ZDV questions A320 flight crew after observing an altitude 1000 ft below a block altitude assignment...

Attributes
ACN	626105
Time
Date	200407
Day	Thu
Local Time Of Day	1801 To 2400
Place
Locale Reference	airport : den.airport
State Reference	CO
Altitude	msl bound lower : 35000 msl bound upper : 37000
Environment
Flight Conditions	Mixed
Weather Elements	Turbulence
Light	Night
Aircraft 1
Controlling Facilities	artcc : zdv.artcc tower : buf.tower
Operator	common carrier : air carrier
Make Model Name	A320
Operating Under FAR Part	Part 121
Navigation In Use	other
Flight Phase	cruise : level cruise : enroute altitude change
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : cfi pilot : multi engine pilot : instrument pilot : commercial pilot : atp
Experience	flight time last 90 days : 200 flight time total : 5300 flight time type : 250
ASRS Report	626105
Person 2
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Events
Anomaly	altitude deviation : excursion from assigned altitude other anomaly other
Independent Detector	atc equipment other atc equipment : radar other controllera
Resolutory Action	controller : issued new clearance controller : issued advisory
Consequence	faa : reviewed incident with flight crew
Supplementary
Problem Areas	Flight Crew Human Performance ATC Human Performance
Primary Problem	ATC Human Performance

Narrative:

We were wbound en route from jfk to oak. We were about 1/2 way into the flight and experiencing continuous light turbulence at FL370. Although this was an eastbound altitude, it was requested and subsequently approved by the previous en route controller. It was requested after considering the aircraft performance capability, as determined by the FMS. Earlier while cruising at FL350, we encountered a similar choppy ride. The ride at FL370 became choppy primarily due to an overcast layer which coincided with our altitude. I again checked the aircraft capability, and saw that we were still unable FL390. We requested a block from FL350-FL380. The controller then assigned block FL350-FL390, and explained that she could not assign FL380. As we flew wbound, various altitude changes were made for passenger comfort/turbulence avoidance. Approximately 120 NM east of den, I descended to FL360 keeping us below a layer. Upon reaching level at FL360, the center controller requested us to 'verify altitude.' I responded level at FL360. She then stated that we were assigned FL370-FL390. I challenged the controller, and asserted that we were assigned a block from FL350-FL390. She disputed this, at which point we requested a new block of FL350-FL370. This was subsequently assigned, and we continued at FL360 until a controller closer to oak assigned a descent to FL350. While I maintain that we were granted a clearance from FL350 to FL390, I cannot confirm it without a replay of the tape. If there was a deviation from the clearance, it may have been a combination of late hour ( domicile time), distraction (turbulence), and hearback expectation. The controller did not have any input after the revised clearance was issued, so I believe that a traffic conflict was not an immediate threat. In the future, I plan to be more vigilant when requesting block cruise altitudes, as it is out of the norm from routine flight operations.

Original NASA ASRS Text

Title: ZDV QUESTIONS A320 FLT CREW AFTER OBSERVING AN ALT 1000 FT BELOW A BLOCK ALT ASSIGNMENT DUE TO TURB. FLT CREW INSISTS THE LOWER ALT WAS PART OF BLOCK ALT ASSIGNMENT.

Narrative: WE WERE WBOUND ENRTE FROM JFK TO OAK. WE WERE ABOUT 1/2 WAY INTO THE FLT AND EXPERIENCING CONTINUOUS LIGHT TURB AT FL370. ALTHOUGH THIS WAS AN EBOUND ALT, IT WAS REQUESTED AND SUBSEQUENTLY APPROVED BY THE PREVIOUS ENRTE CTLR. IT WAS REQUESTED AFTER CONSIDERING THE ACFT PERFORMANCE CAPABILITY, AS DETERMINED BY THE FMS. EARLIER WHILE CRUISING AT FL350, WE ENCOUNTERED A SIMILAR CHOPPY RIDE. THE RIDE AT FL370 BECAME CHOPPY PRIMARILY DUE TO AN OVCST LAYER WHICH COINCIDED WITH OUR ALT. I AGAIN CHKED THE ACFT CAPABILITY, AND SAW THAT WE WERE STILL UNABLE FL390. WE REQUESTED A BLOCK FROM FL350-FL380. THE CTLR THEN ASSIGNED BLOCK FL350-FL390, AND EXPLAINED THAT SHE COULD NOT ASSIGN FL380. AS WE FLEW WBOUND, VARIOUS ALT CHANGES WERE MADE FOR PAX COMFORT/TURB AVOIDANCE. APPROX 120 NM E OF DEN, I DSNDED TO FL360 KEEPING US BELOW A LAYER. UPON REACHING LEVEL AT FL360, THE CTR CTLR REQUESTED US TO 'VERIFY ALT.' I RESPONDED LEVEL AT FL360. SHE THEN STATED THAT WE WERE ASSIGNED FL370-FL390. I CHALLENGED THE CTLR, AND ASSERTED THAT WE WERE ASSIGNED A BLOCK FROM FL350-FL390. SHE DISPUTED THIS, AT WHICH POINT WE REQUESTED A NEW BLOCK OF FL350-FL370. THIS WAS SUBSEQUENTLY ASSIGNED, AND WE CONTINUED AT FL360 UNTIL A CTLR CLOSER TO OAK ASSIGNED A DSCNT TO FL350. WHILE I MAINTAIN THAT WE WERE GRANTED A CLRNC FROM FL350 TO FL390, I CANNOT CONFIRM IT WITHOUT A REPLAY OF THE TAPE. IF THERE WAS A DEV FROM THE CLRNC, IT MAY HAVE BEEN A COMBINATION OF LATE HR ( DOMICILE TIME), DISTR (TURB), AND HEARBACK EXPECTATION. THE CTLR DID NOT HAVE ANY INPUT AFTER THE REVISED CLRNC WAS ISSUED, SO I BELIEVE THAT A TFC CONFLICT WAS NOT AN IMMEDIATE THREAT. IN THE FUTURE, I PLAN TO BE MORE VIGILANT WHEN REQUESTING BLOCK CRUISE ALTS, AS IT IS OUT OF THE NORM FROM ROUTINE FLT OPS.

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.

ZDV questions A320 flight crew after observing an altitude 1000 ft below a block altitude assignment due to turbulence. Flight crew insists the lower altitude was part of block altitude assignment.