Service difficulty report · Stud · Dhav DHC8311

Difficulty date
October 30, 1995
Submitted
March 26, 2000
Operation
General aviation
Make and model
Dhav DHC8311
Part
Stud
Part number
7442833
Condition
Sheared
Location
Valve To Motor
Component
Hamstd · 7786863
Stage of operation
IN
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

(CAN)ONE OF TWO STUDS WHICH ATTACH SHUTOFF VALVE BODY TO THE VALVE MOTOR WAS FOUND SHEARED. FRACTURE OF STUD WAS JUST WHERE IT ENTERED CASTING OF MOTOR BODY. FOLLOW-UP INFO INDICATED THAT FAILED STUDS WERE EMBRITTLED, ONE STUD WAS TOO HARD AS PER MATERIAL HARDNESS. IN ADDITION, STUDS TO BE REPLACED WITH NAS1860CA12 WHICH IS NOT SUSEPTIBLE TO HYDROGEN EMBRITTLEMENT AND CAN BE USED TO REPAIR HOUSINGS WHICH HAVE DAMAGED THREADS AS WELL AS A REPLACEMENT. IN ADDITION, CURRENT GASKET WILL BE REPLACED WITH SHIM.