Airframe Or Engine Modifications - Hartzell HC-E3YR-7 Owner's Manual

3. Airframe or Engine Modifications
A. Propellers are approved vibrationwise on airframe and
engine combinations based on tests or analysis of similar
installations. This data has demonstrated that propeller stress
levels are affected by airframe configuration, airspeed, weight,
power, engine configuration and approved flight maneuvers.
Aircraft modifications that can effect propeller stress include,
but are not limited to: aerodynamic changes ahead of or
behind the propeller, realignment of the thrust axis, increasing
or decreasing airspeed limits, increasing or decreasing weight
limits (less significant on piston engines), the addition of
approved flight maneuvers (utility and aerobatic).
B. Engine modifications can also affect the propeller. The two
primary categories of engine modifications are those that
affect structure and those that affect power. An example
of a structural engine modification is the alteration of the
crankshaft or damper of a piston engine. Any change to
the weight, stiffness or tuning of rotating components could
result in a potentially dangerous resonant condition that is not
detectable by the pilot. Most common engine modifications
affect the power during some phase of operation. Some
modifications increase the maximum power output, while
others improve the power available during hot and high
operation (flat rating) or at off-peak conditions. Examples
of such engine modifications include, but are not limited to:
changes to the compressor, power turbine or hot section of
a turboprop engine; and on piston engines, the addition or
alteration of a turbocharger or turbonormalizer, increased
compression ratio, increased rpm, altered ignition timing,
electronic ignition, full authority digital electronic controls
(FADEC), or tuned induction or exhaust.
C. All such modifications must be reviewed and approved by
the propeller manufacturer before obtaining approval on the
aircraft.
Propeller Owner's Manual
INTRODUCTION
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Rev. 2 Feb/17