Vernier Caliper Essay
Vernier caliper is a precision measuring instrument for checking the accuracy of an object for internal, external, and depth measurement. It consists of main and vernier scale. The largest no. represents inches. The smaller no. is tenth of an inch. Each tenth is divided into 4 parts or 0.025”. The vernies scale has 25 divisions. This will divide each graduation on the main scale into 0.001”.
Several precautions should be taken before using vernier caliper. Firstly, one must avoid from dropping it frequently. Secondly, one must also prevent heat and moisture from making contact with this tool. Before making measurements with Vernier caliper, several pre-used checks have to be done first. Firstly, the user of this tool should refer to the Manufactured Manual for precautions, procedures, operation and security. Secondly, choose and select the correct type and size of vernier caliper. Thirdly, check its serviceability and calibration date or tag. Also, check its zeroing. The jaws should be closed firmly and zero mark on the main scale coincides with the zero mark on the vernier scale. Finally, check the Vernier caliper physically for any damage. The jaws should be cleaned, remained sharp, free from corrosion and smoothly moved. The object that will be measured also should be clean.
The first step to make a measurement with vernier caliper is to put the object to be measured in between the jaws and move the jaws into a contact to object. Next, lock the retainer to prevent any movement while taking out the readings and remove the object from the jaws carefully. Then, begin reading the measurement on vernier caliper. Firstly, read the main scale in inches. Find the value of the large number on the main scale before the zero value on the vernier scale. It shows 4 means 0.400”. Next, find the value of the smaller number on the main scale. It shows less than 1 which means 0.000”. After that, find the first line on the vernier scale that lines up perfectly with a line on the main scale. It shows 10 which means 0.010”. Therefore the reading is 0.400” + 0.000” + 0.010” = 0.410”. As a precaution, check the reading twice to ensure correct and accurate measurement.
Finally, after measurement has been made, clean the vernier caliper properly and apply light oil to prevent corrosion. Ensure the jaws are not fully closed to prevent contact corrosion and keep it in box to protect it from heat and moisture.
Micrometer is a precision measuring instruments for checking the accuracy of an object in distance thousand of an inch. It consists of two parts which are the barrel scale and thimble scale.
Several precautions should be taken before using micrometer. Firstly, one must avoid from dropping it frequently. Secondly, one must also prevent heat and moisture from making contact with this tool. Before making measurements with micrometer, several pre-used checks have to be done first. Firstly, the user of this tool should refer to Manufactured Manual for precautions, procedures, operation and security. Secondly, check its serviceability and calibration date. Thirdly choose and select the correct type and range of micrometer. Also, check its zeroing. The anvil and spindle should be brought together into a contact and the ratchet should click twice in maximum. Next, check the common parts of micrometer including thimble, barrel, C-shaped frame and locking nut are always in a good condition. The locking nut should be lock firmly. Finally, inspect for any physical damage. The anvil and spindle surfaces should be cleaned, flat, and free from corrosion. The ratchet and spindle can be rotated smoothly. The object that will be measured also should be clean.
The first step to make a measurement with micrometer is to put the object in between the anvil and spindle. Turn the thimble until the anvil and spindle are touching to the object. Then, turn the ratchet to adjust tightness until it clicks twice in maximum. Lock the locking nut to prevent any movement while taking out the readings. Then, remove the object carefully. Start reading the measurement by reading the barrel scale in inches first. It shows 4 which means 0.400”. Next, find the value of the smaller number on the main scale. It shows less than 1 which means 0.000”. Finally, read the division on the thimble scale. It shows 10 which means 0.010”. Therefore the reading is 0.400” + 0.000” + 0.010” = 0.410”. As a precaution, check the reading twice to ensure correct and accurate measurement.
Finally, after measurement has been made, clean the micrometer properly and apply light oil to prevent corrosion. Ensure the anvil and spindle are not fully closed to prevent contact corrosion and keep it in box to protect it from heat and moisture.
Torque wrench is a measuring tool that measures the amount of force applied to a fastener and prevent it from over tightening. This tool is issued by the tool crib man.
Several precautions should be taken before using torque wrench. Firstly, the user should remember the wet torque value is less than dry torque value. Wet torque is well lubricated. Secondly, it is not recommended to exceed maximum torque value and don’t over tighten when using torque wrench. If the fastener is over torque, it needs to be loosened and re-torqued to the proper value. Don’t back it off and leave it un-torqued. Next, when many fasteners are going to be torque, tighten the fasteners in sequence of cross to prevent crack. Do not use torque wrench as a torque breaker and make sure to torque on the nut not on the bolt. To use torque wrench correctly, one should hold torque wrench close to the center and apply smooth force and even motion. Make sure to torque perpendicularly to the fastener.
Before tightening a fastener with torque wrench, several pre-used checks should be done first. Firstly, the user of this tool should refer to Manufactured Manual for precautions, procedures, operation and security. Secondly, choose and select the correct type of torque wrench for a specific nut. Next, check for its serviceability and calibration date. If the torque wrench is not calibrated, do not use it. Also, be sure to check the condition of the torque wrench. Ensure the handle is free from corrosion, no sign of crack and damage on the mirror, and common parts of the TW including load lever, pivot and square drive are always in a good condition. After that, check zeroing of TW. Ensure the needle point is set to zero. Then, test the torque wrench with a test rig to check and test its value of loading. The value on the test rig meter should tally with torque wrench meter. If it is not, do not use it as it is not calibrated and render it as unserviceable. It is vital for fastener to suit the size of the socket and to be torqued to specific torque value. If an extension is to be used, calculate the specific torque value by applying the formula, or . Finally, determine the torque wrench to be used whether it is used for heavy or light duty and ensure correct calibration either inch pound or foot pound.
The first step to tighten a nut with torque wrench is to set the required torque value. Next, check the unit whether it is correct or not. Afterwards, set the ratchet to the correct rotation direction. Before tightening the nut with torque wrench, tighten the fastener by using ring spanner first to prevent cross thread. Then, attach correct size of socket to the torque wrench and tighten the fastener to the specific value. Carefully turn the torque wrench and stop once the torque wrench produces sound of click. Immediately remove the torque wrench from the fastener.
Finally, after using the torque wrench clean it properly and apply light oil to prevent corrosion. Keep it in a case to protect it from heat and moisture.
Aircraft refueling is a process where trained personnel carried out task to fill an aircraft with fuel in order to enable the aircraft to continue its journey. Generally there two methods of refueling which is the gravity refueling and pressure refueling. Usually, pressure refueling is used when it comes to the refueling of large aircraft such as Boeing 747 and gravity fueling is used on small aircraft such as Cessna 172. This essay will describe process of pressure refueling and there are several steps and precautions that must be done by responsible personnel.
The first precaution that must be done by trained personnel before carrying out the refueling process is to refer to the specific Aircraft Maintenance Manual. Next, this operation must be carried out outside the hangar and should be in a well-ventilated area only. Make sure there are fire extinguishers nearby. This operation should be conducted by personnel who has the required knowledge. Do not operate any electrical and radio equipment in this operation. After that, park the fuel tanker obliquely so that it can be driven away from aircraft in forward direction in case of emergency and check the correct grade of fuel is used. Also, ensure there is a proper bondings and groundings between aircraft and tanker, aircraft and ground, tanker and ground, and nozzle and filler port. Do not smoke and no use of naked flame or equipment that can cause spark and ignite fuel. This operation should be conducted away from any source of fire and if there is an operation that involve with fire, it must be located 15 meters. Finally, warning sign should be displayed and posted 15 meters from the location of operation.
There are several steps of aircraft refueling and it starts with the grounding of aircraft and the fuel tanker. Do not drag the hose along the leading edge. Next, connect the fueling nozzle grounding cable to the aircraft grounding receptacle and immediately remove the filler cap. After that, insert the fuel nozzle into filler cap and commence fueling which is carried out by the suction method which is provided by the tanker. Stop fueling once the desired fuel quantity has been reached. This can be monitor from the cockpit gauge reading. Once fueling process is done, install and secure the filler cap. Remove the fueling nozzle grounding cable from the aircraft grounding receptacle, the fuel tanker from the aircraft and grounding cable from the aircraft as well as from the tanker.
Finally, ensure the fuel does not come in contact with skin, clothes and eyes. Immediately clean and wash with water and special soap if this happens and also seek for the medical attention. If there is any spillage of fuel on the ground, clean the spillage.
Towing of an aircraft is a process of moving an aircraft without the need of its own engine power. In the towing process, aircraft is towed by using a tow tractor. Aircraft towing is vital in order to allow the aircraft to continue its journey. There are several precautions, preparations and procedures of aircraft towing process.
Aircraft towing is a risky process. Hence several precautions must be concerned in order to avoid accidents. The first precaution is to ensure the tow speed must not exceed 5 mph or 8km/h and do not change the gear of the tow tug while towing. Next, extreme caution must be exercised when towing on a sloping taxiway. Then, always tow slowly to reduce shock loading on the tow bar and shear pin. After that, always move aircraft forward or rearward before initiating a turn.
Several preparations have to be done before carrying out the aircraft towing operation. Firstly, ensure the parking area is prepared for towing and the aircraft is safe to be towed. Secondly, ensure personnel who are going to carry this task wear reflected vast and radio communication device is operative. Thirdly, ensure the doors and panels are closed, attached to the aircraft and the nose wheel steering system is not engaged. Last but not least, all personnel who involved in this operation must listen to operation briefing by the Licensed Aircraft Engineer or Approval Holder.
Once all precautions and preparations have been followed, the aircraft is ready to be towed and there are several procedures that must be followed. The first procedure is to refer to Aircraft Maintenance Manual. After that, ensure the center of gravity of the aircraft is within limit. If it is not, use ballast to maintain its center of gravity within the limit. Also, check the serviceability of brake system, tyre pressure and also availability of telephonic communication. Next, switch on anti-collision light, navigational light and APU. Then, choose and use correct tow tug and tow bar with shear pin installed for specific aircraft. Once everything is ready, one licensed aircraft engineer should be the leader in charged, one personnel at the cockpit, one personnel as tow tug driver and one personnel at each wing tip. Do not remove the nose wheel chock until the aircraft brake and the aircraft brake of tow tug to the aircraft are applied. Also, the ground gear lock pin should be installed. Tow the aircraft immediately after clearance has been given from the control tower. While towing, maintain effective communication by using VHF sets or interphone. Make sure to use standard words of command only.
Once towing process is completed, apply brake and insert chock reset to the aircraft wheel. Release the parking brake, switch off all the aircraft system and disconnect all the towing equipment.
Riveting is a method of connecting two sheets of metal or fabric by inserting a metal tube through both pieces and flattens the ends. The metal tube is called a rivet. Rivet is a preferred method over welding to joint two sheets of metal due to its low cost and it is also minimized stress fractures and cracks. There are several procedures on how to joint two metals by riveting process.
First and foremost, reference to Maintenance Manual should be made by personnel who are going to carry out this task. Secondly, prepare all the tools and equipment such as pneumatic rivet gun, drill gun, hammer, center punch and bucking bar. Thirdly, check the serviceability and calibration tag of all tools and equipment.
Now, begin the process of riveting by marking out of the location to be drilled according to Engineering Drawing and immediately make a center pop on the marking out by using center punch and hammer. After that, fit drill no. 30 into pneumatic drill gun and operate it to check its running true. Then, wear safety spectacles, earmuff and start to drill the first hole. Continue to drill until the last hole and insert gripping pins in each hole. Countersunk the holes by using countersinking tools and check the depth to ensure it is correct. To check the depth, countersunk rivet is inserted in each hole and the holes should be fully flush.
As soon as the checking process is done, disassemble the 2 sheet plates of metal and deburr the edges. Remove any swarf and ensure the plates are clean. Apply jointing compound to the both plates to prevent corrosion and to tight the jointing. Reassemble the sheet metals by using gripping pin and clamp it to the bench vice. Now, take out the pneumatic rivet gun and insert a flat bottom set into the rivet gun. On the other side of the plate, hold the bucking bar and ensure it is straight to the flat bottom set of the rivet. Then, operate the pneumatic rivet gun so that it gives a hard blow to the rivet head. This will also allow the reaction of the bucking bar at the rivet tail to take place.
Once the first rivet successfully riveted, stop the riveting process and check the correct formation of the rivet before proceeding to the next hole. The width of the rivet tail should be 1.5 of its diameter and its height is 0.5 of its diameter. If the formation is correct, repeat the same procedures until the final hole.
Riveting is a method of connecting two sheets of metal or fabric by inserting a metal tube through both pieces and flattening the ends. The metal tube is called a rivet. During riveting, the rivet is inserted through a hole that has been punched or drilled in the materials to be connected. Pressure is applied to flatten, deform, or roll one or both ends. However, rivets may stretch and become loose, necessitating their removal. There are several ways to remove a broken rivet.
Reference to Maintenance Manual should be made by personnel who are going to carry out this task. Next, prepare all the tools and equipment such as drill, drift pin, hammer, wooden block, and center punch. Make sure to check the serviceability and calibration tag of all tools and equipment.
Now, begin the process of rivet removal by filing the rivet head till its flat and immediately center punched at the center of the head. Use a smaller size drill than the size of drill that was used to make the original hole in order to prevent the original hole from damage. Drill to the depth until the rivet head joins the rivet shank.
After that, insert a drift pin into the hole and lever out the rivet head. Use the same size of drift pin as the size of drill that was used to make the original hole. Then, support the material from the rear by using a wooden block and tap out the rivet shank with a drift pin and light blow hammer.
Last but not least, install and secure a new rivet with the same size and type as the original one if the hole has not been enlarged or elongated during removal process. If the hole has been enlarged beyond tolerance, the larger the size of rivet has to be used. Otherwise the part may be scrapped depending on the type, size and location of the rivet.
Aircraft jacking is a process where a part of an aircraft or the aircraft itself is lifted by mechanical devices such as single-base jack and tripod jack. Aircraft jacking is essential as the aircraft must be lifted to allow the functional check of the undercarriage system. There are several preparations and procedures in aircraft jacking operation.
The first preparation of aircraft jacking operation is to ensure jacking area is prepared for jacking operation and the aircraft is safe to be jacked. Secondly, refer to Aircraft Maintenance Manual for precautions, procedures, and operations then immediately listen to aircraft jacking briefing by Licensed Aircraft Engineer or Approval Holder. Thirdly, ensure there are sufficient manpowers for jacking operation. Now, prepare all the tools and equipment available. Make sure to choose and select the correct size and type of jack and load cell to be used and also check their serviceability and calibration date. After that, check the doors and panels to ensure they are closed and attached to the aircraft. Make sure there are no people inside of the aircraft and defuel the aircraft if necessary. Do not operate any electrical or radio equipment inside the cockpit. Check the aircraft level and stability by using plump bob. Release the aircraft brakes and ensure the ground gear lock pin is installed at all time. Jack the aircraft on a flat surface inside the hangar. If aircraft is to be jacked outside, head it to the direction of the wind.
The first procedure of aircraft jacking is to refer to specific Aircraft Maintenance Manual for jacking operation. Next, determine the aircraft center of gravity is within the limit. If it is not, use ballast to position the center of gravity. After that, insert chocks on aircraft front and rear wheels and immediately release the parking brakes. Ensure the area of aircraft to be jacked has sufficient clearance and adequate access. Head the aircraft to the direction of wind if the area of aircraft to be jacked is at outside. Ensure the ground lock pin is installed at all times and the aircraft is correctly earthed. If there are micro switches fitted, isolate it by removing the fuse.
Now, one man should be ready at each jacking point and the crew header stands in front for giving instructions. Then, each man has to fit jack pad assembly to the jacking point. If the jacking point load limits are exceeded, a load cell has to be placed in between the jack pad and adapters. Immediately raise the jack until the adapters are located centrally. Before raising the aircraft to higher level, check the jack for final alignment and to ensure the weight are evenly distributed. Remove the choke and simultaneously raise the aircraft until landing gears’ legs are 6” from the ground.
Finally, lock the mechanical lock of jack within 2 threads to the jack shoulder as the jacks are raised for safety reason. Lock the collar jack, close the hydraulic jack valve and use trestle to give the aircraft more stability.
Drilling can be defined as an implement with cutting edges or a pointed end for boring holes in hard materials, usually by a rotating abrasion or repeated blows. Drilling is vital in aviation industry as fasteners which are used to join the parts of aircraft require holes which are the result of drilling. There are several precautions and procedures of drilling process.
Drilling is a risky process. Hence, several precautions must be concerned to avoid accidents. The first precaution is to ensure the workpiece is secured against turning. Second, swarf should be removed by a brush not by hand. Third, the feeding force of drilling machine should be reduced from time to time
The first procedure in drilling process is to refer to Maintenance Manual by the personnel who are going to carry out this task. Secondly, prepare all tools and equipment and check their serviceability and calibration date. Thirdly, mark out the location to be drilled according to engineering drawing and make centre pop by using centre punch and hammer. Check the centre pop to ensure it is precise. As soon as the workpiece is ready, wear appropriate PPE including safety spectacles and earmuff. Insert drill no.40 into drill chuck and tighten the drill chuck by using chuck key. Immediately remove the chuck key before commencing drilling to prevent injuries. After that, operate the drill to check it is running true.
Now, clamp the workpiece to the drill vice straightly to the surface being drilled. Next, adjust the position of the drill vice. Switch on its power, commence drilling and press down the drill by using feed lever. Make sure to use recommended feed range. Slowly increase the feeding force and remove chips by using a brush. Meanwhile, apply suitable cutting fluid to reduce heat and friction. Continue to drill until it reaches the desired depth. Change the size of drill bit in sequence until meets the desired size of hole.
Once drilling process is completed, disconnect the power and remove the drill from the drilling machine and workpiece from the drill vice. Clean the working area and deburr the hole.
Inspection Following Lightning Strike and HIRF Protection
Lightning is a discharge of electricity between highly charge cloud formation and ground. If an aircraft is flying, lightning may strike the aircraft and cause in high voltage and current passing through the aircraft structure. Therefore, all the aircraft parts are electrically bonded in order to conduct the lightning strike away from the aircraft structure.
Generally, there are two types of damage that occur during flight. They are the strike damage which is the lightning strike discharge that enters the aircraft and static discharge damage which is the static electricity discharge that occur subsequent to the lightning strike. Strike damage usually occurs at primary and secondary control surfaces, leading edges, trailing edges, wing tips, engine, engine cowling, fuselage skin, rivets, radome. This type of damage usually cause burn markings, discolouration, clustering of holes in exterior skin, blistering on the radome and cracks on the glass fibre. Meanwhile, static discharge damage usually occurs at wing tips, trailing edges and antennae. This damage may cause burn markings, discolouration, static discharge burn out, local pitting and elongated burn holes at trailing edges.
Before beginning the inspection process, refer to AMM ATA chapter 5; time limits. Meanwhile, prepare all the tool, equipment available and listen to the inspection briefing by LAE or Approval Holder. Finally, wear appropriate PPE. Now, carry out walk around to check control surfaces in term of stiffness of bearings and hinges. After that, carry out full functional check of control surfaces to ensure their freedom of movement and full range of operation. Also, check the aircraft bonding for sign of burning and disintegration followed by fuselage skin inspection for pulled or damage rivets, burning and pitting. Subsequently, check the residual magnetism at the suspected area and demagnetized where necessary. Last but not least, carry out full functional test on the radio, radar equipment, instruments, compasses and avionic instrumentation systems. Once the inspection is done, record all the defects in aircraft Tech Log and then raise task card for further action. Then, clean all tools and equipment and return them to the tool store. Ensure the no. of tools is correct as before doing the inspections.
In conclusion, aircraft inspection following lightning strike and HIRF protection should be carried out by trained personnel in accordance to AMM ATA chapter 5; time limits.
Inspection to Be Carried Out After Aircraft Flying Through Turbulence
Occasionally, aircraft would fly through turbulence due to unexpected weather condition. During that time, aircraft may be violently tossed about and there are abrupt changes in attitude and altitude. A severe turbulence will cause large variation in airspeed indicator may cause aircraft to be temporarily out of control while for light turbulence, aircraft will experienced slight and rapid rhythmic bumpiness, without noticeable changes in attitude and altitude.
Should the aircraft fly through turbulence it will be notified by pilot and is recorded in the technical log. In this case, detailed inspection should be carried out in accordance with the procedure given in the AMM. As for preparation, torchlight and inspection should be prepared. Make sure to check their serviceability and calibration date.
Now, carry out walk around the landing gear to check for damages such as pulled and damage rivets, sheared bolts and pins. Landing gear inspection should be extended into the surrounding attachment and all joints between landing gear attachment and aircraft attachment, shock absorber mechanism and its end fitting, retraction mechanism, tyre and wheel assemblies. Also, check the aircraft brakes for any damage, cracks and distortion followed by any signal of hydraulic leakage. After that, the wing, fuselage skin and tail plane have to be checked for common damages such as skin wrinkling, damage or pulled rivets, cracks, distortion and structural attachment point damage.
Turbulence may cause fuel tank leakage, loose or sheared rivets hence inspection of wings should be extended the into its fairing, buckling, control surface system, wire, struts, pins, bolts, wing attachment and aileron attachment. This will also apply to aircraft fuselage hence aircraft fuselage inspection should be extended into its skin fairing, fillets, panels, doors and openings. As for tail plane, turbulence may also cause shear bolts and pins. Thus, tail plane inspection should be extended into its mass balance weight attachment, elevator and rudder attachment.
The engine also has to be checked at the mounting assembly, shock mounting assembly, firewall bulkhead to ensure the mountings are secured and properly attached to the main plane or pylon. Turbulence may cause damage at the mountings, pulled rivets, distortion, wrinkling, fuel or hydraulic leakage. As for control surface which is the rudder, ailerons and elevators, inspection has to be done in terms of stiffness of the bearings and hinges, damage and pulled rivets, freedom of movement, full range of travel and mass balance weight attachment. Finally, carry out the aircraft symmetry check. Once all inspections are done, record and write any defects into the Tech Log and raise task card for further actions. Do some housekeeping and clean all tools and equipment. Return them to the tool store and ensure the no. Of tool is correct as before doing the inspection.
In conclusion, inspection after aircraft flying through turbulence should be carried out by trained personnel in accordance to AMM.
Wire locking is a method of securing together two or more parts with a wire which will be installed in a way that any tendency for a part to loosen will be counteracted by an additional tightening of the wire which provides positive locking. Wire locking is an extra precaution for vital fasteners from loosening due to vibration or other forces.
Before carrying this task, reference to Module 7 task card, Maintenance Manuals and ATA chapter 20; standard practices should be made by trained personnel. Next, prepare the required tools such as wire twister, locking nut or bolt, duckbill plier, long nose plier, snip. Make sure to check their serviceability and calibration date. Since lock wiring is a critical operation, several precautions should be concerned in order to have a secure lock wiring. Firstly, wear appropriate personal protective equipment for protection. Secondly, make sure to use correct method of twisting whether it is single strand which uses one strand of wire or double twist which uses two pair or twisted wires. Thirdly, avoid abrasion and do not twist the wire too tight as this may fracture the wire due to vibration. After that, use duckbill plier for gripping the wire and prevent wires from flying into the eyes when cutting the wire. Last but not least make sure the pig tail is not protruding to prevent any injury to personnel and bend it as lower as possible.
The first procedure of wire locking is to check the condition of the fastener the size of the hole of fastener. Make sure the fastener is clean. After that, choose and select the correct size diameter and type of wire to be used and cut the wire into required length. Before begin twisting, make sure the fastener has been torque to the specific value. Then, form a loop around the bolt close to the hole and insert the wire into the hole. Twist the wire with load by fingers or twisting tool. Make sure the direction of twist is clockwise and maintain correct angle of twist which is 45 degree. Also, make sure the twist limitation is not exceeded or less than 6 to 8 twists per inch for 0.032’ wire and 8 to 12 twists per inch for 0.022” wire. Now, insert the wire into the hole of another fastener and form a pig tail by using a long nose plier. Make sure the pig tail twist must be opposite direction of the first twist (anti-clockwise) and it should be at least 3 twists or ¼ inch depending upon the size of wire. Once the wire locking process is completed, check the tension and regularity of the wire. Subsequently, clean all tools and equipment, return them to the tool store and carry put paperwork.
In conclusion, wire locking process should be carried out by trained personnel in accordance to AMM ATA chapter 20; standard practices.
Aircraft Patch Repair
Aircraft patch repair is a type of repair which is permitted in certain areas on some aircraft where aerodynamic smoothness is unimportant. The primary objective in aircraft patch repair is to restore the damaged part to its original condition and to prevent corrosion. There are several precautions and procedures in the aircraft patch repair operation.
Several precautions should be concerned when repairing the skin of the aircraft. Firstly, reference to Structural Repair Manual must be made by trained personnel for precautions, procedures, operation and security. Secondly, wear appropriate personal protective equipment to prevent any injury. Thirdly, make sure to use the same type of metal for patching the aircraft skin. Then, prepare all tools such as hacksaw blade, round file, drill gun, sheet grips and pencil. Make sure to check their serviceability and calibration date.
The first procedure of aircraft patch repair is to mark a hole at the damaged area with pencil. Secondly, drill a row of 1/8” diameter holes as close together as possible inside the penciled line. Then cut out the damaged area and by using a hacksaw blade and file the edge according to the penciled line in order to remove the rough edge of the hole. Thirdly, remove the paint from the damaged area and make a patch of the same specification and thickness as the stressed skin. Make sure the patch overlap the hole by seven times of the hole’s diameter.
After that, mark the patch plate, drill the rivet holes and immediately remove the burrs. Mark the outline of the patch plate on the skin and then place the patch in position. Using the patch plate as a template, drill the rivet holes on the aircraft skin. While drilling, use sheet grips to hold the patch. Remove the patch plate, de-burr, remove swarf and immediately etch prime it. Coat the faying surface with jointing compound, secure the bonding of the patch plate with the aircraft surface by using sheet grips and form the rivets. Finally, clean the excess jointing compound and repaint the repaired area. Once damaged aircraft skin has been patched, do some housekeeping, clean all tools and equipment and return them to the tool crib.
In conclusion, aircraft patch repair should be carried out by trained personnel in accordance to Structural Repair Manual.
Aircraft Insertion Repair
Aircraft insertion repair is a type of repair which is permitted in certain areas on some aircraft where aerodynamic smoothness is very important. This type of repair requires the fitting of a backing plate on the inside of the skin and a filling plate into the hole. There are several precautions and procedures in the aircraft insertion repair operation.
Several precautions should be concerned when repairing the skin of the aircraft. Firstly, reference to structural repair manual must be made by trained personnel for precautions, procedures, operation and security. Secondly, wear appropriate personal protective equipment to prevent any injury. Thirdly, prepare all tools such as hacksaw blade, round file, drill gun, sheet grips and pencil. Make sure to check their serviceability and calibration date.
The first procedure of aircraft insertion repair is to clean out the damaged area to a circular or rectangular shape and mark a hole at the damaged area with a pencil. If the shape is rectangular, the radius of the corner should be twice the diameter of the rivets to be used in the repair. Secondly, cut out the damaged area by using a hacksaw blade and file according to the penciled line in order to remove the rough edge of the hole. Thirdly, remove the paint from the damaged area. By using material of the same specification and thickness as the stressed skin, prepare the backing and filling plates. Filling plates should be prepared by using the cleaned out hole in the stressed skin as template. The backing plate should overlap the hole by seven times of the diameter of the hole. After that, mark the rivet positions, drill the rivet holes on the backing plate and transfer the holes from the backing plate to the aircraft skin. Make sure to remove burrs due to the drilling process. Now, etch the prime on the backing plate and filling plate and immediately apply jointing compound to the backing plate. Hold the backing plate in position with sheet grip to the aircraft skin and form the countersunk rivets.
Now, mark the position of rivet holes, drill through the filling plate and remove all burrs. Insert the filling plate and drill through the holes into the backing plate. Make sure to mark the filling plate and the stressed skin with a pencil, so that the position of the filling plate is known. Then, remove the filling plate, clean the plate from burrs and swarfs and remove all pencil lines. Last but not least, coat the mating face of the filling plate with jointing compound, secure to backing plate using sheet grip and form the countersunk rivets. Once damaged aircraft skin has been patched, do some housekeeping, clean all tools and equipment and return them to the tool crib.
In conclusion, aircraft insertion repair should be carried out by trained personnel in accordance to Structural Repair Manual.
Soldering is a process of joining 2 or more metals together by solder at lower melting point temperature then temperature of the metal to form a reliable electrical path.
Before carrying this task, refer to Module 7 task card, Maintenance Manuals and relevant instructions. Next, prepare the required tools such as soldering station, soldering iron, solder, solder sucker, cleaning agent, multimeter, insulation tester, snips, magnifying glass, drill vice. Make sure to check their serviceability and calibration date.
Soldering is a precise process and any error could damage the electronic component. In order to avoid this, several precautions must be concerned to get a successful soldering. Firstly, do not touch the tip of the soldering iron and the main flex with the tip of soldering iron. Secondly, make sure the veraboard of printed circuit board is clean. Thirdly, always return the soldering iron to its stand when it is not in used. After that, clean the tip of soldering iron with damped sponge and conduct this operation in a well-ventilated area only. Once a component has been soldered, let the joint to cool down naturally before touching. Finally, make sure to wash your hand after using a soldering iron.
Preparations of solder iron and electronic component have to be done first before carrying out the soldering process. As for solder iron, the first preparation is to set up the solder iron safely to drill vice. Next, clean the tip of SI with damped sponge. After that, operate the SI at correct temperature which is 330oc and immediately melt a little solder iron tin at the tip to prevent cold joint. Once the solder iron is ready, prepare the component by cleaning it. After that, do lead bending by using forming tool or plier and insert the leg of the component to the hole of the printed circuit board.
Begin the soldering process by holding and clamping the board firmly and safely to the drill vice. Next, bring the iron to the joint from 1 side of the lead, and solder from the other side of the lead. Make sure to sweep over the end of the lead in order to let the iron to cover the lead end. Do not push the tip onto the pad. Clean and wipe all joints then inspect for any damage and unacceptable soldering. If there is any unacceptable soldering, the joint should be desolder by solder sucker and re-work the soldering process again. As soon as soldering process is done, carry out continuity check by using multimeter and insulation test by using insulation tester.
Finally, clean all tools and equipment that have been used. Return them to the tool store and carry out paperwork.
A break in a cable stops current to flow and it is said to be an open circuit and causes high resistance across the two ends of the cable. Thus, continuity check is required to carry out to find the faulty parts. It is used to measure the continuity of the electrical circuit and other appliances.
Before carrying this task, refer to Module 7 task card, Maintenance Manuals and relevant instructions. Next, prepare the required tools such as multimeter, snips, plier, and screwdriver and check their serviceability and calibration date.
Since continuity check is a critical operation, several precautions should be concerned in order to obtain positive result. Firstly, ensure the power is switched off and circuit breaker is tripped and tagged. Secondly, disconnect all parallel path and use systematic approach in finding a break in a large circuit. The systematic approach is by trying the first half of the circuit to detect the problem. If the problem is not in the first half of the circuit, then check the other half. Thirdly, ensure the power of the meter will not cause damage to other sensitive components. Also, ensure the circuit is completed, switches are made and contact breaker is closed. Finally, check the zeroing of the analogue multimeter only.
The first procedure in continuity check is to set the digital multimeter to the OHM range. If an analogue multimeter is going to be used, set the OHM range to the lowest value. Second, study the circuit and split it into half or quarter. Select the point to be tested and apply the test leads. If high reading is obtained, high resistance or infinity across the cable indicates open circuit. It could be caused by the corroded connection or dirty contact. Then, determine the part that causes the open circuit. Immediately rectify the fault by replacing or removing the cable. Once problem has been rectified, carry out full functional check and zero or low reading should be obtained indicating closed circuit.
As soon as continuity check is done, clean all tools and equipment. Return them to the tool store and carry out paperwork.
Insulation test is a test that is used to check the insulation resistance in the ignition circuit and other high voltage circuit. There are several precautions and procedures in insulation test.
Before carrying this task, refer to Module 7 task card, Maintenance Manuals and relevant instructions. Next, prepare the required tools and equipment such as insulation tester, multimeter, plier, snips, and screw driver. Make sure to check their serviceability and calibration date. Also, check the tools and equipment physically to detect any damage and contamination. Then, operate the insulation tester at the correct rated speed. The reading should be high if the tester is disconnected and the reading should be low if the tester is connected.
Since insulation test is a critical operation, several precautions should be concerned in order to obtain positive result. Firstly, make sure the power supply is switched off and circuit breaker is tripped and tagged. Secondly, disconnect all parallel path and isolate all equipment that are supplied by the circuit. Thirdly, make sure the power of the meter will not cause damage to the other sensitive component and all earth connection are disconnect. Last but not least, ensure the circuit to be tested is completed, switches are made and contact breaker is closed.
The first procedure in insulation test is to connect the insulation tester across the end of the 2 cables and select the correct insulation test value for the system under test. If there is no insulation breakdown between the 2 cables, the reading should be high but if there is insulation breakdown between the 2 cables, the reading is low indicating a fault. Now, to determine the cable if it has insulation breakdown, the test lead should be connected to the earth and cable. If the insulation test value is less than guidance value, reduce the number of circuits. Testing should be continued until the process of eliminating fault has been identified. Once the faulty part has been identified, rectify the parts by removing or replacing the cables. As soon as insulation test is done, carry out continuity check on the pin and cable, insulation test on the pin and full functional check. Finally, clean all tools and equipment that have been used. Return them to the tool store and carry out paperwork.
It is essential that all aircraft parts connected to form a low resistance link (bonding system). Bonding is an electrical interconnection between aircraft metallic parts and earth main potential for a safe distribution of current and charges.
Before carrying this task, refer to Module 7 task card, Maintenance Manuals and relevant instructions. Next, prepare the required tools such as multimeter, snips, plier, and screwdriver and check their serviceability and calibration date. After that, short the 2 spikes of 6ft leads to a single spike of 60ft lead and immediately check the tester. The tester should read zero. If zero is not obtained, the battery needs to be checked and replaced. Then, short the 2 spikes of test leads with the screwdriver and make sure the pointer deflects to the full scale reading. Make sure to avoid pointer from hitting scale full stop too hard as this may damage the unit.
The first procedure of bonding testing is to connect the 60ft lead of the test equipment to the main earth point. Since the length of a standard bonding tester lead is 60ft, the measurement between extremities of the larger types of aircraft may have to be done by selecting one or more of the main earth points successively. In this event, the resistance value between the main earth points chosen should be checked before proceeding to check the remote point. The 6ft leads should be used to check the resistance between selected points. When the 2 probes are brought into the contact to the aircraft part, the tester should read in ohm not exceeding 0.05 ohm.
Now, connect the instrument across the bond to check the resistance and make sure the reading should not beyond the permitted value. If the reading is exceeded, the rectification should be done depending upon the type of connection. In order to provide a good electrical contact between the probes and aircraft part, the protective coating should be removed. Upon the completion of test, the protective coating should be re-applied and restored.
As soon as bonding test is done, clean all tools and bonding tester. Disconnect all leads from the points and return the bonding tester to the tool store.