (MTTR, Mean Time Between Failures (MTBF) – there are the expected values of items repair time

- Maintenance Man Hour (MMH) – this is an estimate of the expected total man hour needed to accomplish the maintenance

The MMH value can be larger the MTTR,MTBF due to the fact that it is often possible and sometimes even necessary to employ more than one person for a given activity or task

Classification of maintenance task

This is a set of activities which is performed with the intention of restoring the functionality or performance i.e. after failure. The duration of the corrective maintenance task DMTc, represents the elapsed time needed for the successful completion of the task. Corrective maintenance task is also referred to as unscheduled or unplanned maintenance task

Corrective maintenance task activities

CMTstart

Item failed DisassemblyFault location

Disassembly Test and Checks Assembly

Repair or Replacement

Verification

CMTcomplete

DMTc

This is a maintenance activity that is performed in order to reduce the probability of a failure of an item or system or to minimize the operational benefit. The duration of the preventive maintenance task DMTp ,represents the elapsed time needed for the successful completion of the task.

Preventive maintenance task activities

PMTstart Disassembly

Replacement

AssemblyTest and Checks

Verification

PMTcomplete

DMTp

This recognizes that a change in condition and/or performance is likely to precede a failure so the maintenance task should be based on the condition of the item. Thus through monitoring of some condition parameters it would be possible to identify the most suitable instant of time at which a preventive maintenance task should take place. The duration of the preventive maintenance task DMTm ,represents the elapsed time needed for the successful completion of the task.

Condition maintenance task activities

COTstart Inspection/

examination

Data collection

Condition assessment

Condition interpretation

Decision making

COTcomplete

DMTm

AIRCRAFT MAINTENANCE CHECKS ARE PERIODIC INSPECTIONS THAT HAVE TO BE DONE ON ALL COMMERCIAL/CIVIL AIRCRAFT AFTER A CERTAIN AMOUNT OF TIME OR USAGE - THE MILITARY AIRCRAFT NORMALLY FOLLOW SPECIFIC MAINTENANCE PROGRAMMES WHICH MAY BE OR NOT SIMILAR TO THE COMMERCIAL/CIVIL OPERATORS. AIRLINES AND OTHER COMMERCIAL OPERATORS OF LARGE OR TURBINE-POWERED AIRCRAFT FOLLOW A CONTINUOUS INSPECTION PROGRAM APPROVED BY EASA IN EUROPEAN UNION, FAA IN THE UNITED STATES, TRANSPORT CANADA OR BY OTHER AIRWORTHINESS AUTHORITIES EACH OPERATOR PREPARES A CONTINUOUS AIRWORTHINESS MAINTENANCE PROGRAM (CAMP), CONTINUOUS AIRWORTHINESS MAINTENANCE EXPOSITION (CAME) UNDER ITS OPERATIONS SPECIFICATIONS OR "OPSPECS"THE CAMP INCLUDES BOTH ROUTINE AND DETAILED INSPECTIONS. AIRLINES AND AIRWORTHINESS AUTHORITIES CASUALLY REFER TO THE DETAILED INSPECTIONS AS "CHECKS", COMMONLY ONE OF THE FOLLOWING: A CHECK, B CHECK, C CHECK, OR D CHECK

AIRCRAFT MAINTENANCE CHECKS

MAINTENANCE HANDLING

DESIGN PHILOSOPHIES v. MAINTENANCE PHILOSOPHIES

RELIABILITY & MAINTENANCE CHARACTERIZATION OPTIMIZATION OF MAINTENANCE RELIABILITY OF SYSTEMS, FMEA/FMECA RCM, MSG3 TEST 1, AVIATION ORGANIZATIONS, AUTHORITY

REGULATIONS DEGRADATION PROCESSES, DAMAGES TEST 2, INTRODUCTION TO DIAGNOSTICS,

DIAGNOSTICS, NDT, NDE, SHM, EHM, HUMS AIR OPERATOR VISITING TEST 3, HUMAN FACTOR, FLIGHT SAFETY

NEXT LECTUREPREVIOUS Lecture

DESIGN PHILOSOPHIES v. MAINTENANCE PHILOSOPHIES

RELIABILITY & MAINTENANCE CHARACTERIZATION OPTIMIZATION OF MAINTENANCE RELIABILITY OF SYSTEMS, FMEA/FMECA RCM, MSG3 AVIATION ORGANIZATIONS, AUTHORITY

REGULATIONS DEGRADATION PROCESSES, DAMAGES TEST 2, INTRODUCTION TO DIAGNOSTICS,

DIAGNOSTICS, NDT, NDE, SHM, EHM, HUMS AIR OPERATOR VISITING TEST 3, HUMAN FACTOR, FLIGHT SAFETY

NEXT LECTUREToday Lecture

Within the aviation industry, the operational requirements are high and because of the consequences of failure, the maintenance procedures govered by strict legislation under strict directive from regulation authority

These derectives are developed in a structured way of national requirements like international safety standards. The scheduled maintenance of an aircraft contains hundreds of timely/cyclic based inspections and replacements of parts

These can be divided into about 40, or more groups with different periodic intervals, which are developed from maintenance strategy like MSG3

Even if a system is maintained, deviations will occur, these deviations must be considered separately since they have a tendency to occur randomly at times and these are the unscheduled maintenance tasks

RELIABILITY CENTRED MAINTENANCE (RCM)

MAINTENANCE IS UNDERTAKEN IN A VARIETY OF FORMS, TO ENSURE THAT THE AIRCRAFT AND EQUIPMENT CONTINUES TO DO WHAT THE USERS WANT IT TO DO

RELIABILITY CENTRED MAINTENANCE DETERMINES WHAT MAINTENANCE NEEDS TO BE PERFORMED AND WHAT TESTING AND INSPECTION NEEDS TO BE PERFORMED TOSUPPORT THE MAINTENANCE STRATEGY

THE OUTCOMES OF AN RCM ANALYSIS CAN RESULT IN CHANGES TO EXISTING PREVENTIVE MAINTENANCE TASKS, THE USE OF CONDITION MONITORING, INSPECTIONS AND FUNCTIONAL TESTING, OR THE ADDITION OR ELIMINATION OF SUCH TASKS

RELIABILITY CENTERED MAINTENANCE

RELIABILITY ASSESSMENT

COMPARISON WHAT WE HAVE AND WHAT WE SHOULD HAVE

IF RELIABILITY CHARACTERISTICS ARE LOWER THAN WE NEED, WE MUST PREPARE IMPROVEMENT STRATEGY

HOW? WE MUST FIND THE ELEMENTS IN RELIABILITY STRUCTURE WHICH DECREASE RELIABILITY OF THE SYSTEM

NEXT APPLY SOLUTION TO IMPROVE RELIABILITY OF THESE ELEMENTS

EASY? … THAT....

DESIGN PHILOSOPHIES v. MAINTENANCE PHILOSOPHIES

RELIABILITY & MAINTENANCE CHARACTERIZATION

OPTIMIZATION OF MAINTENANCE

RELIABILITY OF SYSTEMS, FMEA/FMECA

RCM, MSG3

AVIATION ORGANIZATIONS, AUTHORITY REGULATIONS

DEGRADATION PROCESSES, DAMAGES

TEST 2, INTRODUCTION TO DIAGNOSTICS, DIAGNOSTICS, NDT, NDE, SHM, EHM, HUMS

AIR OPERATOR VISITING

TEST 3, HUMAN FACTOR, FLIGHT SAFETY

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