Boeing 737 Aeroplanes - Flight Controls
- Published
AI-generated summary of the official EASA document. Verify against the PDF before acting.
What to do
Operators and maintenance technicians of the affected Boeing 737 models should follow the updated procedures in the Flight Crew Operations Manual and Aircraft Maintenance Manual for horizontal stabilizer positioning during de-icing. There are no mandatory compliance deadlines since this is an informational bulletin, but adherence is recommended to enhance safety.
Summary
The Special Airworthiness Information Bulletin SAIB: NM-16-21 is an FAA information bulletin addressing flight control procedures for Boeing 737-600, -700, -700C, -800, -900, and -900ER airplanes. It provides guidance on horizontal stabilizer position settings during de-icing to prevent elevator control issues. This bulletin is informational and does not mandate regulatory action.
What changed
SAIB NM-16-21 introduces procedural changes to the Boeing 737 Flight Crew Operations Manual and Aircraft Maintenance Manual regarding horizontal stabilizer positioning during de-icing. It recommends setting the horizontal stabilizer within the green band range or to five units of trim to reduce the risk of de-icing fluid freezing around the elevator power control unit input levers.
Why it matters
This bulletin is important because improper horizontal stabilizer positioning during de-icing can allow fluid to freeze and restrict elevator movement, potentially causing uncommanded pitch-up events. Following the updated procedures helps operators and maintenance personnel maintain flight control reliability and safety during cold weather operations.
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