A320 first officer becomes confused during vectors to runway 19R at las; descending before cleared f...

Attributes
ACN	740637
Time
Date	200706
Local Time Of Day	1201 To 1800
Place
Locale Reference	airport : las.airport
State Reference	NV
Altitude	msl single value : 5000
Environment
Flight Conditions	VMC
Aircraft 1
Controlling Facilities	tracon : l30.tracon
Operator	common carrier : air carrier
Make Model Name	A320
Operating Under FAR Part	Part 121
Flight Phase	descent : approach cruise : level
Route In Use	arrival star : grnpa
Flight Plan	IFR
Aircraft 2
Controlling Facilities	tracon : l30.tracon
Operator	common carrier : air carrier
Make Model Name	Commercial Fixed Wing
Operating Under FAR Part	Part 121
Flight Phase	descent : approach
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : first officer
Experience	flight time last 90 days : 15 flight time total : 7500 flight time type : 2700
ASRS Report	740637
Person 2
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Experience	flight time last 90 days : 188 flight time total : 15000 flight time type : 1800
ASRS Report	740642
Events
Anomaly	non adherence : clearance other anomaly
Independent Detector	other controllera
Resolutory Action	controller : issued alert flight crew : executed go around flight crew : returned to assigned altitude
Supplementary
Problem Areas	Flight Crew Human Performance ATC Human Performance
Primary Problem	Flight Crew Human Performance

Narrative:

We were on a direct heading from grnpa arrival to las VOR. At 5100 ft crossing the hills northeast the airport; we were cleared to a heading of 270 degrees towards the stratosphere. At this point I heard approach tell us there was an air carrier on left downwind to runway 19L; and we were cleared visual. Somewhere in this; we were changed to runway 19R; which made sense to me with air carrier going to runway 19L. Crossing over the hills; as the captain was changing the box to runway 19R; I started my descent; and the altitude alert went off. I shallowed the descent; and asked him to 'roll it up;' and his response was we were not cleared down yet. Same time approach was asking us to climb back up due to air carrier traffic off the nose at 4000 ft. During this hairball is when I found out that air carrier was on a right downwind (west of the airport) and cleared to runway 19L. We were kept above and behind them for runway 19R. In a short time; the conflicts were resolved; we switched to tower; and were required to make a high energy descent to get on profile. Unable to stabilize the approach by 500 ft; I elected to go around. We were vectored for a right downwind base for runway 7R and uneventful landing. Tower/approach queried as to why the go around. We told them kept too high to allow traffic to cross under for landing. My lessons learned. I will obviously be more attentive to the clrncs in the future; especially when airports are running an irregular pattern that rarely happens. The communications were very busy; and this led to my misinterpretation. I am still unsure why las sent air carrier crossing under us when it would make more sense for them to have used runway 19R and us runway 19L. No crossing conflicts.

Original NASA ASRS Text

Title: A320 FO BECOMES CONFUSED DURING VECTORS TO RWY 19R AT LAS; DSNDING BEFORE CLRED FOR THE VISUAL AND NOT COMPREHENDING THAT TFC IS ON R DOWNWIND FOR RWY 19L. A LATE DSCNT CLRNC RESULTS IN AN UNSTABILIZED APCH AND A GAR.

Narrative: WE WERE ON A DIRECT HEADING FROM GRNPA ARR TO LAS VOR. AT 5100 FT CROSSING THE HILLS NE THE ARPT; WE WERE CLRED TO A HDG OF 270 DEGS TOWARDS THE STRATOSPHERE. AT THIS POINT I HEARD APCH TELL US THERE WAS AN ACR ON L DOWNWIND TO RWY 19L; AND WE WERE CLRED VISUAL. SOMEWHERE IN THIS; WE WERE CHANGED TO RWY 19R; WHICH MADE SENSE TO ME WITH ACR GOING TO RWY 19L. CROSSING OVER THE HILLS; AS THE CAPT WAS CHANGING THE BOX TO RWY 19R; I STARTED MY DESCENT; AND THE ALT ALERT WENT OFF. I SHALLOWED THE DESCENT; AND ASKED HIM TO 'ROLL IT UP;' AND HIS RESPONSE WAS WE WERE NOT CLRED DOWN YET. SAME TIME APCH WAS ASKING US TO CLB BACK UP DUE TO ACR TFC OFF THE NOSE AT 4000 FT. DURING THIS HAIRBALL IS WHEN I FOUND OUT THAT ACR WAS ON A R DOWNWIND (W OF THE ARPT) AND CLRED TO RWY 19L. WE WERE KEPT ABOVE AND BEHIND THEM FOR RWY 19R. IN A SHORT TIME; THE CONFLICTS WERE RESOLVED; WE SWITCHED TO TWR; AND WERE REQUIRED TO MAKE A HIGH ENERGY DESCENT TO GET ON PROFILE. UNABLE TO STABILIZE THE APCH BY 500 FT; I ELECTED TO GAR. WE WERE VECTORED FOR A R DOWNWIND BASE FOR RWY 7R AND UNEVENTFUL LNDG. TOWER/APCH QUERIED AS TO WHY THE GAR. WE TOLD THEM KEPT TOO HIGH TO ALLOW TFC TO CROSS UNDER FOR LNDG. MY LESSONS LEARNED. I WILL OBVIOUSLY BE MORE ATTENTIVE TO THE CLRNCS IN THE FUTURE; ESPECIALLY WHEN ARPTS ARE RUNNING AN IRREGULAR PATTERN THAT RARELY HAPPENS. THE COMS WERE VERY BUSY; AND THIS LED TO MY MISINTERPRETATION. I AM STILL UNSURE WHY LAS SENT ACR CROSSING UNDER US WHEN IT WOULD MAKE MORE SENSE FOR THEM TO HAVE USED RWY 19R AND US RWY 19L. NO CROSSING CONFLICTS.

Data retrieved from NASA's ASRS site as of January 2009 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.

A320 first officer becomes confused during vectors to runway 19R at las; descending before cleared for the visual and not comprehending that traffic is on right downwind for runway 19L. A late descent clearance results in an unstabilized approach and a go around.