Service difficulty report · Starter Gen · Bell 407

Difficulty date
August 12, 2020
Submitted
September 10, 2020
Operation
Air carrier
Aircraft
N925MD
Make and model
Bell 407
Aircraft serial
53477
Aircraft time
5,289 hours, 10,440 cycles
Engine
Allsn 250C47B
Engine time
5,176 hours, 7,124 cycles
Part
Starter Gen
Part number
23081018
Part serial
97421
Condition
Arced
Location
Engine
Stage of operation
IN
How discovered
V
Nature of condition
O
Precautionary procedure
K

As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.

What was found

DURING SCHEDULED INSPECTION OF STARTER/GENERATOR, WE FOUND A MOLTEN HOLE IN THE FAN COVER AT THE REAR OF THE GENERATOR. UPON REMOVING THE COVER, WE FOUND ONE OF THE BRUSH LEADS HAD SHORTED TO THE CASE, DAMAGING THE CASE AND THE LEAD. IT WAS ALSO NOTICED THAT ADJACENT TO SOME BRUSH LEADS THERE WAS AN ANTI-CHAFE/INSULATING TAPE APPLIED TO THE COVER, BUT NOT AT THIS LOCATION. THERE WAS NO INSULATION ON ANY OF THE BRUSH LEADS. WHEN WE INSPECTED TWO OTHER GENERATORS, WE FOUND NO INSULATION TAPE, BUT ALL OF THE BRUSH LEADS WERE INSULATED WITH A "SNAKE SKIN". WE CONTACTED PRECISION HELIPARTS LOUISIANA, WHO HAD DONE THE LAST OVERHAUL. THEY TOLD US THERE HAD BEEN A HISTORY OF THE THESE GENERATORS HAVING THE INSULATING TAPE COME LOOSE FROM THE COVER AND INGESTING IT, LEAVING THE BRUSH LEAD UNPROTECTED AND THERE WAS A NEW LEAD AVAILABLE THAT WAS INSULATED AND DIDN'T NEED THE INSULATING TAPE.

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