AI: NO: 20-82 

DATE: 5 Dee 72 

ADVISORY 

CIRCULAR 

DEPARTMENT OF TRANSPORTATION 

FEDERAL AVIATION ADMINISTRATION 

SUBJECT: MAINTENANCE INSPECTION NOTES FOR FAIRCHILD HILLER F-27/FH-227 

SERIES AIRCRAFT 

1. PURPOSE. This advisory circular provides maintenance inspection notes 

which can be used for the maintenance support program for certain 

structural parts of Fairchild Hiller F-27/FH-227 series aircraft. 

2. REFERENCES. 

a. Advisory Circular 20-9, Personal Aircraft Inspection Handbook. 

b. Advisory Circular 20-61, Nondestructive Testing Techniques For 

Aircraft. 

c. Advisory Circular 65-9, Airframe and Powerplant Mechanics General 

Handbook. 

d. Advisory Circular 43.13-1, Acceptable Methods, Techniques and 

Practices - Aircraft Inspection and Repairs. 

3. DESCRIPTION. Maintenance inspection matters on the wing, fuselage, 

empennage, flight controls and landing gear are reviewed, supplementing information currently available. 

4. HOW TO GET THIS PUBLICATION. 

a. Order additional copies of this publication from: 

Department of Transportation 

Federal Aviation Administration 

Distribution Unit, TAD-484.3 

Washington, D.C. 20591 

Initiated by: AFS-230 
5 Dee 72 AC 20- 82 

b. Identify this publication as: Advisory Circular No. 20-82 

Maintenance Inspection Notes for Fairchild Hiller F-27/l%-227 

Series Aircraft. 

C. R. MELUGIN, JR. 

Acting Director, Flight Standards Service 

Page 2 Par 4 
5 Dee 72 AC 20-82 

TABIE OF CONTENTS 

CHAPTER 1. MAINTENANCE INSPECTIONNOTES 1 

1. Preface. 1 

2. Description. 1 

3. Background. 1 

4. General Information. 1 

5. General Visual Inspection Tips. 2 

6. Nondestructive Testing (NDT), 2 

7. Definitions. 3 

8. Abbreviations Used In This Document. 3 

CHAPTER 2. WINGS 

9. F-27/FH-227 Aircraft Maintenance Information. 

5 

5 

CHAPTER 3. FUSELAGE 9 

10. FH-227 Aircraft Maintenance Information. 7 

CHAPTER 4. FLIGHT CONTROLS 9 

11. F-27/FH-227 Aircraft Maintenance Information. 9 

CHAPTER 5. LANDING GEAR 11 

12. F-27/FH-227 Aircraft Maintenance 

Information. 11 

CHAPTER 6. NACELLES 13 

13. F-27/FH-227 Aircraft Maintenance 

Information. 13 

CHAPTER 7. CORROSION-PRONE ARJ3AS 15 

14. 

15. 

16. 

17. 

18, 

19. 

20. 

21. 

22. 

23. 

General 

Exhaust Trail Areas. 

Engine Frontal Areas and Cooling Air Vents. 

Battery Areas and Vents. 

lavatories, Galleys, and Cabin Floors. 

Wheel Wells and Landing Gears. 

Control Surface Recesses. 

Spot-Welded Skins. 

Hinges. 

15 

15 

15 

15 

15 

16 

16 

16 

16 

Lap Joints Between Aluminum Alloy Extruded Sections. 17 

Page No. 

Page i 
AC 20-82 CHG 1 7112173 

24. Fluid Entrapment Areas. 17 

25. Electronic Package Compartments. 17 

26. Control Cables. 18 

27. Microbiological Fuel Contamination and Corrosion. 18 

CHAF'TER 8. 

28. 

CHAPTER 9. 

29. 

*APPENDIX 1. 

PaPe No. 

MAINTENANCE INFORMATION 19 

F-27/FH-227 Aircraft Maintenance Information. 19 

FH-227 AIRCRAFT WINDSHIELD FRAME 23 

Magnetization Characteristics. 23 

Outer Wing Panel Fuel Access Door Land. (2 pages) 1* 

Page ii 
5 Dee 72 

CHAPTERl. MAINTENANCE INSPECTION NOTES 

AC 20-82 

1. PREFACE. This advisory circular provides maintenance information 

which can be used by mechanics, repair agencies, owners, and 

operators in developing maintenance programs, making improvements in 

existing programs, and conducting inspections and repairs on certain 

structural parts of the Fairchild Hiller F-27/FH-227 series of 

airplanes. The material is based, in part, upon information made 

available through discussions with personnel who have maintained 

these types of airplanes for thousands of hours of time in service. 

The intent of the circular is to impart some of this knowledge to 

other interested persons so that it is not lost. 

2. DESCRIPTION. The circular contains guidance material for performing 

inspection and maintenance on wing, fuselage, empennage, and landing 

gear structures. The information has been derived from service 

experience and maintenance publications. Also, there is a listing of 

selected maintenance difficulties reported during 1970 and 1971. 

3. BACKGROUND. 

a. Aircraft Use. The agency has realized that several different 

types of transport aircraft are being phased out of service by 

some airlines because of the availability of newer equipment. 

Such older aircraft are being purchased by other operators who 

may not be familiar with the scope of required maintenance and 

the means which have been used to keep the aircraft in a safe 

and airworthy condition. 

b. Maintenance "Know How." Since maintenance "know how" is not 

transferred with the aircraft, the new operator generally goes 

through a learning cycle before he is able to rapidly pinpoint 

the critical problem areas of the aircraft. In this respect, 

identification of known areas where structural problems have been 

experienced will help in the preparation of an initial maintenance 

inspection program by a new operator. It can also serve as a 

guide to other operators who have not accumulated sufficient 

experience to have knowledge of all the problem areas of the 

aircraft. 

4. GENERAL INFORMATION. 

a. Manufacturer's Bulletins. It must be emphasized that the manufacturer has published several service bulletins and service letters 

concerning the inspection, repair, and modification of Fairchild 

Hiller F-27/FH-227 series aircraft. Service bulletins highlight the 

importance of maintaining structural integrity on aircraft with particular reference to areas known to have experienced crack and corrosion 

damage. Service letters may provide maintenance information and will 

Chap 1 

Par 1 Page 1 
AC 20-82 5 Dee 72 

reference a service bulletin if the information published is 

serious enough to warrant additional action requiring engineering 

approval. Operators are urged to become conversant with the 

manufacturer's recommendations and make certain that responsible 

maintenance personnel are knowledgeable on this subject. 

b. Airworthiness Directive. It is emphasized that the material in 

this circular does not supersede any of the requirement of airworthiness directives issued under Part 39 of the Federal Aviation 

Regulations. 

.5. GENERAL VISUAL INSPECIION TIPS. The primary structure of the aircraft 

is designed to provide resistance to variable forces imposed while in 

operation by dispensing the forces through a structural pattern of 

"force flow" to the primary structural members of the wing and fuselage. 

External indications of failure, such as distorted skin, tilted or 

sheared rivets, and torn, dented, cracked, or corroded skin, are 

usually obvious. Wrinkled skin, "oil cans," and tilted rivets, 

adjacent to the obviously failed area, often indicate secondary 

damage caused by transmission of stress from the failed area,, 

Misalignment of doors and panels may indicate distortion of internal 

structure* Internal structural damage, although not always apparent, 

may be found by closely examining the exterior surface. For example: 

a. Buckled skin between rivets at the end of a stiffener or stringer 

could mean that the last attaching rivet has failed, or that the 

stiffener or stringer is buckled in the area of the skin buckle. 

When a detailed inspection of the failed area is to be performed, 

functional parts should be actuated to determine if the failure 

has caused binding. 

b. Deep diagonal skin buckles, located over a frame, former, or rib, 

could mean the member is distorted. When doubt exists concerning 

internal condition, the area in question should be opened and carefully inspected. 

6. NONDESTRUCTIVE TESTING (NDT). Simply stated, nondestructive testing is 

preventive maintenance. This includes utilization of such maintenance 

tools as X-ray, ultrasonic, magnetic particles, eddy current, dye 

penetrant, and others. 

a. Maintenance Inspection. NISI permits maintenance inspections without 

removing components from aircraft or tearing down complex assemblies. 

Defects in various aircraft systems which would escape detection 

through normaL;visual inspection can be identified by N'UI. 

b. Training Required. Special NDT training is desirable to make sure 

that the operator is capable of operating the equipment and 

interpreting the results. Also, many States require that an X-ray 

operator have an approved certificate for use of X-ray in industrial 

applications. 

Ghap 1 

Page 2 Par 4 
5 Dee 72 AC 20-82 

7. DEFINITIONS. 

a, 

b. 

C. 

d. 

Fatigue. The progressive fracture of a metal by means of a fault 

which develops and spreads under repeated cycles of stress. 

Stress. The force per unit area of a body that tends to produce 

a deformation. 

Stress Raiser. A scratch, groove, rivet hole, forging defect, or 

other structural discontinuity giving rise to a focal point for a 

local concentration of stress. 

Corrosion. Gradual destruction of a material by chemical action 

which is often evidenced by oxide huild-up on the surface. 

8. ABBREVIATIONS USED IN THIS DOCUMENT. 

AD 

F/S 

MLG 

P/N 

S/B 

w/s 

I/B 

O/B 

N/S 

S/N 

Airworthiness Directive 

Fuselage Station 

Main landing Gear 

Nose landing Gear 

Part Number 

Service Bulletin 

Wing Station 

Inboard 

Outboard 

Nacelle Station 

Serial Number 

Chap 1 

Par 7 Page 3 (and 4) 

5 Dee 72 AC 20-82 

CHAPTER 2. WINGS 

9. F-27/FH-227 AIRCRAFT MAINTEA? INFORMATION_. Following is a listing 

~~g~~ant 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. Cent-. 

(1) 

(2) 

(3) 

(4) 

(5) 

(6) 

(7) 

(8) 

(9) 

(10) 

(11) 

(12) 

Skin. Lower wing skin cracks have been detected at stringers -^- 

No. 4 and No. 8 in area of stringer joggles near W/S 68. 

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. 

Strine. 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. 

Skin andSpar. 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. 

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 O/B of the stiffener near 

W/S 89. 

Skin. Check for cracks in skin emanating from under the 

Glage-to-wing attach fittings and extending forward and 

aft at W/S 20. 

Chap 2 

Par 9 Page 5 
AC 20-82 CHG 1 7/12/73 

(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. 

(16) 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 1.) * 

(1) Doors. Cracks have been found at the attach screw holes of 

No. inspection door opening near W/S 195 and 205. 

(2) Doors. Check for cracks at the attach screw holes of the 

No. 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, 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. 

Page 6 

Chap 2 

Par 9 
5 Dee 72 

CHAPTER 3. FLJSELAGE 

AC 20-82 

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. 

b. 

C. 

d. 

e. 

Windshield Post Fitting. Check windshield post attach fitting and 

aft side of bulkhead web at F/S 55 for cracks. 

Forward Bulkhead. Check front bulkhead web through nose wheel well 

in areas of fittings for evidence of cracks. 

Fuse% 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.) 

Tops'uaAe - 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. 

Lower Fuse19 Skin. Cracks have been found in the lower fuselage 

skin between stqers 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 Dee 72 

CHAPTER4. FLIGHT CONTROLS 

AC 20-82 

11. 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. 

b. 

CO 

d. 

e. 

f. 

8. 

Rudder and Elevator Tension Regulator. Loose rivets have been 

found in the rudder and elevator tension regulator. P/N 0501101-O 

or 051101-l. (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. 

Wing Flap Jackscrew Gimbal Nuts. Failure of the gimbal Buts, 

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 27-188 dated 27 October 1959 and 27-28 

revision No. 3 dated 22 August 1961). 

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). 

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 1May 1970,'55-7 dated 

20 July and FH-227 55-9 dated 7 July 1969). 

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. 

Rudder Horn. Cracks have been detected in the rudder horn, 

P/N 27-243018-11. 

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-l 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 Dee 72 

h. Horizontal Stabilizer Bear Spar Fittings. Operators reported 

cracks in the rear spar fittings, P/N 27-210501-3, -4, -5, -6. 

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

. 1. Budder Skin, Stiffeners, and Bear 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). 

5 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 January 1968). 

Page 10 

Chap 4 

Par 11 
5 Dee 72 

CHAPTER 5. LANDING GEAR 

AC 20-82 

.2. 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, 

a. 

b. 

C. 

d. 

e. 

f. 

Main Landing Gear Drag Strut Bolts. Several failures of drag 

strut attach bolts, P/N 9017Yll 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). 

Main Landing Gear Cuter 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 32-418 

dated 5 April 1961, Dowty Service Bulletins 32-11 dated August 

1961, revised December 1962; and 32-15 dated October 1961). 

Main LandinP: 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. 

Nose Steering Actuator Mount Bolts. Failures of mounting bolts, 

P/N 244241 and 245804, in the NLG pivot bracket have been 

reported. (Ref, Walter Xidde Service Bulletin No. 143 dated 

October 1962) 

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 Dac 72 AC 2Oa82 

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. 

b. 

C. 

d. 

e. 

f. 

Lower Connew. Cracks have been detected in the lower 

GGxny strips at cutout areas of N/S 124, 141, and 157. 

Nacelle General. Check entire area of center section interior O/B --_I_ 

ends for cracks and skin stringers, front and rear spar, and any 

other evidence of structural irregularity between N/S 120 and 160. 

String. Check upper center section stringers No. 2 through 

No. 10 for cracks or other evidence of structural irregularities. 

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

-..-- 

Premature Cable Wear_. Operators have reported premature wear of 

engine, fuel shutoff, a nd 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, 

inspect0 for cracrin 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 Dee 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 arc 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. In addition, much of the equipment installed within these 

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. BATTERYAREAS ANDVENTS. 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 Des 72 

19, WHEEL WELLS AND LANDING GEARS. Equipment installations in the wheel 

well areas prohably 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 surfaces 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 ( es p ecially 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 inspect'ion and cleaning of the surfaces and 

installations located in these recesses will prevent corrosion from 

gaining a foothold. 

21. SPm-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. 

Page 16 

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. 

Chap 7 

Par 18 
5 Dee 72 AC 20-82 

23. LAP JOINTS BETWEEN ALUMINUM ALLOY EXTRUDED SECTIONS. Extruded 

sections of high-strength materials such as 7075 or 7178 aluminum 

alloys are more susceptible to intergranular corrosion than are other 

aluminum alloys. Application and maintenance of chemical processes, 

sealants, paints, or combinations of these protective measures have 

proven most effective in controlling corrosive attack on these 

materials. 

If intergranular corrosion occurs, it is usually found around 

fasteners or in lap joints. It is evidenced by raised areas or lumps 

under the paint film, and there have been instances where the attack 

has progressed to such an extent that there were actually bulges in 

the faying surfaces. These raised areas, lumps, and bulges are due 

to the accumulation of corrosion products, which take up more volume 

than did the affected material before it corroded. 

24. FLUIDENTRAPMENTAREAS. Design specifications require that aircraft 

have drains installed in areas where water may collect. However, 

if drains are rendered ineffective because they are clogged by debris, 

sealant, etc., or because the level of the aircraft is changed from 

that of a normal ground attitude, corrosive agents can collect in a 

localized area. Low-point areas and drains should be inspected 

frequently to prevent the inception of corrosive attack. 

Low points of integral fuel tanks are areas where water condensate 

can collect. This water condensate is of doubtful purity, and 

if permitted to stand it can permeate the protective coating of the 

tank and bring many corrosive agents held in suspension in contact 

with the vulnerable metallic surfaces. Water condensate should be 

drained regularly from fuel tanks and the integrity of the tank 

sealant maintained to prevent corrosion of integral tank surfaces. 

When considering fluid entrapment areas, one inevitably thinks of aircraft drinking water and wash water systems. Corrosion in these 

systems is rare because they are fabricated from nonmetallic materials 

and/or stainless steel. Water stagnation should pose no problems so 

long as sanitation regulations are heeded. 

25. EIECTRONIC PACKAGE COMPARTMENTS. Often the safety of those on board 

an aircraft rests on the proper function of a little black box. The 

environment of electronic package compartments is carefully controlled 

to provide the most ideal conditions that can be achieved. The degree 

to which such sensitive equipment is exposed to corrosive agents is 

very small, but even small quantities of moisture and contaminants 

can adversely affect equipment reliability, Components in these 

areas should be inspected for corrosive attack as thoroughly as 

possible during routine checks, and advantage should also be taken 

of nonscheduled component removals for further inspection. 

Chap 7 

Par 23 Page 17 
AC 20-82 5 Dee 72 

26. CONTROL CABLES. Control cables have preservative coatings which, when 

intact , prevent corrosive attack. Due to their vital function it is 

necessary to inspect these cables frequently to ensure that they are 

adequately protected. During these inspections incipient failures due 

to other causes also may be detected. It is recommended that control 

cables be inspected periodically, then cleaned and treated as necessary 

before reapplication of the preservatives. 

27. MICROBIOLOGICAL FUEL CONTAMINATION AND CORROSION. Microbiological 

contamination in turbine fuel is caused by bacteria and fungi which 

feed on the constituents of the turbine fuel. The result is a sludge, 

or mat deposit, which has been found in some aircraft fuel tanks and 

is often loosely referred to as green slime. However, some deposits 

have been found in various shades of grey, brown, red, and white. If 

allowed to develop and grow in the aircraft fuel tanks, microbiological 

contamination can cause a myriad of problems not the least of which 

is severe aluminum alloy corrosion in the aircraft integral fuel tanks 

or the deterioration of the inner liner in fuel bladder cells. 

Fairchild Hiller Service Letters FH-227 28-2 dated 15 May 1966 and 

F-27 222 dated 24 June 1960 are related to this problem. 

Page 18 

Chap 7 

Par 26 
5 Dee 72 

CRAPTER8. MAINTENANCE INFORMATION 

AC 20-82 

28. F-27/FH-227 AIRCRAFT MAINTENANCE INFORMATION. The following is a 

listing of significant maintenance difficulties that have been 

reported by air carriers as mechanical reliability reports from 

January 1970 through June 1971 ADP records. This information may 

be useful in identifying additional structural inspection problem 

areas. In all cases, check the corresponding trouble area, leftright, top-bottom, forward-aft, etc. 

a. Wing. 

(1) During routine inspection, found l/4-inch crack, left wing 

at No. 1 tank plate. Crack started from nut plate rivet 

hole under rivet head, W/S 196 aft of No. 7 stringer. This 

area had been inspected by X-ray approximately 104 hours prior 

to discovery of crack .but was not visible on X-ray. 

(2) During X-ray inspection, found l/4-inch to l/2-inch cracks 

in stringers No, 2, No. 3, No. 4, No, 7 and No. 8, wing 

center section at W/S zero. 

b. Fuselage. 

(1) Routine inspection disclosed intergranular corrosion on 

cockpit floor between F/S 77 and 97. The damaged area was 

left and right of the center line. 

(2) During routine inspection, found intergranular corrosion on 

the floor panel between F/S 576 and 588 at approximately the 

center line of the fuselage. The aircraft total time was 

12,180 hours. 

(3) Routine inspection revealed a l/2-inch crack in skin and a 

3/8-inch crack on the fuselage former flange at F/S 803, 

right-hand side at stringer No. 168. Total airframe time 

was 25,238 hours. 

(4) Inspection disclosed a 3/8-inch skin crack and 3/4-inch 

fuselage former crack at F/S 834, right side at stringer 

No. 168. Total airframe time was 25,238 hours, 

(5) Routine inspection disclosed fuselage former at F/S 404 had 

a 2-inch crack on the right side and two l/2-inch cracks on 

the left side. Total airframe time was 29,125 hours. 

(6) One report was received concerning loss in flight of a 15- 

inch by 30-inch section of the right wing-to-fuselage 

fiberglass fillet. 

Chap 8 

Par 28 Page 19 
AC 20-82 

co Flight Controls - Empennage, 

5 Dee 72 

(1) 

(2) 

(3) 

(4) 

Operator reported finding cracks in stringers, ribs, and 

brackets in the vertical stabilizer VOR antenna mounting 

area at vertical stabilizer station 201,56. Total time on 

the aircraft concerned ranged from 7,798 hours to 9,888 hours. 

During routine overhaul inspection, a S/8-inch crack from 

the bolt hole to the edge of the casting, P/N 27-233000-31, 

was found in the forward leg of the left rear vertical 

stabilizer attach casting, Total aircraft time was 14,704 

hours. 

One operator conducted a fleet campaign and increased 

inspection frequency as a result of finding a 2-inch crack 

in the right elevator spar web at the O/B hinge bracket 

attachment at elevator station 156, (Ref. Fairchild S/B 

F-27 27-21 revision No. 3 dated 26 May 1962). 

During approach for landing, the crew reported a sharp jerk 

of the elevator controls, After landing, inspection revealed 

a hinge bracket broken out from the elevator spar. The 

bracket was P/N 27-220001-141. Elevator time since overhaul 

was 1,855 hours. 

d. Landing Gear. 

(1) 

(2) 

(3) 

(4) 

Several operators reported finding cracked MLG drag strut end 

fittings; lower fitting, P/N 200259-302, and upper fitting, 

P/N 200259-611. Cracks originated at the retaining pin holes. 

Total time in service of end fittings ranged from 8,278 hours 

to 9,764 hours. 

The crew reported a loud bang from the nose wheel well after 

takeoff when gear retracted and nose gear position indicator 

showed nose gear down. Subsequent inspection disclosed link 

rod to NLG door lock was broken. 

During routine inspection, six loose rivets were found at 

MLG support angles for retract cylinder attach fittings, P/N 

01-502033-41. 

The crew reported vibration in the nose section. Ground 

personnel verified the nose gear was up but one nose gear 

door was open. Inspection, after landing, revealed the left 

door attach arm, P/N 27-422013-5, was broken. 

Page 20 map 8 

Par 28 
5 Dee 72 

e. Miscellaneous. 

(1) 

(2) 

(3) 

AC 20-82 

One operator experienced a shattering of the left outer 

windshield panel during cruise. The total time since 

new was 7,317 hours. 

One report of R/H cockpit sliding window shattering during 

flight was received. Total time in service was 20,782 

hours. 

An engine gearbox failure resulted in an in-flight shutdown 

and an unscheduled landing. Subsequent investigation 

disclosed that the input bevel pinion splines, P/N 601013-329, 

and blower spur wheel, P/N 601013-284, had failed. Gearbox 

time since overhaul was 3,363 hours. 

Chap 8 

Par 28 Page 21 (and 22) 

5 Dee 72 AC 20-82 

CHAPTEK 9. FH-227 AIRCRAFT WINDSHIELD FRAME 

29. MAGNETIZATION CHARACTERISTICS. The windshield frame on the FH-227 

is made of ferrous metal; thus the windshield frame becomes 

magnetized if the aircraft has an electrical discharge during an 

electrical storm. This, in turn, causes erroneous readings on 

the standby magnetic compass. The windshield, particularly the 

center post, should be checked periodically for being magnetized. 

The windshield can be degaussed. 

Chap 9 

Par 29 Page 23 

7112173 

1 STATION 206 

AC 20-82 CHG 1 

Appendix 1 

w / /b o/ ‘LAMINATION STEP 14 :” \ 0 o‘\.\NO 5 

- 

\ //O 0 ci 0 01 

/I 

\ 

\ 

O//O 0 

I lo 0 [TOPVlEWj 

\T 0 o’, 0 

\ 

0 

4 

v-----l1 FWD. - 

CUTBOARD + 

\o 0 

& \ 

0’0 0 

\ 

\ 

\o 0 

t - - 

STATldN 197 

FIGURE 1. CRACKS IN WING FUEL ACCESS DOOR LAND AT WS 197 AND WS 206. 

On a routine inspection of an FH-227 series aircraft, two cracks, $-inch 

long each, were found in the No. 1 fuel access door land screw-holes 

(Ref. Fairchild Hiller Service Bulletin FH 227-51-1). Total aircraft 

time 12,830 hours. Time since inspection 150 hours. Time since last 

X-ray 465 hours. 

Page 1 
AC 20-82 CHG 1 

Appendix 1 

7112173 

IsTA. 195 

0 

__--- -- 

, --L 0 0 1 _- , 7 c-t-. i’ ---- 

LOOKING AT EDGE TO DETERMINE ’ 

NUMBER OF LAMINATIONS CRACKED 

CRACK APPROXIMATELY 1;” 

LEAST 4 LAMINATIONS 

[TOP1 

FWD. +I 

- 

IV 

--- 

~IZJTBOARD + 

LOOKING AT EDGE TO DETERMINE 

FIGUKE 2. CRACKS IN WING FUEL ACCESS DOOR LAND AT WS 195 AND WS 196. 

On a routine inspection of an FH-227 series aircraft, two cracks, l/2-inch 

and 7/8-inch long, were found in the left outer wing panel at the 6crewhole6 in the No. 1 fuel acces6 door land. (Ref. Fairchild Hiller Service 

Bulletin FH-227-51-1). Total aircraft time 12,257 hours. Time since 

inspection 132 hours. Time since last X-ray 1,143 hours. 

Page 2 


qONSOIJDATED FtEPFtINT--MARCH 1977 

(includes Change 1) 

AC No: 20-82 

DATE: 5 Dee 72 

ADVISORY 

CIRCULA 

MAlNTEN+NCE INSPECTION NOTES FOR FAIRCHILD HILLER F-27/FH-227 SERIES AIRCRAFT 

PEPARTMENT OF TRANSPORTATION 

FEDERAL AVIATION ADMINISTRATION 

Initiated by: ~~~-230