Partial instrument failure in IMC.

Attributes
ACN	289850
Time
Date	199411
Day	Mon
Local Time Of Day	1201 To 1800
Place
Locale Reference	atc facility : ffu
State Reference	UT
Altitude	msl bound lower : 14000 msl bound upper : 14000
Environment
Flight Conditions	IMC
Light	Daylight
Aircraft 1
Controlling Facilities	artcc : zlc tower : tpa
Operator	general aviation : personal
Make Model Name	PA-32 Cherokee Six/Lance/Saratoga
Operating Under FAR Part	Part 91
Flight Phase	climbout : intermediate altitude cruise other descent other
Flight Plan	IFR
Person 1
Affiliation	Other
Function	flight crew : single pilot
Qualification	pilot : instrument pilot : private
Experience	flight time last 90 days : 18 flight time total : 546 flight time type : 109
ASRS Report	289850
Person 2
Affiliation	government : faa
Function	controller : radar
Qualification	controller : radar
Events
Anomaly	aircraft equipment problem : critical altitude deviation : overshoot other spatial deviation
Independent Detector	aircraft equipment other aircraft equipment : unspecified
Resolutory Action	flight crew : exited adverse environment
Consequence	Other
Supplementary
Primary Problem	Aircraft
Air Traffic Incident	Pilot Deviation other

Narrative:

The alternator belt idler pulley failed, resulting in loss of electrical power. The failure was intermittent for possibly 15-20 mins with total alternator failure approximately 45 mins into flight. The problem occurred while being vectored after departure from slc airport. All readings were normal while being vectored initially southwest of slc and in climb up to 13000 ft. Approximately southeast of tooele, the HSI and backup VOR were showing discrepancies of up to 20 degrees. While trying to determine the cause of navigation discrepancies, I probably busted both altitude and airway limits. I suspected voltage problems, but when I glanced at the ammeter, it appeared to be normal, drawing about 30 amperes. It wasn't until the idler pulley failed completely, triggering my battery warning indicator, that I realized I had an electrical problem. At that point in time my HSI and VOR showed substantial discrepancies. I called ATC and requested vectors to the nearest airport with an FBO. All unnecessary electrical devices were shut off and I arrived at cedar city and landed without incident. No emergency was declared. On the human factor side, 1 pilot IFR was very difficult in hard IMC with conflicting instrument readings.

Original NASA ASRS Text

Title: PARTIAL INST FAILURE IN IMC.

Narrative: THE ALTERNATOR BELT IDLER PULLEY FAILED, RESULTING IN LOSS OF ELECTRICAL PWR. THE FAILURE WAS INTERMITTENT FOR POSSIBLY 15-20 MINS WITH TOTAL ALTERNATOR FAILURE APPROX 45 MINS INTO FLT. THE PROB OCCURRED WHILE BEING VECTORED AFTER DEP FROM SLC ARPT. ALL READINGS WERE NORMAL WHILE BEING VECTORED INITIALLY SW OF SLC AND IN CLB UP TO 13000 FT. APPROX SE OF TOOELE, THE HSI AND BACKUP VOR WERE SHOWING DISCREPANCIES OF UP TO 20 DEGS. WHILE TRYING TO DETERMINE THE CAUSE OF NAV DISCREPANCIES, I PROBABLY BUSTED BOTH ALT AND AIRWAY LIMITS. I SUSPECTED VOLTAGE PROBS, BUT WHEN I GLANCED AT THE AMMETER, IT APPEARED TO BE NORMAL, DRAWING ABOUT 30 AMPERES. IT WASN'T UNTIL THE IDLER PULLEY FAILED COMPLETELY, TRIGGERING MY BATTERY WARNING INDICATOR, THAT I REALIZED I HAD AN ELECTRICAL PROB. AT THAT POINT IN TIME MY HSI AND VOR SHOWED SUBSTANTIAL DISCREPANCIES. I CALLED ATC AND REQUESTED VECTORS TO THE NEAREST ARPT WITH AN FBO. ALL UNNECESSARY ELECTRICAL DEVICES WERE SHUT OFF AND I ARRIVED AT CEDAR CITY AND LANDED WITHOUT INCIDENT. NO EMER WAS DECLARED. ON THE HUMAN FACTOR SIDE, 1 PLT IFR WAS VERY DIFFICULT IN HARD IMC WITH CONFLICTING INST READINGS.

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.