B-757 flight crew descended below the prescribed altitude on the arrival after all altitude limits a...

Attributes
ACN	1293109
Time
Date	201509
Local Time Of Day	1801-2400
Place
Locale Reference	OAK.Airport
State Reference	CA
Environment
Flight Conditions	VMC
Light	Night
Aircraft 1
Make Model Name	B757-200
Operating Under FAR Part	Part 121
Flight Phase	Descent
Route In Use	STAR EMZOH ONE
Flight Plan	IFR
Component
Aircraft Component	FMS/FMC
Person 1
Function	Captain Pilot Not Flying
Qualification	Flight Crew Air Transport Pilot (ATP)
Person 2
Function	First Officer Pilot Flying
Qualification	Flight Crew Air Transport Pilot (ATP)
Events
Anomaly	Aircraft Equipment Problem Less Severe Deviation - Altitude Crossing Restriction Not Met Deviation - Altitude Overshoot Deviation - Procedural Published Material / Policy Deviation - Procedural Clearance Inflight Event / Encounter CFTT / CFIT

Narrative:

On descent we were cleared to descend via the emzoh 1 arrival to 4100 msl. First officer (PF) had briefed the arrival and approach and we had both confirmed all altitude/speed restrictions were in the FMS. We began our descent and were in VNAV pth. We were then given a speed reduction to 250 KIAS. PF opened the speed window and selected 250. I was looking through the HUD and was switching between evas and regular vision when I remarked that we seemed closer to the terrain than I normally thought. We then both noticed that all of our altitude restrictions on the arrival had deleted and we were approx. 1000 ft below the profile. We leveled off and informed norcal who seemed to have no issue with us. They gave us a descent to 5600 MSL and a heading of 280 for the visual at oak. First officer and I extensively debriefed the event and neither of us can come up with an answer of why the restrictions were deleted. I have a call into a check airman to discuss this further as I can't figure this one out. Lesson learned is for me to spend less time in the HUD as pm and more time monitoring our flight path.

Original NASA ASRS Text

Title: B-757 flight crew descended below the prescribed altitude on the arrival after all altitude limits and restrictions were deleted in the FMC for the EMZOH1 STAR being flown. Crew received new clearance from ATC after visually noticing the terrain proximity.

Narrative: On descent we were cleared to descend via the EMZOH 1 arrival to 4100 msl. FO (PF) had briefed the arrival and approach and we had both confirmed all altitude/speed restrictions were in the FMS. We began our descent and were in VNAV PTH. We were then given a speed reduction to 250 KIAS. PF opened the speed window and selected 250. I was looking through the HUD and was switching between EVAS and regular vision when I remarked that we seemed closer to the terrain than I normally thought. We then both noticed that ALL of our altitude restrictions on the arrival had deleted and we were approx. 1000 ft below the profile. We leveled off and informed Norcal who seemed to have no issue with us. They gave us a descent to 5600 MSL and a heading of 280 for the visual at OAK. FO and I extensively debriefed the event and neither of us can come up with an answer of why the restrictions were deleted. I have a call into a Check Airman to discuss this further as I can't figure this one out. Lesson learned is for me to spend less time in the HUD as PM and more time monitoring our flight path.

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.