A number of recent helicopter accident reviews have identified improper maintenance as a contributing factor, according to FAA’s Alert Notice NOTC4455 issued November 21. Mistakes include items seemingly as simple as improper torque settings, failure to install cotter safety pins and reuse of damaged self-locking nuts.

The FAA said the reasons for these problems appear to focus on human factors and failure to follow written procedures. Fatigue, time constraints to perform the maintenance tasks, cell phone activity and complacency were all factors in the accidents concerned, according to the FAA.