MD11 flight crew reports descending below the FAF altitude after altitude capture with autopilot eng...

Attributes
ACN	1125565
Time
Date	201310
Local Time Of Day	0601-1200
Place
Locale Reference	ZZZ.Airport
State Reference	US
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Make Model Name	MD-11
Operating Under FAR Part	Part 121
Flight Phase	Final Approach
Route In Use	Other Controlled
Component
Aircraft Component	MCP
Person 1
Function	Pilot Not Flying Relief Pilot
Experience	Flight Crew Last 90 Days 145 Flight Crew Total 10000 Flight Crew Type 4000
Person 2
Function	Pilot Flying First Officer
Qualification	Flight Crew Flight Engineer Flight Crew Multiengine Flight Crew Instrument Flight Crew Flight Instructor Flight Crew Air Transport Pilot (ATP)
Experience	Flight Crew Last 90 Days 36 Flight Crew Total 8000
Events
Anomaly	Aircraft Equipment Problem Less Severe Deviation - Altitude Excursion From Assigned Altitude Deviation - Altitude Crossing Restriction Not Met Deviation - Procedural Published Material / Policy Deviation - Procedural Clearance

Narrative:

We were cleared for an RNAV approach. First officer was pilot flying while the captain was pilot not flying. Weather was VMC below 5;000 ft AGL. Horizontal visibility was unlimited. We called the field visually at least 15 miles away. We were leveled off at 1;600 ft 5 miles prior to the FAF. We were hooked up to the autopilot and in navigation and prof. He entered in the RNAV minimums of 660 ft on the fcp as we were on the approach phase. I reminded the captain about the .3 rnp on the reference page and he then entered it in. Almost immediately; the aircraft started a descent while we were yet 2 miles prior to the FAF. We all were aware of the deviation; caught and corrected it after a descent of approximately 400 ft. The pilot flying corrected to 1;550 ft MSL acquired the VASI and manually flew the approach visually. When on the early descent; the controller transmitted to us to 'check our altimeter setting and altitude.' we responded that we were correcting and that we were under control. As we were in visual conditions and on a visual approach backed up by the RNAV and as the controller asked only if we would check our instruments; we thought that we were safe from any type of ATC deviation issues. At no time were we unsafe in our approach. At no time did the controller use the pilot deviation notification procedures as outlined in the FAA regulations under provisions of paragraph 2-1-26 of the ATC manual asking us to contact the FAA.

Original NASA ASRS Text

Title: MD11 flight crew reports descending below the FAF altitude after altitude capture with autopilot engaged; when the MDA is set in the FCP window. The aircraft descends 400 FT before climbing back and ATC takes notice.

Narrative: We were cleared for an RNAV approach. First Officer was pilot flying while the Captain was pilot not flying. Weather was VMC below 5;000 FT AGL. Horizontal visibility was unlimited. We called the field visually at least 15 miles away. We were leveled off at 1;600 FT 5 miles prior to the FAF. We were hooked up to the autopilot and in NAV and PROF. He entered in the RNAV minimums of 660 FT on the FCP as we were on the approach phase. I reminded the Captain about the .3 RNP on the REF page and he then entered it in. Almost immediately; the aircraft started a descent while we were yet 2 miles prior to the FAF. We all were aware of the deviation; caught and corrected it after a descent of approximately 400 FT. The pilot flying corrected to 1;550 FT MSL acquired the VASI and manually flew the approach visually. When on the early descent; the Controller transmitted to us to 'check our altimeter setting and altitude.' We responded that we were correcting and that we were under control. As we were in visual conditions and on a visual approach backed up by the RNAV and as the Controller asked only if we would check our instruments; we thought that we were safe from any type of ATC deviation issues. At no time were we unsafe in our approach. At no time did the Controller use the pilot deviation notification procedures as outlined in the FAA Regulations under provisions of paragraph 2-1-26 of the ATC manual asking us to contact the FAA.

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.

MD11 flight crew reports descending below the FAF altitude after altitude capture with autopilot engaged; when the MDA is set in the fcp window. The aircraft descends 400 ft before climbing back and ATC takes notice.