Altitude assignment as given by controller confuses flight crew. Clearance amended and corrected by ...

Attributes
ACN	206015
Time
Date	199203
Day	Sun
Local Time Of Day	1801 To 2400
Place
Locale Reference	atc facility : flm
State Reference	KY
Altitude	msl bound lower : 26600 msl bound upper : 28000
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Controlling Facilities	artcc : zid tower : bos
Operator	common carrier : air carrier
Make Model Name	Large Transport, Low Wing, 3 Turbojet Eng
Flight Phase	descent other
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : instrument pilot : flight engineer pilot : commercial pilot : atp
Experience	flight time last 90 days : 100 flight time total : 7700 flight time type : 500
ASRS Report	206015
Person 2
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : atp pilot : instrument pilot : commercial
Experience	flight time last 90 days : 100 flight time total : 7000 flight time type : 1000
ASRS Report	206009
Events
Anomaly	other anomaly other
Independent Detector	other controllera
Resolutory Action	controller : issued new clearance flight crew : exited adverse environment
Consequence	faa : reviewed incident with flight crew
Supplementary
Primary Problem	ATC Human Performance
Air Traffic Incident	other

Narrative:

We were cruising at FL310 and cleared to descend to FL280 with a request to expedite. Before we could answer, the controller repeated his request but changed the altitude to FL250. I answered back using FL250. The copilot asked for confirmation of altitude in view of the controller's conflicting requests. As we descended through FL29.6, the controller asked our altitude. I reported 'out of 29.6 for FL250' with emphasis on the 250. He 'rogered' us. As we descended through F26.7, the controller said with alarm 'maintain FL280, not 27.7!' I informed him we had been cleared to FL250 and had stated so on 2 separate occasions, but that we would climb back to FL280. Again with alarm, he told us not to climb back to 280. 'My mistake' he said. 'Continue to 250, you have traffic 10 mi ahead at FL270.' we immediately re-commenced our descent to FL250 after climbing back up to FL26.7. His confusion could have resulted in a real conflict.

Original NASA ASRS Text

Title: ALT ASSIGNMENT AS GIVEN BY CTLR CONFUSES FLC. CLRNC AMENDED AND CORRECTED BY CTLR.

Narrative: WE WERE CRUISING AT FL310 AND CLRED TO DSND TO FL280 WITH A REQUEST TO EXPEDITE. BEFORE WE COULD ANSWER, THE CTLR REPEATED HIS REQUEST BUT CHANGED THE ALT TO FL250. I ANSWERED BACK USING FL250. THE COPLT ASKED FOR CONFIRMATION OF ALT IN VIEW OF THE CTLR'S CONFLICTING REQUESTS. AS WE DSNDED THROUGH FL29.6, THE CTLR ASKED OUR ALT. I RPTED 'OUT OF 29.6 FOR FL250' WITH EMPHASIS ON THE 250. HE 'ROGERED' US. AS WE DSNDED THROUGH F26.7, THE CTLR SAID WITH ALARM 'MAINTAIN FL280, NOT 27.7!' I INFORMED HIM WE HAD BEEN CLRED TO FL250 AND HAD STATED SO ON 2 SEPARATE OCCASIONS, BUT THAT WE WOULD CLB BACK TO FL280. AGAIN WITH ALARM, HE TOLD US NOT TO CLB BACK TO 280. 'MY MISTAKE' HE SAID. 'CONTINUE TO 250, YOU HAVE TFC 10 MI AHEAD AT FL270.' WE IMMEDIATELY RE-COMMENCED OUR DSCNT TO FL250 AFTER CLBING BACK UP TO FL26.7. HIS CONFUSION COULD HAVE RESULTED IN A REAL CONFLICT.

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.

Altitude assignment as given by controller confuses flight crew. Clearance amended and corrected by controller.