Flight Crew Air Transport Pilot (ATP)
Distraction; Fatigue; Workload
Deviation - Altitude Crossing Restriction Not Met; Deviation - Speed All Types; Deviation / Discrepancy - Procedural Clearance; Deviation / Discrepancy - Procedural Published Material / Policy; Deviation / Discrepancy - Procedural FAR
Flight Crew Became Reoriented
Human Factors; Company Policy
The event occurred on the second leg of the morning pairing at the end of six days of work. The week began with a night hub turn sequence followed by a 24 hour layover switching to day flying followed by a 24 hour layover switching back to a night hub turn sequence. Basically night hub turn to day hub turn to night hub turn all flown as the regularly scheduled bid pack line. The last pairing of the six day trip had a two leg sequence. The second leg was conducted in early morning day IMC conditions at a cruise altitude of 13;000 ft. Event #1: Did not comply with crossing restriction.ATC issued a clearance to cross 25nm this side of DQO at 9000 ft. Our current altitude was 13;000 ft. There were three fixes in our flight plan between our current fix and DQO spaced out by small mileages (10nm; 5nm; 7nm etc.). Since we were not cleared direct first I had trouble as the PM inputting the crossing restriction into the FMS because I had to do the math to determine which fix and which mileage to attach the restriction to. I definitely recognized some cognitive 'slowness' on my behalf due to fatigue that made it difficult to figure out where to attach the restriction. In the end we added up all the distances between us and DQO and determined we had time to make the descent and gave up on trying to program the FMS so we could use VNAV PATH. As we approached 10;000 ft in VNAV SPD with the speed window closed; the speed bug did not move from 325kts to 240kts automatically and we began to pass through 10;000 ft at 325 kts. The captain as the PF disengaged the autopilot to stop his descent below 10;000 ft above 250kts. He opened the speed window and selected 240kts. As the aircraft slowed he engaged FLCH 240 and re-commenced his descent to make the 9000 ft restriction at DQO. As the airspeed slowed he re-engaged VNAV and the speed bug cycled back up to 325kts; the thrust levers advanced and we reached about 270kts in a descent at approximately 9;500 ft. As the PM; I sensed the captain was overtasked and having trouble recognizing the problem so with one hand I opened the speed window and inserted 240kts and with the other hand I manually overrode the thrust levers and brought them to IDLE while the captain continued to hand fly the aircraft to attempt to maintain 10;000 ft while we slowed. Once the situation was stabilized the captain re-engaged the autopilot; allowed the aircraft to slow below 250kts and then finished the descent to 9000 ft. In the end we did not make the 9000 ft crossing restriction 25nm from DQO.Contributing factors were fatigue and the reduction in cognitive ability to solve a non-routine FMS drill; IMC conditions and steady precipitation; the low altitude/dense traffic area between [our departure airport] and PHL and the unexpected failure of the FMS to slow at 10;000 ft. For whatever reason; the VNAV side of the LEGS page listed .59M/9;000 at DQO instead of 240/9;000. The airplane wanted to maintain .59M below 10;000 ft instead of 240kts. The FMS VNAV DES page did not have the '240/10;000' speed rest like it normally does. I'm not sure why this was but feel it had something to do with our low cruise altitude of 13;000 ft. I'm not sure what could have been done as I would consider this the perfect storm of events. High density traffic environment; lots of low altitude fixes on a Victor Route; a non-routine crossing restriction; IMC and steady precipitation conditions; fatigue and unexpected auto-flight system behavior. We had multiple problems confront us at once. The rest of the flight was uneventful. The second half of a hub turn utilizing multiple legs in a high density environment is tough. The second leg of the pairing is usually when the morning flights of the passenger carriers are the busiest; it's at a low altitude where more low-flying slow speed aircraft are and it's at high density airports. Because of the IMC conditions between ZZZ-PHL we had a 30 minute ground delay after blackout further delaying our flight. This pairing is much different from [other] pairings where there isn't as much activity. It's all a part of the job; I understand but there is more operational risk with these types of pairings because of the time of day and location/operating environment. Fatigue was definitely at play as the week-long sequence had multiple shifts between day flying and night flying. While there was a 24 hour rest period between these shifts it can still be different to shift from a day sequence to a night sequence because it is hard to sleep normally at night and then try to take a nap in the middle of the day before your night sequence begins. It is challenging to have a two-leg pairing on a night hub turn immediately following a day to night switch like [this] pairing does.
B757-200 First Officer reported he and the Captain committed several errors on their flight because of fatigue and workload.