Confusion on response to request for altitude and heading change due to WX.

Attributes
ACN	121040
Time
Date	198908
Day	Sun
Place
Locale Reference	atc facility : jst
State Reference	PA
Altitude	msl bound lower : 22500 msl bound upper : 24000
Environment
Flight Conditions	IMC
Light	Dusk
Aircraft 1
Controlling Facilities	artcc : zob
Operator	common carrier : air carrier
Make Model Name	Medium Large Transport, Low Wing, 2 Turbojet Eng
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 pilot : commercial
Experience	flight time last 90 days : 150 flight time total : 8900 flight time type : 4500
ASRS Report	121040
Person 2
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : atp pilot : cfi pilot : instrument pilot : commercial
Experience	flight time last 90 days : 240 flight time total : 4500 flight time type : 600
ASRS Report	120502
Events
Anomaly	altitude deviation : excursion from assigned altitude other anomaly other
Independent Detector	other controllera other flight crewa
Resolutory Action	controller : issued new clearance flight crew : returned to intended course or assigned course
Consequence	Other
Supplementary
Primary Problem	Ambiguous
Air Traffic Incident	other

Narrative:

While en route toward johnstown VOR during cruise at FL240, approximately 50 mi southeast on the jet arwy, a substantial line of thunderstorms was evident, with several holes or breaks appearing in the line. We were experiencing moderate chop at FL240, and were about to ask ZOB for FL200, when we realized we had to deviate west of course. We asked ZOB for approximately a 30 degree left turn (to roughly 300 degrees) to avoid some buildups, when ZOB told us he could give us '300 degree heading until receiving dryer VOR, only if you can accept FL200.' since we wanted FL200, and direct dryer, we immediately accepted and were told, 'you've got it, 300 degrees until receiving dryer, then direct.' we turned to 300 degrees and began a descent out F FL240. When passing 22500' we were told we 'had no clearance to leave FL240!' we were told to level off at FL220, as there was 21000' traffic crossing. We had understood (or misunderstood) the clearance 'direct dryer if you can accept FL200' to be a clearance, direct dryer and descend to FL200.

Original NASA ASRS Text

Title: CONFUSION ON RESPONSE TO REQUEST FOR ALT AND HEADING CHANGE DUE TO WX.

Narrative: WHILE ENRTE TOWARD JOHNSTOWN VOR DURING CRUISE AT FL240, APPROX 50 MI SE ON THE JET ARWY, A SUBSTANTIAL LINE OF TSTMS WAS EVIDENT, WITH SEVERAL HOLES OR BREAKS APPEARING IN THE LINE. WE WERE EXPERIENCING MODERATE CHOP AT FL240, AND WERE ABOUT TO ASK ZOB FOR FL200, WHEN WE REALIZED WE HAD TO DEVIATE W OF COURSE. WE ASKED ZOB FOR APPROX A 30 DEG LEFT TURN (TO ROUGHLY 300 DEGS) TO AVOID SOME BUILDUPS, WHEN ZOB TOLD US HE COULD GIVE US '300 DEG HDG UNTIL RECEIVING DRYER VOR, ONLY IF YOU CAN ACCEPT FL200.' SINCE WE WANTED FL200, AND DIRECT DRYER, WE IMMEDIATELY ACCEPTED AND WERE TOLD, 'YOU'VE GOT IT, 300 DEGS UNTIL RECEIVING DRYER, THEN DIRECT.' WE TURNED TO 300 DEGS AND BEGAN A DSCNT OUT F FL240. WHEN PASSING 22500' WE WERE TOLD WE 'HAD NO CLRNC TO LEAVE FL240!' WE WERE TOLD TO LEVEL OFF AT FL220, AS THERE WAS 21000' TFC XING. WE HAD UNDERSTOOD (OR MISUNDERSTOOD) THE CLRNC 'DIRECT DRYER IF YOU CAN ACCEPT FL200' TO BE A CLRNC, DIRECT DRYER AND DSND TO FL200.

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.