AD 79-05-01

79-05-01 MCDONNELL DOUGLAS: Amendment 39-3421. Applies to DC-10-10, -10F, -30, -30F and -40 series airplanes certificated in all categories.

Compliance is required as indicated.

To reduce the probability of an autopilot "land" mode failure that could cause automatic landing system performance outside the certification limits, accomplish the following, unless already accomplished:

a. Within the next 100 hours' time in service from the effective date of this AD, on airplanes with 33,000 or more hours time in service on wire bundles serviced by receptacles R5/P1-226, R5/P1-267, R5/P1-281 or R5/P1-282:

1. Deactivate the autopilot "land" mode in accordance with paragraph (d) of this AD; or

2. Replace wire bundles with like serviceable parts and comply with the inspection schedule of paragraph (b) of this AD; or

3. Replace wire bundles per McDonnell Douglas DC-10 Service Bulletin 24-99, dated September 29, 1978. This option terminates the need for further testing as required by this AD.

NOTE: Service Bulletin A24-99, dated June 19, 1978, or Service Bulletin 24-99, dated September 29, 1978, are the only versions of the service bulletins suitable for compliance with paragraphs (a) and (b) of this AD.

b. Within the total time in service on the wire bundles identified in paragraph (a) and as specified in the following table:

Total Hours' Time in Service On Wire Bundles Initial Testing Repetitive Testing

10,000-12,999 Within 3,000 additional hours' time in service after the effective date of this AD 3,000 hours' time in service intervals except DC-10-40 airplanes may use 5,000 hours' time in service intervals

13,000-14,999 Prior to accumulation of 16,000 hours' time in service 3,000 hours' time in service intervals except DC-10-40 airplanes may use 5,000 hours' time in service intervals

15,000-24,999 Within 1,000 additional hours' time in service after the effective date of this AD 3,000 hours' time in service intervals except DC-10-40 airplanes may use 5,000 hours' time in service intervals

25,000-33,000 Within 1,000 additional hours' time in service after the effective date of this AD 1,000 hours' time in service intervals except DC-10-40 airplanes may use 2,000 hours' time in service intervals

1. Perform the initial and repetitive tests indicated in paragraph 2 of McDonnell Douglas Alert Service Bulletin A24-99, dated June 19, 1978; or

2. Deactivate the autopilot "land" mode in accordance with paragraph (d) of this AD; or

3. Replace wire bundles per paragraph 2 of Service Bulletin 24-99, dated September 29, 1978. This option terminates the need for further testing as defined in this AD.

c. If wire-to-wire faults are found during the testing of (b)(1), before further flight:

1. Deactivate the autopilot "land" mode in accordance with paragraph (d) of this AD; or

2. Replace wire bundles with like serviceable parts and comply with the inspection schedule of paragraph (b) of this AD; or

3. Replace wire bundles per paragraph 2 of Service Bulletin 24-99, dated September 29, 1978. This option terminates the need for further testing as defined in this AD.

d. Deactivation of the autopilot "land" mode shall be accomplished as follows:

1. Coil and stow wires 1C512B24 and 2C512B24 or 1C512M24 and 2C512M24 as applicable.

2. Placard the autopilot "land" mode inoperative.

e. For airplanes with the autopilot "land" mode deactivated for reasons other than those defined in this AD for a period in excess of the initial testing period defined in paragraph (b) that have wire bundles subject to testing as defined in this AD must be tested prior to reactivation as defined in paragraph (b).

f. Upon request of an operator, the FAA assigned inspector, subject to prior approval of the Chief, Aircraft Engineering Division, FAA Western Region, may adjust the initial and repetitive tests at 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 that operator.

g. Equivalent test procedures or modifications may be used when approved by the Chief, Aircraft Engineering Division, FAA Western Region.

h. Special flight permits may be issued in accordance with FAR's 21.197 and 21.199 to authorize operation of aircraft to a base where the modification required by this AD may be performed.

This amendment becomes effective March 23, 1979.