Blades on your ceiling fan should not fly off like a pair of dull machetes

Because I used to do failure analysis I occasionally look at the product recalls web page for the Consumer Product Safety Commission (CPSC). On February 13, 2020 there was one titled Fanim Industries recalls Harbor Breeze Santa Anna ceiling fan due to injury hazard: sold exclusively at Lowes stores. They said blade holders on the fan can break and either of the two blades can fly off. 70,000 fans are being recalled because there were 210 reports of blades ejecting or breaking and 10 reports of blades hitting customers.

The installation guide shows that each blade holder arm (red) is attached to the motor flywheel via two screws. Initial assembly instructions warn you to make sure the bottom edge of the blade holder arm is fully seated against the flywheel surface of the motor. Then final assembly instructions say each blade (yellow) is attached to a blade holder via three washer-head screws.

Those screws normally should not loosen. On May 6, 2018 I blogged about how Driverless cars don’t need steering wheels – but the rest of us sure do. That recall was because a locking feature had been improperly applied. An article from 2015 by Michael Kaas at Fastening + Fixing Magazine titled Stop loosening of fasteners shows several options. A more detailed discussion is found in NASA STD 5020 Requirements for threaded fastening systems in spaceflight hardware. See Appendix B, best practices for locking features.