Air carrier X unauthorized descent from assigned altitude. Pilot deviation.

Attributes
ACN	171992
Time
Date	199102
Day	Thu
Local Time Of Day	1801 To 2400
Place
Locale Reference	atc facility : ape
State Reference	OH
Altitude	msl bound lower : 25500 msl bound upper : 26000
Environment
Flight Conditions	VMC
Light	Night
Aircraft 1
Controlling Facilities	artcc : zid tower : cvg
Operator	common carrier : air carrier
Make Model Name	Medium Large Transport, Low Wing, 2 Turbojet Eng
Navigation In Use	Other Other
Flight Phase	cruise other descent other
Route In Use	enroute : direct
Flight Plan	IFR
Aircraft 2
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	government : faa
Function	controller : radar
Qualification	controller : radar
Experience	controller military : 4 controller non radar : 3 controller radar : 1
ASRS Report	171992
Person 2
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : atp
Events
Anomaly	altitude deviation : excursion from assigned altitude conflict : airborne less severe non adherence : clearance non adherence : far other anomaly other
Independent Detector	other controllera
Resolutory Action	flight crew : returned to intended course or assigned course
Consequence	faa : reviewed incident with flight crew
Miss Distance	horizontal : 0 vertical : 1500
Supplementary
Primary Problem	Flight Crew Human Performance
Air Traffic Incident	Pilot Deviation

Narrative:

I was working appleton high radar position. I had air carrier X just leveling from a climb off pit and air carrier Y descending into pit. I called traffic to air carrier Y at 12 O'clock and 8 mi, level at FL260, and told him to maintain FL270, that I would have lower clearing traffic. I then called traffic to air carrier X at 12 O'clock and 3 mi, leveling at FL270, and told him to maintain FL260. Air carrier X didn't acknowledge the traffic call. By the time I had issued the traffic, air carrier X was descending through FL255. I asked air carrier X his altitude. He said he was out of FL255 for FL260. When he said that, I asked if he had descended because of TCAS. He said yes. I think TCAS is a good tool. When used properly, it can save lives. The thought of an aircraft descending in the positive control area west/O a clearance is not too comforting. To save my worries, I think that pilot should have to advise ATC of his intentions prior to taking action.

Original NASA ASRS Text

Title: ACR X UNAUTH DESCENT FROM ASSIGNED ALT. PLT DEVIATION.

Narrative: I WAS WORKING APPLETON HIGH RADAR POS. I HAD ACR X JUST LEVELING FROM A CLB OFF PIT AND ACR Y DSNDING INTO PIT. I CALLED TFC TO ACR Y AT 12 O'CLOCK AND 8 MI, LEVEL AT FL260, AND TOLD HIM TO MAINTAIN FL270, THAT I WOULD HAVE LOWER CLRING TFC. I THEN CALLED TFC TO ACR X AT 12 O'CLOCK AND 3 MI, LEVELING AT FL270, AND TOLD HIM TO MAINTAIN FL260. ACR X DIDN'T ACKNOWLEDGE THE TFC CALL. BY THE TIME I HAD ISSUED THE TFC, ACR X WAS DSNDING THROUGH FL255. I ASKED ACR X HIS ALT. HE SAID HE WAS OUT OF FL255 FOR FL260. WHEN HE SAID THAT, I ASKED IF HE HAD DSNDED BECAUSE OF TCAS. HE SAID YES. I THINK TCAS IS A GOOD TOOL. WHEN USED PROPERLY, IT CAN SAVE LIVES. THE THOUGHT OF AN ACFT DSNDING IN THE PCA W/O A CLRNC IS NOT TOO COMFORTING. TO SAVE MY WORRIES, I THINK THAT PLT SHOULD HAVE TO ADVISE ATC OF HIS INTENTIONS PRIOR TO TAKING ACTION.

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.