Altitude deviation. Miscom clearance ATC flight crew.

Attributes
ACN	315170
Time
Date	199509
Day	Sun
Local Time Of Day	0601 To 1200
Place
Locale Reference	airport : lax
State Reference	CA
Altitude	msl bound lower : 2700 msl bound upper : 3000
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Controlling Facilities	tracon : lax
Operator	common carrier : air carrier
Make Model Name	Commercial Fixed Wing
Operating Under FAR Part	Part 121
Navigation In Use	Other Other
Flight Phase	descent : approach descent other
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : atp
Experience	flight time last 90 days : 110 flight time total : 5000 flight time type : 1100
ASRS Report	315170
Person 2
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : commercial pilot : cfi pilot : instrument pilot : flight engineer pilot : atp
Experience	flight time last 90 days : 156 flight time total : 12200 flight time type : 1300
ASRS Report	315068
Events
Anomaly	altitude deviation : excursion from assigned altitude non adherence : clearance other anomaly other
Independent Detector	other controllera other flight crewa
Resolutory Action	none taken : detected after the fact
Consequence	faa : reviewed incident with flight crew
Supplementary
Primary Problem	Flight Crew Human Performance
Air Traffic Incident	Pilot Deviation

Narrative:

While receiving vectors for a visual approach to runway 24R at lax, we misunderstood a clearance to 'maintain visual from that aircraft,' as a clearance for a visual approach. Subsequent vectors caused us to verify with controller that we were cleared for a visual approach. Controller told us we were not. At that point we had descended approximately 300 ft below our previously assigned altitude of 3000 ft. Frequency congestion and requirement to maintain visual contact with multiple aircraft (as directed by ATC) contributed. Supplemental information from acn 315068: lax is a very busy airport with lots of xmissions of pointing out traffic and clrncs for approachs. Maybe I misinterpreted a clearance for another aircraft being for us. Maybe approach's verbiage was misleading. Double-checking with first officer or ATC would have cleared up the confusion.

Original NASA ASRS Text

Title: ALTDEV. MISCOM CLRNC ATC FLC.

Narrative: WHILE RECEIVING VECTORS FOR A VISUAL APCH TO RWY 24R AT LAX, WE MISUNDERSTOOD A CLRNC TO 'MAINTAIN VISUAL FROM THAT ACFT,' AS A CLRNC FOR A VISUAL APCH. SUBSEQUENT VECTORS CAUSED US TO VERIFY WITH CTLR THAT WE WERE CLRED FOR A VISUAL APCH. CTLR TOLD US WE WERE NOT. AT THAT POINT WE HAD DSNDED APPROX 300 FT BELOW OUR PREVIOUSLY ASSIGNED ALT OF 3000 FT. FREQ CONGESTION AND REQUIREMENT TO MAINTAIN VISUAL CONTACT WITH MULTIPLE ACFT (AS DIRECTED BY ATC) CONTRIBUTED. SUPPLEMENTAL INFO FROM ACN 315068: LAX IS A VERY BUSY ARPT WITH LOTS OF XMISSIONS OF POINTING OUT TFC AND CLRNCS FOR APCHS. MAYBE I MISINTERPRETED A CLRNC FOR ANOTHER ACFT BEING FOR US. MAYBE APCH'S VERBIAGE WAS MISLEADING. DOUBLE-CHKING WITH FO OR ATC WOULD HAVE CLRED UP THE CONFUSION.

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.