Aircraft unable to maintain desired track in crosswind situation at altitude while on autoplt.

Attributes
ACN	143522
Time
Date	199004
Day	Tue
Local Time Of Day	1201 To 1800
Place
Locale Reference	atc facility : mod
State Reference	CA
Altitude	msl bound lower : 35000 msl bound upper : 35000
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Controlling Facilities	artcc : zoa
Operator	common carrier : air carrier
Make Model Name	Medium Large Transport, Low Wing, 2 Turbojet Eng
Flight Phase	cruise other
Route In Use	enroute : direct
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : atp
Experience	flight time last 90 days : 100 flight time total : 3000 flight time type : 500
ASRS Report	143522
Person 2
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : commercial pilot : instrument
Events
Anomaly	inflight encounter other non adherence : clearance other anomaly other other spatial deviation
Independent Detector	other controllera other flight crewa
Resolutory Action	controller : issued new clearance flight crew : returned to intended course or assigned course
Consequence	Other
Supplementary
Primary Problem	Flight Crew Human Performance
Air Traffic Incident	Pilot Deviation

Narrative:

Cleared proceed modesto VOR direct, by ATC (oak). Felt going directly across jet stream core the autoplt had as much as 45 degree correction. Proceeded until oak turned us directly toward modesto. Felt autoplt could not handle extreme crosswind velocities. Hand flew toward modesto. All indications looked accurate, but track over the ground appeared wrong (showing not so much drift as autoplt gave). If autoplt has limits they should be published. Drifted slightly north of original direct course.

Original NASA ASRS Text

Title: ACFT UNABLE TO MAINTAIN DESIRED TRACK IN CROSSWIND SITUATION AT ALT WHILE ON AUTOPLT.

Narrative: CLRED PROCEED MODESTO VOR DIRECT, BY ATC (OAK). FELT GOING DIRECTLY ACROSS JET STREAM CORE THE AUTOPLT HAD AS MUCH AS 45 DEG CORRECTION. PROCEEDED UNTIL OAK TURNED US DIRECTLY TOWARD MODESTO. FELT AUTOPLT COULD NOT HANDLE EXTREME XWIND VELOCITIES. HAND FLEW TOWARD MODESTO. ALL INDICATIONS LOOKED ACCURATE, BUT TRACK OVER THE GND APPEARED WRONG (SHOWING NOT SO MUCH DRIFT AS AUTOPLT GAVE). IF AUTOPLT HAS LIMITS THEY SHOULD BE PUBLISHED. DRIFTED SLIGHTLY N OF ORIGINAL DIRECT COURSE.

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.