Understanding Split Rules
This article is written to help Overlord users creating or editing Duty Templates manage the new split time behaviour introduced in update 26.11.0. If you want more information about the update, you can read the Release Notes.
In HCM, split times can be used in various ways to credit additional time for duty and FDP limits calculated by our engine. In older versions of HCM, this was done globally - but now each template can have its own defined behavior based on your local regulations, operations manual and shift types.
What's a split?
A split is a break on the ground in the middle of a duty. On a duty template you enter the split itself, then two settings decide how much of that break is taken off the duty time and off the FDP when HCM and the FTL engine work out totals and legality.
Split values and controls
Split values can be entered on any individual duty record, which will inherit the default set by its duty template. The template itself will also contain settings for how the split is handled, which can be edited in the definition.
Entering the split values
-
Split before midnight: the whole split, for a duty that doesn't cross midnight. For a duty that does, the part of the split before midnight.
-
Split after midnight: the part of the split after midnight. Only available when the duty ends the next day.
Split off duty control
Whatever is taken off here doesn't count as duty. That lowers the duty length shown on the roster and the duty that counts towards the cumulative limits (for example 60 hours in 7 days or 200 hours in 28 days). For a duty that crosses midnight, the amount is shared between the two days in proportion to how much of the split falls on each.
Split off FDP control
Whatever is taken off here is removed from the FDP before it's checked against the maximum FDP. That has the same effect as extending the maximum FDP by that amount, which is how CAP 371 and EASA describe the split duty extension.
Control options
Any of these options can be set for each control independently:
- None: nothing is taken off. The split counts in full.
- Full split: the whole split is taken off.
- EASA: nothing for a split under 3 hours; half the split from 3 hours.
- CAP 371: nothing for a split under 2 hours; 1 hour for a split of 2 to 3 hours; half the split from 3 hours.
The limits include the boundary: a split of exactly 2:00 or 3:00 is in the higher band.
The split can't be longer than the duty, and each part can't be longer than the duty on its side of midnight: a duty that ends the same day has no split after midnight. A split over 10 hours is saved with a warning: CAP 371 gives no more credit above 10 hours, and a break that long is usually rest rather than a split.
A 10 hour duty, all of it FDP
Each cell shows how much is taken off, then what's left. The same option gives the same figures whether it's chosen for duty or for FDP.
| Split | None | Full split | EASA | CAP 371 |
|---|---|---|---|---|
| 1:30 | 0:00 → 10:00 | 1:30 → 8:30 | 0:00 → 10:00 | 0:00 → 10:00 |
| 2:30 | 0:00 → 10:00 | 2:30 → 7:30 | 0:00 → 10:00 | 1:00 → 9:00 |
| 4:00 | 0:00 → 10:00 | 4:00 → 6:00 | 2:00 → 8:00 | 2:00 → 8:00 |
For example, a 4:00 split with Split off duty on None and Split off FDP on CAP 371: the duty counts as 10:00, and the FDP is checked as 8:00.
Effect on rule calculations
This may have an effect on certain rules if you're using them in your rulesets - such as:
-
Duty length: the duty length shown on the roster and in reports, and the length checked against a maximum duty length rule, is the duty less the split off duty.
-
Cumulative duty (for example 60 hours in 7 days, 200 hours in 28 days, 2000 hours in a year): each day counts the duty worked that day, less the split off duty. For a duty that crosses midnight, the amount taken off is shared between the two days in proportion to how much of the split falls before and after midnight.
-
Maximum FDP: checked for each duty: the FDP less the split off FDP must be within the limit. This is the split duty extension.
-
Cumulative FDP (for example FDP hours in 28 days): each day counts the FDP worked that day, less the split off FDP, shared between the two days in the same way as for duty.
-
Rest: rules that need rest at least as long as the previous duty use the duty less the split off duty. Taking the split off duty shortens the rest needed afterwards.
A night duty in the cumulative duty totals
20:00 to 08:00 (12 hours), with a 4:00 split: 1:00 before midnight and 3:00 after.
| Split off duty | Taken off | First day (20:00–24:00) | Second day (00:00–08:00) | Total |
|---|---|---|---|---|
| None | 0:00 | 4:00 | 8:00 | 12:00 |
| Full split | 4:00 (1:00 + 3:00) | 3:00 | 5:00 | 8:00 |
| EASA or CAP 371 | 2:00 (0:30 + 1:30) | 3:30 | 6:30 | 10:00 |
The first day's figure counts towards limits that include that day, and the second day's towards limits that include the next. With nothing entered after midnight, the whole amount comes off the first day.
Configuring your controls
Based on your location, flying activity and operational setup - your use of these controls may differ, including examples like:
- CAP 371: duty None, FDP CAP 371. The split counts as duty and only extends the FDP.
- EASA FTL: duty None, FDP EASA.
- ENAC HEMS: duty None, FDP None. An interruption doesn't stop the duty, and there's no FDP extension.
- An approved scheme that deducts the break: duty Full split. Check that your approved scheme allows it.
Templates that existed before these settings were added start on duty Full split and FDP CAP 371, which is how splits were always counted. Settings on a template are copied to each duty when it's placed, and changing a template updates its future duties only.