Commuter aircraft misinterprets descent clearance. Controller upset.

Attributes
ACN	285436
Time
Date	199410
Day	Mon
Local Time Of Day	1801 To 2400
Place
Locale Reference	atc facility : gjt
State Reference	CO
Altitude	msl bound lower : 12000 msl bound upper : 24000
Environment
Flight Conditions	VMC
Light	Dusk
Aircraft 1
Operator	common carrier : air carrier
Make Model Name	Commercial Fixed Wing
Operating Under FAR Part	Part 135
Navigation In Use	Other Other
Flight Phase	cruise other
Route In Use	enroute : direct enroute airway : zdv
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : atp
Experience	flight time last 90 days : 240 flight time total : 3500 flight time type : 240
ASRS Report	285436
Person 2
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : cfi pilot : atp
Experience	flight time last 90 days : 200 flight time total : 9000 flight time type : 3500
ASRS Report	285315
Events
Anomaly	altitude deviation : undershoot non adherence : clearance
Independent Detector	other controllera
Resolutory Action	flight crew : returned to intended course or assigned course flight crew : became reoriented other
Consequence	Other
Supplementary
Primary Problem	Flight Crew Human Performance
Air Traffic Incident	Pilot Deviation

Narrative:

Cruising at FL250, ZDV gave us a pilot's discretion to FL240. We acknowledged and remained at FL250. We were then told to contact ZDV on another frequency. After checking in with the new controller, he gave us what we thought was a pilot's discretion descent to 12000 ft. Apparently, we misunderstood his descent clearance. 3 or 4 mins later, he asked us what our altitude was -- with an irritated tone in his voice. We told him. Obviously angry with us, he let us know exactly what he wanted. We apologized for the misunderstanding and he gave us a frequency change. Supplemental information from acn 285315: we should have confirmed the pilot's discretion. Center should have followed up on the descent request.

Original NASA ASRS Text

Title: COMMUTER ACFT MISINTERPRETS DSCNT CLRNC. CTLR UPSET.

Narrative: CRUISING AT FL250, ZDV GAVE US A PLT'S DISCRETION TO FL240. WE ACKNOWLEDGED AND REMAINED AT FL250. WE WERE THEN TOLD TO CONTACT ZDV ON ANOTHER FREQ. AFTER CHKING IN WITH THE NEW CTLR, HE GAVE US WHAT WE THOUGHT WAS A PLT'S DISCRETION DSCNT TO 12000 FT. APPARENTLY, WE MISUNDERSTOOD HIS DSCNT CLRNC. 3 OR 4 MINS LATER, HE ASKED US WHAT OUR ALT WAS -- WITH AN IRRITATED TONE IN HIS VOICE. WE TOLD HIM. OBVIOUSLY ANGRY WITH US, HE LET US KNOW EXACTLY WHAT HE WANTED. WE APOLOGIZED FOR THE MISUNDERSTANDING AND HE GAVE US A FREQ CHANGE. SUPPLEMENTAL INFO FROM ACN 285315: WE SHOULD HAVE CONFIRMED THE PLT'S DISCRETION. CTR SHOULD HAVE FOLLOWED UP ON THE DSCNT REQUEST.

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.