Page lI AC 43.13-1A CHG 1 1975 TABLE OF CONTENTS-Continued Paragraph Page
71. Repalr by Welded Sleeve 35
72. Repair by Bolted Sleeve 35
79. Welded-Patch Hepair 35
74. Splicing Tubing by Inner Sleeve Method 36
75. Splicing Tubing by Outer Sleeve Method 38
78. Splicing Using Larger Diameter Replacement Tubes 39
77. Repairs at Bullt-In Fuselage Fittings 40
78. Engine Mount Repairs 40
79. Landing Gear Repairs 40
80. Built-Up Tubular Wing or Tall Surface Spars 47
81. Wing and Tail Brace Struts 47
82. Repairs to Welded Parts 47
83. Stainless Steel Structure 47
81.-94. Reserved 48 Section 3. METAL REPAIR PROCEDURES
95. Riveted or Bolted Steel Truss-Type Structures 49
96. Aluminum Alloy Structures 48
97. Selection of Aluminum for Replacement Parts 50
98. Heat Treatment of Aluminum Alloy Parts 50
09. Riveting 51
100. Repair Methods and Precautions for Aluminum Structure 54
101. Repairing Cracked Members -_--
102. Steel and Aluminum Fittings --
103. Castings * 104. Selective Plating in Alrcraft Maintenance 73 *
105.-114. Reserved 73-3 Section 4. REPAIR OF LAMINATE STRUCTURES
115. General 74
110.-128. Reserved 78 Chapter 3. FABRIC COVERING Section 1. PRACTICES AND PRECAUTIONS
127. Textile Materials 81
128. Covering Practices 81
129. Preparation of the Structure for Covering .
130. Fabric Seams --
181. Covering Methods 84
132. Relnforcing Tape 86
133. Lacing 86
134. Stitch Spacing 81 185, Surface Tape (Finishing Tape) - 87
136. Special Fasteners
137.-147. Reserved 91 Section 2. DOPING
148. Application of Aircraft Dope, Epoxy, and Resins 92
149. Blushing and Use of Blush-Retarding Thinner 92
150. Number of Coats . 92
151. Technique - 93
152. Rejuvenation of Fabric 93
153. Common Dope Troubles 94
154.-164. Reserved 94
AC 43.13-1A CHO 1 Page Hi 1975 TABLE OF CONTENTS-Continued Paragraph Page Section 3. REPAIRS TO FABRIC COVERING
105. General 95
166. Repair of Tears In Fabric 95
167. Sewed Patch Repair --- 96
168. Unsewed (Doped-On) Repairs 90
160. Repair by a Doped-In Panel 90
170.-180. Reserved 97 Section 4. FABRIC TESTING 181, Testing of Fabric Covering 98
182.-102. Reserved 98 Chapter 4. CONTROL CABLES AND TERMINALS Section 1. INSPECTION AND REPAIR
193. General
184. Cable Specifications
105. Replacement of Cables
190. Mechanically Fabricated Cable Assemblies
187. Hand Fabricated Cable Assembles
188. Cable System Inspection
199. Cable Tension Adjustment 110
200. Corrosion and Rust Prevention . 110
201.-211. Reserved 111 Section 2. SAFETY METHODS FOR TURNBUCKLES
212. General
213. Double Wrap Method
214. Single Wrap Method 114
215. Special Locking Devices 119
216.-226. Reserved 114 Chapter 5. AIRCRAFT HARDWARE Section 1. IDENTIFICATION AND USE OF AIRCRAFT HARDWARE
227. Bolta 115
228. Screws 117
229. Taper Pins (AN-385 and AN-386) - 119
230. Nuts 110
231. Washers - 120
292. Types of Rivets
233. Material Applications
284. Fasteners (Cowl and Fairing)
285. Unconventional Attachments
286.-248. Reserved 122 Chapter 6. CORROSION PROTECTION
247. Types of Corrosion
248. Corrosion Protection Measures for Basic Materials
249. Construction of Corrosion Resistant Structure
250. Corrosion Removal
251. Corrosion Proofing of Landplanes and Seaplanes 127
252. Corrosion Proofing of Landplanes Converted to Seaplanes 127
258. Cleaners, Polishes, Brighteners 128 * 255-284. Reserved 254. Handling and Care of Aircraft Recovered from Water Immersion 128 * 128-8
Page Iv AC 43.13-1A CHG 1 1975 TABLE OF CONTENTS--Continued Chapter 7. IDENTIFICATION, TESTING, AND INSPECTION
OF MATERIALS Paragraph Page Section 1. IDENTIFICATION OF METALS
265. IdentIfication of Steel Stock 129
208. Interchangeability of Steel Tubing - 120
287. Identification of Aluminum 120
288.-278. Reserved 181 Section 2. TESTING OF METALS
279. Hardness Testing 132
280. Brinell Hardness Test 132
281. Rockwell Hardness Test 182
282. Vickers Hardness Test 182
283. Testing Aluminum 182
284.-294. Reserved 132 Section 3. NONDESTRUCTIVE TESTING
205. General 186
206. Inspection by Magnifying Glass After Welding 136
207. Magnetic Particle Inspection 186
208. X-Ray or Radiographic Inspection 137
299. Fluorescent Penetrant 188
300. Dye Penetrants 188
801. Ultrasonle Flaw Detection 139
802.-312. Reserved 189 Section 4. IDENTIFICATION OF FABRICS AND PLASTICS
818. Identification of Fabric 140 *
814. Identification of Plastics 140
315.-320. Reserved 140 * Section 5. CABIN INTERIOR MATERIALS, FIRE PROTECTION QUALITIES
321. Requirements for Fire Protection 140-1
922.-325. Reserved 140-1* Chapter 8. AIRCRAFT EQUIPMENT Section 1. LANDING GEAR EQUIPMENT
926. General 141
927. Inspection 141
328. Cleaning and Lubricating 145
329. Emergency Systems 145
330. Special Inspections 145
381. Retraction Tests 145
332. Tires 145 * 383. Tire Slippage - 150
834. Tire Maintenance 150 *
385.-348. Reserved 150 Section 2. LIFE PRESERVERS AND LIFERAFTS
344. General 151
345. Inspection Procedure for Life Preservers 151
346. Repair of Life Preservers 151
847. Inspection Procedure for Liferafts 151
348. Repair of Liferafts 152
849.-359. Reserved 152
AC 43.13-1A CHG 1 Page iv- 1975 TABLE OF CONTENTS-Continued Paragraph Page Section 3. MISCELLANEOUS EQUIPMENT
360. Parachutes 153
361. Safety Belta 158
382. Flares 154
863. Oxygen Systems 151
364.-374. Reserved 158
AC 43.13-1A CHG 1 1975 all highly stressed main fittings, as set forth in Chapter 7, and if necessary, take corrosion prevention measures as recommended in Chapter 6.
(3) Replace torn, kinked, or cracked fittings.
(4) Elongated or worn boltholes in fittings which were designed without bushings are not to be reamed oversize. Replace such fittings, unless the method of repair is approved by a representative of the FAA. Do not fill holes with welding rod. Acceptable methods of repairing elongated or worn boltholes in landing gear, stabilizer, interplane, or cabane-strut ends only, not originally equipped with pin plates, are shown in figure 2.36. (Also see figure 2.11 on longeron repair at fitting.)
b. Aluminum and Aluminum Alloy Fittings.
(1) Replace damaged fittings with new parts, having the same material specifications.
(2) Repairs may be made in accordance with data furnished by the aircraft manufacturer or data substantiating the method of repair may be submitted to the FAA for review.
103. CASTINGS. Damaged castings are to be replaced and not repaired unless the method of repair is specifically approved by the aircraft manufacturer or substantiating data for the repair has been reviewed by the FAA.
* 104. SELECTIVE PLATING IN AIRCRAFT MAINTE- NANCE. Selective plating is a method of depositing metal from an electrolyte to the selected area. The electrolyte is held in an absorbent material attached to an inert anode. Plating contact is made by brushing or swabbing the part (cathode) with the electrolyte-bearing anode.
a. Selective Plating Uses. This process can be utilized for any of the following reasons:
(1) To prevent or minimize disassembly, reassembly, or masking costs.
(2) Resizing worn components (plate to size).
(3) Filling in damaged or corroded areas.
(4) To plate small areas of extremely large parts.
(5) To plate electrical contacts.
(6) To plate parts too large for existing baths.
Chap 2 Page 73
(7) To supplement conventional plating.
(8) To plate components which become contaminated if immersed in a plating bath.
(9) To cadmium-plate ultra high strength steels without hydrogen embrittlement.
(10) On-site plating.
111) Reverse current applications (e.g., stain removal, deburring, etching, dynamic balancing).
b. Specifications. Selective plating (electrodeposition), when properly applied, will meet the following specifications and standards:
QQ-C-320 Chromium Plating QQ-N-290 Nickel Plating QQ-P-416 Plating, Cadmium QQ-5-365 Silver Plating 22-1-325 Zinc Plating MIL-T-10727 Tin Plating MIL-C-14550 Copper Plating MIL-G-45204 Gold Plating
c. General Requirements.
(1) Areas to be repaired by this process should be limited to reasonably small areas of large parts, although it may be desirable to plate small parts, particularly electrical or electronic parts, in their entirety.
(2) All solutions should be kept clean and free from contamination. Care should be taken to insure that the solutions are not contaminated by used anodes or other plating solutions. Brush plating solutions are not designed to remove large amounts of scale, oil, or grease. Mechanical or chemical methods should be used to remove large amounts of scale or oxide. Use solvents to remove grease or oil.
(3) Brush plating solutions are five to fifty times as concentrated as tank solutions. The current densities used range from 500 to 4,000 amps/feet?. The voltages listed on the solution bottles have been precalculated to give proper current densities. Too high a current density burns the plating, while too low a current density produces stressed deposits and low efficiencies.
Agitation is provided by anode/cathode motion.
Too fast a motion results in low efficiencies and stressed deposits; too slow a motion causes burning. A dry tool results in burnt plate, coarse grain structure, and unsound deposits. The tool* Par 102
*cannot be too wel. Solution temperatures of 110° to 120° F. are reached during operation.
(4) Materials such as stainless steel, aluminum, chromium, and nickel, which have a passive surface, will require an activating operation to remove the passive surface, During the activating process, do not use solutions that have been previously used with reverse current because of solution contamination.
d. Equipment. The power source should operate on either 110 or 220 volt alternating current (AC), 60 Hertz, single phase input. It should have a capability to produce direct current having smooth characteristics with controlled ripple and be able to output a current of at least 25 amperes at 0 to 25 volts. Minimum instrumentation of the power source should include a voltmeter, ammeter, and ampere-hour meter.
(1) The ammeter should provide a full scale reading equal to the maximum capacity of the power source with an accuracy of +5 percent of the current being measured.
(2) The voltmeter should have sufficient capacity to provide a full scale reading equal to the maximum capacity of the power source and an accuracy of +1.0 volt.
(3) An ampere-hour meter should be readable to 0.001 ampere-hour and have an accuracy of 10.01 ampere-hour.
(4) The stylus should be designed for rapid cooling and to hold anodes of various sizes and configurations. For safety, the anode holder should be insulated.
(5) The containers for holding and catching runoff solutions should be designed to the proper configuration and be inert to the specific solution.
(6) The mechanical cleaning equipment and materials should be designed and selected to prevent contamination of the parts to be cleaned.
e. Materlals. The anodes should be of highpurity dense graphite or platinum-iridium alloys.
Do not mix solutions from different suppliers.
This could result in contamination.
f. Detail Requirements. On large parts, no area greater than approximately 10 percent of the total area of the part should be plated by this process. Small parts may be partially or completely plated. Special cases exceeding these Par 104 AC 43.13-1A CHG 1 1975 or oil.
Alloys.
(1) Electroclean the area using forward (direct) current until water does not break on the surface. This electroclean process should be accomplished at 10 to 15 volts, using the appropriate electroclean solution.
(2) Rinse the area in cold clean tap water.
(3) Activate the area with reverse current, 7 to 10 volts, in conjunction with the proper activating solution until a uniform gray to black surface is obtained.
(4) Rinse thoroughly in cold, clean tap water.
(5) Immediately electroplate to color while the area is still wet, using the appropriate nickel solution.
(6) Rinse thoroughly.
(7) Immediately continue plating with any other solution to desired thickness.
(8) Rinse and dry.
k. Plating on Copper and Copper Base Alloys.
(1) Electroclean the area using forward (direct) current until water does not break on the surface. The electroclean process should be accomplished at 8 to 12 volts using the appropriate electroclean solution. * Chap 2
AC 43.13-1A CHG 1 1975 * (2) Rinse the area in cold, clean tap water.
(3) Immediately electroplate the area with any of the plating solutions except silver. Silver requires an undercoat.
(4) Rinse and dry.
I. Plating on 300 and 400 Series Stainless Steels, Nickel Base Alloys, Chrome Base Alloys, High Nickel Ferrous Alloys, Cobalt Base Allays, Nickel Plate, and Chrome Plate.
(1) Electroclean the area using forward (direct) current until water does not break on the surface. This electroclean process should be accomplished at 12 to 20 volts using the appropriate electrocleaning solution.
(2) Rinse the aren in cold, clean tap water.
(3) Activate the surface using forward (direct) current for 1 to 2 minutes using the activating solution and accomplish at 6 to 20 volts.
(4) Do not rinse.
(5) Immediately nickel flash the surface to a thickness of 0.00005 to 0.0001 inch using the appropriate nickel solution.
(6) Rinse thoroughly.
(7) Immediately continue plating with any other solution to desired thickness.
(8) Rinse and dry.
m. Plating on Low-Carbon Steels (Heat Treated to 180,000 psi).
(1) Electroclean the area using forward Break an (direct) current until water does not break on the surface. This electroclean process should be accomplished at 12 to 20 volts using the appropriate electrocleaning solution.
(2) Rinse the area in cold, clean tap water.
(3) Reverse current etch at 8 to 10 volts, using the appropriate activating solution, until a uniform gray surface is obtained.
(4) Rinse thoroughly.
(5) Immediately electroplate the part using any solutions except copper acid or silver. Both these require undercoats.
(6) Rinse and dry.
n. Plating on Cast Iron and High-Carbon Steels (Steels Heat Treated to 180,000 psi).
(1) Electroclean the area using forward (direct) current until water does not break on Chap 2 Page 73-2 the surface. This electroclean process should be accomplished at 12 to 20 volts using the appropriate electrocleaning solution.
(2) Rinse the area thoroughly in cold, clean tap water.
(3) Reverse current etch at & to 10 volts, using the appropriate etching solution, until a uniform gray is obtained.
(4) Rinse thoroughly.
(5) Remove surface smut with 15 to 25 volts using the appropriate activating solution.
(6) Rinse thoroughly.
(7) Electroplate immediately using any of the solutions except copper or ailver (both these require undercoats).
(8) Rinse and dry.
o. Plating on Ultra High Strength Steels (Heat Treated Above 180,000 psi).
(1) Electroclean the area using REVERSE current until water does not break on the surface.
This electroclean process should be accomplished at 8 to 12 volts using the appropriate electroclean solution.
(2) Rinse the area thoroughly in cold, clean tap water.
(3) Immediately electroplate the part, using either nickel, chromium, gold, or cadmium. Other metals require an undercoat of one of the above.
Plate initially at the highest voltage recommended for the solution so as to develop an initial barrier layer. Then reduce to standard voltage.
(4) Rinse and dry.
(5) Bake the part for 4 hours at 375° +25° F.
NoTE 1: Where the solution vendor provides substantiating data that hydrogen embrittlement will not result from plating with a particular solution, then a post bake is not required. This substantlating data can be in the form of alrcraft industry manufacturers' process specifications, military specifications, or other sultable data.
NoTE 2: Acid etching should be avolded, if posible. Where etching is absolutely necessary, it should always be done with reverse current.
alkallne solutions for initial deposita.
p. Dissimilar Metals and Changing Base. As a general rule, when plating two dissimilar metals, follow the plating procedure for the one with the most steps or activation. If activating* Par 104
* steps have to be mixed, use reverse current activation steps prior to forward (direct) current activation steps.
q. Plating Solution Selection.
(l) Alkaline and neutral solutions are to be used on porous base metals, white metals, highstrength steel, and for improved coating ability.
Acid solutions are to be used for rapid buildup and as a laminating structure material in conjunction with alkaline type solutions.
(2) Chrome brush plating solutions do not yield as hard a deposit as bath plating solutions.
The hardness is about 600 Brinell as compared to 1,000 Brinell for hard chrome deposited from a tank.
(3) Silver immersion deposits will form with no current flowing on most base metals from the silver brush plating solutions; such deposits have poor adhesion to the base metal. Consequently, a flash or a more noble metal should be deposited prior to silver plating to develop a good bond.
(4) In general, brush plating gives less hydrogen embrittlement and a lower fatigue strength loss than does equivalent tank deposits.
However, all brush-plated, ultra high strength steel parts (heat treated above 180,000 psi) Par 104 AC 43.13-1A CHG 1 1975 should be baked as mentioned in paragraph
104.0.(5), unless it is specifically known that embrittlement is not a factor.
r. Qualification Tests. All brush plated surfaces shall be tested for adhesion of the electrodeposit. Apply a 1-inch wide strip of Minnesota Mining and Manufacturing tape code 250, or an approved equal, with the adhesive side to the freshly plated surface. Apply the tape with heavy hand pressure and remove it with one quick motion perpendicular to the plated surface. Any plating adhering to the tape shall be cause for rejection.
s. Personnel Training for Quality Control.
Manufacturers of selective plating equipment provide training in application techniques at their facilities. Personnel performing selective plating must have adequate knowledge of the methods, techniques, and practices involved.
These personnel should be products of those training programs and certified as qualifed operators by the manufacturers of the products used, as well as by local quality control depart* ments.
105.-114. RESERVED.
Chap 2
AC 43.13-1A CHG 1 Page 73-4 1975
Page 74 AC 43.13-1A 1972 Section 4. REPAIR OF LAMINATE STRUCTURES
115. GENERAL. There is a wide variation in the composition and structural application of laminates, and it is essential that these factors be given major consideration when any restoration activities are undertaken. To a similar extent, there also exist many types of laminate structure repairs that may or may not be suitable for a given condition. For this reason, it is important that the aircraft or component manufacturer's repair data be reviewed when determining what specific type of repair is permissible and appropriate for the damage at The materials used in the repair of laminate structures must preserve the strength, weight, aerodynamic characteristics, or electrical properties of the original part or assembly. This can best be accomplished by replacing damaged material with material of identical chemical composition or a substitute approved by the manufacturer.
In order to eliminate dangerous stress concentrations, avoid abrupt changes in cross-sectional areas. Whenever possible, for scarf joints and facings, make small patches round or oval-shaped, and round the corners of large repairs. Smooth and properly contour aerodynamic surfaces.
It is recommended that test specimens be prepared at the same time that the actual repair is accomplished. These can then be subjected to a destructive test to establish the quality of the adhesive bond in the repaired part. To make this determination valid, the specimens must be assembled with the same adhesive batch mixture and subjected to curing pressure, temperature, and time identical with those in the actual repair.
a. Fiberglass Laminate Repairs. The following repairs are applicable to fiberglass laminate used for fairings, covers, cowlings, honeycomb panel facings, etc. Prior to undertaking the repair, clean the repair area thoroughly with a castile soap and warm water. Remove any paint by wet or dry sanding methods. Seed blasting may be used but caution must be exercised to not abrade the surfaces excessively.
Superficial scars, scratches, surface abrasion, or rain erosion can generally be repaired by applying one or more coats of a suitable resin, catalyzed to cure at room temperature, to the abraded surface. The number of coats required will depend upon the type of resin and severity of the damage.
Damage not exceeding the first layer or ply of fiberglass laminate can be repaired by filling with a putty consisting of a compatible roomtemperature-setting resin and clean short glass fibers. Before the resin sets, apply a sheet of cellophane over the repair area and work out any bubbles and excess resin. After the resin has cured, sand off any excess and prepare the area for refinishing.
Damage deep enough to seriously affect the strength of the laminate (usually more than the first ply or layer of fabric) may be repaired as illustrated in figure 2.37. Coat the
- DAMAGE TO FACING
DAMAGED MATERIAL
REMOVED BY SANDING , REPLACED LAMINATIONS
SANDED TO CONTOUR FIGURE 2.37.-Typical laminate (facing) repair.
Par 115 Chop 2
AC 43.13-1A 1972 in any cleaning process to avoid unnecessary breaking of the protective film, particularly at the edges of the aluminum sheet. Chromic acid and other inhibitive treatments tend to restore the oxide film.
d. More severe cleaning is necessary with intergranular corrosion (attack along grain boundaries). The mechanical removal of all corrosion products and visible delaminated metal layers must be accomplished in order to determine the extent of the destruction and to evaluate the remaining structural strength of the component. Inspection with a 5- to 10- power magnifying glass or the use of dye penetrant will assist in determining if all unsound metal and corrosion products have been removed. Grinding to blend or fair out the edges of damaged areas can best be accomplished by using aluminum oxide-impregnated rubberbase wheels. Chemically inhibit the exposed surfaces and restore chemical surface films or paint in the same manner as for other aluminum surfaces.
e. Magnesium is the most chemically active of the metals used in aircraft construction and is therefore the most difficult to protect. The prompt and complete correction of the coating failure is imperative if serious structural damage is to be avoided. Treat the corroded area with 10 percent chromic acid solution to which has been added approximately 20 drops of battery electrolyte per gallon, in the same manner as for aluminum alloys.
251. CORROSION PROOFING OF LANDPLANES AND SEAPLANES. In the repair or alteration of aircraft, use corrosion proofing materials the same as, or equivalent to, that originally applied unless the repair or alteration would result in increased susceptibility to corrosion, in which case, employ additional corrosion protection measures.
252. CORROSION PROOFING OF LANDPLANES CONVERTED TO SEAPLANES. A special problem is encountered in the conversion of landplanes to seaplanes. In general, landplanes do not receive corrosion proofing to the same extent as do seaplanes manufactured as such. Corro- Chap 6 Page 127 sion-proofing standards for landplanes converted to seaplanes are divided into two classes: (1) Necessary minimum precautions;
and (2) Recommended precautions. Regardless of such precautions, it is imperative that the exterior surfaces of seaplanes be washed with clear fresh water immediately following extended water operation, or at least once a day when operated in salty or brackish water. Wash interior surfaces of seaplanes exposed to spray, taking care to prevent damage to electrical circuits or other items subject to injury.
a. Necessary Minimum Precautions. The following procedures are considered the minimum to safeguard the airworthiness of the converted aircraft and are not in themselves intended to maintain airworthiness for an indefinite period.
(1) Unless already protected, treat exposed fittings or fittings which can be reached through inspection openings with two coats of zinc chromate primer, paralketone, nonwatersoluble heavy grease, or comparable materials.
This applies to items such as wing-root fittings, wing-strut fittings, control-surface hinges, horns, mating edges of fittings, and attach bolts, etc.
(2) Coat nonstainless control cables with grease or paralketone or other comparable protective coating, if not replaced with corrosion-resistant cables.
(3) Inspect all accessible sections of aircraft structure. Clean structural parts showing corrosion and refinish if corrosion attack is superficial. If a part is severely corroded, replace with an adequately corrosion-proofed part.
b. Recommended Precautions. The recommended precautions are those which are suggested as a means of maintaining such aircraft in condition for safe operation over extended periods of time.
(1) Provide additional inspection openings to assist in detecting corrosion. Experience has shown openings to allow inspection of lower and rearward portion of the fuselage to be particularly desirable.
(2) Incorporate additional provisions for free drainage and ventilation of all interiors to Par 250
prevent collection of moisture (scoop-type drain grommets).
(3) Protect the interior of structural steel tubing. This may be done by air and watertight sealing or by flushing with hot linseed oil and plugging the openings. Inspect tubing for miss.
ing sealing screws, presence of entrapped water, local corrosion around sealing screws, welded clusters, and bolted fittings which may be indicative of entrapped moisture.
14) Shit the fabric of fabric-covered aircraft longitudinally on the bottom of the fuselage and tail structure for access to these sections. Coat the lower structural members with zinc chromate primer (two coats); follow by a coat of dopeproof paint or wrap with cellophane tape and rejoin the fabric. This precaution is advisable within a few months after start of operation as a seaplane.
(5) Spray the interior of metal-covered wings and fuselages with an adherent corrosion inhibitor.
(6) Place bags of potassium or sodium dichromate in the bottom of floats and boat hulls to inhibit corrosion.
(7) Prevent the entry of water by sealing, as completely as possible, all openings in wings, fuselage, control-surface members, openings for control cables, tail-wheel wells, etc.
253. CLEANERS, POLISHES, BRIGHTENERS. It is important that aircraft be kept thoroughly clean of deposits containing contaminating substances such as oil, grease, dirt, and other foreign materials.
a. Materials. Avoid damage to aircraft by not using harmful cleaning, polishing, brightening, or paint-removing materials. Use only those compounds which conform to existing government or established industry specifications or products that have been specifically recommended by the aircraft manufacturer as being satisfactory for the intended application. Observe the product manufacturer's recommendations concerning use of his agent.
b. Chemical Cleaners. Chemical cleaners must be used with great care in cleaning assembled aircraft. The danger of entrapping corrosive materials in faying surfaces and crevices coun- Par 252 AC 43.13-1A CHG 1 1975 taracts any advantages in their speed and effectiveness. Use materials which are relatively neutral and easy to remove.
c. Removal of Spilled Battery Acid. In order to neutralize spilled battery acid, use sodium bicarbonate (baking soda), or sodium borate (borax) 20 percent by weight dissolved in water.
After neutralization, remove alkali salt completely with copious quantities of water to prevent corrosion. An application of acidproof paint to the structure surrounding the battery may be an effective control for this type of cor- * 254. HANDLING AND CARE OF AIRCRAFT RECOV- ERED FROM WATER IMMERSION. Aircraft which were recovered from partial or total immersion in water, including flash floods, have been allowed to air dry, in certain instances, with no safety precautions other than a cursory inspection of the aircraft exterior. The lack of an adequate cleanup of water-immersed areas may subsequently adversely affect the safety of the aircraft. That is, water immersion increases the probability of corrosive attack, the removal of lubrication, the deterioration of aircraft materials, and/or degradation of electrical and avionic equipment.
Sea water, because of salt content, is more corrosive than surface fresh water. However, fresh water may contain varying amounts of salt and, as drying occurs, the salt concentration is increased and corrosive attack accelerated.
The most important factor following recovery of an aircraft from sea or fresh water immersion is prompt action. Components of the aircraft which have been water immersed, such as the powerplant, accessories, airframe sections, actuating mechanisms, screws, bearings, working surfaces, fuel and oil systems, wiring, radio, and radar should be disassembled, to the extent considered necessary, so that the contaminants can be completely removed.
a. Initial Fresh Water/Detergent Wash. As soon as possible after the aircraft is recovered from water immersion, thoroughly wash contaminated internal and external areas of the aircraft using a water/detergent solution as follows:
(1) Mix liquid detergent (MIL-D-16791, Type I) and isopropyl alcohol (TT-I-735) in* Chap 6