Pilot of small transport following his stuck HSI took up erroneous heading.

Attributes
ACN	122692
Time
Date	198909
Day	Mon
Local Time Of Day	0601 To 1200
Place
Locale Reference	airport : msp
State Reference	MN
Altitude	msl bound lower : 8000 msl bound upper : 8000
Environment
Flight Conditions	IMC
Light	Daylight
Aircraft 1
Controlling Facilities	tracon : msp
Operator	general aviation : corporate
Make Model Name	Small Transport, Low Wing, 2 Recip Eng
Flight Phase	climbout : initial climbout : intermediate altitude cruise other
Route In Use	enroute : on vectors
Flight Plan	IFR
Person 1
Affiliation	Other
Function	flight crew : single pilot
Qualification	pilot : atp pilot : cfi pilot : instrument
Experience	flight time last 90 days : 200 flight time total : 14500 flight time type : 50
ASRS Report	122692
Person 2
Affiliation	government : faa
Function	controller : departure
Qualification	controller : radar
Events
Anomaly	aircraft equipment problem : less severe non adherence : clearance other spatial deviation
Independent Detector	other controllera other flight crewa
Resolutory Action	flight crew : overcame equipment problem flight crew : returned to intended course or assigned course
Consequence	Other
Supplementary
Primary Problem	Flight Crew Human Performance
Air Traffic Incident	Pilot Deviation

Narrative:

Upon departure out of the minneapolis area, I was instructed by ZMP to hold a 180 degree heading, and cleared direct des moines when able. I made a shallow left turn and rolled out on a 180 degree heading indicated on my horizontal situation indicator. What I didn't realize was that the magnetic flux value compass had temporarily jammed and stuck on heading 180 degrees, and as I was in a shallow left turn, the HSI was not moving. Since I was in IMC conditions, I could only check my heading with the magnetic compass and the copilot's dg. It took me about 3-4 mins. I was still turning left, and when I was able to ascertain I was in fact not holding heading, I found myself 90 degrees to my assigned heading. Having the magnetic flux valve temporarily stick caused my error. Reviewing my HSI manual, I found out that you will only get a heading flag on an HSI if you loose power to the HSI, and there is no flag that will appear if the magnetic flux valve is actually sending the HSI bad information. I would like to see a comparator flag of some type installed using 2 flux valves, and not just allowing one flux valve to be installed. That would solve problems like the one I encountered.

Original NASA ASRS Text

Title: PLT OF SMT FOLLOWING HIS STUCK HSI TOOK UP ERRONEOUS HEADING.

Narrative: UPON DEP OUT OF THE MINNEAPOLIS AREA, I WAS INSTRUCTED BY ZMP TO HOLD A 180 DEG HDG, AND CLRED DIRECT DES MOINES WHEN ABLE. I MADE A SHALLOW LEFT TURN AND ROLLED OUT ON A 180 DEG HDG INDICATED ON MY HORIZ SITUATION INDICATOR. WHAT I DIDN'T REALIZE WAS THAT THE MAGNETIC FLUX VALUE COMPASS HAD TEMPORARILY JAMMED AND STUCK ON HDG 180 DEGS, AND AS I WAS IN A SHALLOW LEFT TURN, THE HSI WAS NOT MOVING. SINCE I WAS IN IMC CONDITIONS, I COULD ONLY CHK MY HDG WITH THE MAGNETIC COMPASS AND THE COPLT'S DG. IT TOOK ME ABOUT 3-4 MINS. I WAS STILL TURNING LEFT, AND WHEN I WAS ABLE TO ASCERTAIN I WAS IN FACT NOT HOLDING HDG, I FOUND MYSELF 90 DEGS TO MY ASSIGNED HDG. HAVING THE MAGNETIC FLUX VALVE TEMPORARILY STICK CAUSED MY ERROR. REVIEWING MY HSI MANUAL, I FOUND OUT THAT YOU WILL ONLY GET A HDG FLAG ON AN HSI IF YOU LOOSE PWR TO THE HSI, AND THERE IS NO FLAG THAT WILL APPEAR IF THE MAGNETIC FLUX VALVE IS ACTUALLY SENDING THE HSI BAD INFO. I WOULD LIKE TO SEE A COMPARATOR FLAG OF SOME TYPE INSTALLED USING 2 FLUX VALVES, AND NOT JUST ALLOWING ONE FLUX VALVE TO BE INSTALLED. THAT WOULD SOLVE PROBS LIKE THE ONE I ENCOUNTERED.

Data retrieved from NASA's ASRS site as of August 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.