Checklist: Check Ignition Switch & Key Integrity For Safety

Over time, worn surfaces on keys and internal switch components can mean switch positioning errors and unintended engine startups, the National Transportation Safety Board warns. 

Switches and associated keys, in fact, can become so worn that it becomes possible to remove the key from a switch position other than the OFF position.

A loss of ignition switch-to-key integrity can result in an ungrounded magneto, which could lead to an unintended engine startup during a hand movement of the propeller during pre-flight inspections leading to possible injury or death. 

What Should Pilots And Mechanics Do? 

The NTSB recommends: 

1. Always assume that a magneto is in an ungrounded condition and proceed with caution around any propeller.

2. Pilots should verify the integrity of the ignition switch-to-key connection to ensure the key can only be removed when the ignition switch is in the OFF position. If it can be removed otherwise, repair or replace the switch.

3. Mechanics should maintain vigilance when inspecting the ignition switch to key connection and repair or replace if needed.

4. Pilots and mechanics must be aware that an aging aircraft can be more susceptible to worn ignition switches. Additional vigilance may be necessary to detect and resolve the issue.