<< >> NASA ASRS Report 399253, April 1998

Loss of separation between 2 B757's when reporter's aircraft was issued descent to an occupied altitude of FL240 while aircraft were in holding.

Attributes
ACN	399253
Time
Date	199804
Day	Tue
Local Time Of Day	1801 To 2400
Place
Locale Reference	atc facility : atl
State Reference	GA
Altitude	msl bound lower : 24600 msl bound upper : 25000
Environment
Flight Conditions	Mixed
Light	Dusk
Aircraft 1
Controlling Facilities	artcc : ztl
Operator	common carrier : air carrier
Make Model Name	B757 Undifferentiated or Other Model
Operating Under FAR Part	Part 121
Navigation In Use	Other Other
Flight Phase	descent other
Route In Use	arrival other arrival star : star
Flight Plan	IFR
Aircraft 2
Operator	common carrier : air carrier
Make Model Name	B757 Undifferentiated or Other Model
Operating Under FAR Part	Part 121
Navigation In Use	Other Other
Flight Phase	cruise other
Route In Use	arrival other
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : atp
Experience	flight time last 90 days : 100 flight time total : 17000 flight time type : 65
ASRS Report	399253
Person 2
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : instrument pilot : commercial
Events
Anomaly	conflict : airborne less severe non adherence : clearance non adherence : required legal separation
Independent Detector	other controllera
Resolutory Action	other
Consequence	Other
Miss Distance	horizontal : 26400 vertical : 400
Supplementary
Primary Problem	ATC Human Performance
Air Traffic Incident	Operational Error

Narrative:

In cruise at FL280, flight was cleared direct sinca fix to hold and to descend to FL240. As aircraft was descending through approximately FL245, ATC inquired if aircraft was proceeding to fix to hold at FL250. When crew responded the clearance was to hold at FL240, aircraft given a 90-100 degree turn to the right and climb instructions to climb back up to FL250. After aircraft established on new heading and climbing, ATC reclred aircraft back down to FL240, aircraft subsequently cleared on course for sinca 3 arrival. Suspect cause of problem was controller overload due to multiple holding instructions to multiple aircraft in a very short period of time (too many aircraft trying to get to the same place, atlanta, at the same time).

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Original NASA ASRS Text

Title: LOSS OF SEPARATION BTWN 2 B757'S WHEN RPTR'S ACFT WAS ISSUED DSCNT TO AN OCCUPIED ALT OF FL240 WHILE ACFT WERE IN HOLDING.

Narrative: IN CRUISE AT FL280, FLT WAS CLRED DIRECT SINCA FIX TO HOLD AND TO DSND TO FL240. AS ACFT WAS DSNDING THROUGH APPROX FL245, ATC INQUIRED IF ACFT WAS PROCEEDING TO FIX TO HOLD AT FL250. WHEN CREW RESPONDED THE CLRNC WAS TO HOLD AT FL240, ACFT GIVEN A 90-100 DEG TURN TO THE R AND CLB INSTRUCTIONS TO CLB BACK UP TO FL250. AFTER ACFT ESTABLISHED ON NEW HDG AND CLBING, ATC RECLRED ACFT BACK DOWN TO FL240, ACFT SUBSEQUENTLY CLRED ON COURSE FOR SINCA 3 ARR. SUSPECT CAUSE OF PROB WAS CTLR OVERLOAD DUE TO MULTIPLE HOLDING INSTRUCTIONS TO MULTIPLE ACFT IN A VERY SHORT PERIOD OF TIME (TOO MANY ACFT TRYING TO GET TO THE SAME PLACE, ATLANTA, AT THE SAME TIME).

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.