Block time, flight legs, duty limits, logbook decimals - cockpit-grade time math you can type in plain language.
Aviation runs on hours and minutes, but logbooks and payroll want decimals - and duty limits are strict enough that off-by-15-minutes matters. TCalc treats every leg as a real duration, so summing a multi-leg day or checking remaining duty time is one expression.
Type times the way they appear on your OFP. Add legs, subtract turnarounds, and flip the total to decimal hours for the logbook with one tap.
Almost every logbook dispute comes from mixing these up. Block time runs from the moment the aircraft first moves under its own power for the purpose of flight until it comes to rest at the end of the flight - off-blocks to on-blocks. Flight time in a fixed-wing logbook is conventionally recorded as that same block-to-block figure, which is why the two are often used interchangeably. Duty time is a different animal entirely: it starts when you report and ends when you are released, so it swallows briefing, the walk-around, turnarounds and post-flight paperwork.
The practical consequence is that a four-sector day with 5h 40m of block time can easily be a 12-hour duty. You need both figures, and you need them accurate, because one feeds your licence and currency requirements while the other feeds your flight-time-limitation checks.
Block time for a single sector, off-blocks 08:47 to on-blocks 13:05.
Total block time across a four-sector day.
Report at 06:15, released at 21:30 - the duty figure, not the block figure.
Flight time limitations are set by your operating rules and your operator's approved scheme - under EASA these live in ORO.FTL and are elaborated in the operator's OM-A, and the equivalent structures exist under other authorities. The maximum basic daily FDP for an acclimatised crew starts around 13 hours and is cut back as sector count rises and as the report time moves into the window of circadian low. Your operator's table is the authority; the arithmetic to apply it is what this calculator does.
The useful habit is to compute the projected end of your FDP the moment the roster changes, rather than discovering the problem at the gate. Add the planned FDP limit to your report time and you have the wall-clock moment past which you cannot start the final sector.
Report time plus a 13-hour basic FDP - the latest permissible end of duty before extensions.
Basic FDP reduced for sector count; check your operator's table for the exact reduction.
Margin left between projected FDP end and the scheduled on-blocks of the last sector.
Most electronic logbooks and many operators record flight time in decimal hours rather than hours and minutes, because decimal totals add without carrying. The conversion is simply minutes divided by sixty: 4h 18m is 4 + 18/60 = 4.3 hours. Going the other way, 0.7 hours is 42 minutes, not 70. Switching the output format does this without a second calculation.
The other recurring piece of arithmetic is the rolling limit. Flight time is typically capped over a rolling 28-day window and again over the calendar year, so the question is rarely "how much have I flown" but "how much have I flown in the last 28 days, and what does that leave". Subtracting your running total from the cap gives the honest answer before you agree to extra sectors.
Switch the output format to decimal hours for the logbook column.
Remaining flight time against a 100-hour rolling 28-day cap.
Remaining against an annual cap, useful when planning leave and line checks.
Block time: on-block minus off-block, minute borrow handled correctly.
Total flight time across three legs.
Logbook entry in decimal - one tap on the output format.
Landing time for a late departure - date rollover handled.
Subtract the off-block time from the on-block time: 13:05 − 08:47 = 4h 18m. TCalc does true base-60 subtraction, so the minute borrow that trips up mental math is handled for you.
Divide minutes by 60: 6h 45m is 6.75 hours. In TCalc, enter the duration and switch the output format to hours - every total displays as a decimal instantly.
Yes - chain them in one expression: 1h 20m + 45m + 2h 35m = 4h 40m. You can subtract turnarounds or duty already used in the same line.