58-01-05 LOCKHEED: Applies to All Models 49-46, 149, 649, 649A, 749, 749A, and 1049-54 Aircraft.
Compliance required as indicated.
As a result of cracks discovered in Lockheed 749A wing skin and stringers, the following inspections shall be accomplished on the various model aircraft as indicated, and if any cracks are discovered, they must be repaired prior to further operation. Any FAA/LAC approved repair may be used.
Inspect and reinspect for cracks in the lower wing skin and stringers, left and right, from wing Station 125 through Station 215 between the front and rear beams. Inspections to be conducted at the following specified times and intervals using X-ray and visual, or visual means. The X-ray inspection method is recommended if equipment is available, since cracks under the stringers would be detected.
I. For Models 649, 649A, 749, 749A and 1049-54:
A. The first inspection should be performed before 20,500 hours have been accumulated on the aircraft. For aircraft on which inspections of STA 191 through 206 have already been made in accordance with AD 56-03-01, initial inspections of additional indicated areas need not be earlier than and may be correlated with reinspections required by B(1), B(2), B(3), and B(4).
B. Reinspections must be accomplished in accordance with one of the following programs:
(1) X-ray at 2,500 hours (maximum) intervals without opening the fuel tanks following the recommendations and technique outlined on Lockheed Sketch No. 101057 or a FAA/LAC approved equivalent. In addition to the X-ray inspection at this time, the bottom side of the wing skin must be visually inspected from front to rear beam beneath the nacelle to wing fillets on the inboard and outboard sides of No. 2 and No. 3 nacelles. This necessitates opening the kidney plate inspection holes in these fillets and/or removal of the tail cone assembly. See Lockheed Sketch No. 101057 for location of cracks which have previously been discovered; or
(2) X-ray at 3,200 hours (maximum) intervals by opening the fuel tanks and following the technique outlined on Lockheed Sketches No. 101057 and No. 101058, or FAA/LAC approved equivalent. In addition to the X-ray inspections at 3,200 hours, aircraft with over 20,000 hours must be visually inspected at 200-hour (maximum) intervals as follows:
Inspect the bottom side of lower wing skin, for leaks resulting from cracks, from front beam to rear beam between W.S. 125 and W.S. 145 and between W.S. 191 and W.S. 215. This necessitates opening the kidney plate inspection holes in the nacelle to wing fillets on the inboard and outboard sides and/or removal of the tail cone assembly of nacelles No. 2 and No. 3. This area should be given special attention. If leaks are discovered and cracks suspected, tanks must be opened and stripped of sealant to visually inspect upper side of skin. Inspect the upper side of lower wing skin for cracks in the dry area from front beam to rear beam between W.S. 145 and W.S. 191. See Lockheed Sketches No. 101057 and No. 101058 for location of cracks which have been previously discovered; or
(3) When X-ray equipment is not available, a visual inspection must be made at 800-hour (maximum) intervals after opening the fuel tanks and removing the sealant from the designated areas. (It should be noted that cracks under stringers cannot be detected by the visual inspection method); or
(4) X-ray at 2,800 hours (maximum) intervals by opening the fuel tanks and following the technique outlined on Lockheed Sketches No. 101057 and No. 101058, or FAA approved equivalent. In addition to the X-ray inspections at 2,800 hours, visually inspect at 350-hour (maximum) intervals as follows:
Inspect the bottom side of lower wing skin, for leaks resulting from cracks, from front beam to rear beam between W.S. 125 and W.S. 145 and between W.S. 191 and W.S. 215. This necessitates opening the kidney plate inspection holes in the nacelle to wing fillets on the inboard and outboard sides and/or removal of the tail cone assembly of nacelles No. 2 and No. 3. This area should be given special attention. If leaks are discovered and cracks suspected, tanks must be opened and stripped of sealant to visually inspect upper side of skin. Inspect the upper side of lower wing skin for cracks in the dry area from front beam to rear beam between W.S. 145 and W.S. 191. See Lockheed Sketches No. 101057 and No. 101058 for location of cracks which have been discovered previously.
C. The reinspections required as per paragraphs B(1), B(2), B(3), or B(4) may be discontinued when permanent reinforcement per Lockheed Drawing No. 550236 has been accomplished, except that:
In the area from W.S. 125 to W.S. 191 where the size and kind of material remains unchanged (i.e., the old material is merely replaced with new) the reinspection program noted above must be reinstated not later than 20,000 hours after rework.
D. Lockheed Drawing Nos. 11755, 490668, 492806, and 493312, describe approved permanent repairs for individually affected areas in which cracks have been previously discovered. Reinspections in the area between W.S. 191 and W.S. 215 may be discontinued if permanent repair is made per Lockheed Drawing No. 11755. The reinspection program must be reinstated not later than 20,000 hours after rework is accomplished in the individually affected areas per drawing numbers 490668, 492806, or 493312.
E. Upon request of the operator, an FAA maintenance inspector, subject to prior approval of the Chief, Engineering and Manufacturing Branch, 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.
II. For Models 49-46 and 149:
A. The first inspection should be performed before 25,500 hours have been accumulated on the aircraft. For aircraft on which inspections of STA 191 through 206 have already been made in accordance with AD 56-03-01, initial inspections of additional indicated areas need not be earlier than and may be correlated with reinspection required by B(1), B(2), B(3), and B(4).
B. Same as paragraph I.B.
1. Same as paragraph I.B.(1).
2. Same as paragraph I.B.(2) (except substituted 25,000 hours for 20,000 hours).
3. Same as paragraph I.B.(3).
4. Same as paragraph I.B.(4).
C. The reinspections required as per paragraphs B(1), B(2), B(3), or B(4) may be discontinued when permanent reinforcement per Lockheed Drawing No. 550236 has been accomplished, except that:
In the area from W.S. 125 to W.S. 191 where the size and kind of material remains unchanged (i.e., the old material is merely replaced with new) the reinspection program noted above must be reinstated not later than 25,000 hours after rework.
D. Lockheed Dwg. Nos. 11755, 490191, 490668, 492806, and 493312 describe approved permanent repairs for individually affected areas in which cracks have been previously discovered. Reinspections in the area between W.S. 191 and W.S. 215 may be discontinued if permanent repair is made per Lockheed Drawing No. 11755 or 490191. The reinspection program must be reinstated not later than 25,000 hours after rework is accomplished in the individually affected areas per drawing Nos. 490668, 492806, or 493312.
E. Upon request of the operator, an FAA maintenance inspector, subject to prior approval of the Chief, Engineering and Manufacturing Branch, 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 supersedes AD 56-03-01.
Revised September 26, 1963.