Service difficulty report · Lock Nut

Difficulty date
September 30, 2026
Submitted
September 30, 2026
Operation
General aviation
Aircraft
N735CB
Engine
Allsn 250C20B
Engine time
8,822 hours, 11,668 cycles
Part
Lock Nut
Part number
MS21043
Condition
Failed
Location
Engine
Stage of operation
IN
How discovered
V
Nature of condition
Z
Precautionary procedure
K

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

What was found

MS21043 NUTS ARE UTILIZED TO SECURE TURBINE, COMPRESSOR, FUEL CONTROL, GOVERNOR, AND HAVE BEEN FOUND NUMEROUS TIMES TO HAVE NOT MAINTAINED THE MANUAL SPECIFIED TORQUE AND HAVE BACKED OFF. NUMEROUS TIMES NUTS HAVE ARRIVED WITHOUT ANY DRAG TORQUE. THE LOCKING FEATURE OF THE NUT IS FAILING. MANUFACTURER IS MONROE AEROSPACE AND LOT NUMBERS ARE NOT CONSISTENT AS THOUGH IT WAS A BAD LOT.