AC 43.13-1A 1972
(2) Lay the cutout flat metal strip over the leading edge, and proceed to bend this metal down over the leading edge of the propeller, being careful that the metal extends an equal width on thrust and camber faces. This can be done by following the impressions of the old tipping lines. Numerous waves will occur in the metal, but these will be eliminated as the work progresses. Obtain several pieces of strong rubber tape, 4 feet long, 1/2 inch wide, and 1/16 inch thick. While forming the metal, hold it in place on the propeller by wrapping the rubber tape around the blade. Start at the tip and work inboard, being careful not to cover the pencil lines placed on the propeller which show the location of the rivet holes.
While metal is held in place, tap the leading edge with a rawhide or rubber mallet, using moderate force to make sure the metal is seated against the wood along the nose of the leading edge. Smooth the metal by hammering it with the mallet, backing up the opposite side of the blade with a laminated hardwood bucking block having an iron weight built in the center and a piece of leather fastened to the end on which the propeller bears. The block should measure about 2 by 4 inches. Start at the end of the blade and work toward the hub, moving bucking block so that it is always under the section being hammered. Continue to do this until the metal is well shaped to the profile of the propeller. Check to see that the metal has not moved from its original position.
If this happens, remove the rubber tape, reset the metal, and rewrap the rubber tape, thus forming the metal to the leading edge.
(3) With a centerpunch and a hammer, proceed to locate the old screw and rivet holes, using the pencil marks on the blade as a guide.
Punch the metal approximately 1/4 inch from the edge. After all holes have been located, remove the metal from the propeller. Drill screw and rivet holes in the metal with a 1/8-inch drill. File off burrs on the inside of the metal.
Run the drill through the original rivet holes in the propeller in order to clean them. Cut or saw slots in the metal at the original positions.
(Refer to old tipping metal for location of the slots.) Place the metal leading edges on the blades they were formed to fit, and hold them Chap 12 Page 221 in place with rubber tape. With a centerpunch as large as or slightly larger than the diameter of the screw and rivet heads, proceed to punch metal into the original countersunk holes in the wood so that the screw and rivet heads may be entered to the correct depth (not more than 1/82 inch below the surface of the metal).
Use screws and rivets of the appropriate material. Use screws one size larger than were originally in the propeller, and rivets of the solid flat countersunk-head type. Insert screws and rivets in their respective holes, and install rivets with their heads on the thrust face of the propeller. After rivets are tapped in place, cut off the excess length of the rivet, leaving 1/8 inch for heading. End cutters built up with solder to accurately measure this distance are very useful. When an assistant backs up the rivets with a steel bar 18 inches long and pointed to fit the rivet head, hammer the rivets either by hand or with a pneumatic hammer.
Screws may be driven either by hand or with an electric screwdriver.
(4) Cut the metal of the cap tip on the camber face of the propeller to the shape of the propeller tip. Bevel the edge by hand-filing and trim off flat side of metal cap so that it extends about 3/16 inch all around the tip of the propeller. Form a hardwood block to the shape of the propeller tip thrust face. Put metal tipping in place and clamp this block to the underside of the tip with a C-clamp; turn this 8/16 inch of metal up and over the camber face of the tip. Tighten and complete the lap joint.
Mount the propeller blade solidly, with the thrust face up, on a stand supporting the blade at several points along its radius. With a hammer and a flat-faced tool, proceed to smooth the metal, starting at the nose of the leading edge and working toward the edge of the metal until all wrinkles and high spots are removed.
At the edge, use a caulking tool and, in the same manner, press the metal edge tightly against the wood. Turn the propeller over and repeat this operation on the camber face. Make sure that the thin tip is supported at all times when hammering. Apply solder over rivet and screwheads and over the metal seam of the tip of the propeller. Use 50-50 solder in wire form. Use muriatic acid as flux when soldering Par 569
Page 222 АС 43.13-1A 1972 brass. Use stainless steel soldering flux when rected by the the application of finish or solder soldering stainless steel tipping. File excess to the light blade. The light blade may be solder off and check the propeller balance coated with a high grade of primer allowing while doing so. Polish the metal with a fine for a finishing coat. After allowing each coat emery cloth or an abrasive drum driven by a to dry 48 hours, recheck the balance. Then, as flexible shaft. Vent the tipping by drilling may be necessary, either the required amount three holes, No. 60 drill (.040), 3/16 inch deep of finish must be removed by carefully sandin the tip end. Drill ventholes parallel to the papering or applying an additional finishing longitudinal axis of the blade. coat. Recheck the balance and sandpaper or apply additional finish as may be required to
570. REFINISHING. After repairing a blade, it is effect final balancing. Correct vertical unbalusually necessary to refinish it. In some cases it ance in fixed-pitch propellers by applying may be necessary to completely remove the old putty to the light side of the wood hub at a finish. Apply the finish, where necessary, in ac- point on the circumference approximately 90° cordance wih the recommendations of the pro- from the longitudinal centerline of the blades.
peller manufacturer, or with a material which Weigh the putty and prepare a brass plate has satisfactory adhesion and high moisture- weighing slightly more than the putty. The resistant properties. Refinishing of plastic-cov- thickness of the plate should be from 1/16 inch ered blades requires special techniques. Some to 1/8 inch, depending on the final area, and be manufacturers make this information availa- of sufficient size to accommodate the required ble through service bulletins. Refinish or re- number of fathead attaching screws. The plate paint wood blades carefully so that the balance may be made to fit on the hub face or to fit the of the entire propeller is not disturbed. Coating shape of the light side of the wood hub, and one blade heavier than the other will produce drilled and countersunk for the required numunbalance and cause a noticeable vibration ber of screws. Attach the plate and tighten all during flight. of the screws. After the plate is finally attached to the propeller, secure the screws to
571. PROPELLER BALANCING. It is always neces- the plate by soldering the screwheads and resary to check the balance of the propeller after check the propeller balance. All edges of the any repairs or refinishing. Accomplish final plate may be beveled to reduce its weight as balance on a rigid knife-edge balancing stand necessary. The drilling of holes in the proor on a suspension-type balancer in a room free peller and the insertion of lead or other matefrom air currents. There must not be any per- rial to assist in balancing will not be permitsistent tendency to rotate from any position on the balance stand, or to tilt on the suspension balancer. Horizontal unbalance may be cor- 572.-582. RESERVED.
Par 569 Chap 12
AC 43.13-1A Pago 223 1972 Section 3. REPAIR OF METAL PROPELLERS
583. GENERAL, Reject damaged blades with model numbers which are on the manufacturer's list of blades that cannot be repaired.
Follow manufacturer's recommendations in all cases, and make repairs in accordance with latest techniques and best industry practices.
584. STEEL BLADES. Due to the critical effects of surface injuries and their repair on the fatigue life of steel blades, all repairs must be made in accordance with the manufacturer's instructions.
585. ALUMINUM PROPELLER REPAIRS, Aluminum-alloy propellers and blades with dents, cuts, scars, scratches, nicks, leading-edge pitting, etc., may be repaired, provided the removal or treatment does not materially affect the strength, weight, or performance of the blade.
Remove these damages or otherwise treat as explained below unless contrary to manufacturer's instructions or recommendations. More than one injury is not sufficient cause alone for rejection of a blade. A reasonable number of repairs per blade may be made and not necessarily result in a dangerous condition, unless their location with respect to each other is such to form a continuous line of repairs that would materially weaken the blade. Suitable sandpaper or fine-cut files may be used for removing the necessary amount of metal. In each case, the area involved will be smoothly finished with No. 00 sandpaper or crocus cloth, and each blade from which any appreciable amount of metal has been removed will be properly balanced before it is used. Etch suspected cracks and all repairs as discussed in paragraph 605. To avoid removal of an excessive amount of metal, local etching should be accomplished at intervals during the process of removing suspected cracks. Upon completion of the repair, carefully inspect the entire blade by etching or anodizing. Remove all effects of the etching process with fine emery paper. Blades identified by the manufacturer as being coldworked (shot-blasted or cold-rolled) may require peening after repair. Accomplish repair and peening operations on this type of blade in accordance with the manufacturer's instructions. However, it is not permissible in any case to peen down the edges of any injury wherein the operation will lap metal over the
a. Round out nicks, scars, cuis, etc., occurring on the leading edge of aluminum alloy blades as shown in figure 12.2 (view B). Blades that have the leading edges pitted from normal wear in service may be reworked by removing sufficient material to eliminate the pitting. In this case, remove the metal by starting well back from the edge, as shown in figure 12.8, and working forward over the edge in such a way that the contour will remain substantially the same, avoiding abrupt changes in contour or blunt edges. Trailing edges of blades may be treated in substantially the same manner. On the thrust and camber face of blades, remove the metal around any dents, cuts, scars, scratches, nicks, longitudinal surface cracks, and pits to form shallow saucer-shaped depressions as shown in figure 12.2 (view C). Exercise care to remove the deepest point of the injury and also remove any raised metal around the edges of the injury as shown in figure 12.2 (view A).
For repaired blades, the permissible reduction in width and thickness for minimum original dimensions, allowed by the blade drawing and blade manufacturing specifications are shown in figure 12.4 for locations on the blade from the shank to 90 percent of the blade radius.
Beyond the 90 percent blade radius point, the blade width and thickness may be modified as required.
b. Shortening Blades. When the removal or treatment of defects on the tip necessitates shortening a blade, shorten each blade used Chap 12 Par 583
page
CROSS - SECTION CROSS - SECTION
BEFORE REPAIR AFTER REPAIR
BEFORE REPAIR AFTER REPAIR C
SURFACE CRACK AFTER REPAIR-
BEFORE REPAIR CRACK WORKED OUT FIGURE 12.2.—Method of repairing surface cracks, nicks, etc., on aluminum alloy propellers. AC 43.13-1A 1972
MAXIMUM THICKNESS OF BLADE
SECTION IS AT A POINT APPROX- IMATELY .3 OF CHORD LENGTH AS SHOWN.
3 OF CHORD LENGTH
CORRECT METHOD -ORIGINAL
SECTION
REWORKED
DO NOT DESTROY MAXIMUM THICKNESS OF BLADE SECTION IF POSSIBLE.
NOTE - MAINTAIN ORIGINAL RADIUS. DAMAGED 8 REWORK CONTOUR TO POINT OF MAXIMUM THICKNESS. PORTION RADIUS IS TOO LARGE.
D CONTOUR IS TOO BLUNT.
INCORRECT METHOD FIGURE 12.3.Correct and incorrect method of reworking leading edge of aluminum alloy propellers.
Page 226 AC 49.12-14 BLADE RADIUS 70 FIGURE 12.4.--Repair limits to blade section width and thickness for aluminum alloy propellers.
•REDUGTIONS SHOWN ARE THE MAXIMUM ALLOWABLE BELOW THE MINIMUM DIMENSIONS REQUIRED BY. THE BLADE DRAWING AND BLADE MANUFACTURING SPEGIFIGATION REP PER CENT 50 60 RADIUS 40 Par 585 Chap 12
Chap 12 1972 AC 43.13-1A
REFERENCE EDGE OF TEMPLATE,
PENCIL LINE DRAWN ON BLADE AT
SELECTED STATION FOR TEMPLATE
OUTLINE OF NEW REFERENCE TIP.
PLAN VIEW OF BLADE WITH DAMAGED TIP.
SHEET ALUMINUM LEADING EDGE
TIP TEMPLATE, ALLI
BLADES ON THE SAME
PROPELLER MUST BE
SHORTENED EXACTLY THE SAME.
ENLARGED SIDE VIEW OF TIP OF BLADE
•DOTTED LINE SHOWS SIDE VIEW OF NEW TIP AFTER CUTTING DOWN.
FIGURE 12.5.—Method of repairing damaged tip of aluminum alloy propellers.
Page 228 AC 43.13-1A 1972
ANGLE OF BEND
THICKNESS OF BLADE MEASURE AT A POINT OF TANGENCY TAKEN ONE INCH EACH SIDE C.L. OF BEND FIGURE 12.6.-Protractor and method of measuring angle of bend in aluminum alloy propellers.
Par 585 Chap 12
AC 43.13-1A 1972 with it and keep such sets of blades together (see figure 12.5 for acceptable methods). Mark the shortened blades to correspond with the manufacturer's system of model designation to indicate propeller diameter. In making the repair, it is not permissible to reduce the propeller diameter below the minimum diameter limit shown on the pertinent airplane specification.
c. Straightening Propeller Blades. Repair bent blades in accordance with the manufacturer's instructions. Carefully check the extent of a bend in face alinement by means of a protractor similar to the one illustrated in figure 12.6.
Only bends not exceeding 20° at 0.15-inch blade thickness to 0 degrees at 1.1-inch blade thickness may be cold straightened. Straighten blades with bends exceeding these values only upon recommendation of the manufacturer, and only at facilities having proper heat-treatment equipment. In all cases, inspect the blades (as discussed in paragraph 605) for cracks and other injuries both before and after straightening.
586. REPAIR TOLERANCES. The following tolerances are those listed in the blade manufacturing specification for aluminum alloy blades and govern the width and thickness of new blades.
These tolerances are to be used with the pertinent blade drawing to determine the minimum original blade dimensions to which the reduction of figure 12.4 may be applied. When repairs reduce the width or thickness of the blade below these limits, reject the blade. The face alignment or track of the propeller should fall within the limits recommended by the manufacturer for new propellers.
Basic diameter less than 10 feet 6 inches:
Blade width-from shank to 24-inch station + 3/64 from 24-inch station to tip $ 1/82 Blade thickness + 0.025 Basic diameter 10 feet 6 inches to less than 14 feet 0 inches:
Blade width-from shank to 24-inch station ÷ 1/16 Chap 12 Page 229 from 30-inch station to tip ÷ 1/82 Blade thickness--from shank to 24-inch station .. ...- $ 0.030 from 80-inch station to tip ‡ 0.025 Basic diameter 14 feet 0 inches and over:
Blade width-from shank to 30-inch station - ÷ 8/82 from 86-inch station to tip .. ‡ 1/16 Blade thickness-from shank to 80-inch station . + 0.040 from 86-inch station to tip .. . ... +0.085
a. No repairs are permitted to the shanks (roots or hub ends) of aluminum alloy adjustable pitch blades. The shanks must be within manufacturer's tolerances.
587. PROPELLER BALANCE. Upon completion of repairs, check horizontal and vertical balance and correct any unbalance as recommended by the manufacturer. A coaxial hole is drilled in the butt end of certain aluminum alloy detachable blades for the application of lead to obtain static horizontal balance. The size of this hole must not be increased by the repair agency.
To effect vertical balance, follow the manufacturer's specific instructions. The outside of an eccentric hole must not be closer than 1/4 inch to the nearest external blade surface. As an alternate to drilling the two holes mentioned above, the manufacturer may have drilled a single eccentric hole having a diameter and depth conforming to the eccentric hole dimensions given in the table for application of lead. The outer edge of the hole must not be closer than 1 inch to the nearest external blade surface. Finish the ends of all balancing holes with a full sized drill having a spherical end to eliminate sharp corners. Remove the sharp edges of all holes by a 1/32-inch chamfer. The following table is included for inspection information only:
Par 585
Page 230 AC 43.13-1A 1972 Size and depth of balancing holes. be used: (1) safety bolt and castellated nut, Shank centrie hole Max. con- contrle hole max. con- hole depth die. Max. eccentric (2) safety bolt (drilled head) and threaded bushing, or (3) undrilled bolt and self-locking size diameter depth inch max.
(inch) (inches) (inches) nut. Where it is desirable to use oversized 00 2% 2¼ bolts, obtain suitable aircraft standard bolts 0-V2 1/32 8% 1/16 inch larger than the original bolts. En- 1 1¾o 8 % 4¾ 4 % 4½ large the crankshaft propeller flange holes and the propeller hub holes sufficiently to accomo- 2 date the new bolts without more than 0.005- 81⅓2 6 inch clearance. Such reboring will be permitted only once. Further repairs of boltholes may be steel hubs and parts must be accomplished only 588. STEEL HUBS AND HUB PARTS. Repairs to in accordance with the methods (A) or (B) of figure 12.7.
in accordance with the manufacturer's recom- NoTe: Methods (A) or (B) are preferred over the mendations. Welding and remachining is per- oversized bolt method, because a propeller hub flange missible only when covered by manufacturer's service bulletins. redrilled in accordance with this latter method will alwavs require the redrilling of all new propellers subsequently used with the redrilled fiange.
589. PROPELLER HUB AND FLANGE REPAIR.
When the propeller boltholes in a hub or crankshaft flange for fixed-pitch propellers become damaged or oversized, it is permissible to make repairs by methods (A) or (B) in figure
12.7, or by use of aircraft standard bolts 1/16 inch larger than the original bolts. Make the repairs in accordance with the recommendations of the propeller metal hub manufacturer or the engine manufacturer as applicable. Obtain from the engine or propeller hub manufacturer suitable flange bushings with threaded or smooth bores, as illustrated in methods (A) or (B) of figure 12.7. Drill the flange and insert the bushings as recommended by the engine manufacturer. Drill the rear face of the propeller to accommodate the bushings, and protect the holes with 2 coats of aluminum paint or other high moisture-resistant coating.
Use bolts of the same size as those originally used. Any of the following combinations may
590. CONTROL SYSTEMS. Components used to control the operation of certificated propellers should be inspected, repaired, assembled, and/or tested in accordance with the manufacturer's recommendations. Only those repairs which are covered by the manufacturer's recommendations should be made, and only those replacement parts which are approved under FAR Part 21 should be used.
591, DEICING SYSTEMS. Components used in propeller deicing systems should be inspected, repaired, assembled, and/or tested in accordance with the manufacturer's recommendations. Only those repairs which are covered by the manufacturer's recommendations should be made, and only those replacement parts which are approved under FAR Part 21 should be
592.-602. RESERVED.
Par 587 Chap 12
AC 43.13-1A Page 177 1972 FrOURE 11.1.-Wire and circult protector chart. (a) High In-rush. Circuits containing incandescent lamps can draw an initial current which is 16 times greater than the continuous sauge copper Wire AN breaker amp. Circuit Fuse amp. current. Contact burning or welding may occur when switch is closed.
22 (b) Inductive. Magnetic energy stored in
7.5 solenoid coils or relays is released when the 10 control switch is opened and may appear as an 16 14 12 25 (80) 20 arc. (c) Motors. Direct current motors will 10 85 (40) draw several times their rated current during 8 50 starting, and magnetic energy stored in their 80 armature and field coils is released when the 100 control switch is opened.
125 1 (2) Switch Selection. Figure 11.2 provides 150 an approximate method for selecting the prop- Figures in parentheses may be substituted where protectors of the indicated rating are not available.
Basis of chart:
(1) Wire bundles in 185° F. ambient and altitudes up to 80,000 feet.
(2) Wire bundles of 15 or more wires, with wires carrying no more than 20 percent of the total currentcarrying capacity of the bundle as given in Specification MIL-W-5088 (A8G).
(8) Protectors in 75° to 85° P. amblent.
(4) Copper wire Specification MIL-W-5088 (A8G) or equivalent.
er nominal switch rating when the continuous load current is known. The procedure is essentially a derating to obtain reasonable switch efficiency and service life.
(3) Switch Installation. Hazardous errors in switch operation may be avoided by logical and consistent installation. Mount "on-off" two position switches so that the "on" position is reached by an upward or forward movement of the toggle. When the switch controls movable aircraft elements, such as landing gear or
(5) Circuit breakers to Specification MIL-C-6809 or FIOURE 11.2.-Switch derating factors.
equivalent.
(6) Fuses to Specification MIL-F-15160 or equivalent.
Nominal system Derating voltage Type of load factor malfunction can be hazardous, use a switch specifically designed for aircraft service. These 24 V.D.C. Lamp switches are of rugged construction and have sufficient contact capacity to break, make, and 24 V.D.C. 24 V.D.C. Inductive Relative (Beater) (Relay-Bolenold) 2 carry continuously the connected load current. 24 V.D.O. Motor 8 Snap-action design is generally preferred to 12 V.D.C. Lamp obtain rapid opening and closing of contacts ir- 12 V.D.O. Inductive respective of the speed of the operating toggle or plunger, thereby minimizing contact arcing. 12 V.D:C. 12 V.D.C. Motor Reslstive (Heater) (Relay-Solenold) 2 1 2
b. Switch Ratings.
(1) Nominal Rating. The nominal current rating of the conventional aircraft switch is usually stamped on the switch housing and represents the continuous current rating with the contacts closed. Derate switches from their nominal current rating for the following types of circuits:
NOTES :
1. To find the nominal rating of a switch to operate a given device, multiply the continuous load current required by the device by the derating factor corresponding to the voltage and type of load.
2. To find the continuous load current that a switch of a given nominal rating will handle efficiently, divide the switch nominal rating by the derating factor corresponding to the voltage and type of load.
Chap 11 Par 430
flaps, the toggle should move in the same direction as the desired motion. Inadvertent operation of switches can be prevented by mounting suitable guards over the switches.
(4) Relays, Relays are used as a switching device where a weight reduction can be achieved, or to simplify electrical controls. It Par 430 AC 43.13-18 1972 should be remembered that the relay is an electrically operated switch, and therefore subject to dropout under low system voltage conditions. Concerning contact ratings, the discussion of switch ratings in paragraph 480b (1) is generally applicable to relays,
431.-441. RESERVED.
Chap 11