Development of Maintenance Programs

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Development of Maintenance Programs
Embry-Riddle Aeronautical University
Chapter 2
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THIS DAY IN AVIATION

• February 5
• 1914 Lt. J.C. Morrow became 24th and last flier
  to qualify as Military Aviator.

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THIS DAY IN AVIATION

• February 5
• 1919 The first regular, daily passenger service
  in the world is launched at Berlin's city
  airfield. A German airline operates the new
  service on route from Berlin to Weimar via
  Leipzig.

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THIS DAY IN AVIATION

• February 5
• 1929 Frank Hawks and Oscar Grubb land their
  Lockheed Air Express in New York after a record
  flight of 18 hours 20 minutes from Los Angeles.

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THIS DAY IN AVIATION

• February 5
• 1949 An Eastern Air Lines Lockheed
  Constellation lands at LaGuardia, New York, at
  the end of a flight of 6 hours 18 minutes from
  Los Angeles, a coast-to-coast record for
  transport aircraft.

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THIS DAY IN AVIATION

• February 5
• 1951 The United States and Canada announce the
  establishment of the Distant Early Warning (DEW),
  the air defense system that uses more than 30
  radar stations located across the northern
  portion of the continent.

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THIS DAY IN AVIATION

• February 5
• 1962 A Sikorsky HSS-2 Sea King of the United
  States Navy sets a world helicopter speed record
  of 210.6 mph, in the course of a flight between
  Milford and New Haven, Connecticut.

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Questions / Comments
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Development of Maintenance Programs
Embry-Riddle Aeronautical University
Chapter 2
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Before the Wright Flyer
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Development of Maintenance Programs

• Introduction
• Maintenance Steering Group (MSG) Approach
• Process-Oriented Maintenance
• Task-Oriented Maintenance
• Maintenance Program Documents
• Maintenance Intervals Defined
• Changing Basic Maintenance Intervals
• Summary

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Introduction

• Two basic approaches to Maintenance
• Process-oriented
• Task-oriented
• Difference between two
• is the attitude toward maintenance actions
• the manner in which actions are assigned to
  components and systems

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Introduction

• Process-oriented Approach
• Hard time (HT)
• On-condition (OC)
• Condition monitoring (CM)

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Introduction

• Process-oriented Approach
• HT and OC are for components or systems that have
  definite life limits or detectable wear out
  periods (Table 1.1 A, B, C) pg 10
• CM items are operated to failure and failure
  rates are tracked to aid in future prediction or
  failure rate prevention (Table 1.1 D, E, F)

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Introduction

• Task-oriented Approach
• Uses predetermined maintenance tasks to avoid
  in-service failures
• Redundancy and reliability programs utilized

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Maintenance Steering Group Approach (MSG)

• Began in 1968 (747) with reps from Boeings
  design and maintenance groups, from the
  suppliers, airlines who desired to purchase
  aircraft and the FAA.
• 6 working groups structures, mechanical
  systems, engine and auxiliary power plant (APU),
  electrical and avionics systems, flight controls
  and hydraulics, and zonal.
• Used bottom-up review to determine which
  process to use HT, OC or CM.

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Maintenance Steering Group Approach (MSG)

• MSG-2 used (pg. 17)
• Systems and components structures and engines
• Step 1 identify the maintenance or structure
  items requiring analysis
• Step 2 identify the functions and failure modes
  associated with the item and the effect of a
  failure
• Step 3 identify those tasks which may have
  potential effectiveness
• Step 4 assess the applicability of those tasks
  and select those deemed necessary
• Step 5 for structures only, evaluate initial
  sampling thresholds
• MSG-2 no longer used

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Process-Oriented Maintenance

• Hard Time (HT)
• is the removal of an item at a predetermined
  interval (hrs, cycles, calendar time)
• On-condition (OC)
• item will be checked at specific intervals (hrs,
  cycles, or calendar time)
• Condition Monitoring (CM)
• monitors failure rates, removal rates etc. to
  facilitate maintenance planning

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Hard Time (HT)

• Requires item be removed and either completely
  overhauled, partially overhauled (restored), or
  discarded before exceeding the specified interval
• (calendar time, engine change, cycles, flight
  hours, specified flights over water etc..)
• Items that can have an adverse effect on safety
  but no maintenance check for that condition
• Rubber seals, bushing etc..
• Structural inspection, landing gear overhaul, and
  life limited engine parts, mechanical actuators,
  hydraulic pumps and motors, electric motors and
  generators
• Can be OC as long as not safety related

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On-condition (OC)

• Requires item be periodically inspected or tested
  to determine if item can continue in service
  overhaul, restore or replace
• On-condition limited to continued airworthiness
  by measurements or tests without doing a
  tear-down inspection
• Examples tire tread and brake linings,
  scheduled borescope inspections of engines,
  engine oil analysis
• Other include Brake wear indicator pins
• Control cables (measure for diameter, tension,
  and broken strands)
• Linkages, control rods, pulleys etc (measure for
  wear, end or side play, or backlash

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Condition Monitoring (CM)

• Involves the monitoring of the failure rates,
  removals, etc. of individual components or
  systems that do not have a definite lifetime or
  noticeable wear out period
• CM components are operated until failure occurs
  unscheduled maintenance
• FAA states regarding CM
• Item has no direct, adverse effect on safety
• Must not have any hidden function (not evident
  to crew) that could effect safety
• Must be in condition monitoring or reliability
  program
• Avionics and electronic components
• Basic elements include data on unscheduled
  removals, maintenance log entries, on-board data
  systems, shop findings etc. can be used to
  adjust HT and OC intervals
• Only monitors failure not the condition of items

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Task-oriented (MSG-3)

• Top-down approach or consequence of failure
  safety driven
• Used to identify suitable scheduled maintenance
  tasks to prevent failures and maintain the
  inherent reliability of the system
• Three categories
• Airframe systems tasks
• Structural item tasks
• Zonal tasks

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Maintenance Tasks for Airframe Systems

• Lubrication
• Servicing
• Inspection
• Functional Check
• Operational Check
• Visual Check
• Restoration
• Discard

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Maintenance Tasks for Structural Items

• Environmental Deterioration
• Climate or environment may be time dependent
• Accidental Damage
• Result of human error or impact with an object
• Fatigue Damage
• Crack or cracks due to loading or stress

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Inspections for Deterioration of Structural Items

• General Visual Inspection
• Visual exam that will detect obvious conditions
  or discrepancies
• Detailed Inspection
• Use of inspection aids, (i.e. mirrors, hand
  lenses) may require surface cleaning and detailed
  access
• Special Detailed Inspection
• Use of Nondestructive inspection (NDI) dye
  penetrant, high-powered magnification, magnetic
  particle, eddy current

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Zonal Maintenance Tasks

• Ensures all systems, components, and
  installations within a specified zone receive
  adequate screening, security of installation and
  general condition
• Look, listen, and feel test
• General visual inspection
• Detailed visual inspection

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MSG-3

• Failure is assigned safety and economic whether
  it is an evident or hidden failure
• Fig. 2-2, Pg. 25 Level One analysis
• Fig 2-3, Pgs. 26, 27 Level Two analysis

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Maintenance Program Documents

• Maintenance Review Board Report (MRBR)
• Contains the initial scheduled maintenance
  program for US certificated operators
• Includes the systems and power plant maintenance
  program, the structural inspection program, and
  the zonal inspection program
• Also includes aircraft zone diagrams, a glossary,
  and list of abbreviations and acronyms

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Maintenance Program Documents

• Maintenance Planning Document (MPD)
• Contains all the maintenance task information
  from the MRBR report plus additional tasks by the
  airframe manufacturer
• Sorts tasks in various ways letter check, hrs,
  cycles and calendar time
• Includes diagrams showing locations and numbering
  of access doors and panels, aircraft dimensions,
  planning for maintenance checks to include
  man-hour requirements

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Monthly Maintenance Plan

• The Monthly Maintenance Plan is used to identify
  the projected maintenance work load such as
  inspections, receipts/transfers, technical
  directive compliance, etc.
• The Monthly Maintenance Plan provides requirement
  data for aircraft maintenance, SE material,
  manpower and training.
• The Monthly Maintenance Plan is under the
  cognizance of the MO.

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Monthly Maintenance Plan
1. Projected known operational
commitments, including number of flights, flight
hours, and utilization goals.
2. Dates of scheduled inspections.
3. Date of receipt or transfer of
aircraft.
4. Precision Measuring Equipment (PME)
calibration requirements.
5. Schedule of technical training.
6. Forced removal items.
7. Technical Directive Compliance (TDC)
requirements.
8. Schedule of personnel for ejection
seat safety check out
9. Schedule of pre-inspection meetings.
10. Current list of QA personnel
11. Dates of scheduled SE inspections.
12. Scheduled nondestructive inspection
(NDI) requirements
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Maintenance Intervals

• Most intervals are standard but airlines can
  create own intervals as long as the integrity of
  the original task is maintained or receive FAA
  approval
• Transit Check pre-flight and turn
• Visual, open/loose panels, fluid leaks
• 48 hour Checks daily
• Wheels, brakes, fluid levels, hydraulic fluid
• Hourly limit Checks (100, 200, 250 etc.)
• Engines, flight control systems

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Maintenance Intervals

• Operating cycle limit Checks
• Tires, brakes, landing gear, airframe structures
• Letter Checks (A, B, C, and D)
• Development of 777, MSG-3 eliminated checks
• Changing Intervals
• Hot, humid climates more CC
• Dry, desert climates check for sand and dust
• As aircraft age intervals for some items may
  shorten while others may lengthen

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Summary

• Process-oriented and Task-oriented approaches
• HT, OC and CM vs. scheduled, redundancy, and
  reliability
• MSG, MSG-2, and MSG-3
• Structures, mechanical systems, engine and APU,
  electrical and avionics, flight controls and
  hydraulics, zonal
• Systems and components structures and engines
• Straightforward logic approach How does failure
  effect operation?
• Maintenance Documents (MRBR and MPD)
• Maintenance Intervals
• Transit, 48 hr, hourly, cycles, Ltr Checks
• Changing Intervals

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Questions?