A B737 flight descended below clearance altitude. Controller intervened and issued visual approach c...

Attributes
ACN	313900
Time
Date	199508
Day	Sun
Local Time Of Day	0601 To 1200
Place
Locale Reference	atc facility : pxr airport : phx
State Reference	AZ
Altitude	msl bound lower : 5000 msl bound upper : 6000
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Controlling Facilities	tracon : phx
Operator	common carrier : air carrier
Make Model Name	B737 Undifferentiated or Other Model
Operating Under FAR Part	Part 121
Flight Phase	descent other
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : cfi pilot : atp
Experience	flight time last 90 days : 240 flight time total : 11000 flight time type : 7000
ASRS Report	313900
Person 2
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : atp
Experience	flight time last 90 days : 125 flight time total : 3500
ASRS Report	313157
Events
Anomaly	aircraft equipment problem : less severe altitude deviation : overshoot non adherence : clearance
Independent Detector	aircraft equipment other aircraft equipment : unspecified other controllera
Resolutory Action	controller : issued new clearance other other
Consequence	Other
Supplementary
Primary Problem	Flight Crew Human Performance
Air Traffic Incident	Pilot Deviation

Narrative:

At 10000 ft assigned 6000 ft during descent experienced minor mechanical problem. Dealt with problem and had first officer run checklist. Heard just 1 altitude alert chime then began to level off at 5000 ft. Then noticed 6000 ft in alert window. No known conflict. TCASII gave no alerts, but we possibly went below TCA B floor. First officer was fairly new. I was distracted, and not very concerned with flight path due to high altitude, good visibility, airport in sight, very little traffic. Controller did not seem concerned. Supplemental information from acn 313157: the captain believed he was cleared for the visual approach. I was distracted inside the cockpit and missed the deviation until we were asked by the controller what our altitude was and he cleared us for the visual approach at that time. I'll be more diligent ensuring that PF levels at the correct altitude, especially during visual approachs when everyone is looking outside.

Original NASA ASRS Text

Title: A B737 FLT DSNDED BELOW CLRNC ALT. CTLR INTERVENED AND ISSUED VISUAL APCH CLRNC.

Narrative: AT 10000 FT ASSIGNED 6000 FT DURING DSCNT EXPERIENCED MINOR MECHANICAL PROB. DEALT WITH PROB AND HAD FO RUN CHKLIST. HEARD JUST 1 ALT ALERT CHIME THEN BEGAN TO LEVEL OFF AT 5000 FT. THEN NOTICED 6000 FT IN ALERT WINDOW. NO KNOWN CONFLICT. TCASII GAVE NO ALERTS, BUT WE POSSIBLY WENT BELOW TCA B FLOOR. FO WAS FAIRLY NEW. I WAS DISTRACTED, AND NOT VERY CONCERNED WITH FLT PATH DUE TO HIGH ALT, GOOD VISIBILITY, ARPT IN SIGHT, VERY LITTLE TFC. CTLR DID NOT SEEM CONCERNED. SUPPLEMENTAL INFO FROM ACN 313157: THE CAPT BELIEVED HE WAS CLRED FOR THE VISUAL APCH. I WAS DISTRACTED INSIDE THE COCKPIT AND MISSED THE DEV UNTIL WE WERE ASKED BY THE CTLR WHAT OUR ALT WAS AND HE CLRED US FOR THE VISUAL APCH AT THAT TIME. I'LL BE MORE DILIGENT ENSURING THAT PF LEVELS AT THE CORRECT ALT, ESPECIALLY DURING VISUAL APCHS WHEN EVERYONE IS LOOKING OUTSIDE.

Data retrieved from NASA's ASRS site as of July 2007 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.

A B737 flight descended below clearance altitude. Controller intervened and issued visual approach clearance.