Mechanical interruption summary report

If you operate under Part 135 with multiengine aircraft, you must send a monthly summary report to your local Flight Standards office by the 10th day of each month covering the previous month's operations.

The report must include two types of events:

Mechanical interruptions: Any flight interruption, unscheduled aircraft swap, or unscheduled stop/diversion caused by known or suspected mechanical problems—but only those that don't already require reporting under §135.415 (which covers more serious mechanical failures).

Propeller featherings: The total number of times propellers were feathered in flight, broken down by propeller type, engine type, and aircraft. You don't need to count featherings done for training, demonstrations, or flight checks.

This regulation helps the FAA track mechanical reliability trends across Part 135 operations without requiring immediate reports for every minor mechanical issue. It's a summary report, not individual incident reports.

*This is a plain-English summary for study only. The official 14 CFR text on this page is controlling — always read the current regulation and consult a CFI.*