B757 flight crew reports descending below 14;820 ft prior to anbur during the RNAV runway 35 approac...

Attributes
ACN	921001
Time
Date	201011
Local Time Of Day	1801-2400
Place
Locale Reference	SEQU.Airport
State Reference	FO
Environment
Flight Conditions	VMC
Light	Night
Aircraft 1
Make Model Name	B757-200
Operating Under FAR Part	Part 121
Flight Phase	Initial Approach
Flight Plan	IFR
Component
Aircraft Component	Autoflight System
Person 1
Function	Pilot Not Flying Captain
Qualification	Flight Crew Air Transport Pilot (ATP)
Person 2
Function	Pilot Flying First Officer
Events
Anomaly	Deviation - Altitude Crossing Restriction Not Met Deviation - Procedural Clearance Deviation - Procedural Published Material / Policy

Narrative:

On initial approach to sequ; RNAV (rnp) runway 35; between dagma and anbur a descent below the anbur restriction of 14;820 ft occurred to approximately 13;900 ft. An immediate correction and return to 14;800 ft was initiated. No terrain cautions or warnings occurred. A major contributer at the time of the incident was VNAV path had changed to VNAV speed; and was not immediately noticed. The FAF altitude of 11;500 ft that was set in the MCP was not reset to 14;900 ft for anbur when in VNAV speed. Strict adherence to all company procedures for sequ would have most likely prevented this unfortunate event. I think the first officer's mental alertness (tired) could have played a part; although when asked he denied it.

Original NASA ASRS Text

Title: B757 Flight Crew reports descending below 14;820 FT prior to ANBUR during the RNAV Runway 35 approach to SEQU. VNAV had become disengaged without the crew noticing.

Narrative: On initial approach to SEQU; RNAV (RNP) Runway 35; between DAGMA and ANBUR a descent below the ANBUR restriction of 14;820 FT occurred to approximately 13;900 FT. An immediate correction and return to 14;800 FT was initiated. No terrain cautions or warnings occurred. A major contributer at the time of the incident was VNAV PATH had changed to VNAV SPD; and was not immediately noticed. The FAF altitude of 11;500 FT that was set in the MCP was not reset to 14;900 FT for ANBUR when in VNAV SPD. Strict adherence to all company procedures for SEQU would have most likely prevented this unfortunate event. I think the First Officer's mental alertness (tired) could have played a part; although when asked he denied it.

Data retrieved from NASA's ASRS site as of April 2012 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.

B757 flight crew reports descending below 14;820 ft prior to anbur during the RNAV runway 35 approach to sequ. VNAV had become disengaged without the crew noticing.