SMA X EQUIP PROB ELECTRICAL HAD LTSS FROM LTT ON IFR APCH.

Narrative

THE WX WAS IFR WITH CEILINGS OF 400 FT OR LESS. SMA X WAS CLRED FOR TKOF FROM RWY 23L. OVER THE UPWIND NUMBERS SMA X DECLARED HE HAD A LOW PLUS VOLTAGE INDICATION PROB AND NEEDED TO RETURN. I; AS LCL CTLR; ASKED SMA X IF HE WAS DECLARING AN EMER. SMA X WAS HESITANT IN SAYING NO; THEN REQUESTED TO RETURN VFR. I ASKED SMA X IF HE COULD MAINTAIN GND CONTACT AND HE SAID YES. I; AS LCL CTLR; DETERMINED THAT A POSSIBLE EMER DID EXIST AND OFFERED SMA X L OR R TFC. HE ENTERED L TFC. SMA X WAS OBSERVED IN THE PATTERN AND MIDFIELD HE WAS INSTRUCTED TO EXTEND DOWNWIND. HE WAS #2 TO FOLLOW TFC ON FINAL. HE ACKNOWLEDGED. THE TFC ON FINAL WAS AN LTT. HE WAS ON A 1 MI FINAL. AT THIS TIME; IT WAS DETERMINED THAT LETTING THE LTT LAND WOULD NOT DELAY THE EMER ACFT. A FEW MOMENTS LATER; SMA X ADVISED THAT HE WAS TURNING BASE ON HIS OWN ACCORD. I TOLD HIM NEGATIVE; CONTINUE ON THE DOWNWIND; TFC WAS ON FINAL; I WILL CALL YOUR BASE. SMA X WAS RETURNING TO THE DOWNWIND WHEN THE LTT RPTED THAT HE HAD SMA X ON TCASII; YET CONTINUED HIS NORMAL APCH AND LANDED SAFELY. SMA X WAS TOLD TO TURN BASE AND THEN ALSO LANDED SAFELY. I BELIEVE THIS SCENARIO WOULD HAVE NEVER OCCURRED IF SMA X HAD NOT DEVIATED FROM THE DOWNWIND ON HIS WON ACCORD. IN THE FUTURE; THESE TYPES OF INCIDENTS WILL PROBABLY CONTINUE TO HAPPEN WHEN PLTS FAIL TO COMPLY WITH THEIR LAST INSTRUCTION.