ARTCC radar controller amended an air carrier L1011 altitude to FL290 due to traffic, a B737 at FL310. The L1011 did not read back the amended altitude and less than standard separation occurred.

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Attributes
ACN	379382
Time
Date	199708
Day	Fri
Local Time Of Day	1201 To 1800
Place
Locale Reference	atc facility : lin
State Reference	CA
Altitude	msl bound lower : 29000 msl bound upper : 31000
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Controlling Facilities	artcc : zoa
Operator	common carrier : air carrier
Make Model Name	L-1011 Tri-Star All Series
Operating Under FAR Part	Part 121
Flight Phase	climbout : intermediate altitude
Flight Plan	IFR
Aircraft 2
Operator	common carrier : air carrier
Make Model Name	B737 Undifferentiated or Other Model
Operating Under FAR Part	Part 121
Flight Phase	cruise other
Flight Plan	IFR
Person 1
Affiliation	government : faa
Function	controller : radar
Qualification	controller : radar pilot : private
Experience	controller radar : 3 flight time total : 200
ASRS Report	379382
Person 2
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : atp
Events
Anomaly	conflict : airborne less severe non adherence : clearance non adherence : required legal separation
Independent Detector	atc equipment other atc equipment : unspecified other controllera
Resolutory Action	other
Consequence	Other
Miss Distance	horizontal : 9000 vertical : 1600
Supplementary
Primary Problem	ATC Human Performance
Air Traffic Incident	Operational Error

Narrative:

Air carrier X was originally climbed to FL330 but stopped at FL290 for air carrier Y traffic. Air carrier X did not read back amended altitude. Traffic was quoted 'at FL310' and air carrier X was told to 'expect higher in 2 mins.' pilot did not question his clearance to FL330 through traffic at FL310.

Original NASA ASRS Text

Title: ARTCC RADAR CTLR AMENDED AN ACR L1011 ALT TO FL290 DUE TO TFC, A B737 AT FL310. THE L1011 DID NOT READ BACK THE AMENDED ALT AND LTSS OCCURRED.

Narrative: ACR X WAS ORIGINALLY CLBED TO FL330 BUT STOPPED AT FL290 FOR ACR Y TFC. ACR X DID NOT READ BACK AMENDED ALT. TFC WAS QUOTED 'AT FL310' AND ACR X WAS TOLD TO 'EXPECT HIGHER IN 2 MINS.' PLT DID NOT QUESTION HIS CLRNC TO FL330 THROUGH TFC AT FL310.

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.