Govt aircraft descends below assigned altitude on DME arc approach.

Attributes
ACN	166365
Time
Date	199012
Day	Sat
Local Time Of Day	0601 To 1200
Place
Locale Reference	atc facility : sjt
State Reference	TX
Altitude	msl bound lower : 2500 msl bound upper : 6000
Environment
Flight Conditions	IMC
Light	Daylight
Aircraft 1
Controlling Facilities	tracon : sjt tower : iah
Operator	other
Make Model Name	Small Transport, Low Wing, 2 Turboprop Eng
Flight Phase	descent : approach
Flight Plan	IFR
Person 1
Affiliation	government other
Function	flight crew : single pilot
Qualification	pilot : atp pilot : instrument
Experience	flight time last 90 days : 59 flight time total : 3091 flight time type : 77
ASRS Report	166365
Person 2
Affiliation	government : faa
Function	controller : approach
Qualification	controller : radar
Events
Anomaly	altitude deviation : excursion from assigned altitude non adherence : clearance
Independent Detector	other controllera
Resolutory Action	other
Consequence	faa : reviewed incident with flight crew
Supplementary
Primary Problem	Flight Crew Human Performance
Air Traffic Incident	Pilot Deviation

Narrative:

I was conducting an IFR flight from austin, tx, to san angelo, tx. Ft worth center handed me off to san angelo approach (non radar) and I was instructed to descend to 6000' MSL, intercept the 10 DME arc, and arc around to intercept the sjt 055 degree. This I did, but I descended to the altitudes as depicted on the approach. As I approached the sjt VOR on the 055 degree at 2500' MSL, I told approach where I was (right and altitude). I was told that I had not been cleared for the approach but to continue the approach anyway. I landed on runway 21 west/O incident. I was asked to call the tower, which I did. ATC informed me they were working another aircraft for the NDB approach for runway 3. The other aircraft was making their procedure turn outbnd while I was crossing the VOR. ATC wanted to impress upon me the potentially dangerous situation that had occurred. I agreed with him. ATC said they could file a report on the incident, but they would not.

Original NASA ASRS Text

Title: GOVT ACFT DESCENDS BELOW ASSIGNED ALT ON DME ARC APCH.

Narrative: I WAS CONDUCTING AN IFR FLT FROM AUSTIN, TX, TO SAN ANGELO, TX. FT WORTH CTR HANDED ME OFF TO SAN ANGELO APCH (NON RADAR) AND I WAS INSTRUCTED TO DSND TO 6000' MSL, INTERCEPT THE 10 DME ARC, AND ARC AROUND TO INTERCEPT THE SJT 055 DEG. THIS I DID, BUT I DSNDED TO THE ALTS AS DEPICTED ON THE APCH. AS I APCHED THE SJT VOR ON THE 055 DEG AT 2500' MSL, I TOLD APCH WHERE I WAS (R AND ALT). I WAS TOLD THAT I HAD NOT BEEN CLRED FOR THE APCH BUT TO CONTINUE THE APCH ANYWAY. I LANDED ON RWY 21 W/O INCIDENT. I WAS ASKED TO CALL THE TWR, WHICH I DID. ATC INFORMED ME THEY WERE WORKING ANOTHER ACFT FOR THE NDB APCH FOR RWY 3. THE OTHER ACFT WAS MAKING THEIR PROC TURN OUTBND WHILE I WAS XING THE VOR. ATC WANTED TO IMPRESS UPON ME THE POTENTIALLY DANGEROUS SITUATION THAT HAD OCCURRED. I AGREED WITH HIM. ATC SAID THEY COULD FILE A RPT ON THE INCIDENT, BUT THEY WOULD NOT.

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.