Propeller Owner's Manual
115N
INTRODUCTION
61-00-15
Page 1-6
Rev. 24 Dec/20
2.
Airframe or Engine Modifications
(Rev. 1)
A. Propeller Stress Levels
(1) 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
(1)
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.
(a) Examples of turbine
engine modifications include,
but are not limited to: changes to the compressor,
power turbine or hot section of a turboprop engine.
(b) Examples of reciprocating engine modifications
include, but are not limited to: 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.
