EASA SIB NM-20-07: Boeing 747, 757, 767, 777, 787 Aeroplanes - Navigation - Glideslope System

What to do

Owners and operators of the affected Boeing 747, 757, 767, 777, and 787 airplanes are recommended to incorporate the Boeing Flight Crew Operations Manual Bulletin S489-50 procedures at the earliest opportunity. They should stay informed about forthcoming software updates and potential FAA rulemaking mandating their installation. For further technical information, stakeholders can contact the FAA aerospace engineer or Boeing Commercial Airplanes as provided.

Summary

The FAA Special Airworthiness Information Bulletin SAIB: NM-20-07 is an informational bulletin addressing potential erroneous autopilot flight director system (AFDS) guidance during instrument landing system (ILS) approaches on Boeing 747-400 and 747-8 series airplanes, Model 757, 767, 777, and 787-8, -9, and -10 airplanes. It highlights issues with misleading pitch guidance caused by glideslope signal interference during ILS approaches. This bulletin does not mandate any regulatory action but provides important operational information.

What changed

This bulletin introduces awareness of misleading AFDS pitch guidance during glideslope capture or tracking caused by ILS signal interference. Boeing has issued an operations manual bulletin with procedures to mitigate the issue, and Boeing along with its supplier is developing software updates to correct the problem. The FAA is considering future rulemaking to mandate installation of this software once it becomes available.

Why it matters

This information is critical for aviation professionals as misleading AFDS guidance can lead to dangerously steep or long approaches, increasing the risk of runway excursions or late touchdowns. Operators and flight crews need to understand the potential for glideslope signal interference and apply proper procedures to maintain safe approaches. Maintenance and compliance teams should monitor software updates and regulatory developments related to this issue.