Squawk Box

October 2018 Issue




Unregulated

The following information is derived from the FAA’s Service Difficulty Reports and Aviation Maintenance Alerts.

Beechcraft Model 35-C33A Debonair
Shorted Voltage Regulator

Overvoltage warning light illuminated during operation. Installed new voltage regulator (p/n R1530B), started engine, switched on electrical system and the warning light came on. After troubleshooting with manufacturer’s service department, unit shorted internally, which the manufacturer would not warranty because they said the alternator was at fault. Replaced faulty new regulator with part number listed in parts manual—system works fine. This unit will not work with this system no matter what the manufacturer says.

Part total time: 0.0 hours


Beechcraft Model A100 King Air
Shorted Voltage Regulator

When the aircraft is equipped with VR-1010-24-1A regulators allowed by Service Instruction 0766-354, Rev II, the overvoltage testing procedure is not achievable. The solid-state voltage regulators are not adjustable to a range (over 31.5v) that will adequately test the overvoltage relays. During a ground run and adjustment of the new voltage regulators, one failed and caused an overvoltage condition. It is this technician’s opinion that the test procedure for the overvoltage relay should be changed to include removing and bench testing the overvoltage relays.

Part total time: 0.0 hours

LamarAlternatorController

Cessna Model 402C Utiliner/Businessliner
Failed Voltage Regulator

During cruise, both alternators dropped off line, and a smoke odor was noted in the cockpit. The aircraft diverted and landed safely. Initial corrective action included adjusting installation clearance and removing/replacing left and right voltage regulators. Both actions resulted in satisfactory ground runs but the problem recurred after several minutes of flight. After further inspection involving removal of floor panels, wall panels, engine cowlings and stub wing panels, an alternator field fuse was found loose in its housing. After correction, aircraft checked good and was released for a satisfactory functional check flight.

Part total time: Unknown


Piper PA-31-350 Navajo Chieftain
Shorted Voltage Regulator

On climbout, the left ammeter went to zero and the right alternator light illuminated. The pilot reset and the right ammeter went to 70 amps and failed. Then the left alternator light illuminated as both alternators went offline. The pilot reset the right alternator, which remained online, while the left alternator would not reset. The pilot declared an emergency, returned to the departure airport and landed without further incident. Troubleshooting determined the left voltage regulator was the source of the fault. Replaced the left voltage regulator (p/n B-00286-1) and adjusted unit voltage paralleled to right voltage regulator. Aircraft returned to service.

Part total time: Unknown