Air carrier medium large transport altitude deviation excursion from clearance altitude in response ...

Attributes
ACN	87351
Time
Date	198805
Day	Fri
Local Time Of Day	0601 To 1200
Place
Locale Reference	atc facility : fra
State Reference	CA
Altitude	msl bound lower : 19000 msl bound upper : 21000
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Controlling Facilities	artcc : zoa
Operator	common carrier : air carrier
Make Model Name	Medium Large Transport, Low Wing, 2 Turbojet Eng
Flight Phase	climbout : intermediate altitude
Route In Use	departure sid : sid
Flight Plan	IFR
Person 1
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 : 200 flight time total : 5000 flight time type : 1500
ASRS Report	87351
Person 2
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : atp pilot : commercial pilot : flight engineer pilot : instrument
Experience	flight time last 90 days : 200 flight time total : 14000 flight time type : 4000
ASRS Report	87347
Events
Anomaly	altitude deviation : excursion from assigned altitude non adherence : clearance
Independent Detector	other controllera
Resolutory Action	controller : issued new clearance
Consequence	Other
Supplementary
Primary Problem	Ambiguous
Air Traffic Incident	other

Narrative:

This is the second altitude deviation clearance miscom that I have been involved with in this sector of oak center. It is a very busy area with departures from sfo over linden and sfo arrs over modesto. We were flight uxxy, southbound to san diego. Another flight, uxyx was also on the same frequency 126.85. We were initially cleared to FL190, then to FL210. Both altitude clrncs were clearly read back to controller. As we leveled at FL210, oak center asked 'what was your last cleared altitude?' we responded 'FL210.' oak center stated that the clearance to FL210 was for company flight uxyx not uxxy. No incident or encounter with any other aircraft. It appears that the controllers of this oak sector are so busy that they miss incorrect clrncs, even when they are read back. A near miss or mid-air may be just a matter of time in this area. I do not believe that the flight numbers were too similar to contribute to this error. The sector is overloaded with civilian and military traffic. Supplemental information from acn 87347. Previous to this, we were unaware of company uxyx presence on the frequency.

Original NASA ASRS Text

Title: ACR MLG ALT DEVIATION EXCURSION FROM CLRNC ALT IN RESPONSE TO WRONG CALL SIGN.

Narrative: THIS IS THE SECOND ALT DEVIATION CLRNC MISCOM THAT I HAVE BEEN INVOLVED WITH IN THIS SECTOR OF OAK CENTER. IT IS A VERY BUSY AREA WITH DEPS FROM SFO OVER LINDEN AND SFO ARRS OVER MODESTO. WE WERE FLT UXXY, SBND TO SAN DIEGO. ANOTHER FLT, UXYX WAS ALSO ON THE SAME FREQ 126.85. WE WERE INITIALLY CLRED TO FL190, THEN TO FL210. BOTH ALT CLRNCS WERE CLRLY READ BACK TO CTLR. AS WE LEVELED AT FL210, OAK CENTER ASKED 'WHAT WAS YOUR LAST CLRED ALT?' WE RESPONDED 'FL210.' OAK CENTER STATED THAT THE CLRNC TO FL210 WAS FOR COMPANY FLT UXYX NOT UXXY. NO INCIDENT OR ENCOUNTER WITH ANY OTHER ACFT. IT APPEARS THAT THE CTLRS OF THIS OAK SECTOR ARE SO BUSY THAT THEY MISS INCORRECT CLRNCS, EVEN WHEN THEY ARE READ BACK. A NEAR MISS OR MID-AIR MAY BE JUST A MATTER OF TIME IN THIS AREA. I DO NOT BELIEVE THAT THE FLT NUMBERS WERE TOO SIMILAR TO CONTRIBUTE TO THIS ERROR. THE SECTOR IS OVERLOADED WITH CIVILIAN AND MIL TFC. SUPPLEMENTAL INFO FROM ACN 87347. PREVIOUS TO THIS, WE WERE UNAWARE OF COMPANY UXYX PRESENCE ON THE FREQ.

Data retrieved from NASA's ASRS site as of August 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.

Air carrier medium large transport altitude deviation excursion from clearance altitude in response to wrong call sign.