Flight crew uses emergency authority to avoid penetrating volcanic ash cloud in the pacific.

Attributes
ACN	218742
Time
Date	199208
Day	Thu
Local Time Of Day	0001 To 0600
Place
Locale Reference	atc facility : oak
State Reference	CA
Altitude	msl bound lower : 35000 msl bound upper : 30000
Environment
Flight Conditions	VMC
Light	Night
Aircraft 1
Controlling Facilities	artcc : zhn artcc : zoa
Operator	common carrier : air carrier
Make Model Name	Widebody, Low Wing, 4 Turbojet Eng
Flight Phase	cruise other other
Route In Use	enroute : pacific enroute : other oceanic
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : atp
Experience	flight time last 90 days : 205 flight time total : 17789
ASRS Report	218742
Person 2
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : atp
Experience	flight time last 90 days : 200 flight time total : 10200 flight time type : 540
ASRS Report	218746
Events
Anomaly	altitude deviation : excursion from assigned altitude inflight encounter other non adherence : clearance other spatial deviation
Independent Detector	other flight crewa other other : unspecified
Resolutory Action	controller : issued new clearance flight crew : exited adverse environment flight crew : declared emergency flight crew : took evasive action
Consequence	Other
Supplementary
Primary Problem	Weather
Air Traffic Incident	Pilot Deviation

Narrative:

Volcanic ash plume forecast in area of our flight plan. Our flight X requested alternate route to avoid area. Numerous calls, unable to obtain. 100 mi prior to 44N 140W we visually sighted ash plume. Air carrier flight Y reported encountering ash at 390 and immediately descended to 350, exiting the ash somewhere around 370 and we requested immediate descent from 390 to 350. Honolulu radio advise standby. A later call to advise unable to authorize descent due an aircraft 9 min ahead at FL370. Approaching the plume (40 mi prior to 44N 140W) we deviated 15 mi north of track and then informed hnl radio and other aircraft we were descending to 350 to avoid ash plume. After approximately 70-80 mi clear of plume, we were cleared present position direct to zanng intersection to maintain 350.

Original NASA ASRS Text

Title: FLC USES EMER AUTHORITY TO AVOID PENETRATING VOLCANIC ASH CLOUD IN THE PACIFIC.

Narrative: VOLCANIC ASH PLUME FORECAST IN AREA OF OUR FLT PLAN. OUR FLT X REQUESTED ALTERNATE RTE TO AVOID AREA. NUMEROUS CALLS, UNABLE TO OBTAIN. 100 MI PRIOR TO 44N 140W WE VISUALLY SIGHTED ASH PLUME. ACR FLT Y RPTED ENCOUNTERING ASH AT 390 AND IMMEDIATELY DSNDED TO 350, EXITING THE ASH SOMEWHERE AROUND 370 AND WE REQUESTED IMMEDIATE DSCNT FROM 390 TO 350. HONOLULU RADIO ADVISE STANDBY. A LATER CALL TO ADVISE UNABLE TO AUTHORIZE DSCNT DUE AN ACFT 9 MIN AHEAD AT FL370. APCHING THE PLUME (40 MI PRIOR TO 44N 140W) WE DEVIATED 15 MI N OF TRACK AND THEN INFORMED HNL RADIO AND OTHER ACFT WE WERE DSNDING TO 350 TO AVOID ASH PLUME. AFTER APPROX 70-80 MI CLR OF PLUME, WE WERE CLRED PRESENT POS DIRECT TO ZANNG INTXN TO MAINTAIN 350.

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.