AD 81-01-06

81-01-06 BENDIX AVIONICS: Amendment 39-4008. Applies to M-4 (A, B, C, D) Autopilot Primary Servo Models 3013E, 3013F, 3013G, 3013H, 3013J and 3013K and YD-4 Yaw Damper Primary Servos Models 3013J and 3013K having magnetic clutch, P/N 717503-0001, Serial Numbers 16750 through 18396, installed, repaired or overhauled after January 1, 1979, that do not contain Modification Number 4, as defined in Bendix Service Bulletin M-4D-060.

PRIMARY SERVO PRIMARY SERVO PRIMARY SERVO MODEL NUMBER PART NUMBER SERIAL NUMBER *3013E 1U014-01

*3013F 1U014-02

*3013G 1U014-03 Any primary servo that has had magnetic clutches installed after January 1, 1979. 3013H 4000523-8501 9530 through 9925 and any primary servo that has been repaired or overhauled after January 1, 1979 3013J 4009506-8501 1775 through 1792 and any primary servo that has been repaired or overhauled after January 1, 1979. 3013K 4009506-8502 2067 through 2110 and any primary servo that has been repaired or overhauled after January 1, 1979.

*Older model primary servos which may contain magnetic clutches manufactured by Bendix.

Compliance is required as indicated below unless already accomplished. To prevent the possible failure of the primary servo due to seizure of the magnetic clutches (P/N 717503-0001, Serial Numbers 16750 through 18396), accomplish the following:

Within the next 50 hours time in service after the effective date of this AD, inspect and modify the affected primary servos in accordance with Bendix Service Bulletin M-4D-060, dated November 1980 or in an equivalent manner approved by the Chief, Engineering and Manufacturing Branch, FAA Southern Region.

This amendment is effective January 12, 1981.