Par 7-195 Page 7-77 TABLE 7-13. TABLE OF NUTS (CONTINUED)
TABLE 7-14. TABLE OF WASHERS Washer Number Description Washer Humber Description AN 935 Washer, lock, M S9081 Washer, key dbl.
spring Bearing retaining AN 936 Washer, M S9274 Washer, key, obl.
tooth lock Bearing ret. Cres.
AN 950 and 955 Washer, M S9276 Washer, key, cres.
1O10 ball socket, ball seat 180° locking AMS 5510 AN 960 Washer, flat M S9320-9321 Washer, fat AMS 6350 and 5510 AN 961 Washer, M S9482 Washer, flat, flat electrical steel AM S 6437 (Brass, silver or or AMS 6485 tin-plated) diffused nickel cad.
Chak AN 970 Washer, M S9549 Washer, flat, fat, wood AMS 5510 AN 975 Washer, fat M S9581 Washer, key, cres.
AMS 5510 90° locking AN 801 3 Washer, insulator M S9582 Washer, key, cres. AMS 5510 270° locking AN 122576-122600 Washer, M S9684 Washer, cup, lock plain steel cres. AMS 5510 M S9768 Washer, flat, cres. AMS 5525 and AMS 5737 csk.
M S9880 Washer, cup, lock cres.
AMS 5510 Par 7-195 Page 7-78
TABLE 7-14. TABLE OF WASHERS (CONTINUED) Washer Number Description Washer Number Description M S9952 Washer, cup, lock, MS28777 Washer, hydraulic, spanner nut, cres. packing backup AMS 5646 M S15795 Washer, flat, MS35333-35334 Washer, lock, met al flat intemal tooth, light and heavy M S17811 Washer, MS35335-35336 Washer, lock, thrust, steel flat and csk., external tooth M S19069-19070 Washer, key, MS35337-35340 Washer, lock, retaining med., light, heavy M S20002 Washer, plain, csk., hi-strength MS35790 Washer, lock, 100° csk., ext. tooth MS21258 retaining, steel Washer, key, MS122026-122075 lock spring Washer, M S25081 Washer, key MS172201-172235 Washer, key, single bearing, retaining M S27051 Washer, slotted MS172271-172320 Washer, key, single GI M S27111 Washer, finishing, NAS70 Washer, plain countersunk NAS143 Washer, M S27129 Washer, finishing, csk., 80°, 82° 00 osk. and plain MS27183 Washer, flat, NAS390-391 Washer, finishing round Par 7-195 Page 7-79
TABLE 7-14. TABLE OF WASHERS (CONTINUED) Washer Number Description Washer Number Description NAS460 Washer, tabtype NAS1587 washer, 1200 °F, plain and csk.
NAS513 Washer, rod end NAS1598 Washer, sealing locking, steel NAS549 Washer, flat, NAS1636 Washer, resin tiber key dual tab NAS620 Washer, flat, NAS1640 Washer, lock, spring, reduced O.D. nonm ag netic NAS1061 Washer, hitemp, lock, spring NAS1099 washer, bevel 9 1/2° NAS1169 Washer, dimpled 100° NAS1197 Washer, flat, 5052 aluminum NAS1252 Washer, fat NAS1401 Washer, radius, al.
Alloy, steel, cres. Steel NAS1515 Washer, plastic and rubber Par 7-195 Page 7-80
TABLE 7-15. TABLE OF PINS Pin Number Description Pin Number Description AN253 Pin, hinge AN416 Pin, retaining safety AN380 & 381 Pin, cotter AN122676-122775 Pin, dowel steel AN385 Pin, AN121601-121925 Pin, flathead devis plain taper .125 -500 drilled shank AN386 Threaded taper pin AN150201-150400 pin, lock, steel, brass AN392-406 Pin, fathead M S9047 Pin, spring, steel, phoshated finish
• AN415 Pin, lock M S9048 Pin, spring, steel, cadmium plate M S9105 Pin, lock IO M S9164 Pin, straight, steel, headless, oversize M S9245 Pin, cotter, cres. AMS 7211 M S9389 Pin, straight, headless, lock, AMS 5735 M S9390 Pin, straight, headless, cres. AMS 5735, dowel std. & O.S.
Par 7-195 Page 7-81
TABLE 7-15. TABLE OF PINS (CONTINUED) Pin Number Description Pin Number Description MS9462-9468 Pin, straight MS35810 Pin, clevis, hd. AM S 5735 headed MS9486 Pin, draight, headless, MS 39086 Pin, spring, lock, AMS 5132 tubular coiled MS9842-9848 Pin, draight, MS51 923 Pin, pring, headed, AMS 5616 tubular coiled MS16555 Pin, straight, headless 0002 MS51 987 tubular coiled over nominal size MS16556 Pin, draight, headless 001 over nominal size MS171401-171900 Pin, spring, SS, steel MS16562 Pin, spring, tubular, slotted NAS427 Pin, pulley guard, steel, al. Alloy MS17984-17990 Pin, quick release, NAS561 Pin, spring slotted positive lock and colled, heavy duty MS20253 Pin, hinge NAS574 pin, rear mounting MS20392 Pin, straight, headed, drilled NAS607 Pin, headless, dowel, steel MS24665 Pin, cotter NAS1 292-1296 Pin, shear thread 100° flush head MS35671-35679 Pin, grooved, headless, NAS1 322 Pin, shear thread, tapered groove protruding head Par 7-195 Page 7-82
TABLE 7-15. TABLE OF PINS (CONTINUED) Pin Number Description Pin Number Description NAS1332-1346 Pin, quick release NAS1535-1542 Pin, swage lock, 100° hd., tension, pul type, alum.
NAS1353-1366 Pin, quick release, NAS1546-1552 Pin, swage lock, positive locking, 100° hd., tension, double acting stump type, alum.
NAS1407 Pin, spring, NAS1583 Pin, 100° csk. hd., coiled hi-shear rivet, 1200 F NAS1436-1442 Pin, swage lock, NAS1584 Pin, fathead, 0000000000001 100° shear head, pull type, steel hi-shear rivet, 1200 F NAS1446-1452 Pin, swage lock, protruding head, pull type, steel NAS1456-1462 Pin, swage lock, 100° head, pull type, steel NAS1465-1472 Pin, swage lock, protruding head, OSCOIN pull type, steel NAS1475-1482 Pin, swage lock, 100° head, pull type, steel NAS1486-1492 Pin, swage lock, 100° head, stump type, steel NAS1496-1502 Pin, swage lock, stump type, steel protruding head NAS1525-1532 Pin, swage lock, protruding head, al. alloy
7-196.-7-206. [RESERVED.] Par 7-195 Page 7-83
Par 8-1 Page 8-1 CHAPTER 8. ENGINES, FUEL, EXHAUST, AND PROPELLERS SECTION 1. ENGINES
8-1. GENERAL. Consult the manufacturer’s manuals, Service Bulletins (SB), and instruction books regarding the repair and overhaul, inspection, installation, and maintenance of aircraft engines for that particular make, model, and type of engine. This section lists acceptable inspection and repair procedures that may be used in the absence of an engine manufacturer’s maintenance information.
8-2. SPECIAL INSPECTION. A visual inspection is needed to determine the condition of the engine and its components. An annual or 100-hour inspection should include the engine and nacelle group as follows.
a. Cold Cylinder Check. If an engine is running rough, the cause may be a bad ignition lead, a spark plug not firing, a partially clogged fuel injector, or a bad magneto. The dead cylinder will be colder than the surrounding cylinders and can be quickly determined by using the recommended cold cylinder checks. This should be done using a thermocouple probe, which is very sensitive to small differences in temperature, which is the case with a partially clogged injector. For a carbureted engine, the following check may be helpful:
(1) Using experienced personnel, run the engine on the bad magneto for approximately 30 seconds at 1200 revolutions per minute (rpm). Without switching the magneto switch back to both shut off the engine. Have another mechanic use a grease pencil (non-carbon) and quickly mark each exhaust stack approximately 1 inch from the flange that holds the exhaust stack to the cylinder. Next, check the exhaust stacks and look for the exhaust stack whose grease pencil mark has not turned to a grayish-white or ash color. This is the cold cylinder.
(2) The probable cause of the cold cylinder is either a defective spark plug or ignition lead. Switch the spark plugs to another cylinder and run the test again. If the problem stays with the original cylinder, the problem is either the ignition lead or the magneto.
b. Piston Engine Sudden Stoppage Inspection. Sudden stoppage is a very rapid and complete stoppage of the engine. It can be caused by engine seizure or by one or more of the propeller blades striking an object in such a way that rpm goes to zero in less than one complete revolution of the propeller. Sudden stoppage can cause internal damage to constant-speed propellers; reduction drive; gear train damage in the accessory section; crankshaft misalignment;
or damage to accessories such as magnetos, generators, vacuum pumps, and tach generators.
(1) Every engine that suffers a sudden stoppage must be inspected in accordance with the manufacturer’s maintenance instructions before being returned to service.
(2) If the engine manufacturer does not provide the required information, then the engine case must be opened, and every major component part must be inspected using visual and/or nondestructive inspection (NDI) procedures as applicable.
(3) The sudden-stoppage inspections include checking for cowling, spinner, and airframe cracks and hidden damage and alignment of the engine mount to the airframe, the
Par 8-2 Page 8-2 mounting hardware, isolation mounts, and bushings. The aircraft’s firewall must also be checked for distortion, cracks, and elongated bolt holes. The damaged propeller must be sent to a Federal Aviation Administration (FAA)-certificated repair station for complete NDI and repair.
(4) Engine accessories, such as magnetos, starters, fuel pumps, turbochargers, alternators, or generators, must be inspected in accordance with the manufacturer’s maintenance manual on sudden stoppage or overhaul procedures to determine the product’s airworthiness.
c. Reciprocating Engine (Direct Drive). Preliminary inspection before teardown.
(1) Remove the engine cowling and examine the engine for visible external damage and audible internal damage.
(2) Rotate the propeller shaft to determine any evidence of abnormal grinding or rubbing sounds.
(3) With the propeller removed, inspect the crankshaft flange or splines for signs of twisting, cracks, or other deformation. Remove the thrust-bearing nut and seal and thoroughly inspect the threaded area of the shaft for evidence of cracks.
(4) Rotate the shaft slowly in 90-degree increments while using a dial indicator or an equivalent instrument to check the concentricity of the shaft.
(5) Remove the oil sump drain plug and check for metal chips and foreign material.
(6) Remove the oil screens and inspect for metal particles and contamination.
(7) Visually inspect the engine case exterior for signs of oil leaks and cracks. Give particular attention to the propeller thrust-bearing area of the nose case section.
(8) Inspect cylinders and the cylinder hold-down area for cracks and oil leaks.
Thoroughly investigate any indication of cracks, oil leaks, or other damage.
d. Internal Inspection Requirements.
(1) On engines equipped with crankshaft vibration dampers, remove and inspect the cylinders and inspect the crankshaft dampers in accordance with the engine manufacturer’s inspection and overhaul manual. When engine design permits, remove the damper pins and examine the pins and damper liners for signs of nicks or brinelling.
(2) After removing the engine-driven accessories, remove the accessory drive case and examine the accessory and supercharger drive gear train, couplings, and drive case for evidence of damage.
(a) Check for cracks in the case in the area of accessory mount pads and gear shaft bosses.
(b) Check the gear train for signs of cracked, broken, or brinelled teeth.
Par 8-2 Page 8-3
(c) Check the accessory drive shaft couplings for twisted splines, misalignment, and run-out.
(d) Check connecting rods for cracks and straightness.
e. Reciprocating Engine (Gear-Drive). Inspect the engine, propeller (see Section 4 on propeller inspection), and components as described in the preceding paragraphs.
(1) Remove the propeller reduction gear housing and inspect for:
(a) Loose, sheared, or spalled cap screws or bolts.
(b) Cracks in the case.
(2) Disassemble the gear train and inspect the propeller shaft, reduction gears, and accessory drive gears for nicks, cracks, or spalling.
f. Engine-Mount Inspection.
(1) Examine the engine flex mounts, when applicable, for looseness of engine to mount, distortion, or signs of wear.
(2) Inspect the engine-mount structure for bent, cracked, or buckled tubes.
(3) Check the adjacent airframe structure firewall for cracks, distortion, or wrinkles.
(4) Remove engine-mount bolts and mount hold-down bolts and replace.
g. Exhaust-Driven Supercharger (Turbo) Inspection. Sudden stoppage of the powerplant can cause the heat in turbine parts to heat soak the turbine seals and bearings. This excessive heat causes carbon to develop in the seal area and varnish to form on the turbine bearings and journals.
(1) Inspect all air ducts and connections for air leaks, warpage, or cracks.
(2) Remove compressor housing and check the turbine wheel for rubbing or binding and coke or varnish buildup.
NOTE: Turbine turbosupercharger disk seal rubbing is not unusual and may be a normal condition. Consult the engine manufacturer’s inspection procedures and table of limits.
h. Accessory and Drive Inspection. Check the drive shaft of each accessory,
i.e., magnetos, generators, external superchargers, and pumps, for evidence of damage.
8-3. CRANKSHAFT INSPECTION AND REPAIR REQUIREMENTS. Carefully inspect for misalignment and replace if bent beyond the manufacturer’s permissible service limit. Worn journals may be repaired by regrinding in accordance with manufacturers’ instructions. It is recommended that grinding operations be performed by appropriately rated repair stations or the
Par 8-3 Page 8-4 original engine manufacturer. Common errors that occur in crankshaft grinding are the removal of nitrided journal surface, improper journal radii, unsatisfactory surfaces, and grinding tool marks on the journals. If the fillets are altered, do not reduce their radii. Polish the reworked surfaces to assure removal of all tool marks. Most opposed engines have nitrided crankshafts, and engine manufacturers specify that these crankshafts must be re-nitrided after grinding.
NOTE: Rapid deceleration or momentary slowing of a propeller may occur due to contact with tall grass, water, or snow. If this occurs, the engine and propeller should be inspected in accordance with the manufacturer’s instruction or SBs.
8-4. REPLACEMENT PARTS IN CERTIFICATED ENGINES. Engine replacement parts must be approved under Title 14 of the Code of Federal Regulations (14 CFR) part 21.
Serviceable parts obtained from the engine manufacturer, authorized service facility, and those which are approved FAA/Parts Manufacturer Approval (PMA) or Technical Standard Order (TSO) and meet the requirements of part 21 are acceptable for use as replacement parts. Used engine parts can be installed if that part either conforms to new part tolerances or meets the manufacturer’s service limits. Ensure that used parts are airworthy and properly identified as a PMA or TSO part.
8-5. OIL SYSTEM LINES INSPECTION. The inspection of the plumbing for an oil system is similar to the inspection of any other plumbing system. The tubing, hose, tube fittings, hose fittings, hose clamps, and all other components of the system are inspected for cracks, holes, dents, bulges, and other signs of damage that might restrict the oil flow or cause a leak. All lines are inspected to ensure that they are properly supported and are not rubbing against a structure.
Fittings should be checked for signs of improper installation, overtorquing, excessive tension, or other conditions which may lead to failure.
8-6. OIL FILTER INSPECTION. The oil filter provides an excellent method for discovering internal engine damage. During the inspection of the engine oil filter, the residue on the screens, disks, or disposable filter cartridge and the residue in the filter housing are carefully examined for metal particles. A new engine or a newly overhauled engine will often have a small amount of fine metal particles in the screen or filter, but this is not considered abnormal. After the engine has been operated for a time and the oil has been changed one or more times, there should not be an appreciable amount of metal particles in the oil screen. If an unusual residue of metal particles is found in the oil screen, the engine must be taken out of service and disassembled to determine the source of the particles. As an additional precaution, an oil analysis/trend analysis may prevent an engine failure in flight. At oil changes, oil samples are often taken and sent to laboratories to be analyzed for wear by determining the amount of metal in the sample. Over time, a trend is developed, and the engine can be removed from service before failure.
8-7. CYLINDER HOLD-DOWN NUTS AND CAP SCREWS. Great care is required in tightening cylinder hold-down nuts and cap screws. They must be tightened to the recommended torque limits to prevent improper stressing and to ensure even loading on the cylinder flange.
The installation of baffles, brackets, clips, and other extraneous parts under nuts and cap screws is not a good practice and is discouraged. If these baffles, brackets, etc., are not properly fabricated or made of suitable material, they may cause loosening of the nuts or cap screws even
Par 8-7 Page 8-5 though the nuts or cap screws were properly tightened and locked at installation. Improper prestressing or loosening of any one of these nuts or cap screws will introduce the danger of progressive stud failure with the possible loss of the engine cylinder in flight.
8-8. REUSE OF SAFETYING DEVICES. Do not use cotter pins and safety wire a second time. Flat, steel-type wrist pin retainers and lock washers, likewise, must be replaced at overhaul unless the manufacturer’s recommendations permit their reuse.
8-9. SELF-LOCKING NUTS FOR AIRCRAFT ENGINES AND ACCESSORIES.
Self-locking nuts may be used on aircraft engines provided the following criteria are met:
a. When their use is specified by the engine manufacturer in the assembly drawing, parts list, and bills of material.
b. When the nuts will not fall inside the engine should they loosen and come off.
c. When there is at least one full thread protruding beyond the nut.
d. Where the temperature will not exceed the maximum limits established for the self-locking material used in the nut. On many engines, the cylinder baffles, rocker box covers, drive covers and pads, and accessory and supercharger housings are fastened with fiber insert lock nuts, which are limited to a maximum temperature of 250 °F. Above this temperature, the fiber insert will usually char and, consequently, lose its locking characteristic. For locations such as the exhaust pipe attachment to the cylinder, a locknut, which has good locking features at elevated temperatures, will give invaluable service. In a few instances, fiber insert lock nuts have been approved for use on cylinder hold-down studs. This practice is not generally recommended since especially tight stud fits to the crankcase must be provided and extremely good cooling must prevail so that low temperatures exist where the nut is installed.
e. Information concerning approved self-locking nuts and their use on specific engines are usually found in engine manufacturer’s manuals or bulletins. If the desired information is not available, it is suggested that the engine manufacturer be contacted.
f. See Chapter 7, Aircraft Hardware, Control Cables, and Turnbuckles, for additional information on self-locking nuts.
8-10. METALLIZING. Metallizing internal parts of aircraft engines is not acceptable unless it is proven to the FAA that the metallized part will not adversely affect the airworthiness of the engine. Metallizing the finned surfaces of steel cylinder barrels with aluminum is acceptable since many engines are originally manufactured in this manner.
8-11. PLATING. Before restoring the plating on any engine part in accordance with the manufacturer’s instructions, the part should be visually inspected and have an NDI performed before any cylinder reconditioning. In general, chromium plating would not be applied to highly stressed engine parts. Certain applications of this nature have been found to be satisfactory;
however, engineering evaluation of the details for the processes used should be obtained.