Unregulated descent rate of a B717 causes conflict with descending MD88 under ZTL control.

Attributes
ACN	534450
Time
Date	200112
Day	Fri
Local Time Of Day	1201 To 1800
Place
Locale Reference	navaid : atl.vortac
State Reference	GA
Altitude	msl single value : 22000
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Controlling Facilities	artcc : ztl.artcc
Operator	common carrier : air carrier
Make Model Name	MD-80 Super 80
Operating Under FAR Part	Part 121
Navigation In Use	other other vortac
Flight Phase	descent : intermediate altitude
Route In Use	enroute : on vectors
Flight Plan	IFR
Aircraft 2
Controlling Facilities	artcc : ztl.artcc
Operator	common carrier : air carrier
Make Model Name	Stratolifter 717
Operating Under FAR Part	Part 121
Flight Phase	descent : intermediate altitude
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : instrument pilot : multi engine pilot : atp pilot : cfi pilot : commercial pilot : flight engineer
Experience	flight time last 90 days : 180 flight time total : 6700 flight time type : 1400
ASRS Report	534450
Person 2
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : atp pilot : flight engineer
Experience	flight time last 90 days : 150 flight time total : 10000 flight time type : 5000
ASRS Report	533781
Events
Anomaly	non adherence : clearance non adherence : required legal separation
Independent Detector	atc equipment other atc equipment : radar aircraft equipment : tcas other controllera other flight crewa other flight crewb
Resolutory Action	controller : issued new clearance controller : separated traffic
Consequence	faa : reviewed incident with flight crew
Miss Distance	horizontal : 700 vertical : 250
Supplementary
Problem Areas	ATC Human Performance
Primary Problem	ATC Human Performance
Air Traffic Incident	Operational Error

Narrative:

Descending into atl, macey arrival. Last clearance was to descend to 13000 ft. We were being vectored off arrival for spacing. Passing FL220, we got a TA on TCASII. It was a B717 at our 11 O'clock position and 1000 ft above descending. Since he was descending faster than us, we soon got an RA when he was about 700 ft vertically above us (still 2-3 NM ahead at our 1 O'clock position moving left to right). We had him in sight the entire event and did not need to make evasive maneuvers. We just increased our rate of descent. The B717 was instructed to level off and was asked what his last assigned altitude was. He responded 'FL220.' the only other comments made about the situation were by ATC when the B717 was instructed to change to the next frequency. The controller said 'thanks for your help.'

Original NASA ASRS Text

Title: UNREGULATED DSCNT RATE OF A B717 CAUSES CONFLICT WITH DSNDING MD88 UNDER ZTL CTL.

Narrative: DSNDING INTO ATL, MACEY ARR. LAST CLRNC WAS TO DSND TO 13000 FT. WE WERE BEING VECTORED OFF ARR FOR SPACING. PASSING FL220, WE GOT A TA ON TCASII. IT WAS A B717 AT OUR 11 O'CLOCK POS AND 1000 FT ABOVE DSNDING. SINCE HE WAS DSNDING FASTER THAN US, WE SOON GOT AN RA WHEN HE WAS ABOUT 700 FT VERTLY ABOVE US (STILL 2-3 NM AHEAD AT OUR 1 O'CLOCK POS MOVING L TO R). WE HAD HIM IN SIGHT THE ENTIRE EVENT AND DID NOT NEED TO MAKE EVASIVE MANEUVERS. WE JUST INCREASED OUR RATE OF DSCNT. THE B717 WAS INSTRUCTED TO LEVEL OFF AND WAS ASKED WHAT HIS LAST ASSIGNED ALT WAS. HE RESPONDED 'FL220.' THE ONLY OTHER COMMENTS MADE ABOUT THE SIT WERE BY ATC WHEN THE B717 WAS INSTRUCTED TO CHANGE TO THE NEXT FREQ. THE CTLR SAID 'THANKS FOR YOUR HELP.'

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.