AD NUMBER: 2018-23-51

PRODUCT: All Boeing Model 737-8 and -9 airplanes.

ACTION: Final rule; request for comments.

SUMMARY: This emergency AD was sent previously to all known U.S. owners and operators of these airplanes. This AD requires revising certificate limitations and operating procedures of the airplane flight manual (AFM) to provide the flight crew with runaway horizontal stabilizer trim procedures to follow under certain conditions.

This AD was prompted by analysis performed by the manufacturer showing that if an erroneously high single angle of attack (AOA) sensor input is received by the flight control system, there is a potential for repeated nose-down trim commands of the horizontal stabilizer.

DATES: This AD is effective December 21, 2018 to all persons except those persons to whom it was made immediately effective by Emergency AD 2018-23-51, issued on November 7, 2018, which contained the requirements of this amendment. Comments must be received by January 22, 2019.

COST: The FAA estimates that this AD affects 45 airplanes of U.S. registry. Operators may incur the following costs in order to comply with this AD:
Revising the AFM - 1 work-hour × $85 per hour = $85

FMI: AD