A C-150 electrical system failed during a practice instrument approach to a class D airport. Without...

Narrative:

While being vectored for a practice instrument approach I encountered an electrical issue that affected both nav and comm radios. Next ATC notified me transponder was not broadcasting altitude. Controller handed me off to the tower controller. The tower controller advised transponder was not broadcasting altitude and nav being used for approach showed 'off'. I cancelled approach and tower advised not to descend below altitude of 2000' MSL. I was checking fuse and recycled nav/com. The nav/com being used to speak to tower was still operational. As tower approved descent to an altitude to avoid class B. I lost contact with the tower on remaining radio.I am not sure if I changed transponder code while in class D airspace or as I entered into class G. My knobs on transponder are analog and I switched knobs to what I thought was 7600. I finished recycling both nav/coms and noticed I was quickly approaching class D airspace of the adjacent airport.a climb was initiated to get over 2800 feet to avoid class D; but in my estimation I would not make it over 2800 feet so I turned west to avoid class D. Next portion of flight was to a small airport which has parachute jumping so I overflew field to look for the distinctive colors of the aircraft on the ground so as not to cause harm to any parachutists.I started my approach while a call was made to the office at my home airport to advise of electrical problem; however; the answering machine came on.there indeed was no power as I could not get the electrically powered flaps to deploy and committed to a no flap landing.when the office manager gave me a number to call to speak to TRACON I explained the foregoing as I did not realize the transponder was reading 7500 rather than 7600 along with flying the aircraft being first priority. I will make it my practice to confirm transponder settings more often as time permits.

Original NASA ASRS Text

Title: A C-150 electrical system failed during a practice instrument approach to a Class D airport. Without radios the pilot navigated through and around Class B and D airspaces to return to the home airport.

Narrative: While being vectored for a practice instrument approach I encountered an electrical issue that affected both Nav and Comm radios. Next ATC notified me transponder was not broadcasting altitude. Controller handed me off to the tower controller. The tower controller advised transponder was not broadcasting altitude and Nav being used for approach showed 'off'. I cancelled approach and tower advised not to descend below altitude of 2000' MSL. I was checking fuse and recycled Nav/Com. The Nav/Com being used to speak to tower was still operational. As tower approved descent to an altitude to avoid Class B. I lost contact with the tower on remaining radio.I am not sure if I changed transponder code while in Class D airspace or as I entered into Class G. My knobs on transponder are analog and I switched knobs to what I thought was 7600. I finished recycling both Nav/coms and noticed I was quickly approaching Class D airspace of the adjacent airport.A climb was initiated to get over 2800 feet to avoid Class D; but in my estimation I would not make it over 2800 feet so I turned west to avoid Class D. Next portion of flight was to a small airport which has parachute jumping so I overflew field to look for the distinctive colors of the aircraft on the ground so as not to cause harm to any parachutists.I started my approach while a call was made to the office at my home airport to advise of electrical problem; however; the answering machine came on.There indeed was no power as I could not get the electrically powered flaps to deploy and committed to a no flap landing.When the office manager gave me a number to call to speak to TRACON I explained the foregoing as I did not realize the transponder was reading 7500 rather than 7600 along with flying the aircraft being first priority. I will make it my practice to confirm transponder settings more often as time permits.

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.

Attributes
ACN	1245411
Time
Date	201503
Local Time Of Day	0601-1200
Place
Locale Reference	ZZZ.Airport
State Reference	US
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Make Model Name	Cessna 150
Operating Under FAR Part	Part 91
Flight Phase	Cruise Descent Landing
Route In Use	Vectors
Flight Plan	None
Component
Aircraft Component	Electrical Power
Person 1
Function	Pilot Flying Single Pilot
Qualification	Flight Crew Instrument
Events
Anomaly	Aircraft Equipment Problem Less Severe Airspace Violation All Types Deviation - Procedural Published Material / Policy

A C-150 electrical system failed during a practice instrument approach to a class D airport. Without radios the pilot navigated through and around class B and D airspaces to return to the home airport.