FAA Special Airworthiness Information Bulletin NM-18-33: Engine Fuel and Control

https://drs.faa.gov/browse/excelExternalWindow/BBE820D0419DB3358625836600761396.0001

by Bengalilol • 1 year ago

1 2 1 year ago

drs.faa.gov

I keep seeing the word "disengaged" here. Isn't the locking tab an inherent feature of the switch, not something that can be engaged and disengaged? The wording of the bulletin implies that these locking tabs can wear or break off causing the switch to be just an ordinary toggle switch. But why beat around the bush and not just state that clearly?

Bengalilol• 1 year ago

After reading some articles, I became interested in understanding why no one was discussing this report in detail, even though it was being referenced as a document that had circulated. While reading it, I found myself wondering what I was supposed to take away from it and above all, how to determine whether the locking mechanism was actually malfunctioning.

You're absolutely right to question the wording. The term "disengaged" does create some ambiguity, especially since (as you noted) the locking tab is an integral part of the switch design, not something meant to be regularly engaged or disengaged like a mode or setting.

The bulletin indeed suggests that the locking tab can fail or be ineffective, but uses more cautious or indirect language (likely due to regulatory, legal, or technical communication norms?). That said, a clearer phrasing like “locking mechanism worn, broken, or missing” might have conveyed the issue more transparently.

So yes the core issue is a loss of the locking function, and you’re right that the wording could (and probably should) be more direct about it.

FAA Special Airworthiness Information Bulletin NM-18-33: Engine Fuel and Control

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