Clearance confusion creating altitude deviation.

Attributes
ACN	321820
Time
Date	199511
Day	Fri
Local Time Of Day	1201 To 1800
Place
Locale Reference	atc facility : lgc
State Reference	GA
Altitude	msl bound lower : 27000 msl bound upper : 29500
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Controlling Facilities	artcc : ztl
Operator	common carrier : air carrier
Make Model Name	B757 Undifferentiated or Other Model
Operating Under FAR Part	Part 121
Navigation In Use	Other Other
Flight Phase	climbout : intermediate altitude
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : atp pilot : flight engineer
Experience	flight time last 90 days : 150 flight time total : 17500 flight time type : 6500
ASRS Report	321820
Person 2
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : atp pilot : instrument pilot : flight engineer pilot : commercial
Experience	flight time last 90 days : 140 flight time total : 6000 flight time type : 600
ASRS Report	322137
Events
Anomaly	altitude deviation : overshoot other anomaly other
Independent Detector	other controllera
Resolutory Action	none taken : detected after the fact
Consequence	faa : reviewed incident with flight crew
Supplementary
Primary Problem	Ambiguous
Air Traffic Incident	other

Narrative:

Level at FL230. Center cleared us to FL370. Both myself, acting as PNF first officer and captain confirmed FL370, I read back to center, cleared to FL370. Passing FL295, center asked our altitude. We (I) responded, passing FL295 climbing FL370. Controller said he told us to climb to FL270 and we should descend to FL290. About 20 seconds later he said climb to FL310 and 1 min later cleared to FL370. There was no conflict, no evasive turns. No problem. But, whether controller said FL270 or FL370 we read back FL370. Controller did not monitor our readback! Supplemental information from acn 322137: nothing else was said about the potential misunderstanding about our altitude clearance. Remainder of flight was without incident.

Original NASA ASRS Text

Title: CLRNC CONFUSION CREATING ALTDEV.

Narrative: LEVEL AT FL230. CTR CLRED US TO FL370. BOTH MYSELF, ACTING AS PNF FO AND CAPT CONFIRMED FL370, I READ BACK TO CTR, CLRED TO FL370. PASSING FL295, CTR ASKED OUR ALT. WE (I) RESPONDED, PASSING FL295 CLBING FL370. CTLR SAID HE TOLD US TO CLB TO FL270 AND WE SHOULD DSND TO FL290. ABOUT 20 SECONDS LATER HE SAID CLB TO FL310 AND 1 MIN LATER CLRED TO FL370. THERE WAS NO CONFLICT, NO EVASIVE TURNS. NO PROB. BUT, WHETHER CTLR SAID FL270 OR FL370 WE READ BACK FL370. CTLR DID NOT MONITOR OUR READBACK! SUPPLEMENTAL INFO FROM ACN 322137: NOTHING ELSE WAS SAID ABOUT THE POTENTIAL MISUNDERSTANDING ABOUT OUR ALT CLRNC. REMAINDER OF FLT WAS WITHOUT INCIDENT.

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.