NYC07IA199 · Piper PA-32R-301T

After the pilot initiated a descent, smoke began to emanate from under the left side of the instrument panel of the Piper PA-32R-301T. The primary flight display (PFD) then "blanked out" and the 10-amp PFD circuit breaker opened. The pilot declared an emergency, diverted to the closest airport, and landed uneventfully. The airplane had accrued 526 total hours of operation. Examination revealed a Transient Voltage Suppressor (TVS) had failed. The following month, the National Transportation Safety Board was advised of another TVS failure on an airplane that had accrued 132.5 total hours of operation. Research conducted by Safety Board investigators indicated that failures of the same part number TVS were occurring on multiple makes and models of airplanes, some of which had only approximately 20 total hours of operation. Review of manufacturer-supplied information revealed that the maximum ratings and electrical characteristics were compatible with the affected electrical systems; however, testing of failed TVS revealed that the TVS displayed instances of "shorting," "reverse leakage," "breakdown voltage," and "excessive leakage," damaged dies with some separated from the base disc, holes in the center of the die and/or in the silicon near the center of the die, and molten solder internally and/or physical damage to the individual sub assembly. As a result, the manufacturer implemented high-temperature reverse bias testing of all TVSs prior to delivery to reduce the probability of failure and advised their customers to remove from service any TVS with the same date codes as the failed units. Additionally, the airplane manufacturers and the Federal Aviation Administration took corrective actions to remove and replace faulty TVSs.

Verbatim NTSB analysis and probable cause from the NTSB dataset