AD 91-05-01

91-05-01 BOEING: Amendment 39-6904. Docket No. 90-NM-157-AD.

Applicability: All Model 757, 767, and 747-400 series airplanes, certificated in any category.

Compliance: Required within 30 days after the effective date of this AD, unless previously accomplished.

To prevent landing accidents as a result of inadvertent autopilot disconnection during restricted visibility conditions, accomplish the following:

A. Revise the Limitations Section of the FAA-approved Airplane Flight Manual (AFM) as follows. This may be accomplished by inserting a copy of this AD in the AFM.

1. For the Model 747-400 series airplane, add the following paragraph under AUTOPILOT/FLIGHT DIRECTOR SYSTEM: "For low weather minima automatic landing, fail-operational, the autopilot system has only been shown to meet the applicable airworthiness performance and integrity requirements to comply with FAA Advisory Circular (AC) 20-57A, and Appendix 1 and 2 of AC 120-28C, for an automatic landing system. (This supersedes information stated in NORMAL PROCEDURES)."

2. For the Model 767 series airplane, add the following paragraph under AUTOPILOT-FLIGHT DIRECTOR: "For autoland, fail-operational, the autopilot system has only been shown to meet the applicable airworthiness performance and integrity requirements to comply with Appendix 1 and 2 of FAA Advisory Circular 120-28C for an automatic landing system. (This supersedes information stated in NORMAL PROCEDURES)."

3. For the Model 757 series airplane, add the following paragraph under AUTOPILOT-FLIGHT DIRECTOR: "For autoland fail-operational, the autopilot system has only been shown to meet the applicable airworthiness performance and integrity requirements to comply with Appendix 1 and 2 of FAA Advisory Circular 120-28C for an automatic landing system. (This supersedes information stated in NORMAL PROCEDURES)."

B. For the Model 767 and 757 series airplanes, revise the Certificate Limitations Section ofthe FAA-approved AFM under AUTOPILOT - FLIGHT DIRECTOR to include the following. This may be accomplished by inserting a copy of this AD in the AFM. "For Autoland Operation, if the crewmember's status message changes from LAND 3 to LAND 2, an autoland is prohibited, and the pilot must disconnect the autopilot and execute a manual go-around or make a manual landing on that approach."

C. An alternate means of compliance which provides an acceptable level of safety, may be used when approved by the Manager, Seattle Aircraft Certification Office, FAA, Transport Airplane Directorate.

NOTE: The request should be submitted directly to the Manager, Seattle Aircraft Certification Office, and a copy sent to the cognizant FAA Principal Inspector (PI). The PI will then forward comments or concurrence to the Seattle Aircraft Certification Office.

D. 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 withthe requirements of this AD.

This amendment (39-6904, AD 91-05-01) becomes effective on March 5, 1991.