AD 52-27-02

52-27-02 DOUGLAS: Applies to Model DC-6 Aircraft (Fuselage Numbers 1 to 166, Inclusive).

Compliance required as indicated.

The following inspections and rework pertain to the outboard front spar splice plate, Douglas P/N 4325272 at Station 166 in the area of the inboard nacelle. This special inspection does not apply to splice plates that have been reworked by removing the aft attach tab or to new redesigned splice plates or when Douglas Service Bulletin 532 has been accomplished.

1. Inspection.

A. Conduct following inspection as soon as practical but not later than the next 50 hours operation unless already accomplished and continuing thereafter at intervals of regular inspection periods nearest to 500 flying hours from the time of initial inspection until the splice plate is replaced. Using at least an 8-power magnifying glass and/or dye check method or equivalent, make inspections for cracks in the chordwise direction in the area of the milled radius of the aft attach tab of the lower front spar splice plate. Alternate inspection procedures which will provide equivalent safety may be approved. If cracks are found, incorporate the rework of the item 2 before the next scheduled flight.

B. The above inspection must be continued periodically at intervals not to exceed 400 flying hours on all splice plates that have been reworked as per item 2A until the splice plate is replaced. If a crack is found beyond the stop drill hole prior to the replacement period as indicated in item 2C the splice plate must be replaced before the next scheduled flight.

2. Rework.

A. If cracks are found less than 1 3/8 inches long, stop drill using a 1/4-inch drill and ream with 17/64-inch reamer. The drill hole center must be located at a distance of 1 3/8 inches from the aft edge of the splice plate in line with the crack.

B. If cracks are found greater than 1 3/8 inches long, the splice plate must be replaced before the next flight.C. Splice plates reworked in accordance with item 2A must be replaced within 1,500 flying hours from time rework is accomplished.

(Douglas Service Letter No. 123, dated May 29, 1952, also covers this same subject.)