70-01-04 GENERAL DYNAMICS: Amendment 39-917 is amended by Amendment 39- 943. Applies to Model 30 and 30A airplanes.
Compliance required as indicated.
To detect fatigue cracks and prevent possible failure of the main landing gear support beams:
a) Within the next 50 hours time in service after the effective date of this AD, or before the accumulation of 17,000 hours time in service, whichever occurs later, visually inspect the exposed surface of the upper beam cap from wing station 69 to 163 for cracks.
1) If no cracks are found, comply with either paragraph (b) or (c)(1) below.
2) If cracks are found in the exposed beam cap surface, remove the fasteners and conduct the inspection of the upper beam cap and tangs as described in paragraph (b), below. Prior to further flight, accomplish (c)(1) or (c)(2), as appropriate.
b) If no cracks are found as a result of the inspections specified in paragraph (a), within the next 250 hours time in service, remove the fasteners attaching the lower honeycomb wing panels to beam lower aft tang to permit internal access to the area from wing station 69 to 163, and inspect upper beam cap and tangs by means by dye penetrant or eddy current inspection procedure.
1) If no cracks are found, comply with one of the following alternatives:
i) Repeat the inspection described in paragraph (b) at intervals not to exceed 250 hours time in service, or;
ii) Install the beam cap reinforcement specified in paragraph (c)(1).
2) If cracks are found which are confined to the beam tang:
i) Within the next 50 hours' time in service, remove any steel tang reinforcement previously installed per General Dynamics Service Bulletin 57-9 and, unless previously accomplished, remove all evidence of cracking or any stop drilling by routing with a 0.50 radius router in accordance with Detail K on Convair Drawing Number 30-17827. Verify by dye penetrant or eddy current technique that all evidence ofcracking has been removed.
ii) Rework any newly detected tang cracks by routing as prescribed in (b)(2)(i).
iii) At intervals not to exceed 250 hours' time in service following any rework per (i) or (ii) above reinspect such reworked areas by eddy current or dye penetrant technique to determine whether any new cracking has developed. If sufficient tang material remains, any new cracking which is detected may be routed out per (i), above. If cracking has progressed into spar cap, rework per (b)(3) below.
iv) The reinspection of any spar tang which has been reworked so as to remove all indication of cracking may be discontinued when the spar cap is reinforced per (c)(1) below.
3) If cracks are found in the beam cap and any such crack does not exceed a total area of 0.50 square inches or does not extend chordwise along the upper surface of the beam cap for more than 0.75 inches:
i) Remove all evidence of cracking by routing with a router having a minimumradius of 0.50 inches. The cross sectional area removed by routing must not exceed 0.50 square inches. Break all sharp corners and polish all routed surfaces and confirm by eddy current or dye penetrant technique that no evidence of cracking remains.
ii) At intervals not to exceed 50 hours' time in service, reinspect all beam caps which have been reworked per (b)(3)(i), above, using dye penetrant or eddy current technique to determine that no new cracking has developed.
iii) The reinspection program required by paragraphs (b)(3)(ii) may be discontinued when the beam cap reinforcement is installed per (c)(1) below:
4) If cracks are found in the beam cap extending beyond the limitations specified in (b)(3) above, the beam must be replaced with a new beam prior to further flight.
c) Accomplish the following if applicable:
1) If there are no cracks, or if cracks are confined to the beam tangs or extend into the beam cap to any depth less than 0.75 inch, provided that the total cross sectional area loss due to cracking is within the limits specified in General Dynamics Service Engineering Report No. 057-0/67-990-44A, accomplish the repair and reinforcement provisions of paragraph (2)(c) of General Dynamics Service Bulletin 57-9, dated 22 September 1969, or later FAA approved revision, or an equivalent repair and reinforcement approved by the Chief, Aircraft Engineering Division, FAA Western Region. The installation of machine tapered straps on the MLG beam flanges described in General Dynamics Service Bulletin No. 57-3, dated 21 September 1962, or later FAA approved revision, or an equivalent approved installation must be accomplished prior to or concurrently with the rework of S.B. 5709. The repetitive inspections outlined in paragraph (b) may be discontinued following the above repair and reinforcement.
2) If the cracks extend into the beam cap to any depth greater than 0.75 inches, or if the total cross sectional area loss due tocracking exceeds the limits specified in General Dynamics Service Engineering Report No. 057-0/67-990-44A, the beam must be replaced with a new beam before further flight. The following conditions are also applicable:
i) If the rework and reinforcement outlined in paragraph (c)(1) are not accomplished on the new beam, perform inspections at the intervals specified in paragraph (b) of this AD prior to the accumulation of 17,000 hours time in service after installation of the new beam.
ii) If the rework and reinforcement of paragraph (c)(1) has been accomplished on the new beam, all inspections mentioned above may be discontinued.
The inspection required by this AD may be discontinued for any uncracked landing gear support beam or for any support beam which has been reworked as prescribed above when the beam is reinforced in accordance with paragraph (2)(c) of General Dynamics Service Bulletin 57- 9, dated September 22, 1969, or later FAA approved revision, or an equivalent reinforcement approved by the Chief, Aircraft Engineering Division, FAA Western Region. The installation of machine tapered straps on the MLG beam flanges described in General Dynamics Service Bulletin 57-3, dated September 21, 1962, or later FAA approved revision, or an equivalent approved installation must be accomplished prior to or concurrently with the rework of Service Bulletin 57-9.
A further amendment of this AD will be accomplished at such time as new service bulletin information is issued by the manufacturer or any additional requirements or clarifications are found necessary.
Amendment 39-917 effective January 29, 1970.
This amendment is effective February 26, 1970, and was effective upon receipt for all recipients of the telegram dated January 30, 1970, which contained this amendment.