AD 78-20-02

78-20-02 MCDONNELL DOUGLAS: Amendment 39-3306. Applies to DC-10-10, -10F, -30, -30F, and -40 airplanes certificated in all categories, incorporating Part No. SK12280-120, SK12280A120, SK12280-220, or SK12280A220, horizontal stabilizer drive chain with 6,000 or more hours' time in service on the chain.

Compliance required as indicated.

To prevent possible damage of the horizontal stabilizer attachment structure due to stabilizer drive chain failures accomplish the following:

(a) Within 90 hours' time in service after the effective date of this AD and thereafter at intervals not to exceed 90 hours' time in service, inspect to assure that each horizontal stabilizer drive chain is intact and completely engaged on the drive sprockets. If a chain is found disengaged from the sprocket or has noticeable damage, both this and the other chain on the same side must be replaced before further flight.

(b) Within the next 400 hours' time in service after the effective dateof this AD, unless accomplished within the last 800 hours' time in service, and thereafter at intervals not to exceed 1200 hours' time in service, inspect each horizontal stabilizer drive chain as follows:

(1) With hydraulic power applied, manually position the hydraulic control valve on the aft pressure bulkhead to actuate the chain in approximately 6 inch increments.

(2) Wipe the grease from the outer surface of the upper and lower side links.

(3) Visually inspect each and every side link outer surface for fracture or link damage. Special consideration should be given to the areas directly adjacent to the link pins. Move the horizontal stabilizer as required to continue the inspection sequence until a total inspection of each drive chain is assured.

(4) If any link is found cracked or visually damaged, that chain and the other chain of the same side must be replaced before further flight.

(5) Lubricate the drive chain on the completion of the inspection.

(c) Within the next 4,000 hours' time in service after the effective date of this AD, replace chain Part Nos. SK122080-120, SK12280A120, SK12280-220 or SK12280A220 with chain Part Nos. SK14869-120 or SK14869-220.

(d) Inspections per paragraphs (a) and (b) may be discontinued upon accomplishment of the chain replacement specified in paragraph (c).

(e) Equivalent inspections, modifications, or parts may be used when approved by the Chief, Aircraft Engineering Division, FAA Western Region.

(f) Special flight permits may be issued in accordance with FAR's 21.197 and 21.199 to operate airplanes to a base for accomplishment of the inspection or chain replacement required by this AD.

NOTE: McDonnell Douglas DC-10 Alert Service Bulletin A27-163 dated March 30, 1978, Service Bulletin 27-163 dated July 6, 1978 and Telex Alert Service Bulletin A27-163R1 dated August 1, 1978 cover this same subject.

This amendment becomes effective October 3, 1978.