84-20-08 GULFSTREAM AEROSPACE CORPORATION: Amendment 39-4927. Applies to Model G-159 airplanes certificated in all categories. Compliance required as indicated, unless already accomplished.
To detect and prevent corrosion or failure of the forward and aft engine mount assemblies, Vickers Drawing Number 81037, Sheet 29, and Gulfstream Aerospace Drawing Numbers 159W10432-1 (L/H) and 159W10432-3 (R/H), respectively, accomplish the following unless already accomplished:
(a) Within 200 hours time in service or four months after the effective date of this AD, whichever is sooner, inspect the forward and aft engine mounts, L/H and R/H, in accordance with Gulfstream I Customer Bulletin (CB) Number 241C, dated July 10, 1984, or in an equivalent manner approved by the Manager, Atlanta Aircraft Certification Office, FAA, Central Region.
(b) If corrosion is indicated:
(1) Replace corroded tubes in accordance with Customer Bulletin 241C before further flight, then revert to the inspections required under Category A, as stated in paragraph (d), below; or
(2) If continued flight is desired, ascertain the remaining wall thickness of the corroded tubes and categorize in accordance with Customer Bulletin No. 241C, and perform the operations for each category as indicated by paragraph (d), below.
(c) If corrosion is not indicated, perform the operations described in paragraph (d), below, for Category A.
(d) Category A - Reinspect as in paragraph (a) of this AD for corrosion at intervals not exceeding six years from last inspection.
Category B - Treat the tubes within 50 hours time in service in accordance with Addendum 1 or 4 of Customer Bulletin 241C and reinspect for corrosion as in paragraph (a) of this AD at annual intervals for at least two years after treatment. If there are no changes in the thickness measurements, reinspect at intervals not exceeding two years.
Categories C and D - Replace corroded tubes in accordancewith Customer Bulletin 241C within 150 hours time in service or three months, whichever is sooner; then revert to the inspections required under Category A.
Category E - Replace corroded tubes in accordance with Customer Bulletin 241C before further flight; then revert to inspections required under Category A.
(e) To prevent failure of Category B Gulfstream "Grumman mounts," replace the mounts prior to the accumulation of 7500 landings or within the next 25 landings, whichever occurs later within the following time period, in accordance with Gulfstream Aerospace Corporation Gulfstream I Customer Bulletin No. 241C, dated July 10, 1984, or equivalent manner approved by the Manager, Atlanta Aircraft Certification Office, FAA, Central Region:
(1) For airplanes that have accumulated 7500 landings prior to the effective date of this AD, within the next 25 landings after the effective date of this AD;
(2) For airplanes with less than 7500 landings on the effective date of this AD, within the next 25 landings after the accumulation of 7500 landings.
(f) To qualify for service beyond 7500 landings, Category A Gulfstream "Grumman mounts" must accomplish paragraph (g), below, within the following period:
(1) For airplanes that have accumulated 7500 landings prior to the effective date of this amendment, within the next 30 days or within 12 months of the last successful mount inspection in accordance with Gulfstream Aerospace Corporation Gulfstream I Customer Bulletin 289, Amendment 1, dated 26 May 1977, whichever occurs later, or
(2) For airplanes with less than 7500 landings on the effective date of this amendment, no later than the next 30 days after the accumulation of 7500 landings.
(g) Perform the ultrasonic and visual inspections in accordance with Gulfstream Aerospace Corporation Gulfstream I Inspection Schedule, Section V, Special Inspections, Engine Mounts, dated July 31, 1984, or in an equivalent manner approved by theManager, Atlanta Aircraft Certification Office, FAA, Central Region. If the inspections indicate negligible or no corrosion and no cracks, then the Grumman mount initially qualifies for the 20,000 landing life limit in accordance with Gulfstream Aerospace Corporation Gulfstream I Inspection Schedule, Section IV, Life Limited Components, dated July 31, 1984, and is no longer required to comply with the inspection requirements of paragraph (a) of this AD. Throughout this extended life limit, the inspections must be repeated at intervals not to exceed 12 months to maintain qualification for the 20,000 landing life limit. If, during such inspection, any mount subassemblies are found to have negligible or no internal corrosion and no cracks, those subassemblies may continue to be used if a detailed record of each life limited subassembly usage is maintained by the operator. If any inspection indicates the presence of unacceptable internal corrosion, replace the affected mount subassembly within the next 25 landings or 30 days, whichever occurs first. If a mount crack is found by any inspection, notify Gulfstream Aerospace Corporation, Technical Services Department, for dispositon before further flight. All life limited subassemblies that are not replaced during the repetitive inspections must be replaced by the end of the 20,000 landing life limit established by Gulfstream Aerospace Corporation Gulfstream I Inspection Schedule dated July 31, 1984.
All persons affected by this directive who have not already received these documents from the manufacturer may obtain copies upon request to Gulfstream Aerospace Corporation, P.O. Box 2206, Savannah, Georgia 31402. These documents also may be examined at the FAA, Northwest Mountain Region, 17900 Pacific Highway South, Seattle, Washington.
This supersedes Airworthiness Directive 74-03-01, Amendment 39-3667 (38 FR 23962).
This amendment becomes effective January 22, 1985.