Narrative:

Mccarran airport was landing and taking off using runways 1L and 7R. Approach control was using runway 1L for jet aircraft/acrs and runway 7R for smaller aircraft. I, in a C402 for air carrier X, was coming from the southeast. Approach had instructed me to report a mid-field right downwind for runway 7R. Once I was on the right downwind for runway 7R, approach instructed me to turn my base east of the final approach path for runway 1L. I misunderstood my instructions and thought ATC said to turn my base west of the final for runway 1L. In addition, my passenger were distracting me by blocking my view while I'm looking for traffic and constantly tapping my shoulder to ask questions. So I continued west past the final approach of runway 1L at about 4000 ft MSL. Before turning base, tower queried me on my actions, informed me of my error and told me to fly direct to runway 7R. Once on my modified final for runway 7R, tower reported traffic at my 2-3 O'clock position, a B737 on final for runway 1L. I had him in sight and continued my approach. I kept my approach high to avoid a conflict. Once on short final, I did see the B737 pass under me. The landing occurred without event. Ground control told me to copy down a phone number and call them on a land line. On the telephone, they told me of my error and that the B737 had to drop 200 ft of altitude on final because of a TCASII alert. An investigation is pending.

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Original NASA ASRS Text

Title: AIR TAXI PLT OF C402 HAS NMAC WITH B737 BOTH ON APCH TO XING RWYS. HE MISUNDERSTOOD HIS BASE TURN INSTRUCTIONS.

Narrative: MCCARRAN ARPT WAS LNDG AND TAKING OFF USING RWYS 1L AND 7R. APCH CTL WAS USING RWY 1L FOR JET ACFT/ACRS AND RWY 7R FOR SMALLER ACFT. I, IN A C402 FOR ACR X, WAS COMING FROM THE SE. APCH HAD INSTRUCTED ME TO RPT A MID-FIELD R DOWNWIND FOR RWY 7R. ONCE I WAS ON THE R DOWNWIND FOR RWY 7R, APCH INSTRUCTED ME TO TURN MY BASE E OF THE FINAL APCH PATH FOR RWY 1L. I MISUNDERSTOOD MY INSTRUCTIONS AND THOUGHT ATC SAID TO TURN MY BASE W OF THE FINAL FOR RWY 1L. IN ADDITION, MY PAX WERE DISTRACTING ME BY BLOCKING MY VIEW WHILE I'M LOOKING FOR TFC AND CONSTANTLY TAPPING MY SHOULDER TO ASK QUESTIONS. SO I CONTINUED W PAST THE FINAL APCH OF RWY 1L AT ABOUT 4000 FT MSL. BEFORE TURNING BASE, TWR QUERIED ME ON MY ACTIONS, INFORMED ME OF MY ERROR AND TOLD ME TO FLY DIRECT TO RWY 7R. ONCE ON MY MODIFIED FINAL FOR RWY 7R, TWR RPTED TFC AT MY 2-3 O'CLOCK POS, A B737 ON FINAL FOR RWY 1L. I HAD HIM IN SIGHT AND CONTINUED MY APCH. I KEPT MY APCH HIGH TO AVOID A CONFLICT. ONCE ON SHORT FINAL, I DID SEE THE B737 PASS UNDER ME. THE LNDG OCCURRED WITHOUT EVENT. GND CTL TOLD ME TO COPY DOWN A PHONE NUMBER AND CALL THEM ON A LAND LINE. ON THE TELEPHONE, THEY TOLD ME OF MY ERROR AND THAT THE B737 HAD TO DROP 200 FT OF ALT ON FINAL BECAUSE OF A TCASII ALERT. AN INVESTIGATION IS PENDING.

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.