SAIB AIR-20-18

FAA Aviation Safety

SPECIAL AIRWORTHINESS

INFORMATION BULLETIN SUBJ: Flight Management Computing Software System SAIB: AIR-20-18 Date: November 16, 2020 This is information only. Recommendations aren’t mandatory.

Introduction

This Special Airworthiness Information Bulletin (SAIB) advises owners and operators of The Boeing Company Model 747-400 and 747-8 series airplanes equipped with flight management computer (FMC) software block point (BP) 4.0 of dual FMC failures/resets.

Background

Numerous reports have been received from operators of dual FMC resets on Model 747-400 and 747- 8 airplanes with the NGFMC BP 4.0 software update since introduction into the fleet. This can increase pilot workload when the flight crew is already in a high workload situation during approach operations. The NGFMC BP 4.0 software update was introduced as a means of compliance in related rulemaking in order to correct issues with FMC BP 3.1 software.

Multiple operators reported dual FMC BP 4.0 software failures/resets which occurred often in the approach phase of flight. These failures caused cold starts in both FMCs; an auto throttle disconnect;

an LNAV and VNAV mode failure; loss of performance initialization (PERF INIT) data, and the deactivation of the flight plan. This requires the crew to re-enter the PERF INIT data and reactivate the flight plan after the FMCs recovery.

Currently, Boeing and its supplier are investigating these anomalous FMC reset issues reported by 747 fleet operators that have upgraded to FMC software BP 4.0. The FAA anticipates additional rulemaking to address the issues with FMC software BP 3.1 and BP 4.0.

Recommendations

The FAA recommends that all owners and operators of the affected airplanes review the information in Boeing Fleet Team Digest 747-FTD-34-19008, and the interim action included therein, at the earliest opportunity.

For Further Information Contact

Hassan Ibrahim, Aerospace Engineer, Systems and Equipment Section, FAA, Seattle ACO Branch, 2200 South 216th St., Des Moines, WA 98198, at phone and fax: (206) 231-3653; email:

hassan.m.ibrahim@faa.gov

2 For Related Service Information Contact:

Boeing Commercial Airplanes, Attention: Contractual & Data Services (C&DS), 2600 Westminster Blvd., MC 110-SK57, Seal Beach, CA 90740-5600; telephone 562-797-1717;

https://www.myboeingfleet.com; or www.myboeingfleet.com/ReverseProxy/Authentication.html.