ET-PP04 Aircraft Engine Inspection, Maintenance, Operation, and Troubleshooting PDF

ETHIOPIAN AVIATION ACADEMY Aviation Maintenance Training ET-PP04 Aircraft Engine Inspection, Maintenance, Operation and Troubleshooting First Edition March 2020 Table of Contents Power plant Ins...

ETHIOPIAN AVIATION ACADEMY Aviation Maintenance Training ET-PP04 Aircraft Engine Inspection, Maintenance, Operation and Troubleshooting First Edition March 2020 Table of Contents Power plant Inspection.............................................................1 Power plant Documents........................................................................ 1 Manufacturers overhaul manual....................................................... 5 Table of Limits............................................................................... 5 Manufacturer’s Bulletins.................................................................. 5 Airworthiness Directives................................................................. 9 Specification............................................................................... 10 Type Certificate Data Sheets......................................................... 11 Forms and Records...................................................................... 13 Inspection......................................................................................... 15 Engine Inspection Fundamentals.................................................... 16 Methods of Inspection.................................................................. 19 Turbine engine inspection............................................................. 43 Engine removal and replacement (level 3)................................ 60 Fundamentals.................................................................................... 60 Reason for turbine engines removal............................................... 60 Safety precautions during engine removal and Installation................ 62 Tools for engine removal and installation........................................ 63 General Procedures for Engine Installation............................................ 64 Preparation of Engines for Installation............................................ 64 Inspection and Replacement of Powerplant External Units and Systems66 Hoisting and mounting the Engine for installation............................ 68 Preparation of Engine for Ground and Flight Testing......................... 68 Propeller Check........................................................................... 69 Checks and Adjustments after Engine Run-up and Operation............. 70 General procedures for engine removal................................................. 70 Preparing the Engine for Removal.................................................. 70 Removing the Engine................................................................... 73 Turbine Engine Power plant Removal and Installation............................. 74 Removal and Replacement of an Auxiliary Power Unit (APU).............. 75 Removal and Installation of Turbofan Engines................................. 78 Turboprop Powerplant Removal and Installation.............................. 81 Engine Cowling removal and Installation......................................... 82  Engine Components Removal/Installation....................................... 86 Gas turbine engine Maintenance and Troubleshooting................ 87 Turbine engine Maintenance................................................................ 87 Engine Accessory replacement....................................................... 88 Compressor section maintenance................................................... 90 Combustion section maintenance..................................................101 Combustion Chamber Borescope inspection...................................103 Troubleshooting Turbine engine..........................................................106 Types of fault Indicators..............................................................107 Rules for Systematic Troubleshooting............................................107 Turbine Engine Troubleshooting Procedures...................................108 Turbine Engine Calibration and Testing..........................................109 Troubleshooting EGT System........................................................110 Troubleshooting Aircraft Tachometer System..................................111 Probable cause and remedy of the following turbine engine troubles/malfunctions..................................................................112 Engine Ground Operation & Performance (level 3)................... 115 Gas Turbine Engine Operation............................................................115 Pre-Run-up check.......................................................................115 Engine Starting Procedure............................................................116 Precaution after engine light up....................................................117 Procedure after engine start.........................................................119 Parameter checks.......................................................................119 Checking Takeoff Thrust..............................................................120 Engine Shut Down Procedure.......................................................120 Post run up checks......................................................................121 Engine rigging & Adjustment..............................................................122 Desirable Characteristics..............................................................122 Rigging and Operational Check.....................................................124 Engine trimming.........................................................................125 Preservation and Storage of Engines...................................................128 Reason for preserving an Engine...................................................128 Gas Turbine Engine preservation..................................................129 De-preservation procedure...........................................................137  Ethiopian Aviation Academy Aviation Maintenance Revision No. 0 Training March 2020 ET-PP04 M01: Aircraft Engine Inspection, Maintenance, Operation and Troubleshooting Power plant Inspection Power plant Documents Power plant and propeller manufacturers provide a variety of documents and service publications for inspection, maintenance, and repair. Although the FAA reviews and approves only a limited amount of manufacturer's information, generally speaking, the manufacturers' information is considered to be acceptable data for inspection and maintenance. If manufacturer information is unavailable, use the standard inspection and maintenance criteria specified by the FAA. Manufacturers’ publications includes Maintenance manual (aircraft/engine) Engine overhaul manual Component Maintenance Manuals (CMM) Power plant Build up Manual(PBM) Illustrated parts catalog (IPC) Service Bulletins (SB) Standard Practice Manual (STM) Fault Isolation Manual (FIM) Wiring Diagram Manual (WDM) Temporary Revision Information material Miscellaneous The FAA publishes a variety of documents; some provide mandatory regulatory information, while others are advisory to assist inspection personnel. Regulatory documentation includes Type Certificate Data Sheets (TCDS), Aircraft Specifications, Supplemental Type Certificates (STC), and Airworthiness Directives (AD), Non-regulatory information includes Advisory Circulars (AC). You should be familiar with the general content of the current revision of all government and manufacturer documents related to an aircraft component you are inspecting. Maintenance and service manuals Manufacturers produce technical documents to maintain and service their products. The titles and content of these publications vary between manufacturers. However, the typical maintenance manual provides information on routine servicing, systems descriptions and functions, handling procedures, and removal and installation of components. Additionally, these manuals contain basic repair procedures and troubleshooting guides for common malfunctions. With regard to airworthiness inspections, the manuals contain Issue No. 0 ET-PP04.1 Page 1 of 148  Ethiopian Aviation Academy Aviation Maintenance Revision No. 0 Training March 2020 ET-PP04 M01: Aircraft Engine Inspection, Maintenance, Operation and Troubleshooting detailed instructions and checklists for determining the condition of the aircraft and its components. Engine and propeller airworthiness inspection information is often located in an airframe manufacturer's manuals. However, when inspecting subassemblies such as the engine, the propeller, and accessories, it is extremely beneficial to have access to the component manufacturer’s maintenance publications. Maintenance publications The Aircraft Maintenance Manual (AMM) is written and issued by the aircraft manufacturer and contains the engine related maintenance procedures that are carried out when the engine is installed in the aircraft. The engine manual is written and issued by the engine manufacturer and contains the overhaul and repair procedures including the approved inspection criteria, tolerances and data that are used when the engine has been removed from the aircraft and is in an engine maintenance facility. The manuals are published in the ATA 100 manual format. This is a numbering system that was introduced to standardize aircraft and engine manuals. The maintenance publications that related to line maintenance are the Flight Operations Manual, the Aircraft Maintenance Manual, the Illustrated Parts Catalogue and Service Bulletins. The publication relating to off-wing maintenance including overhaul and repair are the Aircraft Overhaul and Repair Manual, the Aircraft Structural Repair Manual, the Engine Manual, Illustrated Parts Catalogue, Component Overhaul and Repair Manuals and Service Bulletins. When an engine is installed in an aircraft the Aircraft Maintenance Manual takes priority over the Engine Manual for all engine related maintenance procedure. The operational procedures in the Flight Operations Manual take priority over all other aircraft related publications. Aircraft Maintenance Manual The Aircraft Maintenance Manual is divided into chapters and groups of chapters. It contains all the information required to service, diagnose, check/inspect, test, adjust, clean, repair, and replace all the systems and equipment installed in the aircraft including the installed engine and propellers whilst the aircraft is on line or hangar maintenance. The manual is divided into chapters and groups of chapters in accordance with the ATA 100 numbering system. Each chapter is further sub-divided into the following topics: Descriptions and operation Pages 001-99 Troubleshooting Pages 101-199 Maintenance practices Pages 201-299 Servicing Pages 301-399 Removal/Installation Pages 401-499 Adjustment test Pages 501-599 Inspection/check Pages 601-699 Cleaning/painting Pages 701-799 Issue No. 0 ET-PP04.1 Page 2 of 148  Ethiopian Aviation Academy Aviation Maintenance Revision No. 0 Training March 2020 ET-PP04 M01: Aircraft Engine Inspection, Maintenance, Operation and Troubleshooting Approved repairs Pages 801-899 The chapters are grouped as follows Power plant group Chapter 70 standard practices Chapter 71 power plant Chapter 72 engine Chapter 73 fuel Chapter 74 ignition Chapter 75 engine air Chapter 76 engine controls Chapter 77 engine indicating Chapter 78 engine exhaust Chapter 79 engine oil Chapter 80 engine starting Each chapter is further sub-divided into sections and subjects to accommodate subsystems and units. For example 71-11-02 would be read as follows: 71 is the chapter number for Power plant, 11 is the section number for Engine cowlings and 02 is the subject Fan cowl. Engine Maintenance Manual The engine manual is issued by the engine manufacturers and covers the off-wing overhaul/repair information for the engine. Its uses the ATA 100 numbering system and consists of Chapters 70 Standard practices, 71 Power plant, 72 Engine and 78 Exhaust. It contains the manufacturers approved inspection criteria, tolerance and data. Each engine manual chapter is subdivided into the following topics Module identification page 1-100 Fault isolation page 101-200 Special procedures page 201-300 Removal page 301-400 Installation page 401-500 Disassembly page 501-600 Cleaning page 601-700 Inspection/check page 801-900 Repair page 901-1000 Assembly page 1001-1100 Servicing page 1101 1200 Storage page 1201-1300 Issue No. 0 ET-PP04.1 Page 3 of 148  Ethiopian Aviation Academy Aviation Maintenance Revision No. 0 Training March 2020 ET-PP04 M01: Aircraft Engine Inspection, Maintenance, Operation and Troubleshooting Testing page 1301-1400 The chapter/section/subject breakdown is a three number code that allows an operator to quickly identify the task. 72-00-39 is Chapter 72 Engine, Section 00, 30 Module interface inspection. Component Maintenance Manuals Component Maintenance Manuals contain the detailed overhaul and repair procedures for specific part numbered engine components. They also contain illustrated parts lists. Illustrated Parts Catalogue (IPC) The Illustrated Parts Catalogue is written to the ATA 100 format. It consists of two sections, the Numerical Index and the Detailed Parts List. The index locates parts by their figure number and the same chapter/section/subject indicators that are used in the maintenance manuals. The manual will refer to the relevant Component Maintenance Manual in case where the breakdown of particular components fails outside of the scope of parts list. This catalog presents component breakdowns of structure and equipment in disassembly sequence. Also included are exploded views or cutaway illustrations for all parts and equipment manufactured by the aircraft manufacturer. The Illustrated Parts Catalog (IPC) identifies the location and part numbers of items installed on an aircraft, or in a subassembly component. IPCs exist for all components of the airframe, power plant, propeller, and accessories. The IPC contains multiple assembly drawings and part number references. They contain detailed exploded views of an aircraft and assist in locating and identifying parts. This information is useful during inspections to help locate components that are called out in the airframe manufacturer's inspection checklists or in an AD. Temporary Revision Temporary revisions to maintenance manuals are issued from the manufacturers in the interim period between the normal maintenance manual revisions. They notify operations of changes in maintenance procedures where the continued use of the old procedure could cause damage or affect safety or increase costs. The temporary revisions are inserted into the maintenance manual facing the page they affect. They are incorporated into the manual at the next formal revision and the temporary revision sheet is then removed. When a page in a maintenance manual is revised. A letter “R” appears in the left hand margin by the line that has been changed. Information material Manufacturers issue a number of informal publications to pass information to operators. These include technical newsletters to inform customers about services, service information letters to supplement information on maintenance actions, operating instructions that advise on operating techniques that improve efficiency and lower costs. All these publications are supplementary to the information contained in the approved manuals and do not change it. Issue No. 0 ET-PP04.1 Page 4 of 148  Ethiopian Aviation Academy Aviation Maintenance Revision No. 0 Training March 2020 ET-PP04 M01: Aircraft Engine Inspection, Maintenance, Operation and Troubleshooting Manufacturers overhaul manual Overhaul Manual Manufacturers of engines, propellers, and other components produce overhaul manuals that provide complex disassembly, inspection, and repair instructions. By definition, an overhaul includes disassembly, cleaning, inspection, repair (as required), reassembly, and testing. Each action is covered in detail and must be followed for an item to be overhauled. The manual is required during overhaul, but the information is also useful when evaluating the condition of a component during an airworthiness inspection. The manufacturer’s overhaul manual contains brief descriptive information and detail step by step instructions covering work normally performed on a unit that has been removed from the aircraft/engine. Simple inexpensive items on which overhaul is uneconomical are not covered in the overhaul manual. Table of Limits The Table of Limits found in the manufacturers overhaul manual supplies the information necessary to determine the degree of wear for various parts. In addition to the Table of Limits, overhaul manuals often include illustrations with reference numbers to identify the location of each measurement. In the Table of Limits it will be noted that three dimensions for each measurement are usually given. These are the serviceable limit, new minimum and new maximum. If a measurement exceeds the serviceable limit, the part is no longer suitable for the engine and must not be used. If the dimension is between the serviceable limit and the new maximum, the part can be used but should not ordinarily be reinstalled in an engine being given a major overhaul. The correct dimension for parts installed in a newly overhauled engine should fall between the new minimum and new maximum dimensions. It will be observed that some of the dimension figures in the table are followed by the letter L or T. The L stands for loose and indicates a clearance between the parts. The letter T stands for tight and indicates a "pinch" or "interference" fit. This usually means that one part must be shrunk into the other. Interference fit. A type of fit used when assembling certain mechanical devices. The hole is made smaller than the part that fits into it. The material containing the hole is heated to expand the hole, and the part that fits into the hole is chilled to shrink it. The parts are assembled, and when they reach the same temperature, their fit is so tight they will not loosen in service. Manufacturer’s Bulletins Manufacturers also communicate with aircraft owners, operators, and technicians through service information publications, or communiqués. Service information can be contained in Service Bulletins (SB) and Service Advisories. Issue No. 0 ET-PP04.1 Page 5 of 148  Ethiopian Aviation Academy Aviation Maintenance Revision No. 0 Training March 2020 ET-PP04 M01: Aircraft Engine Inspection, Maintenance, Operation and Troubleshooting Service Bulletins Service bulletins are used by the manufacturers to publish special information concerning equipment and special modification instructions. They fail into two categories, the standard bulletin and alert bulletin. Standard bulletins contain recommendations that improve reliability of equipment or optional improvements. Alert bulletins are for immediate attention and compliance with them is essential on safety grounds. Alert bulletins are frequently enforced with the issue of a CAA Airworthiness Directive. Service bulletins may include:- The purpose for issuing the publication The name of the applicable airframe, engine, or component Detailed instructions for service, adjustment, modification or inspection, and source of parts, if required The estimated number of man-hours required to accomplish the job Sample Alert and standard SB first page on figure 1-1 & 1-2 Issue No. 0 ET-PP04.1 Page 6 of 148  Ethiopian Aviation Academy Aviation Maintenance Revision No. 0 Training March 2020 ET-PP04 M01: Aircraft Engine Inspection, Maintenance, Operation and Troubleshooting Figure 1-1 Issue No. 0 ET-PP04.1 Page 7 of 148  Ethiopian Aviation Academy Aviation Maintenance Revision No. 0 Training March 2020 ET-PP04 M01: Aircraft Engine Inspection, Maintenance, Operation and Troubleshooting Figure 1-2 Issue No. 0 ET-PP04.1 Page 8 of 148  Ethiopian Aviation Academy Aviation Maintenance Revision No. 0 Training March 2020 ET-PP04 M01: Aircraft Engine Inspection, Maintenance, Operation and Troubleshooting Airworthiness Directives A primary safety function of the FAA is to require correction of unsafe conditions found in an aircraft, aircraft engine, propeller, or appliance when such conditions exist and are likely to exist or develop in other products of the same design. The unsafe condition may exist because of a design defect, maintenance, or other causes. Title 14 of the Code of Federal Regulations (14 CFR) part 39, Airworthiness Directives, defines the authority and responsibility of the Administrator for requiring the necessary corrective action. The Airworthiness Directives (ADs) are published to notify aircraft owners and other interested persons of unsafe conditions and to prescribe the conditions under which the product may continue to be operated. Airworthiness Directives are Federal Aviation Regulations and must be complied with unless specific exemption is granted. Airworthiness Directives may be divided into two categories: (1) those of an emergency nature requiring immediate compliance upon receipt and (2) those of a less urgent nature requiring compliance within a relatively longer period of time. Also, ADs may be a onetime compliance item or a recurring item that requires future inspection on an hourly basis (accrued flight time since last compliance) or a calendar time basis. The contents of ADs include the aircraft, engine, propeller, or appliance model and serial numbers affected. Also included are the compliance time or period, a description of the difficulty experienced, and the necessary corrective action. An Airworthiness Directive (AD) is issued as an amendment to 14 CFR 39 and its instructions must be followed. Registered aircraft owners receive copies of ADs from the FAA whenever a defect is identified that applies to the make and model of their aircraft. The AD is sent to the address indicated on the aircraft registration certificate, or if updated, the address from the FAA database. It is the responsibility of the aircraft owner to determine the necessary action for compliance. During an airworthiness inspection, it is the responsibility of the aircraft maintenance technician to comply with all applicable ADs before returning an aircraft to service. ADs are also available online through the FAA website or commercial providers of aviation data. During an airworthiness inspection, an aircraft maintenance technician must verify that each AD has been complied with, according to the text of the AD. This task requires a thorough review of each AD record entry in the aircraft's maintenance records and often requires verification by examining the engine or power plant. Although an AD might apply to the make and model of an engine or propeller, a component may be exempt. When a component is exempt, it must still be noted in the AD record with a brief explanation of the reason. Many ADs also require a maintenance record entry noting any determination that an aircraft or component is exempt from an AD. If this maintenance entry is not made, the AD has not been complied with, even if no corrective action is required Issue No. 0 ET-PP04.1 Page 9 of 148  Ethiopian Aviation Academy Aviation Maintenance Revision No. 0 Training March 2020 ET-PP04 M01: Aircraft Engine Inspection, Maintenance, Operation and Troubleshooting If the FAA issues an AD that requires adherence to the specific manufacturer's instructions, the FAA has reviewed and approved the manufacturer's instructions. Advisory Circulars Many of the technical publications and regulations issued by the FAA are complex. The FAA issues Advisory Circulars (AC) to inform, explain, and provide further guidance for operating and maintaining aircraft. Advisory Circulars are informational only; they cannot be used as approved data unless incorporated in a regulation or airworthiness directive. Code of Federal Regulations (CFRs) The CFRs were established by law to provide for the safe and orderly conduct of flight operations and to prescribe airmen privileges and limitations. Knowledge of the CFRs is necessary during the performance of maintenance, since all work done on aircraft must comply with CFR provisions. Specification ATA chapter specifications In an effort to standardize the format for the way in which maintenance information is presented in aircraft maintenance manuals, the Air Transport Association of America (ATA) issued specifications for Manufacturers Technical Data. The original specification was called ATA Spec 100. Over the years, Spec 100 has been continuously revised and updated. Eventually, ATA Spec 2100 was developed for electronic documentation. These two specifications evolved into one document called ATA Spec 2200. As a result of this standardization, maintenance technicians can always find information regarding a particular system in the same section of an aircraft maintenance manual, regardless of manufacturer. For example, if you are seeking information about the Ignition system on any engine, you will always find that information in section (chapter) 74. The Air Transportation Association of America, an organization of air carriers has established many standards and procedures that make airline operation more effective and efficient. One of the specifications of value to us in the maintenance field is the A.T.A. Specification 100, which is a standard for the presentation of technical information. Because of this specification, maintenance information from any of the manufacturers of transport aircraft is presented in a specific manner. For example, regardless of the aircraft manufacturer chapter 72 of an aircraft maintenance manual will deal with the turbine engine power plant. More specifically section 30 of chapter 72 will deal with the engines compressor. The A.T.A Specification 100 system has now found its way into all facets of aviation, including General Aviation aircraft. ATA groups Aircraft general group:- chapter 5 through 12 Airframe systems group:- chapter 20 through 49 Issue No. 0 ET-PP04.1 Page 10 of 148  Ethiopian Aviation Academy Aviation Maintenance Revision No. 0 Training March 2020 ET-PP04 M01: Aircraft Engine Inspection, Maintenance, Operation and Troubleshooting Structure group:- chapter 51 through 57 Propeller group:- chapter 61 Power plant group:- chapter 70 through 80 Type Certificate Data Sheets After the FAA approves and verifies the design of a power plant or propeller, they publish a Type Certificate Data Sheet (TCDS), which lists the drawings and specifications that define the configuration and features of the product. The airworthiness of a component is determined by conformity to the TCDS. The TCDS is FAA-approved data. Any modification to an aircraft component that deviates from the TCDS is considered a major alteration and must be documented on an FAA Major Repair or Alteration Form 337. These forms must be retained with an aircraft's permanent maintenance records and accounted for during airworthiness inspections TCDSs are granted to the manufacturers of airframes, power plants, and propellers. The airframe TCDS defines the allowable power plant and propeller combinations that can be installed on an aircraft, but the specific type design requirements of a power plant or propeller are contained in their respective TCDS. To determine if an engine or propeller can be installed on a particular airframe, you must consult the airframe TCDS. In addition, the airframe TCDS provides other important information about the installation of these components, such as engine and propeller limitations, required placards, and the types and quantities of fuel and engine oil. The type certificate data sheet (TCDS) describes the type design and sets forth the limitations prescribed by the applicable CFR part. It also includes any other limitations and information found necessary for type certification of a particular model aircraft/engine. Type certificate data sheets are numbered in the upper right-hand corner of each page. This number is the same as the type certificate number. The name of the type certificate holder, together with all of the approved models, appears immediately below the type certificate number. The issue date completes this group. This information is contained within a bordered text box to set it off. The data sheet is separated into one or more sections. Each section is identified by a Roman numeral followed by the model designation of the aircraft/engine to which the section pertains. The category or categories in which the aircraft can be certificated are shown in parentheses following the model number. Also included is the approval date shown on the type certificate. See below sample EASA Type certificate data sheet first page on figure 1-3 Issue No. 0 ET-PP04.1 Page 11 of 148  Ethiopian Aviation Academy Aviation Maintenance Revision No. 0 Training March 2020 ET-PP04 M01: Aircraft Engine Inspection, Maintenance, Operation and Troubleshooting Figure 1-3 Issue No. 0 ET-PP04.1 Page 12 of 148  Ethiopian Aviation Academy Aviation Maintenance Revision No. 0 Training March 2020 ET-PP04 M01: Aircraft Engine Inspection, Maintenance, Operation and Troubleshooting Supplemental type certificates (STC) The FAA allows a product to be altered from its original type design when specific safety and design requirements are met. A Supplemental Type Certificate (STC) describes the methods and techniques that permit an aircraft to be approved for return to service without additional engineering or flight test requirements. A list of all approved STCs is published in the Summary of Supplemental Type Certificates and available on the FAA website. After an STC has been obtained, the instructions must be followed exactly and all changes documented on an FAA Form 337. Before a return to service, the aircraft must be inspected to ensure that all conditions of the STC have been met. The inspection can be completed by an FAA airworthiness inspector, an aircraft maintenance technician holding an Inspection Authorization (IA), a properly certificated repair station, or another approved entity. Because each STC contains unique information, the installation and maintenance instructions must be retained with the aircraft records for future reference. Forms and Records Forms can be Airmen (pilots, Mechanics, others) forms Designee, Aircraft Registration, Airport Employment forms Other government forms Most frequently used maintenance related FAA FORMS are FAA 337- Major repair & Alteration (Airframe, Powerplant, Propeller or Appliance) 8130-3 Authorized Release Certificate 8130-6 Application for Airworthiness Certificate 8610-1 Mechanic’s Application for Inspection Authorization 8120-11 Suspected Unapproved Parts Report 8710-1 Airman Certificate and/or Rating Application Maintenance release At the completion of any maintenance task a person authorized by the national airworthiness authority signs a maintenance release stating that maintenance has been performed in accordance with the applicable airworthiness requirements. In the case of a certified aircraft this may be an Aircraft Maintenance Engineer or Aircraft Maintenance Technician, while for amateur-built aircraft this may be the owner or builder of the aircraft. A maintenance release can be called a certificate of release to service (CRS). Maintenance Record Entries Federal Aviation Regulations require an entry in the aircraft’s permanent maintenance record whenever an inspection is completed. For annual and progressive inspections, the return to Issue No. 0 ET-PP04.1 Page 13 of 148  Ethiopian Aviation Academy Aviation Maintenance Revision No. 0 Training March 2020 ET-PP04 M01: Aircraft Engine Inspection, Maintenance, Operation and Troubleshooting service record entry must be done in the airframe logbook (although many technicians also document the work in the other equipment logbooks). For 100-hour inspections, the return to service statement for an engine is made in the engine maintenance logbook, and the propeller inspection is recorded in the propeller maintenance logbook. Bear in mind that when a maintenance record entry is made after completing maintenance such as repairs or servicing, the signature constitutes the approval of the aircraft for return to service only for the work performed. Maintenance record entry for compliance with an Airworthiness Directive entries should be clear and concise as to what work was done, how it was done, and if recurring, when it must be redone. The maintenance logbook entry for an airworthiness inspection should include: The date the inspection is completed. The total time in service of the aircraft, engine, or propeller, as appropriate to the equipment inspected. The type of inspection performed Your signature. Your certificate number and type of ratings held If either a major repair or major alteration is performed on an engine or propeller, you must record an appropriate log entry and complete two identical FAA Form 337s. Provide one form to the aircraft owner and submit the other to the local FAA Field Service District Office within 48 hours from the aircraft’s approval for return to service. Logbook entries After an overhaul is complete, you must make the appropriate maintenance entries. In addition to recording the information required by the Federal Aviation Regulations, list all of the new parts you installed. Furthermore, you should document the details from all dimensional and structural inspections, along with evidence of compliance with airworthiness directives and service bulletins. For any major repairs, you must complete form 337 and keep one of the copies in the engine logbook. How long Records must be kept? Making Maintenance Record Entries 14 CFR 43.9 and 43.11 require the technician to make appropriate entries of maintenance actions or inspection results in the aircraft maintenance record. 14 CFR 91.417 defines how long those records must be kept. Whenever maintenance preventive maintenance rebuilding or alteration work occurs on an aircraft engine, propeller, appliance or component part a maintenance record entry must be created. The importance of compliance with this requirement cannot be overemphasized. Complete and organized maintenance logs for an aircraft can have significant (and usually positive) effect during the buy/sell negotiations of an aircraft. On the other hand poorly organized and incomplete logs can have a detrimental effect upon the selling price of an aircraft. Issue No. 0 ET-PP04.1 Page 14 of 148  Ethiopian Aviation Academy Aviation Maintenance Revision No. 0 Training March 2020 ET-PP04 M01: Aircraft Engine Inspection, Maintenance, Operation and Troubleshooting Temporary Records These are records that must be kept by the owner until the work is repeated, superseded or 1 year has transpired since the work was performed. These are typically records referring to maintenance, preventive maintenance, alteration and all inspections. They include a description of the work performed (or reference to the FAA accepted data); the date of completion and the name, signature and certificate number of the person doing the return to service (RTS) Permanent Records These records must be retained by the owner during the time he or she operates the aircraft. They are transferred with the aircraft at the time of sale. Typically these are documents relating to the total time in service, current status of life-limited parts, time since last overhaul, current inspection status, current status of applicable AD notes, and major alteration forms as required by 14 CFR 43.9 Electronic Records During the last 25 years, the field of aviation maintenance has seen a significant change in the documentation requirements for aircraft and related parts. Nowhere is that change seen as revolutionary as the introductions of electronic data and record retention. Just as the arrival of the personal computer placed the possibility of the power and versatility of a computer in the hands of the average person, it made it available to the maintenance technician. Initially some technicians developed their own programs for listing data (TCDS, AD notes, and so forth), but soon commercially available programs were developed. Inspection Aviation maintenance technicians and repair station personnel share the burden of determining whether an aircraft is safe for flight by performing airworthiness inspections at specified intervals and performing, or properly deferring, maintenance discrepancies between inspections. Depending on the type of operation and the operating environment, airworthiness inspections vary in scope, detail, and the interval between inspection phases. For example: an aircraft that is used for transporting passengers for hire must be inspected more frequently than one used for personal transportation. This topic details the different types of inspections required on aircraft used in the conduct of various flight operations. The types of inspections required on an aircraft are determined by the requirements of federal regulations and several other factors such as the owners’ or operators’ type of aircraft, choice of inspection programs, or use of the aircraft. In most situations, the owner or operator has a choice of several inspection programs to comply with airworthiness inspection requirements. Prior to beginning an inspection, obtain the appropriate items to ensure compliance with regulations and manufacturer recommendations. Gather the aircraft maintenance records and verify the presence of all required documents. Research the Type Certificate Data Sheets, Airworthiness Directives, Service Bulletins, and other applicable reference materials and acquire the necessary checklists. Issue No. 0 ET-PP04.1 Page 15 of 148  Ethiopian Aviation Academy Aviation Maintenance Revision No. 0 Training March 2020 ET-PP04 M01: Aircraft Engine Inspection, Maintenance, Operation and Troubleshooting Engine Inspection Fundamentals Inspections are visual examinations and manual checks to determine the condition of an aircraft or engine. An engine inspection can range from a casual walk around to detail inspection involving complete disassembly and the use of complex inspection aids. An inspection system consists of several processes, including reports made by mechanics or the pilots. An inspection system is designed to maintain an engine in the best possible condition. Thorough and repeated inspections must be considered the backbone of a good maintenance program. It has been proven that regularly scheduled inspections and preventive maintenance assure airworthiness. Operating failures and malfunctions of equipment are appreciably reduced if excessive wear or minor defects are detected and corrected early. The importance of inspections and the proper use of records concerning these inspections cannot overemphasize. Engine inspection may range from preflight inspections to detailed inspections. The time intervals for the inspections periods vary with the models of engine and the types of operations being conducted. The engine manufacturer’s instruction should be consulted when establishing inspection intervals. Human factors during Inspection Through an analysis of aircraft accidents and incidents that occurred during the past decades. It has been determined that the rate of aircraft accident and incident due to structural and mechanical failures has decreased. On the other hand, the accident and incident rates that were attributed to human error increased, negating many of the safety improvements in aircraft design and mechanical reliability. Further analysis revealed that, in many cases, policies and procedures were in place that, if properly followed would have prevented many accidents and incidents that were attributed to maintenance personnel errors. Accidents and incidents that occur because of human error or over sight are commonly referred to as human factor some areas where human errors occur during inspections including the following: Failure to properly follow regulatory and manufacturers inspection instruction, including incomplete work due to missed steps or failure to follow maintenance instructions in the correct sequence Failure to perform follow-up maintenance activities with an effective secondary inspection by an experienced supervisor or someone with Equal or better qualifications than the person who performed the original inspection Failure to identify defects due to improper or inadequate inspection procedures, or complacency on the part of individuals during the inspection or maintenance check. Inappropriate or inadequate use of special tools when conducting inspections. Deviation from established and approved inspection methods and procedures. Of course there are many other areas where human error can enter into aircraft maintenance and inspection operations. In many cases, repair facilities have sufficient policies and procedures in place to minimize human factor events from occurring. However, if policies and procedures are not properly followed, or if discrepancies in policies and procedures are not Issue No. 0 ET-PP04.1 Page 16 of 148  Ethiopian Aviation Academy Aviation Maintenance Revision No. 0 Training March 2020 ET-PP04 M01: Aircraft Engine Inspection, Maintenance, Operation and Troubleshooting identified, then the potential for maintenance related human factor accidents and incidents increase dramatically. If you become employed as a technician or inspector in a maintenance facility, you are required to follow your company policies and procedures when conducting inspection. Always use a checklist when performing an inspection. The checklist may be of your own design, one provided by the manufacturer of the equipment being inspected, or one obtained from some other source. Inspection designations Aircraft and engine manufacturers designate turbine engine inspection tasks to help classify and identify specific inspection activities. These designations are often grouped into routine or non-routine inspection classifications. Routine Inspections Routine inspections are those that are mandated by an approved inspection schedule or Federal regulations. All routine inspections are performed periodically at intervals specified by FAA approved company or airline operations manuals. Examples of routine inspections include preflight inspections, airworthiness inspection programs, cold section inspection, and hot section inspections. For the purpose of determining their overall condition, 14 CFR provides for the inspection of all civil aircraft at specific intervals, depending generally upon the type of operations in which they are engaged. The following are examples of routine inspections Pilots are required to follow a checklist contained within the Pilot’s Operating Handbook (POH) when operating aircraft. The first section of a checklist includes a section entitled Preflight Inspection. The preflight inspection checklist includes a “walk-around” section listing items that the pilot is to visually check for general condition as he or she walks around the airplane. Also, the pilot must ensure that fuel, oil and other items required for flight are at the proper levels and not contaminated. Additionally, it is the pilot’s responsibility to review the airworthiness certificate, maintenance records, and other required paperwork to verify that the aircraft is indeed airworthy. After each flight, it is recommended that the pilot or mechanic conduct a post flight inspection to detect any problems that might require repair or servicing before the next flight. Title 14 of the Code of Federal Regulations (14 CFR) part 91 discusses the basic requirements for annual and 100-hour inspections. With some exceptions, all aircraft must have a complete inspection annually. Aircraft that are used for commercial purposes and are likely to be used more frequently than noncommercial aircraft must have this complete inspection every 100 hours. The scope and Issue No. 0 ET-PP04.1 Page 17 of 148  Ethiopian Aviation Academy Aviation Maintenance Revision No. 0 Training March 2020 ET-PP04 M01: Aircraft Engine Inspection, Maintenance, Operation and Troubleshooting detail of items to be included in annual and 100-hour inspections is included as appendix D of 14 CFR part 43 A properly written checklist will include all the items of appendix D. Although the scope and detail of annual and 100-hour inspections is identical, there are two significant differences. One difference involves persons authorized to conduct them. A certified airframe and powerplant maintenance technician can conduct a 100-hour inspection, whereas an annual inspection must be conducted by a certified airframe and powerplant maintenance technician with inspection authorization (IA). The other difference involves authorized over flight of the maximum 100 hours before inspection. An aircraft may be flown up to 10 hours beyond the 100-hour limit if necessary to fly to a destination where the inspection is to be conducted. Each person performing an annual or 100-hour inspection shall inspect (where applicable) components of the engine and nacelle group as follows: (1) Engine section—for visual evidence of excessive oil, fuel, or hydraulic leaks, and sources of such leaks. (2) Studs and nuts—for improper torqueing and obvious defects. (3) Internal engine—for compressor, combustion chamber & turbine and for metal particles or foreign matter on screens and sump drain plugs. If there is for improper internal condition and improper internal tolerances. (4) Engine mounts—for cracks, looseness of mounting, and looseness of engine to mount. (5) Flexible vibration dampeners—for poor condition and deterioration. (6) Engine controls—for defects, improper travel, and improper safetying. (7) Lines, hoses, and clamps—for leaks, improper condition, and looseness. (8) Exhaust stacks—for cracks, defects, and improper attachment. (9) Accessories—for apparent defects in security of mounting. (10) All systems—for improper installation, poor general condition, defects, and insecure attachment. (11) Cowling—for cracks and defects. Appendix D to Part 43—Scope and Detail of Items (as Applicable to the Particular Aircraft) To Be Included in Annual and 100-Hour Inspections. Because the scope and detail of an annual inspection is very extensive and could keep an aircraft out of service for a considerable length of time, alternative inspection programs designed to minimize down time may be utilized. A progressive inspection program allows an aircraft to be inspected progressively. The scope and detail of an annual inspection is essentially divided into segments or phases (typically four to six). Completion of all the phases completes a cycle that satisfies the requirements of an annual inspection. The advantage of such a program is that any required segment may be completed overnight and thus enable the aircraft to fly daily without missing any revenue earning potential. Progressive inspection programs include routine items such as engine oil changes and Issue No. 0 ET-PP04.1 Page 18 of 148  Ethiopian Aviation Academy Aviation Maintenance Revision No. 0 Training March 2020 ET-PP04 M01: Aircraft Engine Inspection, Maintenance, Operation and Troubleshooting detailed items such as flight control cable inspection. Routine items are accomplished each time the aircraft comes in for a phase inspection and detailed items focus on detailed inspection of specific areas. Detailed inspections are typically done once each cycle. A cycle must be completed within 12 months. If all required phases are not completed within 12 months, the remaining phase inspections must be conducted before the end of the 12th month from when the first phase was completed. Each registered owner or operator of an aircraft desiring to use a progressive inspection program must submit a written request to the FAA Flight Standards District Office (FSDO) having jurisdiction over the area in which the applicant is located. Title 14 of the Code of Federal Regulations (14 CFR) part 91, §91.409(d) Continuous inspection programs are similar to progressive inspection programs, except that they apply to large or turbine-powered aircraft and are therefore more complicated. Like progressive inspection programs, they require approval by the FAA Administrator. The approval may be sought based upon the type of operation and the CFR parts under which the aircraft will be operated. The maintenance program for commercially operated aircraft must be detailed in the approved operations specifications (Op Specs) of the commercial certificate holder. Airlines utilize a continuous maintenance program that includes both routine and detailed inspections. However, the detailed inspections may include different levels of detail. Often referred to as “checks,” the A-check, B-check, C-check, and D-checks involve increasing levels of detail. A-checks are the least comprehensive and occur frequently. D-checks, on the other hand, are extremely comprehensive, involving major disassembly, removal, overhaul, and inspection of systems and components. They might occur only three to six times during the service life of an aircraft. Non- routine inspection A non- routine inspection is any inspection that must be done as a result of a component failure or incident that could potentially damage an engine. Some examples of incidents requiring a non-routine inspection includes ingestion of birds, ice, or other foreign objects, and temperature or rpm over limit incidents. Although damage to compressor or turbine blades may not be immediately noticed with respect to engine performance after an incident, the need for an inspection still exists. For example, if foreign object damage occurs, the initial damage may not be noticed immediately. However, if gone unchecked the damage could result in blade failure which may cause blade fragments to travel through the engine causing substantial greater damage or the total destruction of the engine. Methods of Inspection The inspection of engine parts during maintenance/overhaul is divided into three categories: 1. Visual 2. Dimensional 3. Structural NDT Issue No. 0 ET-PP04.1 Page 19 of 148  Ethiopian Aviation Academy Aviation Maintenance Revision No. 0 Training March 2020 ET-PP04 M01: Aircraft Engine Inspection, Maintenance, Operation and Troubleshooting Many defects on the engine components can be detected visually, and a determination of airworthiness can be made at this time. If, by visual inspection, the component is determined to be not airworthy, the part is rejected and no further inspection or repair is required. Structural failures can be determined by several different methods. Magnetic parts can readily be examined by the magnetic particle method. Other methods, such as dye penetrate, eddy current, ultra sound, and X-ray, can also be used. The first two methods are aimed at determining structural failures in the parts, while the last method deals with the size and shape of each part. By using very accurate measuring equipment, each engine component can be dimensionally evaluated and compared to service limits and standards (tolerances) set by the manufacturers. Visual inspection should precede all other inspection procedures. Parts should not be cleaned before a preliminary visual inspection, since indications of a failure may often be detected from the residual deposits of metallic particles in some recesses in the engine. Visual inspection can be enhanced by looking at the suspect area with a bright light, a magnifying glass, and a mirror (when required). Some defects might be so obvious that further inspection methods are not required. The lack of visible defects does not necessarily mean further inspection is unnecessary. Some defects may lie beneath the surface or may be so small that the human eye, even with the assistance of a magnifying glass, cannot detect them. Visual inspection will require  Adequate lighting  20/20 vision by inspection personnel  Common visual aids  Flash light  Inspection mirror  Magnifying glass  Borescopes The dimensional inspection is used to assure that the engine’s component parts and clearances meet the manufacturer’s specifications. These specs are listed in a table of limits, which lists serviceable limits and the manufacturer’s new part maximum and minimum dimensions. Many measuring tools are used to perform the dimensional inspection of the engine. Compare the resulting measurements with those in the table of limits. Measuring tools are: Issue No. 0 ET-PP04.1 Page 20 of 148  Ethiopian Aviation Academy Aviation Maintenance Revision No. 0 Training March 2020 ET-PP04 M01: Aircraft Engine Inspection, Maintenance, Operation and Troubleshooting Steel rule, combination set, calipers (inside & outside), scribers, Vernier calipers, micrometer, dial indicator, feeler gages, telescoping gages, etc. Examples The edge thickness can be measured with sufficient accuracy by a dial indicator and a surface plate Internal measurements can be made by using telescoping gauges, and then measuring the telescoping gauge with a micrometer Using a surface plate and a dial indicator, measure the shaft run out. Borescope. Is an internal viewing device which allows you to visually inspect areas inside a turbine engine without major component disassembly? A borescope may be compared to a small periscope with an eyepiece at one end and a strong light, mirror, and lens at the other end. A conducting cord connects the probe to a control device for adjusting light intensity and lens magnification or focusing. The instrument consists of a light, mirror, and magnifying lens mounted inside a small- diameter tube that is inserted into a turbine engine through borescope inspection ports. Inspection by use of a borescope is essentially a visual inspection. A borescope is a device that enables the inspector to see inside areas that could not otherwise be inspected without disassembly. Functions: Inspect the main areas such as compressor, combustion chamber, turbine sections, gearbox, etc. without disassembling the engine. Borescopes are available in two basic configurations. The simpler of the two is a rigid type of small diameter telescope with a tiny mirror at the end that enables the user to see around corners. The other type uses fiber optics that enables greater flexibility. Many borescopes provide images that can be displayed on a computer or video monitor for better interpretation of what is being viewed and to record images for future reference. Most borescopes also include a light to illuminate the area being viewed. Borescope Equipment: Fiberscope Light source Guide tubes Video camera (optional) Video cassette recorder (VCR) optional Caution: The Borescope is fragile and vulnerable to radiation, shock, twisting and pinching. Extreme care is required during handling to ensure damage and serviceability problems are avoided Issue No. 0 ET-PP04.1 Page 21 of 148  Ethiopian Aviation Academy Aviation Maintenance Revision No. 0 Training March 2020 ET-PP04 M01: Aircraft Engine Inspection, Maintenance, Operation and Troubleshooting Excessive twisting of Fiberscope can sever optic fibers. Do not rotate Fiberscope tip by turning the eyepiece only assist rotating motion of eyepiece with one in same direction as part of fiberscope closest to entry into engine Heat can damage the borescope. Engine temperature must be less than the prescribe limit before an inspection can be carried out. If required carry out dry motoring runs to accelerate cooling. Do not submerge in liquid. All current gas turbine engine types are provided with borescope access holes to enable the use of fiber light guides and eyepieces for inspecting the normally inaccessible parts of the engine. The holes are typically positioned to give access to the HP (high pressure) compressor, the combustion chamber and the turbines. The access holes are fitted with removable sealing plugs and it is essential that these are refitted following an inspection as a failure to do so will lead to gas teaks and nacelle overheat. Each borescope plug is numbered and this is used to identify the engine interior region that it gives access to. The plug threads should be lubricated with anti-seize before being fitted. The procedure for carrying out borescope inspections may be found in the maintenance manual Chapter 72 (engine). Borescope inspections are carried out during routine servicing/inspection, during fault diagnosis, after foreign object ingestion and after compressor surges. Advanced Borescope (Boroblending) A more advanced borescope design equipped with a video viewing system, a camera, and a grinding tip. The rotary file or stone at the tip is designed for use in specific engine locations to blend out small areas of damage in order to remove stress points Issue No. 0 ET-PP04.1 Page 22 of 148  Ethiopian Aviation Academy Aviation Maintenance Revision No. 0 Training March 2020 ET-PP04 M01: Aircraft Engine Inspection, Maintenance, Operation and Troubleshooting Figure 1-4 Borescope with blending tool i. Magnetic Inspection ii. Fluorescent penetrate Inspection iii. Dye Penetrate Inspection I. Magnetic Particle Inspection Magnetic particle inspection is a method of detecting invisible cracks and other defects in ferromagnetic materials such as iron and steel. It is not applicable to nonmagnetic materials. In rapidly rotating, reciprocating, vibrating, and other highly stressed aircraft parts, small defects often develop to the point that they cause complete failure of the part. Magnetic particle inspection has proven extremely reliable for the rapid detection of such defects located on or near the surface. With this method of inspection, the location of the defect is indicated and the approximate size and shape are outlined. The inspection process consists of magnetizing the part and then applying ferromagnetic particles to the surface area to be inspected. The ferromagnetic particles (indicating medium) may be held in suspension in a liquid that is flushed over the part; the part may be immersed in the suspension liquid; or the particles, in dry powder form, may be dusted over the surface of the part. The wet process is more commonly used in the inspection of aircraft parts. If a discontinuity is present, the magnetic lines of force will be disturbed and opposite poles will exist on either side of the discontinuity. The magnetized particles thus form a pattern in Issue No. 0 ET-PP04.1 Page 23 of 148  Ethiopian Aviation Academy Aviation Maintenance Revision No. 0 Training March 2020 ET-PP04 M01: Aircraft Engine Inspection, Maintenance, Operation and Troubleshooting the magnetic field between the opposite poles. This pattern, known as an “indication,” assumes the approximate shape of the surface projection of the discontinuity. A discontinuity may be defined as an interruption in the normal physical structure or configuration of a part, such as a crack, forging lap, seam, inclusion, porosity, and the like A discontinuity may or may not affect the usefulness of a part. Figure 1-5 Development of Indications When a discontinuity in a magnetized material is open to the surface, and a magnetic substance (indicating medium) is available on the surface, the flux leakage at the discontinuity tends to form the indicating medium into a path of higher permeability. (Permeability is a term used to refer to the ease with which a magnetic flux can be established in a given magnetic circuit.) Because of the magnetism in the part and the adherence of the magnetic particles to each other, the indication remains on the surface of the part in the form of an approximate outline of the discontinuity that is immediately below it. The same action takes place when the discontinuity is not open to the surface, but since the amount of flux leakage is less, fewer particles are held in place and a fainter and less sharply defined indication is obtained. If the discontinuity is very far below the surface, there may be no flux leakage and no indication on the surface. The flux leakage at a transverse discontinuity is shown in Figure 1-6. The flux leakage at a longitudinal discontinuity is shown in Figure 1-7. Figure 1-6. Flux leakage at transverse discontinuity. Figure 1-7. Flux leakage at longitudinal discontinuity Issue No. 0 ET-PP04.1 Page 24 of 148  Ethiopian Aviation Academy Aviation Maintenance Revision No. 0 Training March 2020 ET-PP04 M01: Aircraft Engine Inspection, Maintenance, Operation and Troubleshooting Types of Discontinuities Disclosed The following types of discontinuities are normally detected by the magnetic particle test: cracks, laps, seams, cold shuts, inclusions, splits, tears, pipes, and voids. All of these may affect the reliability of parts in service. Preparation of Parts for Testing Grease, oil, and dirt must be cleaned from all parts before they are tested. Cleaning is very important since any grease or other foreign material present can produce non relevant indications due to magnetic particles adhering to the foreign material as the suspension drains from the part. Grease or foreign material in sufficient amount over a discontinuity may also prevent the formation of a pattern at the discontinuity. It is not advisable to depend upon the magnetic particle suspension to clean the part. Cleaning by suspension is not thorough and any foreign materials so removed from the part will contaminate the suspension, thereby reducing its effectiveness. In the dry procedure, thorough cleaning is absolutely necessary. All small openings and oil holes leading to internal passages or cavities should be plugged with paraffin or other suitable nonabrasive material. Coatings of cadmium, copper, tin and zinc do not interfere with the satisfactory performance of magnetic particle inspection, unless the coatings are unusually heavy or the discontinuities to be detected are unusually small. Chromium and nickel plating generally will not interfere with indications of cracks open to the surface of the base metal but will prevent indications of fine discontinuities, such as inclusions. Because it is more strongly magnetic, nickel plating is more effective than chromium plating in preventing the formation of indications. Effect of Flux Direction To locate a defect in a part, it is essential that the magnetic lines of force pass approximately perpendicular to the defect. It is therefore necessary to induce magnetic flux in more than one direction since defects are likely to exist at any angle to the major axis of the part. This requires two separate magnetizing operations, referred to as circular magnetization and longitudinal magnetization. Issue No. 0 ET-PP04.1 Page 25 of 148  Ethiopian Aviation Academy Aviation Maintenance Revision No. 0 Training March 2020 ET-PP04 M01: Aircraft Engine Inspection, Maintenance, Operation and Troubleshooting Figure 1-8 Circular magnetizations Figure 1-9 longitudinal magnetization The effect of flux direction is illustrated in Figure 1-8 & 1-9 Circular magnetization is the induction of a magnetic field consisting of concentric circles of force about and within the part which is achieved by passing electric current through the part. This type of magnetization will locate defects running approximately parallel to the axis of the part In longitudinal magnetization, the magnetic field is produced in a direction parallel to the long axis of the part. This is accomplished by placing the part in a solenoid excited by electric current. The metal part then becomes the core of an electromagnet and is magnetized by induction from the magnetic field created in the solenoid. Issue No. 0 ET-PP04.1 Page 26 of 148  Ethiopian Aviation Academy Aviation Maintenance Revision No. 0 Training March 2020 ET-PP04 M01: Aircraft Engine Inspection, Maintenance, Operation and Troubleshooting Figure 1-10. Effect of flux direction on strength of indication Demagnetization The permanent magnetism remaining after inspection must be removed by a demagnetization operation if the part is to be returned to service. Parts of operating mechanisms must be demagnetized to prevent magnetized parts from attracting filings, grindings, or chips inadvertently left in the system, or steel particles resulting from operational wear. Degaussing is the process of decreasing or eliminating a remnant magnetic field. It is named after the gauss, a unit of magnetism, which in turn was named after Carl Friedrich Gauss. Due to magnetic hysteresis, it is generally not possible to reduce a magnetic field completely to zero, so degaussing typically induces a very small "known" field referred to as bias. Degaussing was originally applied to reduce ships' magnetic signatures during the Second World War. Degaussing is also used to reduce magnetic fields in CRT monitors and to destroy data held on magnetic data storage. Magnaglo Inspection Magnaglo inspection is similar to the preceding method, except that a fluorescent particle solution is used and the inspection is made under black light. Efficiency of inspection is increased by the neon-like glow of defects, and smaller flaw indications are more readily seen. This is an excellent method for use on gears, threaded parts, and aircraft engine components. The reddish brown liquid spray or hath that is used consists of Magnaglo paste mixed with a light oil at the ratio of.10 to.25 ounce of paste per gallon of oil. After inspection, the part must be demagnetized and rinsed with a cleaning sol vent. Issue No. 0 ET-PP04.1 Page 27 of 148  Ethiopian Aviation Academy Aviation Maintenance Revision No. 0 Training March 2020 ET-PP04 M01: Aircraft Engine Inspection, Maintenance, Operation and Troubleshooting Figure 1-11 Fixed general-purpose magnetizing unit. Issue No. 0 ET-PP04.1 Page 28 of 148  Ethiopian Aviation Academy Aviation Maintenance Revision No. 0 Training March 2020 ET-PP04 M01: Aircraft Engine Inspection, Maintenance, Operation and Troubleshooting Figure 1-12 Magnetic particle inspection method Liquid Penetrant Inspection Penetrant inspection is a nondestructive test for defects open to the surface in parts made of any nonporous material. It is used with equal success on such metals as aluminum, magnesium, brass, copper, cast iron, stainless steel, and titanium. It may also be used on ceramics, plastics, molded rubber, and glass. Penetrant inspection will detect such defects as surface cracks or porosity. These defects may be caused by fatigue cracks, shrinkage cracks, shrinkage porosity, cold shuts, grinding and heat treat cracks, seams, forging laps, and bursts. Penetrant inspection will also indicate a lack of bond between joined metals. The main disadvantage of penetrant inspection is that the defect must be open to the surface in order to let the penetrant get into the defect. For this reason, if the part in question is made of material which is magnetic, the use of magnetic particle inspection is generally recommended. Issue No. 0 ET-PP04.1 Page 29 of 148  Ethiopian Aviation Academy Aviation Maintenance Revision No. 0 Training March 2020 ET-PP04 M01: Aircraft Engine Inspection, Maintenance, Operation and Troubleshooting Penetrant inspection uses a penetrating liquid that enters a surface opening and remains there, making it clearly visible to the inspector. It calls for visual examination of the part after it has been processed, increasing the visibility of the defect so that it can be detected. Visibility of the penetrating material is increased by the addition of one of two types of dye, visible or fluorescent. The visible penetrant kit consists of dye penetrant, dye remover emulsifier, and developer. II. Fluorescent penetrant Inspection The fluorescent penetrant inspection kit contains a black light (ultraviolet (UV) light) assembly, as well as spray cans of penetrant, cleaner, and developer. The light assembly consists of a power transformer, a flexible power cable, and a hand-held lamp. Due to its size, the lamp may be used in almost any position or location. Briefly, the steps for performing a penetrant inspection are: 1. Thorough cleaning of the metal surface. 2. Applying penetrant. 3. Removing penetrant with remover emulsifier or cleaner. 4. Drying the part. 5. Applying the developer. 6. Inspecting and interpreting results. III. Dye Penetrant Inspection Dye penetrant inspection serves the same purpose as fluorescent penetrant inspection; however, it has the advantage· of being performed without the special equipment required for the fluorescent penetrant inspection. Dye penetrant inspection uses a penetrating liquid that enters a surface opening and remains there, making it clearly visible to the inspector. It calls for visual examination of the part after it has been processed, increasing the visibility of the defect so that it can be detected. Visibility of the penetrating material is increased by the addition of one of two types of dye: visible or fluorescent. When using a fluorescent dye, the inspection is accomplished using an ultraviolet (UV) light source (black light). The steps for performing a dye penetrant inspection are: 1. Thorough cleaning of the metal surface. 2. Applying penetrant. 3. Removing penetrant with remover emulsifier or cleaner. 4. Drying the part. 5. Applying the developer. 6. Inspecting and interpreting results. Issue No. 0 ET-PP04.1 Page 30 of 148  Ethiopian Aviation Academy Aviation Maintenance Revision No. 0 Training March 2020 ET-PP04 M01: Aircraft Engine Inspection, Maintenance, Operation and Troubleshooting Interpretation of Results The success and reliability of a penetrant inspection depends upon the thoroughness with which the part was prepared. Several basic principles applying to penetrant inspection are: 1. The penetrant must enter the defect in order to form an indication. It is important to allow sufficient time so the penetrant can fill the defect. The defect must be clean and free of contaminating materials so that the penetrant is free to enter. 2. If all penetrant is washed out of a defect, an indication cannot be formed. During the washing or rinsing operation, prior to development, it is possible that the penetrant will be removed from within the defect, as well as from the surface. 3. Clean cracks are usually easy to detect. Surface openings that are uncontaminated, regardless of how fine, are seldom difficult to detect with the penetrant inspection. 4. The smaller the defect, the longer the penetrating time. Fine crack-like apertures require a longer penetrating time than defects such as pores. 5. When the part to be inspected is made of a material susceptible to magnetism, it should be inspected by a magnetic particle inspection method if the equipment is available. 6. Visible penetrant-type developer, when applied to the surface of a part, will dry to a smooth, even, white coating. As the developer dries, bright red indications will appear where there are surface defects. If no red indications appear, there are no surface defects. 7. When conducting the fluorescent penetrant-type inspection, the defects will show up (under black light) as a brilliant yellow-green color and the sound areas will appear deep blue-violet. 8. It is possible to examine an indication of a defect and to determine its cause as well as its extent. Such an appraisal can be made if something is known about the manufacturing processes to which the part has been subjected. The size of the indication, or accumulation of penetrant, will show the extent of the defect and the brilliance will be a measure of its depth. Deep cracks will hold more penetrant and will be broader and more brilliant. Very fine openings can hold only small amounts of penetrants and will appear as fine lines. Issue No. 0 ET-PP04.1 Page 31 of 148  Ethiopian Aviation Academy Aviation Maintenance Revision No. 0 Training March 2020 ET-PP04 M01: Aircraft Engine Inspection, Maintenance, Operation and Troubleshooting False Indications With the penetrant inspection, there are no false indications in the sense that they occur in the magnetic particle inspection. There are, however, two conditions which may create accumulations of penetrant that are sometimes confused with true surface cracks and discontinuities. The first condition involves indications caused by poor washing. If all the surface penetrant is not removed in the washing or rinsing operation following the penetrant dwell time, the unremoved penetrant will be visible. Evidences of incomplete washing are usually easy to identify since the penetrant is in broad areas rather than in the sharp patterns found with true indications. When accumulations of unwashed penetrant are found on a part, the part should be completely reprocessed. Degreasing is recommended for removal of all traces of the penetrant. False indications may also be created where parts press fit to each other. If a wheel is press fit onto a shaft, penetrant will show an indication at the fit line. This is perfectly normal since the two parts are not meant to be welded together. Indications of this type are easy to identify since they are regular in form and shape. Figure 1-13 Liquid penetrant inspection method Issue No. 0 ET-PP04.1 Page 32 of 148  Ethiopian Aviation Academy Aviation Maintenance Revision No. 0 Training March 2020 ET-PP04 M01: Aircraft Engine Inspection, Maintenance, Operation and Troubleshooting I. X-ray X-rays can penetrate material and disclose discontinuities through the metal or non-metal components, making it an excellent inspection process when needed to determine the structural integrity of an engine component. The penetrating radiation is projected through the part to be inspected and produces an invisible or latent image in the film. When processed, the film becomes a radiograph, or shadow picture, of the object. This inspection medium, as a portable unit, provides a fast and reliable means for checking the integrity of engine components. X and gamma radiations, because of their unique ability to penetrate material and disclose discontinuities, have been applied to the radiographic (x-ray) inspection of metal fabrications and nonmetallic products. The penetrating radiation is projected through the part to be inspected and produces an invisible or latent image in the film. When processed, the film becomes a radiograph or shadow picture of the object. This inspection medium and portable unit provides a fast and reliable means for checking the integrity of airframe structures and engines. Figure 1-14 Radiograph. Radiographic inspection techniques are used to locate defects or flaws in airframe structures or engines with little or no disassembly. This is in marked contrast to other types of nondestructive testing which usually require removal, disassembly, and stripping of paint from the suspected part before it can be inspected. Due to the radiation risks associated with x-ray, extensive training is required to become a qualified radiographer. Only qualified radiographers are allowed to operate the x-ray units. Three major steps in the x-ray process discussed in subsequent paragraphs are: (1) exposure to radiation, including preparation, (2) processing of film, and (3) interpretation of the radiograph. Issue No. 0 ET-PP04.1 Page 33 of 148  Ethiopian Aviation Academy Aviation Maintenance Revision No. 0 Training March 2020 ET-PP04 M01: Aircraft Engine Inspection, Maintenance, Operation and Troubleshooting Preparation and Exposure The factors of radiographic exposure are so interdependent that it is necessary to consider all factors for any particular radiographic exposure. These factors include but are not limited to the following: Material thickness and density Shape and size of the object Type of defect to be detected Characteristics of x-ray machine used The exposure distance The exposure angle Film characteristics Types of intensifying screen, if used Knowledge of the x-ray unit’s capabilities should form a background for the other exposure factors. In addition to the unit rating in kilo voltage, the size, portability, ease of manipulation, and exposure particulars of the available equipment should be thoroughly understood. Previous experience on similar objects is also very helpful in the determination of the overall exposure techniques. A log or record of previous exposures will provide specific data as a guide for future radiographs. Film Processing After exposure to x-rays, the latent image on the film is made permanently visible by processing it successively through a developer chemical solution, an acid bath, and a fixing bath, followed by clear water wash. Radiographic Interpretation From the standpoint of quality assurance, radiographic interpretation is the most important phase of radiography. It is during this phase that an error in judgment can produce disastrous consequences. The efforts of the whole radiographic process are centered in this phase; the part or structure is either accepted or rejected. Conditions of unsoundness or other defects which are overlooked, not understood, or improperly interpreted can destroy the purpose and efforts of radiography and can jeopardize the structural integrity of an entire aircraft. A particular danger is the false sense of security imparted by the acceptance of a part or structure based on improper interpretation. As a first impression, radiographic interpretation may seem simple, but a closer analysis of the problem soon dispels this impression. The subject of interpretation is so varied and complex that it cannot be covered adequately in this type of document. Instead, this chapter gives only a brief review of basic requirements for radiographic interpretation, including some descriptions of common defects. Issue No. 0 ET-PP04.1 Page 34 of 148  Ethiopian Aviation Academy Aviation Maintenance Revision No. 0 Training March 2020 ET-PP04 M01: Aircraft Engine Inspection, Maintenance, Operation and Troubleshooting Experience has shown that, whenever possible, radiographic interpretation should be conducted close to the radiographic operation. When viewing radiographs, it is helpful to have access to the material being tested. The radiograph can thus be compared directly with the material being tested, and indications due to such things as surface condition or thickness variations can be immediately determined. The following paragraphs present several factors which must be considered when analyzing a radiograph. There are three basic categories of flaws: voids, inclusions, and dimensional irregularities. The last category, dimensional irregularities, is not pertinent to these discussions because its prime factor is one of degree, and radiography is not exact. Voids and inclusions may appear on the radiograph in a variety of forms ranging from a two-dimensional plane to a three- dimensional sphere. A crack, tear, or cold shut will most nearly resemble a two- dimensional plane, whereas a cavity will look like a three-dimensional sphere. Other types of flaws, such as shrink, oxide inclusions, porosity, and so forth, will fall somewhere between these two extremes of form. It is important to analyze the geometry of a flaw, especially for items such as the sharpness of terminal points. For example, in a crack-like flaw the terminal points appear much sharper in a sphere-like flaw, such as a gas cavity. Also, material strength may be adversely affected by flaw shape. A flaw having sharp points could establish a source of localized stress concentration. Spherical flaws affect material strength to a far lesser degree than do sharp pointed flaws. Specifications and reference standards usually stipulate that sharp pointed flaws, such as cracks, cold shuts, and so forth, are cause for rejection. Radiation Hazards Radiation from x-ray units and radioisotope sources is destructive to living tissue. It is universally recognized that in the use of such equipment, adequate protection must be provided. Personnel must keep outside the primary x-ray beam at all times. Radiation produces changes in all matter through which it passes. This is also true of living tissue. When radiation strikes the molecules of the body, the effect may be no more than to dislodge a few electrons, but an excess of these changes could cause irreparable harm. When a complex organism is exposed to radiation, the degree of damage, if any, depends on which of its body cells have been changed. Vital organs in the center of the body that are penetrated by radiation are likely to be harmed the most. The skin usually absorbs most of the radiation and reacts earliest to radiation. If the whole body is exposed to a very large dose of radiation, death could result. In general, the type and severity of the pathological effects of radiation depend on the amount of radiation received at one time and the percentage of the total body exposed. Smaller doses of radiation could cause blood and intestinal disorders in a short period of time. The more Issue No. 0 ET-PP04.1 Page 35 of 148  Ethiopian Aviation Academy Aviation Maintenance Revision No. 0 Training March 2020 ET-PP04 M01: Aircraft Engine Inspection, Maintenance, Operation and Troubleshooting delayed effects are leukemia and other cancers. Skin damage and loss of hair are also possible results of exposure to radiation. Safety precaution for radiation hazards  Radiation from x-ray units and radioisotope sources is destructive to living tissue.  It is universally recognized that in the use of such equipment, adequate protection must be provided.  Personnel must keep outside the primary x-ray beam at all times.  Film badges and radiation survey meters are necessary to hold them for personnel conducting the task Figure 1-15 Radiographic inspection II. Eddy Current Inspection Eddy currents are composed of free electrons under the influence of an induced electromagnetic field that are made to drift through metal. Different meter readings are seen when the same metal is in different hardness states. Readings in the affected area are compared with identical materials in known unaffected areas for comparison. A difference in readings indicates a difference in the hardness state of the affected area. Eddy current inspection can frequently be performed without removing the surface coatings, such as Issue No. 0 ET-PP04.1 Page 36 of 148  Ethiopian Aviation Academy Aviation Maintenance Revision No. 0 Training March 2020 ET-PP04 M01: Aircraft Engine Inspection, Maintenance, Operation and Troubleshooting primer, paint, and anodized films. It can be effective in detecting surface and subsurface corrosion, pots, and heat treat condition. Eddy currents are created through a process called electromagnetic induction. When alternating current is applied to the conductor, such as copper wire, a magnetic field develops in and around the conductor. This magnetic field expands as the alternating current rises to maximum and collapses as the current is reduced to zero. If another electrical conductor is brought into the close proximity to this changing magnetic field, current will be induced in this second conductor. Eddy currents are induced electrical currents that flow in a circular path. They get their name from “eddies” that are formed when a liquid or gas flows in a circular path around obstacles when conditions are right. In order to generate eddy currents for an inspection, a "probe" is used. Inside the probe is a length of electrical conductor material which is formed into a coil. One of the major advantages of eddy current as an NDT tool is the variety of inspections and measurements that can be performed. In the proper circumstances, eddy currents can be used for: Crack detection Material thickness measurements Coating thickness measurements Conductivity measurements for: o Material identification o Heat damage detection o Case depth determination o Heat treatment monitoring Some of the advantages of eddy current inspection include: Sensitive to small cracks and other defects Detects surface and near surface defects Inspection gives immediate results Equipment is very portable Method can be used for much more than flaw detection Minimum part preparation is required Test probe does not need to contact the part Inspects complex shapes and sizes of conductive materials Some of the limitations of eddy current inspection include: Only conductive materials can be inspected Surface must be accessible to the probe Skill and training required is more extensive than other techniques Issue No. 0 ET-PP04.1 Page 37 of 148  Ethiopian Aviation Academy Aviation Maintenance Revision No. 0 Training March 2020 ET-PP04 M01: Aircraft Engine Inspection, Maintenance, Operation and Troubleshooting Surface finish and and roughness may interfere Reference standards needed for setup Depth of penetration is limited Flaws such as delaminations that lie parallel to the probe coil winding and probe scan direction are undetectable Figure 1-16 Eddy current inspection Issue No. 0 ET-PP04.1 Page 38 of 148  Ethiopian Aviation Academy Aviation Maintenance Revision No. 0 Training March 2020 ET-PP04 M01: Aircraft Engine Inspection, Maintenance, Operation and Troubleshooting Figure 1-17 Eddy current inspection III. Ultrasonic Inspection Ultrasonic detection equipment makes it possible to locate defects in all types of materials. There are three basic ultrasonic inspection methods: 1. Pulse-echo 2. Through transmission 3. Resonance Issue No. 0 ET-PP04.1 Page 39 of 148  Ethiopian Aviation Academy Aviation Maintenance Revision No. 0 Training March 2020 ET-PP04 M01: Aircraft Engine Inspection, Maintenance, Operation and Troubleshooting Pulse-Echo Flaws are detected by measuring the amplitude of signals reflected and the time required for these signals to travel between specific surfaces and the discontinuity. Through Transmission Through transmission inspection uses two transducers, one to generate the pulse and another placed on the opposite surface to receive it. A disruption in the sound path indicates a flaw and is displayed on the instrument screen. Through transmission is less sensitive to small defects than the pulse- echo method. Resonance This system differs from the pulse-echo method, in that the frequency of transmission may be continuously varied. The resonance method is principally used for thickness measurements when the two sides of the material being tested are smooth and parallel, and the backside is inaccessible. The point at which the frequency matches the resonance point of the material being tested is the thickness determining factor. Basic Principles of Ultrasonic Testing Ultrasonic Testing (UT) uses high frequency sound energy to conduct examinations and make measurements. Ultrasonic inspection can be used for flaw detection/evaluation, dimensional measurements, material characterization, and more. To illustrate the general inspection principle, a typical pulse/echo inspection configuration as illustrated below will be used. A typical UT inspection system consists of several functional units, such as the pulser/receiver, transducer, and display devices. A pulser/receiver is an electronic device that can produce high voltage electrical pulses. Driven by the pulser, the transducer generates high frequency ultrasonic energy. The sound energy is introduced and propagates through the materials in the form of waves. When there is a discontinuity (such as a crack) in the wave path, part of the energy will be reflected back from the flaw surface. The reflected wave signal is transformed into an electrical signal by the transducer and is displayed on a screen. In the applet below, the reflected signal strength is displayed versus the time from signal generation to when a echo was received. Signal tra