C177R pilot reported a malfunctioning alternator. He declared an emergency; conserved electrical pow...

Attributes
ACN	1106369
Time
Date	201308
Local Time Of Day	1801-2400
Place
Locale Reference	ZZZ.Airport
State Reference	US
Environment
Flight Conditions	VMC
Light	Dusk
Aircraft 1
Make Model Name	Cardinal 177/177RG
Operating Under FAR Part	Part 91
Flight Phase	Initial Approach
Route In Use	Vectors Visual Approach
Flight Plan	None
Component
Aircraft Component	AC Generator/Alternator
Person 1
Function	Pilot Flying Single Pilot
Qualification	Flight Crew Air Transport Pilot (ATP) Flight Crew Flight Engineer Flight Crew Multiengine Flight Crew Instrument Flight Crew Flight Instructor
Experience	Flight Crew Last 90 Days 165 Flight Crew Total 13500 Flight Crew Type 50
Events
Anomaly	Aircraft Equipment Problem Critical Inflight Event / Encounter Fuel Issue

Narrative:

[In flight] I encountered a steady discharge indication on my ammeter. The voltage indicated battery power only; even though the alternator did not drop off line. In order to preserve battery power I switched off all nonessential electrical equipment. My plan was to have enough battery power at our destination for landing gear and flap extension. My fuel log reflected enough fuel on board to destination and I navigated mostly by pilotage; with an occasional GPS bearing check. Once in a while I had to turn the power back on as the main gear tires were drooping into the airflow; causing a reduction in airspeed and increase of fuel burn.the main wheels are held up by hydraulic power and will over time sag with a pressure decrease in the hydraulic system. Due to this added drag my fuel estimate over the last checkpoint showed us behind on time and I was concerned about reaching the destination in daylight. Approaching the airport I advised approach of my alternator trouble and declared an emergency due to a potential fuel shortage. I requested a vector to the closest runway and landed without incident. After shutdown; I checked the fuel remaining and was relieved to find out that I had in fact the legal night fuel reserve left. I appreciate all the help given by ATC and arff.

Original NASA ASRS Text

Title: C177R pilot reported a malfunctioning alternator. He declared an emergency; conserved electrical power; and continued to destination.

Narrative: [In flight] I encountered a steady discharge indication on my ammeter. The voltage indicated battery power only; even though the alternator did not drop off line. In order to preserve battery power I switched off all nonessential electrical equipment. My plan was to have enough battery power at our destination for landing gear and flap extension. My fuel log reflected enough fuel on board to destination and I navigated mostly by pilotage; with an occasional GPS bearing check. Once in a while I had to turn the power back on as the main gear tires were drooping into the airflow; causing a reduction in airspeed and increase of fuel burn.The main wheels are held up by hydraulic power and will over time sag with a pressure decrease in the hydraulic system. Due to this added drag my fuel estimate over the last checkpoint showed us behind on time and I was concerned about reaching the destination in daylight. Approaching the airport I advised Approach of my alternator trouble and declared an emergency due to a potential fuel shortage. I requested a vector to the closest runway and landed without incident. After shutdown; I checked the fuel remaining and was relieved to find out that I had in fact the legal night fuel reserve left. I appreciate all the help given by ATC and ARFF.

Data retrieved from NASA's ASRS site as of July 2013 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.