An air carrier crew crosses olm VOR during arrival at sea 4000 ft below the charted altitude.

Attributes
ACN	584936
Time
Date	200306
Day	Wed
Local Time Of Day	1201 To 1800
Place
Locale Reference	intersection : arvad
State Reference	WA
Altitude	msl bound lower : 12000 msl bound upper : 17000
Environment
Flight Conditions	IMC
Light	Daylight
Aircraft 1
Controlling Facilities	artcc : zse.artcc tower : ojc.tower
Operator	common carrier : air carrier
Make Model Name	A320
Operating Under FAR Part	Part 121
Navigation In Use	other other vortac
Flight Phase	descent : intermediate altitude
Route In Use	arrival star : olm 4
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : cfi pilot : atp
Experience	flight time last 90 days : 250 flight time total : 11050 flight time type : 2000
ASRS Report	584936
Person 2
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : atp
Experience	flight time last 90 days : 80 flight time total : 12000 flight time type : 2000
ASRS Report	584831
Events
Anomaly	altitude deviation : overshoot altitude deviation : crossing restriction not met non adherence : clearance non adherence : published procedure
Independent Detector	other flight crewa other flight crewb
Resolutory Action	none taken : anomaly accepted none taken : detected after the fact
Supplementary
Problem Areas	Flight Crew Human Performance
Primary Problem	Flight Crew Human Performance
Air Traffic Incident	Pilot Deviation

Narrative:

ATC cleared us to descend via olm 4 arrival landing south. Crossing restr of 17000 ft and 280 KTS at olm VOR and 250 KTS at fourt intersection. During descent it appeared that we were above the required descent path. As is procedure the lowest charted altitude for the arrival was set in the altitude alerter (12000 ft). As we approached 20000 ft the descent path indicator went blank temporarily while the captain loaded the qnh at the field. When it returned, it showed us 430 ft above path, so I went to open descent at a higher speed to capture the path. However I also saw that we were now at 13000 ft approaching olm rather than the 17000 ft required. Contributing factors to this error were my fixation on descent path and failure to return to a managed descent path and the dimness of the navigation display which made it difficult to see that the color of the waypoint olm had changed to amber indicating an altitude error at arvad intersection.

Original NASA ASRS Text

Title: AN ACR CREW CROSSES OLM VOR DURING ARR AT SEA 4000 FT BELOW THE CHARTED ALT.

Narrative: ATC CLRED US TO DSND VIA OLM 4 ARR LNDG S. XING RESTR OF 17000 FT AND 280 KTS AT OLM VOR AND 250 KTS AT FOURT INTXN. DURING DSCNT IT APPEARED THAT WE WERE ABOVE THE REQUIRED DSCNT PATH. AS IS PROC THE LOWEST CHARTED ALT FOR THE ARR WAS SET IN THE ALT ALERTER (12000 FT). AS WE APCHED 20000 FT THE DSCNT PATH INDICATOR WENT BLANK TEMPORARILY WHILE THE CAPT LOADED THE QNH AT THE FIELD. WHEN IT RETURNED, IT SHOWED US 430 FT ABOVE PATH, SO I WENT TO OPEN DSCNT AT A HIGHER SPD TO CAPTURE THE PATH. HOWEVER I ALSO SAW THAT WE WERE NOW AT 13000 FT APCHING OLM RATHER THAN THE 17000 FT REQUIRED. CONTRIBUTING FACTORS TO THIS ERROR WERE MY FIXATION ON DSCNT PATH AND FAILURE TO RETURN TO A MANAGED DSCNT PATH AND THE DIMNESS OF THE NAV DISPLAY WHICH MADE IT DIFFICULT TO SEE THAT THE COLOR OF THE WAYPOINT OLM HAD CHANGED TO AMBER INDICATING AN ALT ERROR AT ARVAD INTXN.

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.