<< >> NASA ASRS Report 407939, July 1998

ARTCC controller evidently assigned FL240 to LR24 flight crew and does not hear incorrect readback of FL340. Controller takes action when conflict alert is activated, but is unable to maintain legal separation. Pilot asked to call facility.

Attributes
ACN	407939
Time
Date	199807
Day	Sat
Local Time Of Day	1201 To 1800
Place
Locale Reference	atc facility : ehf
State Reference	CA
Altitude	msl bound lower : 24000 msl bound upper : 25300
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Controlling Facilities	artcc : zla
Operator	general aviation : corporate
Make Model Name	Learjet 24
Operating Under FAR Part	Part 91
Flight Phase	climbout : intermediate altitude
Route In Use	departure other
Flight Plan	IFR
Aircraft 2
Operator	general aviation : corporate
Make Model Name	Challenger CL600
Operating Under FAR Part	Part 91
Navigation In Use	Other
Flight Plan	IFR
Person 1
Affiliation	Other
Function	flight crew : captain oversight : pic
Qualification	pilot : atp
Experience	flight time last 90 days : 70 flight time total : 5000 flight time type : 70
ASRS Report	407939
Person 2
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : instrument pilot : flight engineer pilot : commercial pilot : cfi pilot : atp
Experience	flight time last 90 days : 230 flight time total : 6500 flight time type : 1300
ASRS Report	408318
Events
Anomaly	altitude deviation : overshoot conflict : airborne less severe non adherence : clearance non adherence : required legal separation other anomaly other
Independent Detector	atc equipment other atc equipment : unspecified other controllera
Resolutory Action	controller : issued new clearance other
Consequence	faa : reviewed incident with flight crew
Miss Distance	horizontal : 23400 vertical : 200
Supplementary
Primary Problem	ATC Human Performance
Air Traffic Incident	Operational Error

Narrative:

On jul/sat/98, we were flying an LR24 from van nuys to coeur D'alene. At approximately XA00Z we were south of shafter VOR climbing when the controller issued a climb clearance to what we believed was 34000 ft. We both acknowledge and my copilot read back to controller 'FL340' to which the controller did not challenge or reply. As we were climbing through 25300 ft the controller then challenged our altitude and stated that we were cleared to FL240. My copilot responded by stating that we heard FL340, and read back FL340, without a controller challenge, and therefore believed we were climbing to that altitude. The controller then issued a descent clearance to FL240 and a left turn of 30 degrees. He later asked us to call. Supplemental information from acn 408318: we called and spoke with the supervisor who stated that we indeed read back FL340 and the controller did not respond.

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Original NASA ASRS Text

Title: ARTCC CTLR EVIDENTLY ASSIGNED FL240 TO LR24 FLC AND DOES NOT HEAR INCORRECT READBACK OF FL340. CTLR TAKES ACTION WHEN CONFLICT ALERT IS ACTIVATED, BUT IS UNABLE TO MAINTAIN LEGAL SEPARATION. PLT ASKED TO CALL FACILITY.

Narrative: ON JUL/SAT/98, WE WERE FLYING AN LR24 FROM VAN NUYS TO COEUR D'ALENE. AT APPROX XA00Z WE WERE S OF SHAFTER VOR CLBING WHEN THE CTLR ISSUED A CLB CLRNC TO WHAT WE BELIEVED WAS 34000 FT. WE BOTH ACKNOWLEDGE AND MY COPLT READ BACK TO CTLR 'FL340' TO WHICH THE CTLR DID NOT CHALLENGE OR REPLY. AS WE WERE CLBING THROUGH 25300 FT THE CTLR THEN CHALLENGED OUR ALT AND STATED THAT WE WERE CLRED TO FL240. MY COPLT RESPONDED BY STATING THAT WE HEARD FL340, AND READ BACK FL340, WITHOUT A CTLR CHALLENGE, AND THEREFORE BELIEVED WE WERE CLBING TO THAT ALT. THE CTLR THEN ISSUED A DSCNT CLRNC TO FL240 AND A L TURN OF 30 DEGS. HE LATER ASKED US TO CALL. SUPPLEMENTAL INFO FROM ACN 408318: WE CALLED AND SPOKE WITH THE SUPVR WHO STATED THAT WE INDEED READ BACK FL340 AND THE CTLR DID NOT RESPOND.

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.