Narrative:

The WX was IFR with ceilings of 400 ft or less. Small aircraft X was cleared for takeoff from runway 23L. Over the upwind numbers small aircraft X declared he had a low plus voltage indication problem and needed to return. I, as local controller, asked small aircraft X if he was declaring an emergency. Small aircraft X was hesitant in saying no, then requested to return VFR. I asked small aircraft X if he could maintain ground contact and he said yes. I, as local controller, determined that a possible emergency did exist and offered small aircraft X left or right traffic. He entered left traffic. Small aircraft X was observed in the pattern and midfield he was instructed to extend downwind. He was #2 to follow traffic on final. He acknowledged. The traffic on final was an light transport. He was on a 1 mi final. At this time, it was determined that letting the light transport land would not delay the emergency aircraft. A few moments later, small aircraft X advised that he was turning base on his own accord. I told him negative, continue on the downwind, traffic was on final, I will call your base. Small aircraft X was returning to the downwind when the light transport reported that he had small aircraft X on TCASII, yet continued his normal approach and landed safely. Small aircraft X was told to turn base and then also landed safely. I believe this scenario would have never occurred if small aircraft X had not deviated from the downwind on his won accord. In the future, these types of incidents will probably continue to happen when pilots fail to comply with their last instruction.

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Original NASA ASRS Text

Title: 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.

Data retrieved from NASA's ASRS site as of July 2007 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.