Commuter BA31 return land.

Attributes
ACN	319009
Time
Date	199510
Day	Thu
Local Time Of Day	0601 To 1200
Place
Locale Reference	airport : fat
State Reference	CA
Altitude	msl bound lower : 7000 msl bound upper : 7000
Environment
Flight Conditions	VMC
Light	Dawn
Aircraft 1
Controlling Facilities	tracon : fat
Operator	common carrier : air carrier
Make Model Name	Jetstream 31
Operating Under FAR Part	Part 135
Flight Phase	climbout : intermediate altitude cruise other
Route In Use	departure other departure sid : sid enroute : on vectors
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : atp
Experience	flight time last 90 days : 140 flight time total : 2600 flight time type : 140
ASRS Report	319009
Person 2
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : atp
Events
Anomaly	aircraft equipment problem : critical non adherence : clearance other spatial deviation
Independent Detector	other controllera other flight crewa
Resolutory Action	none taken : unable other
Consequence	faa : reviewed incident with flight crew
Supplementary
Primary Problem	Aircraft
Air Traffic Incident	other

Narrative:

Climbing out after takeoff, the directional gyroscopes and the RMI's all started reading different headings. We tried everything to rectify the situation, but were unable to. We asked and received a no gyroscope steer back to fresno and landed. Nothing obvious was found with the system, but a stray invertor current was suspected as the culprit. Callback conversation with reporter revealed the following information: while on the fresno 5 departure (vector), the flight crew discovered that their heading information did not xchk. ATC recognized a problem at about the same time, and called and asked 'what's your heading?' reporter states that the problem was not apparent during runway alignment checks, but was not a critical failure because the flight crew was able to maintain orientation through outside visual reference and ATC assistance. An avionics person later informed the flight crew that the bizarre indications may have been a result of flux gate malfunction related to magnetic field disturbance, possibly sunspots. The malfunction could not be duplicated.

Original NASA ASRS Text

Title: COMMUTER BA31 RETURN LAND.

Narrative: CLBING OUT AFTER TKOF, THE DIRECTIONAL GYROSCOPES AND THE RMI'S ALL STARTED READING DIFFERENT HDGS. WE TRIED EVERYTHING TO RECTIFY THE SIT, BUT WERE UNABLE TO. WE ASKED AND RECEIVED A NO GYROSCOPE STEER BACK TO FRESNO AND LANDED. NOTHING OBVIOUS WAS FOUND WITH THE SYS, BUT A STRAY INVERTOR CURRENT WAS SUSPECTED AS THE CULPRIT. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: WHILE ON THE FRESNO 5 DEP (VECTOR), THE FLC DISCOVERED THAT THEIR HDG INFO DID NOT XCHK. ATC RECOGNIZED A PROB AT ABOUT THE SAME TIME, AND CALLED AND ASKED 'WHAT'S YOUR HDG?' RPTR STATES THAT THE PROB WAS NOT APPARENT DURING RWY ALIGNMENT CHKS, BUT WAS NOT A CRITICAL FAILURE BECAUSE THE FLC WAS ABLE TO MAINTAIN ORIENTATION THROUGH OUTSIDE VISUAL REF AND ATC ASSISTANCE. AN AVIONICS PERSON LATER INFORMED THE FLC THAT THE BIZARRE INDICATIONS MAY HAVE BEEN A RESULT OF FLUX GATE MALFUNCTION RELATED TO MAGNETIC FIELD DISTURBANCE, POSSIBLY SUNSPOTS. THE MALFUNCTION COULD NOT BE DUPLICATED.

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.