AD 86-14-01

86-14-01 SPERRY CORPORATION, AEROSPACE AND MARINE GROUP: Amendment 39-5340. Applies to Sperry Corporation AHZ-600 Attitude Heading Reference System (AHRS), known to be installed in, but not limited to, DeHavilland Model DHC-8, British Aerospace Model BAe 125-800, Cessna Model 650, and Aerospatiale Model ATR-42 series airplanes, certificated in any category. Compliance is required within 30 days after the effective date of this AD, unless previously accomplished.

To prevent loss of attitude/heading reference information, accomplish the following:

A. Modify the Sperry Corporation AH-600 Strapdown Attitude and Heading Reference Unit (AHRU) by incorporating modifications in accordance with the following Sperry Service Bulletins or later revisions approved by the Manager, Western Aircraft Certification Office, FAA, Northwest Mountain Region:

21-1985-175, dated April 7, 1986 (Modification T);

21-1985-186, dated April 7, 1986 (Modifications S & V);

21-1985-187,dated April 7, 1986 (Modification U);

21-1986-19, dated April 22, 1986 (Modification Z);

21-1986-20, dated April 22, 1986 (Modification AA); and

21-1986-29, dated April 22, 1986 (Modification AB).

B. Alternate means of compliance which provide an acceptable level of safety may be used when approved by the Manager, Western Aircraft Certification Office, FAA, Northwest Mountain Region.

C. Special flight permits may be issued in accordance with FAR 21.197 and 21.199 to operate airplanes to a base in order to comply with the requirements of this AD.

All persons affected by this directive who have not already received the appropriate service documents from the manufacturer may obtain copies upon request to Sperry Corporation, Aerospace & Marine Group, P.O. Box 29000, Phoenix, Arizona 85038-9000. These documents may be examined at the FAA, Northwest Mountain Region, 17900 Pacific Highway South, Seattle, Washington, or the Western Aircraft Certification Office,15000 Aviation Boulevard, Hawthorne, California.

This amendment becomes effective July 14, 1986.