Incident Description
After initiating a descent, the pilot of a Piper PA-32R-301T observed smoke emanating from under the left side of the instrument panel. Shortly thereafter, the primary flight display (PFD) blanked out and the 10-amp PFD circuit breaker opened. The pilot declared an emergency and diverted to the nearest airport, landing without further incident.
Aircraft and Component Details
The affected airplane had accumulated 526 total hours of operation. Examination of the aircraft identified a failed Transient Voltage Suppressor (TVS). The following month, the National Transportation Safety Board (NTSB) was informed of another TVS failure in an airplane with 132.5 total hours of operation. Further research by NTSB investigators indicated that failures of the same part number TVS were occurring across multiple makes and models of airplanes, some with as few as 20 total hours of operation.
Manufacturer Information and Corrective Actions
Review of manufacturer-supplied data showed that the maximum ratings and electrical characteristics of the TVS were compatible with the affected electrical systems. However, testing of failed TVS units revealed various anomalies, including instances of "shorting," "reverse leakage," "breakdown voltage," and "excessive leakage." Physical damage observed included damaged dies, some separated from the base disc, holes in the center of the die or in the silicon near the center of the die, and molten solder internally or physical damage to the individual subassembly.
In response, the manufacturer implemented high-temperature reverse bias testing of all TVSs prior to delivery to reduce the probability of failure. Additionally, they advised customers to remove from service any TVS with the same date codes as the failed units. Concurrently, the affected airplane manufacturers and the Federal Aviation Administration took corrective actions to remove and replace faulty TVSs.