Life Limited Parts

by Wayne Darlington
(Port Alberni, BC Canada)

For aircraft parts such as a new propeller, a gearbox, or rotorhead, at what time does the clock start for the life limited components? Is it the time of installation, time of overhaul, time of purchase, or time of manufacture? What does the FAA state?

ANSWER: The FAA relies on the manufacturer to determine and publish the requirements. This is usually covered in the manufacturers maintenance and/or overhaul documents, or instructions for continued airworthiness.

FAR 43.13 requires all maintenance to be performed in accordance with the manufacturer’s instructions.

As a rule of thumb, it depends on what drives the life limit or overhaul period. For example:

- If the article's life limit were based on cycles (which most are), then the clock would start when cycles begin to accumulate on the article.

- If it were an overhaul period based on calender time, the clock would start from when the article was last overhauled.

- If it were based on hours, it would be when the article began accumulating hours.

- Some articles may have a shelf life associated with their storage, which would determine how long it could stay in stores before requiring further maintenance.