Pao 208 AC 43.13-1A 1973
PULL HERE UNTIL TIGHT
BEFORE FINISHING KNOT
CORD CROSSES
UNDER LOOS STEP • - STARTING KNOT
FINAL KNOT
STARTING KNOT
TIGHTENED
STEP & - INTERMEDIATE HALF HITCHES
FIRST PART OF FINAL STEP c - (PART I) KNOT TIGHTENED TRIM TO 3/8" MIN STEP € - (PART II) FINAL KNOT PIGURE 11.85.- -Single cord lacing.
Par 519 Chap 11
Chap 11 Par $31 the weight of pure water. 75° F.
the weight of the electrolyte as compared to electrolyte will freeze at approximately minus the battery electrolyte. The specific gravity is charged and discharged state. However, the hydrometer to determine the specific gravity of ciable chemical change takes place between the
535. CHECKING LEAD-ACID BATTERIES. Use a not as susceptible to freezing because no appreaction. Nickel-cadmium battery electrolyte is the addition of distilled water. constant discharge due to the internal chemical electrolyte is returned to the cell from which it its useful life and replacement should be con- was extracted. When a specific gravity differ- electrolyte is 1.244. Take care to assure the the corrected specific gravity reading of the sidered. Electrolyte level may be adjusted by battery, the battery is approaching the end of ence of 0.050 or more eixsts between cells of a posed to cold temperatures are subject to plate mind that lead-acid batteries are subject to a prevent freeze damage, maintain the specific freezing point of electrolyte for various specific damage due to freezing of the electrolyte. The 533. BATTERY FREEZING. Lead-acid batteries ex- gravity levels is shown in figure 11.38. To gravity at a reasonably high level, bearing in established for battery electrolyte. Therefore, trolyte is 40° F. or 16 points below the norm turer as to the proper charging voltage limits.
reading is 1.260; the temperature of the elec- the recommendations of the battery manufacin figure 11.89. As an example, the hydrometer per cell found satisfactory. In all cases, follow applied to the hydrometer indication as shown construction with values of 1.4 and 1.5 volts readings, a temperature correction should be charging voltage limit varies with design and However, to determine precise specific gravity the case of nickel-cadmium batteries, the about 1.200 when tested by a hydrometer. voltage per cell should not exceed 2.85 volts. In battery will show a specific gravity reading of within the battery. For lead-acid batteries, the battery reads about 1.240 and a 2/3 discharged rate at which energy is absorbed as heat is between 1.275 and 1.300. A 1/3 discharged bient temperature and state of charge) the fully charged when the specific gravity reading cant, since this will determine (for a given amfactured lead-acid batteries are considered number of cells in the battery is also signifi-
534. TEMPERATURE CORRECTION. U.S. manu- tween maximum charging voltage and the Anally battery failure. The relationship be- + 19 - 8 1.100 lyte boiling, rapid deterioration of the cell, and +18 -10 1.125 excessive cell temperatures leading to electro- + 5 -15 1.150 ature or charging voltage limits will result in — 4 -20 1.176 storage batteries beyond their ambient temper- -85 -16 -87 -28 1.200 1.225 532. BATTERY OVERHEAT FAILURE. Operation of —80 -62 -95 -52 -82 -70 1.275 1.250 1.800 ally identified by the material used for the plates.
recommendations. Storage batteries are usu- F. o. tained in accordance with the manufacturer's ЗрeolЛo characteristics and, therefore, should be main- Frease point in aircraft. These batteries possess different pointe. batteries are the two most common types used FIGURE 11.88.-Lead-acid battery electrolyte freezing 531. GENERAL. Lead-acid and nickel-cadmium Section 8. STORAGE BATTERIES 1972 AC 43.13-1А Page 210
Par 519 Chap 11 FIGURE 11.87.-Making ties.
SQUARE KNOT- OVER BUNDLE
CLOVE HITCH & WRAP CORD TWICE FIGURE 11.36.-Double cord lacing.
FINAL KNOT STEP • INTERMEDIATE HALF HITCHES STEP b STARTING KNOT TIGHTENED.
STARTING KNOT - BOWLINE ON A BIGHT STEP a 1972 Page 209 AC 43.13-1A
AC 43.13-1A Page 211 1972 FIGURE 11.89.--Sulfuric acid temperature correction.
Blectrolyte temperature Pointe to de aubtracted or added to speoiflo gravity
• 0. •p. readinge 140 +24 +20 +18 +12 + 8 + 1
- 4
- 8 80 10 -10 -28 -20 -85 —80
536. CHECKING NICKEL-CADMIUM BATTERIES.
The state of charge of a nickel-cadmium battery cannot be determined by measuring the specific gravity of the electrolyte with a hydrometer as the electrolyte specific gravity does not change with the state of charge. The only accurate way to determine the state of charge of a nickel-cadmium battery is by a measured discharge. After the battery has been fully charged and allowed to stand for at least 2 hours, the fluid level may be adjusted, if necessary, using distilled or demineralized water.
Because the fluid level varies with the state of charge, water should never be added while the battery is installed in the aircraft. Overfilling the battery will result in electrolyte spewage during charging. This will cause corrosive effects on the cell links, self discharge of the battery, dilution of the electrolyte density, and possible blockage of the cell vents and eventual cell rupture.
CAUTION Servicing equipment used for lead-acid batteries is not to be used for servicing nickel-cadmium batteries as acid is detrimental to the proper functioning of a nickel-cadmium battery.
Chap 11
537. ELECTROLYTE CORROSION. Electrolyte spillage or leakage may result in serious corrosion of the nearby structure or control elements as both sulfuric acid and potassium hydroxide are actively corrosive. Electrolyte may be spilled during ground servicing, leaked when cell case rupture occurs, or sprayed from cell vents due to excessive charging rates. If the battery is not case enclosed, properly treat structural parts near the battery which may be affected by acid fumes. Treat all case and drain surfaces which have been affected by electrolyte with a solution of sodium bicarbonate (for acid electrolyte) or boric acid, vinegar, or a 8 percent solution of acetic acid for potassium hydroxide electrolyte.
CAUTION Serious burns will result if the electrolyte comes in contact with any part of the body. Use rubber gloves, rubber spron, and proteetive goggles when handling electrolyte. If sulphuric acid is splashed on the body neutralize with a solution of baking soda and water, and shower or flush the affected area with water. For the eyes, use an eye fountain and flush with an abundance of water.
If potassium hydroxide contacts the skin, neutralize with 3 percent acetic acid, vinegar, or lemon Juice, and wash with water.
For the eyes, wash with a weak solution of boric acid or a weak solution of vinegar and flush with water.
538. NOXIOUS FUMES. When charging rates are excessive, the electrolyte may boil to the extent that fumes containing droplets of the electrolyte are emitted through the cell vents. These fumes from lead-acid batteries may become noxious to the crewmembers and passengers; therefore, thoroughly check the venting system. Nickelcadmium batteries will emit gas near the end of the charging process and during overcharge.
The battery vent system in the aircraft should have sufficient air flow to prevent this explosive mixture from accumulating. It is often advantageous to install a jar in the battery vent discharge system serviced with an agent to neutralize the corrosive effect of battery vapora.
539. INSTALLATION PRACTICES.
a. Clean the external surface of the battery prior to installation in the aircraft.
Par 536
b. When replacing lead-acid batteries with nickel-cadmium batteries, neutralize the battery box or compartment and thoroughly flush with clear water and dry. Acid residue can be detrimental to the proper functioning of a nickel-cadmium battery.
c. Check the condition of the vent system.
d. When installing batteries in an aircraft, exercise care to prevent inadvertent shorting of the battery terminals. Serious damage to the aircraft structure can be sustained by the resultant high discharge of electrical energy.
This condition may normally be avoided by insulating the terminal posts during the installation process.
Par 539 AC 43.73-1A 1972
e. Assure the battery holddown devices are secure but not so tight as to exert excessive pressure which may cause the battery to buckle causing internal shorting of the battery.
1. If a quick disconnect type of battery connector which prohibits crossing the battery lead is not employed, assure that the aircraft wiring is connected to the proper battery terminal. Reverse polarity in an electrical system can seriously damage a battery. Assure battery cable connections are tight to prevent arcing or a high resistance connection.
540.-552. RESERVED.
Chap 11
AC 43.13-1A Page 213 1972 Chapter 12. PROPELLERS, ROTORS, AND ASSOCIATED EQUIPMENT Section 1. INSPECTION OF PROPELLERS
553. WOOD OR COMPOSITION PROPELLERS AND BLADES. Due to the nature of the wood itself, it is necessary that wood propellers and blades be inspected frequently to assure continued airworthiness. Inspect for such defects as cracks, bruises, scars, warpage, evidence of glue failure and separated laminations, sections broken off, and defects in the finish. Composition blades must be handled with the same consid-
moved from the engine at engine overhaul periods. Whenever the propeller is removed, visually inspect the rear surface for any indication of cracks. When any indications are found, disassemble the metal hub from the propeller.
Inspect the bolts for wear and cracks at the head and threads and, if cracked or worn, replace with new AN bolts. Inspect for elongated boltholes, enlarged hub bore, and check for cracks inside of bore or anywhere on the propeller. Repair propellers found with any of these defects. If no defects are found, the propeller may be reinstalled on the engine. Prior to installation, touch up with varnish all places where the finish is worn thin, scratched, or nicked. Track and balance the propeller, and coat the hub bore and boltholes with some moisture preventive such as asphalt varnish.
In case the hub flange is integral with the installed in the propeller.
b. On new fixed-pitch propeller installations, inspect bolts for tightness after first flight and after the first 25 hours of flying. Thereafter, inspect and check the bolts for tightness at least every 50 hours. No definite time interval can be specified, since bolt tightness is affected by changes in the wood caused by the moisture content in the air where the airplane is flown and stored. During wet weather, some moisture is apt to enter the propeller wood through the drilled holes in the hub. The wood swells, but since expansion is limited by the bolts extending between the two flanges, some of the wood fibers become crushed. Later, when the propeller dries out during dry weather or due to heat from the engine, a certain amount of propeller hub shrinkage takes place, and the wood no longer completely fills the space between the two hub flanges. Accordingly, the hub bolts become loose.
c. In-flight tip failures may be avoided by frequent inspections of the metal cap and leading edge strip, and the surrounding areas. Inspect for such defects as looseness or slipping, separation of soldered joints, loose screws, loose rivets, breaks, cracks, eroded sections, and corrosion. Inspect for separation between metal leading edge and cap, which would indicate the cap is moving outward in the direction of centrifugal force. This condition is often accompanied by discoloration and loose rivets. Inspect tip for cracks by grasping with hand and slightly twisting about the longitudinal blade centerline and by alightly bending the tip backward and forward. If leading edge and cap have separated, carefully inspect for cracke at this point. Cracks usually start at the leading edge of the blade. A fine line appearing in the fabric or plastic may indicate a crack in the wood.
d. Examine the wood close to the metal sleeve of wood blades for cracks extending outward on the blade. These cracks sometimes occur at the threaded ends of the lag screws, and may be an indication of internal cracking of the Chap 12 Par 553
wood. Check tightness of the lag screws, which attach the metal sleeve to the wood blade, in accordance with the manufacturer's instructions. Inspect and protect the shank areas of composition blades next to the metal sleeve in the same manner as for wood blades.
554, METAL PROPELLERS AND BLADES. Metal propellers and blades are generally susceptible to fatigue failure resulting from concentration of stresses at the bottoms of sharp nicks, cuts, and scratches, It is especially necessary, therefore, to frequently and carefully inspect them Par 553 AC 43.13-1A for such injuries. Propeller manufacturers have published service bulletins and instructions which prescribe the manner in which these inspections are to be accomplished.
555. LUBRICATION. Inspect controllable pitch propellers frequently to determine that all parts are lubricated properly. It is especially recommended that all lubrication be accomplished at the periods and in the manner specified by the propeller manufacturer.
556.-566. RESERVED.
Chap 12
AC 43.13-1A Page 215 1972 Section 2. REPAIR OF WOOD AND COMPOSITION PROPELLERS
567. GENERAL. Repair propellers in accordance with the best accepted practices and the latest techniques. Manufacturer's recommendations should in all cases be followed. It is necessary to mark the name of the manufacturer and model designation on the repaired propeller in the event original markings were removed during the repair or refiniahing operations.
filler and will not induce failure, may be filled with a mixture of glue and clean fine sawdust thoroughly worked and packed into the defect, dried, and then sanded smooth and flush with the surface of the propeller. It is very important that all loose or foreign matter be removed from the place to be filled so that a good bond of the glue to the wood is obtained.
568. REPAIR OF WOOD PROPELLERS. Carefully examine wood propellers and blades requiring repair to be sure that they can be restored to their original airworthy condition. Refer doubtful cases to the manufacturer. Carefully evaluate propellers damaged to the following extent prior to attempting a repair:
A crack or deep cut across the grain of the wood.
Split blades.
Separated laminations, except the outside laminations of fixed-pitch propellers.
More screw or rivet holes, including holes filled with dowels, than used to attach the metal leading edge strip and tip.
An appreciable warp.
An appreciable portion of wood missing.
A crack, cut, or damage to the metal shank or sleeve of blades.
Broken lag screws which attach the metal sleeve to the blade.
Oversize shaft hole in fixed-pitch propellers.
Cracks between the shaft hole and boltholes.
Cracked internal laminations.
Excessively elongated boltholes.
a. Fill small cracks parallel to the grain with glue, thoroughly worked into all portions of the cracks, dried, and then sanded smooth and flush with the surface of the propeller. This also applies to small cuts. Dents or scars which have rough surfaces, or shapes that will hold a
b. Blade Inlays. Inlays shown in figure 12.1 may be used. Make inlays of the same wood as the propeller blade; i.e., inlay a yellow birch propeller with yellow birch, not with white birch, and as near the same specific gravity as possible. Make repair joints to conform with figure 12.1 for taper of 10:1 from deepest point to feather edge or end of inlay. Measurements are taken along a straight line parallel to the grain or general slope of the surface on thrust and camber face. This rule applies also to the edge repairs. Extend grain of inlays in the same direction as the grain of the propeller laminations. Make inlays using a fishmouth, scarf, or butt joint. The permanency of the joint is in the order named, the fishmouth being preferable. Dovetail-type inlays should not be used. Do not exceed 1 large, 2 medium, or 4 small widely separated inlays per blade.
Do not overlap a trailing and a leading edge inlay more than 25 percent, as shown in figure
12.1A. Propeller blades of a thickness ratio of 12 or more may be repaired, provided the cross-grained cut does not exceed 20 percent of the chord in length and the depth of cuts does not exceed 1/8 the blade thickness at the deepest point of damage. Blades with airfoil sections less than .12 thickness ratio may be repaired if the maximum depth of damage does not exceed 1/20 of the blade section thickness at the deepest point of damage. To determine the thickness ratio for a propeller blade, divide the maximum thickness of the airfoil section by the blade chord at the 8/4 radius station.
Chap 12 Par 567
Page 216 AC 43.13-1A 1972 Example 1.
Given 6" Chord .72 Maximum thickness of airfoil section Computation .72 + 6 = .12 thickness ratio Example shows the blade thickness ratio to be 12; therefore, an inlay ⅛ of blade thickness at the point of damage may be inserted.
Example 2.
Given 4" Chord „36 Maximum thickness of airfoil section Computation .36 + 4 = .09 thickness ratio Example shows blade thickness ratio to be less than .12; therefore, an inlay 1/20 the blade thickness at the point of damage may be in-
fixed-pitched propellers which would exceed in depth a value greater than 5 percent of the difference between the hub and bore diameters are not acceptable. In the portion of the blade where it fairs into the hub, allowable depths for inlays are dependent upon the general proportions. Where the width and thickness are both very large in proportion to the hub and blade, maximum inlay depths of 71/2 percent of the section thickness at the inlay are permissible. Where the width and thickness are excessively small, maximum inlay depths of 21/2 percent of the section thickness at the center of the inlay are permissible; for propellers over 50 horsepower, cuts 2 1/2 percent deep may be filled with glue and sawdust, while for propellers under 50 horsepower, cuts 5 percent deep may be filled with glue and sawdust.
e. Propeller Tip Repairs. In order to replace the wood worn away at the end of the metal tipping, remove enough of the metal to make the minimum repair taper 10:1 each way from the deepest point. Due to the convex leading edge of the average propeller, this taper usually works out 8:1. Repairs under the metal tipping must not exceed 71/2 percent of the chord for butt or scarf joints, and 10 percent for fishmouth joints, with 8/4 inch maximum depth for any repair. Methods of repairing or replacing propeller blade metal caps or leading edge strips are contained in paragraph 569.
The scarfing of wood tips onto a propeller blade to replace a damaged tip is not considered an acceptable repair. The success of this type of repair is fully dependent upon the strength and quality of the glue joint. Since it is difficult to apply pressure evenly over the glue area, and since no satisfactory means are available for testing the strength of such jointa, it is quite possible for defective glue joints to exist and remain undected until failure occurs.
f. Lamination Repairs. Whenever the glue joint of an outside lamination of fixed-pitch propellers is open, repair the propeller by removing the loose lamination and gluing on a new lamination of kiln dried wood of the same kind as the original lamination. It is not usually economical to attempt to repair separations between other laminations. Repair outside laminations, which have been crushed at the hub due to excessive drawing up of hub bolts, by planing and sanding one hub face smooth, removing a lamination on the other hub face and replacing it with a new lamination, thus building the hub thickness up to the original thickness. It is permissible to replace both outer laminations if necessary and feasible.
d. Blade Profiling. Narrow slivers up to 1/8 inch wide broken from the trailing edge at the wider portions of the blade may be repaired by sandpapering a new trailing edge, removing the least material possible, and fairing in a new trailing edge of smooth contour. Narrow both blades by the same amount. Near the hub or tip, use an inlay which does not exceed, at its greatest depth, 5 percent of the chord.
g. Repair of Elongated Boltholes. It is permissible to repair elongated boltholes by the insertion of a steel bushing around each bolt, as illustrated in figure 12.7. Machine the inside diameter of the bushing to fit the bolt snugly, and the outside diameter approximately 1/4 inch larger than the bolt size. Make the bushing approximately 1/2 inch long. Drill the face of the hub with a hole concentric with the bolt- Par 568 Chap 12
AC 43.13-1A Page 217 1972 NOTES:
IF INLAYS OVERLAP
LENGTHWISE, DEPTH
OF EACH IS LIM- ITED TO 1/10 THICK-
OUTLINE NESS AT DEEPEST OF INLAY MAX. LENGTH POINT OF DAMAGE.
INLAY MATERIAL
SHOULD BE THE SAME
CHECK- AS THE PROPELLER OR CRACK LAMINATIONS.
TRAILING EDGE OUTLINE OF INLAY- 10 k LEADING EDGE DAMAGE
• (CHORD AT CENTER OF REPAIR) THICKNESS AT MAX.
20 % b
DEPTH OF DAMAGE MAX. DAMAGE -INLAY REPAIR k = MAX. DEPTH OF DAMAGE m = 1/20 TO 1/8 † + • THICKNESS AT DEEPEST• MAX. DEPTH OF
POINT OF DAMAGE DAMAGE (SEE TEXT) FIGURE 12.1.-Propeller repair by addition of small inlay. (See continuation.)
Chap 12 Par 568
Page 218 AC 43.13-1A 1972 NOTES:
MAXIMUM LENGTH INLAY MATERIAL SHOULD BE
THE SAME AS PROPELLER
LAMINATIONS 2 b
OUTLINE OF DAMAGE INLAY TRAILING EDGE 10 a MAX. 25% OVERLAP OUTLINE OF 10 ₫ MAXIMUM LEADING EDGE
MAXIMUM DAMAGE- INLAY- 10 ₫ MAXIMUM
- D (CHORD AT GENTER OF REPAIR) -INLAY INLAY- FIOURE 12.1A.-Propeller repair by addition of small inlay-continued.
Par 368 Chap 12
AC 49.13-1A Page 399 1972 7 1/2 % D MAXIMUM FOR BUTT OR SOARF JOINT 10 % D MAXIMUM FOR FISHMOUTH JONT 5%% MAXIMUM FOR ALL JOINTS
BUTT JOINTS b (CHORD AT OENTER OF REPAIR)
SCARF JOINTS
TRAILING EDGE SCARF JOINTS LEADING EDGE
FISHMOUTH JOINTS FIGURE 12.1B-Propeller repair by addition of small inlay-continued.
Chap 12 Pur 368