Beech B55 pilot reported HSI failure in IMC on approach to psf.

Attributes
ACN	1224047
Time
Date	201411
Local Time Of Day	1201-1800
Place
Locale Reference	PSF.Airport
State Reference	MA
Environment
Flight Conditions	IMC
Light	Daylight
Aircraft 1
Make Model Name	Beechcraft Twin Piston Undifferentiated or Other Model
Operating Under FAR Part	Part 91
Flight Phase	Final Approach
Route In Use	Direct
Flight Plan	IFR
Component
Aircraft Component	Compass (HSI/ETC)
Person 1
Function	Pilot Flying Single Pilot
Qualification	Flight Crew Multiengine Flight Crew Instrument Flight Crew Air Transport Pilot (ATP)
Experience	Flight Crew Last 90 Days 20 Flight Crew Total 4042 Flight Crew Type 1358
Events
Anomaly	Aircraft Equipment Problem Critical Deviation - Procedural Clearance Deviation - Track / Heading All Types Inflight Event / Encounter Weather / Turbulence

Narrative:

While turning onto the final approach course for RNAV/GPS approach to RW26; my HSI (both heading indicator and CDI) began to fail; acting erratically. While still outside of the FAF; the HSI began to spin wildly out of control; also causing my mfd to continually change its display and course information; both of which were quite distracting. I had just entered IMC in a snow squall. While reported conditions at the airport were VFR; I was over the mountains to the east of psf and in solid IMC. I elected to discontinue the approach. I turned 180 degrees first to the north and then to the east to return to good VFR conditions that I had just left. I did this rather than risk continuing the approach; or remain in IMC to execute the published missed approach; not being able to fly an exact heading. Radar services had been terminated by albany approach; and when I was able to re-establish contract I informed them of the situation and asked for clearance to a higher altitude on a southeast heading; which they provided. I did not declare an emergency which perhaps I should have as I did not conform to the missed approach procedure. There were no conflicts.

Original NASA ASRS Text

Title: Beech B55 pilot reported HSI failure in IMC on approach to PSF.

Narrative: While turning onto the final approach course for RNAV/GPS Approach to RW26; my HSI (both Heading Indicator and CDI) began to fail; acting erratically. While still outside of the FAF; the HSI began to spin wildly out of control; also causing my MFD to continually change its display and course information; both of which were quite distracting. I had just entered IMC in a snow squall. While reported conditions at the airport were VFR; I was over the mountains to the east of PSF and in solid IMC. I elected to discontinue the approach. I turned 180 degrees first to the north and then to the east to return to good VFR conditions that I had just left. I did this rather than risk continuing the approach; or remain in IMC to execute the published Missed Approach; not being able to fly an exact heading. Radar services had been terminated by Albany approach; and when I was able to re-establish contract I informed them of the situation and asked for clearance to a higher altitude on a southeast heading; which they provided. I did not declare an emergency which perhaps I should have as I did not conform to the Missed Approach Procedure. There were no conflicts.

Data retrieved from NASA's ASRS site 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.