Flight crew of medium large transport descended from assigned descent altitude in response to a TCAS...

Attributes
ACN	271624
Time
Date	199404
Day	Sun
Local Time Of Day	1201 To 1800
Place
Locale Reference	airport : ont
State Reference	CA
Altitude	msl bound lower : 12000 msl bound upper : 12000
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Controlling Facilities	tracon : ont
Operator	common carrier : air carrier
Make Model Name	Commercial Fixed Wing
Operating Under FAR Part	Part 121
Flight Phase	descent other
Flight Plan	IFR
Aircraft 2
Operator	common carrier : air carrier
Make Model Name	DC-9 Undifferentiated or Other Model
Operating Under FAR Part	Part 121
Flight Phase	descent other
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : commercial pilot : instrument
Experience	flight time last 90 days : 200 flight time total : 5000
ASRS Report	271624
Person 2
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : atp
Supplementary
Primary Problem	Flight Crew Human Performance
Air Traffic Incident	Pilot Deviation

Narrative:

On approach into ontario we were cleared for visual approach following an (air carrier Y) plane which was in sight. I declined the clearance as we were about to enter broken layer of clouds at 12000 ft MSL. About 30 seconds after entering clouds, our TCASII gave us a TA followed by a descend command RA. The TCASII screen showed traffic in front and behind us and we initiated a descent. ATC frequency was congested and about 15 seconds passed before able to transmit. Due to continued RA I declared an emergency, however ATC was unable to understand due to TCASII noise level. I was unable to communicate with captain, also because of the loudness of TCASII alert. We then broke out of the clouds, the alert ceased, and we saw the airport and asked for a visual approach. We were cleared for a visual approach to 26R and canceled our attempt for declaring an emergency. When we talked to ATC on the phone afterwards, she stated that TCASII alerts were 'normal' for that sector. In my opinion traffic congestion and radio congestion is a problem in the ontario area. The loudness of our TCASII alert added to the confusion.

Original NASA ASRS Text

Title: FLC OF MLG DSNDED FROM ASSIGNED DSCNT ALT IN RESPONSE TO A TCASII RA AND MOMENTARILY DECLARED AN EMER.

Narrative: ON APCH INTO ONTARIO WE WERE CLRED FOR VISUAL APCH FOLLOWING AN (ACR Y) PLANE WHICH WAS IN SIGHT. I DECLINED THE CLRNC AS WE WERE ABOUT TO ENTER BROKEN LAYER OF CLOUDS AT 12000 FT MSL. ABOUT 30 SECONDS AFTER ENTERING CLOUDS, OUR TCASII GAVE US A TA FOLLOWED BY A DSND COMMAND RA. THE TCASII SCREEN SHOWED TFC IN FRONT AND BEHIND US AND WE INITIATED A DSCNT. ATC FREQ WAS CONGESTED AND ABOUT 15 SECONDS PASSED BEFORE ABLE TO XMIT. DUE TO CONTINUED RA I DECLARED AN EMER, HOWEVER ATC WAS UNABLE TO UNDERSTAND DUE TO TCASII NOISE LEVEL. I WAS UNABLE TO COMMUNICATE WITH CAPT, ALSO BECAUSE OF THE LOUDNESS OF TCASII ALERT. WE THEN BROKE OUT OF THE CLOUDS, THE ALERT CEASED, AND WE SAW THE ARPT AND ASKED FOR A VISUAL APCH. WE WERE CLRED FOR A VISUAL APCH TO 26R AND CANCELED OUR ATTEMPT FOR DECLARING AN EMER. WHEN WE TALKED TO ATC ON THE PHONE AFTERWARDS, SHE STATED THAT TCASII ALERTS WERE 'NORMAL' FOR THAT SECTOR. IN MY OPINION TFC CONGESTION AND RADIO CONGESTION IS A PROB IN THE ONTARIO AREA. THE LOUDNESS OF OUR TCASII ALERT ADDED TO 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.

Flight crew of medium large transport descended from assigned descent altitude in response to a TCASII RA and momentarily declared an emergency.