AC 20-82

5 Dec 72 AC 20-82 CHAPTER 2. WINGS

9. F-27/FH-227 AIRCRAFT MAINTENANCE INFORMATION. Following is a listing of significant maintenance difficulties that have been reported by air carriers. In addition, a number of check and inspection items are listed. This information may be useful in identifying structural inspection areas. Except where noted, wing structural references apply to both left and right wings.

a. Center Wing.

(1) Skin. Lower wing skin cracks have been detected at stringers No. 4 and No. 8 in area of stringer joggles near W/S 68.

(2) Skin. Cracks have been found in the lower wing skin O/B of the center wing to fuselage fitting at the rear spar near W/S 24.

Rib. Cracks have occurred in lower rib flange to stringer attachments at stringers No. 1 through No. 11 near W/S 79.

Stringers. Lower stringers No. 1 through No. 11 have been found cracked on both sides of rib at W/S 20.

Stringers. Lower stringers No. 4 and No. 6 have been found cracked on both sides of rib at W/S zero.

Skin and Stringers. Lower wing skin and stringers No. 5, No. 6, and No. 7 have been found cracked near W/S 64.

Skin. Lower wing skin and external finger strip splice cracks have occurred between the front and rear spar near W/S 55.

Stringer. Cracks have been found in stringer No. 5 at the end of the angle splice near W/S 67.

(9) Skin and Spar. Cracks have occurred in the lower wing skin and in horizontal leg of the front spar cap and splice strip, and the lower skin at the rear spar near W/S 37.

(10) Access Doors. Lower skin access doors have been found cracked.

These doors are located between W/S 80 and 100.

Spar Web. Verticle cracks have occurred in the front spar web at the lower spar cap just 0/B of the stiffener near W/S 89.

(12) Skin. Check for cracks in skin emanating from under the fuselage-to-wing attach fittings and extending forward and aft at W/S 20.

Chap 2 Par 9 Page 5

(13) Spars. Check for cracks in the radius of the lower connecting strip at the front and rear spar near W/S 24.

Cracks in these areas will probably extend I/B then turn forward.

(14) Spar Webs. Check for vertical cracks in front and rear spar webs at the lower spar caps at W/S 22.

(15) Spar. Check for cracks in the rear spar and doubler near W/S Zero.

Engine Mount Support. Cracks have occurred in engine mount upper tube P/N 27-503105-11, -31, -41 and 01-503105-11 or -31; lower tube P/N 27-503101-11, -41, -51, -61, -71, -81, -91, -101 or -111; and upper bracket P/N 27-110105-11, -12, -31, -32, -41, -42, -51, -52, -61, -71, -72, -81, or -82.

Ref. Fairchild Hiller S/B F-27 54-14 revision No. 2 dated February 1969, and FH-227 54-4 revision No. 1 dated February 1969) * b. Outer Wing Panels. (See Appendix l.) *

(1) Doors. Cracks have been found at the attach screw holes of No. 1 inspection door opening near W/S 195 and 205.

(2) Do 2 inspection Check for cracks at the attach screw holes of the No. 2 inspection door opening near W/S 240 and 250.

(3) Doors. Check for cracks at the attach screw holes of the No. 3 inspection door opening near W/S 292 and 302.

(4) Doors. Check for cracks at the attach screw holes of the No. 4 inspection door opening near W/S 335 and 345.

(5) Door and Stringers. Check for cracks in lower skin, access door land, and stringers, at W/S 194, 197, and 204.

Chap 2 Page 6 Par 9

5 Dec 72 AC 20-82 CHAPTER 3. FUSELAGE

10. FH-227 AIRCRAFT MAINTENANCE INFORMATION. Following is a listing of significant maintenance difficulties that have been reported by air carriers. In addition, a number of check and inspection items are listed. This information may be useful in identifying structural inspection areas. Except where noted, fuselage structural references apply to both left and right sides of the fuselage.

a. Windshield Post Fitting. Check windshield post attach fitting and aft side of bulkhead web at F/S 55 for cracks.

b. Forward Bulkhead. Check front bulkhead web through nose wheel well in areas of fittings for evidence of cracks.

Fuselage Tail Section. Cracks have been reported in the skin around the louvers of the aft fuselage tail section. (Ref.

Fairchild Hiller S/B FS-227 53-9 dated 8 June 1967.)

d. Top Fuselage - Cables. Operators have reported a chafing condition between control cables and fuel crossfeed-water methanol lines at F/S 298. (Ref. Fairchild Hiller S/B FH-227 53-8 revision No. 2 dated 23 October 1969.) Applies to aircraft serial numbers 501 through 549.

e. Lower Fuselage Skin. Cracks have been found in the lower fuselage skin between stringers No. 7 and No. 8 left, and stringers No. 44 and No. 45 right, from F/S 198 to 510. (Ref. Fairchild Hiller S/B F-27 53-48 dated 21 March 1967.) Aircraft with serial numbers 20 and above were modified by the manufacturer prior to delivery.

Chap 3 Par 10 Page 7 (and 8)

5 Dec 72 AC 20-82 CHAPTER 4. FLIGHT CONTROLS F-27/FH-227 AIRCRAFT MAINTENANCE INFORMATION. The following is a listing of significant maintenance difficulties that have been reported by air carriers. This information may be useful in identifying structural inspection areas. Except where otherwise indicated, flight control structural references apply to left and right sides.

For details and inspection requirements, each item references pertinent service bulletins, and/or service letters.

a. Rudder and Elevator Tension Regulator. Loose rivets have been found in the rudder and elevator tension regulator. P/N 0501101-0 or 051101-1. (Ref. Fairchild Hiller S/B F-27 27-16 revision No. 2 dated 20 April 1960). Applies to aircraft with serial numbers 1 through 64.

b. Wing Flap Jackscrew Gimbal Nuts. Failure of the gimbal nuts, P/N 27-165012-3, -4, -5, -6, and 27-175023-3, -4, have occurred which render the gimbal nuts unsafe for further use. (Ref.

Fairchild Hiller S/B F-27 27-18A dated 27 October 1959 and 27-28 revision No. 3 dated 22 August 1961).

c. Aileron Control Sectors. Corrosion has been found on magnesium aileron control sectors, P/N 27-727207-21, 27-727208-21, 27-727209-21, 27-727300-21, and 27-727381-21, with two or more years' time since installation. (Ref. Fairchild Hiller Service letters F-27 306 dated 22 August 1963, 307 dated 17 September 1963, and 311 dated 12 April 1965).

d. Horizontal Stabilizer - Upper and Lower Surfaces. Cracks have been found in the skin, stringers, and rib caps. (Ref. Fairchild Hiller S/B F-27 55-6 revision No. 7 dated 1 May 1970, 55-7 dated 20 July and FH-227 55-9 dated 7 July 1969).

e. Horizontal Stabilizer Front Spar. Operators have reported cracks in the front spar web and the upper and lower spar caps between stabilizer stations 95.45 and 125.98. (Ref. Fairchild Hiller S/B F-27 55-7 dated 20 July 1965.

f. Rudder Horn. Cracks have been detected in the rudder horn, P/N 27-243018-11.

g. Horizontal Stabilizer Upper I/B Surface. Cracks have been found in the upper skin between stabilizer stations 0 to 30 from the front spar aft to stringer No. 10. (Ref. Fairchild Hiller S/B FH-227 55-1 revision No. 1 dated 17 November 1966, and F-27 55-11 revision No. 1 dated 17 November 1966).

Chap 4 Par 11 Page 9

AC 20-82 5 Dec 72 Horizontal Stabilizer Rear Spar Fittings. Operators reported cracks in the rear spar fittings, P/N 27-210501-3, -4, -5, -6.

(Ref. Fairchild Hiller S/B FH-227 55-17 dated 10 February 1969).

Rudder Skin, Stiffeners, and Rear Spar. Cracks have been found in the rudder skin and stiffeners and cracks may occur in the rear spar flange. Skin should be inspected from rudder stations 10 to 71 between the center and rear spars. The stiffeners at rudder stations 16, 28, 40, 52, and 64 between the center and rear spars should also be checked for cracks. (Ref. Fairchild Hiller S/B's FH-227 27-4 revision No. 1 and F-27 27-42 revision No. 1, both dated 28 February 1967).

j. Elevator Trim Tab. Failures of elevator trim tab, P/N 01-223008-1, have been reported on at least two occasions. (Ref. Fairchild Hiller Alert S/B FH-227 27-17A dated 8 Jamuary 1968).

Chap 4 Page 10 Par 11

5 Dec 72 AC 20-82 CHAPTER 5. LANDING GEAR F-27/FH-227 AIRCRAFT MAINTENANCE INFORMATION. The following is a listing of significant maintenance difficulties reported by air carriers. This information may be useful in identifying structural and other inspection areas. Except where noted, the items listed refer to left and right sides. For details and inspection requirements, each item references pertinent service bulletins, and/or service letters.

Main Landing Gear Drag Strut Bolts. Several failures of drag strut attach bolts, P/N 9017Y11 and 9027X7, have occurred on aircraft that have accumulated 300 or more landings. (Ref.

Fairchild Hiller S/B F-27 32-44 revision No. 2 dated 19 January 1962).

b. Main Landing Gear Outer Cylinder Torque Link Attach Lugs.

Failures of attach lugs, to which upper torque link, P/N C9027Y3, is attached, have occurred on aircraft that have accumulated 8000 or more landings. (Ref. Fairchild Hiller S/B F-27 32-41A dated 5 April 1961, Dowty Service Bulletins 32-11 dated August 1961, revised December 1962; and 32-15 dated October 1961).

c. Main Landing Gear Drag Strut. Cracks have been detected in main landing gear drag strut assemblies, P/N 2-00259-002, with 500 hours or more time in service.

do Nose Steering Actuator Mount Bolts. Failures of mounting bolts, P/N 244241 and 245804, in the NLG pivot bracket have been reported. (Ref, Walter Kidde Service Bulletin No. 143 dated October 1962)

e. Nose Gear Door Rods. Operators have reported binding of the nose gear door actuating swivel rods. Aircraft with serial numbers 251 and later have been modified by the manufacturer to improve lubrication. (Ref. Fairchild Hiller S/B FH-227 32-3 dated 20 December 1966).

Unselected Gear Retraction. Reports of unselected landing gear retraction on the ground resulted in a change of wiring in the landing gear system. The change was incorporated during the manufacture of aircraft with serial numbers 541 and later.

(Ref. Fairchild Hiller S/B FH-227 32-5 dated 13 March 1967).

Chap 5 Par 12 Page 11 (and 12)

5 Dec 12 AC 20-82 CHAPTER 6. NACELLES

13. F-27/FH-227 AIRCRAFT MAINTENANCE INFORMATION• Following is a listing of significant maintenance difficulties that have been reported by air carriers. in addition, a number of check and inspection items are listed. This information may be useful in identifying structural inspection areas. Except where noted, nacelle structural references apply to both left and right nacelles.

a. Lower Connection Strips. Cracks have been detected in the lower connecting strips at cutout areas of N/S 124, 141, and 157.

b. Nacelle General. Check entire area of center section interior O/B ends for cracks and skin stringers, front and rear spar, and any other evidence of structural irregularity between N/S 120 and 160.

c. Stringers. Check upper center section stringers No. 2 through No. 10 for cracks or other evidence of structural irregularities.

d. Access Doors. Check for cracks in all access doors and door areas.

Premature Cable Wear. Operators have reported premature wear of engine, fuel shutoff, and crossfeed control cables caused by rubbing in fairleads. Applies to aircraft with serial numbers prior to 521.

(Ref. Fairchild Hiller S/B FH-227 54-3 dated 25 April 1967.)

£. Nacelle Aft Bulkhead. On aircraft with serial numbers prior to 522, inspecto for cracks in the rear bulkhead of the left nacelle adjacent to the AC voltage regulator shelf. (Ref. Fairchild Hiller S/B FH-227 54-7 dated 7 June 1967.)

Chap 6 Par 13 Page 13 (and 14)

5 Dec 72 AC 20-82 CHAPTER 7. CORROSION-PRONE AREAS

14. GENERAL Corrosion is most likely to strike at the joints or attachment points in metallic structure because they provide entrapment areas for corrosive agents and moisture to accumulate. However, the problem can be compounded if metallic surfaces are exposed to an extremely corrosive environment, or if the surfaces are difficult to inspect and clean. The most important corrosion preventive measure is to keep them clean and dry.

15. EXHAUST TRAIL AREAS. Both jet and reciprocating engine exhaust deposits contain compounds that are very corrosive, and the structure in the path of exhaust gases is more likely to suffer from corrosion than is any other structure. It is customary to coat structure exposed to exhaust gases with protective finishes to prevent these gases from coming in direct contact with the metal. However, the deposits which collect on top of the protective finishes must be removed before they permeate the film and attack the metal. Most troublesome are those areas where exhaust gas deposits may become entrapped and cannot be reached by normal cleaning methods. Typical of these areas are seams, gaps, hinges, or fairings located in the exhaust gas path.

16. ENGINE FRONTAL AREAS AND COOLING AIR VENTS. These areas are subject to erosion by airborne contaminants, rain, and from foreign objects on the runways. Erosion will remove the protective finishes or oxide film from the metal surfaces leaving them vulnerable to corrosive attack.

recesses is also vulnerable to corrosion. When an aircraft is operated in a marine environment, salt deposits may accumulate in these areas and the ensuing corrosive attack can be rapid and destructive. It is imperative that these areas be frequently inspected and cleaned, and protective finishes be maintained.

17. BATTERY AREAS AND VENTS. Due to the highly corrosive nature of battery acid and its fumes, battery areas and their vents are protected by special acid-resistant paints. Generally this is enough to stem the tide of corrosion if scrupulous attention is devoted to keeping these areas clean.

18. LAVATORIES, GALLEYS AND CABIN FLOORS. The usual spillage, condensation, and other contamination of these areas are extremely corrosive to aircraft metals. The most common corrosive agents are acidic foods and beverages, and human excreta. Also, most chlorinated disinfectants are acidic and corrosive, and cannot be recommended for use in aircraft. It is impractical to assume that these areas can be kept clean and dry at all times, but it is important to inspect Chap 7 Par 14 Page 15

AC 20-82 5 Deç 72 the structure carefully at suitable intervals, cleaning and renewing the finish as necessary. Areas behind lavatories, sinks, or ranges where waste can collect are potential trouble spots, as are personnel relief and waste disposal vents or openings on the exterior of the aircraft.

19. WHEEL WELLS AND LANDING GEARS. Equipment installations in the wheel well areas probably absorb more punishment than any other portion of an aircraft because they are exposed to moisture and flying debris during takeoffs and landings, and when the aircraft is parked they are exposed to atmospheric moisture. After an airplane has entered service, it is difficult to maintain protective paint film on landing gears, equipment installations, and wheel well suriaces because the many complicated shapes, assemblies, and fittings in these areas obscure other surfaces. Items that should receive special attention during wheel well inspections are!

a. Magnesium wheels (especially the areas around the bolt heads, lugs, and wheel webs).

b. Portions of rigid tubing obscured by clamps and identification tapes.

c. Exposed electrical equipment.

d. Crevices between ribs, stiffeners, and lower skin surfaces which can serve as water or debris entrapment areas.

Corrosion control in wheel well areas may best be attained by frequent cleaning, lubrication, paint touchup and judicious use of wheel covers.

20. CONTROL SURFACE RECESSES. Control surface recesses are potential problem areas because normally they are difficult to inspect. If corrosive agents gain entry and accumulate in these areas, they may go unnoticed for some time. Frequent inspection and cleaning of the surfaces and installations located in these recesses will prevent corrosion from gaining a foothold.

21. SPOT-WELDED SKINS. Corrosive agents may become entrapped between the layers of metal adjacent to the spot-weld beads. If moisture enters the area, an elecrolytic cell can be set up between the dissimilar metal phases in the spot-weld area, and one or more of these phases will be subject to preferential corrosive attack. Whenever practical, structural areas with spot-welded assemblies should be sealed to prevent the ingress of contaminants and moisture.

22. HINGES. Hinges are natural traps for corrosive agents. Often they are susceptible to galvanic corrosion when the hinges and pins are made of dissimilar metals. The most practical means of corrosion control is to inspect and lubricate hinges frequently. After lubrication, actuation of the door through several cycles is necessary to ensure complete penetration of the lubricant.

Chap 7 Page 16 Par 18