International flight crew misunderstood clearance.

Attributes
ACN	432431
Time
Date	199902
Day	Sat
Local Time Of Day	0001 To 0600
Place
Locale Reference	atc facility : zny.artcc
State Reference	NY
Altitude	msl bound lower : 31000 msl bound upper : 33000
Aircraft 1
Controlling Facilities	artcc : zny.artcc
Operator	common carrier : air carrier
Make Model Name	Commercial Fixed Wing
Operating Under FAR Part	Part 121
Route In Use	enroute : atlantic
Flight Plan	IFR
Person 1
Affiliation	other
Function	other personnel other
Experience	controller non radar : 2
ASRS Report	432431
Person 2
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : atp
Events
Anomaly	altitude deviation : excursion from assigned altitude non adherence : clearance non adherence : far non adherence : required legal separation
Independent Detector	other controllera other other : 1
Resolutory Action	none taken : detected after the fact
Supplementary
Problem Areas	Flight Crew Human Performance ATC Human Performance Airspace Structure
Primary Problem	Flight Crew Human Performance
Air Traffic Incident	Operational Error Pilot Deviation

Narrative:

At XA11Z, aircraft X requested a change of altitude from FL310 to FL350. 14 mins later, ZNY issued this clearance: 'atcc ctam F320 rr unable requested altitude due traffic.' the ro delivered the clearance verbatim, but the readback was incorrect. The flight read back: 'aircraft X leaving 310, climbing 330 report reaching.' the ro responded with: 'leaving FL310 climbing to FL330 you will report level.' at XA35Z, the flight reported: '...lvl 330.' when the flight reported lvl at FL330, the ro acknowledged seeing FL320 in the ATC clearance that appeared in the lower portion of the display. She said that she saw the difference but she thought that she had made a typing error. Instead of typing the words that she heard through the headset (as verified by the audio tape), she then typed 'lvl FL320.' (it was later reported to new york management by new york ARTCC, that the controller was getting ready to ask about why the readback showed FL330 instead of FL320, but upon receiving the 'lvl FL320 report, he/she decided to not call.) aircraft X continued a FL330 without adequate separation from other flts for 1 hour and 9 mins.

Original NASA ASRS Text

Title: INTL FLC MISUNDERSTOOD CLRNC.

Narrative: AT XA11Z, ACFT X REQUESTED A CHANGE OF ALT FROM FL310 TO FL350. 14 MINS LATER, ZNY ISSUED THIS CLRNC: 'ATCC CTAM F320 RR UNABLE REQUESTED ALT DUE TFC.' THE RO DELIVERED THE CLRNC VERBATIM, BUT THE READBACK WAS INCORRECT. THE FLT READ BACK: 'ACFT X LEAVING 310, CLBING 330 RPT REACHING.' THE RO RESPONDED WITH: 'LEAVING FL310 CLBING TO FL330 YOU WILL RPT LEVEL.' AT XA35Z, THE FLT RPTED: '...LVL 330.' WHEN THE FLT RPTED LVL AT FL330, THE RO ACKNOWLEDGED SEEING FL320 IN THE ATC CLRNC THAT APPEARED IN THE LOWER PORTION OF THE DISPLAY. SHE SAID THAT SHE SAW THE DIFFERENCE BUT SHE THOUGHT THAT SHE HAD MADE A TYPING ERROR. INSTEAD OF TYPING THE WORDS THAT SHE HEARD THROUGH THE HEADSET (AS VERIFIED BY THE AUDIO TAPE), SHE THEN TYPED 'LVL FL320.' (IT WAS LATER RPTED TO NEW YORK MGMNT BY NEW YORK ARTCC, THAT THE CTLR WAS GETTING READY TO ASK ABOUT WHY THE READBACK SHOWED FL330 INSTEAD OF FL320, BUT UPON RECEIVING THE 'LVL FL320 RPT, HE/SHE DECIDED TO NOT CALL.) ACFT X CONTINUED A FL330 WITHOUT ADEQUATE SEPARATION FROM OTHER FLTS FOR 1 HR AND 9 MINS.

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.