Narrative:

Shortly after takeoff to do some practice approaches with my son/student; at about 1;000 ft AGL the alternator indicated a failure and was showing a discharge. We notified ATC and received vectors for the ILS. We turned off all electrical equipment except number 1 com. Radio; number 1 nav radio; and transponder until on 3 mile final. We attempted to reset the alternator to no avail. Although we did not declare an emergency per se; we did ask for prompt handling and advised ATC that we would fly a 270 heading until reaching VFR conditions in the event of total navigation and comm failure. ATC vectored us to final and asked if we needed any further emergency equipment. We refused. The approach commenced normally and we landed safely. In the flare just prior to touchdown; the alternator started indicating normally again. After landing and taxi in we did a little trouble shooting and found that the alternator would fail between 2;000 and 2;300 RPM on the ground during static run-up. We notified the flying clubs safety officer as well as the club's primary mechanic. We hangared the airplane; left signage in the airplane warning of the issue; and wrote up a maintenance squawk per club policy. All ATC facilities did an excellent job in handling our situation.

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Original NASA ASRS Text

Title: C172 pilot experiences an alternator failure shortly after takeoff in IMC and notifies ATC. Vectors are provided for an ILS approach and a safe landing ensues. On the ground it is discovered that the alternator faults between 2;000 and 2;300 RPM and is normal at other RPM's.

Narrative: Shortly after takeoff to do some practice approaches with my son/student; at about 1;000 FT AGL the alternator indicated a failure and was showing a discharge. We notified ATC and received vectors for the ILS. We turned off all electrical equipment except Number 1 Com. Radio; Number 1 Nav radio; and transponder until on 3 mile final. We attempted to reset the alternator to no avail. Although we did not declare an emergency per se; we did ask for prompt handling and advised ATC that we would fly a 270 heading until reaching VFR conditions in the event of total NAV and COMM failure. ATC vectored us to final and asked if we needed any further emergency equipment. We refused. The approach commenced normally and we landed safely. In the flare just prior to touchdown; the alternator started indicating normally again. After landing and taxi in we did a little trouble shooting and found that the alternator would fail between 2;000 and 2;300 RPM on the ground during static run-up. We notified the flying clubs Safety Officer as well as the club's primary mechanic. We hangared the airplane; left signage in the airplane warning of the issue; and wrote up a maintenance squawk per club policy. All ATC facilities did an excellent job in handling our situation.

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.