Narrative:

While transitioning to a visual approach to runway 16L smf we received a check altitude alert from capital tower. Event occurred while starting approach from slightly above ILS GS (1900 ft MSL). While correcting to what to me appeared to be a visual 3.0 degree flight path we got the call from tower to check altitude (approximately 1500 ft AGL). PAPI's were extremely dim or not yet fully visible. Upon hearing the call from tower I returned my scan to inside and regained a proper GS. After the call from tower we also received glidepath alert from GPWS; which also brought my attention back inside to the ILS glidepath. Contributing factors: 1) fatigue: XA45 wakeup for an XC00 show. In addition it was the end of a 7:54 scheduled block day; duty day was scheduled for 10:14 hours. 2) perception: long and narrow runway in the middle of a vast field and valley. Visually I thought I was still above the 3.0 GS but in reality I wasn't.

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Original NASA ASRS Text

Title: B737-800 FLT CREW RECEIVES MSAW WARNING FROM SMF TWR WHILE SHOOTING A NIGHT VISUAL APCH.

Narrative: WHILE TRANSITIONING TO A VISUAL APCH TO RWY 16L SMF WE RECEIVED A CHK ALT ALERT FROM CAPITAL TWR. EVENT OCCURRED WHILE STARTING APCH FROM SLIGHTLY ABOVE ILS GS (1900 FT MSL). WHILE CORRECTING TO WHAT TO ME APPEARED TO BE A VISUAL 3.0 DEG FLT PATH WE GOT THE CALL FROM TWR TO CHK ALT (APPROX 1500 FT AGL). PAPI'S WERE EXTREMELY DIM OR NOT YET FULLY VISIBLE. UPON HEARING THE CALL FROM TWR I RETURNED MY SCAN TO INSIDE AND REGAINED A PROPER GS. AFTER THE CALL FROM TWR WE ALSO RECEIVED GLIDEPATH ALERT FROM GPWS; WHICH ALSO BROUGHT MY ATTN BACK INSIDE TO THE ILS GLIDEPATH. CONTRIBUTING FACTORS: 1) FATIGUE: XA45 WAKEUP FOR AN XC00 SHOW. IN ADDITION IT WAS THE END OF A 7:54 SCHEDULED BLOCK DAY; DUTY DAY WAS SCHEDULED FOR 10:14 HRS. 2) PERCEPTION: LONG AND NARROW RWY IN THE MIDDLE OF A VAST FIELD AND VALLEY. VISUALLY I THOUGHT I WAS STILL ABOVE THE 3.0 GS BUT IN REALITY I WASN'T.

Data retrieved from NASA's ASRS site as of January 2009 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.