The log
Runs in your browser and saves the log in this browser only. Tap the button when the roll leaves and when it goes back.
How out-time adds up
The FAA Airframe Handbook (FAA-H-8083-31, Chapter 7) separates three lives. Storage life: the time allowed in the freezer, typically 6 months to a year. Mechanical life: the time allowed at room temperature before the material cures, “measured from the time the material is removed from the freezer until the time the material is returned to the freezer”. Handling life: the time to complete layup and compaction, shorter than the mechanical life.
Every period out counts toward the mechanical life, so the log adds them: used = sum of (back − out). What is left is the mechanical life minus that sum. The figure for your material and lot is on its data sheet; the calculator will not guess it.
The Handbook also warns that an auto-defrost freezer periodically warms its contents and “can reduce the shelf life and consume the allowable out-time”. Use a freezer that holds 0 °F or below without defrost cycles.
Worked example
A prepreg kit with a mechanical life of 240 h on its data sheet: out for 6 h on Monday, 3.5 h on Tuesday, and out again now for 2 h.
- Used = 6 + 3.5 + 2 = 11.5 h.
- Left = 240 − 11.5 = 228.5 h, 4.8 % used.
Plenty left on this kit. The same three periods on a material with a 10 h mechanical life would already be beyond it: discard.
Limits — when NOT to use this
- Not the quality record. Your repair station's procedures decide where the official out-time record is kept. This log lives only in this browser and is gone if site data is cleared.
- Room temperature assumed. Data sheets state the mechanical life at a temperature. A hot shop consumes it faster.
- One log per browser. Start a new log for each roll or kit.
Questions people actually ask
Does time thawing in a sealed bag count?
Yes. The Handbook measures mechanical life from removal from the freezer, and the material warms in the bag. Thawing in the sealed bag protects it from moisture, not from out-time.
Why is there no default life?
Because it differs by material and by lot, from days to weeks. A wrong default would be worse than none.
Sources
- FAA-H-8083-31, AMT Handbook — Airframe, Volume 1, Chapter 7, Storage of prepregs and adhesives — storage, mechanical and handling life; mechanical life from freezer removal to return; keep records; discard beyond the mechanical life; freezers at 0 °F or below, no auto-defrost.