<< >> NASA ASRS Report 447962, August 1999

Aircraft X was cleared to hold at 15000 ft. Aircraft Y was stopped at 16000 ft. Aircraft X was given a clearance to descend to 13000 ft and then told to disregard. Aircraft X acknowledged the clearance and reporter did not catch it resulting in a loss of standard separation.

Attributes
ACN	447962
Time
Date	199908
Day	Tue
Local Time Of Day	1801 To 2400
Place
Locale Reference	navaid : eno.vortac
State Reference	DE
Altitude	msl single value : 15000
Environment
Flight Conditions	VMC
Light	Night
Aircraft 1
Controlling Facilities	artcc : zdc.artcc
Operator	common carrier : air carrier
Make Model Name	B737-300
Operating Under FAR Part	Part 121
Flight Phase	descent : holding
Flight Plan	IFR
Aircraft 2
Controlling Facilities	artcc : zdc.artcc
Operator	common carrier : air carrier
Make Model Name	MD-80 Series (DC-9-80) Undifferentiated or Other Model
Operating Under FAR Part	Part 121
Flight Phase	descent : intermediate altitude
Flight Plan	IFR
Person 1
Affiliation	government : faa
Function	controller : radar
Qualification	controller : radar
Experience	controller radar : 7
ASRS Report	447962
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 : required legal separation other anomaly other
Independent Detector	atc equipment other atc equipment : error detection other controllera
Resolutory Action	none taken : detected after the fact
Consequence	faa : investigated
Miss Distance	horizontal : 15000 vertical : 100
Supplementary
Problem Areas	Flight Crew Human Performance ATC Human Performance
Primary Problem	ATC Human Performance
Air Traffic Incident	Operational Error

Narrative:

Aircraft X was at 15000 ft cleared to hold. Aircraft Y was descending to 16000 ft and unable to hold. I began to descend aircraft X to 13000 ft, but told him to disregard and maintain 15000 ft. Aircraft Y read back clearance to 15000 ft. I did not catch it.

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Original NASA ASRS Text

Title: ACFT X WAS CLRED TO HOLD AT 15000 FT. ACFT Y WAS STOPPED AT 16000 FT. ACFT X WAS GIVEN A CLRNC TO DSND TO 13000 FT AND THEN TOLD TO DISREGARD. ACFT X ACKNOWLEDGED THE CLRNC AND RPTR DID NOT CATCH IT RESULTING IN A LOSS OF STANDARD SEPARATION.

Narrative: ACFT X WAS AT 15000 FT CLRED TO HOLD. ACFT Y WAS DSNDING TO 16000 FT AND UNABLE TO HOLD. I BEGAN TO DSND ACFT X TO 13000 FT, BUT TOLD HIM TO DISREGARD AND MAINTAIN 15000 FT. ACFT Y READ BACK CLRNC TO 15000 FT. I DID NOT CATCH IT.

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.