Aviation Maintenance Management Why We Have to Do Maintenance Chapter 1

THIS DAY IN AVIATION January 28 1871 — The last balloon to leave Paris during the Persian siege takes off with orders for the French fleet to bring food and supplies to replenish the French capital, an armistice having been signed. The flight of the General “Cambronne” ends a period of almost exactly 5 months during which the advantages of balloons were put to efficient use.

THIS DAY IN AVIATION January 28 1945 — The Burma Road is reopened.

THIS DAY IN AVIATION January 28 1945 — The USAAF 8th AF observed its 3rd birthday with a 1,000 plane raid on Germany.

Aviation Maintenance Management Introduction Design & The Role of the Engineer Role of the Mechanic Types of Maintenance Reliability & Redesign Failure Rate Patterns Other Maintenance Considerations Summary

Introduction Schedule pressures, parts shortages, equipment deficiencies, regulatory and agency compliance inspections, union pressures etc.. Technology advancements and diverse equip require perpetual training Parts issues – no parts, cannibalization, aircraft on ground, weather conditions Personnel issues – financial, family, substance abuse, late, no-show, vacations, trng, meetings – impact (touch labor) Unscheduled Maintenance

Managerial Challenges Aircraft out of service impacts – crew training and readiness Lost of revenue (no passengers – and maint/labor costs) Loss of customer loyalty (customer is price based) Intent of course not to make you an expert maintenance manager but to expose you to the various influences and the functions and techniques of the job Knowledge is power

Modern Day Aircraft Maintenance Aircraft require preventive or corrective maintenance at frequent intervals Kind of operation; environmental conditions; storage facilities avail; age and construct of aircraft Maintenance Man-hours per Flying hour (MMH/FH) Cost to maintain a particular type of aircraft

Modern Day Aircraft Maintenance Cost of ownership – fuel, wash, oil, tires etc… Scheduled maintenance Goal is to correct any deficiency before it occurs Checks cost money – labor and parts, fluids costs and loss of passenger revenue when not flying Total up all Maintenance associated costs subtract from revenue from aircraft and you get profit or loss

Design & Role of Engineer We can design perfect systems on paper but we can not build perfect systems in the “real” world Nothing is perfect Good, Fast, Cheap A design engineer may be limited from making the perfect system by technology or the state of the art within any facet of the design effort Limited by ability, technique or economics Economics may force a redesign with reduced tolerances, cheaper materials and gap between: perfect and “perfect” realism

Role of the Mechanic For the mechanic the gap between “perfect” & “perfect” realism always changes & predominantly for the worse Components or systems tend to wear out from use or lack there of (time or environmentally related) Misuse may cause premature deterioration or degradation of the system or even outright damage The engineer’s responsibility is to design the system with as high degree of perfection within reasonable limits/constraints The mechanic’s responsibility is to combat the gap between ideal & realism during the operational lifetime of the equipment

Two Types of Maintenance Preventive Maintenance (PMs) Performed at regular intervals – to prevent deterioration of the system to an unusable level and to keep it operational – often referred to as: Scheduled Maintenance Performed – daily, every flight, every 200 flight hours, or every 100 cycles (takeoff & landings) Unscheduled Maintenance Various, unpredictable intervals maintenance actions are required to restore a system that may require extensive testing, troubleshooting, adjusting, replacement, restoration, or complete overhaul of parts or subsystems

Maintenance Defined Cost of Ownership and scheduled maintenance are 2/3 of equation Unscheduled Maintenance – random failures Reliability studies have led to MTBF (Mean Time Between Failure) – components / system guesstimated reliability factor Induced failures – FOD, damage from servicing vehicles, maintenance malpractices Inherent failures – delamination of composites, substandard bearings, inefficient seals etc. No defect – A-799 or fault within tech data limits (require expenditure of maintenance resources)

Reliability & Redesign “A measure of the probability that an item will survive to a specified operating age or time, under specified operating conditions, without a failure” no amount of maintenance can be performed to increase the systems inherent level of designed in-level of perfection Redesign When the reliability decreases & a higher level of “perfection” is desired – redesign may take place Needs to be weighed if the performance improvement justifies more maintenance & thus the increase in maintenance costs – ideally the opposite is true

Failure Rate Patterns (MTBF) All systems or components fail at the same rate or exhibit the same patterns of wear out and failure The maintenance performed is related to those rates and failure patterns (Table 1-1 pg. 10) “Infant mortality” – early high failure rate in component’s life “getting the bugs out” Causes” poor design, improper parts, incorrect usage etc.. These characteristics of failure make it necessary to approach maintenance in a systematic manner to reduce peak periods of unscheduled maintenance Several techniques have been designed to combat this:

Three Maintenance Management Techniques Equipment redundancy, line replaceable units, & minimum aircraft dispatch requirements Equipment Redundancy Duplicate systems – primary and a backup (radios, navigation devices, flight control systems, computers) Instrumentation within cockpit can signify status Line Replaceable Units (LRUs) – black boxes Designed to allow easy removal and replacement to reduce out of service timer of aircraft

Three Maintenance Management Techniques Master Minimum Equipment List (MMEL) Lists ALL equipment for the aircraft model – list is tailored to its MEL Minimum Equipment List (MEL) List of equipment that the aircraft may be inoperative but still allowed to fly as long as it does not affect the safety & operation of flight – Tailored to mission Determined by manufacturer and sanctioned by the regulatory authority (FAA)

Three Maintenance Management Techniques Minimum Equipment List (MEL) Concept of the MEL is to allow the deferral of maintenance without upsetting mission requirements Maintenance must be performed within some set of guidelines (1, 3, 10, or 30 days or cycles required) depending on operational requirements of the system Pilot may always require or defer maintenance per the MEL Maintenance MUST abide by decision…. (his call) “Takes a college education to break it & a high school education to fix it.”

Minimum Equipment List (MEL) Dispatch Deviation Guide (DDG) Instructions for maintenance not necessary obvious to the mechanic – tying up cables, capping off connectors, taking circuit breakers out to prevent inadvertent power-up of equipment during flight while maintenance is being performed and any other precautionary steps that need to be taken Configuration Deviation List (CDL) List of information of equipment or panels etc. that may be missing or added per that aircraft model All lists can be found in the aircraft logbook 3 techniques help minimize the workload and reduce service interruptions due to maintenance

Summary The purpose of aircraft maintenance is to ensure the aircraft will remain airworthy throughout its operational life Still haven’t reached perfection even with advances in technology 3 maintenance techniques help manage maintenance actions Not all aircraft maintenance activities will be organized or operated in the same manner but the programs and activities will be the same