While flying a localizer backcourse approach, the first officer began descent prematurely.

Attributes
ACN	147485
Time
Date	199006
Day	Sun
Local Time Of Day	0601 To 1200
Place
Locale Reference	airport : clt
State Reference	NC
Altitude	msl bound lower : 3100 msl bound upper : 3600
Environment
Flight Conditions	IMC
Light	Daylight
Aircraft 1
Controlling Facilities	tracon : clt tracon : dov
Operator	common carrier : air carrier
Make Model Name	Medium Large Transport, Low Wing, 2 Turbojet Eng
Navigation In Use	Other
Flight Phase	descent : approach
Route In Use	approach : straight in
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : atp
Experience	flight time last 90 days : 210 flight time total : 8000 flight time type : 200
ASRS Report	147485
Person 2
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : commercial pilot : instrument
Events
Anomaly	altitude deviation : excursion from assigned altitude non adherence : clearance non adherence : published procedure
Independent Detector	other flight crewa
Resolutory Action	flight crew : returned to intended course or assigned course
Consequence	Other
Supplementary
Primary Problem	Flight Crew Human Performance
Air Traffic Incident	Pilot Deviation

Narrative:

First officer began descent from localizer intercept alto of 3600' at 16 DME instead of 12.1 DME as depicted. He began a very shallow descent 300-500 FPM while on autoplt. He also disabled the altitude alert. He did not advise me and I didn't notice the descent until he reached 3100'. When I questioned him about it, he said something about a 3 degree G/south. I told him to fly the non precision approach as depicted.

Original NASA ASRS Text

Title: WHILE FLYING A LOCALIZER BACKCOURSE APCH, THE FO BEGAN DESCENT PREMATURELY.

Narrative: F/O BEGAN DSNT FROM LOC INTERCEPT ALTO OF 3600' AT 16 DME INSTEAD OF 12.1 DME AS DEPICTED. HE BEGAN A VERY SHALLOW DSNT 300-500 FPM WHILE ON AUTOPLT. HE ALSO DISABLED THE ALT ALERT. HE DID NOT ADVISE ME AND I DIDN'T NOTICE THE DSNT UNTIL HE REACHED 3100'. WHEN I QUESTIONED HIM ABOUT IT, HE SAID SOMETHING ABOUT A 3 DEG G/S. I TOLD HIM TO FLY THE NON PRECISION APCH AS DEPICTED.

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.