Narrative:

I removed my headset to stretch; yawn; etc; then the first officer took a physiological break and I put the O2 mask on; but neglected to turn up the overhead speaker. When the first officer returned to the cockpit he neglected to put his headset on and when I removed the O2 mask I also did not turn on my overhead speaker nor put on my headset. During a period of about 10-15 minutes neither of us had a headset on or the overhead speakers at a listening level. We received an ACARS air-air message that ATC wanted to talk with us. They had tried several times to reach us on the radio and finally asked a company aircraft to message us which they did. We re-established radio comm with ATC and they did not appear concerned. We were both very tired and sleepy and had been drinking coffee in attempt to stay focused but the fatigue issue made us a bit sloppy with our attention to communication procedures. The overhead HUD projector has interfered with my use of the speaker in the past so I have got into the habit of just wearing my headset all of the time. I broke a habit pattern due to lack of sleep; but I will not do it again. Always ensure the speaker column is up when the mask is on and check it again after any crew change or when a crew member has taken a break. Always keep some column on even if wearing the headset. A normal flaps 35 ILS approach and landing was briefed for arrival. Weather was overcast with 10 miles visibility. I elected to use the HUD for my own training proficiency. After configuring the aircraft with the gear down and flaps at 28 deg; I disconnected the autopilot with the runways in sight on approach but we had a speed restriction of 170 knots to the FAF on 16C. I had configured early knowing that I was tired and wanted to have safe methodical and well stabilized approach. Coming down final; on one of my airspeed crosschecks the airspeed did not seem correct; but I could not identify what was wrong with it as I was just above the amber foot and the autothrottles were working efficiently; but I did have my hand on them 'in case.' the HUD projection was working well and I was established on localizer and glide slope and the runway clearly visible in front of me. The pm called stable at 500 ft; but failed to notice 'no green box' and shortly after we received the GPWS 'to low flaps' warning. I knew immediately that I had failed to call for flaps 35. My evaluation of terrain; runway; and the airplane determined a call to set the flaps at 35; which we did; and I made an uneventful landing. The pitch forces and trim changes from 28-35 are minuscule thus the landing was well within acceptable parameters. I should have gone around at the GPWS call. I think my fatigue was the biggest factor and that is the fatigue of back side of the clock flying. I had plenty of rest previous nights; but just not enough prior to this flight with a show after night. I woke up at midnight and drove to work after getting about 3 hrs rest. I should have vocalized my earlier concern to the first officer about my concern that something didn't seem right when on final. And I should have gone around. We clearly did not have a green box on final and I always check that but did not this time for some reason. I will always check it in the future regardless. When using the HUD you must move your head a bit to see the display and the green box symbology. I did not and should have gone around. Train our pilots to recognize fatigue signs during critical phases of flight. Train our pilots ensure a 'green box' prior to the stable call. I should have gone around.

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Original NASA ASRS Text

Title: A Cargo flight crew described fatigue induced communication and procedural errors during flight after their inability to sleep during the previous daylight rest cycle.

Narrative: I removed my headset to stretch; yawn; etc; then the First Officer took a physiological break and I put the O2 mask on; but neglected to turn up the overhead speaker. When the First Officer returned to the cockpit he neglected to put his headset on and when I removed the O2 mask I also did not turn on my overhead speaker nor put on my headset. During a period of about 10-15 minutes neither of us had a headset on or the overhead speakers at a listening level. We received an ACARS Air-Air message that ATC wanted to talk with us. They had tried several times to reach us on the radio and finally asked a Company aircraft to message us which they did. We re-established radio comm with ATC and they did not appear concerned. We were both very tired and sleepy and had been drinking coffee in attempt to stay focused but the fatigue issue made us a bit sloppy with our attention to communication procedures. The overhead HUD projector has interfered with my use of the speaker in the past so I have got into the habit of just wearing my headset all of the time. I broke a habit pattern due to lack of sleep; but I will not do it again. Always ensure the speaker column is up when the mask is on and check it again after any crew change or when a crew member has taken a break. Always keep some column on even if wearing the headset. A normal Flaps 35 ILS approach and landing was briefed for arrival. Weather was overcast with 10 miles visibility. I elected to use the HUD for my own training proficiency. After configuring the aircraft with the gear down and flaps at 28 deg; I disconnected the autopilot with the runways in sight on approach but we had a speed restriction of 170 knots to the FAF on 16C. I had configured early knowing that I was tired and wanted to have safe methodical and well stabilized approach. Coming down final; on one of my airspeed crosschecks the airspeed did not seem correct; but I could not identify what was wrong with it as I was just above the amber foot and the autothrottles were working efficiently; but I did have my hand on them 'in case.' The HUD projection was working well and I was established on LOC and Glide Slope and the runway clearly visible in front of me. The PM called stable at 500 FT; but failed to notice 'no green box' and shortly after we received the GPWS 'To low Flaps' warning. I knew immediately that I had failed to call for flaps 35. My evaluation of terrain; runway; and the airplane determined a call to set the flaps at 35; which we did; and I made an uneventful landing. The pitch forces and trim changes from 28-35 are minuscule thus the landing was well within acceptable parameters. I should have gone around at the GPWS call. I think my fatigue was the biggest factor and that is the fatigue of back side of the clock flying. I had plenty of rest previous nights; but just not enough prior to this flight with a show after night. I woke up at midnight and drove to work after getting about 3 hrs rest. I should have vocalized my earlier concern to the First Officer about my concern that something didn't seem right when on final. And I should have gone around. We clearly did not have a green box on final and I always check that but did not this time for some reason. I will always check it in the future regardless. When using the HUD you must move your head a bit to see the display and the green box symbology. I did not and should have gone around. Train our pilots to recognize fatigue signs during critical phases of flight. Train our pilots ensure a 'Green Box' prior to the stable call. I should have gone around.

Data retrieved from NASA's ASRS site as of July 2013 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.