EASA Part 66 Module 7: Maintenance Practices 1. Safety Precautions-Aircraft and Workshop
Aspects of safe working practices including precautions to take when working with electricity, gases especially oxygen, oils and chemicals. Also, instruction in the remedial action to be taken in the event of a fire or another accident with one or more of these hazards including knowledge on extinguishing agents.
2. Workshop Practices
Care of tools, control of tools, use of workshop materials; Dimensions, allowances and tolerances, standards of workmanship; Calibration of tools and equipment, calibration standards.
3. Tools
Common hand tool types; Common power tool types; Operation and use of precision measuring tools; Lubrication equipment and methods. Operation, function and use of electrical general test equipment;
4. Avionic General Test Equipment
Operation, function and use of avionic general test equipment.
5. Engineering Drawings, Diagrams and Standards
Drawing types and diagrams, their symbols, dimensions, tolerances and projections; Identifying title block information; Microfilm, microfiche and computerized presentations; Specification 100 of the Air Transport Association (ATA) of America; Aeronautical and other applicable standards including ISO, AN, MS, NAS and MIL; Wiring diagrams and schematic diagrams.
6. Fits and Clearances
Drill sizes for bolt holes, classes of fits; Common system of fits and clearances; Schedule of fits and clearances for aircraft and engines; Limits for bow, twist and wear; Standard methods for checking shafts, bearings and other parts.
7. Electrical Cables and Connectors
Continuity, insulation and bonding techniques and testing; Use of crimp tools: hand and hydraulic operated; Testing of crimp joints; Connector pin removal and insertion; Co-axial cables: testing and installation precautions; Wiring protection techniques: Cable looming and loom support, cable clamps, protective sleeving techniques including heat shrink wrapping, shielding.
8. Riveting
Riveted joints, rivet spacing and pitch; Tools used for riveting and dimpling; Inspection of riveted joints.
9. Pipes and Hoses
Bending and belling/flaring aircraft pipes; Inspection and testing of aircraft pipes and hoses; Installation and clamping of pipes.
10. Springs
Inspection and testing of springs.
11. Bearings
Testing, cleaning and inspection of bearings; Lubrication requirements of bearings; Defects in bearings and their causes.
12. Transmissions
Inspection of gears, backlash; Inspection of belts and pulleys, chains and sprockets; Inspection of screw jacks, lever devices, push-pull rod systems.
13. Control Cables
Swaging of end fittings; Inspection and testing of control cables; Bowden cables; aircraft flexible control systems.
14. Material handling 14.1 Sheet Metal
Marking out and calculation of bend allowance; sheet metal working, including bending and forming; Inspection of sheet metal work. 14.2 Composite and non-metallic
Bonding practices; Environmental conditions Inspection methods
15. Welding, Brazing, Soldering and Bonding 15.1 Soldering methods; inspection of soldered joints. 15.2 Welding and brazing methods;
Inspection of welded and brazed joints; Bonding methods and inspection of bonded joints.
16. Aircraft Weight and Balance 16.1 Centre of Gravity/Balance limits calculation: use of relevant documents; 16.2 Preparation of aircraft for weighing;
Aircraft weighing;
17. Aircraft Handling and Storage
Aircraft taxiing/towing and associated safety precautions; Aircraft jacking, chocking, securing and associated safety precautions; Aircraft storage methods; Refueling/defueling procedures; De-icing/anti-icing procedures; Electrical, hydraulic and pneumatic ground supplies. Effects of environmental conditions on aircraft handling and operation.
18. Disassembly, Inspection, Repair and Assembly Techniques 18.1 Types of defects and visual inspection techniques;
Corrosion removal, assessment and re-protection. 18.2 General repair methods, Structural Repair Manual;
Ageing, fatigue and corrosion control programs; 18.3 Non-destructive inspection techniques including, penetrant, radiographic, eddy current, ultrasonic and borescope methods. 18.4 Disassembly and re-assembly techniques. 18.5 Trouble shooting techniques
19. Abnormal Events 19.1 Inspections following lightning strikes and HIRF penetration. 19.2 Inspections following abnormal events such as heavy landings and flight through turbulence.
20. Maintenance Procedures
Maintenance planning; Modification procedures; Stores procedures; Certification/release procedures; Interface with aircraft operation; Maintenance Inspection/Quality Control/Quality Assurance; Additional maintenance procedures; Control of life limited components.
1. Safety Precautions – Aircraft and Workshop Aspects of safe working practices including precautions to take when working with electricity, gases especially oxygen, oils and chemicals. Also, instruction in the remedial action to be taken in the event of a fire or another accident with one or more of these hazards including knowledge on extinguishing agents Negative Effects of unsafe Maintenance System 1. increase operating costs 2. reduce efficiency and effectiveness 3. additional cost for the compensation of health insurances and training of employees
Aviation Maintenance Technicians Model Code of Conduct Main Responsibilities •
make safety their highest priority,
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seek excellence in workmanship,
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develop and exercise good judgment, and apply sound principles of technical decision -making,
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recognize and manage risks effectively,
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adhere to prudent operating practices and personal operating parameters (e.g., tolerances, limitations, and other human factors),
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advance professionalism,
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act with responsibility and courtesy,
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adhere to applicable laws and regulations, and
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comply with training and performance requirements.
Sub Responsibilities •
maintain a safe work place environment,
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manage risk and avoid unnecessary risk to aircraft occupants, people and property on the surface, and people in other aircraft,
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brief team members on maintenance procedures and inform them of any significant or unusual risk associated with the task,
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avoid operations and behavior that may alarm or disturb aircraft occupants, people on the surface, or other third-parties.
PERSONAL MINIMUM CHECKLIST -
a checklist to ensure that the job done is right.
Hazard - anything with the potential to cause harm. Types of Hazard: 1. FIRE 2. CHEMICAL 3. ELECTRICITY 4. MACHINES
HANDLING ELECTRICITY •
Must have a working knowledge of the principles of electricity, and a healthy respect for its capability to do both work and damage.
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Wearing or use of proper safety equipment.
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Avoid water at all times when working with electricity. Never touch or try repairing any electrical equipment or circuits with wet hands. It increases the conductivity of electric current.
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Never use equipment with frayed cords, damaged insulation or broken plugs.
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Always use insulated tools while working.
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Never try repairing energized equipment. Always check that it is de-energized first by using a tester.
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Always be observant of electrical hazards include exposed energized parts and unguarded electrical equipment
HANDLING HAZARDOUS CHEMICAL •
Wear proper equipment (gloves, respirator, face shield, chemical suit and goggles)
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Identify the chemical being used through its label
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Follow the safety guidelines when using the chemical on its MSDS *Material Safety Data Sheet
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Work must be done near emergency shower in case of contact on the eyes or skin.
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Segregate chemicals when disposing through the use of color code
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When accident occur refer immediately to its MSDS
NFPA – NATIONAL FIRE PROTECTION ASSOCIATION
NFPA HAZARD IDENTIFICATION
Personal Protective Equipment Consists of a glove, suit, goggle and face mask that is mainly used to protect the mechanic from hazards if contact through the body has occured. HANDLING FIRE Personal Protective Equipment •
Work in a secured location with a fire extinguisher nearby.
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Wear your PPE *PERSONAL PROTECTIVE EQUIPMENT
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Ensure the material that will be subjected to the fire is safe and stored properly
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Avoid smoking near flammable areas
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Flammable materials should be out of reach
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Extinguish immediately the fire when not in use
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Never overload circuits or extension cords on the shop
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IF ALL ELSE FAILS SOUND THE ALARM
PROPER WAYY OF EXTINGUISHING THE FIRE P – Pull the pin and hold the extinguisher with the nozzle pointing away from you. A – Aim low. Point the extinguisher at the base of the fire. S – Squeeze the lever slowly and evenly. S – Sweep the nozzle from side to side
2. Workshop Practices An understanding of aircraft workshop principles and practice is a fundamental requirement for those aircraft engineering technicians or engineers, irrespective of their chosen specialization. This presentation will give learners an understanding of the safe working practices associated with aircraft workshop activities and the care, control and safe use of aircraft workshop tools and equipment. Learners will develop the skills needed to safely carry out tasks associated with aircraft Tools and Equipment. They will also gain the skills necessary to read and interpret engineering diagrams and drawings.
Care of Tools - Good tools can be quite an investment, but if you keeping your tools properly stored, cleaned, and maintained it will maintain its effectiveness. - Tools and equipment on the aircraft undergo rigorous handling. These tools are exposed to large amounts of dirt and abuse. Proper maintenance of tools and equipment is critical to preserving them for future use. Failure to maintain the tools properly results in unnecessary expense.
Example
Clean the tools and equipment after each day's work. While a thorough cleaning is not required each day, a general wipe-down and removal of the heaviest co dirt is key to extending the life of the tools.
Keep air lines and electrical cords protected from heavy foot-traffic and vehicles or other motorized machinery, can easily cut or crush cords and hoses, preventing the tools from w orking properly, and creating potential electrical hazards. Cover the electrical cords with purpose-built ramps or casing.
Lubricate air tools and pneumatic equipment before each day's use. Condensation in the airline creates an environment for corrosion inside pneumatic tools. Coating the internal components of these tools with air-tool oil will displace the moisture and prevent tool corrosion.
Inspect and repair all equipment and tools at the completion of each job. Make all repairs to the equipment that are necessary for future construction work. This will prevent time being wasted repairing faulty equipment at future use.
Tool Control - Tool control is a method to quickly determine that all tools are accounted for at the end of a maintenance task. This can only be done if each tool has a specific place where it is stored that allows for quick identification if the tool is missing. There are several ways to do this - Tool control affects safety. Leaving a tool in an aircraft or engine is not just an inconvenience, it is a safety risk. Realizing this, most aircraft maintenance businesses enforce some sort of tool control procedures. They realize that establishing and enforcing a tool control program can provide numerous benefits, the foremost of which is safety.
Tool shadowing This involves specifying a specific space for each tool. It should be designed in such a way as to quickly determine if a tool is missing. A popular method is to use some type of foam product and cut out spots for each tool. In a toolroom environment, walls can be used with pegboard and hooks. The item is then outlined and shadowed.
Tool identification Some companies require employees permanently mark their tools for tool identification purposes. This provides a way to quickly identify who a tool belongs to when it is found. Tools can be marked using a vibra-peen tool. Some other marking methods such as permanent marker may not be very effective in a hangar environment.
Marking tools serves two purposes. First of all, it ensures that if a tool is found it is returned to the owner. Second, it helps assure compliance with missing tool reporting. It makes employees become more vigilant in reporting missing tools vs. just going to the closest tool truck or store to buy a replacement.
Tool inventory A tool inventory should be accomplished on a regular basis so that any missing tools can quickly be identified and searched for before they affect the safety of an aircraft. This can be done after each work task or at least once a day. Many companies choose to do it at the beginning and end of each shift.
Tool inspection An important part of tool control that can easily be overlooked is tool inspection. Tools should be inspected before and after each use to ensure they are in proper working order and no parts are missing. If this is not done, it can be easy for a piece of a tool to be left behind in a work area. David Smith, director of quality assurance, U.S. maintenance for Jet Aviation, discusses his company’s tool inspection requirement. “We require mechanics to inspect all tools and equipment before and after each use. This is written in our standard operating procedures manual. This policy helps ensure that no pieces from a broken tool are left in an aircraft or engine after maintenance is performed.”
Missing tool reporting An important part of any tool control program is a process for missing tool reporting. In order to achieve the goal of accounting for all tools to ensure a safe product for the customer, a culture must be present that encourages employees to report any missing tool. This procedure should be clear as to how often tools need to be inventoried, how the employee should report a missing tool, and the steps to be taken once a missing tool is reported. An important part of this is the person who has the authority to release the aircraft in the event a missing tool is not found.
RFID Tool Control 3M has introduced a tool control solution using radio frequency identification (RFID) to the marketplace. This tool tracking solution was announced at the NBAA convention this past November. The RFID tool tracking system includes tracking software, RFID tags with protective labels, and RFID handheld readers. The system is currently being installed at The Nordam Group’s Tulsa, Oklahoma, facility. Dr. Sandra Tokach, general manager for 3M’s Aerospace and Aircraft Maintenance Division, says, “For aerospace manufacturers and MRO providers alike, systems that use RFID will bring much-needed efficiencies across a wide array of processes; in NORDAM’s case, for tool tracking.”
API API recently introduced Electronic Supply Program (ESP) to the market. This is an Internet-based software program that uses and allows customers to automate inventory control and parts replenishment. As an added feature, ESP also has a tool control module. This module allows tools to be tracked according to a customer’s needs — whether it is by work order, N-number, or employee number. It can also track tool calibration requirements and send email alerts when a tool is approaching a calibration due date.
In the end, each company must select a tool control program that works best for its needs. Whether it is a matter of shadowing toolboxes or an investment in an automated tool control system, keeping track of tools is a safety issue that shouldn’t be ignored.
Dimensions, Allowance, and Tolerance Dimensions The dimension of an object is a topological measure of the size of its covering properties. Roughly speaking, it is the number of coordinates needed to specify a point on the object. For example, a rectangle is two-dimensional, while a cube is three-dimensional. The dimension of an object is sometimes also called its "dimensionality." Allowance An allowance is a planned deviation between an actual dimension and a nominal or theoretical dimension, or between an intermediate-stage dimension and an intended final dimension. The unifying abstract concept is that a certain amount of difference allows for some known factor of compensation or interference. An allowance, which is a planned deviation from an ideal, is contrasted with a tolerance, which accounts for expected but unplanned deviations. Tolerance Dimensions, properties, or conditions may vary within certain practical limits without significantly affecting functioning of equipment or a process. Tolerances are specified to allow reasonable leeway for imperfections and inherent variability without compromising performance. A variation beyond the tolerance (for example, a temperature that's too hot or too cold) is said to be noncompliant, rejected, or exceeding the tolerance (regardless of if this breach was of the lower or the upper bound). If the tolerance is set too restrictive, resulting in most objects run by it being rejected, it is said to be intolerant. Example: All measuring devices and test equipment will: 1. Meet any requirements published by the manufacturer of the measuring device with respect to accuracy. 2. Meet any calibration requirements that are published by the tool manufacturer. 3. Be inspected before use. 4. Any tool suspected of inaccuracy or damage, despite meeting any other requirements, will be taken out of service, repaired and calibrated, or replaced. 5. Where calibration is required, be calibrated in accordance with a national standard. 6. Each precision tool will have a calibration sticker attached. Records relating to the calibration of the tool will be retained on file. All tools and equipment requiring calibration will be listed on a status board in the organization office. The status board will contain:
Name of tool Serial number of tool Date last calibrated Date next calibration due
3. Tools Common hand tool types Pounding Tools Punches Holding Tools Cutting Tools Turning Tools Inspection Tools Common power tool types Screwdriver Drill Riveting gun
Precision measuring tools Vernier Micrometer Tape measure Multimeter
Lubrication equipment and methods. •
Lubrication needle nozzles - in aircrafts many grease points are of flush type, countersunk in the construction. These flush type grease points can’t be lubricated with a standard hydraulic coupler, and a special lubrication needle nozzle is needed.
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Extension tubes - used to connect a needle nozzles or hydraulic couplers to a grease gun. The extensions are produced from heavy-wall steel tubing.
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Extension hoses - used to create a flexible connection between a needle , nozzles or hydraulic couplers to a grease gun.
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Hydraulic couplers - used to transmit rotating mechanical power. It has been used in automobile transmissions as an alternative to a mechanical clutch.
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Grease gun - a device for pumping grease under pressure to a particular point.
4. Avionic General Test Equipment Operation, function and use of avionic general test equipment. BASIC AVIONICS TEST EQUIPMENT POWER SUPPLIES Power for an avionics system is typically 14 or 28 volts DC and, for large aircraft, 400 Hz AC. When the avionics are removed from the aircraft, the appropriate bench supply is required. A power supply of about 20 amperes at 14 volts and 10 amperes at 28 volts should cover most avionics systems. One power hungry system is the HF transceiver. Many transmitters operate at more than 100 watts output, which requires about twice that as input. A power supply of about 20 amperes at 14 volts and 10 amperes at 28 volts should cover most avionics systems. One power hungry system is the HF transceiver. Many transmitters operate at more than 100 watts output, which requires about twice that as input. 3 COMMONLY USED AVIONIC TEST EQUIPMENT 1. SOUND – AUDIO MODULATOR 2. NAVIGATION – ADF ANTENNA TESTER 3. AUTOPILOT – TEST PANELS AUDIO MODULATOR •
The first and most widespread use for the audio generator is to modulate radio transmitters. Another application is troubleshooting and testing audio panels and intercoms. When an audio generator provides signals for transmitters and audio equipment, the te st is called a single tone test and is not ideal for transmitter testing. This is particularly the case with SSB (single sideband), where a single tone test is virtually worthless. To effectively measure an SSB transmitter, two audio frequency tones within the speech range of 300 to 3000 Hz are applied. The tones are typically equal in amplitude and not harmonically related. The single tone test, although not ideal, is acceptable for routine amplitude modulation testing.
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No unusual features are needed for an audio source for voice transmitter testing because the transmitters are not high-fidelity and operate over a narrow range of audio frequencies. The ideal source would be two inexpensive audio frequency sine generators. The two are combined with a simple resistive network and function as a two-tone source, or one generator as a single-tone source. Shops that never repair SSB transceivers can survive with only one audio generator.
ADF ANTENNA TESTER •
The Automatic Direction Finder uses a directional antenna as an integral part of the system. Without the antenna, the ADF cannot function. To operate the ADF in the shop, therefore, a signal simulator and ADF antenna are required. To simulate a received ADF signal, the antenna is placed in a known magnetic field, where the field is a signal in space with known magnitude and direction.
The ADF signal is generated by creating a magnetic field within a large aluminum box. The carrier frequency is provided by a signal generator. An ADF antenna matching the receiver to be serviced is placed within the ADF simulator and connected to the receiver. •
A repair shop may have several ADF antennas for placing within the ADF simulator so several models may be serviced. Most failures, however, occur within the receiver rather than the antenna. The antenna contains few components although it is vulnerable to environmental damage at its location. Unless the antenna is suspected of being faulty, most ADF problems involve removing only the receiver and leaving the antenna in place. If the receiver is operational, the antenna is removed from the aircraft and placed in the signal simulator.
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ADF receivers have two antennas: loop and sense. Most modern receivers locate both loop and sense antennas inside a common assembly. ADF signal simulators require a mounting plate for the specific antenna and an adapter box to couple the signal generator to the sense antenna with the correct amplitude and phase relationship.
TEST PANELS •
Once an avionics unit has been removed from an aircraft, it cannot operate unless connections are made to antennas, speakers, power supplies, indicators, microphones, etc. These items are provided by a test panel and test harness. The panel provides hardware such as speakers, volume control, frequency setting, etc., while a wire harness makes connection to the unit under test (UUT).
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A test panel generally covers a number of products but not all. As an example, a panel will handle one or more brands of navigation receiver or communications transceivers.
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Another test panel may handle DMEs and transponders or just DMEs or only transponders. Each model has a unique harness for signal connections via a mating connector.
5. Engineering Drawings, Diagrams and Standards Types of Technical Drawings The two types of technical drawings are based on graphical projection. This is used to create an image of a three-dimensional object onto a two-dimensional surface: Two-dimensional representation -
Uses orthographic projection to create an image where only two of the three dimensions of the object are seen.
Three-dimensional representation -
In a three-dimensional representation, also referred to as a pictorial, all three dimensions of an object are visible.
Engineering Drawing An engineering drawing, a type of technical drawing, is used to fully and clearly define requirements for engineered items.
Engineering drawing (the activity) produces engineering drawings (the documents). More than just the drawing of pictures, it is also a language—a graphical language that communicates ideas and information from one mind to another. Most especially, it communicates all needed information from the engineer who designed a part to the workers who will make it.
Systems of dimensioning and Tolerancing Almost all engineering drawings (except perhaps reference-only views or initial sketches) communicate not only geometry (shape and location) but also dimensions and tolerances for those characteristics. Several systems of dimensioning and tolerancing have evolved. The simplest dimensioning system just specifies distances between points (such as an object's length or width, or hole center locations). Since the advent of well-developed interchangeable manufacture, these distances have been accompanied by tolerances of the plus-or-minus or min-and-max-limit types. Coordinate dimensioning involves defining all points, lines, planes, and profiles in terms of Cartesian coordinates, with a common origin. Coordinate dimensioning was the sole best option until the post-World War II era saw the development of geometric dimensioning and tolerancing (GD&T), which departs from the limitations of coordinate dimensioning (e.g., rectangular-only tolerance zones, tolerance stacking) to allow the most logical tolerancing of both geometry and dimensions (that is, both form [shapes/locations] and sizes). Dimensions The dimension of an object is a topological measure of the size of its covering properties. Roughly speaking, it is the number of coordinates needed to specify a point on the object. For example, a rectangle is two-dimensional, while a cube is three-dimensional. The dimension of an object is sometimes also called its "dimensionality." Tolerance Dimensions, properties, or conditions may vary within certain practical limits without significantly affecting functioning of equipment or a process. Tolerances are specified to allow reasonable leeway for imperfections and inherent variability without compromising performance. A variation beyond the tolerance (for example, a temperature that's too hot or too cold) is said to be noncompliant, rejected, or exceeding the tolerance (regardless of if this breach was of the lower or the upper bound). If the tolerance is set too restrictive, resulting in most objects run by it being rejected, it is said to be intolerant.
Three basic tolerances Limit Dimension Are two dimensional values stacked on top of each other? The dimensions show the largest and smallest values allowed anything in between these values is acceptable. Unilateral Tolerance A unilateral tolerance exists when a target dimension is given along with a tolerance that allows variation to occur in only one direction.
Bilateral Tolerance A bilateral tolerance exists if the variation from a target dimension is shown occurring in both the positive and negative directions.
Systems of dimensioning and tolerancing In most cases, a single view is not sufficient to show all necessary features, and several views are used. Types of views include the following:
Orthographic projection The orthographic projection shows the object as it looks from the front, right, left, top, bottom, or back, and are typically positioned relative to each other according to the rules of either first-angle or third-angle projection. The origin and vector direction of the projectors (also called projection lines).
Auxiliary projection An auxiliary view is an orthographic view that is projected into any plane other than one of the six principal views. These views are typically used when an object contains some sort of inclined plane. Using the auxiliary view allows for that inclined plane (and any other significant features) to be projected in their true size and shape. The true size and shape of any feature in an engineering drawing can only be known when the Line of Sight (LOS) is perpendicular to the plane being referenced. It is shown like a threedimensional object.
Isometric projection The isometric projection show the object from angles in which the scales along each axis of the object are equal. Isometric projection corresponds to rotation of the object by ± 45° about the vertical axis, followed by rotation of approximately ± 35.264° [= arcsin(tan(30°))] about the horizontal axis starting from an orthographic projection view. "Isometric" comes from the Greek for "same measure". One of the things that makes isometric drawings so attractive is the ease with which 60 degree angles can be constructed with only a compass and straightedge.
Isometric projection is a type of axonometric projection. The other two types of axonometric projection are: Oblique projection An oblique projection is a simple type of graphical projection used for producing pictorial, twodimensional images of three-dimensional objects: It projects an image by intersecting parallel rays (projectors) from the three-dimensional source object with the drawing surface (projection plan). In both oblique projection and orthographic projection, parallel lines of the source object produce parallel lines in the projected image.
Perspective Perspective is an approximate representation on a flat surface, of an image as it is perceived by the eye. The two most characteristic features of perspective are that objects are drawn:
Smaller as their distance from the observer increases Foreshortened: the size of an object's dimensions along the line of sight are relatively shorter than dimensions across the line of sight.
Section Views Projected views (either Auxiliary or Orthographic) which show a cross section of the source object along the specified cut plane. These views are commonly used to show internal features with more clarity than may be available using regular projections or hidden lines. In assembly drawings, hardware components (e.g. nuts, screws, washers) are typically not sectioned.
Identifying title block information; -
The title block (T/B, TB) is an area of the drawing that conveys header-type information about the drawing, such as:
Drawing title (hence the name "title block")
Drawing number
Part number(s)
Name of the design activity (corporation, government agency, etc.)
Identifying code of the design activity (such as a CAGE code)
Address of the design activity (such as city, state/province, country)
Measurement units of the drawing (for example, inches, millimeters)
Default tolerances for dimension callouts where no tolerance is specified
Boilerplate callouts of general specs
Intellectual property rights warning
Traditional locations for the title block are the bottom right (most commonly) or the top right or center.
Specification 100 of the Air Transport Association (ATA) of America; ATA Spec 100: Manufacturers' Technical Data The then Air Transport Association released the newest version of ATA Spec 100 in 1999. According to the A4A website, this information will not be revised and has been combined with ATA Spec 2100 to produce the ATA iSpec 2200: Information Standards for Aviation Maintenance manual. This specification defines a widely used numbering scheme for aircraft parts and the appearance of printed aircraft maintenance information. The Federal Aviation Administration's JASC (Joint Aircraft System/Component) code table provides a modified version of ATA Spec 100. ATA Spec 100 contains format and content guidelines for technical manuals written by aviation manufacturers and suppliers, and is used by airlines and other segments of the industry in the maintenance of their respective products. This document provides the industrywide standard for aircraft systems numbering, often referred to as the ATA system or ATA chapter numbers. The format and content guidelines define the data prepared as conventional printed documentation. In 2000 ATA Spec 100 and ATA Spec 2100 were incorporated into ATA iSpec 2200: Information Standards for Aviation Maintenance. ATA Spec 100 and Spec 2100 will not be updated beyond the 1999 revision level.
Aeronautical and other applicable standards Example: ISO The International Organization for Standardization, known as ISO, is an international standard-setting body composed of representatives from various national standards organizations. ANSI The American National Standards Institute is a private non-profit organization that oversees the development of voluntary consensus standards for products, services, processes, systems, and personnel in the United States.[3] The organization also coordinates U.S. standards with international standards so that American products can be used worldwide. For example, standards ensure that people who own cameras can find the film they need for that camera anywhere around the globe. MIL A United States defense standard, often called a Military Standard, "MIL-STD", "MIL-SPEC", or (informally) "MilSpecs", is used to help achieve standardization objectives by the U.S. Department of Defense. Standardization is beneficial in achieving interoperability, ensuring products meet certain requirements, commonality, reliability, total cost of ownership, compatibility with logistics systems, and similar defenserelated objectives. Defense standards are also used by other non-defense government organizations, technical organizations, and industry. This article discusses definitions, history, and usage of defense standards. Related documents, such as defense handbooks and defense specifications, are also addressed.
Wiring diagrams and schematic diagrams. Wiring diagrams A wiring diagram is a simplified conventional pictorial representation of an electrical circuit. It shows the components of the circuit as simplified shapes, and the power and signal connections between the devices. A wiring diagram usually gives more information about the relative position and arrangement of devices and terminals on the devices, to help in building the device. This is unlike a schematic diagram, where the arrangement of the components' interconnections on the diagram usually does not correspond to the components' physical locations in the finished device. A pictorial diagram would show more detail of the physical appearance, whereas a wiring diagram uses a more symbolic notation to emphasize interconnections over physical appearance. A wiring diagram is used to troubleshoot problems and to make sure that all the connections have been made and that everything is present.
Schematic diagrams A schematic, or schematic diagram, is a representation of the elements of a system using abstract, graphic symbols rather than realistic pictures. A schematic usually omits all details that are not relevant to the information the schematic is intended to convey, and may add unrealistic elements that aid comprehension. For example, a subway map intended for riders may represent a subway station with a dot; the dot doesn't resemble the actual station at all but gives the viewer information without unnecessary visual clutter. A schematic diagram of a chemical process uses symbols to represent the vessels, piping, valves, pumps, and other equipment of the system, emphasizing their interconnection paths and suppressing physical details. In an electronic circuit diagram, the layout of the symbols may not resemble the layout in the physical circuit. In the schematic diagram, the symbolic elements are arranged to be more easily interpreted by the viewer.
6. Fits and Clearances Tolerance Dimensioning
Tolerance is the total amount that a specific dimension is permitted to vary; It is the difference between the maximum and the minimum limits for the dimension. For Example a dimension given as 1.625 ± .002 means that the manufactured part may be 1.627” or 1.623”, or anywhere between these limit dimensions.
The Tolerance is 0.001” for the Hole as well as for the Shaft
Size Designations
Nominal Size: It is the designation used for general identification and is usually expressed in common fractions. For Ex. In the previous figure, the nominal size of both hole and shaft, which is 11/4” would be 1.25” in a decimal system of dimensioning. Basic Size or Basic dimension: It is the theoretical size from which limits of size are derived by the application of allowances and tolerances. Actual Size: is the measured size of the finished part. Allowance: is the minimum clearance space (or maximum interference) intended between the maximum material conditions of mating parts.
Fits between Mating Parts
Fit is the general term used to signify the range of tightness or looseness that may result from the application of a specific combination of allowances and tolerances in mating parts.
There are four types of fits between parts 1. Clearance Fit: an internal member fits in an external member (as a shaft in a hole) and always leaves a space or clearance between the parts.
Minimum air space is 0.002”. This is the allowance and is always positive in a clearance fit 2. Interference Fit: The internal member is larger than the external member such that there is always an actual interference of material. The smallest shaft is 1.2513” and the largest hole is 1.2506”, so that there is an actual interference of metal amounting to at least 0.0007”. Under maximum material conditions the interference would be 0.0019”. This interference is the allowance, and in an interference fit it is always negative.
3. Transition Fit: may result in either a clearance or interference condition. In the figure below, the smallest shaft 1.2503” will fit in the largest hole 1.2506”, with 0.003” to spare. But the largest shaft, 1.2509” will have to be forced into the smallest hole, 1.2500” with an interference of metal of 0.009”.
4. Line Fit: the limits of size are so specified that a clearance or surface contact may result when mating parts are assembled. Basic Hole System
Minimum hole is taken as the basic size, an allowance is assigned, and tolerances are applied on both sides of and away from this allowance.
1. The minimum size of the hole 0.500” is taken as the basic size. 2. An allowance of 0.002” is decided on and subtracted from the basic hole size, making the maximum shaft as 0.498”. 3. Tolerances of 0.002” and 0.003” respectively are applied to the hole and shaft to obtain the maximum hole of 0.502” and the minimum shaft of 0.495”.
Minimum clearance: 0.500”-0.498” = 0.002” Maximum clearance: 0.502” – 0.495” = 0.007”
Basic Shaft System
Maximum shaft is taken as the basic size, an allowance is assigned, and tolerances are applied on both sides of and away from this allowance.
1. The maximum size of the shaft 0.500” is taken as the basic size. 2. An allowance of 0.002” is decided on and added to the basic shaft size, making the minimum hole as 0.502”. 3. Tolerances of 0.003” and 0.001” respectively are applied to the hole and shaft to obtain the maximum hole of 0.505” and the minimum shaft of 0.499”.
Minimum clearance: 0.502”-0.500” = 0.002” Maximum clearance: 0.505” – 0.499” = 0.006”
Specifications of Tolerances 1. Limit Dimensioning- The high limit is placed above the low limit.
In single-line note form, the low limit precedes the high limit separated by a dash
2. Plus-or-minus Dimensioning
Unilateral Tolerance
Bilateral Tolerance
Basic Size: is the size from which limits or deviations are assigned. Basic sizes, usually diameters, should be selected from a table of preferred sizes. Deviation: is the difference between the basic size and the hole or shaft size. Upper Deviation: is the difference between the basic size and the permitted maximum size of the part. Lower Deviation: is the difference between the basic size and the minimum permitted size of the part. Fundamental Deviation: is the deviation closest to the basic size. Tolerance: is the difference between the permitted minimum and maximum sizes of a part.
7. Electrical Cables and Connectors Continuity, insulation and bonding techniques and testing; Electrical Continuity. Metal raceways, cables, boxes, fittings, cabinets, and enclosures for conductors must be metallically joined together to form a continuous, low-impedance fault current path capable of carrying any fault current likely to be imposed on it Continuity refers to being part of a complete or connected whole. In electrical applications, when an electrical circuit is capable of conducting current, it demonstrates electrical continuity. It is also said to be “closed,” because the circuit is complete. In the case of a light switch, for example, the circuit is closed and capable of conducting electricity when the switch is flipped to "on." The user can break the continuity by flipping the switch to "off," opening the circuit and rendering it incapable of conducting electricity. Electrical bonding is the practice of intentionally electrically connecting all exposed metallic items not designed to carry electricity in a room or building as protection from electric shock. If a failure of electrical insulation occurs, all bonded metal objects in the room will have substantially the s ame electrical potential, so that an occupant of the room cannot touch two objects with significantly different potentials. Even if the connection to a distant earth ground is lost, the occupant will be protected from dangerous potential differences. An insulator, also called a dielectric, is a material that resists the flow of electric charge. In insulating materials valence electrons are tightly bonded to their atoms. These materials are used in electrical equipment as insulators or insulation. Their function is to support or separate electrical conductors without allowing current through themselves. The term also refers to insulating supports that attach electric power transmission wires to utility poles or pylons. Use of crimp tools: hand and hydraulic operated;
Handheld , manual
Handheld tools are portable, inexpensive, and effective. They typically have interchangeable die -sets. A manually actuated ratchet crimper can yield up to 180 terminations per hour.
Hydraulic, handheld
Hydraulic crimp tools are hand operated and pump hydraulic fluid into the device to compress the die. Despite being hand-driven, effort is considerably less than other manual crimpers.
Testing of crimp joints; Crimp Testing There are several destructive tests an operator can utilize to ensure the quality of the crimp. Bend test: A quality connection will be able to accommodate 90° bends in several directions without misplacing the insulation or wire crimps. Crimp height testing: Measured from the top surface of the formed crimp to the bottom radial surface, this provides a metric for the mechanical and electrical reliability of the connection. A caliper or crimp micrometer is used for this test, and it provides a good measure of terminal compression and process control. Pull test: Attaching hanging weights to the wire for one minute, or using a mechanical pull tester, are means of testing the tensile strength--and crimp quality--of a wire termination. Connector pin removal and insertion; D-sub (d-subminiature) connectors – For use with low-current circuits such as data signals, position sensor feedback, micro-switches, and trim motors. These are used on the Control Unit and Display Unit. Each d-sub connector is unique to minimize the risk of a miss-match. D-sub Terminal Install Step 1: Mark the pin numbers on both sides of the d-sub with a Sharpie Step 2: Strip the end of the wire Step 3: Install terminal into crimper tool, ensuring crimp tool is adjusted to the proper height. The head of the terminal should be flush with the top of the tool. Step 4: Crimp terminal to wire. Step 5: Insert terminal into connector assembly until you hear a slight click. Give the wire a tug to make sure it is fully seated. Visually inspect the other face of the connector to verify proper placement of the terminal. D-sub Pin Removal Step 1: Insert white side of removal tool into connector. Carefully wrap metal prongs around the wire. Step 2: Push down on tool until you feel it seat around the terminal. Note: you may have to fish around for a bit until it seats properly. Step 3: Gently pull the wire and the tool together out of the connector.
Co-axial cables: testing and installation precautions; Coaxial cable, or coax (pronounced 'ko.æks), is a type of cable that has an inner conductor surrounded by a tubular insulating layer, surrounded by a tubular conducting shield.
RG-59 flexible coaxial cable composed of: A. Outer plastic sheath B. Woven copper shield C. Inner dielectric insulator D. Copper core
1. Choose the right cable: there are many coaxial cables on the market and the type you buy can depend on whether you are using it for commercial or domestic purposes 2. Weatherproof: very important because moisture can damage the cable. Seal the end of the cable and make sure the cable's outer sheath is not damaged during installation. Loop the cable up and down to help prevent water from entering. 3. General installation rule of thumb: make sure your cables are not bent or crushed. If coax is bent beyond its limit, then internal damage will occur. 4. Connections: the connections to the connectors must be made correctly and the right quality connectors should be used. Some cheap versions of connectors can take away from the coaxial cable's performance.
CAUTION 1: Avoid Torque Forces (Twisting) While individual coaxial cables within the test adapter have some rotational freedom, twisting the TPA as a unit, with one end held stationary, in excess of +/- 90° may damage or severely degrade performance. Adherence to Caution 5 (below) helps to avoid exceeding twist limits. CAUTION 2: Avoid Sharp Cable Bends Never bend coaxial cables into a radius of 26 mm (1 -inch) or less. Never bend cables greater than 90°. Single or multiple cable bends must be kept within this limit. Bending the TPA cables less than a 26mm (1-Inch) radius will permanently damage or severely degrade test adapter performance. CAUTION 3: Avoid Cable Tension (Pull Forces) Never apply tension (pull forces) to an individual coaxial cable that is greater than 2.3 kg (5 lbs.). To avoid applying tension, always place accessories and equipment on a surface that allows adjustment to eliminate tension on the TPA and cables. Use adjustable elevation stands or apparatus to accurately place and support the TPA. Wiring protection techniques: Cable looming and loom support, cable clamps, protective sleeving techniques including heat shrink wrapping, shielding.
A cable harness, also known as a wire harness, cable assembly, wiring assembly or wiring loom, is an assembly of cables or wires which transmit signals or electrical power. The cables are bound together by straps, cable ties, cable lacing, sleeves, electrical tape, conduit, a weave of extruded string, or a combination thereof. Wire clamps Wire clamps consist of a piece of heavy wire, typically steel, first bent into a tight U, then formed into a ring shape with one end overlapping the other, and finally the ends bent outwards and cut. A captive nut is attached to one end, and a captive screw to the other. When the screw is tightened, the overlapped ends of the wire are pushed apart, tightening the wire loop around the hose. For an explanation of why this design is used, see the section on sealing the connection.
Braided sleeving is a great way to keep hoses, wires and cables safe from abrasion, temperature, chemicals and other damage. Expandable sleeving adds an extra layer of versatility by conforming to bundles of odd shapes & sizes.
High temperature and flame retardant sleeves are built for the most extreme conditions. Most are made of fiberglass, and less commonly from ceramic and material blends. Some of these sleevings operate with no problems in temperatures up to 3000°F. In addition, many models can protect cables from abrasion, moisture, chemicals and fungus.
Side entry braided sleeving makes installation a breeze by allowing you to easily wrap cables, hoses and wires for maximum convenience. The semi-rigid construction of F6 provides an extra layer of flexibility for clean and fast implementation.
Abrasion Resistant Sleeving These sleevings will protect cables from cuts, scratches and other abrasions. Several types are available, including stainless steel, Nylon and Kevlar examples, but all feature woven designs that allow for flexibility while keeping cables, wires, and hoses free from damage, and most are expandable to allow for maximum versatility.
Treated fiberglass sleeve These protective sleevings are ideal for automotive and industrial applications, as well for use in generators, transformers, or any setting where resistance to heat, abrasion, moisture, chemicals or weather corrosion is required.
Silicone coated fiberglass
10. Springs Inspection of springs 1. 2. 3. 4. 5.
Inspect spring free length Inspect spring compression force Inspect for bends Inspect for pitting Inspect coils for rubbing
Because there are many different types of spring carrying out different functions, the answer is not always easy. Normally it is not necessary to NDT springs since the time between crack initiation and breakage is extremely short. NDT assumes that cracks can exist benignly until the next inspection interval allowing one to find the crack before the part breaks in half. The following inspection and replacement criteria is suggested as a general aid to be used when the maintenance manual is lacking:
If the spring is inexpensive - replace it. If the spring works hard and hot - replace it during major maintenance. For example, valve springs. If the spring is in a corrosive environment - replace it. If the spring serves some critical or safety function - replace it. 11. Bearings
Maintenance Instructions: 1. Keep your bearings dirt-free, moisture free, and lubricated. 2. Clean your bearings when they become dirty or noisy with the most environmentally friendly cleaner you can find that is suitable for dissolving oil, grease, and removing dirt from the steel, plastic and rubber surfaces. 3. If you use a solvent cleaner, please wear appropriate rubber gloves and work in a safe wellventilated area. 4. Do not add oil to dirty bearings. It will not clean the bearing, but merely flush the existing dirt further into the bearing. Cleaning Instructions: 1. Gently remove the non-contact rubber shield with a push pin or the edge of a small knife by prying the shield upwards from under the shield at the inner race. 2. Optional Cage Removal: You can clean your bearings more thoroughly by removing the ball retainer or “cage.” 3. Clean your bearings and your ball retainers 4. Dry your bearings 5. Reinstall your cages 6. Lubricate your bearings 7. Reinstall your clean rubber shields 8. Reinstall your bearings
12. Transmissions
Inspection of gears, backlash;
Gear - is a rotating machine part having cut teeth, or cogs, which mesh with another toothed part in order to transmit torque, in most cases with teeth on the one gear being of identical shape, and often also with that shape on the other gear. Two or more gears working in tandem are called a transmission and can produce a mechanical advantage through a gear ratio and thus may be considered a simple machine.
Backlash - Its clearance or lost motion in a mechanism caused by gaps between the parts. It can be defined as "the maximum distance or angle through which any part of a mechanical system may be moved in one direction without applying appreciable force or motion to the next part in mechanical sequence.
Factors affecting the amount backlash required in a gear train include errors in profile, pitch, tooth thickness, helix angle and center distance, and run-out. The greater the accuracy the smaller the backlash needed. Backlash is most commonly created by cutting the teeth deeper into the gears than the ideal depth. Another way of introducing backlash is by increasing the center distances between the gears.
Inspection of belts and pulleys, chains and sprockets
Belts and Pulleys - is a loop of flexible material used to mechanically link two or more rotating shafts, most often parallel. Belts may be used as a source of motion, to transmit power efficiently, or to track relative movement. Belts are looped over pulleys and may have a twist between the pulleys, and the shafts need not be parallel. In a two pulley system, the belt can either drive the pulleys normally in one direction (the same if on parallel shafts), or the belt may be crossed, so that the direction of the driven shaft is reversed (the opposite direction to the driver if on parallel shafts). As a source of motion, a conveyor belt is one application where the belt is adapted to continuously carry a load between two points.
How to check Belts: 1. 2. 3. 4. 5.
Listen for squealing sounds from the engine. Check belts for signs of wear Check you belts for places where the rubber is slick or glazed in appearance Inspect the pulleys Check the belt tension
Chains and Sprockets Sprocket - is a profiled wheel with teeth or cogs that mesh with a chain, track or other perforated or indented material. The name "sprocket" applies generally to any wheel upon which are radial projections that engage a chain passing over it. It is distinguished from a gear in that sprockets are never meshed together directly, and differs from a pulley in that sprockets have teeth and pulleys are smooth. The word "sprockets" may also be used to refer to the teeth on the wheel.
Chain Inspection
Chain cleanliness and proper lubrication are vital to your chains long life
Check for evidence of wear
Inspect chain for flexibility
Inspect the amount of chain stretch or elongation
Check for any signs of physical damage to the chain, such as broken or cracked parts, loose pins and bushings, or indications of corrosion.
Sprocket Inspection
The sprocket teeth should be inspected for signs of wear, indicating a possible alignment problem. Check the teeth for signs of wear, indicated by a “hooked” shaped Inspect for signs of physical damage to the sprocket, such as broken or chipped teeth, or excessive corrosion. Check the sprocket run out on the shaft, and inspect the keys and keyw ays for wear or damage.
Inspection of Screw Jacks, Push-pull rod systems
Jack Screw - is a type of jack that is operated by turning a lead screw. In the form of a screw jack it is commonly used to lift heavy weights, such as the foundations of houses, or large vehicles.
An advantage of jackscrews over some other types of jack is that they are self-locking, which means when the rotational force on the screw is removed, it will remain motionless where it was left and will not rotate backwards, regardless of how much load it is supporting.
Push-pull Rod Systems - A stiff rod in an aircraft control system that moves a control surface by either pushing or pulling on it.
13. Control Cables
Swaging of End Fittings
Swaging - is a forging process in which the dimensions of an item are altered using dies into which the item is forced. Swaging is usually a cold working process; however, it is sometimes done as a hot working process.
Inspection and Testing of Control Cables
Maintenance:
Moisture Management - Wipe off the control cable as you draw the probe up on the last run of the day. Cable - When necessary, rinse cable (but not connectors) in clean water or wash the cable in a laboratory-grade detergent, such as Liquinox.Do not use solvents to clean the cable. Connectors - If it is necessary to clean the connector, use a cotton swab moistened with alcohol. Sockets can be cleaned with a brush.Do not use spray lubricants or electric contact cleaners. Solvents contained in such products will attack the neoprene inserts in the connectors. Storing Control Cable - Improper coiling of any electrical cable twists conductors and can cause reliability problems. There are several ways to control twisting: Use a cable reel with hub diameter of at least 200mm or 8 inches. Coil cable in a figure-eight. Coil cable using over-under loops.
Inspection: Cuts or Gouges - Deep cuts or gouges allow water to enter cable. In both cases, bad section of cable must be removed, either by shortening the cable or replacing the cable.
Bowden Cables; Aircraft Flexible Control Systems
Bowden Cable - is a type of flexible cable used to transmit mechanical force or energy by the movement of an inner cable (most commonly of steel or stainless steel) relative to a hollow outer cable housing. The housing is generally of composite construction, consisting of a helical steel wire, often lined with nylon, and with a plastic outer sheath.
Transmission 1. A chain removed for routine inspection, it does not need proof loading 2. An aircraft control chain is connected using nuts and bolts 3. If a control chain can be lifted clear of a tooth, it should be removed and an elongation check carried out. 4. In removing a tight link from a chain, it should tap it lightly with a hammer. 5. The initial lubricant on a new chain should not be removed 6. Control chains should be fitted in an aircraft with the minimum of slack in the chain. 7. Backlash is a type of wear associated with gears. 8. After a chain has been cleaned in paraffin it should be dried in hot air. 9. What fraction of the minimum breaking load should be the proof load for a chain? 1/3 10. If corrosion is found on a chain, replace the chain. 11. The three principle dimensions specified for a chain is the diameter of the rollers and the pitch and width between inner plates.
12. The distance between the centers of the rollers and chain is called pitch. 13. The maximum allowable extension of a chain assembly over a normal length is 2%. 14. A feather key locates a gear on a shaft and permits a positive drive and axial movement. 15. A chain is removed by nuts and bolts. 16. To check a chain for elongation, lay flat on a table, apply tensile load and measure.
Control Cables 1. When a control cable is contaminated with acid, it should be rejected or replaced. 2. A balanced cable is installed in a control system to enable the cable to be tensioned 3. The aileron balance cable equalizes the control cable tension. 4. How would you inspect a cable for fraying? Run a rag the full length of the cable. 5. A cable is replaced if a chemical spillage is suspected. 6. The proof loading for cables after swaging is 50% minimum breaking strain. 7. The best way to check control cables for broken wires is to run a rag along the cable in both directions. 8. If the turnbuckles in a control system is being tightened extensively, the aircraft will be heavy on controls 9. The control cable is proof loaded to ensure that the end fittings on the cable are secure.
14. Material Handling Bending Is a manufacturing process that produces a V-shape, U-shape, or channel shape along a straight axis in ductile materials, most commonly sheet metal. Bend Allowance The length of the arc through the bend area at the neutral axis. Bend Angle The included angle of the arc formed by the bending operation. Bend Compensation The amount by which the material is stretched or compressed by the bending operation. All stretch or compression is assumed to occur in the bend area. K-factor Defines the location of the neutral axis. It is measured as the distance from the inside of the material to the neutral axis divided by the material thickness. Mold Lines For bends of less than 180 degrees, the mold lines are the straight lines where the surfaces of the flange bounding the bend area intersect. This occurs on both the inside and outside surfaces of the bend. Neutral Axis Looking at the cross section of the bend, the neutral axis is the theoretical locati on at which the material is neither compressed nor stretched. Set Back For bends of less than 180 degrees, the set back is the distance from the bend lines (see above) to the mold line. Composite materials (also called composition materials or shortened to composites) Are materials made from two or more constituent materials with significantly different physical or chemical properties, that when combined, produce a material with characteristics different from the individual components. The individual components remain separate and distinct within the finished structure. The new material may be preferred for many reasons: common examples include materials which are stronger, lighter or less expensive when compared to traditional materials.
17. Aircraft Handling and Storage Aircraft taxiing/towing and associated safety precautions; Taxiing, also sometimes written "taxying", is the movement of an aircraft on the ground, under its own power, in contrast to towing or push-back where the aircraft is moved by a tug. The aircraft usually moves on wheels, but the term also includes aircraft with skis or floats (for water-based travel). Safety When taxiing, aircraft travel slowly. This ensures that they can be stopped quickly and do not risk wheel damage on larger aircraft if they accidentally turn off the paved surface. Taxi speeds are typically from 5 to 20 knots (9 to 37 km/h; 6 to 23 mph). Rotor downwash limits helicopter hover-taxiing near parked light aircraft. The use of engine thrust near terminals is restricted due to the possibility of jet blast damage.
Towing is necessary to enable the aircraft to be moved without engine power. The procedure required will vary greatly dependent on the type of aircraft to be moved. Safety (a) Aircraft must not exceed walking pace while being towed (in closed area). (b) Oleo-leg and tyres must be correctly inflated prior to moving the aircraft, and sufficient brake pressure available for an emergency stop. (c) Undercarriage ground locks must be fitted prior to towing (d) At night Aircraft navigation lights must be “ON” (e) By-pass pin or towing pin must be fitted before connecting the tow bar. (f) A person in charge with all other team members in his sight. (g) Personnel must be stationed on the wing tip and tail to ensure clearance round obstacles. (h) There must be a competent person occupying the pilot set to operate the aircraft brakes in case of emergency.
Aircraft jacking, chocking, securing and associated safety precautions;
Jacking Procedure - Raising The general procedure for raising the complete aircraft on jacks is as follows: 1
Place Safety Barriers in position around the aircraft.
2
Place warning notices in the aircraft cockpit.
3
Ensure that Ground Safety Locks are fitted to all Landing Gears.
4
Ensure Wheel Chocks are fitted.
5
Ensure the Brakes are applied.
6
Ensure that the aircraft is balanced and stable.
7
Ensure that the aircraft is in the ‘Clean Flight Configuration’. (Flaps/Slats are housed)
8
Deactivate the relevant circuit breakers to ensure that there will be no movement of flight controls or the operation of other in-flight systems. NB: As the aircraft is raised it moves from the ‘Ground Configuration’ to the ‘Flight Configuration’.
9
Fit Jacking Pads and Adaptors.
10
Position the jacks under the aircraft, just taking a little of the aircraft’s weight.
11
Remove Wheel Chocks.
12
Release the Brakes.
13
Ensure that all the passenger/crew doors, the emergency exits and the cargo doors are closed and locked or fully open and locked.
14
Remove access ladders and platforms.
15
Clear the area around the aircraft of all ground support and maintenance e quipment and ensure that no other work is being carried out.
16
Operate the nose jack if necessary to ensure the aircraft is longitudinally stable.
17
Slowly operate the jacks at the same time to keep the aircraft level until the appropriate clearance is achieved between the main landing gear wheels and the ground.
18
Ensure that throughout the jacking operations the jack Safety Locking Collars are kept approximately 2.5 cms clear of the jack body.
19
On completion of all jack raising operations the aircraft should be levelled to the ‘datum position’, the jack Safety Locking Collars tightened and the aircraft made stable by the fitting of trestles or a safety stay.
Aircraft storage methods; Categories of Storage. The length of time that the aircraft will be inactive will determine which of the following categories of storage will be used.
Flyable Storage Flyable storage is the prescribed procedure to maintain a stored aircraft inoperable condition. Next to daily use, this category of storage keeps the aircraft in the best possible condition. All scheduled preventative maintenance will be performed on aircraft in flyable storage, and periodic operation of the aircraft and all systems is required. There is no time limit on flyable storage. Short Term Storage Short term storage issued to store an aircraft for a period not to exceed 45days. Aircraft in short term storage require extensive preservation but very little periodic attention. Intermediate Storage Intermediate storage issued to store aircraft for a period of 46 to 180 days. Aircraft in intermediate storage require very extensive preservation but minimal periodic attention. Long Term Storage Procedures for long term storage are not available for the storage of Army aircraft if storage beyond 180 days is required, the aircraft will be depreserved, returned to flyable status, operated, and represerved in accordance with this chapter.
Refuelling/defuelling procedures;
Aircraft fuel is highly combustible and burning AVgas is only useful to us inside an engine while trying to rotate the propeller.
Refueling
Check the color and type of fuel before the actual delivery. 100 octane aviation gasoline (AVgas) is green and 100 octane low lead AVgas is blue. Jet fuel is usually clear, but sometimes it is a very light yellow color as is normal road diesel and biodiesel. Red diesel is, well, colored red.
No smoking within at least 50 feet of an aircraft.
Refuel outside only. Remember: when refueling an aircraft within a closed hanger a situation could develop where the combination of air and fuel vapors are very explosive! One spark due to static electricity and your flight will end prematurely.
The aircraft and fueling vehicles or equipment should be bonded together to dissipate static electricity collected during refueling.
Always keep fire extinguishers nearby.
Portable electronic devices should be switched off (cellphones, radio's, pagers).
If a spill occurs, refueling should be stopped and the airport fire department notified, if necessary.
Ground power units should not be connected or disconnected during refueling.
Persons refueling aircraft should not carry lighters or matches when refueling.
At the first sight of lightning in the area, refueling operations should be suspended.
Refueling may not be conducted with passengers on board the aircraft.
Avoid contact with fuel. The health risks are high if fuel gets into your body, this is possible via the eyes, skin contact, ingestion of via inhalation. Get medical help if this happens.
AVgas refueling must not be done with the engines running (hot refueling) and be careful if hot refueling with JET A.
Make sure the fuel nozzle is clean and keep dirt and water away from the fuel caps, also support the nozzle preventing damage to the wing tank.
Replace the fuel caps securely, loosing a cap in flight will guarantee a loss of fuel and possible wing damage.
Wait some 30 minutes before sampling fuel, gently rock the wings so that any water and debris can settle near the sample port.
Defueling
pumping excess duel into drums by a hand pump, make sure the suction end is clean before inserting it into the aircraft tanks
or by opening the drain points and let the fuel run via a funnel with filter into a container suitable for aviation fuel
if you defuel and store AVgas keep in mind that the shelf life is about a year (commercial operators) due to gum forming caused by oxidation
Make sure to take every safety precaution when defueling the aircraft as the dangers remain the same as with refueling.
De-icing/anti-icing procedures; If any of these critical surfaces are contaminated with frost, ice, show or slush, then the aircraft must be de-/anti-iced prior to dispatch. DE-ICING is a procedure by which frost, ice or snow is removed from an aircraft in order to obtain “clean”, free of contamination surfaces. ANTI-ICING is a precautionary procedure that provides protection against the formation of frost or accumulation of ice and snow on treated surfaces for a limited period of time, which is called “the holdover time” (HOT).
DE-ICING/ANTI-ICING
is
a
combination
of
the
two
above-mentioned
procedures.
● ONE-STEP: The de-icing procedure is carried out with a heated mixture that also ensures the necessary protection against frost, snow and ice formation (the anti -icing layer). ● TWO-STEP: De-icing procedure is performed first and then an anti-icing layer is sprayed on the CLEAN surfaces of the aircraft. The selection of a one- or two-step process depends upon weather conditions, available equipment and fluids and the HOT to be achieved.
De-/anti-icing methods There are several aircraft de-icing methods: - Manual de-icing, this can be either performed by using brooms or brushes, by using wing and propeller covers or by using air blowers. This option will reduce the amount of contamination on the surfaces of the aircraft even if the surface is not entirely clean. - Hot air de-icing systems are used to melt snow and ice from specific areas that cannot be sprayed with de-icing fluids: e.g. landing gear, engines, propellers, cockpit windows. - Hot de-icing fluids combined with water is a method used to remove the accumulations of ice and snow on the aircraft. Heated fluids are very important when removing contaminants, just as the pressure of the spray is paramount to breaking the ice bond.
- Infra-red (IR) de-icing systems use natural gas- or propane-fired radiant heaters in order to melt frost, ice and snow. This technology does not heat up the surrounding air and works well especially for small aircrafts.
Electrical, hydraulic and pneumatic ground supplies. GPU (Ground Power Unit) A ground power unit (GPU) may be used to supply electric power for an aircraft on the ground, to sustain interior lighting, ventilation and other requirements before starting of the main engines or the aircraft auxiliary power unit (APU).
HPU (Hydraulic Power Unit) is used for hydraulic ground supply.
17. Disassembly, Inspection, Repair and Assembly Techniques 18.1 Types of defects and visual inspection techniques; Brinelling is the permanent indentation of a hard surface. It is named after the Brinell scale of hardness, in which a small ball is pushed against a hard surface at a preset level of force, and the depth and diameter of the mark indicates the Brinell hardness of the surface.
Burnishing is the plastic deformation of a surface due to sliding contact with another object. Visually, burnishing smears the texture of a rough surface and makes it shinier.
A burr is a raised edge or small pieces of material remaining attached to a workpiece after a modification process.It is usually an unwanted piece of material and is removed with a deburring tool in a process called 'deburring'.
Metal burr extending beyond the edge of the cut piece, view on the cut face (top) and from the bottom (bottom)
Corrosion is the gradual destruction of materials (usually metals) by chemical reaction with its environment.
Crack A physical separation of two adjacent portions of metal, evidenced by a fine or thin line across the surface caused by excessive stress at that point.
Cut Loss of metal, usually in appreciable depth over a relatively long and narrow area, by mechanical means, as would occur with the use of the saw blade, chisel, or sharp-edged stone striking a glancing blow.
Dent Indentation the metal surface produced by an object striking with force. The surface surrounding the indentation is usually slightly upset.
Erosion Loss of metal from the surface by mechanical action of foreign objects, such as grit or fine sand. The eroded are is rough and may be lined in the direction in which the foreign material moved relative to the surface.
Chattering Breakdown or deterioration of metal surface by vibratory or chattering action. Although chattering may give the general appearance of metal loss or surface cracking, usually, neither has occurred.
Galling is a form of wear caused by adhesion between sliding surfaces. Galling is caused by a combination of friction and adhesion between the surfaces, followed by slipping and tearing of crystal structure beneath the surface.
Gouge Groove in, or breakdown of, a metal surface from contact with foreign material under heavy pressure. Usually it indicates the metal loss but may be largely the displacement of material.
Inclusion Presence of foreign or extraneous material wholly within a portion of metal. Such material is introduced during the manufacture of rod, bar or tubing by rolling or forging.
Nick Local break or notch on an edge. Usually it involves the displacement of metal rather than loss.
Pitting corrosion, or pitting, is a form of extremely localized corrosion that leads to the creation of small holes in the metal.
A corrosion pit on the outside wall of a pipeline at a coating defect before and after abrasive blasting Scratch Slight tear or break in metal surface from light, momentary contact by foreign object.
v Score Deeper (than scratch) tear or break in metal surface from contact under pressure. May show discoloration from temperature produced by friction.
A stain is a discoloration that can be clearly distinguished from the surface, material, or medium it is found upon.
. Upsetting A displacement of material beyond the normal contour or surface (a local budge or bump). Usually it indicates no metal loss.
Corrosion removal, assessment and reprotection.
Remove all corrosion you discover with fine sandpaper, Scotch-Brite pads, or aluminum wool.
After removing the corrosion, acid etch the aluminum by washing it with Poly-Fiber's E-2310 Acid Etch, diluted with water, or a similar product.
After thoroughly rinsing the area, wash it with E-2300 Conversion Coating.
Rinse the area again and let it dry completely before priming and painting the surface.
18.2 General repair methods, Structural Repair Manual; Ageing, fatigue and corrosion control programs; Definition An aircraft begins to ‘age’ as soon as it first flies and various effects of aging begin to occur almost immediately. The maintenance issues which have particularly arisen with aging aircraft structural failure have generally been seen as arising from fatigue or corrosion, with corrosion sometimes initiating fatigue effects. Metallic Corrosion Metallic Corrosion occurs when chemical action causes deterioration of the surface of a metal. Most corrosion is galvanic or electrolytic in origin, which means that it has occurred because two dissimilar metals have been together in an electrolyte (usually contaminated water). Chronological age is especially relevant to corrosion incidence, as are the ground environment where an aircraft is usually parked and the typical flight environment. Of the three main areas of aging aircraft safety concern, corrosion was probably the first to be routinely recognized and so dramatic events attributable solely to undetected corrosion are relatively infrequent thanks to extensive, and generally effective, inspection regimes.
Structural Fatigue Structural Fatigue has produced a number of ageing aircraft losses. The possibility of structural fatigue from any origin has been actively considered since the advent of pressurized aircraft when there were accidents attributable to an insufficient understanding of some basic design issues. The mechanism by which fatigue propagates in a structure is the well-known crack. Cracks propagate because the geometry of a crack produces a very high concentration of stress at the end of the crack and eventually, if a growing crack goes undetected, fracture will occur. Fatigue cracks have been found to arise in three main ways:
in internal load-bearing airframe structural components which can develop stress ‘hot spots’;
in load bearing skins of large aircraft in which the skin itself carries a significant structural load;
from fastener holes such as those for rivets, bolts, nuts and screws where locali zed stress concentration can initiate premature cracking.
18.3 Non-destructive inspection techniques including, penetrant, radiographic, eddy current, ultrasonic and borescope methods. Defect detection techniques fall into two categories:
Those that can only detect defects on or near to the surface of a component (Surface Techniques);
Those which can detect both surface and embedded defects (Volumetric Techniques).
Surface Techniques
Dye Penetrant Inspection (PT)
Eddy Currents
Magnetic Particle Inspection (MPI or MT)
Volumetric techniques
Radiography
Ultrasonics
Other techniques (in alphabetical order)
AC-FM - Alternating Current Field Measurement
Acoustic Emission
Creep waves
Digital Filmless Radiography
Flash Radiography
Leak Testing
Long Range Ultrasonics
Magnetic Flux Leakage (MFL)
Phased Array Inspection
Pressure Testing
Pulsed Eddy Currents
Radioscopy
Remote Field Eddy Currents
Replication
Shearography
Time of Flight Diffraction. TOFD
Thermography
18.4
Disassembly and re-assembly techniques.
1. Interpret specifications and organize materials 1.1 The procedure for assembly/disassembly of structure is determined in order to plan equipment use 1.2 Appropriate jigs, fixtures or bracing methods are selected to ensure maintenance of contour/structural integrity during disassembly/assembly operations 1.3 All components and equipment are organized 2. Prepare aircraft or sub-assembly for structural disassembly 2.1 Structure is supported with appropriate jigs, fixtures or bracing, as required 2.2 Structural components are removed, as required, to provide access 3. Disassemble aircraft structure or sub-assembly 3.1 Aircraft standard practices are applied in the removal of structural hardware and fasteners 3.2 Disassembled components are tagged, as required, to facilitate correct reassembly 4. Prepare components and tooling for assembly 4.1 Jigs and fixtures are set up to ensure accuracy of component assembly 4.2 Replacement component alignment is checked for conformance to specifications prior to fastener hole generation 4.3 Hole location/relocation is carried out in accordance with specification procedures and standard practices 4.4 Standard practices in hole generation sequencing are followed to ensure that assembly stress defects are not built in 4.5 Components are disassembled, cleaned, deburred and surface treatments applied prior to final assembly
5. Assemble aircraft structure or sub- assembly 5.1 Sealants and/or adhesives are selected and applied in accordance with assembly specifications or applicable documentation 5.2 Components are positioned and secured with appropriate temporary fastening devices for accurate assembly 5.3 Fasteners are selected and installed in accordance with assembly specifications or applicable manuals 6. Inspect completed assemblies 6.1 Assembled components are inspected to confirm dimensional accuracy and specifications are met 6.2 Checking or testing equipment is used, where appropriate, to ensure requirements are met 6.3 Aircraft mensuration is checked for compliance with applicable maintenance manuals, where necessary 6.4 Required documentation is completed and processed in accordance with standard enterprise procedures
18.5 Trouble shooting techniques Tip #1: Talk to the flight crew. Tip #2: Take time to fully under- stand the system’s installation. Tip #3: Use your head before your hands. Tip #4: Is this thing on? Tip #5: Only change one thing at a time. Tip #6: Check antennas, wires and connectors. Tip #7: Is it making its connection during flight? Tip #8: Autopilot “Porpoising.” Tip #9: Troubleshoot your troubleshooting equipment. Tip #10: The spin on gyro systems.
19. Abnormal Events 19.1 Inspections following lightning strikes and HIRF penetration. LIGHTNING-STRIKE STRUCTURAL INSPECTION PROCEDURES
If lightning strikes an airplane, a lightning-strike conditional inspection must be performed to locate the lightning-strike entrance and exit points. When looking at the areas of entrance and exit, maintenance personnel should examine the structure carefully to find all of the damage that has occurred.
The conditional inspection is necessary to identify any structural damage and system damage prior to return to service. The structure may have burn holes that can lead to pressurization loss or cracks. The critical system components, wire bundles, and bonding straps must be verified as airworthy prior to flight.
Airplane lightning-strike zones are defined by SAE Aerospace Recommended Practices (ARP) 5414. Some zones are more prone to lightning strikes than others. Lightning-strike entrance and exit points are usually found in Zone 1, but can very rarely occur in Zones 2 and 3. A lightning strike usually attaches to the airplane in Zone 1 and departs from a different Zone 1 area. The external components most likely to be hit are:
Radome.
Nacelles.
Wing tips.
Horizontal stabilizer tips.
Elevators.
Vertical fin tips.
Ends of the leading edge flaps.
Trailing edge flap track fairings.
Landing gear.
Water waste masts.
Air data sensors (pitot probes, static ports, angle of attack [AOA] vane, total air temperature probe).
Figure 8: Lightning zone definitions Airplane lightning zones as defined by SAE Aerospace Recommended Practices 5414. Zone Designation
Description
Definition
1A
First return stroke zone All areas of the airplane surfaces where a first return is likely during lightning channel attachment with a low expectation of flash hang on.
1B
First return stroke zone All areas of the airplane surfaces where a first return is likely with a long hang on during lightning channel attachment with a low expectation of flash hang on.
1C
Transition zone for first All areas of the airplane surfaces where a first return stroke return stroke of reduced amplitude is likely during lightning channel attachment with a low expectation of flash hang on.
2A
Swept stroke zone
2B
Swept stroke zone with All areas of the airplane surfaces into which a lightning long hang on channel carry subsequent return stroke is likely to be swept with a high expectation of flash hang on.
3
Strike locations other Those surfaces not in Zone 1A, 1B, 1C, 2A, or 2B, where any than Zone 1 and Zone 2 attachment of the lightning channel is unlikely, and those portions of the airplane that lie beneath or between the other zones and/or conduct a substantial amount of electrical current between direct or swept stroke attachment points.
All areas of the airplane surfaces where a first return of reduced amplitude is likely during lightning channel attachment with a low expectation of flash hang on.
Figure 9: Airplane lightning zones Areas of an airplane that are prone to lightning strikes are indicated by zone. Zone 1 indicates an area likely to be affected by the initial attachment of a strike. Zone 2 indicates a swept, or moving, attachment. Zone 3 indicates areas that may experience conducted currents without the actual attachment of a lightning strike.
In Zone 2, an initial entry or exit point is a rare event, but in such a case, a lightning channel may be pushed back from an initial entry or exit point. As an example, the radome may be the area of an initial entry point, but the lightning channel may be pushed back along the fuselage aft of the radome by the forward motion of the airplane. A Zone 3 examination is highly recommended even if no damage is found during the Zone 1 and Zone 2 examinations. In summary, any entrance and exit points must be identified in Zones 1, 2, or 3 so that the immediate areas around them can be thoroughly examined and repaired if necessary.
19.2 Inspections following abnormal events such as heavy landings and flight through turbulence. (8) Heavy or Overweight Landings An aircraft landing gear is designed to withstand landings at a particular aircraft weight and vertical descent velocity. Overstressing can also be caused by landing with drift or landing in an abnormal attitude (e.g. nose or tail wheel striking the runway before the main wheels).
The damage resulting from a heavy landing is normally concentrated around the landing gear, its supporting structure in the wings or fuselage, the wing and stabilizer attachments and the engine mounts. Secondary damage can be found on the fuselage upper and lower skin and structure, and wing skin and structure, depending on the configuration and loading of the aircraft.
On some aircraft the manufacturer can recommend that if no damage is found in the primary areas, the secondary areas need not be inspected; but if damage is found in the primary areas, then the inspection shall be continued.
(a) Landing Gear (i) Examine tires for creep, flats, bulges, cuts, pressure loss and enlargement. (ii) Examine wheels and brakes for fluid leaks, cracks and other damage. (iii) Examine axles, struts and stays for distortion and other damage. (iv) Check shock struts for fluid leaks, scoring and abnormal extension. (v) Examine landing gear attachments for cracks, other damage and signs of movement. In some instances this can require the removal of certain bolts in critical locations, for detailed nondestructive testing. (vi) Examine the structure in the vicinity of the landing gear attachments for signs of cracks, distortion, movement of rivets or bolts and fluid leakage. (vii) Examine doors and fairings for damage and distortion. (viii) Jack the aircraft and carry out retraction and nose-wheel steering tests; check for correct operation of locks and warning lights, clearances in wheel bays, fit of doors and signs of fluid leaks.
(b) Wings (i) Examine the upper and lower skin surfaces for signs of wrinkling, pulled rivets, cracks and movement at skin joints. Inertia loading on the wing will normally result in wrinkles on the lower surface and cracks or rivet damage on the upper surface, but stress induced by wing-mounted engines can result in wrinkles on either surface.
(ii) Check for signs of fuel leaks and seepage from integral tanks. (iii) Examine wing root fillets for cracks and signs of movement. (iv) Check flying controls for freedom of movement. (v) Check balance weights, powered flying control unit mountings and control surface hinges for cracks, and control surfaces for cracks or bucking. (vi) Check spars for distortion and cracks.
(c) Fuselage (i) Examine fuselage skin for wrinkling or other damage particularly at skin joints and adjacent to wing and landing gear attachments. (ii) Examine pressure bulkheads for distortion and cracks. (iii) Examine the supporting structure of heavy components such as galley modules, batteries, water tanks, fire extinguishers, auxiliary power units, etc. for distortion and cracks. (iv) Check that the inertia switches for fire extinguishers, emergency lights, etc, have not tripped. (v) Check instruments and instrument panels for damage and security. (vi) Check ducts and system pipelines for leaks and buckling. (vii) Check fit of access doors, emergency exits, etc., and surrounding areas for distortion and cracks. (viii) Check loading and unloading operation of cargo containers and condition of cargo restraint system.
(d) Engines (i) Check engine and propeller controls for full and free movement. (ii) Examine engine mounts and pylons for damage and distortion, tubular members for bowing and cracks at welds, mounting bolts and attachments for damage and evidence of movement. (iii) Check freedom of rotating assemblies - on piston engines, check freedom of rotation with spark plugs removed. (iv) Examine engine cowlings for wrinkling and distortion, and integrity of fasteners. (v) Check for oil, fuel and hydraulic fluid leaks. (vi) Check propeller shaft for alignment.
(e) Empennage (i) Check flying controls for freedom of movement. (ii) Examine rudder and elevator hinges for cracks, and control surfaces for cracks and distortion, particularly near balance weight fittings. (iii) Examine stabilizer attachments and fairings, screw jacks and mountings for distortion and signs of movement.
(f) Engine Runs Provided that no major structural distortion has been found, engine runs shall be carried out to establish the satisfactory operation of all systems and controls. A general check for system leaks shall be carried out while the engines are running, and on turbine engines the rundown time shall be checked.
(g) Helicopters The inspections necessary on helicopters are broadly similar to those detailed in the preceding paragraphs, but additional checks are normally specified for the main rotor blades, head and shaft, tail rotor and transmission. The inspections outlined below are typical. (i) Examine the rear fuselage or tail boom for evidence of strike damage from the main rotor blades, and if damage is found, check for cracks, security, and symmetry. (ii) Remove the main rotor blades and examine them for twisting and distortion. Check the surface for cracks, wrinkles or other damage, and check the security of the skin attachment rivets or structural bonding. If the main rotor blades are badly damaged through impact with the tail boom or ground, certain components in the transmission can be shockloaded, and it shall be necessary to refer to the instructions for rotor strikes (see section13 below). (iii) For the main rotor head, disconnect pitch change rods and dampers, and check that the flapping hinges, drag hinges and blade sleeves move freely, without signs of binding or roughness. Examine the rotor head and blade stops for cracks or other damage, and the dampers for signs of fluid leaks. Damage in this area can be an indication of further damage inside the main gearbox. (iv) Examine the tail rotor blades for damage and security, and the coning stops for evidence of damage. Damage to the tail rotor blades which is beyond limits shall entail eithe r further inspection, or replacement of the hub, pitch change links, tail rotor gear box and drive shaft.
(9) Flight in Severe Turbulence The type of damage that results from flight through severe turbulence is similar to that resulting from a heavy landing, the major difference being that the damage is less localized, and that wheel and brake assemblies are unlikely to be affected.
On some aircraft an indication of the severity of the loads experienced can be obtained from accelerometers or fatigue meters. These instruments, however, are designed to record steady loads, and peak forces recorded during flight through turbulence can be exaggerated due to instrument inertia. Generally, readings outside the range of -.5 g to + 2.5 g on transport category aircraft are cause for investigation. Most aircraft do not have such instrumentation, and all incidents of flight through severe turbulence shall be investigated.
Severe turbulence can cause excessive vertical or lateral forces on the aircraft structure, and the effects can be increased by the inertia of heavy components such as engines, fuel tanks, water tanks and cargo. Damage can be expected at main assembly points such as the wing to fuselage joints, tail to fuselage joints and engine mountings. Damage can also occur in those areas of the wings, fuselage, stabilizer and control surfaces where the greatest bending moment takes place (i.e. part way along their length, and can be indicated by skin wrinkles, pulled rivets or similar faults). An inspection for damage after a report of flight through severe turbulence shall include the inspections detailed in Section (8) above, except, in most cases, those covering the landing gear.
20. Maintenance Planning Maintenance planning and scheduling prioritizes and organizes work so it can be executed in the most efficient manner. It’s getting the right people in the right place with the necessary tools, parts and information to perform the required task. The benefits of proper planning and scheduling include:
Cost savings due to efficient use of maintenance labor hours Increased production yield from faster execution of jobs Reduced injuries and stress from a better work flow
Maintenance planning and scheduling are two activities that ensure the allocation of needed resources and the sequence in which they are needed so any activity can be performed in the shortest time with the least cost. Although planning and scheduling are often spoken in the same breath, they are t wo separate functions. Planning defines the WHAT, WHERE, and HOW, while scheduling defines the WHO and WHEN.
Effective aircraft maintenance planning and scheduling must:
Optimally balance marketing’s desire for schedule flexibility with Operations reliability focus and maintain workable fleet routing schedules through established Minimum Maintenance Requirements. Evaluate and redesign maintenance programs and fleet schedules to optimize ground time and eliminate wasted effort arising from poorly sequenced tasks. Plan an evolving, operationally sound maintenance strategy, with clear expectations and processes to manage scheduled and unscheduled requirements. Align A check packages to enhance station productivity and task yield while reducing planning and aircraft routing constraints. Strategically aligned and continuously coordinated efforts between Maintenance Programs, Engineering, Inspection, Technical Training, Engine Planning, Heavy Maintenance Planning, and Line Operations to ensure timely and accurate completion of maintenance activities. Refine and utilize planning and scheduling tools that provided visibility of maintenance requirements, station capabilities and capacity, nightly station workload assignment, task prioritization of work packages, and real time task completion accountability reporting. Evaluate performance measures to ensure processes and operational execution is being managed. Efficiently adjust operational resources and/or planning to support changes in business drivers (i.e. # aircraft, aircraft utilization, etc.) that optimizes asset usage and maximizes resources- labor, materials, hangar slots, etc.
Stored Procedure - is a subroutine available to applications that access a relational database system. A stored procedure is actually stored in the database data dictionary.
Typical use for stored procedures include data validation (integrated into the database) or access co ntrol mechanisms. Furthermore, stored procedures can consolidate and centralize logic that was originally implemented in applications. Extensive or complex processing that requires execution of several SQL statements is moved into stored procedures, and all applications call the procedures. One can use nested stored procedures by executing one stored procedure from within another.
CERTIFICATION / RELEASE PROCEDURES I. Components a) A certificate of release to service shall be issued at the completion of any maintenance on an aircraft component whilst off the aircraft. b) The authorized release certificate in accordance with document SA - CATS 43 constitutes the aircraft component certificate of release to service. MAINTENANCE INSPECTION A maintenance inspection is a routine inspection of an aircraft which is conducted to make sure that it is in good working order. This type of inspection can be performed by the mechanic. It is a good idea to make regular maintenance inspections so that any problems can be identified at an early stage, allowing people to intervene promptly to correct them. A Check This is performed approximately every 500 - 800 flight hours or 200 - 400 cycles. It needs about 20 - 50 man-hours and is usually performed overnight at an airport gate or hangar. The actual occurrence of this check varies by aircraft type, the cycle count (takeoff and landing is considered an aircraft "cycle"), or the number of hours flown since the last check. The occurrence can be delayed by the airline i f certain predetermined conditions are met. B Check This is performed approximately every 4–6 months. It needs about 150 man-hours and is usually performed within 1–3 days at an airport hangar. A similar occurrence schedule applies to the B check as to the A check. B checks may be incorporated into successive A checks, i.e.: A-1 through A-10 complete all the B check items. C Check This is performed approximately every 20–24 months or a specific amount of actual flight hours (FH) or as defined by the manufacturer. This maintenance check is much more extensive than a B Check, requiring
a large majority of the aircraft's components to be inspected. This check puts the aircraft out of service and until it is completed, the aircraft must not leave the maintenance site. It also requires more space than A and B Checks—usually a hangar at a maintenance base. The time needed to complete such a check is generally 1–2 weeks and the effort involved can require up to 6000 man-hours. The schedule of occurrence has many factors and components as has been described, and thus varies by aircraft category and type. D Check This is by far the most comprehensive and demanding check for an airplane. It is also known as a Heavy Maintenance Visit (HMV). This check occurs approximately every 5 years. It is a check that, more or less, takes the entire airplane apart for inspection and overhaul. Also, if required, the paint may need to be completely removed for further inspection on the fuselage metal skin. Such a check can usually demand up to 50,000 man-hours and it can generally take up to 2 months to complete, depending on the aircraft and the number of technicians involved. It also requires the most space of all maintenance checks, and as such must be performed at a suitable maintenance base. Given the elevated requirements of this check and the tremendous effort involved in it, it is also by far the most e xpensive maintenance check of all, with total costs for a single visit ending up well within the million-dollar range. Because of the nature and the cost of such a check, most airlines — especially those with a large fleet — have to plan D Checks for their aircraft years in advance. Often, older aircraft being phased out of a particular airline's fleet are either stored or scrapped upon reaching their next D Check, due to the high costs involved in it in comparison to the aircraft's value. On average, a commercial aircraft undergoes 2–3 D Checks before it is retired. Many Maintenance, Repair and Overhaul (MRO) shops state that it is virtually impossible to perform a D Check profitably at a shop located within the United States. As such, only a few of these s hops offer D checks.
Control of Life Limited Components Aircraft life-limited parts are those parts identified by the aircraft manufacturer or production certificate holder as being limited to a total life counted in hours, cycles, landings, or by calendar. A technician installing a life-limited part is responsible for, and should be held accountable for, recording all of the pertinent information regarding the part and its replacement in the appropriate maintenance re- cords. This includes documentation of the part removed as well. Another type of life-limited parts that receiving inspectors should be aware of are those that have a limited shelf life. Parts that have a specific shelf life - a limit as to how long they are eligible to be used must be identified in some fashion to ensure that they are not used in the maintenance of aircraft once the shelf life has expired. Examples of shelf life-limited materials are, adhesives, solvents, sealants, Orings, and other rubber products, and fire extinguisher squibs. Proper control over these items means purging such materials from the inventory before their shelf life has expired. When these types of materials are received, the receiving inspector should identify them in an obvious way. Inspectors should also be aware of life-limited materials with a limit to the period of time the material remains usable after its container's seal has been broken. Such materials have what is termed a limited usable life.
An effective way to manage materials with a limited useful life is to mark the material with a date when it is opened. The marking usually occurs when they are purchased from the parts store and moved to the shop floor by the technicians. The most effective procedure I have seen is to mark those material containers with a colored dot when they are received from the vendor. The colored dot alerts the parts personnel to mark the check-out date on the material when it is checked out from the parts store.
