TM 55-1510-220-MTF
F12.
Both arm lights extinguish when one power lever is retarded (engine torque 9 to 14 percent on
retarded engine, AUTOFEATHER ARM-TESTI' 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 RPM).
3-26
