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
WOOD HUB OF PROPELLER WOOD HUB OF PROPELLER {2) (1) 0 = 1/4" LARGER
THAN BOLT SIZE
METHOD (A) METHOD (B)
REPAIR OF DAMAGED OR ELONGATED BOLTHOLES IN REPAIR OF ELONGATED BOLTHOLES PROPELLER HUB FLANGES. IN PROPELLER.
(I) DRILLED BOLT WITH CASTELATED NUT OR UNDRILLED BOLT WITH SELF- LOCKING NUT.
(2) BOLT WITH HEAD DRILLED FOR SAFETY WIRING.
NOTE: PROPELLER HUS THESE REPAIRS ARE PERMITTED ONLY ON THE DRIVING FLANGE OF THE PROPELLER HUB AND THE ADJACENT FACE OF THE PROPELLER.
FIGURE 12.7.-Repair of fixed-pitch hub and propeller with elongated or damaged boltholes.
Page 332 AC 43.13-1A 1972 Section 4. OVERHAUL OF PROPELLERS 603, HUB AND HUB PARTS. Disassemble propellers submitted for overhaul and clean all hub parts in accordance with the manufacturer's recommendations. Make an inspection of the parts to determine that the critical dimensions are within the manufacturer's specified tolerances. Take particular care to check the 90° relation between shaft bore and blade socket centerline and track of the blade sockets, as these are the dimensions which are most likely to be affected by accidents. Reject and replace any hub which is sprung, worn, or damaged.
Stress risers such as cuts, nicks, or tool marks must be carefully stoned or the part rejected Carefully inspect splines and cone seats for signs of wear, and check splines with a single key "no-go" gauge made to plus 0.002 inch of the base drawing dimensions for spline land width. If the gauge enters more than 20 percent of the spline area, reject the hub. Cones and cone seats may show discoloration, pitting, and corrosion. Generally, corrosion and discolored spots may be removed by light lapping.
Pitting is not grounds for rejection, if 75 percent of the bearing area is not affected and the pitted areas are well dispersed about the cone bearing area. After cleaning, minutely inspect steel hubs and parts for cracks by the wet or dry magnetic particle method at every major overhaul period. It is not necessary to remove the plating or special external finish for this inspection unless so specified in the manufacturer's recommended practice.
Steel hubs which adapt fixed-pitch propellers to all taper crankshafts are susceptible to cracks along the keyway which often extend into the flange lightening holes. Carefully inspect these hubs by the magnetic particle method at engine overhaul periods. Any crack is cause for rejection.
604. PLATING FOR HUBS AND PARTS. Replate hubs and parts from which the plating has been removed after they have been satisfactorily inspected. All replating must be of the same material as the original plating and be done in accordance with the manufacturer's recommendations. Chrome or nickel plating is not an acceptable substitute for cadmium or zinc plating. The use of zinc chromate primer on the external surfaces followed by a coating of aluminum lacquer in lieu of cadmium plating is considered acceptable where recommended by the manufacturer. However, this type of finish will require replacement more frequently than cadmium plating.
605. INSPECTION OF ALUMINUM PROPELLERS AND BLADES. Carefully inspect aluminum propellers and blades for cracks and other injuries. A transverse (chordwise) crack or flaw of any size is cause for rejection. Refer any unusual condition or appearance revealed by these inspections to the manufacturer. Acceptable inspection methods are the acid-etching process, the anodizing process, the fluorescent penetrant process, or the dye penetrant process.
Where applicable, supplement one process with another. Etching is accomplished by immersing the blade in a warm 20 percent caustic soda solution and cleaning with a warm 20 percent nitric acid solution, with a warm water rinse between the caustic bath and the acid bath, and also a warm water rinse following the acid bath. Remove all effects of the etching by polishing. Maintain the caustic and acid solution at a temperature of from 160° F. to 180° F. Some blades incorporate parts made of steel and other materials, and the caustic soda and the nitric acid must not be allowed to come in contact with these parts. The blade surfaces are then examined with a magnifying glass of at least three-power. A crack will appear as a distinct black line. The fluorescent penetrant method is recommended as a supplement to the caustic etch for the inspection of Par 603 Chap 12