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2010-13-08: We are adopting a new airworthiness directive (AD) to supersede AD 2006-08-09, which applies to all Air Tractor, Inc. (Air Tractor) Models AT-802 and AT-802A airplanes. AD 2006-08-09 currently requires you to repetitively inspect (using the eddy current method) the two outboard fastener holes in both of the wing main spar lower caps at the center splice joint for cracks and repair or replace any cracked spar cap. Since we issued AD 2006-08-09, we have determined we need to clarify the serial numbers (SNs) of the Models AT-802 and AT- 802A airplanes affected by that AD. Additionally, we are adding an option of modifying the wing main spar lower caps to extend the safe life limit on the affected airplanes. Consequently, this AD would keep the actions of AD 2006-08-09, clarify the affected SNs, and add a modification option to extend the safe life limit. We are issuing this AD to detect and correct cracks in the wing main spar lower cap at the center splice joint, which could result in failure of the spar cap and lead to wing separation and loss of control of the airplane. DATES: This AD becomes effective on July 28, 2010. As of April 21, 2006 (71 FR 19994, April 19, 2006) the Director of the Federal Register approved the incorporation by reference of Snow Engineering Co. Process Specification 197, page 1, revised June 4, 2002; pages 2 through 4, dated February 23, 2001; and page 5, dated May 3, 2002; Snow Engineering Co. Process Specification 204, Rev. C, dated November 16, 2004; Snow Engineering Co. Service Letter 215, page 5, titled "802 Spar Inspection Holes and Vent Tube Mod,'' dated November 19, 2003; Snow Engineering Co. Service Letter 240, dated September 30, 2004; Snow Engineering Co. Drawing Number 20975, Sheet 2, Rev. A, dated September 1, 2004; Snow Engineering Co. Drawing Number 20975, Sheet 3, dated January 6, 2005; and Snow Engineering Co. Drawing 20995, Sheet 2, Rev. C, dated September 28, 2004, listed in this AD.
2009-23-51: This document publishes in the Federal Register an amendment adopting Airworthiness Directive (AD) 2009-23-51, which was sent previously to all known U.S. owners and operators of Sikorsky Aircraft Corporation (Sikorsky) Model S-92A helicopters by individual letters. This AD requires cleaning and inspecting each main gearbox (MGB) assembly mounting foot pad and rib for a crack and corrosion. If you do not find a crack, the AD requires applying a corrosion preventive compound. If you find a crack, the AD requires replacing the MGB before further flight. If you find corrosion, bubbled paint, or paint discoloration, the AD also requires you to repair the MGB before further flight. This amendment is prompted by reports of cracks in the MGB mounting foot pads and foot ribs. This condition, if not detected, could result in loss of the MGB and subsequent loss of control of the helicopter.
57-20-04: 57-20-04 VICKERS: Applies to All Viscount 700 Series Aircraft Equipped With 14-Inch Stroke Oleos. Compliance required as indicated. As a result of investigations and tests by Vickers it has been found necessary to limit the life of the trunnion pins and bearing bolts of the main landing gear retraction jack (cylinder) assembly, right and left, Drawing No. 77450 sheet 7. Accordingly, Vickers-Armstrong insured the following corrective measures with concurrence of the British Air registration Board. The FAA concurs with this action and considers compliance therewith mandatory: 1. At the ram end of the retraction jack, attached to the landing gear actuating lever assembly, replace the trunnion fork end P/N 74450-99 and pin P/N 7450-101, at 2,500 flights; and bearing bolt P/N 74450-103 at 5,000 flights. On aircraft that have exceeded 2,500 flights a precautionary visual inspection for cracks on the trunnion P/N 74450-99 is required at the next daily inspection with particular attention being paid to the flat surfaces. If cracks are found the trunnion and pin and bearing bolt must be replaced before further flight. If no cracks are found, aircraft may continue flying provided the trunnion is visually inspected for cracks at every daily check until replaced. 2. At the retraction jack cylinder end, attached to structure joint assembly, replace the trunnion block P/N 74450-79, pin P/N 74450-81 and bearing bolt P/N 74450-341 or 74450- 83 at 7,000 flights.
2021-11-15: The FAA is adopting a new airworthiness directive (AD) for certain International Aero Engines AG (IAE) V2500 model turbofan engines. This AD was prompted by an analysis performed by the manufacturer after an event involving an uncontained failure of a high- pressure turbine (HPT) 1st-stage disk that resulted in high-energy debris penetrating the engine cowling. This AD requires the performance of an ultrasonic inspection (USI) of the HPT 1st-stage disk and HPT 2nd-stage disk and, depending on the results of the inspections, replacement of the HPT 1st-stage disk or HPT 2nd-stage disk. The FAA is issuing this AD to address the unsafe condition on these products.
91-02-02: 91-02-02 BOEING: Amendment 39-6851. Docket No. 90-NM-125-AD. \n\n\tApplicability: Model 757 series airplanes, certificated in any category. \n\n\tCompliance: Required within the next 48 months after the effective date of this AD, unless previously accomplished. \n\n\tTo preclude cross connection of engine and cargo compartment fire extinguishing wiring and plumbing during maintenance, accomplish the following: \n\n\tA.\tModify the engine and cargo compartment fire extinguishing system wiring and plumbing in accordance with Boeing Service Bulletin 757-26-0020, dated March 22, 1990. Accomplishment of this modification constitutes terminating action for the repetitive inspections and functional tests required by Airworthiness Directive 89-03-51, Amendment 39-6213, on Boeing Model 757-200 airplanes following maintenance on the engine and cargo compartment fire extinguishing wiring and plumbing. \n\n\tNOTE: The modification required by this paragraph was incorporated in production on airplanes, line numbers 256 and subsequent. Accordingly, this paragraph terminates the repetitive inspection and functional test requirements of AD 89-03-51 for those airplanes. \n\n\tB.\tAn alternate means of compliance or adjustment of the compliance time, which provides an acceptable level of safety, may be used when approved by the Manager, Seattle Aircraft Certification Office (ACO), FAA, Transport Airplane Directorate. \n\n\tNOTE: The request should be submitted directly to the Manager, Seattle ACO, and a copy sent to the cognizant FAA Principal Inspector (PI). The PI will then forward comments or concurrence to the Seattle ACO. \n\n\tC.\tSpecial flight permits may be issued in accordance with FAR 21.197 and 21.199 to operate airplanes to a base in order to comply with the requirements of this AD.\n \n\tAll persons affected by this directive who have not already received the appropriate service documents from the manufacturer may obtain copies upon request to Boeing Commercial AirplaneGroup, P.O. Box 3707, Seattle, Washington 98124. These documents may be examined at the FAA, Northwest Mountain Region, Transport Airplane Directorate, 1601 Lind Avenue SW., Renton, Washington. \n\n\tThis amendment (39-6851, AD 91-02-02) becomes effective on February 4, 1991.
93-05-17: 93-05-17 BOEING: Amendment 39-8521. Docket No. 92-NM-10-AD. Supersedes AD 82-08- 09, Amendment 39-4364. \n\n\tApplicability: Applies to Model 707/720, series airplanes, listed in Boeing Service Bulletin 2983, Revision 5, dated January 31, 1991; Model 727 series airplanes listed in Boeing Service Bulletin 727-53-0086, Revision 11, dated August 8, 1991; and Model 737 series airplanes listed in Boeing Service Bulletin 737-53-1023, Revision 11, dated May 16, 1991; certificated in any category. \n\n\tCompliance: Required as indicated, unless previously accomplished. \n\n\tTo prevent depressurization as a result of failure of the control cabin window post structure, accomplish the following: \n\n\t(a)\tInspect the E-F window posts for cracks in accordance with the schedule set forth in Table 1, 2, or 3 of this AD, as applicable: \n\n\n\t\t\t\t\tTABLE 1 \n\n\t\t\tModel 707/720 E-F Window Post Inspection \n\t\t\t(Applicable Boeing Service Bulletin 2983) \n\n\nAirplane\nCondition\nInspection Requiredin accordance with\nRevision 4, 5, or 6\nof Service Bulletin\nInitial\nInspection\nnot to exceed\n(flight cycles)\nRepeat Inspection \nInterval not to exceed (flight cycles) \n1. Service Bulletin not accomplished.\nX-ray of E-F window post.\n1,650 after May 21,1982 (effective date of AD 82-08-09), or prior to accumulation of 11,650, whichever \noccurs later. \n3,300 \n2. Repaired or modified per Original Issue of Service Bulletin.\t\nX-ray of E-F window post.\n1,650 after May 21, 1982, or prior to accumulating 10,000 after repair or modification, whichever occurs later.\n3,300 \n3. Repaired or modified per Revision 1, 2, 3, 4, 5, or 6 of Service Bulletin. (Modification was accomplished without using eddy current inspection to verify structure was free of cracks.) \nClose visual for cracks of external doubler and the\texposed portion of the E-F window post with the #2 sliding window open. \n1,650 after May 21, 1982; or prior to accumulating 16,650 after repair or mod- ification; whichever occurs later. \n3,300 \n4. Repaired or modified per Revision 1 of Service Bulletin.\t\nVisual inspection for sufficient edge margin of all of the strap fastener holes. \n1,650 after effective date of this AD. \nNone \n5. Modified per Revision 2, 3, 4, 5, or 6 of Service Bulletin (verified no cracks in structure using eddy current inspection described in Revision 4 or 5 of Service Bulletin).\nClose visual for\tcracks of external doubler and the exposed portion of the E-F window post with the #2 sliding window open. \n3,300 after effective date of this AD, or 24,000 after strap installation, whichever is later. \n3,300 \n\n\t\t\t\t\t TABLE 2 \n\n\t\t\t Model 727 E-F Window Post Inspection\n\t\t\t(Applicable Boeing Service Bulletin 727-53-0086) \n\n\nAirplane\nCondition\nInspection Required\nin accordance with\nRevision 6, 7, 8, 9,10, or 11 of Service Bulletin\nInitial\nInspection\nnot to exceed\n(flight cycles)\nRepeat Inspection \nInterval not to exceed (flight cycles) \n1. Service Bulletin not accomplished.\nX-ray of E-F window post.\n1,650 after May 21, 1982 (effective date of AD 82-08-09), or \tprior to accumulation of 11,650, whichever \noccurs later. \n3,300 \n2. Repaired or modified per Original Issue or Revision 1 of Service Bulletin.\nX-ray of E-F window post.\n1,650 after May 21, 1982, or prior to accumulating 10,000 after repair or modification, whichever occurs later.\n3,300 \n3. Repaired or modified per modified per Revision 2, 3, 4, 5, 6, 7, 8, 9, 10, or 11 of Service Bulletin. (Modification was accomplished without using eddy current inspection to verify structure was free of cracks.) \nClose visual for\tcracks of external doubler and the exposed portion of the E-F window post with the post with the #2 sliding window open.\n1,650 after May 21, 1982, or prior to accumulating 16,650 after repair or modification, whichever occurs later.\n3,300 \n4. Repaired or modified per Revision 9 or 10 of Service Bulletin.\nVisual inspection for sufficient edge margin of all of the strap fastener holes.\n1,650 after effective date of this AD. \nNone \n5. Modified per Revision 2, 3, 4, 5, 6, 7, 8, 9, 10, or 11 of Service Bulletin\t(verified no cracks in structure using eddy current inspection described in Revision 6, 7, 8, 9, 10, or 11).\nClose visual for\tcracks of external doubler and the exposed portion of the E-F window post with the #2 sliding window open. \n3,300 after effective date of this AD, or 24,000 after strap installation, whichever occurs later. \n3,300 \n\n\t\t\t\t\tTABLE 3 \n\t\t\t\tModel 737 E-F Window Post Inspection \n\t\t\t(Applicable Boeing Service Bulletin 737-53-1023) \n\n\nAirplane \nCondition\nInspection Required\nin accordance with\nRevision 6, 7, 8, 9,10, or 11 of Service Bulletin\nInitial Inspection\nnot to exceed\n(flight cycles)\nRepeat Inspection \nInterval not to exceed (flight cycles) \n1. Service Bulletin not accomplished.\nX-ray of E-F window post.\n2,750 after May 21, 1982 (effective date of AD 82-08-09), or \tprior to accumulationof 12,750, whichever \noccurs later. \n5,500 \n2. Repaired or modified per Original Issue or Revision 1 or 2 of Service Bulletin.\nX-ray of E-F window post.\n2,750 after May 21, 1982, or prior to accumulating 10,000 after repair or modification, whichever occurs later.\n5,500 \n3. Repaired or modified per modified per Revision 3, 4, 5, 6, 7, 8, 9, 10, or 11 of Service Bulletin. (Modification was accomplished without using eddy current inspection to verify structure was free of cracks.) \nClose visual for\tcracks of external doubler and the exposed portion of the E-F window post with the post with the #2 sliding window open.\n1,650 after May 21, 1982, or prior to accumulating 16,650 after repair or modification, whichever occurs later.\n5,500 \n4. Repaired or modified per Revision 9 or 10 of Service Bulletin.\nVisual inspection for sufficient edge margin of all of the strap fastener holes.\n2,750 after effective date of this AD. \nNone \n5. Modified per Revision 3, 4, 5, 6, 7, 8, 9, 10, or 11 of Service Bulletin\t(verified no cracks in structure using eddy current inspection described in Revision 6, 7, 8, 9, 10, or 11).\nClose visual for\tcracks of external doubler and the exposed portion of the E-F window post with the #2 sliding window open. \n3,300 after effective date of this AD, or 24,000 after strap installation, whichever occurs later. \n5,500 \n\n\t(b)\tInspect the E-N window post for cracks in accordance with the schedule set forth in Table 4, 5, or 6 of this AD, as applicable: \n\n\t\t\t\t\t TABLE 4 \n\n\t\t\t\tModel 707/720 E-N Window Post Inspection \n\t\t\t\t (Applicable Boeing Service Bulletin 2983) \n\n\nAirplane\nCondition\nInspection Required\nin accordance with\nRevision 5 or 6 of Service Bulletin\nInitial\nInspection\nnot to exceed\n(flight cycles)\nRepeat Inspection \nInterval not to exceed (flight cycles) \n1. Service\tBulletin not accomplished; or repaired or\t modified per Original Issue or Revision 1, 2, 3, or 4 of Service Bulletin. \nX-ray of E-N windowpost.\n1,650 after effective date of this AD, or prior to the accumulation of 11,650, whichever occurs later. \n3,300\n2. Repaired per Revision 5 or 6 of Service Bulletin (cracks in structure).\t\nX-ray of E-N window post; and close visual of external strap.\t\n1,650 after effective date of this AD, or prior to accumulating 16,650 after repair, whichever occurs later. \n3,300 \n3. Modified per Revision 5 or 6 of Service Bulletin (no cracks in structure).\nX-ray of E-N window post; and close visual of external strap.\n3,300 after effective date of this AD, or 24,000 after strap installation, whichever occurs later. \n6,600 \n \n\t\t\t\t\t TABLE 5 \n\n\t\t\tModel 727 E-N Window Post Inspection \n\t\t (Applicable Boeing Service Bulletin 727-53-0086) \n\n\n\nAirplane\nCondition\nInspection Required\nin accordance with\nRevision 9, 10, or 11 of Service Bulletin\nInitial\nInspection\nnot to exceed\n(flight cycles)\nRepeat Inspection \nInterval not to exceed (flight cycles) \n1. Service\tBulletin not accomplished; or repaired or modified per Original Issue or Revision 1, 2, 3, 4, 5, 6, 7, or 8 of Service Bulletin. \nX-ray of E-N window post.\n1,650 after effective date of this AD, or prior to the accumulation of 11,650, whichever occurs later. \n3,300\n2. Repaired per Revision 9, 10, or 11 of Service Bulletin (cracks in structure).\t\nX-ray of E-N window post; and close visual of external strap.\t\n1,650 after effective date of this AD, or prior to accumulating 16,650 after repair, whichever occurs later. \n3,300 \n3. Modified per Revision 9, 10, or 11 of Service Bulletin (no cracks in structure).\nX-ray of E-N window post; and close visual of external strap.\n3,300 after effective date of this AD, or 24,000 after strap installation, whichever occurs later. \n6,600 \n\n\n\t\t\t\t\t TABLE 6 \n\n\t\t\tModel 737 E-N Window Post Inspection\n\t\t (Applicable Boeing Service Bulletin 737-53-1023 \n\n\nAirplane\nCondition\nInspection Required\nin accordance with\nRevision 9, 10, or 11of Service Bulletin\nInitial\nInspection\nnot to exceed\n(flight cycles)\nRepeat Inspection \nInterval not to exceed (flight cycles) \n1. Service\tBulletin not accomplished; or repaired or modified per Original Issue or Revision 1, 2, 3, 4, 5, 6, 7, or 8 of Service Bulletin. \nX-ray of E-N window post.\n2,750 after effective date of this AD, or prior to the accumulation of 12,750, whichever occurs later. \n5,500\n2. Repaired per Revision 9, 10, or 11 of Service Bulletin (cracks in structure).\t\nX-ray of E-N window post; and close visual of external strap.\t\n2,750 after effective date of this AD, or prior to accumulating 17,750 after repair, whichever occurs later. \n5,500\n3. Modified per Revision 9, 10, or 11 of Service Bulletin (no cracks in structure).\nX-ray of E-N window post; and close visual of external strap.\n5,500 after effective date of this AD, or 24,000 after strap installation, whichever occurs later. \n11,000\n\n\t(c)\tReinspect the affected areas for cracks at intervalsnot to exceed those specified in the "Repeat Inspection Interval" column of the Tables of paragraphs (a) and (b) of this AD.\n \n\t(d)\tCracks and short edge margins must be repaired, prior to further flight, in accordance with the "Accomplishment Instructions" of the applicable service bulletin specified in paragraph (d)(1), (d)(2), or (d)(3) of this AD. After such repair, inspections must continue in accordance with the Tables of paragraphs (a) and (b) of this AD. \n\n\t\t(1)\tFor Boeing Model 707/720 series airplanes: Boeing Service Bulletin 2983, Revision 5, dated January 31, 1991; or Revision 6, dated November 12, 1992. \n\n\t\t(2)\tFor Boeing Model 727 series airplanes: Boeing Service Bulletin 727-53- 0086, Revision 11, dated August 8, 1991. \n\n\t\t(3)\tFor Boeing Model 737 series airplanes: Boeing Service Bulletin 737-53- 1023, Revision 11, dated May 16, 1991. \n\n\t(e)\tAn alternative method of compliance or adjustment of the compliance time that provides an acceptable level of safetymay be used if approved by the Manager, Seattle Aircraft Certification Office (ACO), FAA, Transport Airplane Directorate. Operators shall submit their requests through an appropriate FAA Principal Maintenance Inspector, who may add comments and then send it to the Manager, Seattle ACO. \n\n\tNOTE: Information concerning the existence of approved alternative methods of compliance with this AD, if any, may be obtained from the Seattle ACO. \n\n\t(f)\tSpecial flight permits may be issued in accordance with FAR 21.197 and 21.199 to operate the airplane to a location where the requirements of this AD can be accomplished. \n\n\t(g)\tThe repairs shall be done in accordance with Boeing Service Bulletin 2983, Revision 5, dated January 31, 1991; Boeing Service Bulletin 2983, Revision 6, dated November 12, 1992; Boeing Service Bulletin 727-53-0086, Revision 11, dated August 8, 1991; and Boeing Service Bulletin 737-53-1023, Revision 11, dated May 16, 1991; as applicable. This incorporation by reference was approved by the Director of the Federal Register in accordance with 5 U.S.C. 552(a) and 1 CFR Part 51. Copies may be obtained from Boeing Commercial Airplane Group, P.O. Box 3707, Seattle, Washington 98124. Copies may be inspected at the FAA, Transport Airplane Directorate, 1601 Lind Avenue, SW., Renton, Washington; or at the Office of the Federal Register, 800 North Capitol Street, NW., suite 700, Washington, DC. \n\n\t(h)\tThis amendment becomes effective on May 5, 1993.
65-21-05: 65-21-05 LOCKHEED: Amdt. 39-136 Part 39 Federal Register September 11, 1965. Applies to Models 188A and 188C Series Airplanes. Compliance required as indicated. To Detect and repair cracks in the vertical stabilizer -to-fuselage attach channel, P/N 803179-5, located at Fuselage Station 1117.6, accomplish the following: (a) For airplanes with 8,000 or more hours' time in service as of the effective date of this AD, comply with (c) within the next 150 hours' time in service unless accomplished within 1,350 hours' time in service prior to the effective date of this AD, and thereafter at intervals not to exceed 1,500 hours' time in service form the last inspection. (b) For those airplanes with less than 8,000 hours' time in service as of the effective date of this AD, comply with (c) prior to the accumulation of 8,150 hours' time in service unless accomplished during the 1,350 hours' time in service from 6,650 hours' to 8,000 hours' and thereafter at intervals not to exceed1,500 hours' time in service from the last inspection. (c) Visually or by use of other FAA-approved methods, inspect the vertical stabilizer- to-fuselage attach channel, P/N 803179-5, located at F. S. 1117.6 for cracks. If a crack is found, confirm crack end by inspection with dye penetrant or an FAA-approved equivalent. (d) If a crack is found during the inspection required by (c), the following apply: (1) If the crack length does not exceed 3 inches, stop drill the crack and install angles P/N 841309-101 and P/N 841309-102 in accordance with Lockheed Drawing 841307 or an equivalent approved by the Chief, Aircraft Engineering Division, FAA Western Region, before further flight, except that the airplane may be flown in accordance with FAR 21.197 to a base where the repair can be made. (2) If the crack length exceeds 3 inches, replace the P/N 803179-5 channel with a new P/N 803179-5 channel and install angles P/N 841309-101 and P/N 841309-102 in accordance with LockheedDrawing 841307 or an equivalent approved by the Chief, Aircraft Engineering Division, FAA Western Region, before further flight, except that the airplane may be flown in accordance with FAR 21.197 to a base where the repair can be made. (e) The periodic reinspection may be discontinued for airplanes on which the cracks are repaired in accordance with (d) and for airplanes with an uncracked P/N 803179-5 channel on which the P/N 841309-101 and P/N 841309-102 angles are installed in accordance with Lockheed Drawing 841307 as a reinforcement or on which an equivalent reinforcement approved by the Chief, Aircraft Engineering Division, FAA Western Region is incorporated. (f) Upon request of the operator, an FAA maintenance inspector, subject to prior approval of the Chief, Aircraft Engineering Division, FAA Western Region, may adjust the repetitive inspection intervals specified in this AD to permit compliance at an established inspection period of the operator if the request contains substantiating data to justify the increase for such operator. This directive effective October 11, 1965.
82-18-05: 82-18-05 BOEING: Amendment 39-4444. Applies to Model 747 series freighter airplanes as listed in Boeing Service Bulletin No. 747-26-2083, Revision 1, or later FAA approved revisions, certificated in all categories. To prevent the rudder cable from possible hangup on the smoke detection tube, accomplish the following: \n\n\tA.\tWithin the next 1,500 hours time-in-service after the effective date of this AD, unless previously accomplished, modify the smoke detection tube in accordance with Boeing Service Bulletin No. 747-26-2083, Revision 1, or later FAA approved revision. \n\n\tB.\tAlternate means of compliance with the AD which provide an equivalent level of safety may be used when approved by the Manager, Seattle Area Aircraft Certification Office, FAA Northwest Mountain Region. \n\n\tC.\tSpecial flight permits may be issued in accordance with FAR 21.197 and 21.199 to operate airplanes to a base for the accomplishment of inspections and/or modifications required by this AD. \n\n\tThe manufacturer's specifications and procedures identified and described in this directive are incorporated herein and made part hereof pursuant to 5 U.S.C. 552(a)(1). \n\n\tAll persons affected by this directive who have not already received these documents from the manufacturer may obtain copies upon request to Boeing Commercial Airplane Company, P.O. Box 3707, Seattle, Washington 98124. These documents may also be examined at FAA Northwest Mountain Region, 9010 East Marginal Way South, Seattle, Washington. \n\n\tThis amendment becomes effective September 30, 1982.
2010-13-02: We are adopting a new airworthiness directive (AD) for the products listed above. This AD results from mandatory continuing airworthiness information (MCAI) originated by an aviation authority of another country to identify and correct an unsafe condition on an aviation product. The MCAI describes the unsafe condition as: A Fokker 50 operator reported an overextended MLG [main landing gear] sliding member after landing. During subsequent investigation it was found that an end stop had unscrewed itself to a certain extent. This caused the MLG torque links to move into an overcentre position against the MLG sliding member. Investigation learned that there was no lockwiring present on the two lockbolts, which hold the end stop. This condition, if not corrected, could lead to structural damage of the main gear and loss of control of the aeroplanes during the landing roll. This AD requires actions that are intended to address the unsafe condition described in the MCAI.
91-06-08: 91-06-08 BOEING: Amendment 39-6928. Docket No. 90-NM-27-AD. \n\n\tApplicability: Model 747 series airplanes, line positions 2 through 707, except Model 747-400 series airplanes, certificated in any category. \n\n\tCompliance: Required as indicated, unless previously accomplished. \n\n\tTo prevent damage to wing panels and/or electrical wiring as a result of failure of wing leading edge ducts, accomplish the following: \n\n\tA.\tPrior to the accumulation of 5,850 flight cycles, or within the next 1,850 flight cycles after the effective date of this AD, whichever occurs later, conduct a penetrant inspection and proof pressure test as follows: \n\n\t\t1.\tFor titanium T-ducts and flanged ducts: Conduct the inspection and test in accordance with the Accomplishment Instructions, Items A. through F., J., and K. of Boeing Alert Service Bulletin 747-36A2074, Revision 3, dated May 11, 1989, or Revision 4, dated September 13, 1990. If cracks or ruptures are detected, prior to further flight, repair or replace the duct in accordance with the service bulletin. \n\n\t\t2.\tFor flangeless ducts: Conduct the inspection and test in accordance with the Accomplishment Instructions, Items A. through F., J., and K. of Boeing Alert Service Bulletin 747- 36A2074, Revision 4, dated September 13, 1990. If cracks or ruptures are detected, prior to further flight, repair or replace the duct in accordance with the service bulletin. \n\n\tNOTE: For both flanged and flangeless ducts specified in paragraphs A.1. and A.2. of this AD (excluding T-ducts): The duct weld stress relieving procedure specified in Items G., H., and I. of the referenced service bulletins (and required by paragraphs B.2. and B.3. of this AD) may be accomplished in conjunction with the penetrant inspection and proof pressure test required by this paragraph, and constitutes terminating action for the requirements of paragraphs B.2. and B.3. of this AD. \n\n\tB.\tPrior to the accumulation of 3,000 flight cycles after accomplishment of the initial inspection required by paragraph A. of this AD, accomplish the following: \n\n\t\t1.\tFor titanium T-ducts: Replace titanium T-ducts with Inconel T-ducts in accordance with Boeing Service Bulletin 747-36-2059, dated June 3, 1983. Accomplishment of this replacement constitutes terminating action for the requirements of this AD. \n\n\t\t2.\tFor flanged ducts, except T-ducts: Conduct a penetrant inspection, proof pressure test, and duct weld stress relieving in accordance with the Accomplishment Instructions, Items A. through K., of Boeing Alert Service Bulletin 747-36A2074, Revision 3, dated May 11, 1989, or Revision 4, dated September 13, 1990. If cracks or ruptures are detected, prior to further flight, repair or replace the duct in accordance with the service bulletin. If the duct weld stress relieving has already been accomplished in accordance with AD 88-17-07 prior to the effective date of this AD, it constitutes terminating action for the requirements of this paragraph for flanged ducts. \n\n\t\t3.\tFor flangeless ducts: Conduct a penetrant inspection, proof pressure test, and duct weld stress relieving in accordance with the Accomplishment Instructions, Items A. through K., of Boeing Alert Service Bulletin 747-36A2074, Revision 4, dated September 13, 1990. \n\n\tIf cracks or ruptures are detected, prior to further flight, repair or replace the duct in accordance with the service bulletin. If the penetrant inspection, proof pressure test, and duct weld stress relieving have already been accomplished in accordance with AD 88-17-07 prior to the effective date of this AD, the following apply: \n\n\t\t\ta.\tFor straight flangeless ducts (L3, R3, L4, R4, L5, and R5 defined in the service bulletin): The above constitutes terminating actions for the requirements of this AD. \n\n\t\t\tb.\tFor bent flangeless ducts (L2, R2, L7, and R7 defined in the service bulletin): Conduct only a proof pressure test in accordance with Boeing Alert Service Bulletin 747- 36A2074, Revision 4, dated September 13, 1990. \n\n\tC.\tFor ducts other than T-ducts: Replacement of all leading edge pneumatic ducts by kits in accordance with Boeing Alert Service Bulletin 747-36A2074, Revision 3, dated May 11, 1989, or Revision 4, dated September 13, 1990; or in accordance with Boeing Service Bulletin 747-36-2092, dated June 28, 1990; constitutes terminating action for the requirements of this AD. \n\n\tD.\tAn alternate means of compliance or adjustment of the compliance time, which provides an acceptable level of safety, may be used when approved by the Manager, Seattle Aircraft Certification Office (ACO), FAA, Transport Airplane Directorate. \n\n\tNOTE: The request should be submitted directly to the Manager, Seattle ACO, and a copy sent to the cognizant FAA Principal Inspector (PI). The PI will then forward comments or concurrence to the Seattle ACO. \n\n\tE.\tSpecial flight permits may be issued in accordance with FAR 21.197 and 21.199 to operate airplanes to a base inorder to comply with the requirements of this AD. \n\n\tAll persons affected by this directive who have not already received the appropriate service documents from the manufacturer may obtain copies upon request to Boeing Commercial Airplane Group, P.O. Box 3707, Seattle, Washington 98124. These documents may be examined at the FAA, Northwest Mountain Region, Transport Airplane Directorate, 1601 Lind Avenue SW., Renton, Washington. \n\n\tAirworthiness Directive 91-06-08 supersedes AD 88-17-07, Amendment 39-5986. \n\n\tThis amendment (39-6928, AD 91-06-08) becomes effective on April 15, 1991.