Propeller Owner’s Manual
139
MESSAGE
61-00-39
Page 3
Rev. 17 Apr/20
For operators of uncertified or experimental aircraft an
even greater level of vigilance is required in the
maintenance and inspection of the propeller. Experimental
installations often use propeller-engine combinations that
have not been tested and approved. In these cases, the
stress on the propeller and, therefore, its safety margin
is unknown. Failure could be as severe as loss of a
propeller or propeller blades and cause loss of propeller
control and/or loss of aircraft control.
Hartzell Propeller Inc. follows FAA regulations
for propeller
certification on certificated aircraft. Experimental aircraft
may operate with unapproved engines or propellers or
engine modifications to increase horsepower, such as
unapproved crankshaft damper configurations or high
compression pistons. These issues affect the vibration
output of the engine and the stress levels on the propeller.
Significant propeller life reduction and failure are real
possibilities.
Frequent inspections are strongly recommended if
operating with a non-certificated installation; however,
these inspections may not guarantee propeller reliability,
as a failing device may be hidden from the view of the
inspector. Propeller overhaul is strongly recommended to
accomplish periodic internal inspection.
Visually examine metal blades for cracks. Inspect hubs,
with particular emphasis on each blade arm for cracks.
Eddy current equipment is recommended for hub
inspection, since cracks are usually not apparent.
