Descent below lda/DME published altitude. Wrong NAVAID.

Attributes
ACN	305820
Time
Date	199505
Day	Mon
Local Time Of Day	1201 To 1800
Place
Locale Reference	airport : stl
State Reference	MO
Altitude	msl bound lower : 3600 msl bound upper : 5500
Environment
Flight Conditions	Mixed
Light	Daylight
Aircraft 1
Controlling Facilities	tracon : stl tower : tpa
Operator	common carrier : air carrier
Make Model Name	Commercial Fixed Wing
Operating Under FAR Part	Part 121
Navigation In Use	Other Other
Flight Phase	descent : approach
Route In Use	enroute : on vectors
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : atp
Experience	flight time last 90 days : 200 flight time total : 9000 flight time type : 1000
ASRS Report	305820
Person 2
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : atp
Experience	flight time last 90 days : 240 flight time total : 9500 flight time type : 6500
ASRS Report	305693
Events
Anomaly	altitude deviation : crossing restriction not met non adherence : published procedure non adherence : clearance
Independent Detector	other controllera other flight crewa
Resolutory Action	flight crew : returned to intended course or assigned course other
Consequence	Other
Supplementary
Primary Problem	Flight Crew Human Performance
Air Traffic Incident	Pilot Deviation

Narrative:

Our flight was on vector to lda/DME approach runway 12L at stl. Approach was briefed and radios tuned but I had gone back to st. Louis VOR to make a descent fix. On vector I was concentrating on acquiring parallel ILS traffic and did not switch back to lda/DME. With proper inbound course set in, when cleared to 'maintain 5500 ft till established, cleared lda/DME and runway 12L' I intercepted inbound course to st. Louis VOR, and descended to 3600 ft using st. Louis DME. First officer noticed discrepancy and called for frequency switch to stl at the same time I noted FMC/DME difference. Power was added and climb to proper altitude initiated when approach called 'we show you at 3600 ft' proper profile was intercepted and descent to landing resumed at proper DME. Parallel traffic and terrain in sight, at all times. Supplemental information from acn 305693: we had parallel traffic off to our right that I kept in sight entire time, which meant missing the wrong frequency being tuned.

Original NASA ASRS Text

Title: DSCNT BELOW LDA/DME PUBLISHED ALT. WRONG NAVAID.

Narrative: OUR FLT WAS ON VECTOR TO LDA/DME APCH RWY 12L AT STL. APCH WAS BRIEFED AND RADIOS TUNED BUT I HAD GONE BACK TO ST. LOUIS VOR TO MAKE A DSCNT FIX. ON VECTOR I WAS CONCENTRATING ON ACQUIRING PARALLEL ILS TFC AND DID NOT SWITCH BACK TO LDA/DME. WITH PROPER INBOUND COURSE SET IN, WHEN CLRED TO 'MAINTAIN 5500 FT TILL ESTABLISHED, CLRED LDA/DME AND RWY 12L' I INTERCEPTED INBOUND COURSE TO ST. LOUIS VOR, AND DSNDED TO 3600 FT USING ST. LOUIS DME. FO NOTICED DISCREPANCY AND CALLED FOR FREQ SWITCH TO STL AT THE SAME TIME I NOTED FMC/DME DIFFERENCE. PWR WAS ADDED AND CLB TO PROPER ALT INITIATED WHEN APCH CALLED 'WE SHOW YOU AT 3600 FT' PROPER PROFILE WAS INTERCEPTED AND DSCNT TO LNDG RESUMED AT PROPER DME. PARALLEL TFC AND TERRAIN IN SIGHT, AT ALL TIMES. SUPPLEMENTAL INFO FROM ACN 305693: WE HAD PARALLEL TFC OFF TO OUR R THAT I KEPT IN SIGHT ENTIRE TIME, WHICH MEANT MISSING THE WRONG FREQ BEING TUNED.

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.