Narrative:

While cruising at 5000 ft MSL, first officer (me) switched to company frequency when 10 mins out (company policy). Normal altitude from lax to oxr is 4000 ft MSL. After switching from lax approach to burbank approach, I observed the captain reduce power (I was still on company frequency then ATIS). I flashed 4 fingers to the captain questioning if we had been cleared to descend to 4000 ft. No verbal communication took place. I thought I saw the captain nod in the affirmative, then switch the altitude selector to 4000 ft. We began our descent, then, after completing the company call and getting ATIS, I asked the captain if we were cleared to descend. He said we were given a speed restriction of 160 KTS. We continued descent. At 4500 ft burbank gave us an immediate climb to 5000 ft and right turn to 360 degree. A conflicting small aircraft was at 4000 ft. We climbed back to 5000 ft and reintercepted the localizer from the north. The rest of the flight was uneventful. This incident resulted from a breakdown in crew coordination. The first officer (myself) should have been concentrating on his own duties when off the active ATC frequency, combined with a very heavy workload (IMC with turbulence and lots of traffic, and an airborne time of 12 mins from lax to oxr). A desire to help the captain resulted in a very embarrassing and potentially very serious conflict.

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Original NASA ASRS Text

Title: COMMUTER ACFT MAKING DSCNT FOR APCH FLIES BELOW ASSIGNED ALT. CTLR GIVES VECTOR TO AVOID CONFLICT.

Narrative: WHILE CRUISING AT 5000 FT MSL, FO (ME) SWITCHED TO COMPANY FREQ WHEN 10 MINS OUT (COMPANY POLICY). NORMAL ALT FROM LAX TO OXR IS 4000 FT MSL. AFTER SWITCHING FROM LAX APCH TO BURBANK APCH, I OBSERVED THE CAPT REDUCE PWR (I WAS STILL ON COMPANY FREQ THEN ATIS). I FLASHED 4 FINGERS TO THE CAPT QUESTIONING IF WE HAD BEEN CLRED TO DSND TO 4000 FT. NO VERBAL COM TOOK PLACE. I THOUGHT I SAW THE CAPT NOD IN THE AFFIRMATIVE, THEN SWITCH THE ALT SELECTOR TO 4000 FT. WE BEGAN OUR DSCNT, THEN, AFTER COMPLETING THE COMPANY CALL AND GETTING ATIS, I ASKED THE CAPT IF WE WERE CLRED TO DSND. HE SAID WE WERE GIVEN A SPD RESTRICTION OF 160 KTS. WE CONTINUED DSCNT. AT 4500 FT BURBANK GAVE US AN IMMEDIATE CLB TO 5000 FT AND R TURN TO 360 DEG. A CONFLICTING SMA WAS AT 4000 FT. WE CLBED BACK TO 5000 FT AND REINTERCEPTED THE LOC FROM THE N. THE REST OF THE FLT WAS UNEVENTFUL. THIS INCIDENT RESULTED FROM A BREAKDOWN IN CREW COORD. THE FO (MYSELF) SHOULD HAVE BEEN CONCENTRATING ON HIS OWN DUTIES WHEN OFF THE ACTIVE ATC FREQ, COMBINED WITH A VERY HVY WORKLOAD (IMC WITH TURB AND LOTS OF TFC, AND AN AIRBORNE TIME OF 12 MINS FROM LAX TO OXR). A DESIRE TO HELP THE CAPT RESULTED IN A VERY EMBARRASSING AND POTENTIALLY VERY SERIOUS CONFLICT.

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.