AD 72-09-01

72-09-01 MCDONNELL DOUGLAS: Amendment 39-1436 as amended by Amendment 39-1636 is further amended by Amendment 39-2844. Applies to all Model DC-9 series airplanes listed in McDonnell Douglas Service Bulletin No. 54-27 dated March 3, 1972, or later FAA-approved revisions, and Military C-9A (DC-9-32F) airplanes.

Compliance required as indicated.

To prevent failures of the engine mount pylon as the result of cracks in the engine pylon upper aft spar caps (P/N 9958154-5, and -6) and/or the titanium straps (P/N 9958154-17 and -18) and supporting structure, accomplish the following:

A. For aircraft with more than 4000 hours time in service: Within the next 150 hours time in service after the effective date of this AD, unless already accomplished, conduct visual inspections for evidence of cracking, in accordance with the following procedure.

1. Visually inspect the upper and lower surfaces of the titanium straps, P/N 9958154-17 and -18, and the upper and lower surfaces of the steel spar caps, P/N 9958154-5 and -6, at the first, second and third fasteners inboard of the fuselage shell; and,

2. Visually inspect the aft face and lower surface of the titanium straps, P/N 9958154-17 and -18, and the lower surface of the steel spar caps, P/N 9958154-5 and -6, at the first, second and third fasteners outboard of the fuselage shell; and,

3. Visually inspect the bend radius and areas around the vertical line of rivets in the pylon rear spar supporting bulkhead shear clips, P/N 9912246-43 and -44, inside the fuselage shell between longerons 14 and 16; and,

4. Visually inspect the bend radius and areas around the horizontal line of rivets in the outboard leg of the intercostals, P/N 9915596-3 and -4, which attach to the fuselage skin between the pylon rear spar supporting bulkhead and next aft fuselage frame (P/N 5913596) inside the fuselage shell; and,

5. Visually inspect the bend radius and areas around the vertical line of rivetsin the outboard leg of the fuselage frame shear clips, (P/N 5913596-11 and -12, P/N 5913595-11 and -12), inside the fuselage shell, at the first and second fuselage frames (P/N's 5913596 and 5913595) aft of the rear spar support bulkhead.

6. If a crack is found:

a. In the pylon structure (other than the rear spar upper cap and/or strap) or adjacent fuselage structure, before further flight, replace the cracked parts with new parts of the same design, or repair in accordance with instructions prescribed in the Douglas DC-9 Structural Repair Manual, or repair in a manner approved by the Chief, Aircraft Engineering Division, FAA Western Region. After accomplishment of the above, perform the radiographic inspections specified in paragraph B.

b. In the spar cap(s), P/N 9958154-5 and/or -6, and/or strap(s), P/N 9958154-17 and/or -18, before further flight, replace the cracked parts with new parts of the same design; or, replace the cracked steel spar cap(s), P/N 9958154-5 and/or -6, with a new cap(s) of the same design, and replace the titanium strap(s), P/N 9958154-17 and/or -18, with a new design steel strap(s), P/N 5917717-3 and/or -4, using new larger diameter interference fit fasteners, in accordance with Douglas Service Bulletin S/B 54-27, dated 3 March 1972, or later FAA approved revisions; or, replace the spar cap(s), P/N 9958154-5 and/or -6 with a new spar cap(s), P/N 5917717-37 and/or -38 or 9958154-43 and/or -44 and replace the strap(s), P/N 9958154-17 and/or -18, with a new strap(s), P/N 5917717-39 and/or -40 in accordance with Douglas Service Bulletin 54-31 dated August 24, 1976 or later FAA approved revisions.

7. a. When a new spar cap or strap of the same (i.e. original) design is installed in accordance with the requirements in 6.b., accomplish the inspections specified in paragraph B until the existing (retained) part (cap or strap) is replaced with a new part in accordance with the requirements in 6.b., at which time the inspection requirements in paragraph 7.b. apply (Note: accumulation of 4000 hours time in service is based on earliest replaced part (cap or strap)); or

b. Upon installation of both a new spar cap and a new strap of the same (i.e. original) design, the inspections required in paragraphs A and B may be discontinued until these parts accumulate 4000 hours time in service, at which time reinstate the program of inspections and any necessary replacement or repairs per this AD; or,

c. Upon installation of new improved design steel strap(s), P/N 5917717-3 and/or -4, in conjunction with an existing (retained) uncracked steel spar cap(s) P/N 9958154-5 and/or -6, using new larger diameter interference fit fasteners, in accordance with Douglas S/B 54-27, or later FAA approved revision; or, new spar cap(s), P/N 5917717-37 and/or -38 or P/N 9958154-43 and/or -44 and a new strap(s), P/N 5917717-39 and/or -40 in accordance with the Douglas Service Bulletin 54-31 dated August 24, 1976 or later FAA approved revisions; the inspections required in paragraphs A and B of this AD are no longer applicable.

B. If no cracks are found after accomplishment of the inspections required by paragraph A-1 through A-5, or, after repair or replacement of parts as specified in 6(a), within the next 1200 hours time in service after the effective date of this AD and thereafter, at intervals not to exceed 1200 hours time in service from the last inspection, inspect the upper aft steel spar caps, P/N 9958154-5 and -6 and titanium cap straps, P/N 9958154-17 and -18, using radiographic inspection methods in accordance with the instructions outlined in Douglas All Operators Letter, AOL 9-666 dated November 22, 1971, (X-rays numbers 1, 1A, 2, 3, 7 and 8 are not required) or equivalent inspection means approved by the Chief, Aircraft Engineering Division, FAA Western Region; or, replace the titanium strap(s), P/N 9958154-17 and/or -18, with a new steel strap(s), P/N 5917717-3 and/or -4, using new larger diameter interference fit fasteners in accordance with the instructions specified in Douglas Service Bulletin 54-27, dated March 3, 1972, or later FAA approved revisions; or, replace the spar cap(s), P/N 9958154-5 and/or -6 with a new spar cap(s), P/N 5917717-37 and/or -38 or 9958154-43 and/or -44 and replace the strap(s), P/N 9958154-17 and/or -18, with a new strap(s), P/N 5917717-39 and/or -40 in accordance with Douglas Service Bulletin 54-31 dated August 24, 1976, or later FAA approved revisions. Upon accomplishment of the above rear spar upper cap and strap modifications specified in S/B 54-27 or S/B 54-31, the inspections required in Paragraphs A and B may be discontinued.

NOTE: Prior to installation of the new steel strap(s) P/N 5917717-3 and/or -4 per Service Bulletin 54-27, determine by radiographic inspection methods specified in Douglas AOL 9-666 or other FAA-approved equivalent inspection means (visual inspection is not considered satisfactory) that the existing (retained) steel cap is not cracked and shows no other signs of damage.

If cracks are found as a result of the radiographic inspections, before further flight, replace the cracked parts as specified in paragraph 6(b) and accomplish the inspections in accordance with the instructions in 7.a, 7.b and 7.c, as applicable.

Aircraft which have accumulated more than 1200 hours time in service as of the effective date of this amendment to AD 72-09-01, must be X-ray inspected within 150 hours time in service after the effective date of this amendment to AD 72-09-01, or the accumulation of 1500 hours total time in service, whichever occurs earlier.

Amendment 39-1436 supersedes Amendment 39-1418 (37 F.R. 6380), AD 72-07-06.

Amendment 39-1436 became effective April 25, 1972.

Amendment 39-1636 became effective May 14, 1973 for all persons except those to whom it was made effective by telegrams dated April 7, 1973 and April 21, 1973, which contained these amendments.This amendment 39-2844 becomes effective March 3, 1977.