Air carrier X unauthorized descent from assigned altitude. Pilot deviation.

Attributes
ACN	147681
Time
Date	199006
Day	Wed
Local Time Of Day	1201 To 1800
Place
Locale Reference	atc facility : rdm
State Reference	OR
Altitude	msl bound lower : 8000 msl bound upper : 9000
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Controlling Facilities	artcc : zse
Operator	common carrier : air carrier
Make Model Name	Light Transport
Flight Phase	cruise other
Route In Use	enroute : direct
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : atp
Experience	flight time last 90 days : 150 flight time total : 6000 flight time type : 2000
ASRS Report	147681
Person 2
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : instrument pilot : commercial
Experience	flight time last 90 days : 250 flight time total : 3500
ASRS Report	148331
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	Other
Supplementary
Primary Problem	Flight Crew Human Performance
Air Traffic Incident	Pilot Deviation

Narrative:

Air carrier X from pdx to rdm. We were cleared to 10000' and then 'cleared to 9000', cleared to the rdm VOR via the VOR-a profile.' this is how the clearance was stated. Both of us pilots discussed the clearance and since the altitude was stated first we both believed that we were cleared to the lower altitudes of the profile. Had the clearance been 'cleared to the rdm VOR via the VOR-a profile maintain 9000'' I do not believe this would have occurred. There were two different controller voices on frequency and because of the workload we were not able to get a transmission in to bring clarity to our questions. Supplemental information from acn 148331. While en route to redmond, from portland, was given a clearance to the redmond airport, (roberts field) by VOR-a approach procedure. The clearance was given after we were given the instructions to descend to 9000'. While following the instructions from the controller to follow the VOR-a approach procedure we descended to 8000' when we were within 15 mi northwest of the 10 DME arc. (As per the procedure). Just prior to intercepting the DME arc, the controller advised us that he wanted us at 9000'. However, the VOR-a procedure which he directed us to follow indicates 8000' when on the R-295 within 20.0 DME. We immediately climbed back to 9000', but advised that the clearance was apparently in error or confusing in that it leads you to think that the procedure was what the controller wanted us to follow.

Original NASA ASRS Text

Title: ACR X UNAUTH DESCENT FROM ASSIGNED ALT. PLTDEV.

Narrative: ACR X FROM PDX TO RDM. WE WERE CLRED TO 10000' AND THEN 'CLRED TO 9000', CLRED TO THE RDM VOR VIA THE VOR-A PROFILE.' THIS IS HOW THE CLRNC WAS STATED. BOTH OF US PLTS DISCUSSED THE CLRNC AND SINCE THE ALT WAS STATED FIRST WE BOTH BELIEVED THAT WE WERE CLRED TO THE LOWER ALTS OF THE PROFILE. HAD THE CLRNC BEEN 'CLRED TO THE RDM VOR VIA THE VOR-A PROFILE MAINTAIN 9000'' I DO NOT BELIEVE THIS WOULD HAVE OCCURRED. THERE WERE TWO DIFFERENT CTLR VOICES ON FREQ AND BECAUSE OF THE WORKLOAD WE WERE NOT ABLE TO GET A XMISSION IN TO BRING CLARITY TO OUR QUESTIONS. SUPPLEMENTAL INFO FROM ACN 148331. WHILE ENRTE TO REDMOND, FROM PORTLAND, WAS GIVEN A CLRNC TO THE REDMOND ARPT, (ROBERTS FIELD) BY VOR-A APCH PROC. THE CLRNC WAS GIVEN AFTER WE WERE GIVEN THE INSTRUCTIONS TO DSND TO 9000'. WHILE FOLLOWING THE INSTRUCTIONS FROM THE CTLR TO FOLLOW THE VOR-A APCH PROC WE DSNDED TO 8000' WHEN WE WERE WITHIN 15 MI NW OF THE 10 DME ARC. (AS PER THE PROC). JUST PRIOR TO INTERCEPTING THE DME ARC, THE CTLR ADVISED US THAT HE WANTED US AT 9000'. HOWEVER, THE VOR-A PROC WHICH HE DIRECTED US TO FOLLOW INDICATES 8000' WHEN ON THE R-295 WITHIN 20.0 DME. WE IMMEDIATELY CLBED BACK TO 9000', BUT ADVISED THAT THE CLRNC WAS APPARENTLY IN ERROR OR CONFUSING IN THAT IT LEADS YOU TO THINK THAT THE PROC WAS WHAT THE CTLR WANTED US TO FOLLOW.

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.