Atx small transport altitude deviation excursion from clearance altitude.

Attributes
ACN	120185
Time
Date	198908
Day	Thu
Local Time Of Day	1201 To 1800
Place
Locale Reference	atc facility : gsp
State Reference	SC
Altitude	msl bound lower : 19000 msl bound upper : 20000
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Controlling Facilities	artcc : ztl
Operator	common carrier : air taxi
Make Model Name	Small Transport, Low Wing, 2 Turboprop Eng
Flight Phase	cruise other descent other
Flight Plan	IFR
Person 1
Affiliation	company : air taxi
Function	flight crew : captain oversight : pic
Qualification	pilot : atp
Experience	flight time last 90 days : 150 flight time total : 3050
ASRS Report	120185
Person 2
Affiliation	company : air taxi
Function	flight crew : first officer
Qualification	pilot : commercial pilot : instrument
Events
Anomaly	altitude deviation : excursion from assigned altitude non adherence : clearance
Independent Detector	other controllera
Resolutory Action	controller : issued new clearance other
Consequence	Other
Supplementary
Primary Problem	Flight Crew Human Performance
Air Traffic Incident	Pilot Deviation

Narrative:

On aug/thu/89, we were flying from norfolk, va to greer, sc. We were cleared to descend from FL240 to FL180 with pilot's discretion to leave FL230 by ZTL. After arriving at FL230, ATC cleared us to descend to FL200. The clearance was read back to ATC as 'descend to FL200, pilot's discretion to FL180'. ATC did not correct the readback. Since the readback was not a question from the crew, nothing was noticed to be wrong among the crew. We descended to FL200 and then 75 NM out of greer, began a normal descent to FL180. Out of FL190 we called ATC 'out of FL190 for FL180'. This was a reminder to ATC that a lower altitude was needed. ATC then informed us that FL200 was the assigned altitude and then cleared us to FL180 no other traffic was observed or otherwise indicated. I believe this incident occurred as a result of a communication breakdown between ATC and crew. ATC should have corrected our readback of the clearance if it was in fact incorrect. Without this, there is no way for the crew to know what is expected of them. My suggestion to prevent a recurrence of this type of incident is for the crew to always report leaving an altitude when beginning a descent, even if the clearance was given with the phrase 'pilot's discretion'. This check serves as a backup in case ATC missed or did not understand your readback of the initial clearance.

Original NASA ASRS Text

Title: ATX SMT ALT DEVIATION EXCURSION FROM CLRNC ALT.

Narrative: ON AUG/THU/89, WE WERE FLYING FROM NORFOLK, VA TO GREER, SC. WE WERE CLRED TO DSND FROM FL240 TO FL180 WITH PLT'S DISCRETION TO LEAVE FL230 BY ZTL. AFTER ARRIVING AT FL230, ATC CLRED US TO DSND TO FL200. THE CLRNC WAS READ BACK TO ATC AS 'DSND TO FL200, PLT'S DISCRETION TO FL180'. ATC DID NOT CORRECT THE READBACK. SINCE THE READBACK WAS NOT A QUESTION FROM THE CREW, NOTHING WAS NOTICED TO BE WRONG AMONG THE CREW. WE DESCENDED TO FL200 AND THEN 75 NM OUT OF GREER, BEGAN A NORMAL DSCNT TO FL180. OUT OF FL190 WE CALLED ATC 'OUT OF FL190 FOR FL180'. THIS WAS A REMINDER TO ATC THAT A LOWER ALT WAS NEEDED. ATC THEN INFORMED US THAT FL200 WAS THE ASSIGNED ALT AND THEN CLRED US TO FL180 NO OTHER TFC WAS OBSERVED OR OTHERWISE INDICATED. I BELIEVE THIS INCIDENT OCCURRED AS A RESULT OF A COM BREAKDOWN BETWEEN ATC AND CREW. ATC SHOULD HAVE CORRECTED OUR READBACK OF THE CLRNC IF IT WAS IN FACT INCORRECT. WITHOUT THIS, THERE IS NO WAY FOR THE CREW TO KNOW WHAT IS EXPECTED OF THEM. MY SUGGESTION TO PREVENT A RECURRENCE OF THIS TYPE OF INCIDENT IS FOR THE CREW TO ALWAYS REPORT LEAVING AN ALT WHEN BEGINNING A DSCNT, EVEN IF THE CLRNC WAS GIVEN WITH THE PHRASE 'PLT'S DISCRETION'. THIS CHECK SERVES AS A BACKUP IN CASE ATC MISSED OR DID NOT UNDERSTAND YOUR READBACK OF THE INITIAL CLRNC.

Data retrieved from NASA's ASRS site as of August 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.