MEL rectification interval calculator
Work out the due date for a deferred defect under MEL categories A, B, C and D. Free, private and nothing to install.
For guidance only. Your operator's MEL and its preamble define the applicable intervals, how they are counted and any extension procedures.
How MEL categories work
| Category | Rectification interval |
|---|---|
| A | As specified in the remarks of the MEL item (e.g. a number of days, flight hours or cycles) |
| B | 3 consecutive calendar days |
| C | 10 consecutive calendar days |
| D | 120 consecutive calendar days |
The calculator adds the interval to the date the defect was found. For example, a Category C item found on 1 October is due by 11 October.
The same calculator is built into the Experience Logbook app, alongside an airport reference and an aircraft type list, and you can log the deferral as an MEL task in your experience logbook in the same minute.
MEL calculator FAQ
What are MEL categories A, B, C and D?
MEL items are given a rectification interval category. Category B items must be rectified within 3 consecutive calendar days, Category C within 10 and Category D within 120. Category A has no standard interval: the time limit is stated in the remarks of the MEL item itself.
Is the day the defect was found counted?
Commonly the interval is counted in calendar days excluding the day of discovery, which is how this calculator works: it adds the number of days to the start date. Your operator's MEL preamble is the authority on how intervals are counted and when exactly they expire.
Can the rectification interval be extended?
Some authorities allow a one-time Rectification Interval Extension (RIE) for categories B, C and D under strict conditions defined in the operator's procedures. Category A items generally cannot be extended. Check your operator's MEL procedures.