Max FDP/Fatigue Calculator: EASA FTL and FAA Part 117

Three checks on one page. The fatigue risk check compares your recent sleep and the hours you will have been awake with the thresholds of the Prior Sleep/Wake Model. The EASA FDP calculator reads your maximum daily flight duty period from ORO.FTL.205, and the Part 117 calculator reads it from Table B of 14 CFR Part 117. Every figure is transcribed from its source, which is cited under each tool.

Fatigue risk check

Enter the sleep you actually got, counted back from the start of the duty, and the hours you will have been awake when the duty ends. The check tests the model's three thresholds.

Source: D. Dawson and K. McCulloch, “Managing fatigue: it’s about sleep”, Sleep Medicine Reviews, 2005: thresholds of under 5 h sleep in the prior 24 h, under 12 h in the prior 48 h, and hours awake at the end of work exceeding the sleep obtained in the prior 48 h. Alcohol comparison: D. Dawson and K. Reid, “Fatigue, alcohol and performance impairment”, Nature 388, 235 (1997). WOCL: ORO.FTL.105 and 14 CFR 117.3. The colours are this page’s summary of how many thresholds are crossed: green none, amber one, red two or three.

EASA maximum daily FDP

The basic maximum daily FDP for a flight or cabin crew member under the EU rules, from the start time at reference time and the number of sectors. It covers the tables for acclimatised crew and for crew in an unknown state of acclimatisation.

Source: Regulation (EU) No 965/2012, Annex III (Part-ORO), ORO.FTL.205(b)(1), Table 2, maximum daily FDP for acclimatised crew members, and ORO.FTL.205(b)(2), Table 3, crew members in an unknown state of acclimatisation (inserted by Regulation (EU) No 83/2014); reference time and WOCL defined in ORO.FTL.105. EASA Easy Access Rules for Air Operations. Not included: extensions without in-flight rest (ORO.FTL.205(d)), commander’s discretion (ORO.FTL.205(f)), in-flight rest for augmented crews, split duty, the higher table for unknown acclimatisation when the operator has FRM in place, standby, and any variation your authority has approved for your operator.

FAA Part 117 maximum FDP

The maximum flight duty period for a Part 117 flightcrew member in unaugmented operations, from the scheduled start in acclimated time and the number of flight segments.

Source: 14 CFR 117.13(a) and Table B to Part 117, “Flight Duty Period: Unaugmented Operations” (maximum flight duty period for lineholders); 117.13(b) for crew who are not acclimated (Table B reduced by 30 minutes, based on the local time at the theater in which the flightcrew member was last acclimated); flight time from 117.11 and Table A. 14 CFR Part 117 on eCFR. Not included: FDP extensions (117.19), augmented operations (117.17 and Table C), split duty, reserve assignments, and any FRMS approved under 117.7.

How to use the calculators

Start with the fatigue check, because the duty limits know nothing about how you slept. Enter the sleep you actually got, not the time you spent in bed, counted back from the start of the duty. Hours awake run from the moment you woke until the planned end of the duty, so include the commute and any delay you expect. Choose “yes” for the WOCL if any part of the duty falls between 02:00 and 05:59 on your body clock, which after a time-zone change may still be running on home time.

For the EASA calculator, enter the report time in reference time: the local time at the reporting point, when that point lies within the 2-hour-wide band around the local time to which you are acclimatised. If the acclimatisation table in ORO.FTL.105 puts you in an unknown state of acclimatisation, choose that option and the start time no longer matters. For Part 117, enter the scheduled start in acclimated time. If you are not acclimated, the tool takes 30 minutes off, and the start time to enter is the local time where you were last acclimated. Both results give the latest end of the FDP: when the aircraft must come to rest after the last sector (EASA) or be parked after the last segment (FAA).

What fatigue is

ICAO defines fatigue as a physiological state of reduced mental or physical performance capability resulting from sleep loss, extended wakefulness, circadian phase or workload, which can impair a crew member’s alertness and ability to perform safety-related duties. Two processes drive most of it. Sleep pressure builds with every hour awake and only sleep discharges it. The circadian rhythm is a roughly 24-hour cycle of alertness, lowest in the early morning with a smaller dip in the early afternoon.

Fatigue slows reactions, causes lapses and microsleeps, narrows attention and weakens memory and crew communication. Its most dangerous effect is on self-assessment: tired people consistently underrate how impaired they are. That is why the check above asks for hours rather than how you feel. The laboratory comparison with alcohol makes the same point: after 17 hours awake, performance on a tracking task fell to the level seen at a blood alcohol concentration of 0.05 %, and after 24 hours to about 0.10 % (Dawson and Reid, 1997).

The WOCL and sleep debt

The window of circadian low (WOCL) is 02:00 to 05:59 in the time zone to which you are acclimatised (ORO.FTL.105). The FAA uses the same hours in 117.3 and calls the WOCL a period of maximum sleepiness during a physiological night. Both FDP tables give shorter limits to duties that start at night or in the early morning for this reason. The model’s three thresholds ignore the time of day, which is why the check reports the WOCL separately: the same sleep and hours awake carry more risk at 04:00 than at 14:00.

Sleep debt is the running shortfall between the sleep you need and the sleep you get. It builds over consecutive short nights, even when you feel you have adapted, and only sleep repays it; after several restricted nights, one normal night is usually not enough. Daytime sleep after a night duty tends to be shorter and lighter, so a debt carried out of a night duty often grows. The 48-hour threshold in the check catches exactly this pattern, and it is the logic behind the recovery rest in the rules: 36 hours including two local nights under EASA, and 30 consecutive hours free from duty in any 168 hours under Part 117.

FRMS and fatigue reporting

Prescriptive limits cannot know how you slept. ICAO therefore also recognises the fatigue risk management system (FRMS): a data-driven means of continuously monitoring and managing fatigue-related safety risks, based on scientific principles and operational experience. An operator’s FRMS collects fatigue reports, compares planned with actual duties, may use sleep and alertness data or fatigue models, and changes rosters that do not work. In Europe fatigue risk management is covered by ORO.FTL.120 and is required in some cases, such as reduced rest; in the United States the FAA may approve an FRMS under 117.7.

All of it depends on reports. Filing one when a duty left you or a colleague impaired is not a complaint: it is safety data, handled under a just culture and, in Europe, under the occurrence reporting rules of Regulation (EU) No 376/2014. The figures in the fatigue check are the facts a useful report contains: sleep in the last 24 and 48 hours, hours awake, and the time of day.

The legal duty not to fly fatigued

Under 14 CFR 117.5 each flightcrew member must report for a flight duty period rested and prepared. No certificate holder may assign, and no flightcrew member may accept, an FDP when the pilot has reported too fatigued to perform it safely, and a pilot who reports too fatigued to continue may not be kept on duty. Each flightcrew member must also affirmatively state fitness for duty before the flight. Under the EU rules, ORO.FTL.115 requires crew members to make optimum use of their rest opportunities and, through the crew responsibilities in CAT.GEN.MPA.100, not to perform duties when they know or suspect they are fatigued to the extent that the flight may be endangered.

So the order of questions is always the same: am I fit, and only then, is the duty within the limits? A green result on this page answers neither for you. For the full rules, read flight time limitations, and for the physiology, pilot fatigue and sleep and circadian rhythms in the v1prep Library.

Frequently asked questions

What is the maximum flight duty period under EASA rules? For an acclimatised crew member, ORO.FTL.205(b)(1) allows 13:00 when the FDP starts between 06:00 and 13:29 with one or two sectors. Each sector from the third takes off 30 minutes, down to 9:00, and later starts have lower limits, reaching 11:00 for one or two sectors between 17:00 and 04:59. In an unknown state of acclimatisation the limit is 11:00 for one or two sectors, whatever the start time. Planned extensions, commander’s discretion and in-flight rest can change these figures under set conditions.

What is the maximum FDP under FAA Part 117? Table B to Part 117 sets 9 to 14 hours for an unaugmented crew, by the scheduled start in acclimated time and the number of flight segments. A start between 0700 and 1159 allows 14 hours for one or two segments, falling to 11.5 hours for seven or more; a start between 0000 and 0359 allows 9 hours for any number. A flightcrew member who is not acclimated has 30 minutes taken off the Table B limit (117.13(b)).

What is the Prior Sleep/Wake Model? A simple fatigue check proposed by Dawson and McCulloch in 2005. Before work, a person should have had at least 5 hours of sleep in the prior 24 hours and at least 12 hours in the prior 48 hours, and at the end of work should not have been awake for longer than the sleep obtained in the prior 48 hours. Crossing any threshold signals a higher likelihood of fatigue-related error and the need for a fatigue control.

Is being awake for 17 hours really like drinking alcohol? In a laboratory study published in Nature in 1997, Dawson and Reid found that after 17 hours of sustained wakefulness, performance on a tracking task fell to the level seen at a blood alcohol concentration of 0.05 %, and after 24 hours to about 0.10 %. It compares performance on one task and is not a legal equivalence, but both levels are above the alcohol limits for flight crew in Europe and the United States.

Can I use this calculator to decide whether I am fit to fly? No. It is educational. Your operator’s approved flight time limitation scheme, your roster and its FRMS govern your duties, and they include extensions, reductions and conditions that this page leaves out. Fitness for duty is your own judgement and a legal duty: if you are fatigued, do not operate, tell your operator and file a fatigue report.