AC 20-78

11 July 72 AC 20-78 CHAPTER 3. FUSELAGE

12. DC-8 AIRCRAFT MAINTENANCE INFORMATION. The following 1s & listing of significant maintenance difficulties that have been reported by air carriers. This information may be useful in identifying structural inspection areas. Except where noted, fuselage structural references apply to left and right sides of the fuselage.

Tail cone structure has been found cracked. SB 53-17 The cracks are a result of sonic vibration 10/5/60 which is prevalent in the tail cone area SB 53-11 during operation of the aircraft. Rev 2 5/1/61 SB 53-13 Rev 2 3/24/61 SB 53-19 11/1/60 SB 53-25 Rev 1 2/27/62

b. Cracks have been reported in the aft vertical SB 53-21 stiffeners of the 0/B MG wheel well webs. 3/24/61

c. Cracked fuselage to skin shear clips have been found cracked on aircraft with 5,000 hours Rev 2 SB 53-28 flight time. The affected areas are at F/S 6/26/53 Y 640.000 between longerons 22 and 23 and F/S Y 660.000 between the cusp line and longeron 23.

d. Cracks have been found in longeron 24 at F/S SB 53-32

980.000 on aircraft with 10,000 or more Rev l flight hours. 9/17/65

e. Cracks in the MG I/B door actuating cylinder support fittings have been reported. SB 53-33 1/21/66 fittings are located on the left and right sides of the keel beam at F/S 920.000.

Cracks in the domed aft pressure bulkhead have been reported. Cracks were a result of SB 53-41 10/17/67 fatigue and occurred at approximately 15,000 flight hours.

Cracked vertical angles located at the upper SB 53-46 portion of the aft flat pressure bulkhead 3/28/68 have been reported by one operator on an aircraft with 14,000 flight hours.

Chap 3 Par 12 Page 11

AC 20-78 11 July 72

h. Fuselage skin corrosion has been found on SB 53-53 an aircraft with approximately 25,000 12/20/68 flight hours. The corrosion was in the scuff plate area of passenger, service, and cargo doors.

Fuselage frame fittings have been found AOL 8-169A corroded on aircraft with between 21,000 8/30/68 and 30,000 flight hours. The corroded fittings were located at F/S 920 and 960.

Chap Page 12 Par 1

11 July 72 AC 20-78 CHAPTER 4. FLIGHT CONTROLS

13. DC-8 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 noted, ilight control structural references apply to left and right sides.

a. Flap support fittings on the aft side of SB A27-5 the rear spar have been found cracked. Reissue #2 Examination indicated stress corrosion 3/1/61 developed and cracks propagated from the corroded area.

b. Operators have experienced cracking of the SB 27-48 rudder nose rib webs at the three hinge point locations and in the rib to spar attach angles, (Stations Zy 105.000, Zy 162.906, and Zr 220.813).

c. An alert bulletin was issued by the manufacturer SB A27-66 due to a report of a left 0/B elevator geared 6/20/60 tab push rod being broken at the aft rod end fitting, rod P/N 4702890.

d. The aileron reversion mechanism forward gripper SB 27-95 has been found cracked at the lower clevis ends Reissue #l which attach to the end of the aileron tab 5/18/62 lockout cylinder piston end fitting.

e. Clevis P/N 2619862 on the rudder lockout SB A27-100 cylinder was found broken. This allowed Reissue #2 the rudder to revert to manual with hydraulic 9/24/64 and power still on causing the rudder to lock AD 61-6-4 in its last position.

f. Cracks have been found in the aileron tab SB 27-115 lockout mechanism support brackets Rev #1 10/25/01 P/N 4643350. and AD 62-2-4

g. Wing flap actuating cylinder barrels have SB 27-118 been found cracked. Examination of failed Reissue #2 cylinders disclosed corrosion in the internal 12/4/61 portion of the barrel.

Wing flap support track assemblies have been SB 27-123 found cracked at W/S Xp 219.498. Analysis 12/27/61 indicated the cracks could have been caused by stress corrosion.

Chap 4 Par 13 Page 13

AC 20-78 11 July 72 Wing flap rod end bearings have been found SB 27-127 cracked with more than 5000 hours. Rev. #2 The cracked bearings were located at W/S 1/28/64 and 98 and 219 in the area of the bearing case AD 62-12-4 adjacent to the bearing dust shield.

j• Wing flap actuating cylinder barrels have SB 27-134 failed. Both mid-wing and 0/B actuating Reissue #1 cylinders have been found cracked. 10/19/62 SB A27-134 Reissue #2 10/13/64 and ADS 62-16-2 and 62-24-4 Wing flap link assemblies P/N 5644642-501 SB 27-137 at W/S X 97.906 and P/N 5644644-501 at Rev. #1 W/S Xp 219.498 have been found broken on 1/8/64 several occasions.

1. Cracks have been found along the horizontal SB 27-142 centerline of the forward attach lugs of the flap Reissue #l link support assemblies on aircraft with 5/15/63 more than 8000 hours,

m. Operators have experienced failure of the SB 27-159 0/B wing slot assembly, P/N 3770143-1, on Reissue #1 aircraft with four percent extended wing 2/23/65 leading edge.

n. Cracked flap hinge support fittings have been SB 27-217 found in the 0/B flap center hinge base Rev. #1 assembly on aircraft with between 8000 and 10/9/68 11,000 hours..

o. Rudder link, P/N 2619201, failures have SB 27-218 occurred on aircraft with 23,000 to 26,000 Rev. #1 hours. 10/18/68 Cracked aileron tab rod end assemblies have SB 27-223 been found on aircraft with 3,000 to 29,000 12/6/68 hours.

Chap 4 Page 14 Par 13

11 July 72 AC 20-78 CHAPTER 5. LANDING GEAR DC-8 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 noted, landing gear structural references apply to left and right landing gear.

Intergranular corrosion and cracking have SB 32-28 been reported on main and nose gear Rev. #1 aluminum 'B" nuts on landing gear pipe 11/13/61 assemblies.

Cracks have been found in the MIG retract SB 32-51 strut barrels. The cracks occurred in a Reissue #1 flash weld area of the barrel. Rev. #1 6/28/61

c. Operators have reported failure of the bolt SB 32-53 assembly attaching the aft brake compensating Reissue #1 links to the MIG piston. 5/4/61 Cracked and broken MIG bogie beam pivot bolts SB. 32-60 have been found which appeared to be caused Reissue #l by lack of lubrication. 8/3/61 Rev. #1 2/27/62 MIG bogie beam trim cylinder forward attach SB 32-61 bolts have failed allowing the bogie beam Reissue #l to rock freely without snubbing. 2/2/62

f. MIG actuating cylinder upper attach brackets SB A32-76 P/N 5641950-1, -2, -501, or -502 have been Reissue #l found broken. Rev. #l 4/5/62 and AD 62-23-3 MLG bungee cylinder rod-end eyebolts have been SB A32-87 found cracked in the threaded area. Byebolt Reissue #1 P/N 4772490-1. 5/4/62

h. Fatigue cracks have been found in the support SB 32-89 flange and O-ring groove of the MIG retract Reissue #l cylinder gland assembly on aircraft with 7/16/63 5,000 or more hours flight time.

Cracks have been found in the MIG forward axle SB 32-91 beam pivot arm upper lug. 11/12/62 Chap S Par 14 Page 15

AC 20- 78 11 July 72 J. MIG forward bogie beam swivel pin lower lugs McDaco letter have been found cracked and failures of bogie C1-78-987/WBM beams in "critical area" on the bottom of Rev. #1 7/17/64 certain forward bogie beams have occurred. and C1-78-228 The failures were determined to be a result 2/16/65 and of corrosion. AD 68-26-7 Failures of the nose gear forward door operating SB 32-104 mechanism bellcrank have occurred on aircraft 9/17/64 having more than 7,000 hours flight time.

1. Several operators reported nose gear uplatch SB 32-112 upper link assemblies broken at the lower 11/8/65 attach point.

m. Malfunctions of the MIG uplatch hook have been SB 32-113 due to inadequate lubrication of the pivot bolt Rev. #1 bearings. Aircraft fuselage #348 and subsequent 8/10/67 were modified prior to delivery. The modification replaced the pivot bolt with one that permits lubrication without removing the bolt.

Some operators have reported binding of the SB 32-114 bearing in the lower support bracket of the MIG 3/23/66 I/B door latch due to corrosion.

0. There have been numerous instances of minute SB 32-140 cracks in the machine threaded root of the 11/6/68 main gear bogie trim cylinder eyebolt. These cracks were detected on aircraft with approximately 15,000 flight hours. Manufacturer recommends replacing bolt, with a bolt incorporating rolled threads. This applies to series 60 aircraft; fuselage #445 and subsequent were modified prior to delivery.

P. Failures of landing gear bogie beams have AD 64-5-2 occurred due to cracks initiated by corrosion in areas where the bogie beam surface had been damaged.

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11 July 72 AC 20-78 CHAPTER 6. PYLONS/NACELLES DC-8 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 noted, pylon/nacelle structural references apply to left and right sides of the aircraft.

Access doors have been found cracked on SB 54-7 the R/H side of nacelles in the area of 5/18/60 cooling air exit ducts.

Cracks have been found in the tunnel and SB 54-17 junction box of each pylon. The cracks Rev. #1 occurred due to the welded seam which 9/26/61 joins the tunnel to the junction box.

Cracks have been found in the zee angles SB 54-20 located on the left side nacelle door in Rev. #1 the area of the upper aft pylon drain 8/7/61 fitting support.

d. Lower 0/B pylon-to-wing attach angles and SB 54-24 flexible ribs below pylon spars have been Reissued T/25/62 found cracked. and Revised 8/20/62

e. The vertical leg of the 0/B spar cap on SB 54-27 the O/B pylon upper spar was found cracked 1/26/62 at station Yop 246.000.

1. Failure of the upper I/B spar cap structure SB A54-33 has occurred in the O/B pylons in the area Rev. #2 1/24/64 oi station I 230 at the edges of support and AD 62-27-4 fitting P/N 3647306-501.

g. Failure of the upper 0/B spar cap structure SB 54-34 has occurred in the I/B pylons in the area of Reissue #l stations Yip 225 to Yip 233. 7/6/64 and AD 65-5-2

h. Cracks have been found in the I/B and 0/B Daco Service pylon stub wing structure. The cracks have Engineering occurred in skins, bulkheads, and spar caps. Letter C1-78-2016/DBA 10/18/66 SB 54-57 Rev. #1 12/9/69 and AD 67-5-3 Chap 6 Par 15 Page 17

AC 20- 78 11 July 72 Skin and doubler cracks have been found on SB 54-41 the 0/B side of the O/B pylons between Rev. #1 aircraft vith four percent extended wing <30.000 and Top 240.000 on 9/27/68 leading edge. Aircraft fuselage #148 and and subsequent were modified prior to delivery.

Cracks have been found on 0/B pylon stub SB 54-42 wings on aircraft with more than 6,000 1/6/67 flight hours. The cracks occurred at station Xw 454.000 and the I/B intersection adjacent to the leading edge lower slot door.

Operators have reported cracks in the SB 54-43 Pylon cant bulkhead fitting on aircraft Rev. #1 with 17,000 and 18,000 flight hours. 5/12/67

1. Cracks have been found in the D-duct spars, SB 54-44 adjacent structure, and pylon skin of the Rev. #1 I/B pylons. The reported cracks were on 2/10/67 aircraft with 14,000 to 21,000 flight hours between station Lip 204.000 and Iip 220.000.

Cracks have been found in the I/B pylon stub SB 54-49 wing skin and internal doubler at the cutout 8/25/67 for the wing leading edge lower slot door on The cracks were detected in the area aft of Thrust reverser stow latch pivot bolt failures SB 54-52 have occurred. This applies to series 60 3/28/68 aircraft; fuselage #332 and subsequent were modified prior to delivery.

Five failures of forward thrust reverser stow SB 54-53 latch on series 60 aircraft at approximately 8/20/68 2,000 flight hours have occurred.

An alert bulletin was issued due to reported SB A54-58 cracks in P/N 5753016-1 and -2 wing skin Rev #1 pylon support doubler. The cracks originated 12/16/68 at the forward edge of the doubler in the intersection of the I/B side of the I/B pylons and the wing front spar lower cap at W/S Xw

234.000. Aircraft fuselage #451 and subsequent were modified prior to delivery. Although cracks were not reported in 0/B pylons, the structure is similar and should also be inspected.

Chap 6 Page 18 Par 15

11 July 72 AC 20-78 CHAPTER 7. STABILIZERS

16. DC-8 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. ixcept where noted, stabilizer structural references apply to leit and right sides.

Cracks have been reported in the formers SB 55-7 of the vertical stabilizer leading edge at 10/18/61 stations Zes 117.250 to Zfs 179.750 and Zfs SB 55-11

186.000 to Zfs 350.500. 5/2/63

b. Cracks have been detected in the radius of SB 55-8 the vertical leg of the horizontal stabilizer Rev. 1 closing bulkhead caps, P/N 5654549-1, -2 8/13/62 -501, and -502. The cracks have been up to 4" in length in the aft end of the caps.

Operators have reported cracked formers in SB 55-10 the horizontal stabilizer leading edges 5/2/63 originating at the aft end of the formers.

Flying time on aircraft with reported cracks was in excess of 5,000 hours.

Fatigue cracking has been reported in the SB 53-45 vertical stabilizer front spar to fuselage Rev. #1 attach fitting at F/S 1500.000 on aircraft 3/12/68 with 15,000 to 20,000 fight hours.

Chap ar 16 Page 19 (and 20)

11 July 72 AC 20-78 CHAPTER 8. MISCELLANEOUS

17. DC-8 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.

a. Cracks have been found in the vertical SB 51-2 flange of the keel beam fittings between Reissue #1 the center and rear spar. 1/3/61 Operators have reported cracks in fuselage SB 51-7 frame at refrigerant condenser forward 9/3/63 exhaust flap hinges.

C. Forward and aft passenger entrance door SB 52-14 mechanism housings have been found cracked. 9/26/60 The cracks were a result of maladjustment of the latching mechanism.

d. The forward upper cargo door mechanism apex SB 52-47 pin assembly has been found cracked on aircraft rev. #1 with approximately 8,000 hours. 8/16/68 Chap 8 Par 17 Page 21 (and 22)