TM 55-1510-219-MTF
F12.
Both arm lights extinguish when one power lever is
retarded (engine torque 9 to 14 percent on retarded
engine, AUTOFEATHER ARM-TEST switch in TEST
position).
a.
Defective No. 2 (6.5 PSI) torque pressure switch on
retarded engine.
F13.
One arm light remains illuminated after torque of one
engine falls below 9-14 percent of the retarded engine,
AUTOFEATHER ARM-TEST switch in TEST position).
a.
Defective No. 2 (6.5 PSI) torque pressure switch on
retarded engine.
b.
Defective autofeather dump valve.
F14.
Propeller slow to feather or unfeather.
a.
Preformed packing leak at transfer tube or transfer
housing.
b.
Defective propeller governor.
c.
Malfunction or incorrect rigging of control linkage.
d.
High block friction or excessive friction in pitch changing
mechanism.
F15.
Propeller fails to unfeather.
a.
Malfunction or incorrect rigging of control linkage.
b.
Defective governor.
c.
Excessive leakage at engine transfer bearing.
d.
High blade turning friction or excessive friction in pitch
changing mechanism.
F16.
Propeller goes to high pitch or feather uncommanded.
a.
Lack of oil pressure to propeller.
b.
Beta valve malfunction (only during ground operation).
F17.
Propeller goes to full low pitch (high R PM).
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