Air carrier Y descended to 10,000' without clearance. Pilot deviation. Less than standard separation...

Attributes
ACN	127863
Time
Date	198911
Day	Mon
Local Time Of Day	1801 To 2400
Place
Locale Reference	atc facility : den
State Reference	CO
Altitude	msl bound lower : 10000 msl bound upper : 11000
Environment
Flight Conditions	VMC
Light	Night
Aircraft 1
Controlling Facilities	tracon : den
Operator	common carrier : air carrier
Make Model Name	Any Unknown or Unlisted Aircraft Manufacturer
Flight Phase	cruise other
Route In Use	departure other enroute : on vectors
Flight Plan	IFR
Aircraft 2
Operator	common carrier : air carrier
Make Model Name	Any Unknown or Unlisted Aircraft Manufacturer
Flight Phase	descent other
Route In Use	arrival other
Flight Plan	IFR
Person 1
Affiliation	government : faa
Function	controller : departure
Qualification	controller : radar
Experience	controller radar : 24
ASRS Report	127863
Person 2
Affiliation	government : faa
Function	controller : approach
Qualification	controller : radar
Events
Anomaly	altitude deviation : overshoot altitude deviation : excursion from assigned altitude conflict : airborne less severe non adherence : clearance non adherence : required legal separation
Independent Detector	other controllera
Resolutory Action	controller : issued new clearance other
Consequence	Other
Miss Distance	horizontal : 15000 vertical : 900
Supplementary
Primary Problem	Flight Crew Human Performance
Air Traffic Incident	Pilot Deviation

Narrative:

I was working departure radar. Air carrier X was on heading 170 to go out via south departure gate. I issued merging target traffic at 19 O'clock 5 mi 110 thousand. I then noticed that the target air carrier Y was descending below 110. I turned air carrier X H230 and advised the arrival radar that air carrier Y was below 110, he took immediate action to correct air carrier Y. They passed approximately 2 1/2 to 3 mi lateral less than one thousand vertical. Air carrier Y descended from 170 to 100 without a clearance.

Original NASA ASRS Text

Title: ACR Y DESCENDED TO 10,000' WITHOUT CLRNC. PLT DEVIATION. LESS THAN STANDARD SEPARATION.

Narrative: I WAS WORKING DEP RADAR. ACR X WAS ON HDG 170 TO GO OUT VIA S DEP GATE. I ISSUED MERGING TARGET TFC AT 19 O'CLOCK 5 MI 110 THOUSAND. I THEN NOTICED THAT THE TARGET ACR Y WAS DESCENDING BELOW 110. I TURNED ACR X H230 AND ADVISED THE ARR RADAR THAT ACR Y WAS BELOW 110, HE TOOK IMMEDIATE ACTION TO CORRECT ACR Y. THEY PASSED APPROX 2 1/2 TO 3 MI LATERAL LESS THAN ONE THOUSAND VERTICAL. ACR Y DESCENDED FROM 170 TO 100 WITHOUT A CLRNC.

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.