Narrative:

On mar/tue/02 morning flight, I had a minor autoplt problem: over correction of pitch in altitude hold mode. The autoplt continued to work in other control axes and in other operational modes. I reported this to company maintenance, and they elected to defer it for a couple of days until the aircraft could be worked on in ZZZ1. They called company (local FBO) maintenance in ZZZ and asked them to execute the deferral. I showed up for my (nighttime) departure from ZZZ for ZZZ2 that evening and noted the log entry and the presence of a ty-rap on the circuit breaker panel. It was not until I was airborne and en route to alb, in really nasty IFR conditions, that I discovered that the company X mechanic had pulled and ty-rapped the wrong circuit breaker, and in so doing had disabled my only altitude encoder, in such a way that I was not able to correct the error in-flight (I had no tool available capable of cutting a ty-rap). The aircraft is equipped with dual xponders for redundancy, but they both share a single encoder, or at least, a single encoder circuit breaker. The up-side was that the autoplt was therefore still enabled, and while setting up my approach to ZZZ2 in very nasty conditions, I elected to use its fully svcable heading mode to help keep the airplane right-side up for a few moments while I fished out an approach plate. (Company freight operations are single pilot. 2 points here about the ty-rap practice: 1) a mechanic's error in using it can become a new and unrelated safety hazard, and 2) even when done properly, when it's done in a way that the pilot cannot override even in case of an emergency, it seriously reduced the pilot's available options. It's not hard to imagine scenarios in which the presence of one of those ty-raps, either rightly or wrongly placed, could become a contributing factor to an accident. Since their positive contribution to safety seems to be not significant enough to override that consideration, I would like to take the opportunity to recommend that the ty-rap practice be dropped. The alternative would be for the deferring mechanic simply to pull the circuit breaker and notify the pilot in his deferral write-up that it is pulled, and what the reason for pulling it is. Callback conversation with reporter revealed the following information: the reporter stated the autoplt was deferred and per the MEL a circuit breaker was required to be pulled and locked out. The reporter said using this procedure will render inoperative the electrical pitch trim and this was pointed out to the local FSDO recently. The reporter stated the major problem was the local FBO technician who carried out the deferral transaction supposedly using the facility MEL. The reporter said the wrong circuit breaker was pulled and locked out with electrical wiring ty-wraps. The reporter stated that after discovering the wrong breaker was pulled and the altitude encoding panel was inoperative there was no tooling to remove the ty-wraps.

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Original NASA ASRS Text

Title: A C208B WAS DISPATCHED IN NON COMPLIANCE WITH THE AUTOPLT DEFERRED PER THE MEL BUT THE WRONG CIRCUIT BREAKER WAS LOCKED OUT IMPROPERLY.

Narrative: ON MAR/TUE/02 MORNING FLT, I HAD A MINOR AUTOPLT PROB: OVER CORRECTION OF PITCH IN ALT HOLD MODE. THE AUTOPLT CONTINUED TO WORK IN OTHER CTL AXES AND IN OTHER OPERATIONAL MODES. I RPTED THIS TO COMPANY MAINT, AND THEY ELECTED TO DEFER IT FOR A COUPLE OF DAYS UNTIL THE ACFT COULD BE WORKED ON IN ZZZ1. THEY CALLED COMPANY (LCL FBO) MAINT IN ZZZ AND ASKED THEM TO EXECUTE THE DEFERRAL. I SHOWED UP FOR MY (NIGHTTIME) DEP FROM ZZZ FOR ZZZ2 THAT EVENING AND NOTED THE LOG ENTRY AND THE PRESENCE OF A TY-RAP ON THE CIRCUIT BREAKER PANEL. IT WAS NOT UNTIL I WAS AIRBORNE AND ENRTE TO ALB, IN REALLY NASTY IFR CONDITIONS, THAT I DISCOVERED THAT THE COMPANY X MECH HAD PULLED AND TY-RAPPED THE WRONG CIRCUIT BREAKER, AND IN SO DOING HAD DISABLED MY ONLY ALT ENCODER, IN SUCH A WAY THAT I WAS NOT ABLE TO CORRECT THE ERROR INFLT (I HAD NO TOOL AVAILABLE CAPABLE OF CUTTING A TY-RAP). THE ACFT IS EQUIPPED WITH DUAL XPONDERS FOR REDUNDANCY, BUT THEY BOTH SHARE A SINGLE ENCODER, OR AT LEAST, A SINGLE ENCODER CIRCUIT BREAKER. THE UP-SIDE WAS THAT THE AUTOPLT WAS THEREFORE STILL ENABLED, AND WHILE SETTING UP MY APCH TO ZZZ2 IN VERY NASTY CONDITIONS, I ELECTED TO USE ITS FULLY SVCABLE HDG MODE TO HELP KEEP THE AIRPLANE RIGHT-SIDE UP FOR A FEW MOMENTS WHILE I FISHED OUT AN APCH PLATE. (COMPANY FREIGHT OPS ARE SINGLE PLT. 2 POINTS HERE ABOUT THE TY-RAP PRACTICE: 1) A MECH'S ERROR IN USING IT CAN BECOME A NEW AND UNRELATED SAFETY HAZARD, AND 2) EVEN WHEN DONE PROPERLY, WHEN IT'S DONE IN A WAY THAT THE PLT CANNOT OVERRIDE EVEN IN CASE OF AN EMER, IT SERIOUSLY REDUCED THE PLT'S AVAILABLE OPTIONS. IT'S NOT HARD TO IMAGINE SCENARIOS IN WHICH THE PRESENCE OF ONE OF THOSE TY-RAPS, EITHER RIGHTLY OR WRONGLY PLACED, COULD BECOME A CONTRIBUTING FACTOR TO AN ACCIDENT. SINCE THEIR POSITIVE CONTRIBUTION TO SAFETY SEEMS TO BE NOT SIGNIFICANT ENOUGH TO OVERRIDE THAT CONSIDERATION, I WOULD LIKE TO TAKE THE OPPORTUNITY TO RECOMMEND THAT THE TY-RAP PRACTICE BE DROPPED. THE ALTERNATIVE WOULD BE FOR THE DEFERRING MECH SIMPLY TO PULL THE CIRCUIT BREAKER AND NOTIFY THE PLT IN HIS DEFERRAL WRITE-UP THAT IT IS PULLED, AND WHAT THE REASON FOR PULLING IT IS. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: THE RPTR STATED THE AUTOPLT WAS DEFERRED AND PER THE MEL A CIRCUIT BREAKER WAS REQUIRED TO BE PULLED AND LOCKED OUT. THE RPTR SAID USING THIS PROC WILL RENDER INOP THE ELECTRICAL PITCH TRIM AND THIS WAS POINTED OUT TO THE LCL FSDO RECENTLY. THE RPTR STATED THE MAJOR PROB WAS THE LCL FBO TECHNICIAN WHO CARRIED OUT THE DEFERRAL TRANSACTION SUPPOSEDLY USING THE FACILITY MEL. THE RPTR SAID THE WRONG CIRCUIT BREAKER WAS PULLED AND LOCKED OUT WITH ELECTRICAL WIRING TY-WRAPS. THE RPTR STATED THAT AFTER DISCOVERING THE WRONG BREAKER WAS PULLED AND THE ALT ENCODING PANEL WAS INOP THERE WAS NO TOOLING TO REMOVE THE TY-WRAPS.

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.