Mdt jet crew and another jet had less than legal separation in D10 class B airspace.

Attributes
ACN	536806
Time
Date	200201
Day	Sun
Local Time Of Day	0601 To 1200
Place
Locale Reference	airport : dal.airport
State Reference	TX
Altitude	msl bound lower : 2700 msl bound upper : 3000
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Controlling Facilities	tracon : d10.tracon
Operator	general aviation : corporate
Make Model Name	Medium Transport
Operating Under FAR Part	Part 91
Navigation In Use	other
Flight Plan	VFR
Aircraft 2
Controlling Facilities	tracon : d10.tracon
Make Model Name	Any Unknown or Unlisted Aircraft Manufacturer
Person 1
Affiliation	company : corporate
Function	flight crew : first officer
Qualification	pilot : multi engine pilot : instrument pilot : cfi pilot : atp
Experience	flight time last 90 days : 150 flight time total : 3200 flight time type : 150
ASRS Report	536806
Person 2
Affiliation	company : corporate
Function	flight crew : first officer oversight : pic
Events
Anomaly	conflict : airborne critical non adherence : far non adherence : published procedure other anomaly other
Independent Detector	other flight crewa other flight crewb
Resolutory Action	controller : issued alert controller : issued new clearance flight crew : took evasive action none taken : detected after the fact
Miss Distance	horizontal : 3000 vertical : 800
Supplementary
Problem Areas	Flight Crew Human Performance ATC Human Performance
Primary Problem	Ambiguous

Narrative:

On the approach phase, ATC cleared us to 2000 ft and said 'maintain 2000 ft till advised.' we left 3000 ft and started a turning descent for a left base to runway 13L at dal. I saw the jet coming from right to left, stopped my descent, added power and started back to altitude. The controller said we weren't supposed to descend, but by that time we were cleared to 2000 ft till advised. After the other jet passed us, he said since we were already in the descent to continue and switch over to dal tower, and then he said be advised of traffic.

Original NASA ASRS Text

Title: MDT JET CREW AND ANOTHER JET HAD LESS THAN LEGAL SEPARATION IN D10 CLASS B AIRSPACE.

Narrative: ON THE APCH PHASE, ATC CLRED US TO 2000 FT AND SAID 'MAINTAIN 2000 FT TILL ADVISED.' WE LEFT 3000 FT AND STARTED A TURNING DSCNT FOR A L BASE TO RWY 13L AT DAL. I SAW THE JET COMING FROM R TO L, STOPPED MY DSCNT, ADDED PWR AND STARTED BACK TO ALT. THE CTLR SAID WE WEREN'T SUPPOSED TO DSND, BUT BY THAT TIME WE WERE CLRED TO 2000 FT TILL ADVISED. AFTER THE OTHER JET PASSED US, HE SAID SINCE WE WERE ALREADY IN THE DSCNT TO CONTINUE AND SWITCH OVER TO DAL TWR, AND THEN HE SAID BE ADVISED OF TFC.

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.