Narrative:

Ferry flight [trans-pacific international]. Inbound flight delayed; so our outbound was also delayed; we ended up departing at xa:54 and airborne at xb:10; putting us directly into our window of circadian low (wocl). Captain was PF and I was pm; because of recent far 117 interpretations that required him to have a 2 hour break in the last half of the flight he was required to fly the first leg (when he would normally be asleep) and sleep the second leg (when he would normally be awake). I had planned to be PF for the leg and took a 2 hour nap from xr:00-xt:00; and felt well rested when I showed for the trip; but still found myself fighting fatigue during the leg; including micronaps; etc as did the captain. We then took our break during the second leg; but due to a malfunctioning crew bunk rest thermostat the bunk area was far too warm for effective rest; and after 3 hours of sleep I moved to an empty cabin seat; where I was able to get only another hour of sleep; since my body/mind was following its normal sleep/wake cycle and was awake. Captain also reported sleep issues after the rest period ended due to the warm bunk area; and amount of caffeine taken in to (try to) stay awake and alert during the first leg.during the descent/approach to landing numerous errors were made; with the captain declaring fatigue issues due to the revered sleep schedule. Landing was safely accomplished with the assistance of the two international relief officers (iros); who had been allowed to stay on their normal sleep schedule.

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Original NASA ASRS Text

Title: B787 FO reported fatigue on a trans-Pacific international route when FAR 117 dictated a rest schedule that was less than optimum for the flight crew's physiological needs.

Narrative: Ferry flight [trans-Pacific international]. Inbound flight delayed; so our outbound was also delayed; we ended up departing at xa:54 and airborne at XB:10; putting us directly into our Window of Circadian Low (WOCL). Captain was PF and I was PM; because of recent FAR 117 interpretations that required him to have a 2 hour break in the last half of the flight he was required to fly the first leg (when he would normally be asleep) and sleep the second leg (when he would normally be awake). I had planned to be PF for the leg and took a 2 hour nap from XR:00-XT:00; and felt well rested when I showed for the trip; but still found myself fighting fatigue during the leg; including micronaps; etc as did the Captain. We then took our break during the second leg; but due to a malfunctioning crew bunk rest thermostat the bunk area was far too warm for effective rest; and after 3 hours of sleep I moved to an empty cabin seat; where I was able to get only another hour of sleep; since my body/mind was following its normal sleep/wake cycle and was awake. Captain also reported sleep issues after the rest period ended due to the warm bunk area; and amount of caffeine taken in to (try to) stay awake and alert during the first leg.During the descent/approach to landing numerous errors were made; with the Captain declaring fatigue issues due to the revered sleep schedule. Landing was safely accomplished with the assistance of the two International Relief Officers (IROs); who had been allowed to stay on their normal sleep schedule.

Data retrieved from NASA's ASRS site and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.