<< >> NASA ASRS Report 493845, November 2000

A DC9 descending to 10000 ft above a PA46 descending to 9000 ft overtakes the PA46 in descent resulting in a loss of separation.

Attributes
ACN	493845
Time
Date	200011
Day	Mon
Local Time Of Day	1201 To 1800
Place
Locale Reference	navaid : tvt.vortac
State Reference	OH
Altitude	msl bound lower : 9000 msl bound upper : 12400
Environment
Flight Conditions	IMC
Light	Daylight
Aircraft 1
Controlling Facilities	artcc : zid.artcc
Operator	common carrier : air carrier
Make Model Name	DC-9 Undifferentiated or Other Model
Operating Under FAR Part	Part 121
Navigation In Use	other vortac
Flight Phase	descent : vacating altitude
Flight Plan	IFR
Aircraft 2
Controlling Facilities	artcc : zid.artcc
Operator	general aviation : personal
Make Model Name	PA-46 Malibu
Operating Under FAR Part	Part 91
Navigation In Use	other vortac
Flight Phase	descent : vacating altitude
Flight Plan	IFR
Person 1
Affiliation	government : faa
Function	controller : radar
Qualification	controller : radar
Experience	controller radar : 16
ASRS Report	493845
Person 2
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : atp
Events
Anomaly	conflict : airborne less severe non adherence : published procedure
Independent Detector	aircraft equipment : tcas other controllera other flight crewa other flight crewb
Resolutory Action	none taken : insufficient time
Supplementary
Problem Areas	ATC Human Performance
Primary Problem	ATC Human Performance
Air Traffic Incident	Operational Error

Narrative:

Both aircraft were descending into cak. ZID/ZOB LOA requires that propellers cross the common center boundary at 9000 ft for propellers/single engine and 10000 ft for jets. I was step descending the DC9 on top of the PA46. During this time period I noticed an 11000 ft untracked target in confliction with the DC9. At the time I noticed the 11000 ft traffic, the DC9 was at FL190 descending to 13000 ft, and the PA46 was descending from 12400 ft to cross 10 mi northeast of tvt at 9000 ft. I continued to monitor the situation and made the decision to cross the DC9 10 mi northeast of tvt at 10000 ft. I felt that I had no other choice since cak was so close to the boundary to get the DC9 below the 11000 ft intruder. The PA46 shallowed his descent rate at 10500 ft and the DC9 must have increased his and separation was lost.

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Original NASA ASRS Text

Title: A DC9 DSNDING TO 10000 FT ABOVE A PA46 DSNDING TO 9000 FT OVERTAKES THE PA46 IN DSCNT RESULTING IN A LOSS OF SEPARATION.

Narrative: BOTH ACFT WERE DSNDING INTO CAK. ZID/ZOB LOA REQUIRES THAT PROPS CROSS THE COMMON CTR BOUNDARY AT 9000 FT FOR PROPS/SINGLE ENG AND 10000 FT FOR JETS. I WAS STEP DSNDING THE DC9 ON TOP OF THE PA46. DURING THIS TIME PERIOD I NOTICED AN 11000 FT UNTRACKED TARGET IN CONFLICTION WITH THE DC9. AT THE TIME I NOTICED THE 11000 FT TFC, THE DC9 WAS AT FL190 DSNDING TO 13000 FT, AND THE PA46 WAS DSNDING FROM 12400 FT TO CROSS 10 MI NE OF TVT AT 9000 FT. I CONTINUED TO MONITOR THE SIT AND MADE THE DECISION TO CROSS THE DC9 10 MI NE OF TVT AT 10000 FT. I FELT THAT I HAD NO OTHER CHOICE SINCE CAK WAS SO CLOSE TO THE BOUNDARY TO GET THE DC9 BELOW THE 11000 FT INTRUDER. THE PA46 SHALLOWED HIS DSCNT RATE AT 10500 FT AND THE DC9 MUST HAVE INCREASED HIS AND SEPARATION WAS LOST.

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.