AC NO: 20-84 DATE: 22 Jan 73 AiDVISORY
CIRCULAR DCE INSPECTION NOl!ES FOR BOEING B-727 SERIES AIRCRAFT
CONSOLIDATED REPRINT
THIS CONSOLIDATED REPRINT INCORPORATES CHANGES 1 and 2
DEPARTMENT OF TRANSPORTATION
FEDERAL AVIATION ADMINISTRATION
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AC NO: 20-M 1 DATE: 22 Jan 73 < Of TR+$ &#* % e ?A 6 0, D 6 8 z ADVISORY + * “z 3 d 6 %rrs 0% /+ CIRCULAR
DEPARTMENT OF TRANSPORTATION
FEDERAL AVIATION ADMINISTRATION SUBJECT: MAINTENANCE INSPECTION NOTES FOR BOEING B-727 SERIES AIRCRAFT
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PURPOSE. This advisory circular provides inspection notes which can be used for the maintenance support program for certain structural parts of the B-727 series aircraft.
:cDESCRIPTION. Maintenance inspection matters on the wing and fuselage are reviewed with a view toward supplementing information currently available.
REFERENCES.
a. Advisory Circular 20-61, Nondestructive Testing Techniques for Aircraft.
b. Advisory Circular 65-9, Airframe and Powerplant Mechanics General Handbook.
c. Advisory Circular 43.13-1, Acceptable Methods, Techniques and Practices - Aircraft Inspection and Repair.
d. Defense Metals Information Center (DMIC) Report, S-25, dated June 1, 1968, Current Problems and Prevention of Fatigue.
e. Advisory Circular 20-9, Personal Aircraft Inspection Handbook.
1 Initiated by:MS-302/fiC-230
AC 20-84 22 Jan 73
4. HOW TO GET THIS PUBLICATION.
a. Order additional copies of this publication from:
Department of Transportation Distribution Unit, TAD-484.3 Washington, D. C. 20590
b. Identify the publication as Advisory Circular No. 20-84, Maintenance Inspection Notes For Boeing B-727 Series Aircraft.
(y%5?q* C. R. MRLUGIN, JR.
Acting Director, Flight Standards Service Page ii Par 4
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TABLE OF CONTENTS AC 20-84 CHG 2
1. Introduction.
2. Description.
3. Background.
4. General Discussion of Structure Surveillance.
5. Type of Construction.
6. Aircraft Station Diagrams.
7. Abbreviations Used In This Document.
8. Maintenance Reports.
APPENDIX 1. CORROSION (2 pages) 1 APPENDIX 2. STATION CHARTS (6 pages) Figure 1. Principal Dimensions 1 Figure 2. Forward Body Station Diagram 2 Figure 3. Aft Body Station Diagram 5 Figure 4. Wing .Station Diagram 4 Page No.
Figure 5. Stabilizer and Elevator Station Diagram 5 Figure 6. Side Engines Station Diagram 6 APPENDIX 3. NONDESTRUCTIVE TESTING (5 pages) 1 Page iii
AC 20-84 CHG 1
1. INTRODUCTION. This advisory circular provides maintenance information which can be used, but is not required to be used, by mechanics, repair -- agencies, owners, and operators in developing maintenance programs, making improvements in existing programs, and conducting inspection and repairs on certain structural parts of Boeing B-727 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. Appendices 1, 2, 3 and 4 provide a technical digest of material on corrosion, fatigue failures, nondestructive testing and station charts, respectively.
2. DESCRIPTION. This circular contains guidance material for performing maintenance on wing, fuselage, and empennage structure. The information has been derived from service experience. It does not comprise a full and complete maintenance program for the subject aircraft, but should be considered as supplemental maintenance data. Included in the circular is a listing of selected maintenance difficulties which have been reported since 1966 by air carrier operators.
3. BACKGROUND.
9: a. Used Aircraft. The Administrator realizes that several different types of transport aircraft are being phased out of service by some airlines and are being purchased by other operators who may not be 9:
familiar with the scope of required maintenance and the means which have been used to keep the aircraft in a safe 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 important/ 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 program by a new operator. It also can serve as a guide to other operators who have not accumulated sufficient service experience to have knowledge of all the problem areas of the aircraft.
4. GENERAL DISCUSSION OF STRUCTURE SURVEILLANCE.
a. Manufacturer's Service Bulletins. The manufacturer has published service bulletins containing its recommendations concerning the inspection, repair, and modification of aircraft. Most of these bulletins cover known areas; however, some are predictive in nature and have been issued even though no fatigue damage has been identified in the fleet. Because of differences in structural configuration, most service bulletins apply only to certain aircraft. Effectivity is shown in each bulletin. Additional bulletins may be published by the manufacturer, and a service bulletin index is available from the manufacturer which is updated periodically.
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b. Other Documentation. Further, the manufacturer has published the ( following documents to aid in maintaining the aircraft in serviceable condition:
Maintenance Planning Document (D6-8766) Maintenance Manual, (D6-Series, different for each operator) Overhaul Manual, (~6-4420) Structural Repair Manual (~6-4062) NM' Document (D6-7170) * These documents are updated from time to time by the manufacturer.
Structural Item Interim Advisories are published by the manufacturer to notify operators of newly found problems which may be of fleetwide significance and may or may not be followed by service bulletins.
c. Maintenance Action. For adequate maintenance of the B-727 structure, every operator should have in his possession and be conversant with the above documentation, including service bulletins applicable to his particular aircraft. He should also obtain complete service records from previous owners and become familiar with the structural history of his aircraft, including information on maintenance procedures followed, major repairs made, and preventive modifications and/ or repair work incorporated per service bulletins. This is essential to carry out the followup procedures required, and to avoid unnecessary work where corrective action has already been taken.
(1) The new operator should contact the manufacturer regarding any areas requiring clarification.
(2) The operator should keep himself informed of new developments and arrange to be supplied with revised and new documentation by the manufacturer. Consultation with the manufacturer and/or more experienced operators should take place from time to time as necessary, to establish which service bulletins have structural significance and when they would best be incorporated.
(3) The maintenance program established by the new operator should reflect changes in environment and usage of the aircraft (e.g., shorter flights, intermittent use, etc.).
d. Airworthiness Directives. It is emphasized that the material in this circular does not supersede any of the requirements of airworthiness directives issued under Part 39 of the Federal Aviation Regulations.
e. Certification. Type certificate No. A3WE was issued to The Boeing Company, Renton, Washington, on 24 December 1963. The basis for certification was CAR 4b (dated December 1953). The type certificate data sheet No. A3WR prescribes conditions and limitations for which the type certificate was issued. The latest revision of the type certificate data sheet, at the time this document was published, was revision No. 10 (dated 1 September 1972). 3; * Page 2 Par 4
5. TYPE OF CONSTRUCTION. The aircraft structure is comprised of three major sections: the fuselage, the wing, and the empennage. The structure is designed to provide maximum strength with minimum weight by providing alternate load paths so that a failure of one segment will not result in failure of the complete structural component. The materials most commonly used throughout the structure are aluminum, steel, and magnesium alloys. In secondary structural areas and many flight control surfaces, aluminum and fiberglas honeycomb core material is extensively used.
a. The fuselage is a semimonocoque structure with the skin reinforced by circumferential frames and longitudinal stringers. It is composed of four sections of which the forward three sections contain passenger, crew, and cargo compartments and extend from body station 178 to body station 1183. The fourth section (aft) provides support for the engines and empennage. Except for the nose gear wheel well and the cutout which accommodates the center wing box and main landing gear wells, the entire shell between body stations 178 and 1183 is pressurized. The frames at body stations 740 and 870 incorporate the points at tihich the fuselage is attached to the wing front and rear spars.
b. The wing structure consists of a left and right wing box and a center wing box. The left and right wing boxes are cantilevered from the center wing box and the thickness and chord of each wing tapers towards the tip and sweeps back from the center wing box. The surfaces consist of upper and lower skin panels and front and rear spars. The skin is reinforced by spanwise stringers and the spars are reinforced by vertical stiffeners.
(1) The left and right win, 0‘ boxes are reinforced by chordwise ribs with the greater portion of their enclosed volume sealed to serve as fuel tanks. They extend from the wing root ribs at WBL 70.5 to the tank end rib at station 760.5. The center wing box is reinforced by a pair of spanwise beams and contains a series of bladder-type fuel cells.
(2) The leadin, 0‘ edge of each wing supports three flaps and four slats. The trailing edge of each wing supports an inboard and outboard flap, an inboard and outboard aileron, and seven spoilers.
c. The empennage consists of a vertical fin, adjustable horizontal stabilizer, two elevators and two rudders. The vertical fin structure is a three-spar box with longitudinal stringers to reinforce the skin. The box is reinforced by chordwise ribs.
(1) The horizontal stabilizer is installed across the top of the vertical fin and consists of a complete dual box structure from left to right tip.
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(2) The rudders and elevators are dual spar structures with ribs and i boned skin panels. Each rudder has a full length antibalance tab%onstructed Of aluminum or fiberglass honeycomb. Each J;
elevator has a' control tab and five balance panels are hinged to the nose of each elevator.
6. AIRCRAFT STATION DIAGRAMS. The wing, fuselage, and empennage station diagrams included in this document were developed for the B-727 aircraft and are used as a general reference only. Several models of these aircraft were manufactured and have different station locator numbers based on the particular configuration. Since the defective areas generally apply to all models of aircraft, the referenced area can be compared with a similar area and locator on the appropriate station diagram for the particular model aircraft.
7. ABBREVIATIONS USED IN THIS DOCUMENT.
NLG
O/B P/N
R/H TAT TSN TSO Federal Aviation Regulation Inboard Left Hand Main Landing Gear Nose Landing Gear Outboard Part Number Right Hand Total Aircraft Time Time Since New Time Since Overhaul
1. MAINTENANCE REPORTS. The following is a listing of selected maintenance difficulties experienced, representing examples of reports submitted by air carrier operators. This information may be useful in identifying structural problem areas. It should be noted that this is a partial list and covers only a portion of time in the history of the B-727 series aircraft.
a. Fuselage.
(1) A 4" crack was found in fuselage frame at station 783.95 on the R/H side below the cabin floor. TAT 14,255 hours.
(2) The NLG drag strut support shelf was found to have cracks in the L & R tangs. TAT 14,255 hours.
(3) Tine aft pressure bulkhead left vertical beam was found cracked at the upper lightening hole. TAT 14,255 hours. c (&) During main base check, the tail skid door link lower attach fitting was found to be cracked, fitting P/N 65-59727-6.
TAT 14,882 hours.
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08) A 1" crack was found in the aft brace support beam. TAT 14,056 lower corner of the NLG drag hours.
Corrosion was found at the skin TAT 14,056 hours.
lap at station 665 stringer 28~.
AC 20-84 CHG 1 A 10" crack was found in the upper vertical "1" beam on the L/H side of the aft entry door. TAT 8,998 hours.
An unscheduled landing was made due to 6 L/H eyebrow window inner panel cracking during cruise, window P/N 5-7176-13.
TAT 13,480 hours.
During eddy current inspections, cracks were detected on the L & R sides of the bulkhead flanges at station 740. The cracks were between stringers 18 & 19 and 19 & 20. TAT on the several aircraft concerned ranged from 8,641 hours to 15,444 hours.
During main base inspections, stringers 20 & 21 L & R and 22R at station 294.5 and stringer 2OR at station 360 were found cracked. TAT 14,786 hours to 15,610 hours.
Routine inspection disclosed a 2" crack in station 930 L/H fuselage frame and stringer 18A, also cracked skin at station
940. TAT 17,270 hours.
The upper left fuselage skin lap was found bulged at station 900 and the skin split at stations 990 & 1030 due to corrosion, ;t TAT 17,482 hours.
Routine scheduled inspection disclosed cracks in the cabin floor beam at station 910. TAT 15,256 hours.
During scheduled inspection, the forward hinge mount bracket on the forward cargo door was found broken and pulled out of the structure. TAT 6,150 hours.
Extreme corrosion was found on main cabin seat track assemblies #3, 5, 6, and 7 between stations 4X, and 720. TAT 8,026 hours.
The fuselage frames at both hinge cutouts for the aft cargo door were found cracked. TAT 13,OgO hours.
3uring modification, the following damaged fuselage frames were replaced: stations 480, 500, 520, 540, 560, 580, 600, 600F, 600G, 600H, and 6005. Also replaced damaged skin panel station 420 to F. S. Bulkhead. TAT 30,380 hours, Fuselage frame station 880 found cracked at stringers #15 L & R.
TAT 14,786 hours.
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(19) The bulkhead at station u-83 was found to have a l$' crack on the L/H side and a 2" and 4" crack on the R/H side. TAT 15,852 hours.
(20) During main base check, a crack was found in fuselage frame at station 1203 upper R/H torque box. TAT 14,639 hours.
(21) A 20" tear in the ram air inlet between stations 660 and 680 was found and determined to be a result of excessive corrosion .between the skin and strap. TAT 15,450 hours.
(22) Extensive corrosion was found below the floor of the forward cargo compartment from station 480 to 7~).
(23) Ultrasonic inspection disclosed severe corrosion along the sides of the ram air splitter vein and around the ram air door actuator rod holes and a 16” crack underneath the splitter vein from station 642 to 658. TAT 15,678 hours.
(24) The NIX collar forward segment was found cracked and the reporting operator attributed the crack to corrosion between the faying surfaces of the collar and bushing. TSR 6,234 hours.
* (25) A 12" crack was found in #l pylon fitting, P/N 65-18722-3.
TAT 4,259 hours.
b. Wing;
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(5) * l During a main base check, the upper #lO left wing stringer at station 656 was found cracked. TAT 14,536 hours.
The R/H MLG trunnion support beam, P/N 65-16230-4 (7079-T6 MTL) * has been found cracked. TAT 14877 hours.
During scheduled inspection, the L/H flap O/B carriage support was found broken, P/N 69-39601-l. TAT 14,876 hours.
Routine inspections disclosed six broken lobes on the R/H I/B aileron balance panel forward hinge at a TAT of 14,056 hours and ten broken lobes at a TAT of 15,400 hours. Nineteen forward hinge lobes were found broken on the L/H O/B aileron O/B panel at a TAT of 16,748 hours.
A main base inspection disclosed the R/H wing rib at station
686.5 cracked at the top at stringers #12 and 13 and at the bottom at stringer #6. The rib at station 629 was also cracked at the top at stringer #lb. The top stringer ##c station 601 and top stringer #9c at station 686.5 were also cracked. TAT 15,270 hours.
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(6) The O/B aileron lockout support assembly was found broken at station 661.25 on the R/H wing. TAT 6,577 hours.
(7) During inspection, corrosion was found at the R/H wing station 422 front spar lower cap. TSO 10,659 hours.
(8) A cracked R/H MU trunnion forward support wing attach fitting was found during scheduled maintenance check, fitting P/N 69-19296-2. TAT 14,794 hours.
(9) Routine service check disclosed the L/H wing O/B leading edge mid-flap interspar rib cracked in two places at WBL 319.
TAT 11,647 hours.
(10) Routine inspection disclosed two cracks in the R/H aileron O/B control rod, P/N 65-23544-l. TAT 6,804 hours. Similar cracks have also been found in the L/H aileron control rod.
(11) A 2 3/4” crack was found in support P/N 65-21640-1 at station 388, L/H I/B flap jackscrew forward attachment. TAT 6,849 hours.
(12) Scheduled inspection disclosed heavy corrosion on R/H wing rear spar lower chord at station 601.5. TAT 20,030 hours.
(13) Ultrasonic inspection disclosed a cracked MLG beam lower left support link pin, P/N 69-14908 at body station 940. The crack was three-fourths way around the circumference of the link pin.
TAT 16,604 hours.
(14) On scheduled inspection, found #2, 1113 and #14 outboard spoiler actuator support fitting cracked. TAT 13,151 hours.
(15) Routine inspection revealed an 8-inch crack in radius of upper spar cap at station 720 right wing. TAT 14,452 hours.
(16) During inspection found L/H inboard flap drive gear box cracked at three mounting lugs. TAT 15,517 hours.
(17) Found right inboard flap inboard track cracked at mount bolt hole for landing gear support beam.
(18) During inspection found corrosion at R/H W. S. 422 front spar lower cap, vertical tang. TSO 10,659 hours.
(19) No. 7 spoiler actuator rod end failed and rod penetrated flight spoiler. TAT 20,069 hours.
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c. Empennage.
(1) Forward hinge lobes on the R/H elevator 81 balance panel were broken. TAT 14,255 hours.
* (2) During overhaul, a crack was found in the center section rear spar forging of the R/H horizontal stabilizer. TAT 14,113 dr hours.
(3) The L/H inner flange of the vertical fin stiffener #9 at station 133.8 was found cracked. TAT 10,658 hours.
(4) The #3 and #5 L/H elevator balance panels forward hinge lobes were found broken. Number 3 panel had 29 broken and #5 panel had six broken. TAT 14,056 hours.
(5) A 2%" crack was found in the L/H elevator hinge support at the O/B end of #3 balance panel. TAT 14,056 hours.
(6) A 4" crack in the lower skin panel and a crack in the stiffener were found at station 114 R/H elevator. TAT 14,056 hours.
(7) During routine inspection, the trailing edge rib at station
136.5 R/H horizontal stabilizer was found cracked. TAT 9,244 hours. Cracked trailing edge ribs were also found in the L and R horizontal stabilizer at station 114.97 at a TAT of l 5,274 hours.
(8) A 10" crack was detected in the lower L/H elevator skin at the skin at the O/B end of the elevator tab. TAT 5,881 hours. A 2" crack was also found in the R/H elevator lower skin at O/B end of the tab. TAT 5,563 hours.
(9) A crack was found in the front spar web of the vertical fin aft of station 1183. TAT 15,256 hours.
(10) Scheduled inspection disclosed a cracked and broken stringer in the vertical fin R/H side at approximately station 160.
TAT 2,159 hours.
(11) Routine inspection disclosed a 1" crack in the R/H horizontal stabilizer rear lower spar vertical leg at station 200. TAT 15,800 hours.
(12) A 1" crack was found in the vertical leg of the R/H horizontal stabilizer lower spar cap at station 135. TAT 15,828 hours.
(13) During scheduled inspection, cracks were found in two elevator hinge support brackets, P/N 65-16931-1 at stations 99.79 and
136.5.
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