ACFT ELECTRICAL FAILURE LED TO A RETURN LAND.

Narrative

PROGRESSIVE ELECTRICAL FAILURE RESULTING IN TOTAL ELECTRICAL LOSS. I AGREED TO ACT AS CFI/II TO PLT OF UNFAMILIAR ACFT. NEITHER OF US PAID SUFFICIENT ATTN TO AMMETER UNTIL I STARTED SUSPECTING ELECTRICAL PROB; THEN NOTED SMALL AMMETER DISCHARGE. INDICATORS OF ELECTRICAL PROB: UNABLE TO RECEIVE VOR IDENT AND VOICE FOR OTT VOR (20 MI DISTANT) AT 5000 FT MSL; GS OF #1 VOR AND LOC OF #2 VOR FLICKERING IN SYNC WITH FLASHING BEACON. WHEN #1 VOR LOC NEEDLE SHOWED NAV FLAG; I 'DECLARED' ELECTRICAL FAILURE TO OTHER OCCUPANTS; DIRECTED PLT TO REMAIN VFR AND STOP CLB; SELECTED 7600 ON XPONDER; AND ATTEMPTED TO CALL BWI APCH. WHEN NO REPLY; I DIRECTED PLT TO TURN TOWARD BAY BRIDGE; POS OVER BAY BRIDGE; AND SPIRAL DOWN 500-1000 FPM. INTENT WAS TO MAINTAIN PREDICTABLE AND CONSISTENT IMAGE ON BWI APCH PRIMARY RADAR AND TO AVOID SHOCK-COOLING ENG WHILE REMAINING VFR. I DIRECTED BACK- SEATER (ALSO PLT) TO COMMUNICATE OUR INTENTIONS TO BWI APCH ON HAND-HELD RADIO. THIS WAS EFFICIENTLY PERFORMED. AT 2000 FT IN VFR WITH HOME-BASE EASTON IN SIGHT; PLT AGREED TO MY PROPOSAL THAT WE RETURN TO EASTON. UNEVENTFUL NORDO LNDG WAS COMPLETED AT ESN. LESSON: DON'T LAUNCH INTO IFR IN UNFAMILIAR ACFT UNTIL ALL SYS CHK OK!