Short-Call Reserve — the RAP and the 16-Hour Wall
Reserve day math is not "FDP starts at report". §117.21(c) measures from a clock that starts before you even have an assignment — and that is what actually caps your day.
First: which reserve are you on?
§117.21(a): "Unless specifically designated as airport/standby or short-call reserve by the certificate holder, all reserve is considered long-call reserve." The flavors behave completely differently:
| Type | Rule |
|---|
| Long-call | Notified to report after a full §117.25 rest period (§117.3 definition). No RAP clock. |
| Airport/standby | Must be designated as such (§117.21(b)); all time in status is FDP — the whole standby sits inside Table B, segments or not. |
| Short-call | Assigned a reserve availability period (RAP) — the rules below. |
The three short-call caps (§117.21(c))
- RAP ≤ 14 hours (§117.21(c)(1)). A reserve availability period is itself a duty period (§117.3) — it is duty, just not FDP.
- Rest between RAPs: after completing one RAP, the company cannot schedule — and you cannot accept — another RAP without the required §117.25(e) rest (10 h incl. 8 h uninterrupted sleep) in between (§117.21(c)(2)).
- The combined wall, unaugmented: total FDP + RAP, measured from the beginning of the RAP, may not exceed the lesser of Table B + 4 hours, or 16 hours (§117.21(c)(3)).
- The combined wall, augmented: FDP + RAP from RAP start may not exceed Table C + 4 hours (§117.21(c)(4)).
§117.19(a)(1) lets the PIC and company extend the combined limits of §117.21(c)(3)/(4) by up to 2 hours for unforeseen operational circumstances — the same +2 h, once-per-30-hour-break machinery as the FDP extension.
Worked example — where the wall bites
Short call starting 05:00, unaugmented, expecting a 2-segment trip. Table B at 0500/2 seg = 12 h, so the combined cap is min(12 + 4, 16) = 16 h from 05:00 → everything must be done by 21:00.
- Assignment to report at 09:00 → your FDP gets 16 − 4 = 12 h... but Table B itself caps that FDP at 12 h. Fine.
- Assignment to report at 13:00 → 16 − 8 = 8 h of FDP left, even though a lineholder reporting 13:00 would get 13 h. The RAP hours ate the FDP.
- Assignment at 17:30 → 16 − 12.5 = 3.5 h. Often better to decline and take the rest: §117.21(c)(2) makes the next RAP legally impossible without a full 10/8 rest anyway.
The rest of the reserve rulebook
- 12-hour WOCL notice (§117.21(d)): if a long-call assignment would begin before and operate into the window of circadian low (0200–0559), you must get 12 hours' notice of report time. See reserve status & the FDP window.
- Long-call → short-call shift (§117.21(e)): the company may flip your status mid-cycle only after giving you a full §117.25(e) rest first — "you're short call tomorrow" said today during your rest does not work.
- Cumulative interaction: only actual FDP counts toward §117.23(c) — RAP time is duty but not FDP — while §117.23(a) counts every hour of flying for anyone, reserve or not.
Compute your combined FDP + RAP wall in the calculator