Arc X thought approach clearance had been issued. Unauthorized descent from assigned altitude.

Attributes
ACN	296398
Time
Date	199502
Day	Sun
Local Time Of Day	1201 To 1800
Place
Locale Reference	atc facility : jac
State Reference	WY
Altitude	msl bound lower : 15000 msl bound upper : 16000
Environment
Flight Conditions	IMC
Light	Daylight
Aircraft 1
Controlling Facilities	tracon : phl
Operator	common carrier : air carrier
Make Model Name	Xingu EMB-121 All Series
Operating Under FAR Part	Part 121
Navigation In Use	Other Other
Flight Phase	cruise other
Route In Use	enroute : direct enroute airway : zlc
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : atp
Experience	flight time last 90 days : 250 flight time total : 6100 flight time type : 1800
ASRS Report	296398
Person 2
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : atp
Experience	flight time last 90 days : 300 flight time total : 3500 flight time type : 300
ASRS Report	296418
Events
Anomaly	altitude deviation : excursion from assigned altitude non adherence : clearance
Independent Detector	other controllera
Resolutory Action	flight crew : returned to intended course or assigned course other
Consequence	faa : assigned or threatened penalties faa : investigated
Supplementary
Primary Problem	Flight Crew Human Performance
Air Traffic Incident	Pilot Deviation

Narrative:

Problem arose because we assumed that we were cleared for the approach -- we were concerned that we had to descend from 16000- 12700 ft in a short period of time. It would have been nice if ATC had told us that we were to expect clearance for the approach at some time, and about any traffic that we would have to wait for. Since there was no efc or traffic that we knew of, we assumed that after joining the arc we were cleared for the approach. There had been a lot of bad WX flying during the previous week, which may have effected my performance.

Original NASA ASRS Text

Title: ARC X THOUGHT APCH CLRNC HAD BEEN ISSUED. UNAUTH DSCNT FROM ASSIGNED ALT.

Narrative: PROB AROSE BECAUSE WE ASSUMED THAT WE WERE CLRED FOR THE APCH -- WE WERE CONCERNED THAT WE HAD TO DSND FROM 16000- 12700 FT IN A SHORT PERIOD OF TIME. IT WOULD HAVE BEEN NICE IF ATC HAD TOLD US THAT WE WERE TO EXPECT CLRNC FOR THE APCH AT SOME TIME, AND ABOUT ANY TFC THAT WE WOULD HAVE TO WAIT FOR. SINCE THERE WAS NO EFC OR TFC THAT WE KNEW OF, WE ASSUMED THAT AFTER JOINING THE ARC WE WERE CLRED FOR THE APCH. THERE HAD BEEN A LOT OF BAD WX FLYING DURING THE PREVIOUS WK, WHICH MAY HAVE EFFECTED MY PERFORMANCE.

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.