Propeller Owner’s Manual
139
MAINTENANCE PRACTICES
61-00-39
Page 6-28
Rev. 17 Apr/20
10. Propeller Ice Protection Systems
(Rev. 1)
A. Maintenance Information
(1) Refer to the Anti-ice and De-ice Systems chapter of
this manual for ice protection system maintenance
information.
11. Tachometer Calibration
(Rev. 1)
WARNING:
OPERATION WITH AN INACCURATE
TACHOMETER CAN CAUSE RESTRICTED
RPM OPERATION AND DAMAGING HIGH
STRESSES. PROPELLER LIFE WILL
BE SHORTENED AND COULD CAUSE
CATASTROPHIC FAILURE.
A. Important Information
(1) All engine/propeller combinations have operating
conditions at which the propeller blade stresses begin to
reach design limits.
(a) In most cases, these conditions occur above the
maximum rated RPM of the engine.
(b) Some engine/propeller combinations have certain
ranges of RPM that are less than maximum engine
speed, where stresses are at a level considered
too high for continuous operation. This results in
a restricted operating range where continuous
operation is not permitted. A placard on the
instrument panel or yellow arc on the tachometer will
inform the pilot to avoid operation in this range.
(c) In other cases, the limiting condition occurs at an
RPM only slightly above the maximum engine RPM.
(d) For these reasons, it is very important to accurately
monitor engine speed.
