EASA SIB 2009-34: Boeing 737 Cabin Altitude Warning Confusion

What to do

Operators and training organizations should remind flight and cabin crews on all Boeing 737 model aeroplanes to don oxygen masks immediately upon hearing the intermittent warning horn or when passenger oxygen masks deploy. This procedure should be incorporated into operational manuals and training programs in accordance with EU-OPS Regulation OPS 1.210 (b). No specific compliance deadline is stated.

Summary

EASA Safety Information Bulletin SIB No: 2009-34 addresses confusion related to the cabin altitude warning horn on Boeing 737 model aeroplanes. The bulletin highlights incidents where flight crews misinterpreted the intermittent warning horn, which is used for both cabin altitude warnings and takeoff warnings, leading to inadequate responses and risk of hypoxia. It references the FAA Safety Alert for Operators SAFO No. 08016 and the Helios Airways Flight HCY522 accident report to emphasize the safety concern.

What changed

EASA SIB No: 2009-34 does not introduce new regulations but reinforces existing safety information by recommending that operators and training organizations remind flight and cabin crews of the critical need to don oxygen masks immediately when the intermittent warning horn sounds. It supports the FAA Airworthiness Directive 2006-13-13 and FAA SAFO No. 0816, emphasizing immediate crew response to cabin altitude warnings.

Why it matters

This bulletin is important for aviation professionals because misinterpretation of the cabin altitude warning horn can lead to crew hypoxia and loss of aircraft control, posing serious safety risks. Operators and training organizations must ensure crews are properly trained to recognize and respond promptly to these warnings to prevent accidents. Awareness and proper procedures reduce the risk of incapacitation due to slow or unnoticed cabin depressurization.

What to do

Summary

What changed

Why it matters

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