CHG T ight parts detergent to 20 parts of dd the detergent/alcohol mixture to tap water and mix thoroughly. For ne part of the foregoing concentrate ts of tap water (warm water if availnix thoroughly.
the above specified detergent/alcohol re not available, use water emulsion ›mpound (MIL-C-43613). Add one und to nine parts water. If the MIL ompound is not available, use any ild household detergent solution with 'ater.
Precautions. The following safety i should be observed:
ctrically ground the aircraft. Attach lead to the aircraft at a point which the area that could contain explosive the landing gear of land planes is
• supporting mechanism, install a ir, jury strut, landing gear downlocks itable devices to insure that the gear ollapse. If the landing gear is not insure that the aircraft is solidly to prevent hazardous movement.
connect and remove wet- and/or dryes and isolate aircraft from all sources ty or other spark-producing devices.
lucing static electricity is generated at air hose outlets, so this method should ed for ventilating or purging fuel nove all fuel, oil, and hydraulic fluid.
sh all fuel and oil cells with clean late tires, especially on magnesium epressurize landing gear struts, pneums, and hydraulic accumulators.
scating Engines and Propellers. The would be removed from the engine and from the aircraft. The exterior of the propeller should be washed with ot or cold fresh water.
›r accessories, engine parts, etc., should I and all surfaces flushed with fresh erably hot. If facilities are available, ed parts, size permitting, should be Page 128-1 immersed in hot water or hot oil, 180° F., for a short period of time. Soft water is preferred and should be changed frequently. All parts must be completely dried by air blast or other means. If no heat drying facility is available, wipe the cleaned parts with suitable drying cloths.
Constant speed propeller mechanism should be disassembled, as required, to permit complete decontamination. Clean parts with steam or hot or cold fresh water. Dry the cleaned parts in an oven, but if a heat drying facility is not available, wipe the cleaned parts with suitable drying
d. Gas Turbine, Turboprop and Turboshaft En- The engine exhaust shield, insulation blankets, separate exhaust collectors, compressor housing, pinion cowl and/or upper pinion housing should be removed. The engine accessories, outer housing exhaust shields, and other exposed parts should be steam cleaned. The steamcleaned parts should be dried in an oven at approxímately 200° F., or with hot air from a portable engine heater, or with clean wiping cloths.
Immerse remainder of engine in 10-20 percent water solution of sodium dichromate, or hot, fresh water and apply sufficient agitation to provide complete flushing.
If immersion cannot be accomplished, flood the lower section of the compressor housing and thoroughly flush rotor blades with sodium dichromate solution or warm fresh water. Seal off combustion chamber openings and alternately fill and drain the combustion chamber with fresh water. Dry clean parts in an oven, or use dry air from a portable engine heater or wipe with suitable drying cloths.
e. Airframe. The salvageable components of the fuselage, wings, empennage, seaplane and amphibian hulls and floats, and movable surfaces should be processed as follows:
(1) The fabric from fabric-covered surfaces should be removed and replaced.
(2) The sircraft interior and exterior should be cleaned using steam under pressure with steam-cleaning compound. The steam should be directed into all seams and crevices where corrosive water may have penetrated. Avoid steam * Par 254
*cleaning electrical equipment, such as terminal boards and relays.
(3) Areas that have been steam cleaned should be rinsed immediately with either hot or cold fresh water.
(4) Touch up all scratches and scars on painted surfaces using zinc chromate primer or preservative.
(5) Undrained hollow spaces or fluid entrapment areas should be provided temporary draining facilities by drilling out rivets at lowest point. Install new rivets after drainage.
(6) All leather, fabric upholstery, and insulation should be removed and replaced. Plastic or rubber foam which cannot be cleaned of all to cleanes corrosive water should be replaced.
lar structures should be removed and the structure blown out with compressed air. If corrosive water has reached the tubular interiors, carefully flush with hot, fresh water and blow out water with compressed air. Roll the structure as necessary to remove water from pockets. Fill the tubes with hot linseed oil at approximately 180° F. Drain oil and replace drain plugs or drive screws.
(8) Clean sealed wood, metalite, and other nonmetallic areas, excluding acrylic plastics, with warm water. Wood, metalite, and other porous materials exposed to water immersion should be replaced, unless surfaces are adequately sealed to prevent penetration by corrosive water. Virtually all solvents and phenolic type cleaning agents are detrimental to acrylics and will either
f. Helicopter Rofor Dynamic Components.
(1) All evidence of corrosive water should be removed from the exterior of transmissions and gear boxes by flushing with clean hot or cold fresh water.
(2) Where it is possible that corrosive water has reached the interior of the transmission or gear boxes, remove plugs and/or covers and drain completely. Flush interior of part with hot or cold fresh water. Drain residual water, replace plugs and/or covers, and reapply proper lubricant.
g. Helicopter Blades. Except for blades with wooden or other nonmetallic constructions, treat Par 254 AC 43.1:
helicopter blades the same as propelle ciprocating engines. Clean nonmetal by hand, using warm water. Dry wi cloths or a warm air blast. When clea copter rotor blades, insure that nonsen members, such as the spars and blad are cleaned and dried.
h. Fuel and Oil Systems. Contamir and oil systems should be processed as :
(1) Flush oil system, including li water-displacing preservative.
(2) Open fuel systems. Purge cell lines. Check effectiveness of the pur combustible gas indicator. Remove bli self-sealing type fuel cells and all cal or pads.
(3) Use clean, fresh water to wash After drying, spray interior walls witł
(4) Chemically treat bare metal si cleaned aluminum tanks with 10-21 water solution of sodium dichromate.
(5) Flush fuel lines with hot water maximum). Dry, using clean, dry, a air.
1. Landing Gear. Process salvageab nents of the landing gear, wheels, and follows:
(1) Remove tires and wheels.
(2) Steam clean wheels, rinse in fr and dry.
(3) Remove wheel bearings and cl dry cleaning solvent.
(4) Immerse bearings in methyl al dry the cleaned bearings in air blast.
permit bearings to rotate during air bla Reapply proper lubricant.
(5) Remove brakes, steam clean, :
with fresh water and dry.
I. Electrical Equipment.
(1) Wet cell batteries. The risk in using wet cell batteries that have been in sea water may outweigh any ecor vantage and should be replaced.
(2) Because of possible flight haz later defects caused by progressive cor tack, all electrical wiring immersed sive water should be replaced. If
CHG 1 Page 128-3 shed or sprayed with corrosive water, ughly with clean, fresh water and dry, ressed air. Following compressed air it with water dispensing preservative 1309, Grade A).
laneous Equipment. The following should be thoroughly washed to resalt, and other contaminants. Dry last or other means, and, if required, oper lubricant:
ring and fuselage hydraulic units.
(2) Electric landing gears.
(3) Actuators.
(4) Cables.
(5) Aceumulators.
(6) Hydraulic reservoirs.
(7) Flight control.
(8) Torque tubes and bell cranks.
(9) Heating units, ducts, etc. *
255.-264. RESERVED.
Par 254
13-14 Page 129 Chapter 7. IDENTIFICATION, TESTING, AND INSPECTION
OF MATERIALS Section 1. IDENTIFICATION OF METALS IDENTIFICATION OF STEEL STOCK, The So- Numerala y of Automotive Engineers (SAE) and the Type of steels and digita erican Iron and Steel Institute (A.I.S.I.)
a numerical index system to identify the Carbon Steels ---- 1xxx position of various steels. The numbers as- Plain Carbon Steels 10Xx Free Cutting Steels 11xx ed in the combined listing of standard Manganese Steels (Manganese 1.60 to 1.90%) 18xx la issued by these groups represent the Nickel Steels 2xXX ! of steel and make it possible to readily 8.50% nickel 28xx tify the principal elements in the material. 5.00% nickel 25xx he first digit of the four number designa- Nickel Chromium Steels indicates the type to which the steel be- 8.70% nickel, 0.07% chromium
g. Thus "1" indicates a carbon steel, "2" a 1.25% nickel, 0.60% chromium 1.75% nickel, 2.00% chromium el steel, "¿" a nickel chromium steel, etc. 8.50% nickel, 1.50% chromium he case of simple alloy steels, the second Corrosion and heat resisting -. 80xXX t indicates the approximate percentage of Molybdenum Steels --. 40xx predominant alloying element. The last two Chromfum Molybdenum Steels -. SIZI ›on content. Thus the symbol "1020" indi- ts usually indicate the mean of the range of Nickel Chromium Molybdenum Steels Nickel Molybdenum Steels 1.75% nickel, 0.25% molybdenum 48xx 1ůxx s a plain carbon steel lacking a principal 8.50% nickel, 1.50% chromium 48×x ving element and containing an average of Chromium Steele БxXX percent (0.18 to 0.28) carbon. The symbol Low chromium 51xx 30" indicates a nickel steel of approxi- Medium chromium Corrosion and heat resisting 521XX 61xxx ely 8 percent (8.25 to 8.75) nickel and an Chromium Vanadium Steels - 6XІX *age of 0.30 percent, (0.28 to 0.88) carbon 1.00% chromium -- 61xx ent. The symbol "4180" indicates a chro- National Emergency Steels 8xxx m-molybdenum steel of approximately 1 Silicon Manganese Steels 9xxx 'ent (0.80 to 1.10) chromium, 0.20 percent 2.00% silicon -- 82xI 5 to 0.25) molybdenum, and 0.80 percent 8 to 0.83) carbon. The basic numbers for FIGURE 7.1.-Numerical system for steel identification.
four digit series of the carbon and alloy Is may be found in figure 7.1.
forming to Specification MIL-1-6786 are in- INTERCHANGEABILITY OF STEEL TUBING. terchangeable.
"1025" welded tubing as per Specification -T-5066 and "1025" seamless tubing conning to Specification MIL-T-5066A are inhangeable.
c. NE-8630 welded tubing conforming to Specification MIL-T-6784, and NE-8680 seamless tubing conforming to Specification MIL-T-6782 are interchangeable.
, "4130" welded tubing as per Specification 267. IDENTIFICATION OF ALUMINUM. To pro- ~T-6781, and "4180" seamless tubing con- vide a visual means for identifying the various Par 265
Page 130 AC 4 grades of aluminum and aluminum alloys, such metals are usually marked with symbols such as Government Specification Number, the temper or condition furnished, or the commercial code marking. Plate and sheet are usually marked with specification numbers or code markings in rows approximately 5 inches Nonbeat-treatable Alloye Temper designation Defnition Annealed recrystallized (wrought products only) applies to softest temper of wrought producta.
-H12 Strain-hardened one-quarter-hard temper.
-H14 Strain-hardened half-hard temper.
-H16 Strain-hardened three-quarters• hard temper.
-H18 Strain-hardened full-bard temper, -H22 Strain-bardened and partially annealed to one-quarter-bard temper.
-H24 Strain-hardened and partially annealed to balf-hard temper.
-H26 Strain-hardened and partially annealed to three-quarters-hard temper.
-1128 Strain-bardened and partially annealed to full-hard temper.
-H82 Straln-hardened and then lized. Final temper la one-quarter -H84 Strain-hardened and then stabilized. Final temper is one-half -9186 Strain-bardened and then stabilized. Final temper is three quarters hard.
-#88 Strain-bardened and then stabllized. final temper is full-hard.
-H112 As fabricated; with specified mechanical property limita.
For wrought alloys; as fabricated.
No mechanical properties limits.
For cast alloys; as cast.
apart. Tubes, bars, rods, and extruded s are marked with specification numbers or markings at intervals of 8 to 5 feet alon length of each piece. The commercial marking consists of a number which iden the particular composition of the alloy. Ir dition, letter suffixes designate the follov Heat-trentable Alloya Temper designation Dennition -0 Annealed recryatallized producta only) applies to a temper of wrought products.
-12 Annealed (castinge only).
-T8 Solution beat-treated worked by the Battening atraightening operation.
-T86 Solution heat-treated and worked by reduction of 6 per -T4 Solution heat-treated.
-T42 Solutlon heat-treated by the regardieas of prior temper plicable only to 2014 and -T5 Artifcially aged only (cas only).
-T6 Solution heat-treated and artific aged.
-782 Solution heat-treated and age user regardless of prior te (applicable only to 2014 and alloys).
-T851, -T451, Solution heat-treated and stres -T8510, -78511 lieved by stretching to produ -T4510, -T4511. permanent set of 1 to 8 per depending on the product.
-T651, -T851, Solution heat-treated, stress rel!
-76510, -T8510, by stretching to produce a I -78511, -78511. anent set of 1 to 8 percent, artificially aged.
-T852 Solution heat-treated, compress produce a permanent set and artificially aged.
-T81 Solution heat-treated, cold-wo by the fattening or straighte operation, and then artific aged.
-T86 Solution heat-treated, cold-wo by reduction of 6 percent, and artificially aged.
For wrought alloys; as fabric No mechanical properties Ill For cast alloys; as cast.
FIGURE 7.2.-Basic temper designations and subdivisions for aluminum alloys.
Par 267
3.13-1A Clad aluminum alloys have surface layers of e aluminum or corrosion-resistant alumin alloy bonded to the core material to inpit corrosion. Presence of such a coating may determined under a magnifying glass by exination of the edge surface which will show ree distinct layers.
b. Test for Distinguishing Heat-Treatable and inheat-Treatable Aluminum Alloys. If for any ason the identification mark of the alloy is t on the material, it is possible to distinguish tween some heat-treatable alloys and some nheat-treatable alloys by immersing a same of the material in a 10 percent solution of ustic soda (sodium hydroxide). Those heateated alloys containing several percent of ap 7 Page 131 copper (2014, 2017, and 2024) will turn black due to the copper content. High copper alloys when clad will not turn black on the surface, but the edges will turn black at the center of the sheet where the core is exposed. If the alloy does not turn black in the caustic soda solution it is not evidence that the alloy is not heat-treatable, as various high strength heattreatable alloys are not based primarily on the use of copper as an alloying agent. These include among others 6058, 6061, and 7075 alloys. The composition and heat-treatability of alloys which do not turn black in a caustic soda solution can be established only by chemical or spectro-analysis.
268.-278. RESERVED.
Par 267
Page 132 AC 43.
Section 2. TESTING OF METALS
279. HARDNESS TESTING. Hardness testing provides a convenient means for determining, within reasonable limits, the tensile strength of steel. It has several limitations in that it is not suitable for very soft or very hard steels.
In hardness testing, the thickness of the specimen being tested and the edge distance should be such that distortion of the metal due to these factors is eliminated. Several readings should be taken and the results averaged. In general, the higher the tensile strength, the greater is its hardness. Common methods of hardness testing are outlined in the following paragraphs. These tests are suitable for determining the tensile properties resulting from the heat treatment of steel. Care should be taken to have case hardened, corroded, pitted, decarburized, or otherwise nonuniform surfaces removed to a sufficient depth. Also, exercise caution not to cold-work and consequently harden the steel during removal of the surface.
The relationship between tensile strength and hardness is indicated in figure 7.3.
282. VICKERS HARDNESS TEST. In this test small pyramidal diamond is pressed into metal. The hardness number is the ratio of load to the surface area of indentation.
283. TESTING ALUMINUM. Hardness tests :
useful for testing aluminum alloy chiefly a means of distinguishing between anneal cold-worked, heat-treated, and heat-trea and aged material. It is of little value in in cating the strength or quality of heat tre ment. Typical hardness values for alumin alloys are shown in figure 7.4 FIGURE 7.4.-Hardness values for aluminum alloy!
Brinell numb Material commercial Eardnesa 500 kg. lom designation temper 10 mm. ball 1100 A18 8008 H16
280. BRINELL HARDNESS TEST. In this test a 2014 standard load is applied to a smooth surface of T8 185 2017 45 metal through a hardened steel ball, one centi- 18 105 meter in diameter. The numerical value of Bri- 2024 47 nell hardness is equal to the load divided by T· 120 the surface area of the resulting spherical im- 2025 T8 110 pression. 8151 100 5052 47 H86 78
281. ROCKWELL HARDNESS TEST. In this test, a 6061 80 standard minor load is applied to seat a hard- 65 ened steel ball or a diamond cone in the surface 95 of the metal, followed by the application of a 7075 185 standard major load. The hardness is meas- 7079 185 T6 185 75 ured by depth of penetration. Rockwell super- 220 T4 ficial hardness tests are made using light 0855 T6 minor and major loads and a more sensitive A856 system for measuring depth of indentation. It is useful for thinner sections, very small parts,
284.-294. RESERVED.
Par 279 Char
Rockwell, superficial bardness Brinell bardness number Rockwell hardness number number, superfielal brale 10-mm. ball, 3000-kg. load penetrator Tenaile Diamond Shore etrengths Hockwell pyramid A-scale, B-scale, D-scale, sclero- (approxi- Rockwell bardness numbers C-scale (Vickers) hardness number ard ball Stand- Kult- gren ball penetra- 60-kz. load, brale 1/16-1n. 100-kg load, diam. penetra- 100-kg. lond, brale 15-kg. 15-N acale, load 30-kg. scale, 30-N load 45-kg. 45-N load scale, hardness number всоре mate) in P. 8. 1. 1000 bardness number® C-scale tor ball tor Col. 1 Col. 2 Col. 3 Col. 4 Col. 5 Col. 6 Col. 7 Col. 8 Col. 9 Col. 10 Col. 11 Col. 12 Col. 13 Col. 14 68 -- 940 85.6 76.9 93.2 84.4 75.4 97 68 67 900 85.0 76.1 92.9 83.6 74.2 95 67 66 865 84.5 75.4 92.5 82.8 73.3 92 66 65 832 739 83.9 74.5 92.2 81.9 72.0 91 65 64 800 722 83.4 73.8 91.8 81.1 71.0 88 64 63 772 705 82.8 73.0 914 80.1 69.9 87 63 62 746 688 82.3 72.2 91.1 79.3 68.8 62 61 720 670 81.8 71.5 90.7 78.4 67.7 83 61 60 697 613 654 T18 70.7 90.2 77.5 66.6 81 60 59 674 599 $£9 1°09 6*69 8°68 76.6 65.5 80 326 59 58 653 587 919 I°08 769 £*68 75.7 64.3 78 315 58 57 633 575 969 9'62 5*89 6*88 S72 63.2 76 305 57 56 613 561 LIS 0°62 L'19 73.9 62.0 75 295 56 55 595 546 099 S81 6°99 87.9 73.0 60.9 74 287 55 54 577 534 543 0°82 1°99 #°48 72.0 59.8 72 278 54 53 560 519 £ZS F°LL 6°98 71.2 58.6 71 269 53 52 544 500 508 ZIS 8°94 9°F9 1°98 70.2 57.4 69 262 52 51 528 487 494 96₺ £94 8°89 698 69.4 56.1 68 253 51 50 513 475 481 IS₺ 6°9L T°£9 68.5 55.0 67 245 50 49 498 464 469 69₺ 1°29 0°S8 67.6 53.8 66 239 49 48 484 451 455 SS₺ LYL £₺8 66.7 52.5 64 232 48 47 471 442 443 £FT I°72 8°09 6°&8 8"99 51.4 68 225 47 46 458 432 432 ZET 9EL 0°09 S£8 8*79 50.3 62 219 46 See footnotes at end of table
FIGURE 7.3.-Rockwell C scale steel hardness numbers comparison table-continued.
Brinell hardness number Rockwell, superficial hardness 10-mm. ball, 8000-kg. load Rockwell bardness numbers number, superficial brale penetrator Tenalle Rockwell bardnede number* C-scale (Vickera) hardness Diamond pyramid number ard ball Stand- Hult- gren ball carbide Tung- sten- ball penetra- A-scale, 60-kg. load, brale B-scale, 1/16-10. 100-kg. load, diam. D-scale, 100-kg. penetra- load, brale 15-kg. scale, 15-N load 80-kg. scale. 30-N load 45-58. scale, 45-N load hardness number Shore scope sciero- strengtha (approxi- mate) in D. e. I. 1000 hardness Rockwell numbers C-scale tor ball tor Col. 1 Col. 2 Col. 3 Col. 4 Col. 5 Col. 6 Col. 1 Col. 8 Col. 9 Col. 10 Col. 11 Col. 12 Col. 13 Col. 14 446 421 421 421 731 59.2 83.0 64.0 49.0 60 212 45 434 409 409 409 725 58.5 82,5 63.1 47.8 58 206 44 423 400 400 400 72.0 57.7 82.0 62.2 46.7 57 201 43 412 390 390 390 71.5 56.9 81.5 61.3 45.5 56 196 42 402 381 381 381 70.9 56.2 80.9 60.4 44.3 55 191 41 392 371 371 371 70.4 55.4 80.4 59.5 43.1 54 186 40 382 362 362 362 69.9 54.6 79.9 58.6 41.9 52 181 39 372 353 353 353 69.4 538 79.4 57.7 40.8 51 176 38 363 344 344 344 68.9 53.1 78.8 56.8 39.6 50 172 37 354 336 336 336 68.4 (109.0) 52.3 78.3 55.9 38.4 49 168 36 345 327 327 327 67.9 (108.5) 51.5 77.7 55.0 37.2 48 168 35 336 319 319 319 67.4 (108.0) 50.8 77.2 54.2 36.1 47 159 34 327 311 311 311 66.8 (920I) 50.0 76.6 53,3 34.9 46 154 33 318 301 301 301 66.3 (107.0) 49.2 76.1 52.1 33.7 44 150 32 310 294 294 294 65.8 (106.0) 48.4 75.6 51.3 32.5 43 146 31 302 286 286 286 65.3 (105.5) 47.7 75.0 50.4 31.3 42 142 30 294 279 279 279 64.7 (104.5) 47.0 74.5 49.5 30.1 41 188 29 286 271 271 271 64.3 (104.0) 46.1 73.9 48.6 28.9 41 184 28 279 264 264 264 63.8 (103.0) 45.2 73.3 47.7 27.8 40 131 272 258 258 258 63.9 (102.5) 44.6 72.8 46.8 26.7 38 197 26 266 253 253 253 62.8 (101.5) 43.8 72.2 45.9 25.5 38 124 25 260 247 247 247 62.4 (101.0) 49.1 71.6 45.0 24.3 37 121 24 254 243 243 243 62,0 100.0 42.1 71.0 44.0 23.1 36 118 23 248 237 237 237 61.5 99.0 41.6 70.5 43.2 22.0 35 115 22 243 231 231 231 61.0 98.5 40.9 69.9 42.3 20.7 35 113 21
PIGUKE TO -доскжен ~ осас і 20_ 238 226 226 226 60.5 97. 8 40. 1 69-4 $1.5 19. 6 110 20 3.13-14
(18) - 230 219 219 219 96. 7 (18)
(16) 222 212 212 212 95. 5
(14) 213 203 203 203 93. 9
(12) 204 194 194 194 92. 3
(10) 196 187 187 187 90. 7 188 179 179 179 89. 5 180 171 171 171 87. 1
(4) 173 165 165 165 85. 5
(2) 166 158 158 158 83. 5
(0) - 160 152 152 152 81. 7 : The values in this table shown in bold-face type correspond to the values shown in the corresponding joint SAE-ABM-ASTH Committee on Hardoess Conversions as printed in ABTH E4S, table 2.
• Values in () are beyond normal range and are given for information only.
* It is possible that steels of various compositions and processing historles will deviate in hardness-tensile strength relationship from the data pres nted in this table. Above the level of Rockwell C43, deviation increases with increasing hardness and the table shall not be used above Bo 48 ercept in the absence of other data specifcally approved by the procuring agency.
Page 136 AC 43.
Section 3. NONDESTRUCTIVE TESTING
295. GENERAL, The field of NDT (nondestructive testing) and inspection is too varied to be covered in detail in this handbook. This section provides a brief description of the various methods that are available for use in aircraft maintenance. The effectiveness of any particular method of NDT inspection depends upon the skill, experience and training of the persona applying the process. Each process is limited in its usefulness as an inspection tool through its adaptability to the particular component to be inspected. Consult the aircraft or product manufacturer for specific instructions regarding NDT inspection of their product.
296. INSPECTION BY MAGNIFYING GLASS AFTER WELDING. Careful examination of all joints with a medium-power magnifying glass (at least 10-power), after first removing all scale, is considered an acceptable method of inspection for repaired structures. The practice of filling steel tubular structures with hot linseed or petroleum base oils, under pressure, in order to coat the inside surface and inhibit corrosion, assists in the detection of weld cracks, as the hot oil will seep through cracks invisible to the eye. This practice, though not justifiable in all cases, is suggested where a very large portion of the structure has been rewelded.
297. MAGNETIC PARTICLE INSPECTION. Magnetic particle inspection of Magnaflux (a patented trade name used by the Magnaflux Corp.) can be used only on magnetic materials;
l.e., iron and steel. Most stainless or high chromium nickel and manganese alloy steels, being nonmagnetic, cannot be inspected by this method. The method consists essentially of detection of discontinuities (cracks, voids, defects, pits, subsurface holes, etc.) by means of accumulation of magnetic particles on the discontinuities when the part has been magnetized. The magnetic particles are applied either dry as a powder or suspended in light oil. F complete magnetic inspection, both circu and longitudinal, magnetization should be e ployed.
CAUTION Improper operation of Magnaflux equipment be cause of faulty equipment or by untrained persons can Jeopardize the airworthinesa of parta bein inspected. Minute electrical arc burns caused durin inspection by improper operation of Magnaflu equipment, can result in eventual fallure of thi
a. Circular magnetization is produced by tral mitting an electric current directly throu the article being tested, or through a centi conductor placed through the part, in whi case defects parallel to the flow of current m be detected. As an example, circular magne zation of a round steel bar would be produc by placing the ends of the steel bar betwe the heads of the magnetic inspection machi and passing a current through the bars. Ma netic particles applied either during or aft passage of the current, or after passage of t current in magnetically retentive steels, wou disclose discontinuities parallel to the axis the bar.
b. Longitudinal magnetization is induced in part by placing the part in a strong magne!
field, such as the center of a coil. Thus, longit dinal magnetization of a round steel bar wou be produced by placing the ends of the bar t tween the heads of a magnetic-inspecti machine and placing the D.C. solenoid arou the bar. After application of the magnet particles, either during or subsequent to ma netization, discontinuities perpendicular to t axis of the bar would be disclosed.
c. Red, black, and sometimes gray particles & used in the wet or dry methods. In the case wet inspection, a fluorescent magnetic partic may also be used. This process is commercial known as Magnaglo. Articles inspected usi Par 295 Chap
atter medium are illuminated by so-called it light, and the magnetic particles glow by pescence causing any defects or indications pe easily visible. The wet inspection procee provides better control and standardiza- 1 of the concentration of magnetic particles, ier application to complex shapes, and indiions that are easier to interpret. This is due the difficulty of obtaining efficient distribu- 1 of the dry powder during magnetization.
e dry procedure is particularly suitable for ecting subsurface defects, such as, when pecting heavy welds, forgings, castings, etc.
e wet continuous process is recommended ' most aircraft work.
1. The presence of accumulations of magnetic ticles in magnetic inspection does not necesily mean that a defect exists. Changes in tion of the part, particularly where the ange in section is very sharp, and also holes illed through a part, will frequently cause fications. Surface defects are most easily deted, however, since a crack will cause a arp line of magnetic particles to appear.
surface defects are less easily detected, ice only a general collection of magnetic rticles will be observed.
e. After magnetic inspection carefully demagtize and clean the parts. Examine for possie evidence of electrical arc burns that may ‚ve occurred during inspection. All metal irticles must be removed and the serviceable irts coated with a suitable preservative.
f. Portable type magnetic particle inspection ruipment such as Sonoflux has been developed ›r use in the detection of surface or slightly ibsurface discontinuities in ferromagnetic rcraft materials and parts. This type equipent usually gives better results when the wet ispension type of indicator, such as that con- ›rming to Specification MIL-1-6868, is used ith the powder supplied by the equipment anufacturer. As in other inspection methods, ›llow the manufacturers' recommendations oncerning use of the procedure.
98. X-RAY OR RADIOGRAPHIC INSPECTION.
-ray may be used on either magnetic or nonagnetic materials for detecting subsurface lap 7 Page 137 voids such as open cracks, blowholes, etc.
When a photographic film or plate is used to record the X-ray (in a similar manner to ex- Posine posing a photographic film), the process is known as radiography. When the X-rays are prosen, t th projected through the part onto a fluorescent she echnig screen, the process is known as fluoroscopy. The technique used for radiography should be capable of indicating the presence of defects having a dimension parallel to the X-ray beam of 3 percent of the thickness of the part being radiographed for magnesium alloys, and 2 percent for all other metals and alloys. Inspection using a fluoroscopic screen is much less sensitive. Consequently, the radiographic method is usually used for inspection and the fluoroscopic method is used for culling.
a. Radiographic inspection is extensively used in the aircraft industry for the inspection of all types of castings including sand castings, permanent-mold castings, die castings, etc. X- ray is particularly useful for this application, since it is capable of disclosing defects which exist below the surface, and also since the open types of defects which may occur in castings (shrinks, blowholes, dross inclusions, etc.) are readily disclosed by proper use of X-rays. In the inspection of forged or wrought metals, on the other hand, X-ray inspection is not used so extensively. This is due to the fact that the process of forging or working may cause defects which originally existed in the metal to become tightwalled cracks. Such defects are somewhat difficult to disclose by X-rays. If doubt exists as to the suitability of the X-ray examination, consult a laboratory familiar with the X-ray examination of aircraft parts.
b. In radiography, values of peak kilovoltage, radiographic density range and penetrometer characteristics are often selected that produce less than optimum radiological data.
This selection of high kilovoltage is made in order to reduce the exposure time. The use of too high a kilovoltage reduces the resolvable detail recorded on the radiographic film. As the kilovoltage is increased, X-rays of shorter wave length and greater penetrating power are produced. This presents a sound argument for increased kilovoltages but does not take into Par 297