A C172 CFI allowed his student to descend before intercepting the localizer in sat's airspace.

Attributes
ACN	592965
Time
Date	200309
Day	Sun
Local Time Of Day	1201 To 1800
Place
Locale Reference	airport : sat.airport
State Reference	TX
Altitude	msl bound lower : 3300 msl bound upper : 4000
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Controlling Facilities	tracon : sat.tracon tower : hts.tower
Operator	general aviation : instructional
Make Model Name	Skyhawk 172/Cutlass 172
Operating Under FAR Part	Part 91
Flight Plan	IFR
Person 1
Affiliation	other
Function	flight crew : single pilot instruction : instructor oversight : pic
Qualification	pilot : multi engine pilot : cfi pilot : commercial pilot : instrument
Experience	flight time last 90 days : 100 flight time total : 710 flight time type : 550
ASRS Report	592965
Person 2
Affiliation	other
Function	flight crew : single pilot instruction : trainee
Events
Anomaly	altitude deviation : excursion from assigned altitude non adherence : far non adherence : clearance
Independent Detector	other controllera
Resolutory Action	none taken : detected after the fact
Supplementary
Problem Areas	Flight Crew Human Performance
Primary Problem	Flight Crew Human Performance
Air Traffic Incident	Pilot Deviation

Narrative:

We were being vectored for the ILS runway 12R sat. When we were about 12 mi out on a 30 degree intercept, I told my student to descend from 4000 ft. The controller was busy and the radios were not very clear. ATC had only instructed us to turn to 090 degrees and intercept the localizer. I doubted myself, but allowed my student to descend anyway to 3000 ft, since this was the clearance I was used to getting every other time. To prevent this from happening again, I should pay more attention to my clearance.

Original NASA ASRS Text

Title: A C172 CFI ALLOWED HIS STUDENT TO DSND BEFORE INTERCEPTING THE LOC IN SAT'S AIRSPACE.

Narrative: WE WERE BEING VECTORED FOR THE ILS RWY 12R SAT. WHEN WE WERE ABOUT 12 MI OUT ON A 30 DEG INTERCEPT, I TOLD MY STUDENT TO DSND FROM 4000 FT. THE CTLR WAS BUSY AND THE RADIOS WERE NOT VERY CLR. ATC HAD ONLY INSTRUCTED US TO TURN TO 090 DEGS AND INTERCEPT THE LOC. I DOUBTED MYSELF, BUT ALLOWED MY STUDENT TO DSND ANYWAY TO 3000 FT, SINCE THIS WAS THE CLRNC I WAS USED TO GETTING EVERY OTHER TIME. TO PREVENT THIS FROM HAPPENING AGAIN, I SHOULD PAY MORE ATTN TO MY CLRNC.

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.