Narrative:

Cleared down to 5200 ft. Copilot hand flying. I was inside the cockpit momentarily to press PA button for 'prepare for landing' PA. Copilot declared that a mlt was coming right at us. He became concerned about which way to go (turn) to avoid hitting same. I checked altimeter which showed we were 200-300 ft below 5200. That is on third altimeter. Captain and first officer altimeter on QFE. Third altimeter usually shows high, slightly. So we might have been at 4900 MSL. Got an RA. Started climb -- clear of conflict. TCASII performed well. ATC didn't point out mlt as traffic or state that he was reason we were cleared to 5200 ft instead of lower. My guess is that mlt was being handled by norton AFB and was restr to some lower altitude and would not have climbed through our assigned altitude even though it appeared to be climbing. ATC questioned our altitude during event, before RA. Copilot disconnected autoplt without, me being aware of it. 'Autoplt off' is mandatory call. I'm not sure if it was made or not. It is not easily determined which way to go to get out of the way of a big jet filling your windscreen. Happy about TCASII.

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Original NASA ASRS Text

Title: AN ACR MLG HAD AN NMAC WITH AN MLT IN THE ONT ARSA ON APCH.

Narrative: CLRED DOWN TO 5200 FT. COPLT HAND FLYING. I WAS INSIDE THE COCKPIT MOMENTARILY TO PRESS PA BUTTON FOR 'PREPARE FOR LNDG' PA. COPLT DECLARED THAT A MLT WAS COMING RIGHT AT US. HE BECAME CONCERNED ABOUT WHICH WAY TO GO (TURN) TO AVOID HITTING SAME. I CHKED ALTIMETER WHICH SHOWED WE WERE 200-300 FT BELOW 5200. THAT IS ON THIRD ALTIMETER. CAPT AND FO ALTIMETER ON QFE. THIRD ALTIMETER USUALLY SHOWS HIGH, SLIGHTLY. SO WE MIGHT HAVE BEEN AT 4900 MSL. GOT AN RA. STARTED CLB -- CLR OF CONFLICT. TCASII PERFORMED WELL. ATC DIDN'T POINT OUT MLT AS TFC OR STATE THAT HE WAS REASON WE WERE CLRED TO 5200 FT INSTEAD OF LOWER. MY GUESS IS THAT MLT WAS BEING HANDLED BY NORTON AFB AND WAS RESTR TO SOME LOWER ALT AND WOULD NOT HAVE CLBED THROUGH OUR ASSIGNED ALT EVEN THOUGH IT APPEARED TO BE CLBING. ATC QUESTIONED OUR ALT DURING EVENT, BEFORE RA. COPLT DISCONNECTED AUTOPLT WITHOUT, ME BEING AWARE OF IT. 'AUTOPLT OFF' IS MANDATORY CALL. I'M NOT SURE IF IT WAS MADE OR NOT. IT IS NOT EASILY DETERMINED WHICH WAY TO GO TO GET OUT OF THE WAY OF A BIG JET FILLING YOUR WINDSCREEN. HAPPY ABOUT TCASII.

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.