A flight instructor reports losing his HSI and navigation on approach when he extended the landing g...

Narrative:

While on final approach for ILS we had a complete electrical failure. We lost HSI; loc; glideslope; navs; coms; transponder; rpm gauge; everything. It was VMC when the failure happened and we were about to descend into an overcast layer around 800 ft MSL without any ground reference. Per ATC approach instruction; upon going missed we climbed to 2000 ft MSL and flew runway heading with our magnetic compass. We maintained 2000 ft to maintain VFR due to layers above and beneath us. After running through all of the relative checklist with no changes; I decided to fly to an uncontrolled airport to land after exiting the airspace. While performing an emergency gear extension; we regained total electrical power. I determined that the failure was related to the gear switch. After putting the gear down on the approach is when our HSI and navs failed. When we went missed and picked the gear up; we lost all electrical power before I could advise tower of the situation. I attempted to transmit our condition and situation just in case they could hear us. We could not squawk 7600 due to the failure. After lowering the gear for the emergency gear extension and immediately recovering electrical power is when I realized it must be related to an electrical issue with the gear switch. After regaining power I contacted ATC approach on 121.1 and let them know what happened. After we landed; I called tower and informed them of the problem as well.

Original NASA ASRS Text

Title: A Flight Instructor reports losing his HSI and navigation on approach when he extended the landing gear on their Piper PA-44 Seminole aircraft. Due to the missed approach; he retracted the gear and then lost all electrical power and indications; except for the magnetic compass and vacuum gauges.

Narrative: While on final approach for ILS we had a complete electrical failure. We lost HSI; Loc; glideslope; Navs; coms; transponder; rpm gauge; everything. It was VMC when the failure happened and we were about to descend into an overcast layer around 800 FT MSL without any ground reference. Per ATC Approach instruction; upon going missed we climbed to 2000 FT MSL and flew runway heading with our magnetic compass. We maintained 2000 FT to maintain VFR due to layers above and beneath us. After running through all of the relative checklist with no changes; I decided to fly to an uncontrolled airport to land after exiting the airspace. While performing an emergency gear extension; we regained total electrical power. I determined that the failure was related to the gear switch. After putting the gear down on the approach is when our HSI and NAVs failed. When we went missed and picked the gear up; we lost all electrical power before I could advise Tower of the situation. I attempted to transmit our condition and situation just in case they could hear us. We could not squawk 7600 due to the failure. After lowering the gear for the emergency gear extension and immediately recovering electrical power is when I realized it must be related to an electrical issue with the gear switch. After regaining power I contacted ATC approach on 121.1 and let them know what happened. After we landed; I called Tower and informed them of the problem as well.

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	1232193
Time
Date	201501
Local Time Of Day	0601-1200
Place
Locale Reference	ZZZ.Airport
State Reference	US
Environment
Flight Conditions	Mixed
Light	Daylight
Aircraft 1
Make Model Name	PA-44 Seminole/Turbo Seminole
Operating Under FAR Part	Part 91
Flight Phase	Final Approach
Route In Use	None
Flight Plan	IFR
Component
Aircraft Component	Electrical Power
Person 1
Function	Instructor
Qualification	Flight Crew Multiengine Flight Crew Flight Instructor Flight Crew Commercial Flight Crew Instrument
Experience	Flight Crew Last 90 Days 100 Flight Crew Total 700 Flight Crew Type 200
Events
Anomaly	Aircraft Equipment Problem Critical Flight Deck / Cabin / Aircraft Event Other / Unknown Inflight Event / Encounter Other / Unknown

A flight instructor reports losing his HSI and navigation on approach when he extended the landing gear on their piper PA-44 seminole aircraft. Due to the missed approach; he retracted the gear and then lost all electrical power and indications; except for the magnetic compass and vacuum gauges.