it keeps the mechanism operating smoothly, and changing the grease will help eliminate contaminants that can
cause corrosion. However, it must be done according to
the manufacturer’s exact instructions and only with the
Always leave constant-speed propellers in a horizontal
or, in the case of three blades, in a “Y” position to avoid
water from collecting on the hub. Regular oil changes are
also very important in aircraft with constant-speed props.
Since engine oil provides the power source for controlling propeller pitch, ensuring that the oil is clean will
reduce the chance that the propeller and governor will
have problems caused by sludge or water contamination.
Wood propellers are truly works of art and should be
treated as such. They should be inspected regularly for
damage and delamination. Pay particular attention to
the metal tips, looking for loose screws, rivets, or solder.
The varnish coating serves a critical role in protecting the
propeller from moisture damage and should be carefully
maintained. If the propeller is removed for any reason,
the bolt holes and hub bore should be inspected for elongation and damage. Then, the holes should be treated
with a moisture preventive such as asphalt varnish.
The compressible nature of wood requires that the
torque on the propeller bolts be checked regularly. If
moisture enters the wood, it can swell and then become
loose after drying out. Typically, propeller torque should
be checked 25 hours after installation and every 50
Finally, regardless of the type of propeller that you
have, perform a propeller tracking check. This is a fairly
simple procedure that any owner can do. Begin by
removing one spark plug from each cylinder so that the
propeller can be easily rotated. Next, rotate one of the
blades so that it’s pointing down and place a wooden
The technician uses a highly accurate protractor to measure the blade
angle at each station.
block under the blade tip, marking the exact spot that
the tip passes over on the block. Finally, rotate the propeller, checking the other blades to ensure that the track
is within 1/16 inch of the mark. Any variation beyond
1/16 inch is cause for concern. It may be caused by a bent
blade and should be inspected and repaired by a propeller
Aircraft owners often follow the advice of their wallets
when it comes to preventive maintenance. This is especially true with regard to the manufacturer’s overhaul
recommendations for propellers.
Many owners of fixed-pitch propellers are unaware that
a TBO exists at all for their props. McCauley recommends
that its fixed-pitch propellers be overhauled every seven
Every propeller station has a proper width, thickness, and angle.