Hardware Material Week 1 Test Notes PDF

**not a lot of test answers for day 4** Day 1: -​ Corrosion resistant steel tubing, CRES 304, CRES 321 or CRES 304-⅛-HARD are used for high pressure hydraulic systems for (3000 psi or more). Its higher tensile strength permits the use of tubing with thinner walls. Final install...

**not a lot of test answers for day 4** Day 1: -​ Corrosion resistant steel tubing, CRES 304, CRES 321 or CRES 304-⅛-HARD are used for high pressure hydraulic systems for (3000 psi or more). Its higher tensile strength permits the use of tubing with thinner walls. Final installation weight is not much greater than that of the thicker wall aluminum alloy tubing. (used in fire zones) -​ Titanium 3AL-2.5V is used for transport category and high performance aircraft hydraulic systems. -​ Titanium is 30% stronger than steel and 50% lighter than steel -​ Cryofit fittings or swaged fittings are used with titanium tubing -​ DO NOT use titanium tubing and fitting in any oxygen system assembly -​ Titanium and titanium alloys are oxygen reactive -​ Before making repairs to tubing, it is important to make accurate identification of tubing materials. -​ To identify the material, compare code marking of the replacement tubing with the original marking in the tubing being replaced -​ On small aluminum tubing, the designation may be on the surface or more often it is shown by a color code, not more than 4” in width, painted at 2 ends and approx midway between ends of some tubing -​ Metal tubing is sized by outside diameter (o,d) measured fractionally in sixteenths of an inch -​ Tubings are manufactured in various thicknesses therefore it is important to know the material outside diameter and thickness of wall. Fabrication: -​ Damaged tubing, and fluid lines should be replaced with new parts whenever possible. -​ Fittings can often be salvaged. -​ Tube forming consists of four processes → cutting, bending, flaring, beading. -​ If the tubing is ¼ in diameter or larger, hard bending without the aid of tools is impractical -​ Cut tubing, ensure there is a square end and free of burrs. -​ Tubing should be cut approx 10% longer than the tube to be replaced to provide for minor variations in bending. -​ Too much pressure on the wheel at one time could deform the tubing or cause excessive burring. -​ Deburring can be done with a deburring tool -​ Use a fine-tooth file to tile the end square and smooth. Also file the end of the tube square and smooth and remove all burrs. -​ The objective of bending is to obtain a smooth bend without flattening the tube. -​ Tubing under ¼ in diameter usually can be bent without using a bending school. → for larger sizes, either hand bending or production benders are used. Hand bender  -​ Align the 2 zeros and align the mark on the tubing with the L on the form handle -​ A small amount of flattening in bends is acceptable but the small diameter of the flattened portion must not be less than 75% of the original outside diameter. -​ The radius blocks are so constructed that the radius of bend will vary with the tube diameter. (radius of bend is usually stamped on the block). -​ A filler of metallic composition or of dry sand may be used to facilitate bending, when hand or production tube benders are not available. -​ A modified version of filler method, a fusible alloy is used instead of sand. ​ → after the end is made, the alloy is again melted under hot water and removed from the tubing. -​ 55*** -​ In the case of attachment to a hose, it may be necessary to bend the rigid tube so that a clamp can be used to hold the hose onto the tube. -​ Although the use of flareless tube fittings eliminates all tube flaring, another operation referred to as pressetting is necessary prior to installation of a new flareless tube assembly. -​ the presetting operation is performed as follows: -​ Cut the tube to correct length, with the ends square, debur the inside and outside of the tube, lubricate the threads, place the fitting in a vise and hold tubing firmly, tighten the nut until the cutting edge of the sleeve grips the tube, to determine this point slowly turn the tube back and forth while tightening the nut. When the tube no longer turns the nut is ready for tightening. Final tightening, depends upon the tubing, for aluminum alloy tubing up to and including ½’’ outside diameter, tighten the nut from 1 to 11/6 turns. For steel tubing and aluminum alloy tubing over ½’’ Outside diameter, tighten 11/6 to 1 ½ turns. -​ Tags may be used in place of tap or decals -​ Lines conveying fuel may be marked FLAM -​ Lines containing toxic materials are marked TOXIC in place of FLAM -​ Lines containing physically dangerous materials, such as oxygen nitrogen, or Freon may be marked PHDAN (physically dangerous) -​ SLIDE 69 exam question on figure 9-16 Day 2: -​ Pipe threads are similar to those used in ordinary plumbing and are tapered, both internal and external. -​ When two fitting are joined (male and female) the thread taper forms a seal -​ Use care when applying thread lubricant so that the lubricant will not enter and contaminate the system. -​ Do no use lubricants on oxygen lines -​ Oxygen will react with petroleum products and can ignite (special lubricants are available for oxygen systems.  -​ Machine threads. This type of fitting is used to draw connections together or for attachment through bulkheads. -​ A flared tube connection, a crush washer, or a synthetic seal is used to make the connection fluid tight. -​ Machine threads have no taper and will not form a fluid tight seal -​ The size of these fittings is given in dash number which is equal to the nominal o.d in sixteenths of an inch. -​ When a fluid line passes through a bulkhead a bulkhead fitting should be used. -​ The end of the fitting that passes through the bulkhead is longer than the other ends, which allows a locknut to be installed. -​ Fittings attach one piece of tubing to another or to system units. -​ There are four types 1) bead and clamp. 2) flared fittings. 3) flareless fittings. 4) permanent fittings (permaswage, permalite, cyrofit) -​ The flared or flareless or permanent type fittings may be used as connectors in all systems, regardless of the pressure. -​ Fitting combinations composed of different alloys should be avoided to prevent dissimilar metal corrosion -​ Standard AN fitting are identified by their black or blue color -​ All AN steel fittings are colored black =, all AN aluminum fittings are colored blue, and aluminum bronze fittings are cadmium plated and natural in appearance. -​ AN flared and MS flareless are not interchangeable. MS flareless fittings: -​ MS flareless fittings are designed primarily for high-pressure (3000 psi) hydraulic systems that may be subjected to severe vibration or fluctuating pressure -​ The fittings consists of three parts: a body, a sleeve, and a nut -​ MS flareless fittings, the counterbore shoulder within the body, is designed with a reverse angle of 15 degrees for steel connectors and 45 degrees for aluminum fittings. -​ This reverse angle prevents inward collapse of the tubing when tightened and provides a partial sealing force. Swaged fittings: -​ A popular repair system for connecting and repairing hydraulic lines on transport category aircraft is the use of Permaswage. -​ Swaged fittings are used to join hydraulic lines in areas where routine disconnections are not required and are often used with titanium and corrosion resistant steel tubing. -​ The fittings are installed with portable hydraulically powered tooling. -​ Always use manufacturer's instructions to install swaged fittings. -​ Permalite, is a tube fitting that is mechanically attached to the tube by axial swaging Cryo fittings: -​ Many transport category aircraft use cryofit fittings to join hydraulic lines in areas where routine disconnections are not required. -​ Cryofit fittings can only be removed by cutting the tube at the sleeve, through this leaves enough room to replace it with a swaged fitting without replacing the hydraulic line.  -​ It is frequently used with titanium tubing Rigid tubing installation and inspection: -​ Never apply compound to the faces of the fitting or the flare, for it will destroy the metal-to-metal contact between the fitting and flare, a contact which is necessary to produce the seal. -​ Torque values for flare-type fittings only → always tighten fittings to the correct torque, over tightening a fitting may badly damage or completely cut off the tube flare, or it may ruin the sleeve or fitting nut. failure to tighten sufficiently may be serious as this condition may allow the line to blow out of the assembly or to leak uber system pressure. -​ The use of torque wrenches and the prescribed torque values prevents over tightening or under tightening -​ It is important that the final tightening commences at the point where the nut just begins to bottom. Use a wrench and turn the nut one-sixth turn (one flat on a hex nut) -​ It is permissible to tighten the nut an additional one-sixth turn (making a total of one third turn), should a connection leak. -​ If leakage still occurs after tightening the nut a total of one-third turn, remove the assembly and inspect the components for scores, cracks, presence of foreign material or damage from overtightening. -​ Several aircraft manufacturers include torque values in their maintenance manuls to tighten the flareless fittings. -​ Over Tightening a flareless tube nut drives the cutting edge of the sleeve deeply into the tube, causing the tube to be weakened to the point where normal in-flight vibration could cause the tube to shear. -​ CAUTION: never tighten the nut beyond one-third turn (two flats on the hex nut): this is the maximum the fitting may be tightened without the possibility of permanently damaging the sleeve and nut. -​ The damage limits for hard, thin-walled corrosion-resistant steel and titanium tubing are considerably less than aluminum. -​ When repairing a low-pressure line using a flexible fluid connection assembly, position the hose clamps carefully to prevent overhang of the clamp bends or chafing of the tightening screws on adjacent parts. -​ When replacing Rigid tubing ensure that the layout of the new line is the same as of the line being replaced. -​ Never select a path that does not require bends in the tubing. -​ A tube cannot be cut or flared accurately enough so that it can be installed without bending and still be free from mechanical strain. -​ Bends are also necessary to permit the tubing to expand or contract under temperature changes and to absorb vibration. -​ In all cases, the new tube assembly should be so formed prior to installation that it will not be necessary to pull or deflect the assembly into alignment by means of the coupling nuts. Flexible hose fluid lines: -​ Flexible hose is used in aircraft fluid systems to connect moving parts with stationary parts in locations subject to vibration or where a great amount of flexibility is needed. -​ Pure rubber is never used in the construction of flexible fluid lines. -​ Synthetic materials most commonly used in the manufacture of flexible hose are Buna-N, Neoprene, butyl, ethylene propylene diene monomer rubber (EPDM), and teflon. -​ While teflon is in a category of its own, the others are synthetic rubber. -​ Buna-N is a synthetic rubber compound which has excellent resistance to petroleum products. -​ Neoprene is a synthetic rubber compound which has an acetylene base. -​ Butyl is a synthetic rubber compound made from petroleum raw materials. It is an excellent material to use with phosphate ester base hydraulic fluid (skydrol). Do not use with petroleum products. -​ Low pressure → below 250 psi, fabric braid reinforcement -​ Medium pressure → up to 3000 psi, one wire braid reinforcement -​ High pressure → all sizes up to 3000 psi operating pressures. -​ Lay lines and identification markings consisting of lines, letters and numbers, printed on the hose. -​ Most hydraulic hoses are marked to identify its type, the quarter and year of manufacture, and a 5-digit code identifying the manufacturer. → These markings are in contrasting colored letters and numerals which indicate the natural lay (no twist) of the hose. -​ Hoses suitable for use with phosphate ester base hydraulic fluid will be marked Skydrol use. → therefore to make the correct hose selection, always refer to the applicable aircraft maintenance or parts manual. Teflon: -​ Has a broad operating temperature range of (-65 F to +450 F) -​ It is compatible with nearly every substance or agent used. -​ It offers little resistance to flow; sticky, viscous materials will not adhere to it. -​ It has less volumetric expansion than rubber and the shelf and service life is practically limitless. → Teflon; hose is flexible and designed to meet the requirements of higher operating temperatures and pressures in present aircraft systems. The hose is processed and extruded into tube shape to a desired size. It is covered with stainless steel wire, which is braided over the tube for strength and protection. The hose is unaffected by any known fuel, petroleum or synthetic base oils, alcohol, coolants or solvents. Practically unlimited storage life, greater operating temperature range, and broad usage. Medium pressure Teflon, hose assemblies are sometimes Preformed to clear obstructions and to make  connections using the shortest possible hose length. Since performing permits higher bends that eliminate the need for special elbows, preformed hose assemblies Save space and weight. Never straighten a preformed hose assembly. Use a support wire if the hose is to be removed for maintenance. Day 3: -​ The term “Cold flow” describes the deep, permanent impressions in the hose produced by the pressure of hose clamps or supports. -​ When Failure occurs in a flexible hose equipped with swaged end fittings, the entire assembly must be replaced. -​ When failure occurs in a hose equipped with reusable end fittings, a replacement line can be fabricated. Fabrication and replacement of flexible hose -​ MS-type end fittings for flexible hose are detachable and may be reused if determined to be serviceable. -​ Hydraulic, fuel, and oil lines are generally tested using hydraulic oil or water. -​ When testing with a liquid, all trapped air is bled from the assembly prior to tightenign the cap or plug. -​ When a flexible hose has been repaired or overhauled using existing hardware and a new hose material, and before the hose is installed on the aircraft, it is recommended that the hose be tested to at least 1.5 system pressure. -​ A New hose can be operationally checked after it is installed in the aircraft using system pressure. -​ The dash number is stenciled on the side of the hose and indicates the size of tubing with which the hose is compatible. -​ When the dash number of the hose corresoinds with the dash number of the tubing, the proper size hose is being used. -​ Slack — hose assemblies must not be installed in a manner that will cause a mechanical load on the hose. -​ When installing a flexible hose, provide slack or bend in the jose line from 5 to 8 percent of its total length to provide for changes in length that will occur when pressure is applied. -​ Flexible hose contracts in length and expands in diameter when pressureized. -​ Flex — when hose assemblies are subject to considerable vibration or flexing, sufficient slack must be left between rigid fittings. -​ Install the hose so that Flexing does not occur at the end. -​ The hose must remain straight for at least two hose diameters from the end fittings -​ Twisting — hoses must be installed without twisting ti avoid possible rupture of the hose or loosening of the attaching nuts. -​ Use of Swivel connections at one or both ends will relieve twist stresses. -​ Twisting of the hose can be determined from the identification stripe (Lay line) running along its length. → this stripe should not spiral around the hose.  Bending — to avoid sharp bends in the hose assembly, use elbow fittings, hose wil elbow-type end fittings, or the appropriate bend radius → Bends that are too sharp will reduce the bursting pressure of flexible hose considerably below its rated value. -​ Clearance — th whose assembly must clear all other, lines, equipment, and adjacent structure under every operating condition. -​ To ensure proper sealing of hose connections and to prevent breaking hose clamps or damaging the hose, follow the hose clamp tightening instructions carefully. → when available, use the hose clamp torque- limiting wrench. -​ These wrenches are available in calibrations of 15 and 25 in-lb limits. -​ In the absence of torque limiting wrenches, follow the finger-tight-plus-turns method. -​ Since hose connections are subject ot “cold flow” or a setting process, a follow-up tightening check should be made ofr several days after installation -​ Non-self-sealing hose — if the clamp screw cannot be tightened with the fingers, do not disturb unless leakage is evident. If leakage is present, tighten one-fourth turn. -​ self -sealing hose — if looser than finger tight, tighten to finger tight and add one-fourth turn. -​ Flexible hose should be installed so that it will be subject to a minimum of flexing during operation. Flexible hose must never be stretched tightly between 2 fittings. Although hose must be supported at least every 24 inches, closer supports are desirable. -​ The most commonly used clamps are the rubber-cushioned and plain. -​ The rubber-cushioned clamp is used to secure lines subject to vibration; the cushioning prevents chafing of the tubing. -​ The Plain-clamp is used to secure lines in areas not subject to vibration. -​ A Teflon-cushioned clamp is used in areas where the deteriorating effect of skydrol, hydraulic fluid, or fuel is expected. Because it is less resilient, it does not provide as good a vibration-damping effect as other cushion materials. -​ Use bonded clamps to secure metal hydraulic, fuel or oil lines in place. -​ Unbonded clamps should be used only for securing wiring -​ Clamps or supporting clips smaller than the o.d diameter of the hose may restrict the flow of fluid through the hose. -​ All fluid lines must be secured at specified intervals. Safetying methods -​ Safetying is the process of securing all aircraft, bolts, nuts, screws, pins, and other fasteners so that they do not work loose due to vibration. -​ The most widely used methods are safety wire, cotter pins, lockwashers, snaprings, and special nuts, such as self-locking nuts, pal nuts and jamnuts. -​ Pins; the three main types of pins used in aircraft structures are the → taper pin → flathead pin → cotter pin. -​ Pins are used in shear applicatims and for safetying.  -​ Roll pins are finding increasing uses in aircraft construction Taper pins; → plain and threaded taper pins (AN385 and AN 386) are used in joints which carry shear loads and where absence of play is essential. -​ Plain taper pin, is drilled used with a usually safetied with wire. -​ The threaded taper pin is used with a taper pin weather (AN975) and shear nut (safetied with a cotter pin or safety clip) or self-locking nut. Flathead pin; → commonly called a clevis pin, th epin is customarily installed with the head up so that the cotter pin fails or works out the pin will remain in place. Cotter pins; → the AN380 cadmium plated cotter pin is used for safetying bolts, screws, nuts, other pins, and various pplications where such safetying is necessary. -​ An381 corrosion resistant steel cotter pin is used in locations where nonmagnetic material is required or in locations where resistance to corrosion is desired. Cotter pins must be replaced after every use. Roll pins; → pressure exerted by the roll pin against the hole walls keeps it in place, until deliberately, removed with a drift punch or pin punch. Safety wiring → safety wiring is the most positive and satisfactory method of safety capscrews, studs, nuts, bolt heads and turnbuckle barrels which cannot be safetied by any other practical means. It is a method of wiring together two or more untis in such a manner that nay tendency of on to loosen is counteracted by the tightening of the wire. nuts , bolts, screws, → nuts, bolts and screws are safety wired by the single wire or double twist method. The double twist method is the most common method of safety wiring. The single wire method may be used on small screws in a closely spaced closed geometrical pattern, on parts in electrical systems, and in places that are extremely difficult to reach. Safetying methods; -​ Safety wiring should always be per conventional methods or as required by the manufacturer. -​ Slides 51-53 review on day 3. -​ When safety wiring widely spaced bolts by the double twist method, a group of three should be the maximum number in a series. -​ When wiring Closely spaced bolts the number that be be safety wired by a 24-inch length of wire is the maximum in a series.  -​ The wire is arranged so that if the bolt or screw begins to loosen, the froce applied to the wire is in the tightening direction. -​ Never over torque or loosen a torqued nut to align safety wire holes. Safety methods; Oil caps, drain cocks, and valves. -​ In the case of the oil cap, the wire is anchored to an adjacent fillister head screw. → This system applies to any other unit which must be safety wired individually. Electrical connectors: -​ under conditions of severe vibration, the coupling nut of a connector may vibrate loose, and with sufficient vibration the connector may come apart. -​ The safety wire should be as short as practicable and must be installed in such a manner that the pull on the wire is in the direction which tightens the nut on the plug. Turnbuckles; -​ The clip locking method is used on most modern aircraft. -​ Double wrap method; the double wrap method is preferred, although the single warp methods described are satisfactory. -​ Single wrap method (spiral) → spiral each of the wire ends in opposite directions around the first half of the turnbuckle barrel so that the wires cross each other twice, again spiral the two wire ends in opposite directions around the remaining half of the turnbuckle, crossing them twice. Wrap each wire end around the shank for at least four turns. After safetying, no more than three threads of the turnbuckle threaded terminal should be exposed. General safety wiring rules; -​ This pigtail must be bent back or under to prevent it from becoming a snag. -​ When castellated nuts are to be secured with safety wire, tighten the nut tot he low side of the selected torque range, continue tightening until a slot aligns with the hole. -​ All safety wires must be tight after installation, but not under such tension that normal handling or vibration will break the wire. -​ The wire must be applied so that all pull exerted by the wire tends to tighten the nut. -​ Twists should be tight and even adn the wire between the nuts as taut as possible without overtwisting. -​ The safety wire should alwaysbe installed and twisted so that the loop around the head stays down and does not tend to ome up over the bolt head causing a slack loop. Cotter pin safetying; -​ Castellated nuts are used with bolts that have been drilled for cotter pins. -​ The cotter pin should fit neatly into the hole, with very little sideplay. Snaprings;  -​ A snapring is a ring of metal, either round or flat in cross section, which is tempered to have springlike action. -​ This springlike action will hold the snapring firmly seated in a groove. -​ The external types are designed to fit in a groove around the outside of a shaft or cylinder and may be safety wired. -​ The internal types fit in a groove inside a cylinder and are never safetied. -​ A special type of pliers is designed to install each type of snapring. -​ Snaprings can be reused as ling as they retain their shape and springlike action. Day 4: Structural fasteners; -​ Unlike friction lock rivet, the mechanical lock rivet has locking collar that forms a positive lock for retention of the stem in the shank of the rivet. → this collar is seated in position during the installation -​ The mechanical lock type of self-plugging rivet can be used in the same applications as the friction lock type of rivet. -​ Figure 7-46, depicts the sequences of a typical mechanically locked blind rivet Diameters -​ Shank diameters are measured in 1/32 inch increments and are generally identified by the first dash number: -3 Grip length (1 test questions)**** -​ Grip refers to the maximum total sheet thickness to be riveted and is measured in 1/16 of an inch -​ (identified by the second dash number) -​ Each company that manufactures self-plugging (friction lock) rivets has a code number to help users obtain the correct rivet for the grip range or material thickness of a particular installation. -​ MS numbers are used for identification purposes. -​ Many special fasteners produce high strength with light weight and can be used in place of conventional AN bolts and nuts. -​ When AN bolts are tightened with the nut the bolt stretches narrowing the diameter, and then the bolt is no longer tight in the hole -​ Special fasteners eliminate this loose fit, because they are held in place by a collar that is squeezed into position. Pin (Hi-Shear) → are not of the blind type. → “access to both sides of the material is required” → pin rivets have the same shear strength as bolts of equal diameters, are about 40 percent of the weight of a bolt, and require only about one-fifth as much time for  installation as a bolt,nut and washer combination. They are approximately three times as strong as solid shank rivets. -​ Pin rivets are essentially threadless bolts -​ The pin is headed at one end and is grooved about the circumference at the other. -​ A metal collar is swaged onto the grooved end effecting a firm, tight fit. Taper-Loks -​ Are the special fasteners used in aircraft construction. -​ The taper-lok exerts a force on the walls of the hole because of its tapered shape. -​ Designed completely to fill the hole, without deforming the shank. -​ The washer head nut squeezes the metal with tremendous force against the tapered walls of the hole. → this creates radial compression around the shank and vertical compression lines as the metals are squeezed together. Hi-Tigue -​ Has a bead that encircles the bottom of its shank. -​ The bead preloads the hole it fills, resulting in increased joint strength. -​ At installation, the bead presses against the sidewall of the hole, exertign radial force hat strengthens the surrounding area. -​ Because it is preloaded, the joint is not subjected to the constant cyclic action that normally causes a joint to become cole worked and eventually fail -​ Made of aluminum, titanium, and stainless steel alloys. Special purpose fasteners -​ (Hi-Shear pin rivet) -​ The metal collar is swaged onto the grooved end effecting a firm tight fit. -​ They are essentially threadless bolts. -​ Hi-Shear rivets are installed with standard bucking bars and pneumatic riveting hammers. -​ They require the use of a special gun set, that incorporates collar swaging and trimming and a discharge port through which excess collar material is discharged. -​ At times, it may be necessary to spot-face the area under the head of the pin to ensure the head of the rivet fits tightly against the material. -​ The spotfaced area should be 1/16-inch larger in diameter than the head diameter. -​ Pin rivets may be driven from either end. Pin rivets should be inspected on both sides of material, head of rivet should not be marred and should fit tightly against the material. Removal of rivets -​ The conventional method is drilling off the head may be utilized on either end of the pin rivet. Center punching is recommended. -​ Alternate methods are, grind a chisel edge on a small pin punch to blade a width of ⅛-inch Hi-Lok fastening system -​ The threaded end of the Hi-Lok, two-piece fastener contains a hexagonal shaped recess. -​ The hex tip of an allen wrench engages the recess to prevent rotation of the pin while the collar is being installed. -​ For shear applications, the pin is made in countersunk style and in a compact protruding head style. -​ For tension applications, the MS24694 countersunk and regular protruding head styles are available